United States
Environmental Protection
Agency
Industrial Environmental Research EPA-600/2-80-042b
Laboratory March 1980
Research Triangle Park NC 27711
Research and Development
Source Assessment:
Residential
Combustion of Wood
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously
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The nine series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7. Interagency Energy-Environment Research and Development
8. "Special" Reports
9. Miscellaneous Reports
This report has been assigned to the ENVIRONMENTAL PROTECTION TECH-
NOLOGY series. This series describes research performed to develop and dem-
onstrate instrumentation, equipment, and methodology to repair or prevent en-
vironmental degradation from point and non-point sources of pollution. This work
provides the new or improved technology required for the control and treatment
of pollution sources to meet environmental quality standards.
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This document is available to the public through the National Technical Informa-
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EPA-600/2-80-042b
March 1980
Source Assessment:
Residential Combustion
of Wood
by
D.G. DeAngelis, D.S. Puffin, J.A. Peters, and R.B. Reznik
*
Monsanto Research Corporation
1515 Nicholas Road
Dayton, Ohio 45418
Contract No. 68-02-1874
Task No. 23
Program Element No. 1AB015
EPA Project Officer: John 0. Milliken
Industrial Environmental Research Laboratory
Office of Environmental Engineering and Technology
Research Triangle Park, NC 27711
Prepared for
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Research and Development
Washington, DC 20460
KS) &m&\ I)e«rom Street;
6G604
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PREFACE
The Industrial Environmental Research Laboratory (IERL) of the
U.S. Environmental Protection Agency (EPA) has the responsibility
for insuring that pollution control technology is available for
stationary sources to meet the requirements of the Clean Air Act,
the Federal Water Pollution Control Act, and solid waste legisla-
tion. If control technology is unavailable, inadequate, or
uneconomical, financial support is provided for the development
of the needed control techniques for industrial and extractive
process industries. All types of techniques are considered:
process modifications,,feedstock modifications, add-on control
devices, and complete process substitution. The scale of the
control technology programs ranges from bench studies to full-
scale demonstration plants.
To support the control technology development program, IERL also
conducts extensive environmental assessment programs for the
purpose of identifying and" prioritizing those sources of pollu-
tion in need of control. This is a determination which should
not be made on superficial information; consequently, each major
source category is being evaluated in detail to determine if
there is, in EPA's judgment, sufficient need for emission reduc-
tion. This report contains data that will be useful in making
a more objective decision with respect to the air emissions from
the residential combustion of wood.
Monsanto Research Corporation has contracted with EPA to investi-
gate the environmental impact of various source categories which
represent sources of pollution in accordance with EPA's respon-
sibility as outlined above. Dr. Robert C. Binning serves as
Program Manager in this overall program, entitled "Source Assess-
ment," which includes the investigation of sources in each of
four categories: combustion, organic materials, inorganic mate-
rials, and open sources. Dr. Dale A. Denny of the Industrial
Processes Division at Research Triangle Park serves as EPA
Project Officer. In this study of the residential combustion
of wood, Dr. Ronald A. Venezia of the Chemical Processes Branch,
Warren Peters of the Process Technology Branch, and John O.
Milliken of the Special Studies Branch served as EPA Task
Officers.
111
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ABSTRACT
The potential environmental impact from the residential combus-
tion of wood has been estimated. An estimated 16.6 million
metric tons of wood were burned in the residential sector in
1976. ABout 30% of this was burned for primary heating in an
estimated 912,000 housing units. Georgraphic distribution of
wood-fired heating devices is related to the natural forest
regions in the United States. By 1985 it is estimated that
over 10 million homes will be using some wood fuel.
Emissions from wood-fired residential heating devices include
particulate matter, sulfur oxides, nitrogen oxides, carbon mon-
oxide, hydrocarbons, and polycyclic organic matter (POM). The
estimated impact of these emissions has been assessed by the
method of source severities. This method involves estimating
maximum ground level concentrations of pollutants from an average
source and comparing these concentrations to a National Ambient
Air Quality Standard for criteria pollutants or to a reduced
threshold limit value for noncriteria pollutants. Source sever-
ities were found to be highest for POM emissions. The potential
impact of this source was also evaluated by calculating total
state and national emissions. Particulates, hydrocarbons, and
carbon monoxide emissions from all residential wood-fired sources
were estimated to contribute 1.0%, 1.5% and 3.8%, respectively,
of the total national emission burden for those species in 1976.
In addition, this source was determined to.be a major national
source of POM emissions.
This report was submitted in/partial fullfillment of Contract No.
68-02-1874 by Monsanto Research Corporation under the sponsorship
of the U.S. Environmental Protection Agency. The study described
in the report covers the period November 1976 to February 1980.
IV
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CONTENTS
Preface iii
Abstract iv
Figures vi
Tables vii
1. Introduction 1
2. Summary 2
3. Source Description 6
Source definition . 7
Equipment description and operation , 8
Fuel characteristics 14
Combustion process 16
Source population and geographical
distribution 21
4. Emissions 26
Selected pollutants 26
Emissions data 27
Potential environmental effects 35
5. Control Technology 48
6. Growth and Nature of the Source 49
Present technology 49
Industry trends 52
References 60
Appendices
A. Estimation of the source population and fuel
consumption 67
B. Determination of the representative source 73
C. Derivation of emission factors 77
D. Total wood-fired residential combustion emissions. . 83
Glossary 88
Conversion Factors and Metric Prefixes 90
v
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FIGURES
Number Page
1 Typical masonry wood-burning fireplace 9
2 Wood-fired forced air furnace 13
3 Combustion of a solid 18
4 Overfeed arrangement of a solid fuel bed 20
5 The natural forest regions of the United States . . 22
6 Estimated residential wood consumption by state
in 1976 22
7 Residential wood-firing heating trends 53
8 United States production of wood burning stoves . . 56
9 New housing completed, 1971-1976 57
VI
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TABLES
Number Pa9e
1 Criteria Emissions from Wood-Fired Residential
Heating Equipment 3
2 Noncriteria Emissions from Wood-Fired Residential
Combustion 3
3 Housing Units Heated by a Particular Fuel in 1976 . 7
4 Composition and Fuel Properties of Typical Grades
of Dry Wood 17
5 Composition of Ash from Typical Grades of Wood. . . 18
6 Elemental Composition of Wood 18
7 Estimated Population of Wood-Fired Residential
Combustion Equipment and Wood Consumed by the
Residential Sector, 1976 24
8 Average Emission Factors for Wood-Fired Residential
Combustion 28
9 Major Organic Species and POM Compounds Detected
in Emissions from Wood-Fired Residential
Combustion Equipment 34
10 Elemental Emissions from a Nonbaffled Woodburning
Stove ' 35
11 Results of Bioassays Performed on SASS and
Combustion Residue Samples 37
12 Definition of Range of EC5o Values 38
13 Source Severity for Average Wood-Fired
Residential Combustion Units 41
14 Affected Population for Wood-Fired Residential
Combustion 43
15 State Listing of Residential Wood Criteria
Emissions That Exceed 1% of Total State
Criteria Emissions 44
16 Estimated Annual Criteria Emissions and National
Emission Burden from Wood-Fired Residential
Combustion for 1976 45
VII
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TABLES (continued)
Number
Page
17 Total Annual Emissions from Residential
Combustion Sources 45
18 Listing of Source Types That Emit POM's in
Quantities Greater Than 1 Metric Ton/Year 46
19 Combustion Control Strategies for Reducing Air
Pollutants from Residential Heating Equipment. ... 48
20 Structures Built with Primary Wood Heating 53
21 Housing Units with Primary Wood Heat by Region,
1970 54
22 Regional Distribution of Housing Units with
Primary Wood Heat, 1976 54
23 Percent Distribution of Fireplaces in New Housing
by Sales Price in 1976 57
24 States Which Depend Highly on Fuel and or
Electricity as Primary Heat 59
A-l Number of Housing Units Burning Wood for Primary
Heating, 1970 and 1976 67
A-2 Number of Housing Units Burning Wood for Primary
Heating by State, 1970 and 1976 69
A-3 Estimated Annual Heating Degree-days and Wood
Consumption for Primary Heating by State, 1976 . . . 70
A-4 Estimated Wood Consumption in Fireplaces and in
Auxiliary Heating by Wood Stoves by State, 1976. . . 71
B-l Distribution by Region of Households which Heat
Primarily with Wood 73
B-2 Distribution within Regions of Households which
Heat Primarily with Wood, 1976 73
B-3 TVA Wood for Energy Heating Demonstration -
January 1978 Data 75
B-4 TVA Wood for Energy Heating Demonstration -
February 1978 Data 76
C-l Emissions Data for Wood Combustion, Stable
Conditions 78
C-2 Emissions Data for Wood Combustion 78
C-3 Particulate Emissions Data for Wood Consumption. ... 79
Vlll
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TABLES (continued)
Number gage
C-4 Emissions Data for Wood Combustion, Stable
Conditions 79
C-5 Emissions Data for Wood Combustion 80
C-6 Particulate Emissions Data for Wood Combustion. ... 81
D-l Percentage of Total State Criteria Emissions due
to Primary Residential Heating with Wood 84
D-2 Percentage of Total State Criteria Emissions due
to Auxiliary Residential Heating with Wood 85
D-3 Percentage of Total State Criteria Emissions due
to Residential Wood Burning in Fireplaces 86
D-4 NEDS Emission Summary by State 87
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SECTION 1
INTRODUCTION
Residential combustion of wood for space heating has found
renewed interest in this country due to the rising cost of oil
and natural gas and their uncertain future availability. Exist-
ing knowledge of the emissions from wood combustion indicate that
this trend poses a potential environmental problem. It is gener-
ally assumed that residential combustion of wood produces signi-
ficant emissions because of the high level of smoke produced.
No major effort has been made in the past to reduce these emis-
sions, however, design changes to improve combustion efficiency
may have also reduced smoke and emission levels.
By 1960 residential combustion of wood for home heating had almost
been eliminated. This decline is now being reversed, and it is
uncertain how rapidly this form of residential heating will grow.
It is also unclear what environmental problems would be created
by large scale residential combustion of wood. For example, it
is suspected that long term exposure to relatively low concentra-
tions of certain organic compounds (e.g., polycyclic organic
matter) can have serious health effects. Some of these compounds
are known to be emitted by wood combustion sources.
This report presents a review of characterization data for emis-
sions from residential wood combustion and an evaluation of their
potential environmental effects. It describes several types of
residential wood combustion equipment, the 1976 geographic dis-
tribution of wood-fired equipment, fuel characteristics, and
combustion chemistry. Primary and secondary wood heating, as
well as wood burning for aesthetic purposes, are all covered in
the report. Emission control technology and possible future
trends of the source are also discussed.
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SECTION 2
SUMMARY
This report assesses the environmental impact of air emissions
produced by the residential combustion of wood. It encompasses
wood burned for primary home heating, wood burned for auxiliary
home heating and wood burned in fireplaces for aesthetic purposes.
Residential consumption of wood for primary heating in 1976 was
estimated to be 5,122,000 metric tons, burned in 912,000 housing
units. The large wood-producing areas in the West and South have
the highest number of homes heated by wood. On the basis of 1976
data the six-state region of Alabama, Georgia, North Carolina,
South Carolina, Tennessee and Virginia contains about 39% of the
nation's total wood-fired primary heating devices, and accounts
for 32% of the wood burned for that purpose. Large quantities of
wood are also burned in homes either for auxiliary heat or for
aesthetic purposes. It is estimated that wood burned for these
purposes is greater than that burned for primary heating. In
1976 an estimated 28,000,000 fireplaces and 7,600,000 auxiliary
wood stoves burned 2,700,000 metric tons and 8,800,000 metric
tons of wood, respectively, per year. Fireplaces are more pre-
dominant in the Northeast and West regions of the country, while
auxiliary wood heating is more prevalent in the South and North-
east regions.
Residential combustion of wood produces emissions of particulate
matter, sulfur oxides (SOX)/ nitrogen oxides (NOx), hydrocarbons,
carbon monoxide (CO), and a wide variety of organic compounds
including polycyclic organic matter (POM). Uncontrolled mass
emissions and emission factors are listed in Tables 1 and 2. Also
presented is the contribution of wood-fired residential combustion
to the national level of criteria emissions (i.e., particulate
matter, SOX, NOx, CO, and hydrocarbons). All criteria emissions
from residential wood combustion except SOx and NOx exceed 1% of
the national level of criteria pollutant emissions. On a state
basis, criteria emisssions from residential wood combustion
exceed 1% of the state total of at least one criteria pollutant
in 49 states.
Emission factors for hydrocarbons, CO, and POM are higher than
those for most other combustion sources and reflect the imperfect
combustion conditions typical of residential wood burning. The
composition of the particulate emissions (50% to 80% carbon) also
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TABLE 1. CRITERIA EMISSIONS FROM WOOD-FIRED RESIDENTIAL HEATING EQUIPMENT
, . a
g/kg
Emission
species
Particulate
SOX
NOX
Hydrocarbons
CO
Wood
stove
9.1
0.2
0.49
13
180
Fire-
place
13
0.2C
2.0
74
67
Source
Wood
stove
0.02
<0.001
0.004
0.063
0.004
severity
Fire-
place
0.08
<0.001
0.05
1.0
0.005
Affected population0
X> >
Wood
stove
0
0
0
0
0
: 1.0
Fire-
place
0
0
0
0
0
X/F >
Wood
stove
0
0
0
0
0
0.05
Fire-
place
1
0
0
10
0
.
emissions from
all stationary
sources
1.0
<0.01
0.05
1.5
3.3
Based on kg wood burned, as received.
Based on an average population density of 21 personsAm2.
"Based on data from wood stoves.
TABLE 2. NONCRITERIA EMISSIONS FROM WOOD-FIRED RESIDENTIAL COMBUSTION
Emission factor,
Emission
speciesc
Condensable organics
POM
Formaldehyde
Total carbonyls
Phenol
Wood
stove
•5.5
0.27
0.23
gAg
Fire-
place
10
0.029
1.5
4.4
1.0
Source
Wood
stove
d
46
0.013
severity
Fire-
place
d
14
0.23
d
0.03
Affected population0
X/F >.
Wood
stove
d
32
0
1.0
Fire-
place
d
9
0
d
0
X/F >
Wood
stove
d
730
0
0.05
Fire-
place
d
210
3
d
0
Note: Blanks indicate no data available.
on kg wood burned, as received.
Based on an average population density of 21 persons/km2.
COnly major species are listed. An extensive listing of other organic species is given
in Section 4.
dThese species are evaluated for source severity and affected population under the
criteria pollutant categories of particulates and hydrocarbons.
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shows the incomplete nature of the combustion process. It is
estimated that total national POM emissions from this source
represent approximately 80% of total national POM emissions from
all sources (excluding natural and mobile sources).
The extent of potential environmental and health effects was
addressed in this study on the basis of bioassay testing of com-
bustion emissions and by means of certain evaluation criteria
established under the Source Assessment program. Bioassay tests
on^a series of stack samples collected from three wood-burning
units firing different types of wood showed that solvent extracts
°f all the samples were mutagenic (Ames test) and cytotoxic (CHO
cytotoxicity test).
Potential environmental impact was also evaluated by determining
the parameters of source severity and affected population. Be-
cause the parameters are based on average source parameters and
employ certain assumptions and approximations, they are not in-
tended to provide an absolute measure of environmental impact.
Rather, they are to be used in conjunction with other studies
to set priorities for sources where emissions reduction may be
required. For assessment purposes an average wood stove was
assumed to burn wood at the rate of 3.0 kg/hr during a 24-hr
period of the heating season. An average fireplace burns wood
at the rate of 8.5 kg/hr. It is assumed that both units have
chimneys 5.2 m high and are located in areas with a population
density of 21 persons/km2.
Source severity is defined as the ratio of the time-averaged maxi-
mum gound level concentrations (Xmax) of £pecies emitted from the
source to a hazard factor (F), i.e., S = Xmax/F. For criteria
emissions, F is the primary ambient air quality standard (PAAQS),
while for noncriteria emissions, it is a reduced threshold limit
value (TLV®/300). Tables 1 and 2 give the severities for the
average wood-burning sources.
Severities for individual residential sources may differ greatly
from the values given in Tables 1 and 2 because of the variabil-
ity found in the population. Those parameters that significantly
affect severity include emission factors9, wood consumption
rates3, duration of burning3, stack heights, and wind speeds.
In addition, the hazard factors for noncriteria pollutants and
the equations used to calculate Xmax contain a number of assump-
tions. An in-depth study of all these factors would be necessary
to define the actual dimensions of the potential environmental
impact. However, these results together with the bioassay results
do indicate that there is reason for concern, especially when the
possible effects of multiple sources are considered.
These factors depend in turn on the type of combustion equipment,
the type and condition of wood, and the method of burning.
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Another measure of potential environmental effect is the affected
population, defined as the number of persons around an average
source who are exposed to a specified average ground level con-
centration (x)-_ These values are given in Tables 1 and 2 for
X/F > 0.05 and x/F ^1-0. The largest value_is for POM emissions
from wood stoves, and equals 32 persons for x/F ^1-0 and 732
persons for x/F > 0.05. Again, these numbers would increase if
multiple sources were considered.
Emissions from residential combustion systems are not typically
controlled with add-on equipment; however, proper operation of
each unit can significantly reduce emissions. Factors influenc-
ing emission levels include fuel properties, fuel type, firing
rate, firing equipment design, cyclic operation of automatic
equipment, and excess air ratio.
Residential combustion of wood for primary heating had shown a
steady decline since the 1940's. Even from 1970 to 1974, wood
combustion for primary heating decreased about 25%. However,
interest in this form of heating has revived since 1974. U.S.
Bureau of Census data up to 1976 indicate that primary residential
heating with wood increased from 1974 to 1976, with the Northeast
and West experiencing the greatest increase. Shipments of wood-
fired heating equipment decreased until 1973, when the trend
reversed. From 1962 to 1972, sales decreased by about 60%; but
from 1972 to 1975 sales increased by 130%. Increased sales have
been in the area of domestic heating stoves. Primary heating
devices such as stoker furnaces began to show an increase in
sales in 1976.
It is difficult to predict the impact the current shortage of oil
and natural gas will have on the volume of wood combustion in the
residential sector. The resurgence in residential wood combustion
is expected to continue in the near term as the cost of wood fuel
becomes even more competitive with distillate oil and electric
resistance space heating.
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SECTION 3
SOURCE DESCRIPTION
Only 1% of U.S. housing units with primary heating devices in
1976 burned wood for primary heating. Natural gas, the most
popular heating fuel, was used in about 56% of the housing units
(1). Emissions from the small fraction of housing units burning
wood are major contributors to total national emissions from
residential combustion. For example, a study done in 1973 (2)
estimated that particulate emissions from wood-fired residential
combustion contributed 11% of the total particulate emissions
from all residential sources. By comparison, the analogous
fractions of particulate emissions from coal, petroleum, and gas
residential combustion were estimated to be 30%, 36% and 23%,
respectively (in 1973). Particulate emissions from residential
combustion sources accounted for 0.7% of total national particu-
late emissions from all man-made sources.
Table 3 gives the breakdown of units heated by different fuel
types in 1976 (1). As discussed later in Section 6, the number
of homes heating with wood has been increasing rapidly in recent
years. Another home heating method that is once more gaining in
popularity is residential coal combustion. A separate environ-
mental assessment report on this source type has been published
(3).
01) Current Housing Reports; Bureau of the Census Final Report
H-150-76; Annual Housing Survey: 1976, Part A; General
Housing Characteristics for the United States and Regions.
U.S. Department of Commerce, Washington, D.C., February 1978
179 pp.
(2) Surprenant, N., R. Hall, S. Slater, T. Susa, M. Sussman, and
C. Young. Preliminary Emissions Assessment of Conventional
Stationary Combustion Systems; Volume II - Final Report.
EPA-600/2-76-046b, PB 252 175, U.S. Environmental Protection
Agency, Research Triangle Park, North Carolina, March 1976.
557 pp.
(3) DeAngelis, D. G., and R. B. Reznik. Source Assessment:
Residential Combustion of Coal. EPA-600/2-79-019a, U.S.
Environmental Protection Agency, Research Triangle Park,
North Carolina, January 1979. 143 pp.
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TABLE 3. HOUSING UNITS HEATED BY A PARTICULAR FUEL IN 1976 (1)
- — - - - - — - - - .
Utility gas
Bottled, tanked or
liquefied petroleum gas
Fuel oil, kerosene
Electricity
Coke or coal
Wood
Other .fuels
Total
Rural
6,286,000
3,712,000
5,785,000
3,954,000
311,000
820,000
8,000
20,860,000
Urban
34,932,000
527,000
10,666,000
6,197,000
174,000
92,000
78,000
52,666,000
Total
units
41,219,000
4,239,000
16,451,000
10,151,000
484,000
912,000
86,000
73,542,000
SOURCE DEFINITION
Wood-fired residential combustion sources include all equipment
that burns wood for household heat or aesthetic purposes. These
devices produce up to 530 MJ/hr of heat in occupied structures
containing one or two housing units although under typical oper-
ating conditions, most units produce well under 100 MJ/hr. Wood
burned for primary or auxiliary heating (primarily in wood stoves)
and wood burned aesthetically (primarily in fireplaces) are all
included in the source population.
A negligible amount of wood is burned for cooking and hot water
heating. Discussions with manufacturers have indicated that
very few persons use wood for hot water heating. In 1976 approx-
imately 208,000 housing units, or 23% of the units heating with
wood (1), used wood for cooking. It is estimated that cooking
requires about 10% of the energy used for heating (4, 5). There-
fore, the amount of wood used for cooking is approximately 2% of
that used for heating with those fuels.
Also excluded from this source type are wood-fired devices located
in large multiunit structures since they represent only a small
portion of the total wood combustion for residential heating. In
(4) Patterns of Energy Consumption in the United States. Pre-
pared by Stanford Research Institute for Office of Science
and Technology, Executive Office of the President,
Washington, D.C., January 1972. 221 pp.
(5) Wells, R. M., and W. E. Corbett. Electrical Energy as an
Alternate to Clean Fuels for Stationary Sources: Volume I.
Contract 68-02-1319, Task 13, U.S. Environmental Protection
Agency, Research Triangle Park, North Carolina, March 1976.
181 pp.
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1970, approximately 99% of all housing units heated by wood were
located in structures having fewer than 3 housing units (6).
EQUIPMENT DESCRIPTION AND OPERATION
A wide variety of wood-fired combustion equipment is available
for residential usage. The most popular devices are masonry or
prefabricated metal fireplaces, and radiating or circulating metal
stoves. Larger forced air furnaces and boilers are also used in
the United States, but to a much lesser extent (7, 8).
Fireplaces and stoves operate in essentially the same manner.
Wood is manually placed on a metal grate in the unit and ignited.
A natural draft of room air passes over the wood and escapes up
the chimney, providing combustion air to maintain the fire.
Energy released by the fire heats the room by radiation, conduc-
tion, and convection. Ash removal is also performed manually.
Residential wood-fired furnaces and boilers operate in a similar
fashion where combustion air may be provided by blowers or natural
draft.
Despite these similarities, there are substantial differences
between the various types of residential combustion units. These
differences are primarily related to equipment configuration and
combustion efficiency, as described in the following subsections.
Fireplaces
A typical wood-burning, masonry fireplace is shown in Figure 1.
These devices are commonly used for secondary heating and aes-
thetic purposes, but rarely for primary heating due to their
poor thermal efficiencies. Regular masonry fireplaces have effi-
ciencies of no greater than 10% in cold weather (7). When used
in conjunction with another form of heating, they can actually
result in an overall loss of heat, because -of the large volume
of heated room air going up the chimney.
The intake air rate of an open fireplace has been measured at
0.04 m3/s to 0.16 m3/s, which is considerably greater than the
air intake rate needed to maintain combustion (8). An average
(6) Census of Housing: 1970 Subject Reports; Bureau of the
Census Final Report HC(7)-4; Structural Characteristics
the Housing INventory. U.S. Department of Commerce,
Washington, D.C., June 1973. 450 pp.
(7) The Old Wood Stove is in Demand Again. Dayton Journal
Herald, 170(27):19, 1977.
(8) Soderstrom, N. Heating Your Home with Wood. Times Mirror
Magazines, Inc., Harper & Row, New York, New York, 1978.
207 pp.
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,w
CHIMNEY OPENING
FIREPLACE
OPENING
Figure 1. Typical masonry wood-burning fireplace (9).
insulated house with ^270 m3 of living space will normally undergo
a complete exchange with outdoors air approximately every hour.
A fireplace, taking in air at a rate of 0.09 m3/s, causes the air
exchange rate to more than double. Thus, the radiant heating
effect of the fire is partially or wholly negated by increased
infiltration of cold air from outdoors.
The options for minimizing air exchange are limited. The fire-
place opening can be covered with a glass screen or a metal
damper can be placed in the fireplace throat. The first option
minimizes air exchange at the expense of heat loss up the chimney.
The radiant energy transmitted by the fire is partially absorbed
or reflected by the glass screen.
A more practical approach to minimizing air exchange is the
installation of a metal damper in the throat of the fireplace.
A damper controls the intake of room air, reduces the wood con-
sumption rate and eliminates the escape of warm air when there
is no fire. Several other mechanical devices are available on
-------
the market to increase radiant heat yields from fireplaces; how-
ever, these devices do not eliminate the intake of heated room
air (9, 10).
The efficiency of masonry fireplaces can be improved by using
outside air rather than room air for combustion purposes. Unfor-
tunately, most fireplaces are not equipped in this fashion (10).
Various types of prefabricated metal fireplaces are available
on the market. These include stovelike fireboxes designed for
installation in existing masonry fireplaces, "zero clearance"3
fireplaces which physically resemble their masonry counterparts,
and free standing fireplaces (8).
Prefabricated fireboxes are normally equipped with glass doors
and louvers to regulate the intake of combustion air from the
room. In addition, these units are surrounded by a duct through
which floor-level air is drawn by natural convection, heated, and
returned to the room. Although the glass doors reduce radiant
heat transfer from the fire, prefabricated fireboxes tend to be
more efficient than open masonry fireplaces due to the reduction
in room air losses up the chimney and the return of heated con-
vection air to the room.
Zero-clearance fireplaces consist of a heavy-gauge steel firebox
lined with firebrick on the inside and surrounded by multiple
steel walls spaced for air circulation. In operating principle,
they are very similar to the prefabricated metal fireboxes de-
scribed above. Some models are also equipped with combustion air
inlets that draw cool air from other rooms or from outdoors to
avoid the loss of heated air up the chimney. In general, zero-
clearance fireplaces are somewhat more efficient than open
masonry fireplaces.
The most common freestanding fireplace models consist of an in-
verted sheet-metal funnel and stovepipe directly above the fire- -
bed and grate. However, units such as the Ben Franklin stove
may also be considered freestanding fireplaces when operated with
Zero-clearance fireplaces are so-named because the insulative
value of the walls and bottom allow placement directly adjacent
to combustible walls or floors.
(9) Snowden, W. D. , D. A. Alguard, G. A. Swan son, and
W. E. Stolberg. Source Sampling Residential Fireplaces
for Emission Factor Development. EPA-450/3-76-010, U.S.
Environmental Proteciton Agency, Research Triangle Park,
North Carolina, November 1975. 173 pp.
(10) Manufacturers Brochure. Bolap, Inc., of Colorado, Fort
Collins, Colorado.
10
-------
the doors open. Like masonry fireplaces, these units are inher-
ently inefficient due to the large volumes of heated room air
drawn up the chimney. Freestanding fireplaces may be slightly
more efficient than masonry fireplaces, however, since all sides
of the fire chamber are exposed to the room.
Stoves
The wood-burning stove is a freestanding, cast iron or sheet
steel unit similar to a metal fireplace. The major difference
is that stoves are equipped with doors through which wood is
loaded into the firebox. During operation, these doors are
closed and the combustion air intake rate is controlled by
movable air inlets. In comparison to the 0.04 m3/s to 0.16 m3/s
air intake rates for fireplaces, stoves normally draw only
0.01 m3/s to 0.05 m3/s (8). Thus, stoves are inherently more
efficient than fireplaces due to the reduction in heated room air
losses.
Two basic types of stoves are available on the market: radiating
stoves, such as the Ben Franklin model, and circulatory stoves
(8). A radiating stove consists of a single cast iron or heavy-
gauge sheet steel shell lined with firebrick which serves as the
firebox and heat radiator. Most radiating stoves are also
equipped with burners for cooking. In general, a maximum thermal
efficiency of approximately 60% is attainable with radiating
stoves.
Circulating stoves consist of an inner firebox enclosed by a
decorative steel jacket (resembling an oil space heater) which
absorbs radiant energy from the walls of the fire chamber and
releases heat to air circulating both inside and outside the
jacket. Air flow through the annulus may be provided by natural
convection or automatic blowers, depending upon the model. Many
circulating stoves are also equipped with thermostats and auto-
matically-controlled dampers to regulate combustion air intake
and thus, heat output. With this regulated combustion air rate,
wood may only need to be charged to the stove every 6 hr to
12 hr, depending on the type of wood burned.
One practical advantage of the circulatory stove over the radia-
ting stove is a reduction in the severity of the burn received
if the stove is accidentally touched. On the negative side,
circulatory stoves are not designed for cooking.
The completeness of combustion and the amount of heat transferred
from a stove, regardless of whether it is a radiating or circula-
tory model, depends heavily upon the air flow pattern through the
unit. The size and number of combustion air inlets and internal
channels that direct flow are the major factors that affect air
flow.
11
-------
The basic combustion air flow patterns are updraft, diagonal and
s-flow. In the updraft air flow type of stove, air enters at the
base of the stove and passes through the wood to the stove pipe
at the top. Secondary air enters above the wood to assist in
igniting unburned volatiles in the combustion gases. This type
air flow usually results in flames reaching the stove pipe, and
the combustion process is fairly complete. However, updraft
stoves provide very little gas-phase residence time, which is
needed for efficient transfer of heat from the gases to the walls
of the stove and stovepipe. Thus, thermal efficiency is limited
to some extent.
Stoves designed for diagonal air flow are equipped with an air
inlet in the front, but do not have an inlet for secondary air.
Air enters at the lower vent and travels diagonally upward
through the wood and out of the stovepipe at the upper back.
It has been suggested that this stove type does not allow hot
volatiles in the combustion gases to mix sufficiently with air
to insure complete combustion. Gas-phase residence times in
dxagonal flow units are also very short, which limits heat
transfer and thermal efficiency in itself.
The s-flow type stove is currently the most popular design in
the United States. This type of stove is equipped with both a
primary and a secondary air inlet like the updraft stove. How-
ever, gases are not allowed to exit directly up the flue because
a metal baffle plate is located several inches above the burning
wood to lengthen the retention time. The baffle plate absorbs a
considerable amount of heat and reflects and radiates much of it
back to the firebox. This longer gas-phase residence time results
in improved combustion when the proper amounts of air are pro-
vided, and enhances heat transfer from the gas phase. Ironically,
the major problem with this type of stove is that the gases are
often cooled below creosote condensing temperatures, creatincr
deposits in the flue. •
Forced-Air Furnaces and Boilers
Larger forced air furnaces and boilers are also being used in the
U.S., although to a much lesser extent than stoves or fireplaces
Figure 2 shows a schematic of a typical forced air furnace (11).'
These units are essentially large circulating stoves, the major
differences relating to heating capacity and heat delivery system
configuration. While stoves are usually intended to heat a single
room or area, furnaces are designed to heat entire houses through
(11) Riteway, The Quality Name in Energy Innovations (manufactur-
ers brochure). Riteway Manufacturing Co., Harrisonburg,
Virginia. 12 pp.
12
-------
o ©
IHIHWAVI
( 1) ASH PIT BLOWER CONTROLLED BY ROOM THERMOSTAT CREATES
FORCED DRAFT IN THE COMBUSTION CHAMBER. AIR ENTERS THROUGH
TWO PORTS ( 3 ) LOCATED ON EITHER SIDEOFTHEGAS COMBUSTION
FLUE ( 5 ).
( 2 t SECONDARY AIR ENTERS HERE, IS PREHEATED AS IT PASSES THROUGH
SPACE UNDER THE FURNACE AND UPWARD THROUGH A SMALL DUCT INTO
THE GAS COMBUSTION FLUE (4 I.
13) AIR PORTS WHICH DIRECT THE aOW OF PRIMARY AIR FROM THE BACK
TOWARD THE FRONT OF THE COMBUSTION CHAMBER.
(4) SECONDARY AIR DUCT.
( 5 ) GAS COMBUSTION FLUE LOCATED COMPLETELY INSIDE COMBUSTION
CHAMBER, INSURING HIGH TEMPERATURE NECESSARY TO BURN THE GASES.
I 6 ) DRAFT INDUCER OPERATES CONSTANTLY TO GUARANTEE SUFFICIENT SEC-
ONDARY AIR UNDER ALL DRAFT CONDITIONS.
I 7 ) RETURN AIR IS PREHEATED AT THE HEAT EXCHANGER BEFORE PASSING
THROUGH THE FILTER AND INTO THE BLOWER, WHICH IN TURN FORCES
IT OVER THE FURNACE BODY.
I 8) OPENING FOR RETURN AIR PLENUM IN TOP OF FAN CHAMBER.
(9) BYPASS AIR RUE IN TOP OF FURNACE.
( 10) OPENING IN TOP OF FURNACE FOR WARM AIR PLENUM.
( 11) BAROMETRIC DAMPER PERMITS A CONTINUAL FLOW OF AIR INTO THE
BYPASS AIR aUE THE DRY WARM AIR IS MIXED WITH RUE GASES
AND HaPS IN PREVENTING THE SMOKEPIPE AND CHIMNEY FROM SWEATING.
I 12 ) DIRECT DRAFT DAMPER LOCATED NEAR TOP OF FUEL DOOR. OPEN ONLY WHEN
ADDING FUEL TO PREVENT SMOKE FROM ESCAPING INTO THE FURNACE ROOM.
I 13 ) OPTIONAL OIL OR GAS BURNER. DAMPER OPERATED BY A SOLENOID ISOLATES
BURNER FROM THE COMBUSTION CHAMBER WHEN BURNER IS NOT IN OPERATION.
IF WOOD FAILS TO MAINTAIN THE DESIRED TEMPERATURE, A ROOM THERMOSTAT
CAN AUTOMATICALLY ENERGIZE THE SOLENOID AND OIL BURNER TO SUPPLY
REQUIRED HEAT UNTIL WOOD SUPPLY IS REPLINISHED.
I 14 ) GRATE BARS
Figure 2. Wood-fired forced air furnace (11). (Wood-fired boiler is similar
in design and operation except furnace jacket is water-filled).
-------
a system of ductwork. Most of these furnaces are thermostatically
controlled and require little attention by the user. The thermo-
stat is set at the desired temperature and wood is supplied as
necessary, or every 2 to 12 hours, depending on the type of wood
burned and the heating requirements. When the furnace is acti-
vated by the thermostat, a damper automatically admits air for
combustion (other units have combustion air fans). When the
demand for heat is satisfied, the damper closes automatically;
however, enough air is passed through the system to keep the
firebed burning slowly. In this type of unit, ash is collected
in an ash pan which must be dumped every week to every 2 weeks.
Return air for the heating system is provided by a blower, which
is activated and deactivated in conjunction with a damper. When
the blower is activated, air is forced over the furnace body
through a system of heat exchangers and into the ductwork system.
Hot water boiler systems currently available on the market are
analogous to forced air furnace systems except that water, rather
than air, is used as the heat transfer medium (12). Hot combus-
tion gases from the firebox pass through firetubes around which
water is circulated. The heated water is then pumped through a
series of baseboard heat exchangers to heat the building.
Wood-fired furnaces and boilers can be used as the sole source of
heating, or they can be used in tandem with conventional heating
systems. In the latter case, the systems are designed so that
the conventional heating source is automatically activated if the
fire in the wood combustor is extinguished.
FUEL CHARACTERISTICS
Hardwoods and softwoods are the two basic types of wood. When
air-dry, most hardwoods weigh over 400 kg/m3 and have a maximum
heating value of 20 MJ/kg. Softwoods weigh less than 400 kg/m3,
air-dry. The most resinous softwoods have a maximum heating
value of 21 MJ/kg. Resins and a higher lignin content account
for this higher heating value (8). Because of their higher
density, hardwoods have a higher heating value than softwoods on
a volume basis.
Although softwoods have a higher heating value, hardwoods are
favored for use as fuel for various reasons. Because the cells
of_softwoods are larger and lighter, they tend to burn faster
which results in more frequent charges and the handling of more
logs in the process. In addition to this disadvantage, the
unburned and partially combusted resins of softwoods tend to
(12) Introducing Tritherm® (manufacturers brochure). Meyer
Company, Glenwood Springs, Colorado. 2 pp.
14
-------
condense in flues and form a creosote that is very difficult to
remove. Softwoods ignite more easily and have an extremely hot
burn. For these reasons, they are used in many cases for kindling
and then hardwoods are added to sustain the burn.
The composition of wood plays an important role in residential
combustion and resulting emissions. Wood composition can vary
from one type to another or within a wood type, depending upon
geographical location.
The materials present in woods include carbohydrates, phenolic
substances (lignin), terpenes, aliphatic acids, alcohols, pro-
teins, and inorganic constituents. Cellulose, a carbohydrate,
and lignin, a phenolic compound, make up more than 90% of wood
substance, with lignin composition ranging from 15% to 30% (13).
Chemically, all hardwoods and all softwoods are similar except
for the resin and lignin content.
The elemental composition of wood, regardless of species, is
approximately 50% carbon, 6% hydrogen, and 44% oxygen on an ash-
and moisture-free basis (14). Sulfur content is often undetect-
able and nitrogen content is typically less than 0.5%. Ash
content of wood is also low, rarely exceeding 5% on a dry weight
basis (15).
Mineral constituents of wood vary greatly between species and
between trees within a species. The most prominent minerals in
wood are calcium, potassium, magnesium, phosphates, and silicates.
Volatile content of wood is high, ranging from 60% to 80% on a
dry weight basis. Because of this, wood has a low ignition tem-
perature and rapid heat release. Heating value of wood ranges
from about 18.1 MJ/kg to about 24.7 MJ/kg on a dry weight basis
(16).
Moisture content of wood burned in residential units can vary
greatly because the wood is stored outdoors exposed to the
weather. Dry wood has a higher heating value than an equal
(13) Koch, P. Utilization of the Southern Pines. Agriculture
Handbook No. 420, U.S. Department of Agriculture Forest
Service, Washington, D.C., August 1972. 1662 pp.
(14) Rieck, H. G., Jr., E. G. Locke, and E. Tower. Charcoal,
Industrial Fuel from Controlled Pyrolysis of Sawmill Wastes,
The Timberman, 46127:49-54, 1944.
(15) Schorger, A. W. Chemistry of Cellulose and Wood. McGraw-
Hill Book Company, New York, New York, 1926. p. 51.
(16) Fernandez, J. H. Why Not Burn Wood? Chemical Engineering,
84(11):159-164, 1977.
15
-------
volume of green wood of the identical type. Approximately 8% of
a hardwood's heating value is lost at 12% moisture content (8).
It is difficult to maintain temperatures high enough to drive
off water and generate the gases necessary for ignition of green
woods. If green woods must be burned, better results are
obtained by burning them in combination with dry woods.
Moisture content can range from 10% to 50% and averages approxi-
mately 20% (17). Tables 4 and 5 list typical analyses of several
woods used for residential combustion (15, 16). An average min-
eral composition of wood is given in Table 6 (15, 18).
COMBUSTION PROCESS
General Description
Because of the varied nature of wood, a precise quantification
of combustion chemistry is difficult to determine. The oxidation
of hydrocarbons to carbon dioxide and water is only part of the
reaction chemistry. Solid fuels contain a variety of chemical
constituents that may participate to some extent in reactions at
high temperatures. Mineral substances such as silicates and
sulfides oxidize in the flame during combustion to form ash that
is either retained in the fuel bed or entrained in the flue gas.
The processes involved in the combustion of wood are illustrated
in Figure 3 (19). Solid fuels burn in diffusion flames because
the solid phase cannot be mixed with oxidants on a molecular
scale. With the addition of radiant energy from an ignition
device or the combustion zone, volatile components are vaporized
and flow away from the solid surface while the solid portion of
the fuel begins to pyrolyze. At this point, no oxidation of the
fuel at the surface occurs due to lack of intimate contact with
the oxidant. A diffusion flame is established where the mixing
of combustibles and oxidant forms a combustable mixture. This
is noted as the primary combustion zone. Additional transfer of
heat results in additional vaporization of volatiles, pyrolysis,
and a rise in surface temperature of the solid. After the deple-
tion of volatiles, oxidation of the solid materials commences.
(17) Panshin, A. J., E. S. Harrar, J. S. Bethel and W. J. Baker.
Forest Products, Their Sources, Production, and Utilization.
McGraw-Hill Book Company, New York, New York, 1953.
(18) Mingle, J. G., and R. W. Boubel. Proximate Fuel Analysis
of Some Western Wood and Bark. Wood Science, l(l);29-36,
1968.
(19) Edwards, J. B. Combustion, Formation, and Emission of Trace
Species. Ann Arbor Science, Ann Arbor, Michigan, 1974.
240 pp.
16
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TABLE 4. COMPOSITION AND FUEL PROPERTIES OF TYPICAL GBADES OF DRY WOOD (16)
Fuel properties
Softwoods :
Cedar , white
Cypress
Fir, Douglas
Hemlock, western
Pine:
Pitch
White
Yellow
Redwood
Hardwoods :
Ash, white
Beech
Birch, white
Elm
Hickory
Maple
Oak:
Black
Red
White
Poplar
Carbon
48.80
54.98
52.3
50.4
59.00
52.55
52.60
53.5
49.73
51.64
49.77
50.35
49.67
50.64
48.78
49.49
50.44
51.64
Ultimate
analysis, wt %
Hydrogen Sulfur Oxygen Nitrogen
6.37
6.54
6.3
5.8 0.
7.19
6.08
7.02
5.9
6.93
6.26
6.49
6.57
6.49
6.02
6.09
6.62
6.59
6.26
44.46
38.08
40.5 0.1
1 41.4 0.1
32.68
41.25
40.07
40.3 0.1
43,04
41.45
43.45
42.34
43.11
41.74 0.25
44.98
43.74
42.73
41.45
Heating value,
MJ/kg
Ash
0.37
0.40
0.8
2.2
1.13
0.12
0.31
0.2
0.30
0.65
0.29
0.74
0.73
1.35
0.15
0.15
0.24
0.65
Higher
19.5;b
23. Ob
21.1
20.1
26. 3b
20. 7b
22. 4b
21.0
20. 7b
20. 4b
20. lb
20. 4b
20. 2b
20.0
19. Ob
20. 2b
20. 5b
20. 7b
Lower
18.1
21.5
19.6
18.7
24.7
19.5
20.8
19.8
19.1
19.0
18.7
19.0
18.7
18.6
17.6
18.7
19.0
19.3
Atmos . air
required
at zero
excess air,
kg/MJ
0.305
0.306
0.310
0.304
0.302
0.311
0.306
0.311
0.305
0.314
0.307
0.308
0.306
0.310
0.308
0.305
0.308
0.308
Blanks indicate no data reported.
Calculated from reported higher heating value of kiln-dried wood assumed to originally contain 80%
moisture (i.e., 80 g water per 100 g of dry wood).
-------
TABLE 5. COMPOSITION OF ASH FROM TYPICAL GRADES OF WOOD (15)
Weiqht percent of ash
Wood grade
Mockernut hickory
Red oak
White oak
Water oak
Shortleaf pine
Dogwood
White ash
Chestnut
Sycamore
Longleaf pine
Evergreen magnolia
Asha
0.73
0.85
0.37
1.09
0.35
0.95
0.43
0.22
0.99
0.49
0.60
K2O
18.93
16.41
29.90
15.46
12.97
20.03
34.74
13.33
18.24
10.34
11.87
NB2O
3.38
3.68
1.94
7.22
1.18
7.65
0.94
7.67
5.92
2.34
2.52
CaO
25.21
32.25
21.21
32.67
43.31
27.81
17.68
36.43
24.98
37.24
23.64
MgO
6.66
3.58
2.43
4.84
2.11
4.92
0.45
1.56
0.49
4.21
4.69
?2°5
7.98
7.04
6.72
6.38
2.75
1.02
2.69
5.00
9.65
2.65
5.31
503
2.06
2.29
4.11
0.38
0.86
2.72
8.58
2.68
5.73
4.32
3.46
Cl
0.28
0.68
1.00
0.77
0.67
0.74
0.26
0.88
0.45
0.21
0.23
Si02
1.80
0.97
3.20
1.00
2.35
2.00
7.05
4.17
9.66
3.41
7.32
Fe203
0.25
0.21
0.50
0.37
o.'ie
0.12
2.92
2.65
4.13
2.76
1.60
C
1.20
1.38
3.87
0.65
0.74
0.40
1.14
1.19
2.14
1.11
17.22
C02
32.44
31.85
25.16
28.86
33.26
28.16
23.65
24.82
19.01
31.47
22.66
Percent ash in wood based on wood with 10% moisture.
TABLE 6. ELEMENTAL COMPOSITION OF WOOD (15,18)
Mean
Constituent concentration, Number of
formula g/kg
A1203 0.4
CaO 3.1
Cl 0.04
Fe203 0.2
K20 1.1
MgO 0 . 6
MnO 0 . 5
P205 0.3
Si02 0.5
Na20 0.2
Ti02 0.005
samples Reference
4 18
15 15,
11 15
15 15,
15 15,
15 15,
4 18
15 15,
15 15,
11 15
4 18
18
18
18
18
18
18
PYROLYSIS | OXIDATION
—SOLID PHASE-J
BBBilm 'CONDENSED PHASE
•S^KGJ 1g|jt:TiONZON|r
BPlfBBiil ^ VOLATILES
HHMSJiliBil -^ . ,, ,
|
'PHASE ""*
J PRIMARY
1 , COMBUSTION
! '/
GAS !/ PRIMARY AIR /
PHACF 1 \ fj \
REACTION!! SECONDARY
)ZONE i7>osT^ VEFFLUENT)
lj FLAME REACTIONS^ V
RECEDING INTERFACES
Figure 3. Combustion of a solid (19).
Reprinted from The Formation and Emission of Trace Species by J. B. Edwards,
p. 151, by permission of Ann Arbor Science Publishers, Inc.
18
-------
Oxygen diffuses to the solid surface where oxidation of the non-
volatiles occurs, resulting in the release of more heat. Carbon
monoxide and dioxide, water, hydrogen, nitrogen oxides, sulfur
oxides, carbonaceous particulates from noncombusted vapors, and
metallic oxides from the noncombustible constituents may form or
begin to form in the combustion zone.
The postflame region is that region directly downstream of the
combustion zone. Many chemical and physical processes may occur
in the postflame region because the reactants may be both gaseous
and solid. Radical recombination reactions such as the recombi-
nation of atomic oxygen and the formation of water from atomic
hydrogen and the hydroxyl radical occur as the combustion gases
cool. Carbon dioxide and atomic hydrogen are formed by the com-
bination of carbon monoxide and the hydroxyl radical. Pyrolytic
reactions such as the reaction of fuel species and their products
with other hydrocarbons, hydrogenation of hydrocarbons to species
of greater saturation, and the cracking of hydrocarbons are among
the postflame reactions. Finally, nonash particulates may be
formed by both condensation and agglomeration (19).
The high moisture content typical of most woods must be driven
off before ignition can take place. The heat needed for this can
reduce the potential heat recovery from the wood by as much as
15% (13, 16). The general course of thermal degradation of wood
can be described in terms of four reaction zones that develop
parallel to the wood surface (13):
Reaction zone
Zone A, to 200°C
Zone B, 200°C to 280°C
Zone C, 280°C to 500°C
Description
Zone D, above 500°C
Water vapor, formic acid, acetic acid, and possibly
carbon dioxide are evolved. Charring may eventu-
ally occur at temperatures as low as 95°C.
Reaction becomes exothermic between 150°C and 260°C.
With sufficient time - and under favorable condi-
tions - ignition is possible.
Ignitable gases are evolved and block oxygen from
the wood surface, thereby preventing ignition.
Charcoal is formed with a lower thermal conductiv-
ity than wood; thus heat conduction to the center
of the wood - and therefore attainment of the
exothermic reaction point - is delayed. Surface
temperatures high enough for spontaneous combustion
have been reported over the entire range of Zone C.
Charcoal glows.
19
-------
During these combustion processes more than 200 compounds can
potentially be distilled from the wood (20). Under efficient
combustion conditions, these compounds are decomposed; however,
residential wood-fired combustion is often not efficient Creo-
sote, a major constituent of wood distillation, can partially
escape combustion and condense in the chimney. Chimney fires
can be traced to the build up and ignition of this creosote.
During residential combustion fresh wood is placed on top of a
burning fuel bed, as illustrated in Figure 4.
SECONDARY AIR
(OVERFIRE)
GRATE
PRIMARY AIR
(UNDERFIRE
FUEL
(OVERFEED )
SECONDARY
OX I DAT I ON ZONE
2 CO +0j — 2COj
C +02 — COj
PREHEAT ZONE
IGNITION PLANE-
CO
,T
REDUCTION ZONE
OXIDATION"
c+ot—co.
ZONE
ASH LAYER
COMPOSITION
AND TEMPERATURE
Figure 4. Overfeed arrangement of a solid fuel bed (19).
Reprinted from The Formation and Emission of Trace Species by J. B. Edwards,
p. 151, by permission of Ann Arbor Science Publishers, Inc.
The air supply is divided between primary air fed under the bed
(or grate) and secondary air introduced above the fuel bed. Pri-
mary air controls the rate of combustion since the wood cannot be
consumed at a rate greater than the available oxygen permits. A
deficiency or excess of primary air will reduce the bed tempera-
ture and the rate of combustion. Secondary air controls the
overall combustion efficiency by oxidizing unburned or partially
oxidized combustible materials emitted from the fuel bed. Over-
feed firing has a major problem: as fresh fuel is supplied to
the top of the bed, it is preheated with hot combustion gases,
and its volatile components are driven off. Because little or no
oxygen is present in this region, these volatile organics can only
undergo pyrolytic reactions. Therefore, secondary air must be
supplied for oxidation to take place above the fuel bed. However,
excess secondary air can quench the reactions and produce partial
(20) Wood Chemistry, Second Edition, Volume 2. wise, L. E., and
E. C. Jahn, eds. Reinhold Publishing Co., New York, New
York, 1974. pp. 475-479.
20
-------
oxidation products. Usually 30% to 50% total excess air is suf-
ficient to compensate for incomplete mixing and permits optimal
combustion of the wood, although complete combustion is never
attained in residential combustion equipment. Overall excess air
levels for combustion of wood in fireplaces have been measured as
high as 2,000% excess air (9).
Another characteristic of overfeed firing of wood is that com-
bustion gases flow through the fuel bed in channels resulting
in localized areas of high velocity. This high velocity gas en-
trains smaller particles of partially combusted material carrying
them away from the combustion zone.
Most residential wood combustion is batch-fed. When fresh fuel
is placed on top of the fuel bed, a number of process steps are
upset. At this stage of combustion, the flue gas contains the
greatest load of combustible species, and the overall combustion
process is least efficient (19).
SOURCE POPULATION AND GEOGRAPHICAL DISTRIBUTION
Wood-fired residential combustion equipment is used throughout
the United States and is concentrated in heavily forested areas
of the nation as shown in Figures 5 and 6 (21). This distribu-
tion pattern reflects the desire of homeowners to burn fuel that
is readily available and inexpensive.
The number of residential housing units heated with wood is com-
piled by the U.S. Bureau of Census. However, detailed state by
state compilations are only conducted every ten years at the time
of the census. Housing surveys are conducted annually and give
estimated statistics on a regional basis. In addition, statisti-
cal data are only reported for primary heating with wood, not for
auxiliary heating or aesthetic use. In this assessment, two re-
ports from the 1970 U.S. Census of Housing (6, 22) were used in
conjunction with the 1976 annual Housing Survey (1) to estimate
the actual population of wood-fired heating devices used in homes.
Details are presented in Appendix A, and the results are given in
Table 7.
(21) Diller, D. Forest Conservation. In: McGraw-Hill Encyclo-
pedia of Science and Technology, Volume 5. McGraw-Hill Book
Company, New York, New York, June 1960. p. 445.
(22) Census of Housing: 1970, Volume 1, Housing Characteristics
for States, Cities, and Counties, Part 1; United States
Summary. U.S. Department of Commerce, Washington, D.C.,
December 1972. 512 pp.
21
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ROCKY MOUNTAIN
NORTHERN
PACIFIC COAST
CENTRAL HARDWOOD
SOUTHERN
TROPICAL
Figure 5. The natural forest regions
of the United States (21).
E%S% >300,000metrictons/yr
VZffifa 100,000 to 300,000 metric tons/yr
I I < 100,000 metric tons/yr
Figure 6. Estimated residential wood
consumption by state in 1976
22
-------
Wood consumption by the residential sector in 1976 was determined
from the source population and the annual heating degree-days per
state. This methodology has been discussed in other reports
(23-25), and detailed calculations are presented in Appendix A.
Results appear in Table 7.
All 50 states have housing units that are heated by wood. The
greatest concentration is in the Southeast where the heating
season is shorter and milder. Of the approximately 912,000 resi-
dential wood-fired primary heating devices, approximately 39%
are located in the states of Alabama, Georgia, North Carolina,
South Carolina, Tennessee, and Virginia, and about 90% are
located in rural housing.
There is no exact information available on the population of
wood-fired combustion equipment used for auxiliary heat or aes-
thetic purposes. However, data on sales of wood stoves and new
homes built with fireplaces indicate that this population is much
larger than the population of primary heating devices. Estimated
secondary wood consumption is also greater. The assumptions and
rationale used in arriving at the estimates given in Table 7 are
presented in Appendix A.
In order to characterize the source population and evaluate the
potential environmental impact of residential wood combustion,
operating parameters were determined for the average wood stove
and fireplace. It must be recognized that this source exhibits
a high degree of variability that is not reflected in the use of
average parameters. Details are given in Appendix B. The average
wood stove is located in the South region of the United States.
It was estimated that the average wood stove consumes wood at the
rate of 3 kg/hr during the coldest months of the year, and that
the average fireplace consumes wood at the rate of 8.5 kg/hr.
Additional assumptions were (1): Both units have emission
heights of 5.2 m; (2) The population density around the average
source is 21 persons/km2 (55 persons/mile2).
(23) 1973 NEDS Fuel Use Report. EPA-450/2-76-004, PB 253 908,
U.S. Environmental Protection Agency, Research Triangle
Park, North Carolina, April 1976. 124 pp.
(24) Guide for Compiling a Comprehensive Emission Inventory
(Revised). Publication No. APTD-1135, U.S. Environmental
Protection Agency, Research Triangle Park, North Carolina,
March 1973. 204 pp.
(25) Myers, J. P., and F. Benesh. Methodology for Countywide
Estimation of Coal, Gas, and Organic Solvent Consumption.
EPA-450/3-75-086, U.S. Environmental Protection Agency,
Research Triangle Park, North Carolina, December 1975.
152 pp.
23
-------
TABLE 7.
ESTIMATED POPULATION OF WOOD-FIRED RESIDENTIAL
COMBUSTION EQUIPMENT AND WOOD CONSUMED BY THE
RESIDENTIAL SECTOR, 1976
Number of housing
units burning wood3
State
Alabama
Alaska
Arizona
Arkansas
California
Colorado
Connecticutt
Delaware
Florida
Georgia
Hawaii
Idaho
Illinois
Indiana
Iowa
Kansas
Kentucky
Louisiana
Maine
Maryland
Massachusetts
Michigan
Minnesota
Missippi
Missouri
Montana
Nebraska
Nevada
New Hampshire
New Jersey
New Mexico
New York
North Carolina
North Dakota
Ohio
Oklahoma
Oregon
Pennsylvania
Rhode Island
South Carolina
Primary
59,200
3,600
15,200
53,500
54,000
2,000
2,300
700
25,200
70,700
2,600
6,700
3,100
6,800
1,600
3,400
26,700
17,000,
15,900°
6,500
3,000
6,300
7,700
56,700
45,100
5,100
1,300
1,600,
5,000
2,500
18,500
15,900
65,000
200
5,400
13,700
39,900
14,100
500
48,800
Auxiliary
or aesthetic
586,000
64,500
414,500
278,300
4,329,900
492,100
589,200
73,300
1,180,300
618,800
143,400
151,100
1,608,400
753,600
421,300
344,100
557,100
469,100
284,800
520,300
1,103,200
1,258,900
559,600
362,100
711,000
144,000
227,700
120,300
220,800
1,380,800
736,100
3,577,100
684,100
89,000
1,515,600
379,500
556,400
2,271,600
179,200
342,000
Fuel consumption,
metric tons/vr
Primary
150,000
50,000
36,000
280,000
190,000
18,000
22,000
5,000
30,000
340,000
1,000
60,000
29,000
58,000
17,000
25,000
190,000
38,000
180,000
47,000
26,000
76,000
110,000
200,000
•330,000
60,000
12,000
15,000
57,000
19,000
120,000
150,000
340,000
3,000
47,000
78,000
290,000
120,000
5,000
200,000
Auxiliary
or aesthetic
390,000
43,000
60,000
120,000
620,000
100,000
190,000
19,000
300,000
270,000
21,000
31,000
390,000
180,000
100,000
82,000
200,000
120,000
460,000
130,000
360,000
510,000
410,000
130,000
290,000
30,000
54,000
17,000
350,000
280,000
94,000
1,200,000
170,000
21,000
360,000
62,000
290,000
460,000
76,000
87,000
(continued)
24
-------
TABLE 7 (continued)
State
Number of housing
units burning wood
Auxiliary
Primary or aesthetic
Fuel consumption,
metric tons/yr
Auxiliary
Primary or aesthetic
South Dakota
Tennessee
Texas
Utah
Vermont
Virginia
Washington
West Virginia
Wisconsin
Wyoming
Total
1,700
60,500
26,500
1,200.
2,700
48,200
22,200
5,100
7,900
900
912,000
96,100
697,800
1,000,200
204,100
125,600
635,600
853,400
237,800
644,800
73,400
35,467,900
21,000
320,000
87,000
11,000
33,000
280,000
210,000
36,000
90,000
10,000
5,100,000
23,000
890,000
410,000
42,000
200,000
160,000
450,000
60,000
260,000
15,000
11,500,000
Each housing unit was assumed to contain only one wood-fired
combustion device.
3 A dramatic increase has been noted since 1976 in primary heating
with wood in New England because of rising fuel costs. Recent
estimates indicate 20% of the homes in Maine and New Hampshire
and 18% of the homes in Vermont employ wood for primary heating
(26-28).
(26) Vermont Surveys Wood Stove Use. Wood'N Energy, 3(2):8,
September 1978.
(27) Turner, A. Personal communication. Vermont Energy Office,
Montpelier, Vermont, October 1979.
(28) Shapiro, A. Personal communication. Wood Energy Research
Corporation, Camden, Maine, October 1979.
25
-------
SECTION 4
EMISSIONS
SELECTED POLLUTANTS
Residential combustion of wood produces a number of atmospheric
emissions and a solid residue. Atmospheric emissions include
particulates, sulfur oxides, nitrogen oxides, carbon monoxide,
organic materials including POM's, and mineral constituents. The
solid residue is composed of inert materials in the fuel (ash)
unburned or partially burned fuel, and materials formed durinq
combustion.
Organic species, carbon monoxide, and to a large extent the par-
ticulate matter emissions result from incomplete combustion of
the fuel. Sulfur oxides arise from oxidation of fuel sulfur
while nitrogen oxides are formed both from fuel nitrogen and by
the combination of atmospheric nitrogen with oxygen in the com-
bustion zone. Mineral constituents in the particulate emissions
result from minerals in the wood that are released from the wood
matrix during combustion and entrained in the combustion gases.
Polycyclic organic materials result from the combination of free
radical species formed in the flame. The synthesis of these
molecules is dependent on many combustion variables, including
the presence of a chemically reducing atmosphere. Under reducing
conditions, radical chain propagation is enhanced, allowing the
buildup of a complex organic molecule such as a POM compound.
A list of POM species encountered during sampling is presented
onnfo 1\Table 9- Because POM compounds melt/sublime at about
^00 C, which is approximately 100°C higher than exhaust qas
temperatures for this source (29), they should be in the con-
densed phase when emitted.
(29) Preliminary Characterization of Emissions from Wood-fired
Residential Combustion Equipment. EPA-600/7-80-040, U.S.
Environmental Protection Agency, Research Triangle Park,
North Carolina, March 1980. 153 pp.
26
-------
EMISSIONS DATA
Little work has been done to characterize the emissions from
wood-fired residential combustion sources. A few measurements
of emissions from wood-fired combustion units have been reported
within the past ten years. The limited amount of emissions data
available on the residential combustion of wood is attributed to
the increasingly small role that wood played in the primary heat-
ing of homes in the past.
The 1973 oil embargo and the current energy crisis have created a
renewed interest in wood-fired residential combustion. As a re-
sult, characterization studies have been undertaken on the local,
State, and Federal levels. As a part of this effort, a special
sampling project was conducted under the Source Assessment program
to better quantify criteria pollutant emissions and characterize
other types of emissions from this source. Three wood-burning
units - a zero clearance fireplace, a baffled stove, and a non-
baffled stove - and four wood types - oak and pine, both seasoned
and green - were tested. A complete description of the sampling
project and test results appears in a separate report (29).
Emissions data from all available sources are compiled for refer-
ence in Appendix C. Average emission factors based on this data
are presented in Table 8 (9, 29-33). In some cases test results
were reported as pollutant concentrations in the exhaust gas in-
stead of as emission factors, and material balance considerations
were needed to convert from one to the other. These calculations
and the averaging procedures used in arriving at Table 8 are also
included in Appendix C.
(30) Clayton, L. , G. Karels, C. Ong, and T. Ping Emissions from
Residential Type Fireplaces. Source Tests 24C67, 26C,
29C67, 40C67, 41C67, 65C67, and 66C67, Bay Area Air Pollu-
tion Control District, San Francisco, California,
January 31, 1968. 6 pp.
(31) Butcher, S. S., and D. I. Buckley. A Preliminary Study of
Particulate Emissions from Small Wood Stoves. Journal of
the Air Pollution Control Association, 27 (4) : 346-347,
April 1977.
(32) Source Testing for Fireplaces, Stoves, and Restaurant Grills
in Vail, Colorado. Contract 68-01-1999, U.S. Environmental
Protection Agency, Region VIII, Denver, Colorado. (Draft
document submitted to the EPA by PEDCo-Environmental, Inc.,
December 1977.) 29 pp.
(33) Butcher, S. S., and E. M. Sorenson. A Study of Wood Stove
Particulate Emissions. Journal of the Air Pollution Control
Association, 29 (7):724-728, 1979.
27
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TABLE 8. AVERAGE EMISSION FACTORS FOR WOOD-FIRED RESIDENTIAL COMBUSTION9
to
CO
Emission
species
Total particulates
Filterable
particulates
Condensable organics
SOX
NOX
CO
Hydrocarbons
POM
Major organic
species
Pentanol
Acetaldhyde
I sobutyraldehyde
Formaldehyde
Propionaldehyde
n-Butyr aldehyde
Phenols
Total carbonyls
(as CHOH)
Organic acids
(as CH3COOH)
Additional organics
(including CH^)
Emission factor,
g/kg
Wood
stove
9.1
3.6
5.5
0.2
0.49
130
13
0.27
1.6
0.07
0.11
1.5
0.23
0.15
0.47
Fire-
place
13
2.8
10
2.0
67
74
0.029
0.55
0.70
1.4
1.5
0.2
1.0
4.4
6.4
27
Emission factor
range , g/kg
Wood
stove
1.0 -
1.8 -
3.3 -
0.16 -
0.2 -
91
0.3 -
0.19 -
1.1 -
0.03 -
0.03 -
0.1 -
0.1 -
0.1 -
0.2 -
28
7.0
12.0
0.24
0.8
370
44
0.37
2.6
0.1
0.2
4.3
0.3
0.2
0.6
Fire-
place
2.4
1.8
5.9
0.84
15
2.1
0.017
0.46
0.29
0.4
<0.02
1.6
<0.02
9.6
- 26
4.8
9.1
4.3
- 140
- 300
0.044
0.64
1.3
1.6
2.4
9.4
- 15
- 44
Reference
9, 29-33
9, 29
29
29
29, 30
9, 29, 30, 32
9, 29, 32
9, 29
29
29
29, 30
29
29, 30
29
29
30
30
30
30
The data used in obtaining these average emission factors, as well as the procedure
for averaging them, can be found in Appendix C.
-------
Distinct average emission factors were calculated for wood-burning
stoves and fireplaces because emissions from the two kinds of
units have been shown to differ significantly (9, 29-33). All
emissions data are for uncontrolled emissions, because no emission
control devices are used in the residential sector. A discussion
of the emissions data for individual emission species follows.
When possible, the effect of various operating parameters (e.g.,
wood type, combustion equipment, or burning cycle) on emissions
is indicated.
Particulate Material
Interpretation of particulate emissions data is difficult because
of the large amount of condensable organic material present in
the exhaust gas. Test results are strongly dependent on the
methods used to collect samples, and different studies have em-
ployed different methods. The standard method recognized by EPA
for collection of particulate samples, EPA Method 5, consists of
a sampling probe connected to a filter held at >100°C, followed
by a series of impingers in an ice bath, a sampling pump, and a
dry gas meter (34). Normally everything.collected on or before
the filter in the front half of the sampling train is considered
the particulate catch. However, during sampling tests on resi-
dential wood combustion a significant quantity of organic mate-
rial passes through the filter in the vapor phase and condenses
in the impingers. This material generally weighs more than the
particulate catch from the front half of the train. Because
this organic material would normally condense in the atmosphere
(some of it may in fact condense within the chimney), it can be
considered as a part of the total particulate emissions.
In order to reduce ambiguity, the following terminology has been
employed in evaluating particulate emission test data.
• Filterable particulates - All material collected on or
before the filter of the sampling train. This includes
organic material not in the vapor phase that is collected
on the filter.
• Condensable organics - Organic material that condenses
in the impingers of a sampling train.
• Total particulates - The sum of filterable particulates
and condensed organics.
(34) Environmental Protection Agency - Part II - Standards of
Performance for New Stationary Sources - Revision to Refer-
ence Method 1-8. Method 5 - Determination of Particulate
Emissions from Stationary Sources. Federal Register,
42(160):41776-41782, August 1977.
29
-------
Five previous studies have characterized particulate emissions
from wood-fired residential combustion sources. These studies
indicate that there is no significant difference between the
emissions from fireplaces and wood stoves. Average particulate
emission factors range from 1.0 g/kg to 28 g/kg. Although the
methods of collection and quantification are not consistent
each study indicates a degree of variability in emission factors
which can be attributed to the variable nature of the combustion
process. Factors such as the addition of fresh wood charges
fuel bed configuration, size of fuel charge, etc., all have some
effect on emissions generated from fireplaces and wood burning
stoves. 3
Analysis of particulates for carbon, hydrogen and nitrogen indi-
cated a composition similar to that of wood. The composition
remained unchanged upon extraction with methylene chloride. The
particulates were a dark brown or black sooty, carbon-black-like
material which exhibited some resinous qualities (29).
Sulfur Oxides
Sulfur oxides are formed during combustion by the oxidation of
sulfur in the fuel. They are not released to any great extent
in residential wood combustion because the sulfur content of wood
is low, typically <0.1% in branches and wood components (35).
Only one study has examined emissions of sulfur oxides during
residential wood combustion, and that study was limited to two
tests using EPA Method 6. Results were close to the detection
limit for the method, and gave emission factors of 0.16 g/kg and
0.24 g/kg (29). These values are nearly equal to those expected
based on material balance considerations, assuming 100% conver-
sion of fuel sulfur to SO2.
Recent work with burning of wood bark suggests a substantially
lower conversion rate (approximately 5%) of bark sulfur to SO2,
with the balance accounted for in the bottom ash combustion
products (36). This study employed a more sensitive measurement
technique and also determined the sulfur content of the ash.
Most of the fuel sulfur was recovered in the ash, confirming the
low sulfur levels found in the stack gas.
(35) Shriner, D. A., and G. S. Henderson. Sulfur Distribution
and Cycling in Dedicuous Forest Watershed. Journal of
Environmental Quality, 7 (3):392-397, 1978.
(36) Oglesby, H. S., and R. 0. Blosser. Information on the Sul-
fur Content of Bark and Its Contributions to S02 Emissions
When Burned as Fuel. Paper 79-6.2, Presented at the 72nd
Annual Meeting of the Air Pollution Control Association,
Cincinnati, Ohio, June 24-29, 1979.
30
-------
Nitrogen Oxides
Nitrogen oxide formation depends primarily on fuel nitrogen con-
tent, amount of excess air used, combustion temperature and de-
sign of combustion equipment. Average emission factors have been
found to range from 0.2 g/kg to 0.8 g/kg for wood stoves and from
0.8 g/kg to 4 g/kg for fireplaces (29, 30).
Based on average emission factors, fireplaces emit about four
times as much NOX as stoves per unit of wood burned. Increased
NOX emissions are generally associated with higher combustion
temperatures. This is consistent with the lower CO and POM
emissions (products of incomplete combustion) associated with
fireplaces since higher combustion temperatures are indicative
of greater combustion efficiency. A possible explanation for
this may be the higher combustion air velocities associated with
the fireplace which cause more rapid burning and thus higher
temperatures.
Carbon Monoxide
Carbon monoxide is a product of incomplete combustion and is a
major pollutant emitted from wood-burning fireplaces and stoves.
Average emissions of carbon monoxide are highly variable, ranging
from 91 g/kg to 370 g/kg for wood stoves and from 15 g/kg to
140 g/kg for fireplaces. Although emission factors for the wood-
burning stoves appear higher, a statistical analysis showed no
significant difference. According to this analysis an unaccounted
for variable exerted significant influence on the CO emission
factors. This same study also indicated that CO formation is very
sensitive to changing fuel bed conditions which may account for
the variability between replicate test results (29).
Condensable Organics
Condensable organic emissions are usually determined by measuring
the mass of material collected in the back of the EPA Method 5
particulate train. The back half of this train consists of im-
pingers containing distilled water and a back-up filter which
collects most of the materials passing through the front-half
filter. This material is often considered as part of the parti-
culate emissions.
Average emission factors range from 3.3 g/kg to 12 g/kg, with no
significant difference between fireplace and wood stove emissions.
However, emissions are over two times higher when burning green
pine than when burning other wood types tested. It has been
shown that the condensable organics account for 54% to 76% of
the total mass collected by the EPA Method 5 train (29).
31
-------
Volatile Hydrocarbons
Low-molecular-weight volatile hydrocarbon emissions have been
measured in three studies (9, 29, 32). Two of the studies (9,
32) measured total volatile hydrocarbon emissions from fireplaces
while the remaining study (29) measured volatile hydrocarbon
species in the d to C6 range from a fireplace and two wood-
burning stoves.
Measurement of volatile hydrocarbons was accomplished by collec-
tion of a gas sample in an inert gas sampling bag and subsequent
injection into a gas chromatograph with a flame ionization detec-
tor (GC/FID) . The resultant emission data demonstrates a high
degree of variability in volatile hydrocarbon emissions ranging
from 0.3 g/kg to 3 . 0 g/kg from wood-burning stoves and from
2 g/kg to 400 g/kg from fireplaces.
Major Organic Species
Four studies have been conducted to quantify and characterize
organic species present in the emissions of wood-fired combustion
equipment (9, 29, 30, 33). Preliminary analyses of total partic-
ulate matter (33) indicated that benzene extractables range from
42% to 67% of the total particulate mass. About 45% of the mass
of benzene extractables appeared in the neutral fraction of acid
base extractions. Polycyclic aromatic hydrocarbons are expected
to be included in this neutral fraction. Other fractions included
carboxylic acid fraction (15%), phenol fraction (40%) and organic
base fraction (^1%) (33).
Another study to characterize major organic species was conducted
on four fireplaces in the San Francisco area (9). Emissions of
organic acids, phenols, formaldehyde, and acetaldehydes were
quantified while burning eucalyptus, oak and madrone. Emission
data for this study are presented in Appendix C and range from
<0.03 g/kg to 29 g/kg for organic acids, <0.04 g/kg to 4.8 g/kg
for phenols, 0.3 g/kg to 11 g/kg for formaldehyde and 0.4 q/kq
to 2.5 g/kg for acetaldehyde.
A more extensive characterization of organic emission was accom-
plished as part of the Source Assessment program (29). Major
organic species were collected using the Source Assessment Samp-
ling System (SASS) train and a modified Method 5 train equipped
with an XAD-2 resin trap. This study found that a significant
quantity of organic matter was trapped in the aqueous impingers
after passing through the filter and XAD-2 resin trap. That
which was recovered from the resin and the particulate fractions
would only partially dissolve in hexane during the sample workup.
A portion of this insoluble material was soluble in methylene
chloride, but there remained an insoluble solid white residue.
32
-------
It was found that the hexane-soluble fraction was totally chro-
matographable by GC/MS, while the methylene chloride fraction^
hexane-insoluble material was largely nonchromatographable. The
chromatographable fraction, however, did contain approximately
50% of the POM compounds recovered from the total system. The
nonchromatographable portion was found to contain a variety of
high molecular weight fused-ring aromatics (e.g., POM s, MW
greater than 302).
The organic material recovered from the aqueous portion of the
sampling train was for the most part nonchromatographable. Ions
associated with organic acids were found and determined to be of
molecular weight greater than 284, e.g., stearic acid. The de-
tection limit of GC/MS for organic acids is quite high and their
presence may go undetected.
Over 50 organic species were identified, in addition to POM com-
pounds, in the flue gas from wood-burning stoves and fireplaces.
Specific organic acids (i.e., acetic acid, formic acid, etc.)
were not identified because of the very high detection limit,
but their presence was substantiated as mentioned earlier. The
organic species emitted were dominated by the naphthalenes,
furans, phenols, cresols, and aldehydes. Total organic emission
factors, except POM's, based on individual speciation for each
condition ranged from 1.1 g/kg to 2.6 g/kg for wood stoves and
0.46 g/kg to 0.64 g/kg for fireplaces. A list of the organic
compounds detected is given in Table 9.
Emission factors for POM compounds and total POM's were also
generated during this study. The average emission factors for
fireplace emissions range from 0.025 g/kg to 0.036 g/kg. This
range is an order of magnitude lower than the total POM emissions
from wood stoves which range from 0.19 g/kg to 0.37 g/kg. This
is consistent with the CO and NOX results, which indicate more
efficient combustion and/or higher combustion temperatures in
the fireplace. The total POM emissions from fireplaces are in
agreement with results from another study (9). The average
emission factors for fireplace emissions from this earlier study
range from 0.017 g/kg to 0.044 g/kg. A list of POM compounds
detected during sampling is also given in Table 9.
Trace Elements
One study to date has characterized trace element emissions from
wood-fired residential heating equipment (29). Table 10 presents
emission factors for 29 elements identified in the analysis of
samples taken while burning green pine in the nonbaffled stove.
The emission factors determined during this study range from
1.4 x 10-7 g/kg to 4.2 x 10~2 g/kg. The highest values measured
(1.8 x 10-2 g/kg for silver and 4.2 x 10~2 g/kg for zinc) are
believed to be in error. The analytical procedure tends to give
high readings at low concentrations for silver, and many of the
33
-------
TABLE 9. MAJOR ORGANIC SPECIES AND POM COMPOUNDS
DETECTED IN EMISSIONS FROM WOOD-FIRED
RESIDENTIAL COMBUSTION EQUIPMENT (9, 29)
Major organic species
POM compounds
Ethyl benzene/xylenes
Indane
Indene
Methyl indanes
Methyl indenes
Naphthalene
Methyl-naphthalenes
Ca-alkyl-naphthalenes
Biphenyl
Acenaphthylene
Acenaphthene
Benzo furan
Dibenzo furan
Fluorene
Anthracene/phenanthrene
Phenol
Cresols
Ca-alkyl phenols
Ca-alkyl phenols
C^-alkyl phenols
Benzaldehyde
C-i-alkyl benzaldehyde
Ca-alkyl benzaldehyde
C3-alkyl benzaldehyde
Methyl furans
Ca-alkyl-furans/furfural
C3-alkyl-furans/methylfurrural
C^-alkyl-furans/Ca-alkylfurfural/
methoxy phenols
Catechol
Naphthol
Methoxy phenols
Methyl methoxy phenols
Ca-alkyl methoxy phenols
Ca-alkyl methoxy phenols
C«»-alkyl methoxy phenols
Cs-alkyl methoxy phenols
Fluorenone
Fluorenone isomer
Anthrone
Benzanthrone
Dimethoxy phenol
Hydroxy methoxy benzaldehyde
Hydroxy methoxy acetophenone
Hydroxy methoxy benzole acid
Hydroxy dimethoxy benzaldehyde
Hydroxy dimethoxy acetophenone
Hydroxy dimethoxy cinnamaldehyde
Ca-alkyl biphenyls (or isomers)
Ca-alkyl biphenyls (or isomers)
C<»-alkyl biphenyls (or isomers)
Di-Cs-alkyl-phthalate
Anthracene/phenanthrene
Methyl-anthracenes/-phenanthrenes
C2-alkyl-anthracenes/-phenanthrenes
Cyclopenta-anthracenes/-phenanthrenes
Fluoroanthene
Pyrene
Methyl-fluoranthenes/-pyrenes
Benzo(ghi)fluoranthene
Cyclopenta[ed]pyrene
Benzo(c)phenanthrene
Benz(a)anthracene/chrysene
Methyl-benzanthracenes
-benzphenanthrenes/-chrysenes
C2-alkyl-benzanthracenes/
-benzophenanthrenes/
-chrysenes
Benzofluoranthenes
Benzopyrenes/perylene
Methyl cholanthrene
Indeno(1,2,3-ed)pyrene
Benzo(ghi)perylene
Anthanthrene
Dibenzanthracenes/-phenanthrenes
Dibenzopyrenes
34
-------
elements (including silver) were near their detection limits in
this analysis. The high reading for zinc may result from volatil-
ization of zinc from the galvanized stack.
The ash composition of wood can range from 0.2% to 2.2%,_with
calcium, potassium, phosphorus, sodium, and magnesium being the
predominant elements (15, 18). These same elements have rela-
tively high emission factors in Table 10 (on the order of 10~3
g/kg), but the absolute value of the emission factors is two or
three orders of magnitude lower than their typical concentration
in wood. Thus, only a small fraction of the trace element con-
tent of wood is emitted to the atmosphere, with the majority
remaining as a component of bottom ash.
TABLE 10. ELEMENTAL EMISSIONS FROM A
NONBAFFLED WOODBURNING STOVE (29)
Emission
species
Aluminum
Antimony
Arsenic
Barium
Beryllium
Boron
Cadmium
Calcium
Chromium
Cobalt
Copper
Iron
Lead
Magnesium
Manganese
Emission
factor,
g/kg
1.
2.
1.
2.
1.
7.
3.
4.
9.
6.
1.
3.
4.
2.
1.
5
3
3
0
4
3
6
7
0
0
7
1
8
9
9
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
10-
10-
10-
10-
10-
10-
10-
10-
10-
10-
10-
10-
10-
10-
10-
3
5
4
4
7
4
5
3
4
5
4
3
4
4
4
Emission
species
Mercury
Molybdenum
Nickel
Phosphorus
Selenium
Silicon
Silver
Sodium
Strontium
Tin
Titanium
Vanadium
Yttrium •
Zinc
Emission
factor,
g/kg
1.
2.
1.
7.
1.
2.
1.
3.
1.
3.
1.
1.
9.
4.
3
3
7
0
3
7
8
0
1
8
0
5
3
2
X
X
X
X
X
X
X
X
X
X
X
X
X
X
10-
10-
10-
10-
10-
10-
10-
10-
10-
10-
10-
10-
10-
10-
4
4
3
S
4
3
2
3
5
5
5
5
5
2
POTENTIAL ENVIRONMENTAL EFFECTS
Of significant concern in residential wood combustion are the
possible environmental and health effects. These were addressed
in this study through bioassay testing of combustion emissions
and by means of certain evaluati >n criteria established under
the Source Assessment program.
35
-------
Bioassay Testing
Bioassay tests were conducted on stack emission and bottom ash
samples from residential wood-fired combustion equipment (29, 37).
Results of these tests are presented in Table 11.
Discussions of the results observed for each bioassay test are
given in the following subsections. Specific test procedures
can be found in a report prepared by Litton Bionetics, Inc.,
(LBI) for the EPA under a separate contract (37).
Ames Mutagenicity Assay—
The Ames Mutagenicity Assay test evaluates samples for genetic
activity in the Salmonella/microsome plate assays with and with-
out the addition of mammalian metabolic activation preparations.
The genetic activity of a sample is measured in these assays by
its ability to revert the Salmonella indicator strains from
histidine dependence to histidine independence. The degree of
genetic activity of a sample is reflected in the number of rever-
tants that are observed on the histidine free medium.
The results shown in Table 11 show that all of the emission sam-
ples (twenty-four) tested exhibited mutagenic activitiy. None of
the four samples of combustion residue showed mutagenic activity
\ -3 / ) •
CHO Clonal Toxicity Assays—
This test determined the cytotoxicities of twenty-four residential
wood combustion emission samples to cultured Chinese hamster cells
(CHO-K1 cell line). The measure of cytotoxicity was the reduction
in colony-forming ability after a 24-hour exposure to the test
material. After a period of recovery and growth, the number of
colonies that developed in treated cultures was compared to the
colony number in unexposed vehicle control cultures. The concen-
tration of test material that reduced the Colony number by 50%
was estimated graphically and referred to as the EC50 value
(effective concentration for 50% survival). The toxicity of the
test materials is evaluated as high, moderate, low, or nondetect-
able according to the range of EC50 values (Table 12).
The cytotoxicity results indicated that the combined organic
module rinse plus SAD-2 resin extracts were, as a group, more
toxic than the particulate catch extracts. Within each group,
(37) Level I Bioassays on Thirty-two Residential Wood Combustion
Residue Samples. Contract 68-02-2681, U.S. Environmental
Protection Agency,. Research Triangle Park, North Carolina.
(Final report submitted to the EPA by Litton Bionetics, Inc.
November 1979). 211 pp.
36
-------
TABLE 11. RESULTS OF BIOASSAYS PERFORMED ON SASS
AND COMBUSTION RESIDUE SAMPLES (29, 37)
Sample
code3
A-l (1)
A-l (2)
A-l (3)
A-2 (1)
A-2 (2)
A-2 (3)
A-3 (1)
A-3 (2)
A-3 (3)
A-4 (1)
A-4 (2)
B-l (1)
B-l (2)
B-2 (1)
B-2 (2)
B-2 (3)
B-3 (1)
B-3 (2)
B-3 (3)
B-4 (1)
B-4 (2)
C-l (1)
C-l (2)
C-2 (1)
C-2 (2)
C-2 (3)
C-3 (1)
C-3 (2)
C-3 (3)
C-4 (1)
C-4 (2)
C-4 (3)
Note:
ff^-rtro c
Combustion
equipment
Fireplace
Fireplace
Fireplace
Fireplace
Fireplace
Fireplace
Fireplace
Fireplace
Fireplace
Fireplace
Fireplace
Baffled stove
Baffled stove
Baffled stove
Baffled stove
Baffled stove
Baffled stove
Baffled stove
Baffled stove
Baffled stove
Baffled stove
Nonbaffled stove
Nonbaffled stove
Nonbaffled stove
Nonbaffled stove
Nonbaffled stove
Nonbaffled stove
Nonbaffled stove
Nonbaffled stove
Nonbaffled stove
Nonbaffled stove
Nonbaffled stove
Ames
Bioassay test
Acute
CHO clonal rodent Freshwater
Wood type mutagenicity toxicity0 RAM quantal daphniac
Seasoned oak +
Seasoned oak +
Seasoned oak
Green oak +
Green oak +
Green oak
Seasoned pine +
Seasoned pine +
Seasoned pine
Green pine +
Green pine +
Seasoned oak +
Seasoned oak +
Green oak +
Green oak +
Green oak
Seasoned pine +
Seasoned pine +
Seasoned pine
Green pine +
Green pine +
Seasoned oak +
Seasoned oak +
Green oak +
Green oak +
Green oak
Seasoned pine +
Seasoned pine +
Seasoned pine
Green pine +
Green pine -t-
Green pine -
Blanks indicate samples were not submitted
iT-innrla f-n ^-hf^ fnllnw
'i na samnle fractions: i
H
H
L
H
H
ND
H/M
H
NT
H
H
M
H
H
H
L
H
H
L
H/M
H
H
H
H
H.
NT
H
H
ND
H
H
for testing.
(11 oarticulate catch extract, supplied to LBI
as methylene chloride solutions; (2) combined organic module rinse and XAD-2 extract, supplied
to LBI as dimethyl sulfoxide solutions; (3) combustion residue (bottom ash), supplied to LBI as
dry ash.
b"+" designates mutagenic activity; "-" designates no mutagenic activity.
ND, no detectable toxicity;
toxicity.
NT, not tested; L, low toxicity; M, moderate toxicity; H, high
-------
TABLE 12. DEFINITION OF RANGE OF EC5o VALUES
EC50 values,
Toxicity yg/L
High <10
Moderate 10 to 100
Low 100 to 1,000
Nondetectable >1,000
Formulated by Litton Bio-
netics, Inc., under EPA Con-
tract 68-02-2581, Technical
Directive No. 301.
the fireplace samples were either the least toxic or in the least
toxic half of the test samples, and the nonbaffled stove extracts
were generally the most toxic. No generalizations regarding the
fuel source were apparent. Twenty-one of the twenty-four samples
tested were considered highly toxic, the others were described as
moderately toxic, or at the moderate-to-high toxicity borderline.
These results are given in Table 11 (37).
Rabbit Alveolar Macrophage (RAM) Cytotoxicity Assays—
This assay determined the cytotoxicities of four bottom ash sam-
ples to rabbit alveolar macrophages in short term culture. The
cells were exposed to the test material for 20 hours and the
following five cellular variables were measured: percent via-
bility index, total protein, total ATP, and ATP content per 106
cells. Each parameter was compared to the corresponding value
obtained for untreated control cell cultures. Then the concen-
trations of test material that reduced each parameter by 50%
were estimated graphically and referred to -as the EC50 values.
This assay was limited to applied concentrations in the 3 yg/L
to 1,000 yg/L range.
All four test materials (bottom ashes) were evaluated as having
low toxicity to RAM cells because the most sensitive assay param-
eter (usually ATP content) yielded EC50 values in the 100 to
1,000 yg/L concentration range (37).
Level I Rodent Toxicity—
The Level I rodent toxicity test evaluates the acute toxicity of
the test materials when administered orally to male and female
rats. Attempts were made to test two combustion residue (ash)
samples. This test was abandoned when it proved impossible to
prepare a liquefied form of the combustion residue (37).
38
-------
Freshwater Toxicity Assays —
Freshwater toxicity assay determines the toxicity of the combus-
tion residue samples during 48-hour static exposure. The acute
toxicities of two of the combustion residue samples were deter-
mined for the freshwater invertebrate Daphnia magna.
The toxicity of the test materials is evaluated as high, moderate,
low, or nondetectable according to the range of EC5o values
(Table 12). Both samples tested had nondetectable toxicity (37).
Environmental Evaluation Criteria
A series of evaluation criteria (source severity, affected popu-
lation, state emissions burden, and national emissions burden)
was established under the Source Assessment program to provide a
uniform basis for comparing the relative environmental effects
of different source types. Because these criteria are generally
based on average source parameters and employ certain assumptions
and approximations, they are not intended to provide an absolute
measure of environmental impact. Rather, they are to be used in
conjunction with other similar studies to set priorities for
sources where emissions reduction may be required.
In this program source severity and affected population are used
as measures of local environmental impact. Severity is defined
as:
s =
where Xmax = the time-averaged maximum ground level concentra
tion for each emission species.
F = hazard factor
= primary ambient air quality standard (PAAQS) for
criteria pollutants (particulates , hydrocarbons,
NOX, SOX, and CO)
= a reduced threshold limit value (TLV®) for non-
criteria pollutants (i.e., TLV x 8/24 x l/100)a
3/24 = correction factor to adjust the TLV to a 24-hr exposure
level. 1/100 = arbitrary safety factor.
39
-------
Values of Xmax were computed for an average residential source
(as described at the end of Section 3) using the equation
suggested by Turner (38):
xmax xmax
O . 1 7
where Xmax -"-s ^-^e "instantaneous" (i.e., 3-min average) maximum
ground level concentration as determined from the equation:
(3)
max ireuH
where Q = emission rate, g/s
H = stack height, m
TT = 3.14
e = 2.72
u = wind speed, m/s
= 4.5 m/s (national average)
t = 3 min
t = averaging time, min
Averaging times used in the calculation of Xmax f°r the criteria
pollutants were the same as those specified in the corresponding
primary ambient air quality standards (PAAQS) . For noncriteria
pollutants, a 24-hour averaging time was employed.
Average emission rates were calculated from the average emission
factors in Table 8 and the wood consumption rate of the average
source (3 kg/hr for wood stoves and 8.5 kg/hr for fireplaces).
The average stack height was taken to be 5.2 m (Appendix B) .
Further details on the derivations of the severity equations are
given in the literature (3).
Table 13 presents the values of source severity for the average
source. TLV's (39) for noncriteria pollutants and ambient air
quality standards for criteria pollutants (40-42) are also listed.
(38) Turner, D. B. Workbook of Atmospheric Dispersion Estimates.
Public Health Service Publication No. 999-AP-26, U.S.
Department of Health, Education, and Welfare, Cincinnati,
Ohio, May 1970. 84 pp.
(39) TLVs® Threshold Limit Values of Chemical Substances and
Physical Agents in the Workroom Environment with Intended
Changes for 1976. American Conference of Governmental
Industrial Hygienists, Cincinnati, Ohio, 1976. 94 pp.
(40) Federal Register, 36:22384, November 25, 1971.
(41) Federal Register, 43:46258, October 5, 1978.
(42) Federal Register, 44:8220, February 8, 1979.
40
-------
TABLE 13. SOURCE SEVERITY FOR AVERAGE WOOD-FIRED
RESIDENTIAL COMBUSTION UNITS3
Source severity
Emission species
Total particulates
Filterable particulates
SOX
NOX
Hydrocarbons
CO
POM
Formaldehyde
Acetaldehyde
Phenols
PAAQS,
mg/m3
0.260
0.260
0.365
0.100
0.160C
40.0
TLV,
mg/m3
0.001
3.0
180
19
Wood
stove
0.02
0.008
0.0003
0.004
0.063
0.004
46
0.013
0.0001
Fire-
place
0.08
0.02
0.05
1.1
0.005
14
0.23
0.002
0.03
Blanks indicate no data available.
Emissions assumed constant over a 24-hr period during the
heating season.
Q
There is no primary ambient air quality standard for hydro-
carbons. The value of 160 yg/m3 used for hydrocarbons in
this report is a recommended guideline for meeting the
primary ambient air quality standard for oxidants.
Because EPA, in this program, assigned the low TLV of 1 yg/m3 to
potential carcinogens, POM emissions have the highest severities.3
The Source Assessment program has utilized an estimated "TLV"
for carcinogens of 1 yg/m3. The basis for this value is found
in Reference 43. According to the data presented in Figure 13
on page 90 of Reference 43, the ambient level of carcinogens is
4.9 ng/m3, which was adopted as an approximate hazard factor,
F, in the source severity equation. The "TLV" was devised by
multiplying 4.9 ng/m3 by the safety factor of 300 to arrive at
1.47 yg/m3, which was rounded off to 1 yg/m3 for use in the
Source Assessment program. Use of 1 yg/m3 yields a hazard
factor which approximately corresponds to the carcinogen expos-
ure experienced by nonsmokers.
(43) Handy, R. and A. Schindler. Estimation of Permissible
Concentrations of Pollutants for Continuous Exposure.
EPA-600/2-76-155, U.S. Environmental Protection Agency,
Research Triangle Park, North Carolina, June 1976. 148 pp.
41
-------
Severities for individual residential sources may differ greatly
from the values given in Table 13 because of the variability found
in the population. Those parameters that significantly affect
severity include emission factors,3 wood consumption rates,3
duration of burning,3 stack heights, and wind speeds. In addi-
tion, the hazard factors_for noncriteria pollutants and the equa-
tions used to calculate Xmax contain a number of assumptions. An
in-depth study of all these factors would be necessary to define
the actual dimensions of the potential environmental impact.
However, the data in Table 13 together with the bioassay results
do indicate that there is reason for concern, especially when the
possible effects of multiple sources are considered. [A similar
study on residential coal combustion indicated that emissions
from an array of 100 houses caused a 30-fold increase in severity
\ 3 ) J *
In addition to source severity it is important to know how many
people around an average residential combustion unit are exposed
to high ground level concentrations. Dispersion equations pre-
dict that the average ground level concentration ("x") varies with
the distance, x, away from a source. For elevated sources, x" is
zero at the source, increases to some maximum value, Ymax' as x
increases, and then falls back to zero as x approaches infinity
Therefore a plot of x/F versus x will have the following
appearance:
DISTANCE FROM SOURCE
The affected population is defined as the number of persons
living in the area around an average source where x/F is greater
than 0.05 or 1.0. The mathematical derivation of the affected
population can be found in Reference 3. The affected population
for wood-fired residential combustion emissions is presented in
Table 14. Emissions from an individual wood-fired combustion
source affect few people, except in the case of POM emissions,
where the maximum affected population is 700 persons for
X/F > 0.05 and 30 persons for x/F > 1-0. The affected popula-
tion varies with population density and will be greater in urban
areas.
Another_measure of the regional (as opposed to local) impact on
the environment is the total annual emissions of each criteria
pollutant. Estimated annual emissions from wood-fired residential
combustion equipment on a state-by-state basis are derived and
tabulated in Appendix D. These were calculated using emission
These factors depend in turn on the type of combustion equip-
ment, the type and condition of wood, and the method of burning.
42
-------
TABLE 14. AFFECTED POPULATION FOR WOOD-FIRED
RESIDENTIAL COMBUSTION
(number of persons)
Affected population
Emission
species
Particulate
Hydrocarbons
POM
Formaldehyde
X/F
Wood
stove
0
0
730
0
> 0.05
Fire-
place
1
10
210
3
X/F
Wood
stove
0
0
30
0
> 1.0
Fire-
place
0
0
9
0
Based on an average population density of 21
persons/km2.
factors and fuel usage estimates. The appendix also shows the
percent contribution of each source type to the total state emis-
sion burden from all stationary sources. In 1976 residential
combustion of wood had emissions exceeding 1% of the total state
emissions for at least one of the criteria pollutants in 49
states, as shown in Table 15.
Total national criteria emissions from this source and corres-
ponding national emission burdens are given in Table 16.
National emissions of criteria pollutants from wood-fired resi-
dential combustion can also be compared to emissions from other
forms of residential combustion (Table 17). The data show that
wood combustion contributes between 0.2% and 95% of the total
from the residential sector.
Another emission species worthy of comparing on a national scale
are POM's, because of their potential carcinogenicity. Table 18
gives a recent inventory of source types that emit more than
1 metric ton/year of POM's, nationwide (44). Data for certain
sources have been revised based on more recent information.
Total POM emissions from residential wood combustion, as deter-
mined in this report, are: primary wood heating, 1,400 metric
tons; auxiliary heating, 2,400 metric tons; and fireplaces, 78
metric tons; for a total of 3,800 metric tons. This represents
a substantial increase over the value reported in Reference 44
of 217 metric tons.
(44) Eimutis, E. C., R. P. Quill, and G. M. Rinaldi. Source
Assessment: Noncriteria Pollutant Emissions (1978 Update),
EPA-600/2-78-044t, U.S. Environmental Protection Agency,
Research Triangle Park, North Carolina, July 1978. 149 pp.
43
-------
TABLE 15. STATE LISTING OF RESIDENTIAL WOOD CRITERIA EMISSIONS
THAT EXCEED 1% OF TOTAL STATE CRITERIA EMISSIONS
Residential wood criteria emissions as a
percent of total state criteria emissions
State
Alabama
Alaska
Arizona
Arkansas
California
Colorado
Connecticut
Delaware
Florida
Georgia
Hawaii
Idaho
Illinois
Indiana
Iowa
Kansas
Kentucky
Louisiana
Maine
Maryland
Massachusetts
Michigan
Minnesota
Mississippi
Missouri
Montana
Nebraska
Nevada
New Hampshire
New Jersey
New Mexico
New York
North Carolina
North Dakota
Ohio
Oklahoma
Oregon
Pennsylvania
Rhode Island
South Carolina
South Dakota
Tennessee
Texas
Utah
Vermont
Virginia
Washington
West Virginia
Wisconsin
Wyoming
Particulates
5.9
1.4
2.7
5.4
1.5
1.4
1.6
11.9
4.0
1.8
1.9
2.8
1.3
25.3
2.1
2.2
8.3
1.0
1.5
3.2
3.3
1.4
2.7
14.8
3.8
Hydrocarbons
1.4
5.0
1.7
3.2
1.5
2.0
2.5
1.0
1.6
2.2
1.1
2.3
1.1
1.2
2.1
7.4
2.3
1.8
2.2
2.8
2.7
1.5
1.9
6.8
1.3
4.6
3.0
2.0
1.0
1.0
1.0
4.2
2.2"
2.2
1.1
4.9
1.7
8.1
2.3
2.5
2.0
1.4
1.2
CO
5.0
9.1
1.7
8.3
1.3
2.0
3.8
1.9
1.8
5.1
4.3
1.2
1.2
1.6
5.7
30.5
2.2
3.6
2.9
4.0
7.0
5.8
2.4
1.8
2.1
28.4
1.5
6.2
4.2
5.0
1.1
1.2
1.5
10.9
2.2
2.0
1.1
1.8
14.7
1.1
1.9
27.5
4.7
6.6
3.1
3.6
1.2
44
-------
TABLE 16. ESTIMATED ANNUAL CRITERIA EMISSIONS AND NATIONAL EMISSION
BURDEN FROM WOOD-FIRED RESIDENTIAL COMBUSTION FOR 1976
Total
annual emissions,
metric tons/yr
Emission
species
Particulate
SOX
NOX
Hydrocarbons
CO
Primary
heating
7,000
1,000
2,500
65,000
930,000
Auxiliary
heating
80,000
1,800
4,300
110,000
2,000,000
Fireplaces
36,000
5,500
200,000
190,000
National emission
% of total
Primary
heating
0.3
<0.01
0.01
0.3
1.0
burden,
of all stationary sources
Auxiliary
heating
0.5
<0.01
0.02
0.4
2.1
Fireplaces
0.2
0.02
0.8
0.2
Ul
TABLE 17. TOTAL ANNUAL EMISSIONS FROM
RESIDENTIAL COMBUSTION SOURCES'
Fuel type
Utility, bottled,
tank, or L.P. gas (2)
Fuel oil, kerosene,
etc. (2)
Coal (3)
Wood
Total
Particulates
47,000(16)
74,000(25)
17,000(6)
160,000(53)
300,000
Emissions, metric
SOX
1,400(0.1)
1,100,000(92)
81,000(7)
2,800(0.2)
1,200,000
tons/yr (percentage of total)
NOX
190,000(63)
89,000(30)
6,900(2)
12,000(4)
300,000
Hydrocarbons
19,000 (4)
23,000(5)
7,600(2)
380,000(88)
430,000
CO
49,000(2)
37,000(1)
72,000(2)
3,100,000(94)
3,300,000
Wood emissions were determined in this report; others are from References 2 and 3.
-------
TABLE 18. LISTING OF SOURCE TYPES THAT EMIT POM'S IN
QUANTITIES GREATER THAN 1 METRIC TON/YEAR (44)
Source typec
Annual POM
emissions,
metric tons
Percent of
total POM
emissions from
all sources
Residential combustion of wood 3,800
Coke manufacturing 632
Residential combustion of
bituminous coal 100C
Dry bottom industrial boilers
firing pulverized bituminous coal 41
Prescribed burning 40
Coal refuse piles 28°
Abandoned mines and outcrops 28C
Asphalt roofing 15
Dry bottom utility boilers firing
pulverized lignite coal 14
Stoker-fired industrial boilers
firing bituminous coal 7
Dry bottom utility boilers firing
pulverized bituminous coal 7
Residential combustion of gas 6
Residential combustion of
distillate oil 5
Asphalt paving - hot mix 4
Wet bottom utility boilers firing
pulverized lignite coal 4
Cyclone-fired utility boilers
firing lignite coal 3
Carbon black -furnace process 3
Stoker-fired utility boilers
firing lignite coal 2
Commercial/institutional combustion
of bituminous coal in stokers 2
Industrial boilers firing gas ' 2
Wet bottom industrial boilers
firing pulverized bituminous coal 1
Wet bottom utility boilers firing
pulverized bituminous coal 1
Cyclone-fired utility boilers
firing bituminous coal 1
Commercial/institutional combustion
of anthracite coal in stokers 1
Commercial/institutional combustion
of gas 1
Total 4,748
80
13
0.9
0.8
0.6
0.6
0.3
0.3
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
Natural and mobile sources are not included in this listing.
b.
Revised data based on this report.
Revised data from Reference 3.
Revised data from Reference 45.
46
-------
Two other recent reports give new data on POM emissions from coal
refuse piles (45) and residential coal combustion (3). Based on
the first report, annual POM emissions from coal refuse piles
amount to only 28 metric tons. Data were not given for abandoned
mines and outcrops, but they are likely to be similar in magni-
tude. Annual POM emissions from residential coal combustion have
been estimated at 100 metric tons. On the basis of these revised
values, residential wood combustion accounts for 80% of national
POM emissions from stationary sources.
(45) Chalekode, P. K., and T. R. Blackwood. Source Assessment:
Coal Refuse Piles, Abandoned Mines and Outcrops, State of
the Art. EPA-600/2-78-004v, U.S. Environmental Protection
Agency, Cincinnati, Ohio, July 1978. 51 pp.
47
-------
SECTION 5
CONTROL TECHNOLOGY
Because of the past decline of solid fuel-fired residential
heating systems, there has been little interest in controlling
emissions from these sources. No add-on emission control devices
are currently on the market; however, any improvement in com-
bustion efficiency will usually result in some improvement of
emission levels.
A study was performed to evaluate emission reduction techniques
in oil- and gas-fired residential furnaces (46), which, in some
areas, can apply to wood-fired units. Table 19 summarizes those
control strategies that may apply to wood-fired equipment.
TABLE 19. COMBUSTION CONTROL STRATEGIES FOR REDUCING AIR
POLLUTANTS FROM RESIDENTIAL HEATING EQUIPMENT (46)
Control strategy
Impacted
pollutant emission
Comments
Excess air level
adjustment
NO
CO
HC
Combustion
chamber design
Service and
maintenance
NO
CO
Hydrocarbons
Smoke/particulate
NO
CO
Hydrocarbons
Smoke/particulate
As excess air is increased, CO, HC, and
smoke pass through a minimum, but NO
passes through a maximum
Optimum pollutant and thermal efficiency
level occurs at a stoichiometric ratio
greater than one
Combustion chamber design affording long
residence time at high temperature
minimizes smoke, participates, CO, HC,
but may increase NO
Refractory-lined chamber affords better
combustion and lower emissions
Equipment state-of-repair very important
for providing breadth for reducing
emissions by other methods
(46) Brown, R. A., C. B. Moyer, and R. J. Schreiber. Feasibility
of a Heat and Emission Loss Prevention System for Area Source
Furnaces. EPA-600/2-76-097, PB 253945, U.S. Environmental
Protection Agency, Research Triangle Park, North Carolina,
April 1976. 187 pp.
48
-------
SECTION 6
GROWTH AND NATURE OF THE SOURCE
Before the twentieth century, coal and wood were the predominant
fuels available for residential heating in the United States.
The last thirty years saw the decline in the use of wood and coal
for residential heating in favor of the cleaner, more efficient
and convenient oil and gas fuels. This substitution took place
at a time when supplies of these new fuels seemed abundant, cheap,
and, to many, inexhaustible. Recent history has shown that not
only were reserves limited, they were grossly undervalued at
current prices. As prices rose rapidly following the Arab oil
embargo of 1973 to more truly reflect the value of energy, the
displaced, unattractive fuels such as wood and coal once again
gained appeal for large numbers of people. Since increased usage
of wood has been easier to accomplish individually, the number of
households supplementing and converting their residential heating
to wood has risen rapidly and dramatically.
PRESENT TECHNOLOGY
The technology of residential wood heating follows a curious
historical phenomenon: knowledge is discovered, used, and lost,
over and over again. The Romans, who were excellent engineers
as shown by their roads and aqueducts which still stand today,
developed heating systems under their tiled floors (using wood
as fuel) that were modern both in concept and execution (47).
With the fall of Rome, wood heating technology disappeared and
did not revive until after the Dark Ages.
The earliest records of cast-iron stoves in Europe date from
around the end of the fifteenth century, when they began to assume
their present form.- They were built with rectangular plates and
the number of plates gave the stove its basic designation.
By colonial times heating had once again become sophisticated;
the Dutch, German, Scandinavian, and French heating units were
impressively efficient and satisfactory. The English, however,
(47) Harrington, G. The Wood-Burning Stove Book. MacMillan Pub-
lishing Company, Inc., New York, New York, 1977. 175 pp.
49
-------
stubbornly stuck to the open fireplace of which they were so
fond, and froze in their frame houses from Vermont to Virginia.
Eventually, thanks to Ben Franklin and Count Rumford, fireplaces
became smaller - and developed smoke shelves, dampers, and other
useful devices (47).
As cities grew and forests receded, it became more difficult
and expensive to feed the enormous appetite of inefficient
colonial fireplaces. By the middle of the eighteenth century
there was a real shortage of wood in Philadelphia, and Ben
Franklin set his inventive genius to the problem. The result
was "The Pennsylvania Fire-place," which he designed in 1744 and
described in a published account, complete with diagrams, measure-
ments, and instructions for building and installing. Made of
cast iron, the stove was designed to fit into an existing fire-
place. It was an open box, joined together with screws and
mortared to seal the seams. The front opening was fitted with
a solid iron plate, or "shutter," which could be moved up and
down to create or control draft while tending the fire, or
closed completely when no fire was wanted. The floor of the
box curved up in front "to keep coals and ashes from coming to
the floor". Although it looks simple at first glance, the con-
struction was fairly complicated. A false back of from two to
four inches was constructed so that "no air may pass into the
chimney but what goes under the false back, and up behind it."
This, to some extent, cut down on drafts, since no air was drawn
into the chimney except through the fire (47).
Few people realize that practically all of the technical features
of Franklin's Pennsylvania stove were copied from earlier inven-
tors. Louis Savat's heat circulating fireplace, installed in the
Louvre around 1600, had a preheated draft which was employed by
Franklin with little change in design. The descending flue was
also copied: smoke rose in front of a hollow metal back, passed
over the top and down the opposite side. Finally, at the same
level as the hearth, the smoke ascended the flue. Savat also
surrounded the grate with 2 metal air chambers which had warm
air outlets above the fire opening. He also supplied the fire
with air from under the floor, thereby reducing room drafts and
improving combustion efficiency (48).
Franklin had spurned the efficient Dutch and German stoves in
favor of an open stove which would allow the fire to be viewed.
By 1786 Franklin had lived abroad for some years and become
acquainted with European heating devices. Although he never lost
(48) Stoner, C. Producing Your Own Power. Rodale Press, Inc.,
Emmaus, Pennsylvania, 1974. 322 pp.
50
-------
his love of an open wood fire, he reluctantly came to the conclu-
sion that it was not the most efficient method of heating. How-
ever, none of the existing heating devices met with his complete
approval, and he set about devising one that would be more satis-
factory. The result was described in considerable detail in a
paper entitled: "Description of a new Stove for burning Pitcoal,
and consuming all its Smoke," which was presented to the American
Philosophical Society on January 28, 1786. Although described as
a stove for pitcoal, it was equally suitable for burning wood,
and Franklin's directions cover both fuels (47).
Although Franklin preferred the open fire to the Dutch or Holland
stoves, he did so in the face of his own common sense. As he says
in another paper (47): "An English farmer in America, who makes
great fires in large open chimneys, needs the constant employment
of one man to cut and haul wood for supplying them; and the draft
of cold air to them is so strong, that the heels of his family
are frozen, while they are scorching their faces, and the room is
never warm, so that little sedentary work can be done by them in
winter. The difference in this article alone of economy shall,
in a course of years, enable the German to buy out the Englishman,
and take possession of his plantation."
The Franklin fire-place proved immensely popular and was soon
being manufactured throughout the colonies. Since Franklin did
not believe in patents, he placed no restriction on his inven-
tions, and the Franklin stove was soon being manufactured both to
his design and with alterations of which he did not approve. His
name was used freely, as it is today, to adorn stoves far removed
from the principles on which his original fireplace stove was
based.
The first Franklin stove of that name was patented in 1816 and
subsequent patents were issued for Slide-Door Franklin Stoves,
Closed Franklin Stoves, Pipe Franklin Stoves, and Fold-Door
Franklin Stoves, among others. It was soon found that the stove,
whatever its variation in design, would heat more effectively if
installed outside - rather than within - the fireplace, with a
pipe leading to the fireplace chimney. This variation is found
to this day, although there are also modern Franklin stoves that
still nestle within the fireplace.
Thus the technology of wood heating today is much the same as it
always has been, and as diverse: efficient freestanding wood
stoves with baffled plate design; fireplaces with heat-circulating
chambers, combustion air brought from outside; wood furnace de-
signs which collect heated air and transport it under floors and
through ducts; parlor stoves, potbelly stoves and box stoves; and
fireplaces which rob a home of heat but afford the charm of an
ornamental fire. The reluctance through the ages to give up the
51
-------
viewing of the open fire demonstrates how much a fire means to
people. Whether it is due to some atavistic need, or just to
aesthetic appreciation, fire has always been a symbol of home.
INDUSTRY TRENDS
Residential heating with wood is increasing rapidly after bottom-
ing out in the early 1970's. In 1850 wood supplied approximately
90% of the energy needs of this nation. Its use declined rapidly
to about 75% by 1875 and 20% by 1900 (49).
Near the turn of the century gas and oil entered the home heating
market. However, these fuels were only available to a small
number of homes near the source. Developments around 1920 made
it possible to deliver large quantities of these fuels to distant
markets and signalled the decline of coal and wood use for home
heating. Wood remained a major home heating fuel in 1940, when
8,000,000 occupied housing units burned wood for primary heating
purposes (50). This was about 23% of the total number of occupied
housing units in the United States. From that point, however,
the decline was rapid. By 1970, housing units burning wood for
heat numbered only about 800,000 units (6) and made up 2% of the
total number of occupied housing units. By 1974, wood-fired
heating dropped by almost 20% to 660,000 housing units (51).
Figure 7 shows the decline in primary wood-fired residential heat-
ing from 1940 to 1974, followed by slight upturn to 1976 when
912,000 housing units were heated primarily with wood (1, 50, 51).
Table 20 gives the distribution of structures built with primary
wood heating by decade (6).
Primary wood heating is predominately a rural phenomenon, and
tends to occur where the seasonal heating load of a residence is
less than 4,000 degree days. The rural nature of heating with
wood is because of easy accessibility to supplies of wood fuel
and short transportation distances. Table "21 illustrates the
distribution of households with primary wood heat by region and
shows that the Southern, mountain states have over 50% of the
(49) Zerbe, J. I. Wood in the Energy Crisis. Forest Farmer,
37 (2):13-15, November-December, 1977.
(50) Statistical Abstracts of the United States 1975. U.S.
Department of Commerce, Washington, D.C., July 1975.
1,050 pp.
(51) Current Housing Reports; Bureau of the Census Final Report
H-150-74; Annual Housing Survey: 1974, Part A; General
Housing Characteristics for the United States and Regions.
U.S. Department of Commerce, Washington, D.C., August 1976.
179 pp.
52
-------
total U.S. population which heat in this manner, followed by the
Pacific northwest region (6). All these areas have an abundance
of forest regions. Table 22 gives the breakdown between urban
and rural use of wood fuel as primary heat and illustrates that
it is predominately the non-farm household in a rural region (1),
20
15
in
=3
O
o
o
•°o
10
HOUSING UNITS WITH PRIMARY
WOOD HEATING
1940
1950
1960
1970
1976
YEAR
Figure 7. Residential wood-firing
heating trends (1, 50, 51)
TABLE 20. STRUCTURES BUILT WITH
PRIMARY WOOD HEATING (6)
Decade
Units
1960 - 1970 92,000
1950 - 1959 103,000
1940 - 1949 126,400
1939 and earlier 472,500
Total 793,900
53
-------
TABLE 21. HOUSING UNITS WITH PRIMARY WOOD
HEAT BY REGION, 1970 (6)
Region
U.S. Total
New England
Middle Atlantic
E. North
W. North
Central
Central
South Atlantic
E. South
W. South
Mountain
Pacific
Atlantic
Atlantic
Number
794
12
12
25
52
254
191
104
41
99
,000
,500
,800
,400
,400
,600
,400
,400
,400
,000
100
1
1
3
6
32
24
13
5
12
.6
.6
.2
.6
.1
.1
.1
.2
.5
Percent
(CT,
(PA,
(WI,
(MO,
(MD,
(KY,
(TX,
(MT,
(CA,
RI,
NY,
MI,
KS,
DE,
TN,
OK,
ID,
OR,
MA
of total
r
VT,
NH, ME)
NJ)
IL
NE
WV
MS
AR
WY
i
r
t
r
i
r
WA)
IN,
IA,
VA,
AL)
LA)
NV,
OH)
MN, SD, ND)
NC, SC, GA)
UT, CO, AZ, NM)
TABLE 22. REGIONAL DISTRIBUTION OF HOUSING UNITS
WITH PRIMARY WOOD HEAT, 1976 (1)
Region
U.S.
Northeast Region
North Central Region
South Region
West Region
Total
912,000
63,000
91,000
584,000
173,000
Urban
92,000
5,000
0
64,000
23,000
Rural
820,000
58,000
91,000
520,000
150,000
Percent
non-farm
73.5
86.2
72.5
70.4
81.3
Percent
farm
26 .5
13.8
27 . 5
29 .6
18.7
The largest increase in wood heating is occurring in supplemental
or auxiliary heating. In spite of high utility bills, most
people are not willing to rely on wood alone for heat. Particu-
larly in Northern New England, recent surveys have shown that
substantial amounts of indigenous fuel wood are being used to
supplement conventional energy sources (oil or electricity) for
residential space heating. These surveys indicate that 6.5%,
16.5%, and 21.8% of the heating loads per residence were main-
tained by wood combustion for the winters of 1975-76, 1976-77
and 1977-78, respectively (33). '
Statistics on the shipment of wood-fired heating equipment indi-
cate a sudden demand for stove type heating devices, starting
ro?U™1973 When the retail Price index of #2 fuel oil jumped
b«* (50). in 1972, total stove type residential heating equip-
ment shipped was about 197,000 units. In 1975, the number had
54
-------
jumped to about 407,000 units (52-54). Figure 8 shows the trends
in shipments for both airtight and nonairtight wood heating stoves
(52-63) .
(52) Current Industrial Reports, Heating and Cooking Equipment.
Bureau of the Census, MA-34N(72)-1, U.S. Department of
Commerce, Washington, D.C., November 1973. 9 pp.
(53) Current Industrial Reports, Selected Heating Equipment.
Bureau of the Census MA-34N(75)-1, U.S. Department of
Commerce, Washington, D.C., July 1976. 6 pp.
(54) Current Industrial Reports, Air Conditioning and Refrigera-
tion Equipment Including Warm Air Furnaces. Bureau of the
Census, MA-35M(75)-1, U.S. Department of Commerce,
Washington, D.C., October 1976. 14 pp.
(55) Current Industrial Reports, Heating and Cooking Equipment.
Bureau of the Census M34N(60)-13, U.S. Department of
Commerce, Washington, D.C., August 1961. 7 pp.
(56) Current Industrial Reports, Heating and Cooking Equipment.
Bureau of the Census M34N(64)-13, U.S. Department of
Commerce, Washington, D. C., July 1966. 9 pp.
(57) Current Industrial Reports, Heating and Cooking Equipment.
Bureau of the Census M34N(65)-13, U.S. Department of
Commerce, Washington, D.C., July 1966. 9 pp.
(58) Current Industrial Reports, Heating and Cooking Equipment.
Bureau of the Census M34N(66)-13, U.S. Department of
Commerce, Washington, D.C., February 1968. 9 pp.
(59) Current Industrial Reports, Heating and Cooking Equipment.
Bureau of the Census M34N(67)-13, U.S. Department of
Commerce, Washington, D.C., January, 1969. 7 pp.
(60) Current Industrial Reports, Heating and Cooking Equipment.
Bureau of the Census M34N(69)-13, U.S. Department of
Commerce, Washington, D.C., February 1971. 7 pp.
(61) Current Industrial Reports, Heating and Cooking Equipment.
Bureau of the Census M34N(70)-13, U.S. Department of
Commerce, Washington, D.C., December 1972. 9 pp.
(62) Current Industrial Reports, Selected Heating Equipment.
Bureau of the Census MA-34N(76)-1, U.S. Department of
Commerce, Washington, D. C., August 1977. 7 pp.
(63) Current Industrial Reports, Selected Heating Equipment.
Bureau of the Census MA-34N(77)-1, U.S. Department of
Commerce, Washington, D.C., August 1978. 7 pp.
55
-------
400
350
300
250
200
150
AIRTIGHT
NON-AIRTIGHT
° 58 60 62 64 66 68 70 72 74 76 78 ou
YEAR
Figure 8. United States production of
wood burning stoves (52-63).
The residential use of fireplaces for wood burning is also in-
creasing. Figure 9 illustrates that 36% of new houses completed
in 1971 were constructed with one or more fireplaces; this number
increased to 58% in 1976, of which 5% had more than one fireplace
(64). Fireplaces in American homes are used primarily for aes-
thetic purposes. Table 23 illustrates the percent distribution of
fireplaces in new housing by sales price o'f the housing unit (50).
Primary residential wood combustion accounts for 5% of total
timber usage in the United States. Total timber production in
1977 was estimated at 3.2 x 108 m3, roundwood equivalent, or
2.5 x 108 m3 of wood allowing for the packing factor (65). Based
on a typical density of 400 kg/m3 (at 12% moisture), the total
production level was approximately 100 x 106 metric tons. This
can be compared with the estimated consumption figures for pri-
mary residential wood combustion in 1976 of 5 x 106 metric tons.
(64) Construction Report; Bureau of the Census-Series C25;
Characteristics of New Housing: 1976. U.S. Department of
Commerce, Washington, D.C., July 1977. 77 pp.
(65) Statistical Abstracts of the United States 1978. U.S.
Department of Commerce, Washington, D.C., September 1978.
1,081 pp.
56
-------
These data indicate that increased consumption of wood by the
residential sector could have a substantial impact on forest
utilization. By way of example, an increase in the percent of
homes in the U.S. heated primarily by wood from 1% to 10% would
mean that timber harvesting would have to be increased by 45%, if
other wood demand areas remained unchanged.
Houses With One Fireplace or More
36% 38%
North-
east
North
Centr^
47% 44% 47% 48% 45% 53%
100
0
100
50
0
100
0
100
S°Uth »{ 29% 32% ™
0
,,„
33% 34% 2Z*
45% 48% 50%
51%
58%
56%
63% 66% 72*
100
West so I 46% 47%
0-
1971 1972 1973 1974 1975 1976
Figure 9. New housing completed, 1971-1976 (64).
TABLE 23. PERCENT DISTRIBUTION OF FIREPLACES IN
NEW HOUSING BY SALES PRICE IN 1976 (64).
Sale price of house
Number of
fireplaces
No fireplace
1 fireplace
2 fireplaces
Under
$30,000
87
13
$30,000
to
$39,999
55
44
$40,000
to
$49,999
32
64
$50,000
to
$59,999
20
75
$60,000
to
$69,999
12
81
$70,000
and
over
8
77
Total
39
57
or more
15
57
-------
When the pioneers began to clear land in the New World for their
homes, farms, and cities, they marveled at the apparently endless
forests. By the eighteenth century, Ben Franklin was turning his
inventive skills to a stove that would help ease the shortage of
wood around Philadelphia. Today, two centuries later, the United
States still has almost 75% as much forest land as existed in the
time of the pioneers - 754 million acres, or one third of the
United States, is still forest. Of that acreage, 254 million
acres have been set apart for parks and recreation areas and can-
not be commercially cut for lumber, but they are still available
to those gathering wood by permit. The remaining 500 million
acres are classified as commercial forest land, i.e., forests
which may be harvested. In the state of Maine, for example,
90% of the land is forest but Maine is also the site of some of
the largest paper manufacturers in the country, and 86% of the
forest land is commercial acreage (47).
From commercial forest land comes plywood, paper, wood pulp,
air^er; °^6? *°°d Products' supporting some of the
and most essential industries in the country; yet even
r00d 1S gr°Wn thSn harvest^. This is due largely to
where woo hmanagemSnt bY industrial users. In most instances
where wood has proven an economically desirable product, forest
productivity has been increased. rorest
oarat in,re^fdential "°°d heating are dependent on com-
parative costs of other residential heating fuels - gas, oil and
electricity. Particularly fuel oil and electricity appear cur-
fh^ "nattractive a* residential fuels, and states whiS Save
reason, ??? Ce 0n.Jhese fuels coupled with abundant forest
regions will see residents supplementing with or switching to
wood-fired equipment. Table 24 notes several key states 2ith a
large proportion of households dependent on fuel oil or electri-
city as primary heat (22). If natural gas prices were to rise
rapidly as did fuel oil many other states would expedience llrae
increases in supplemental heating by wood. experience large
Also, should tax credits be provided to U.S. taxpayers under the
P"
and hi treatment now afforded to wind
and geothermal energy equipment, a sharp increase in wood-fired
equipment usage might follow. Most solar and wind energy equip-
h;StinaeisUa nS0nd.th; P°cketbook* °f »ost Americans ; ^ood P
neating is a necessity for many rural poor. Yet, six million
0n?tyPe of energ? tax credit in ?978 - some
* °
(66) Mueller, S. Federal Tax Credits: The Ultimate "Accounting"
for Solar Sales. Solar Heating & Cooling, 4(6):7, 1979.
58
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TABLE 24. STATES WHICH DEPEND HIGHLY ON FUEL AND/OR
ELECTRICITY AS PRIMARY HEAT (1970) (22)
Percent housing units
which heat primarily with;
State
Alabama
Arkansas
Florida
Georgia
Indiana
Iowa
Maine
Maryland
Massachusetts
Mississippi
Missouri
New Hampshire
New York
North Carolina
Oregon
Pennsylvania
Rhode Island
South Carolina
Tennessee
Vermont
Virginia
Washington
Wisconsin
Wood
5.4
8.2
4.9
2.1
8.4
2.5
4.7
6.3
4.7
1.4
3.3
1.6
Fuel
oil
29.2
26.9
20.7
91.8
43.8
65.8
80.5
56.8
61.9
37.8
35.0
69.7
44.6
80.4
48.6
40.8
39.2
Bottled
Electricity gas
21.1
32.3
10.7 18.3
12.5
26.6
16.7
10.8
29.8
40.4
30.4
As long as the governments and information media convey the idea
that saving on oil imports is a national priority, households
will add or switch to wood-burning equipment, often at a substan-
tial cost; so that they can voluntarily contribute to saving on
our massive national oil import bill and reduce their own heating
bills.
59
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60
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61
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23. 1973 NEDS Fuel Use Report. EPA-450/2-76-004 (PB 253908)
U.S. Environmental Protection Agency, Research Triangle
Park, North Carolina, April 1976. 124 pp.
24. Guide for Compiling a Comprehensive Emission Inventory
(Revised). Publication No. APTD-1135, U.S. Environmental
Protection Agency, Research Triangle Park, North Carolina,
March 1973. 204 pp.
25. Myers, J. P., and F. Benesh. Methodology for Countywide
Estimation of Coal, Gas, and Organic Solvent Consumption.
EPA-450/3-75-086, U.S. Environmental Protection Agency,
Research Triangle Park, North Carolina, December 1975.
152 pp.
26. Vermont Surveys Wood Stove Use. Wood'N Energy, 3(2):8,
September 1978.
27. Turner, A. Personal communication. Vermont Energy Office,
Montpelier, Vermont, October 1979.
28. Shapiro, A. Personal communication. Wood Energy Research
Corporation, Camden, Maine, October 1979.
29. Preliminary Characterization of Emissions from Wood-fired
Residential Combustion Equipment. EPA-600/7-80-040, U.S.
Environmental Protection Agency, Research Triangle Park,
North Carolina, March 1980. 153 pp.
30. Clayton, L., G. Karels, C. Ong, and T^ Ping. Emissions from
Residential Type Fireplaces. Source Tests 24C67, 26C, 29C67,
40C67, 41C67, 65C67, and 66C67, Bay Area Air Pollution
Control District, San Francisco, California, January 31,
1968. 6 pp.
31. Butcher, S. S., and D. I. Buckley. A Preliminary Study of
Particulate Emissions from Small Wood Stoves. Journal of
the Air Pollution Control Association, 27(4):346-347,
April 1977.
32. Source Testing for Fireplaces, Stoves, and Restaurant Grills
in Vail, Colorado. Contract 68-01-1999, U.S. Environmental
Protection Agency, Region VIII, Denver, Colorado. (Draft
document submitted to the EPA by PEDCo-Environmental, Inc.,
December 1977.) 29 pp.
62
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33. Butcher, S. S., and E. M. Sorenson. A Study of Wood Stove
Particulate Emissions. Journal of the Air Pollution Control
Association, 29 (7) :724-728, 1979.
34. Environmental Protection Agency - Part II - Standards of
Performance for New Stationary Sources - Revision to Refer-
ence Method 1-8. Method 5 - Determination of Particulate
Emissions from Stationary Sources. Federal Register,
42 (160):41776-41782, August 1977.
35. Shriner, D. A., and G. S. Henderson. Sulfur Distribution
and Cycling in Dedicuous Forest Watershed. Journal of Envi-
ronmental Quality, 7 (3):392-397, 1978.
36. Oglesby, H. S., and R. 0. Blosser. Information on the Sul-
fur Content of Bark and Its Contributions to S02 Emissions
When Burned as Fuel. Paper 79-6.2, Presented at the 72nd
Annual Meeting of the Air Pollution Control Association,
Cincinnati, Ohio, June 24-29, 1979.
37. Level I Bioassays on Thirty-two Residential Wood Combustion
Residue Samples. Contract 68-02-2681, U.S. Environmental
Protection Agency, Research Triangle Park, North Carolina.
(Final report submitted to the EPA by Litton Bionetics, Inc.,
November 1979). 211 pp.
38. Turner, D. B. Workbook of Atmospheric Dispersion Estimates.
Public Health Service Publication No. 999-AP-26, U.S.
Department of Health, Education, and Welfare, Cincinnati,
Ohio, May 1970. 84 pp.
39. TLVs® Threshold Limit Values of Chemical Substances and
Physical Agents in the Workroom Environment with Intended
Changes for 1976. American Conference of Governmental
Industrial Hygienists, Cincinnati, Ohio, 1976. 94 pp.
40. Federal Register, 36:22384, November 25, 1971.
41. Federal Register, 43:46258, October 5, 1978.
42. Federal Register, 44:8220, February 8, 1979.
43. Handy, R. and A. Schindler. Estimation of Permissible
Concentrations of Pollutants for Continuous Exposure.
EPA-600/2-76-155, U.S. Environmental Protection Agency,
Research Triangle Park, North Carolina, June 1976. 148 pp.
44. Eimutis, E. C., R. P. Quill, and G. M. Rinaldi. Source
Assessment: Noncriteria Pollutant Emissions (1978 Update).
EPA-600/2-78-004t, U.S. Environmental Protection Agency,
Research Triangle Park, North Carolina, July 1978. 149 pp.
63
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45. Chalekode, P. K., and T. R. Blackwood. Source Assessment:
Coal Refuse Piles, Abandoned Mines and Outcrops, State of
the Art. EPA-600/2-78-004v, U.S. Environmental Protection
Agency, Cincinnati, Ohio. July 1978. 51 pp.
46. Brown, R. A., C. B. Moyer, and R. J. Schreiber. Feasibility
of a Heat and Emission Loss Prevention System for Area
Source Furnaces. EPA-600/2-76-097, PB 253945, U.S. Environ-
mental Protection Agency, Research Triangle Park, North
Carolina, April 1976. 187 pp.
47. Harrington, G. The Wood-Burning Stove Book. MacMillan
Publishing Company, Inc., New York, New York, 1977. 175 pp.
48. Stoner, C. Producing Your Own Power. Rodale Press, Inc.,
Emmaus, Pennsylvania, 1974. 322 pp.
49. Zerbe, J. I. Wood in the Energy Crisis. Forest Farmer,
37(2):13-15, November-December, 1977.
50. Statistical Abstracts of the United States 1975. U.S.
Department of Commerce, Washington, D.C., July 1975.
1,050 pp.
51. Current Housing Reports; Bureau of the Census Final Report
H-150-74; Annual Housing Survey: 1974, Part A; General
Housing Characteristics for the United States and Regions.
U.S. Department of Commerce, Washington, D.C., August 1976.
179 pp.
52. Current Industrial Reports, Heating and Cooking Equipment.
Bureau of the Census, MA-34N(72)-1, U.S. Department of
Commerce, Washington, D.C., November 1973. 9 pp.
53. Current Industrial Reports, Selected Heating Equipment.
Bureau of the Census MA-34N(75)-1, U.S. Department of Com-
merce, Washington, D.C., July 1976. 6 pp.
54. Current Industrial Reports, Air Conditioning and Refrigera-
tion Equipment Including Warm Air Furnaces. Bureau of the
Census, MA-35M(75)-1, U.S. Department of Commerce, Washing-
ton, D.C., October 1976. 14 pp.
55. Current Industrial Reports, Heating and Cooking Equipment.
Bureau of the Census M34N(60)-13, U.S. Department of
Commerce, Washington, D.C., August 1961. 7 pp.
56. Current Industrial Reports, Heating and Cooking Equipment.
Bureau of the Census M34N(64)-13, U.S. Department of Com-
merce, Washington, D.C., July 1966. 9 pp.
64
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57. Current Industrial Reports, Heating and Cooking Equipment.
Bureau of the Census M34N(65)-13, U.S. Department of Com-
merce, Washington, D.C., July 1966. 9 pp.
58. Current Industrial Reports, Heating and Cooking Equipment,
Bureau of the Census M34N(66)-13, U.S. Department of Com-
merce, Washington, D.C., February 1968. 9 pp.
59. Current Industrial Reports, Heating and Cooking Equipment.
Bureau of the Census M34N(67)-13, U.S. Department of
Commerce, Washington, D.C., January, 1969. 7 pp.
60. Current Industrial Reports, Heating and Cooking Equipment.
Bureau of the Census M34N(69)-13, U.S. Department of Com-
merce, Washington, D.C., February 1971. 7 pp.
61. Current Industrial Reports, Heating and Cooking Equipment.
Bureau of the Census M34N(70)-13, U.S. Department of Com-
merce, Washington, D.C., December 1972. 9 pp.
62. Current Industrial Reports, Selected Heating Equipment.
Bureau of the Census MA-34N(76)-1, U.S. Department of
Commerce, Washington, D.C., August 1977. 7 pp.
63. Current Industrial Reports, Selected Heating Equipment.
Bureau of The Census MA-34N(77)-1, U.S. Department of
Commerce, Washington, D.C., August 1978. 7 pp.
64. Construction Report; Bureau of the Census-Series C25;
Characteristics of New Housing: 1976. U.S. Department of
Commerce, Washington, D.C., July 1977. 77 pp.
65. Statistical Abstracts of the United States 1978. U.S.
Department of Commerce, Washington, D.C., September 1978.
1,081 pp.
66. Mueller, S. Federal Tax Credits: The Ultimate "Accounting"
for Solar Sales. Solar Heating & Cooling, 4(6):7, 1979.
67. Jjzftul: A Resource Book on the Art of Heating with Wood
(1978 Revision). Kristia Associates, Portland, Maine, 1978.
64 pp.
68. Project Plan: North Georgia Wood Heater Demonstration
Project. Preliminary Report. Tennessee Valley Authority,
Chattanooga, Tennessee, October 1978. 18 pp.
65
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69. 1972 National Emissions Report. EPA 450/2-74-012, U.S.
Environmental Protection Agency, Research Triangle Park,
North Carolina, June 1974. 422 pp.
70. Standard for Metric Practice. ANSI/ASTM Designation
E 380-76e, IEEE Std 268-1976, American Society for Testing
and Materials, Philadelphia, Pennsylvania, February 1976.
37 pp.
66
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APPENDIX A
ESTIMATION OF THE SOURCE POPULATION AND FUEL CONSUMPTION
The most recent published data on the population of wood-fired
heating equipment is the 1976 Annual Housing Survey published
by the Bureau of Census. However, this report is based on data
collected from a sample population; it lacks the detail necessary
to adequately characterize the whole population. The 1970 Census
of Housing surveyed the total population and is much more detailed
than the 1976 Housing Survey. To obtain a better estimate of the
1976 population this appendix employs certain relationships and
trends observed in various tables from both surveys.
Residential combustion of wood was divided into three categories:
1) primary heating, done primarily with wood-fired furnaces and
airtight stoves; 2) auxiliary heating, done with airtight stoves,
nonairtight wood stoves (Franklin stoves, box stoves, laundry
stoves, parlor stoves), and converted fireplace stoves; and
3) fireplaces, from the heat-circulating type with glass doors
to those used for ornamental or aesthetic wood burning.
Table A-l shows the number of housing units burning wood as their
primary source of heat in 1970 and 1976 by region. The table
also gives the percent growth from 1970 to 1976. It is assumed
that each housing unit noted contains one wood-burning device.
Although some multi-unit structures may contain only one heating
device, some single unit structures will contain more than one.
Thus, possible errors in determining the population of primary
heating equipment will tend to cancel out.
TABLE A-l.
NUMBER OF HOUSING UNITS BURNING WOOD FOR
PRIMARY HEATING, 1970 and 1976 (1, 21)
Number of
housing units
Percentage
increase from
Percentage of
national units
Region
North East
North Central
South
West
1970
25,000
78,000
550,000
140,000
1976
63,000
91,000
584,000
173,000
1970 to 1976
152
16.7
6.2
23.6
1970
3
10
69
18
1976
7
10
64
19
United States 794,000 912,000
14.9
67
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Table A-2 lists the population of housing units burning wood by
state as obtained from the 1970 Census of Housing. The estimated
1976 population is obtained by applying the regional growth per-
centages from Table A-l to the 1970 state-by-state data. Wood
consumption for primary heating was calculated based on the
annual heating degree-days in each state and a wood consumption
rate of 1.54 kg/degree-day per dwelling unit (23). Results are
given in Table A-3.
Estimates of the number of fireplaces burning wood are not avail-
able from published surveys. However, a report on the number of
new housing units constructed gives the percentage which contain
one or more fireplaces (58). Using 1971 as a baseline (since the
percentage with fireplaces is increasing), an estimate of the
percentage of homes by region was obtained and applied to all
housing units in each region. These figures are: South region -
29% of all housing units have one or more fireplaces; West region
- 46%; North East region - 47%; and North Central region - 33%.
An estimate of the amount of wood consumed in fireplaces was con-
servatively assumed to equal the average U.S. wood fuel consump-
tion per capita (65) (2.9 ft3), in lieu of any published estimate.
At 2.9 persons per household, the average wood fuel consumption
in fireplaces becomes 98.3 kg per housing unit. This estimate
should balance wood consumption between the households with heat-
circulating fireplaces who burn wood often during cooler autumn
and spring evenings and those households that burn wood rarely
for aesthetic reasons. Many households never utilize their fire-
place, realizing that it may rob the house of heated air and due
to unavailability of sources of firewood. The estimated amount
of wood consumed in fireplaces on a state-by-state basis is given
in Table A-4.
The largest area of uncertainty and greatest lack of published
data are in the category of auxiliary heating by wood stoves.
Increasing numbers of homeowners and renters are installing and
using wood stoves as an alternative to the high price and uncer-
tain availability of fuel oil. Homes with electric resistance
heating are also turning to wood as a supplement in order to
hold down heating costs. The best source of information from
which to estimate the number of wood stoves are the U.S. Bureau
of Census Current Industrial Reports (52-62). Taking the last
fifteen years' output (1961-1976) as an estimate of the number of
wood stoves which are in use shows that 2,300,000 airtight-type
stoves were manufactured and shipped, and 4,300,000 nonairtight
stoves (includes kitchen heaters, caboose, woodbox, laundry
stoves) were shipped. It was also assumed that an additional
15% over the total number of U.S. made stoves were imported. It
is known that wood stoves are manufactured in Taiwan, Korea,
68
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TABLE A-2. NUMBER OF HOUSING UNITS BURNING WOOD FOR
PRIMARY HEATING BY STATE, 1970 AND 1976
(1, 21)
: "Estimated number
Number of housing of housing units
units burning burning wood for
wood for primary primary heating,
State heating, 1970 1976
Alabama
Alaska
Arizona
Arkansas
California
Colorado
Connecticut
Delaware
Florida
Georgia
Hawaii
Idaho
Illinois
Indiana
Iowa
Kansas
Kentucky
Louisiana
Maine
Maryland
Massachusetts
Michigan
Minnesota
Mississippi
Missouri
Montana
Nebraska
Nevada
New Hampshire
New Jersey
New Mexico
New York
North Carolina
North Dakota
Ohio
Oklahoma
Oregon
Pennsylvania
Rhode Island
South Carolina
South Dakota
Tennessee
Texas
Utah
Vermont
Virginia
Washington
West Virginia
Wisconsin
Wyoming
55,800
2,900
12,300
50,400
43,700
1,600
900
700
23,700
66,600
2,100
5,400
2,700
5,800
1,400
2,900
25,100
16,000
6,300
6,100
1,200
5,400
6,600
53,400
38,700
4,100
1,100
1,300
2,000
1,000
15,000
6,300
61,200
200
4,600
12,900
32,300
5,600
200
46,000
1,500
57,000
25,000
1,000
1,900
45,400
18,000
4,800
6,800
700
59,200
3,600
15,200
53,500
54,000
2,000
2,300
700
25,200
70,700
2,600
6,700
3,100
6,800
1,600
3,400
26,700
17,000
15,900
6,500
3,000
6,300
7,700
56,700
45,100
5,100
1,300
1,600
5,000
2,500
18,500
15,900
65,000
200
5,400
13,700
39,900
14,100
500
48,800
1,700
60,500
26,500
1,200
2,700
48,200
22,200
5,100
7,900
900
United States 794,000 912,000
69
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TABLE A-3.
ESTIMATED ANNUAL HEATING DEGREE-DAYS AND
WOOD CONSUMPTION FOR PRIMARY HEATING BY
STATE, 1976
State
Degree daysa
Wood consumed for
primary heating,
metric tons
Alabama
Alaska
Arizona
Arkansas
California
Colorado
Connecticut
Delaware
Florida
Georgia
Hawaii
Idaho
Illinois
Indiana
Iowa
Kansas
Kentucky
Louisiana
Maine
Maryland
Massachusetts
Michigan
Minnesota
Mississippi
Missouri
Montana
Nebraska
Nevada
New Hampshire
New Jersey
New Mexico
New York
North Carolina
North Dakota
Ohio
Oklahoma
Oregon
Pennsylvania
Rhode Island
South Carolina
South Dakota
Tennessee
Texas
Utah
Vermont
Virginia
Washington
West Virginia
Wisconsin
Wyoming
1,684
9,007
1,552
3,354
2,331
6,016
6,350
4,940
767
3,095
0
5,833
6,113
5,577
6,710
4,687
4,640
1,465
7,498
4,729
5,621
7,806
9,034
2,300
4,956
7,652
6,049
6,022
7,360
4,946
4,292
6,221
3,366
9,044
5,642
3,695
4,792
5,398
5,972
2,598
7,838
3,462
2,134
5,983
7,876
3,714
6,010
4,590
7,444
7,255
150,000
50,000
36,000
280,000
190,000
18,000
22,000
5,000
30,000
340,000
1,000
60,000
29,000
58,000
16,000
24,000
190,000
38,000
180,000
47,000
26,000
76,000
110,000
200,000
330,000
60,000
12,000
15,000
57,000
19,000
120,000
150,000
340,000
3,000
47,000
78,000
290,000
130,000
5,000
190,000
20,000
320,000
87,000
11,000
33,000
280,000
210,000
36,000
91,000
10,000
Total
5,100,000
Data in Reference 55 is given for major cities in
each state. For this study, it was assumed that
these numbers approximated state averages.
Assumed 200 degree days.
70
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TABLE A-4.
ESTIMATED WOOD CONSUMPTION IN FIREPLACES AND IN
AUXILIARY HEATING BY WOOD STOVES BY STATE, 1976
State
Alabama
Alaska
Arizona
Arkansas
California
Colorado
Connecticut
Delaware
Florida
Georgia
Hawaii
Idaho
Illinois
Indiana
Iowa
Kansas
Kentucky
Louisiana
Maine
Maryland
Massachusetts
Michigan
Minnisota
Mississippi
Missouri
Montana
Nebraska
Nevada
New Hampshire
New Jersey
New Mexico
New York
North Carolina
North Dakota
Ohio
Oklahoma
Oregon
Pennsylvania
Rhode Island
South Carolina
South Dakota
Tennessee
Texas
Utah
Vermont
Virginia
Washington
West Virginia
Wisconsin
Wyoming
Total
Estimated number
of homes with
fireplaces
346,800
53,800
346,400
211,400
3,610,100
410,300
493,000
55,700
896,700
470,100
119,600
126,000
1,258,600
589,700
329,700
269,300
329,700
356,400
167,300
395,300
923,100
985,100
437,900
214,300
556,400
120,100
178,200
100,300
129,700
1,155,300
702,100
2,993,000
519,700
69,600
1,186,000
288,300
387,800
1,900,700
149,900
259,800
75,200
413,000
1,215,700
170,200
73,800
482,900
594,800
180,700
504,600
61,200
27,865,300
Wood consumed in
fireplaces,
metric tons
34,000
5,000
34,000
21,000
360,000
40,000
49,000
5,000
88,200
46,000
12,000
12,000
120,000
58,000
32,000
26,000
32,000
35,000
16,000
39,000
91,000
97,000
43,000
21,000
55,000
12,000
18,000
10,000
13,000
114,000
69,000
290,000
51,000
7,000
120,000
28,000
38,000
190,000
15,000
26,000
7,000
41,000
120,000
18,000
7,000
48,000
58,000
18,000
50,000
6,000
2,700,000
Estimated number
of homes with
auxiliary heat
by wood stove
239,200
10,700
69,100
66,900
719,800
81,800
96,200
17,600
283,600
148,700
23,800
25,100
349,800
163,900
91,600
74,800
227,400
112,100
117,500
125,000
180,100
273,800
121,700
147,800
154,600
23,900
49,500
20,000
91,100
225,500
34,000
584,100
164,400
19,400
329,600
91,200
. 168,600
370,900
29,300
82,200
20,900
284,800
384,500
33,900
51,800
152,700
258,600
57,100
140,200
12,200
7,603,000
Wood consumed in
auxiliary wood
stoves, metric
tons (cords)3
360,000 (1)
32,000 (2)
26,000 (k)
100,000 (1)
270,000 (k)
61,000 (h)
140,000 (1)
13,000 (k)
210,000 (%}
220,000 (1)
9,000 (%)
19,000 (h)
260,000 (h)
120,000 (%)
68,000 (h]
56,000 (h)
170,000 (h)
84,000 (h.}
440,000 (2.5)
94,000 (h)
270,000 (1)
410,000 (1)
360,000 (2)
110,000 Cs)
230,000 (1)
18,000 (%)
38,000 (%)
' ; , (
8,000 (%)
340,000 (2.5)
170,000 (h)
25,000 (h)
870,000 (1)
120,000 Cs)
14,000 (%)
250,000 (%)
34,000 (%)
250,000 (1)
280,000 (%)
22,000 (%)
62,000 (%}
16,000 (%)
850,000 (2)
290,000 (%)
25,000 (%)
190,000 (2.5)
110,000 (%)
390,000 (1)
43,000 (%)
210,000 (1)
9,000 (h)
8,500,000
Number in parentheses is estimated number of cords used per household.
71
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Canada, South America, as well as several European countries (67).
These additional 990,000 stoves give a U.S. total wood stove
population of 7,600,000 stoves used for auxiliary heating.
The states in which wood heating has become prevalent are assumed
to have higher percentages of households which utilize wood stoves
as auxiliary heating. It was assumed that 33% of the households
in northern New England (VT, NH, and ME) have auxiliary wood
stoves, 20% of the households in the East South Central region
(KY, AL, TN, and MS) and 20% of the households in Washington and
Oregon. That leaves 6,042,300 stoves for the remaining 65,876,000
households of the U.S., or 9.17% of all households for all the
other states. Average wood fuel usage for auxiliary wood stoves
in each state was estimated based on average state degree days
and forest availability, and ranged from one-fourth of a cord to
2.5 cords (374 kg to 3,740 kg). The estimated number of housing
units with auxiliary heat by wood stoves and auxiliary wood fuel
consumption by state are given in Table A-4.
(67) Jjrftul: A Resource Book on the Art of Heating with Wood
(1978 Revision). Kristia Associates, Portland, Maine, 1978
64 pp.
72
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APPENDIX B
DETERMINATION OF THE REPRESENTATIVE SOURCE
Due to the heterogeneous nature of residential wood combustion,
two representative sources were chosen for source severity calcu-
lations: 1) a wood-burning stove used for primary or auxiliary
heating, and 2) a fireplace used for aesthetic burning.
Data from the 1976 Housing Survey indicate that the representa-
tive wood stove is located in the South region of the U.S., with-
in a rural area in a non-farm dwelling, as shown in Table B-l and
Table B-2. Within the South region the wooded hills and mount-
ains comprising Appalachia are the location of most wood-derived
home heating.
TABLE B-l. DISTRIBUTION BY REGION OF HOUSEHOLDS
WHICH HEAT PRIMARILY WITH WOOD (1)
Region
South
Northeast
North Central
West
1976, a
%
64.0
6.9
10.0
19.0
1970, a
%
69.3
3.1
9.8
17.6
Numbers do not add up to 100% due
to rounding.
TABLE B-2. DISTRIBUTION WITHIN REGIONS OF HOUSEHOLDS
WHICH HEAT PRIMARILY WITH WOOD, 1976 (1)
Urban, Rural, %~~
Region % Farm Non-farm
South 11.0 26.3 62.7
Northeast 7.9 12.7 79.4
North Central 0 27.5 72.5
West 13.3 16.2 70.5
U.S. 10.1 23.8 66.1
73
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Excellent data is available from the Tennessee Valley Authority
(TVA) concerning individual household wood stove usage rates in
the South (68). In the fall of 1977 TVA embarked on a project
to study the practicality of wood-burning stoves as an alternate
source of residential heating to electricity. Benefits to the
TVA were expected to be energy conservation by households and
reduction in peak hourly loads. Ninety (90) households partici-
pated in the study, with 59 installing Ashley stoves and 31
installing Riteway stoves. In return for a reduced cost from
the manufacturer they agreed to provide TVA a monthly report for
two years on the stove's operation and their past and present
electric utility bills. Data from 36 households for the months
of January and February 1978 are presented in Tables B-3 and B-4,
respectively (68).
The average household during the most severe heating load months
(January and February) loaded the stove 3.69 times per day with
dry hardwood. At an average hardwood density of 640.6 kg/m3,
each household averaged 0.113 m3 (4.0 ft3) of wood burned, or
3 kg/hr.
The average fireplace burning rate was determined by averaging
the data from all published source tests on fireplaces (9, 29,
30 and 32), giving a value of 8.5 kg/hr.
Emission heights of residential combustion equipment will vary
with building height and placement within a building. Chimney
heights for a total of 38 wood-burning fireplaces average 4.3m
above the firebox (9, 29). Assuming the top of the firebox to
be about 0.9 m above the floor and these fireplaces to be all at
ground level, the average emission height is 5.2 m above ground.
This figure will be used for all wood-burning equipment.
To determine the affected population for a pollutant from an
emission source, the population density around the source must
be known. For the representative wood stove emission source the
average population density of the non-urban counties of Tennessee
will be assumed in this case, or 21 persons/km2 (55 persons/mi2).
(68) Project Plan: North Georgia Wood Heater Demonstration
Project. Preliminary Report. Tennessee Valley Authority,
Chattanooga, Tennessee, October 1978. 18 pp.
74
-------
TABLE B-3. TVA WOOD FOR ENERGY HEATING DEMONSTRATION - JANUARY 1978 DATA (68)
Ul
ID
number
•0007
•0908
•0010
•0012
• 0011
•0922
•0932
•0931
•003*
•0034
•0037
-00*4
•0045
•0051
•0052
•0053
•0055
•0051
•9J63
• 0065
•0066
•0077
•0971
•0101
•010*
-0111
•0112
•0114
-0115
•0116
•0119
•0123
•012*
•0125
•0126
.0127
Where wood
obtained, January
IVA LAND
OTHER PUILIC
OTHER PUILIC
OTHER PUILIC
IVA LAND
TVA LAND
YOUR LAND
OTHER PUBLIC
IVA LAND
OTHER PUILIC
YOUR LAND
OTHER PUILIC
OTHER PRIVATE
YOUR LAND
TOUR LAND
YOUR LAND
TOUR LAND
OTHER PRIVATE
TOUR LAND
DO NOT KUDU
YOUR LAND
DO NOT K«D*
TVA LAND
OTHER PUILIC
TVA LAND
JTHER PRIVATE
TOUR LAND
TOUR LAND
OTHER PRIVATE
TOUR LAND
OTHER PUILIC
OTHER PRIVATE
3THER PUILIC
OTHER PRIVATE
OTHER PRIVATE
YOUR LAND
Cost
How wood of
obtained, January wood, S
NOT PURCHASED
NOT PURCHASED
NOT PURCHASED
NOT PURCHASED
NOT PURCHASED
NOT PURCHASED
NOT PURCHASED
NOT PURCHASED
NOT PURCHASED
NOT PURCHASED
NOT PURCHASED
NOT PURCHASED
PURCHASED C DELIVERED 75
NOT PURCHASED
NOT PURCHASED
NOT PURCHASED
NOT PURCHASED
PURCHASED t CUT/YOU HAUL
NOT PURCHASED
PURCHASED C DELIVERED 50
NOT PURCHASED
NOT PURCHASED
NOT PURCHASED
NOT PURCHASED
PURCHASED L DELIVERED 75
PURCHASED I DELIVERED 90
NOT PURCHASED
NOT PURCHASED
NOT PURCHASED
NOT PURCHASED
NOT PURCHASED
PURCHASED I DELIVERED 50
TOT PURCHASED
PURCHASED C CUT/T3U HAUL 30
PURCHASED t DaiVERED 75
NOT PURCHASED
Condition
of wood,
January
GREEN-
DRY
GREEN-
DRY
GREEN-
GREEN"
DRV
DRY
GREEN-
DRY
DRY
GREEN*
GREEN-
GREEN.
DRV
DRT
GREEN-
GREEN-
GREEN.
GREEN.
DRY
DRY
DRY
DRY
GREEN •
GREEN-
DRY
GREEN"
DRY
DRV
DRY
GREEN-
GREEN-
GREEN-
GREEN.
DRY
lit
Type loa
wood per
HARD 3
HARC *
HAID «
HAIC 4
HAID 4
son- i
HARD 3
HAIO 3
HAID 1
HAID <
HARD «
HAID i
HAID !
HAID <
HARD
50/50
HAID
HAID
HARD
HARC
HAID
HARD
HAID
HAIO
HAID
HAIO
HAID
HAID
HAID
HAID
HAIO
HAID
HAID
HAIO
HAID
HAIO
ties Wood
Jed used in
day January, ft
171
10
96
122
271
120
210
150
' 128
116
81
' 120
72
1 121
60
180
190
96
128
78
62
128
184
160
90
125
200
80
22*
75
160
160
126
27
100
<• 128
Utility
bill
3 1978, $
56.79
63.70
54.80
64.37
19.83
113.52
40.00
53.80
38.65
46.95
57.05
23.97
21.88
49.19
86.23
49.83
11.40
34.61
66.16
45.36
28.06
32.00
65.18
13.53
45.67
66.06
45.52
73.19
47.51
4*. 63
57.58
91.03
24.92
34.64
39.43
63.13
Kwh,
1978
2.204
2.484
2.000
2.554
708
4,500
1.400
2.052
1.510
1.606
2.104
676
142
1.896
3.568
1.922
650
1.306
2.66*
1.722
1. 000
1.165
2.5*2
518
1.762
2.580
1.758
2.868
1.73*
1.712
2.236
3.528
91*
1.33*
1.480
1.920
Utility
bill
1977, $
97.88
61.48
99 .26
77.67
55.10
112.89
63.00
98.10
150.40
66.58
81.**
61.88
67.30
81.65
It 3.00>
9*.*9
43 .19
6 7.* 8
135.00
75.62
21 .76
6* .99
125.5*
52 .on
45.00
1*5.21
72.39
91.60
11 7.00
36.62
90.23
90.1*
62.42
*4.73
71.66
61.50
Kwh,
1977
4,796
2,595
4.712
3.820
2.219
5.5(6
2.420
3,773
7,764
3.29*
3.121
2.380
2,588
3.96*
6.276
3.700
1,660
3.238
5.2C4
3,53*
820
4,0:*
6.21*
?,0"P
1.730
7, 2?2
3,4<6
4.782
*, 5C2
I.t56
4,40*
3.467
2.*01
1.720
2.756
3.1*0
FINAL TOTALS
**S
*,558
1.779.56 67,639 3.000.22 131.581
-------
TABLE B-4. TVA WOOD FOR ENERGY HEATING DEMONSTRATION - FEBRUARY 1978 DATA (68)
ID
number
0007
0006
0010
0012
0020
0021
0033
0030
0036
00)7
0000
0005
00*6
OOSI
0052
•OS)
•ess
• 060
006)
0065
«0»6
••77
0078
0108
• 109
• 111
0112
• ID
01 1«
• IIS
0116
• 119
0123
0120
0125
• 126
• 127
Where wood
obtained , February
TVA LAND
OTHER PUBLIC
OTHER PUBLIC
OTHER PUBLIC
OTHER PUBLIC
TOUR LAND
OTHER PUBLIC
TVA LAND
OTHER PUBLIC
TCUR LAND
OTHER PUBLIC
OTHER PRIVATE
TOUR LAND
TOUR LAND
TOUR LAND
TOUR LAND
TOUR LAND
TOUR LAND
TOUR LAND
OTHER PRIVATE
TOUR LAND
DO NOT UNO*
OTHER PRIVATE
OTHER PRIVATE
TVA LAND
OTHER PRIVATE
TOUR LAND
OTHER PRIVATE
TOUR LAND
OTHER PRIVATE
TOUR LAND
OTHER PUBLIC
00 NOT
-------
APPENDIX C
DERIVATION OF EMISSION FACTORS
Some calculations in this appendix have been made using nonmetric
units; however, all final emission factors were converted to
metric form in this appendix and in the text.
Source test measurements from six studies, summarized in Tables
C-l to C-6, were used to derive average emissions factors.
Emission data were presented in one study (7) for particulates,
CO, hydrocarbons and POM from wood combustion in fireplaces under
three conditions: startup, stable burning, and smoldering. Only
stable burning emissions are considered here, because startup and
smoldering are assumed to be small segments of the total combus-
tion time.
Because the results of some studies were reported as concentra-
tion of stack gas, it was necessary to calculate the emission
factors. The following examples illustrate the methods used in
converting concentrations to emission factors in g/kg.
For run number 6 (Table C-l), CO is expressed as 280 ppm. The
emission factor calculation is:
280 std m3 CO 12.771 std m3 flue gas ' 44.62 g - mole
x x
106 std m3 flue gas min std m3
28 g CO hr 60 min
x = 43.2 g CO/kg wood
g - mole CO 6.2 kg wood hr
For run number 6 (Table C-l), POM's are expressed as 5,746 ng/std
ft3. The Emission factor calculation is:
5,746 ng 10~9 g 12.771 std m3 flue gas
""" " ~ •" — X - X •--.... — ......., _.. .1,1.1
std ft3 flue gas 1 ng min
hr 60 min
x = 0.025 g POM/kg wood
6. 2 kg wood hr
77
-------
TABLE C-l.
oo
EMISSIONS DATA FOR WOOD COMBUSTION IN
FIREPLACES UNDER STABLE CONDITIONS (9)
Fuel type
Alder
Douglas Fir
Locust
,Pine
Run no.
from
Ref. 7
2
6
7
8
10
11
15
18
20
21
23
Burning
rate,
kg/hr
7.8
6.2
5.7
4.1
6.7
4.3
6.2
5.5
14.0
10.0
9.1
Stack
gas flow
rate,
std m3/min
10.513
12.771
12.139
11.715
11.814
11.737
11.414
12.709
10.986
10.539
10.727
Particulate
emission
factor ,
gAg
5.9
11.5
14.4
13.5
12.7
15.3
6.5
8.1
Nonme thane
volatile
POM, ng/std ft3 CO, ppm hydrocarbons,
(gAg) (gAg) ppm (gAg)
5,746(0.025) 280(43) 4.5(2.1)
405(87) 4.7(3.1)
7,444(0.044)
440(61) 5.3(2^2)
7,647(0.017)
Note.-Blanks indicate data not available.
TABLE C-2. EMISSIONS DATA FOR WOOD COMBUSTION (30)
Emissions, Ib/ton^
Test
code
from
Ref. 25
Al
A2
A3
A4
B2
Cl
C2
C3
Dl
D2
Wood
type
Eucalyptus
Eucalyptus
and oak
Eucalyptus
and oak
Oak
Oak
Oak
Oak
Madrone
Oak
Oak
Burning
rate,
Ib/hr
(kg/hr)
22(10
69(31)
5(2.3)
13(5.9)
12(5.5)
19(8.6)
15(6.8)
10(4.5)
25(11)
20(9.1)
CO
64 to 111
25.8
438
268 to 166
96.7
114
171
168
55.1
52.6
NOX
(as N02)
(gAg)
12(1.3)
35(0.8)
22(7.8)
16(2.1)
11(0.9)
8(0.8)
Organic
acids
(as acetic
acid)
20.2 to 16.2
<0.03
<0.03
^7.7
11.8
17.5
17.9
29.3
3.4
5.3
Phenols
1.5 to 2.2
<0.04
<0.04
M.6
0.83
1.6
2.8
4.8
0.2
0.48
Formaldehyde Acetaldehvde Organics
3.3 to 2.2
0.27
4.3
1.4 to 1.2
10.5
1.2
1.5
3.2
0.59
1,03
0.45
1.21
1.3
1.9
2.5
0.36
0.78
41 to 40
5.4 -
82.9
^32.8
44.5
39.3
48.8
66.3
11.9
15.1
Particulate
VL3.2
25.2 to 6.9
26.7
26.3
44.0
48.0
10.4
16.0
Note.-Blanks indicate data not available.
31 Ib/ton = 0.5 gAg-
b
ppm.
-------
TABLE C-3. PARTICULATE EMISSIONS DATA FOR WOOD COMBUSTION (31)
Emission factor
Stove
Jotul
Jotul
Jotul
Jotul
Jotul
Franklin
Franklin
Wood
Pine
Pine
Oak
Oak
Birch
Oak
Very
dry oak
Draft
setting
1/2 open
1/4 open
1/2 open
open
1/2 open
_a
a
Number
of runs
6
5
6
2
2
15
3
Average
4.5
10
1.7
1.17
2.3
2.8
1.02
Standard
Deviation
1.0
8
0.9
0.01
1.7
1.0
0.10
, g/kg
Range
2.9 to 5.6
4.5 to 25
0.7 to 2.8
1.16 to 1.18
1.1 to 3.5
1.2 to 4.4
0.91 to 1.08
Not applicable.
TABLE C-4. EMISSIONS DATA FOR WOOD COMBUSTION, STABLE CONDITIONS (32)
Test code
from
Ref. 32 Sampling location
2
4
5
8
10
13
16
17
18
19
Condominium
Condominium
Condominium
Condomin ium
Condominium
Condominium
Residential
Residential
Residential
Stove
fireplace
fireplace
fireplace
fireplace
fireplace
fireplace
fireplace
fireplace
fireplace
Burning
Type rate ,
fuel kg/hr
Dry pine
Dry pine
Dry pine
Green aspen
Dry aspen
Green pine
Dry pine
Dry pine
Green pine
Dry pine
8.2
11.5
10.1
7.1
8.1
7.1
3.2
3.2
4.6
6.2
Flow rate,
std m3/min
12,1
9.3
10.9
13.1
12.2
10.6
7.4
7.5
6.8
2.2
Particulates,
g/kg
16
15
16
19
15
20
20
23
26
28
.6
.3
.7
.1
.8
.0
.8
.1
.3
.3
a
(
1
1
1
1
1
8
CO,
ppm
gAg)
269(28)
,308(74)
,117(81)
,111(144)
659(75)
,033(108)
647(105)
670(110)
,001(104)
,194(204)
C02,
ppm
10,634
12,571
8,419
6,004
7,383
4,840
8,085
10,883
7,523
115,007
Hydrocarbons,
ppm (g/kg)
222(13)
2,575(83)
1,337(18)
4,023(297)
1,042(63)
920(55)
4,162(385)
1,507(141)
451(27)
3,130(44)
The particulate emission factors were calculated using both the front-half and back-half catch.
portion on back half averaged 75% of the total particulate loadings.
b
Hydrocarbons reported as methane equivalents.
The condensable
-------
TABLE C-5. EMISSIONS DATA FOR WOOD COMBUSTION (29)
oo
o
Wood burning
device
Fireplace
Fireplace
Baffled stove
Baffled stove
Baffled stove
Nonbaffled stove
Nonbaffled stove
Nonbaffled stove
Nonbaffled stove
Wood
type
Seasoned oak
Green oak
Seasoned pine
Green pine
Seasoned oak
Green oak
Seasoned pine
Green pine
Seasoned oak
Green oak
Seasoned pine
Green pine
Wood
burning
rate,3
kg/min
0.18
0.17
0.19
0.16
0.14
0.11
0.12
0.10
0.13
0.11
0.12
0.13
Flow
rateB
NmVmin
6.5
6.4
6.5
6.5
1.5
0.9
1.0
2.0
0.9
0.9
0.9
0.8
Emission factor, gAg
Particulates
2.3
2.5
1.8
2.9
3.0
2.5
3.9
7.0
2.5
1.8
2.0
6.3
(0.13)
(0.19)
(0.10)
(0.21)
(0.17)
(0.19)
(0.21)
(0.51)
(0.14)
(0.13)
(0.11)
(0.46)
Condensable
organicsd
6.3
5.4
5.9
9.1
4.0
3.8
4.1
12.0
6.0
3.3
5.6
10.0
(0.35)
(0.40)
(0.32)
(0.67)
(0.22)
(0.28)
(0.23)
(0.88)
(0.34)
(0.25)
(0.31)
(0.74)
Volatile
hydrocarbons6
19 (1.1)
j
j
j
j
j
2.8 (0.15)
j
j
0.3 (0.02)
j
3.0 (0.22)
2.
1.
1.
1.
0.
0.
0.
0.
0.
0.
0.
0.
u
4
9
4
7
4
7
5
8
4
5
4
(0.13)
(0.14)
(0.08)
(0.13)
(0.02)
(0.05)
(0.03)
(0.06)
(0.02)
(0.04)
(0.01)
(0.03)
(g/MJ)
SOx9
j
j
j
j
j
3
j
0.16 (0.01)
j
0.24 (0.02)
j
coh
30 (1.7)
22 (1.6)
21 (1.2)
15 (1.1)
110 (6.2)
120 (9.0)
270 (15)
220 (16)
370 (21)
91 (6.8)
150 (8.2)
97 (7.1)
POM1
0.025 (0.0014)
j
j
0.036 (0.0026)
0.21 (0.012)
j
0.37 (0.020)
j
0.19 (0.011)
j
j
0.32 (0.024)
aAverage burning rate during EPA Method 5, POM, and SASS train operation.
Determined from average EPA Method 5 data.
°Front half of EPA Method 5 and POM train. Averaged when two values available.
dBack half of EPA Method 5. Averaged when two values available.
eGC/FID
fEPA Method 7. Average of 6 grab samples.
9EPA Method 6.
"EPA Method 3 (ORSAT) for stoves; average of 10 samples. Drager tube for fireplaces 15 to 30 minute composite.
^OM train (EPA Method 5 modified with XAD resin trap).
•'NO data obtained.
-------
TABLE C-6. PARTICULATE EMISSIONS DATA FOR WOOD COMBUSTION (33)
Stove
Jotul
Jotul
Jotul
Jotul
Jotul
Jotul
Jotul
Jotul
Jotul
Jotul
Jotul
Jotul
Jotul
Jotul
Jotul
Jotul
Jotul
Jotul
Jotul
Jotul
Jotul
Jotul
Jotul
Jotul
Rite-
way
Rite-
way
a
Wood
Oak
Oak
Oak
Oak
Oak
Oak
Oak
Oak
Oak
Oak
Oak
Oak
Oak
Oak
Oak
Oak
Oak
Oak
Oak
Pine
Pine
Pine
Pine
Pine
Oak
Pine
%
moisture
23.8
23.8
23.8
23.8
23.8
23.8
23.8
23.8
22.8
22.8
22.8
19.8
8.7
8.7
8.7
8.7
23.8
23.8
23.8
42.4
42.4
42.4
42.4
42.4
22.8
42.8
Draft
1
1
h
h
%
h
%
k
k
h
k
%
k
\
\
%
<\
<%
-------
In cases where emission data was reported as Ib/ton, the follow-
ing conversion factor was used: 1 Ib/ton = 0.5 g/kg.
Average emission factors (Table 8) were determined by considering
the average of tests conducted on one piece of combustion equip-
ment and test condition. Replicate runs with a specific wood
type were treated as one separate test. For example, Refer-
ence 30 reports two tests burning oak and one burning madrone in
fireplace C. The madrone test is considered as a separate test
in calculating the overall emission factor. The oak tests were
first averaged and then considered as one test.
82
-------
APPENDIX D
TOTAL WOOD-FIRED RESIDENTIAL COMBUSTION EMISSIONS
Total criteria emissions from wood-fired residential combustion
equipment were compared on a state and national basis to emis-
sions from all stationary sources. State emissions were calcu-
lated by multiplying the emission factors presented in Section 4
by the estimated fuel usage in each state for wood-fired residen-
tial combustion. Tables D-l, D-2, and D-3 give the percent con-
tribution to total state and national criteria emissions for
primary heating with stoves, auxiliary heating with wood stoves,
and aesthetic burning in fireplaces, respectively. Total state
emissions were taken from the NEDS inventory (69) which is shown
in Table D-4.
(69) 1972 National Emissions Report. EPA 450/2-74-012, Environ-
mental Protection Agency, research Triangle Park, North
Carolina. .Tnno 1 Q'JA A oo ~~
Carolina, June 1974. 422 pp.
83
-------
TABLE D-l. PERCENTAGE OF TOTAL STATE CRITERIA EMISSIONS
DUE TO PRIMARY RESIDENTIAL HEATING WITH WOOD
State
Alabama
Alaska
Arizona
Arkansas
California
Colorado
Connecticut
Delaware
Florida
Georgia
Hawaii
Idaho
Illinois
Indiana
Iowa
Kansas
Kentucky
Louisiana
Maine
Maryland
Massachusetts
Michigan
Minnesota
Mississippi
Missouri
Montana
Nebraska
Nevada
New Hampshire
New Jersey
New Mexico
New York
North Carolina
North Dakota
Ohio
Oklahoma
Oregon
Pennsylvania
Rhode Island
South Carolina
South Dakota
Tennessee
Texas
Utah
Vermont
Virginia
Washington
West Virginia
Wisconsin
Wyoming
Percent
Particulates
0.12
3.3
0.46
1.8
0.18
0.08
0.51
0.13
0.12
0.76
0.01
0.99
0.02
0.07
0.07
0.06
0.32
0.09
3.40
0-.09
0.25
0.10
0.37
1.09
1.50
1.12
0.12
0.14
3.46
0.11
1.08
0.87
0.64
0.03
0.02
0.76
1.58
0.06
0.32
0.89
0.36
0.72
0.14
0.14
2.04
0.53
1.15
0.15
0.20
0.12
of total state emissions
SOy NOx
<0.01 0.02
0.17 0.07
0.01 0.01
0.14 0.08
0.01 0.01
0.01 0.01
<0.01 <0.01
<0.01 <0.01
<0.01 <0.01
0.01 0.05
<0.01 <0.01
0.02 0.06
<0.01 <0.01
<0.01 <0.01
<0.01 <0.01
<0.01 <0.01
<0.01 0.02
<0.01 <0.01
0.03 0.10
<0.01 <0.01
<0.01 <0.01
<0.01 <0.01
<0.01 0.02
0.08 0.06
<0.01 0.04
<0.01 0.02
<0.01 <0.01
<0.01 <0.01
0.01 0.04
<0.01 <0.01
<0.01 0.03
<0.01 0.01
0.01 0.04
<0.01 <0.01'
<0.01 <0.01
0.01 0.02
0.16 0.10
<0.01 <0.01
<0.01 <0.01
0.02 0.02
0.02 0.02
<0.01 0.04
<0.01 <0.01
<0.01 <0.01
0.04 0.07
0.01 0.04
0.02 0.05
<0.01 <0.01
<0.01 0.01
<0.01 <0.01
Hydrocarbons
0.30
2.22
0.24
1.78
0.11
0.12
0.1
0.1
0.06
0.90
0.01
0.90
0.02
0.1
0.07
0.1
0.7
0.03
1.9
0.2
0.07
0.1
0.3
1.3
1.0
0.3
0.1
0.3
0.8
0.03
1.0
0.2
0.9
0.05
0.05
0.3
1.6
0.2
0.09
0.3
0.3
1.1
0.05
0.1
1.0
0.9
0.8
0.4
0.2
0.2
CO
1.48
5.41
0.81
5.94
0.43
0.38
0.5
0.5
0.2
3.0
0.05
3.1
0.08
0.36
0.2
0.4
2.9
0.12
9.0
0.7
0.3
0.4
1.1
4.4
3.3
1.8
0.4
1.2
4.0
0.1
4.4
0.6
3.5
0.2
0.2
1.0
5.7
0.6
0.3
0.8
1.0
4.0
0.2
0.5
3.9
3.2
2.2
1.3
1.0
0.6
Total 0.3 <0.01 0.01 0.3 1.0
84
-------
TABLE D-2.
PERCENTAGE OF TOTAL STATE CRITERIA EMISSIONS
DUE TO AUXILIARY RESIDENTIAL HEATING WITH WOOD
Percent of total state emissions
State
Alabama
Alaska
Arizona
Arkansas
California
Colorado
Connecticut
Delaware
Florida
Georgia
Hawaii
Idaho
Illinois
Indiana
Iowa
Kansas
Kentucky
Louisiana
Maine
Maryland
Massachusetts
Michigan
Minnesota
Mississippi
Missouri
Montana
Nebraska
Nevada
New Hampshire
New Jersey
New Mexico
New York
North Carolina
North Dakota
Ohio
Oklahoma
Oregon
Pennsylvania
Rhode Island
South Carolina
South Dakota
Tennessee
Texas
Utah
Vermont
Virginia
Washington
West Virginia
Wisconsin
Wyoming
Total
Partic-
ulates
0.28
2.09
0.32
0.66
0.24
0.28
3.27
0.33
0.85
0.50
0.13
0.31
0.21
0.15
0.29
0.15
0.28
0.20
8.14
0.17
2.55
0.53
1.24
0.60
1.04
0.06
0.35
0.07
20.78
1.01
0.22
4.99
0.23
0.17
0.12
0.33
1.35
0.14
1.52
0.28
0.27
1.89
0.48
0.32
12.08
0.22
2.17
0.18
0.46
0.11
0.5
sox
<0.01
0.11
<0.01
0.05
0.01
0.02
0.02
<0.01
<0.01
0.01
<0.01
0.01
<0.01
<0.01
<0.01
0.01
<0.01
0.01
0.06
<0.01
0.01
0.01
0.02
0.04
0.02
<0.01
0.01
<0.01
0.1
0.01
<0.01
0.05
<0.01
<0.01
<0.01
<0.01
0.1
<0.01
<0.01
<0.01
0.02
0.01
<0.01
<0.01
0.2
<0.01
0.03
<0.01
<0.01
<0.01
<0.01
NOx
0.06
0.05
0.01
0.03
<0.01
0.02
0.05
0.01
0.02
0.03
<0.01
<0.01
0.01
<0.01
0.01
0.01
0.02
<0.01
0.3
0.02
0.04
<0.01
0.06
0.03
0.03
<0.01
0.02
<0.01
0.3
0.02
<0.01
0.07
0.01
<0.01
0.01
<0.01
0.09
<0.01
0.02
<0.01
0.02
0.1
0.01
0.02
0.4
0.02
0.10
<0.01
0.03
<0.01
0.2
Hydro-
carbons
0.7
1.4
0.2
0.6
0.2
0.4
0.8
0.3
0.4
0.6
0.1
0.3
0.2
0.3
0.3
0.2
0.7
0.06
4.51
0.40
0.77
0.72
1.12
0.71
0.71
0.08
0.36
0.18
4.85
0.26
0.21
1.10
0.35
0.26
0.27
0.13
1.35
0.39
0.42
0.09
0.22
2.96
0.16
0.33
5.81
0.39
1.41
0.46
0.50
0.21
0.4
CO
3.44
3.47
0.57
2.15
0.59
1.27
2.91
1.17
1.43
1.98
0.59
0.99
0.74
0.76
0.86
1.01
2.59
0.27
21.18
1.34
2.90
2.29
3.75
2.42
2.26
0.53
1.18
0.63
24.09
1.06
0.91
3.25
1.29
0.82
0.86
0.42
4.92
1.35
1.40
0.26
0.73
10.52
0.76
1.14
23.33
1.34
4.23
1.57
2.40
, 0.54
2.1
85
-------
TABLE D-3.
PERCENTAGE OF TOTAL STATE CRITERIA EMISSIONS
DUE TO RESIDENTIAL WOOD BURNING IN FIREPLACES
Percent of total
State
Alabama
Alaska
Arizona
Arkansas
California
Colorado
Connecticut
Delaware
Florida
Georgia
Hawaii
Idaho
Illinois
Indiana
Iowa
Kansas
Kentucky
Louisiana
Maine
Maryland
Massachusetts
Michigan
Minnesota
Mississippi
Missouri
Montana
Nebraska
Nevada
New Hampshire
New Jersey
New Mexico
New York
North Carolina
North Dakota
Ohio
Oklahoma
Oregon
Pennsylvania
Rhode Island
South Carolina
South Dakota
Tennessee
Texas
Utah
Vermont
Virginia
Washington
West Virginia
Wisconsin
Wyoming
Total
Partic-
ulates
0.04
0.5
0.6
0.2
0.5
0.3
1.6
0.2
0.5
0.1
0.2
0.3
0.1
. 0.1
0.2
0.1
0.1
0.1
0.4
0.1
1.2
0.2
0.2
0.2
0.3
0.1
0.2
0.1
1.1
1.0
0.9
2.4
0.1
0.1
0.1
0.4
0.3
0.1
1.5
0.2
0.2
0.1
0.3
0.3
0.7
0.1
0.5
0.02
0.2
0.1
0.2
NOX
0.02
0.04
0.06
0.02
0.04
0.06
0.06
0.02
0.03
0.02
0.05
0.05
0.02
<0.01
0.03
0.02
0.02
0.02
0.04
0.03
0.05
<0.01
0.03
0.02
0.02
0.02
0.03
0.02
0.04
0.05
0.07
0.1
0.03
0.02
0.02
0.02
0.06
0.01
0.06
<0.01
0.03
0.02
0.02
0.04
0.06
0.03
0.06
0.01
0.02
0.02
0.02
state emissions
Hydro-
carbons
0.4
1.4
1.3
0.80
1.2
1.5
1.6
0.6
1.1
0.7
1.0
1.1
0.5
0.7
0.8
0.6
0.7
0.1
1.0
X0.01
1.5
1.0
0.8
0.8
1.0
0.3
1.0
1.4
1.1
1.0
3.4
1.7
. 0.8
0.7
0.7
0.6
1.2
1.6
1.7
0.2
0.6
0.8
0.4
1.3
1.3
1.0
1.3
1.1
0.7
0.8
0.8
CO
0.1
0.2
0.3
0.2
0.3
0.3
0.4
0.2
0.2
0.1
0.3
0.2
0.1
0.1
0.1
0.2
0.2
0.04
0.3
0.2
0.4
0.2
0.2
0.2
0.2
0.1
0.2
0.3
0.3
0.3
0.9
0.4
0.2
0.1
0.1
0.1
0.3
0.3
0.3
0.04
0.1
0.2
0.1
0.3
0.3
0.2
0.2
0.2
0.2
0.1
0.2
86
-------
TABLE D-4.
NEDS EMISSION SUMMARY BY STATE (69)
(metric tons)
State
Alabama
Alaska
Arizona
Arkansas
California
Colorado
Connecticut
Delaware
Dist. Columbia
Florida
Georgia
Hawaii
Idaho
Illinois
Indiana
Iowa
Kansas
Kentucky
Louisiana
Maine
Maryland
Massachusetts
Michigan
Minnesota
Mississippi
Missouri
Montana
Nebraska
Nevada
New Hampshire
New Jersey
New Mexico
New York
North Carolina
North Dakota
Ohio
Oklahoma
Oregon
Pennsylvania
Rhode Island
South Carolina
South Dakota
Tennessee
Texas
Utah
Vermont
Virginia
Washington
West Virginia
Wisconsin
Wyoming
Particulates
1,178,643
13,913
72,685
137,817
1,006,452
201,166
40,074
36,808
19,451
226,460
404,574
61,621
55,499
1,143,027
748,405
216,493
348,351
546 ,214
380,551
49,155
494,921
96,160
705,921
266,230
168,355
202,435
272,688
95,338
94,040
14,920
151,768
102,785
160,044
481,017
78,978
1,766,056
93,595
169,449
1,810,598
13,073
198,767
52,336
409,704
549,399
71,692
14,587
477,494
161,934
213,715
411,558
75,427
SOX
882,731
5,874
1,679,768
39,923
393,326
49,188
168,068
209,310
60,630
897,381
472,418
45,981
54,387
2,043,020
2,050,541
283,416
86,974
1,202,827
166,664
144,887
420,037
636,466
1,466,935
391,633
50,591
1,152,373
871,235
58,014
304,851
86,596
463,736
444,310
345,979
473,020
78,537
2,980,333
130,705
36,776
2,929,137
65,761
247,833
17,354
1,179,982
753,098
152,526
17,751
447,394
272,991
678,348
712,393
69,394
NOX
397,068
32,757
123,871
168,989
1,663,139
147,496
155,832
58,407
46,824
644,794
369,817
44,221
48,552
974,372
1,371,233
242,524
233,987
419,142
442,817
76,741
265,204
334,379
2,222,438
311,834
172,519
448,300
148,405
101,948
88,933
67,309
489,216
199,181
572,451
412,599
85,708
1,101,470
222,687
135,748
3,'017,345
46,921
521,544
49,490
426,454
1,303,801
' 80,998 •
24,286
329,308
187,923
229,598
408,525
72,572
Hydrocarbons
643,410
28,389
189,981
195,538
2,160,710
193,456
219,661
63,886
41,789
619,872
458,010
89,530
84,230
1,825,913
600,477
316,617
309,633
326,265
1,919,662
122,918
295,867
440,481
717,891
410,674
195,950
413,130
271,824
127,821
53,673
88,469
819,482
152,057
1,262,206
447,238
70,289
1,153,493
341,358
234,669
891,763
65,833
907,833
90,478
362,928
2,218,891
98,282
41,980
369,416
344,643
116,155
523,930
55,319
CO
1,885,657
167,357
815,454
843,204
8,237,667
875,781
897,580
204,227
190,834
2,695,817
2,036,010
275,566
343,720
6,412,718
2,933,780
1,440,621
1,002,375
1,189,932
5,633,827
376,196
1,261,804
1,682,218
3,243,526
1,760,749
829,094
1,854,901
611,061
569,522
215,751
256,380
2,877,319
504,249
4,881,922
1,734,398
318,679
5,205,719
1,456,627
929,247
3,729,830
283,650
4,222,168
387,356
1,469,253
6,897,748
402,527
150,510
1,548,031
1,659,117
494,214
1,582,869
303,297
ADJUSTMENTS TO GRAND TOTAL
The United States summary does not include certain source categories. The following
additions should be considered part of the United States grand total for a more
accurate picture of nationwide emissions.
New York
pt. sources 311,000
Forest wild fires 375,000
Agricultural burning 272,000
Structural fires 52,000
Coal refuse piles 100,000
Total 1,110,000
U.S. subtotal
(above) 16,762,000
U.S. grand total 17,872,000
993,000
0
15,000
0
128,000
1,076,000
28,873,000
29,949,000
382,000
68,000
29,000
6,000
31,000
536,000
21,722,000
22,258,000
127,000
529,000
272,000
61,000
62,000
1,051,000
23,994,000
25,045,000
44,000
3,089,000
1,451,000
200,000
308,000
5,086,000
91,782,000
96,868,000
87
-------
GLOSSARY
affected population: Number of persons around an average source
who are exposed to a source severity greater than 0.05 or
1.0 as specified.
average source: Wood-fired residential combustion source defined
for use in calculating source severity.
boiler: Closed vessel in which fuel is burned to generate steam
or heat water.
criteria emissions: Those for which air quality standards have
been established.
damper: Valve or plate used to regulate the flow of air to a
combustion process.
draft: Pressure difference causing flow of a fluid, usually
applied to convection flow as in chimneys.
emission factor: Quantity of emission per quantity of fuel
burned.
flue: Enclosed passage for conveying combustion gases to the
atmosphere.
housing unit: Apartment, group of rooms, or a single room occu-
pied or intended for occupancy as separate living quarters.
national emission burden: Ratio of annual emissions from a
specific source to the total national emissions from all
stationary sources.
overfeed: Method of feeding solid fuel to a fuel bed where the
fresh fuel is charged to the top of the fuel bed.
overfire: Portion of the combustion air which enters the combus-
tion zone over the fuel bed to provide turbulence for smoke
reduction in hand- and stoker-fed coal combustion equipment.
plenum: Air space or chamber under pressure.
88
-------
pyrolysis: Chemical decomposition by the application of heat.
source severity: Indication of the hazard potential of an emis-
sion source.
state emission burden: Ratio of annual emissions from a specific
source in any state to the total state emissions from all
stationary sources.
threshold limit value (TLV®): Airborne concentrations of sub-
stances to which it is believed that nearly all workers may
be exposed day after day without adverse effect.
underfire: Method of providing combustion air to a fuel bed by
forcing the air through the fuel bed from underneath.
'warm air furnace: Closed vessel in which fuel is burned to heat
room air.
wind box: Enclosure around a stoker which directs combustion
air through the retort.
89
-------
CONVERSION FACTORS AND METRIC PREFIXES (70)
CONVERSION FACTORS
To convert from
Degree Celsius (°C)
Degree Kelvin (°K)
Gram (g)
Gram/second (g/s)
Joule (J)
Kilogram (kg)
Kilogram (kg)
Kilogram/meter3 (kg/m3)
Kilometer2 (km2)
Meter (m)
Meter (m)
Meter3 (m3)
Metric ton
Pascal (Pa)
To
Degree Fahrenheit (°F)
Degree Celsius (°C)
Pound-mass
Pounds/hour
British thermal unit
(Btu)
Pound mass
(avoirdupois)
Ton (short, 2,000 Ib
mass)
Lb mass/foot3
Mile2
Foot
Inch
Foot3
Pound-mass
Pound-force/inch2
(psi)
Multiply by
= 1.8 t° +
32
= t£ - 273.15
2.205 x 10~3
7.930
9.479 x 10~4
2.204
1.102 x 10~3
6.243 x 10~2
2.591
3.281
3.937 x 101
3.531 x 101
2.205 x 103
1.450 x 10-1*
Prefix
Giga
Mega
Kilo
Milli
Micro
Symbol
G
M
k
m
METRIC PREFIXES
Multiplication
factor
109
106
103
io-3
10~6
Example
!Gg=lxl09 grams
1 MJ = 1 x IO6 joules
1 kPa = 1 x 103 pascals
1 mg = 1 x 10~3 gram
1 ym = 1 x 10~6 meter
(70) Standard for Metric Practice. ANSI/ASTM Designation
E 380-76E, IEEE Std 268-1976, American Society for Testing
and Materials, Philadelphia, Pennsylvania, February 1976.
37 pp.
90
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-600/2- 80-042b
2.
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
Source Assessment: Residential Combustion of Wood
5. REPORT DATE
March 1980
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
D.G. DeAngelis, D.S. Ruffin, J.A. Peters, and R.B. Reznik
8. PERFORMING ORGANIZATION REPORT NO
MRC-DA-974
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Monsanto Research Corporation
1515 Nicholas Road
Dayton, Ohio 45418
10. PROGRAM ELEMENT NO.
1AB015
11. CONTRACT/GRANT NO.
68-02-1874, Task 23
12 SPONSORING AGENCY NAME AND ADDRESS
EPA, Office of Research and Development
Industrial Environmental Research Laboratory
Research Triangle Park, NC 27711
13. TYPE OF REPORT AND PERIOD CO
Task Final; 11/76 - 2/80
VERED
14. SPONSORING AGENCY CODE
EPA/600/13
B SUPPLEMENTARY NOTES
IERL-RTP project officer is John 0.~Milliken, Mail Drop 63,
CT
The report gives results of ^ estimate of the potential environmental im-
pact of the residential combustion of wood. About 16. 6 million metric tons of wood
was burned in the residential section in 1976. About 30% of this was burned for pri-
mary heating in about 912,000 residential units. Geographic distribution of wood-
fired heaters is related to the natural forest regions in the U.S. By 1985, over 10
million homes will be using some wood fuel. Emissions from wood-fired residential
heaters include particulates , SOx, NOx, CO, hydrocarbons (HC), and polycyclic or-
ganic material (POM). The impact of these emissions has been assessed by source
severity, involving estimating maximum ground level concentrations of pollutants
and comparing these concentrations to a National Ambient Air Quality Standard for
criteria pollutants or to a reduced threshold limit value for non-criteria pollutants.
A comparative analysis of source severities for residential wood combustion with
other stationary sources indicates that residential wood combustion is a major
source of POM. Particulate, HC, and CO emissions from all residential wood-fired
sources were estimated to contribute 1.0, 1.5, and 3.8%, respectively, of the total
national emission burden for those species in 1976.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Pollution
Combustion
Wood
Residential Buildings
Heating Equipment
Assessments
Dust
Sulfur Oxides
Nitrogen Oxides
Carbon Monoxide
Hydrocarbons
Polycyclic Com-
pounds
Pollution Control
Stationary Sources
Residential Heaters
Source Assessment
Particulate
Polycyclic Organic Ma-
terial
13B
2 IB
11L
13M
13A
14B
11G
07B
07C
Release to Public
19. SECURITY CLASS (ThisReport)
Unclassified
21. NO. OF PAGES
99
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
91
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