United States
Environmental Protection
Agency
National Risk Management
Research Laboratory
Research Triangle Park, NC 27711
Research and Development
EPA/600/SR-96/119
November 1996
^» EPA Project Summary
Wood Products in the Waste
Stream-Characterization and
Combustion Emissions
Richard S. Atkins and Christine T. Donovan
Waste wood is wood separated from
a solid-waste stream and processed
into a uniform-sized product that is re-
used for other purposes such as fuel.
As an alternative to the combustion of
fossil fuels, it has raised concerns that,
if it is "contaminated" with paints, res-
ins, preservatives, etc., unacceptable
environmental impacts may be gener-
ated during combustion. Given the dif-
ficulty of separating contaminated ma-
terial from waste wood and the large
energy potential existing in the re-
source, it is important to identify pos-
sible problems associated with con-
taminated waste-wood combustion.
This project:
• Identifies the quantity and quality
of waste wood;
• Summarizes regulatory issues af-
fecting the processing and com-
bustion of waste wood for energy;
• Characterizes waste-wood process-
ing and combustion facilities;
• Characterizes representative waste-
wood samples; and
• Collects and analyzes emissions
data from operating combustion fa-
cilities.
Types of waste wood described in-
clude pallets; construction and demoli-
tion waste; wood treated with paints or
stains; wood containing glues, binders,
or resins; wood containing plastics or
vinyl wood treated with preservatives
such as creosote, chloropentaphenol,
and chromium copper arsenate; and
wood treated with pesticides or fungi-
cides.
This study, completed in mid-1992,
describes research of technical, public
policy, and regulatory issues that af-
fect the processing and combustion of
waste wood for fuel.
The report provides environmental
regulators, project developers, and oth-
ers with data to make informed deci-
sions on the use of waste-wood mate-
rials as a combustion resource. Poten-
tial environmental problems and solu-
tions were identified.
One project result was the identifica-
tion of combustion-system operating
parameters and air pollution control
technologies that can minimize emis-
sions of identified air and solid-waste
contaminants from the combustion of
waste wood.
This Project Summary was developed
by EPA's National Risk Management
Research Laboratory's, Air Pollution
Prevention and Control Division, Re-
search Triangle Park, NC, to announce
key findings of the research project
that is fully documented in a separate
report of the same title (see Project
Report ordering information at back).
Introduction
This report emphasizes understanding
the differences in air emissions and ash
characteristics from the combustion of
"clean" wood compared to "treated" wood.
Clean and treated wood are produced by
a variety of municipal, commercial, indus-
trial, agricultural, construction, and demo-
lition activities. Treated wood is commonly
referred to as "urban," "recycled," "treated,"
"dirty," and/or "demolition" wood. "Clean"
wood is a by-product of harvesting activi-
ties connected with forest management,
commercial logging, and site conversion.
Harvested wood may be in the form of
chips or stumps.
In most states evaluated in this study,
the source and type of wood fuel affect
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the environmental permitting of facilities.
Each state or province has developed defi-
nitions for different wood fuels, or classi-
fies combustion facilities according to the
type of wood fuel burned. For this report,
wood-fuel types are divided into "clean" or
"treated" wood. "Clean" wood is untreated
and uncontaminated natural wood.
In this report, wood is referred to as
"waste wood" when it is in its prepro-
cessed form and as "processed wood"
when it has been prepared for fuel.
Federal, State, and Provincial
Regulations
The project (1) reviewed existing fed-
eral, state, and provincial air, solid waste
and energy policies, and regulations that
relate to waste-wood processing and com-
bustion facilities; (2) identified major trends
in policies that affect the processing and
use of waste wood for energy; and (3)
investigated ash disposal from waste-wood
combustion facilities.
Major air quality regulatory issues that
affect waste-wood combustion facilities in-
clude:
• Regulatory implications for permitting
a "treated" or a "clean" wood com-
bustion facility;
• The level of control and/or control
equipment currently considered best
available control technology; and
• Implications of the 1990 Clean Air
Act Amendments for new and exist-
ing wood-combustion facilities.
Types and Amounts of Waste
Wood A vailable for Fuel
This study compiled data on the types
and amounts of waste wood currently gen-
erated and used for fuel in the eight-state,
one-province study area to estimate the
amount of wood separated from the waste
stream and processed into fuel. This wood
is derived from a variety of forest harvest-
ing, municipal, commercial, industrial, ag-
ricultural, construction, and demolition ac-
tivities. Identifying the types and amounts
of waste wood that may contain non-wood
materials or "contaminants," such as paint,
stain, and preservatives, is emphasized.
Information from state energy offices, for-
estry and wood use experts, solid-waste
managers, forest products industries, and
published research on forestry and waste-
wood resources is included.
Composition of Waste Wood
The study identified specific types of
treated waste-wood materials that are com-
monly found in solid-waste streams in-
cluding:
• Wood products manufactured with
glues, binders, or resins, such as struc-
tural and non-structural panels (e.g.,
plywood, particleboard, masonite,
waferboard, and wood laminates);
• Wood products treated with paints,
stains, or coatings; and
• Wood products impregnated with pre-
servatives such as creosote, pentachlo-
rophenol, or chromium copper arsen-
ate (CCA) (e.g., railroad ties, utility
poles, and exterior grade lumber).
Information and product-specific data
were obtained from industry reports, sales
representatives, research chemists, state
and federal government research scien-
tists, and others. A summary of common
wood products and the levels and types
of non-wood contaminants is provided.
Major issues affecting the use of waste
wood (especially treated wood) for fuel
are the types and amounts of potential
contaminants contained in the material and
the physical, chemical, and environmental
characteristics of the contaminant.
Waste-Wood Processing
Facilities
The study investigated facilities that col-
lect, sort, and process waste wood for
fuel. Six processing facilities in the U.S.
and Canada were visited. In addition, pro-
cessing equipment manufacturers, solid-
waste regulators, and facility owners and
operators that were not visited were inter-
viewed.
Research focused on investigating regu-
latory and economic issues that affect the
ability of processors to use wood from the
waste stream; determining the types and
sizes of facilities that process waste wood
in the study area; and identifying the ma-
jor types and capabilities of equipment
and systems used to process wood for
fuel.
The study determined that operation of
a waste-wood processing facility is contin-
gent on many factors including the eco-
nomic and regulatory climate that affects
the types of waste wood available to pro-
cessing facilities; ways in which recycling
and solid-waste management authorities
permit a processing facility; and the size
and specifications of markets that use pro-
cessed waste wood for fuel or other uses.
Waste-wood processing methodologies,
equipment, and systems are evolving to
meet the requirements of various end-use
markets. Facility operators are becoming
more specific about the types of wood
accepted for processing. The level of in-
spection and enforcement of unaccept-
able materials prior to processing is an
important step in achieving and maintain-
ing the quality and specifications required
for fuel and other end-use products.
Waste-Wood Combustion
Facilities
Combustion facilities that burn, or in-
tend to burn, processed waste wood for
fuel were researched and identified in the
study area. Data on the capacity of the
facility, type of fuel handling, combustion,
pollution control equipment used, and stack
emissions and ash characteristics were
collected. Research techniques included
surveying commercial and industrial wood
energy facilities; visiting two combustion
facilities in the U.S. and Canada; complet-
ing telephone interviews with plant engi-
neers, equipment manufacturers, and air-
quality regulators; and reviewing published
research about the performance of vari-
ous wood-combustion systems.
The study identified key issues con-
cerning fuel specifications and procure-
ment, fuel delivery and feeding equipment,
and furnace and boiler designs for com-
bustion facilities that use processed wood
for all or part of their feedstock. The study
focused on utility-scale power plants that
burn processed wood exclusively for elec-
trical generation, and industrial facilities
that burn processed wood to produce ther-
mal and/or electrical energy. In particular,
the project team investigated the issues
that affect the decision to procure and
burn processed waste wood.
The decision to use processed waste
wood for fuel, especially treated wood, is
primarily affected by the fuel requirements
of the combustion system; availability of
fuel from untreated waste wood; local air
quality conditions and local environmental
regulations and standards; and the famil-
iarity of state, provincial, or local regula-
tory authorities with waste-wood combus-
tion technologies and facilities.
Chemical and Physical
Properties of Waste Wood and
Its Ashes
The chemical and physical properties of
waste woods and the ashes produced from
their combustion were evaluated. There is
limited information available in the techni-
cal literature. There is some information
on "clean" wood but it is also extremely
limited and not completely applicable to
waste-wood combustion. Since there is
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increased interest in using waste wood to
produce energy, it is important to under-
stand its properties to predict the environ-
mental impact from its burning.
The type of information gathered for
this study is needed to evaluate the emis-
sion of trace metals due to combustion of
waste wood and to understand the metal
contaminants in the ash. The waste-wood
data collected can be used by develop-
ers, regulators, and others.
This study used random sampling tech-
niques to obtain waste wood and ash
samples from six waste-wood processing
and two combustion facilities that em-
ployed various processing and combus-
tion methods. Samples gathered at these
facilities were then finely ground, blended,
and analyzed to obtain information on their
chemical and physical properties. Ash
samples were obtained from combustion
facilities and also by laboratory ashing the
collected waste-wood samples.
As part of this study, homogeneous
waste-wood samples were collected and
analyzed. Some of these samples were
collected from facilities also burning these
homogeneous materials. In those in-
stances, ash samples were also collected
and studied. The following types of homo-
geneous waste woods were collected and
analyzed:
• plywood
• CCA pressure-treated wood
• particle board
• creosote-treated wood
• furniture scraps
• laminated wood
Environmental Impacts of
Waste-wood Combustion - Air
Emissions of heavy metals, sulfur, and
chloride from the combustion of waste
wood in boilers can be approximated us-
ing wood and ash concentration data de-
veloped for this study. These data, and
conservative observations about partition-
ing these compounds between bottom and
fly ash, can be used to estimate air emis-
sions. Worst case assumptions about the
partitioning (e.g., 100% of metals are con-
tained in the fly ash) can be used for
overestimates of emission rates; however,
emissions of organic compounds cannot
be estimated from wood and ash compo-
sition data.
Actual emissions data from testing ex-
isting wood boilers have been compiled to
supplement the wood and ash concentra-
tion data gathered for this study. While
emissions data for criteria pollutants such
as particulate matter, nitrogen oxides, car-
bon monoxide, sulfur dioxide, and total
hydrocarbons were obtained, this study
focused on non-criteria pollutants such as
metals and various organic compounds
that are regulated as hazardous air pollut-
ants (HAPs) by most state agencies.
In the absence of HAP emissions data
for wood boilers, regulators have used
test data from residential wood combus-
tion appliances to quantify emissions. Al-
though these data may be useful in identi-
fying the types of pollutants that may be
products of wood combustion, the emis-
sion rates from industrial wood-fired boil-
ers are significantly lower due to the dif-
ferences in combustor design, combus-
tion efficiencies, and operating conditions.
The overall objective of compiling emis-
sions data for this project, therefore, was
to summarize available HAP emissions
data that are more applicable to commer-
cial or industrial wood boiler facilities.
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Richard S. Atkins is with Environmental Risk Limited, Bloomfield, CT 06002 and Christine
T. Donovan is with C. T. Donovan Associates, Inc., Burlington, VT 05402.
Robert C. McCrillis is the EPA Project Officer (see below).
The complete report consists of two volumes, entitled "Wood Products in the Waste Stream-
Characterization and Combustion Emissions."
Volume 1. "Technical Report," (Order No. PB93-198950; Cost: $49.00, subject to
change).
Volume 2. "Appendices," (Order No. PB93-198968; Cost: $28.00, subject to change).
The above reports will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Air Pollution Prevention and Control Division
National Risk Management Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
United States
Environmental Protection Agency
Center for Environmental Research Information
Cincinnati, OH 45268
Official Business
Penalty for Private Use $300
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POSTAGE & FEES PAID
EPA
PERMIT NO. G-35
EPA/600/SR-96/119
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