x°/EPA
United States
Environmental Protection
Agency
Industrial Environmental Researc
Laboratory
Research Triangle Park NC 2771
Research and Development-
EPA-600/S7-81-108 Aug. 1981
Project Summary
Assessment of Hazard
Potential from Combustion of
Wastes in Industrial Boilers
James W. Harrison, James B. White, and William J. King
The Resource Conservation and Re-
covery Act of 1976 encourages the
conservation of valuable resources,
including energy, consonant with the
protection of environmental quality.
Recently promulgated hazardous
waste regulations allow the onsite use
of wastes as fuels with few restrictions.
In response EPA's Office of Solid
Waste has asked for comment and
advice on this matter. The present
study was undertaken to determine
the extent of the present onsite use of
waste fuel in industrial boilers and
related process equipment, the nature
and quantities of the materials so
disposed, and the current regulations
concerning such use.
Based upon contacts with Federal,
State, and local environmental pro-
tection officials as well as industry
personnel and the open literature, this
study concludes that: a wide variety of
materials have been burned as fuel in
standard or appropriately modified
combustion equipment; the practice
can be expected to expand due to the
economic pressures of hazardous
waste disposal and rising fossil fuel
costs; virtually no emission data on
waste fuel combustion (except through
incineration) is available; under condi-
tions of inefficient combustion, signif-
icant paniculate matter and high
molecular weight (including polycyclic
organic compounds) emission rates
can be expected; and, finally, within
the scope of this study, no current
regulations were found to ba directed
specifically at waste combustion.
Recommendations for increased
industry contacts, representative site
selection, and a field program in con-
junction with a coordinated regulatory
program to ensure the environmentally
safe use of wastes as fuel are made.
This work, under Contract 68-02-
3170, Work Assignment 21, was
carried out between June 5, 1980,
and September 30, 1980.
This Project Summary was devel-
oped by EPA's Industrial Environ-
mental Research Laboratory. Research
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 and Summary
The Resource Conservation and Re-
covery Act of 1976 (RCRA) has among
its objectives "to promote the protection
of health and the environment and to
conserve valuable material and energy
resources." In formulating and promul-
gating regulations for classifying and
dealing with hazardous wastes, EPA's
Office of Solid Waste has deemed the
recovery of energy from waste combus-
tion to be consonant with Congressional
intent as expressed in the RCRA.
Specifically, Part 261 of Title 40 of the
Code of Federal Regulations defines
solid waste in a manner that excludes
material burned as fuel for the purpose
-------
of energy recovery. The regulation also
includes criteria for determining whether
or not solid wastes are hazardous. The
effect of the exclusionary definition of
solid waste is to allow ignitable materials
which would otherwise be classified as
hazardous to be regarded as nonhaz-
ardous if they are burned onsite as fuel
for energy recovery.
The RCRA-based testing, classifying,
handling, transporting, and disposing of
hazardous waste will be complex,
troublesome, and an additional cost
item for every generator of such wastes
in the nation. It is therefore anticipated
that a significant change in disposal
practice may occur. Many wastes which
were previously discarded may now be
burned in an attempt to qualify under
the exclusionary definition. These wastes
could include synthesis process wastes,
solvents, lubricants, and other organics.
A further stimulus to such use is the
escalating prices of the conventional
fossil fuels that have heretofore been
used almost exclusively for energy
production. Any materials which can
supplement fossil fuels, at lower costs
per Btu, will be seriously considered for
use.
The Office of Solid Waste (OSW) is
aware of the many possible consequences
of the combustion allowed under the
present exclusion, and it plans to begin
consideration of the problems of spent
solvents and waste oil in the fall of 1980
ana of organic chemical process residues
in the fall of 1981. OSW has invited
comments on such further regulations
and has specifically solicitated informa-
tion dealing with combustion of wastes
in industrial boilers. It is in response to
this solicitation that the work being
reported was undertaken.
EPA's Office of Air Quality, Planning
and Standards (OAQPS), in conjunction
with the IERL-RTP and lERL-Cinn. of
EPA's Office of Research and Develop-
ment (ORD), has initiated a program to
collect information on the current prac-
tice of waste-burning in industrial
boilers and other process heating equip-
ment, the types and quantities of mate-
rials burned, the state of the art of
technology for waste combustion and
waste/fossil fuel co-firing, and the
current environmental regulations and
policies of State and Federal environ-
mental protection organizations. In
addition to the assessment of current
waste combustion practices, there are
also plans to assess how waste com-
bustion in industrial heating equipment
might be carried out in the future under
various regulatory scenarios that will
encourage the complete use of suitable
materials for energy recovery commen-
surate with adequate safeguards for
human health and environmental quality.
The purpose of this initial work in the
OAQPS/ORD program is to scope the
problem and make recommendations as
to what should be done by EPA to meet
its responsibilities in respect to the
objectives of the RCRA.
It must be emphasized that the in-
formation reported here in no way
represents an exhaustive survey. The
intent was to collect enough data from
several Federal and State sources as
well as from prior reports and the open
literature in order to obtain (1) an idea of
what kinds of materials might be used
for fuel, (2) an order of magnitude
estimate of the quantities of these
materials used in industry, (3) some
indication of how these materialsare, or
might be, burned as a fuel in standard
industrial combustion equipment, and
(4) what air quality impacts might be
expected.
An additional purpose was to find out
on the basis of a limited survey how
current environmental regulations are
being interpreted by Federal and State
enforcement officials with regard to
such waste burning and how those
officials felt that they might be, or
should be, regulated in the future.
Waste Materials As Fuel
Problems with waste as fuel derive
mainly from the unknown, highly vari-
able nature of waste matter. In order to
determine the proper type of combustion
system for use with a particular waste,
many properties are of interest;, but in
an initial screening, the most important
of these are physical state, heat content,
and fuel-borne contaminants.
Before a waste can be burned as a
fuel its physical state must be suitable
for a particular burner type. Physical
state is normally classed as gaseous,
liquid, or solid. When dealing with
waste, however, the difference between
solids and-liquids is frequently not clear
cut. As in the case of still bottoms from
solvent reclamation or the chemical
industry, physical state is often depen-
dent on the process and how much
liquid the industrial processor chooses
to leave behind. The distinction between
liquids, semi-solids, and solids is there-
fore made on the basis of viscosity. To be
considered a liquid, a waste must be
pumpable at ambient temperature or
should be capable of being pumped after
being treated to some reasonable tem-
perature (204°C -260°C). This normally
restricts the viscosity of the waste to
less than 10,000 ssu and solids content
to 70 percent by weight.
Next, a waste must have a high
enough heat content to develop and
sustain combustion reactions and
maintain required boiler temperatures.
The heat content of waste gases can be
grouped as High Btu—>5.59 MJ/m3
(>150 Btu/ft3), Medium Btu—3.73-5.59
MJ/m3 (100-150 Btu/ft3), or Low Btu—
<3.73 MJ/m3 (<100 Btu/ft3). The heat
content of liquids and solids can be
grouped as High Btu—23.26 MJ/kg
(>10,000 Btu/lb), Medium Btu—11.63-
23.26 MJ/kg (5,000-10,000 Btu/lb),
and Low Btu—<11.63 MJ/kg «5,000
Btu/lb). This grouping is only an indica-
tor of a waste's fuel potential. Some
liquids with thermal values as great as
23.26-25.59 MJ/kg (10,000-11,000
Btu/lb) are incapable of sustaining
combustion, while other wastes with
values as low as 10.47 MJ/kg (4,500
Btu/lb) have been burned unassisted.
Lastly, a waste must be relatively
clean in order to burn properly. After
physical state and heat content, fuel-
borne contaminants have the greatest
effect on the quality and efficiency of
combustion. Contaminants in gaseous
organic waste include particles, inor-
ganic gases, and water vapor. Panicu-
late matter can foul burner tips and
erode mechanical surfaces, while the
presence of other gases can affect the
limits of flammability of the waste.
Solids, metals, water, and inorganic
liquids are the most common contami-
nants of organic liquid wastes. Not only
do water and other liquids require
energy to vaporize, but the relative
differences in specific gravities can
cause the mixtures to stratify in holding
tanks and fuel lines. Chemical reactions
cause precipitates to form or can cause
polymerization to occur which may
affect feed rates. Solids suspended in
the liquid waste can also erode or clog
burner tips and control devices.
Metals create problems in both solid
and liquid waste fuels. If a burner
operates at temperatures greater than
the fusion point of the metal, oxides, or
carbonates, slagging and fouling can
occur. Metals can also form eutectic
mixtures on refractory surfaces and
promote corrosion at temperatures
much lower than would otherwise be
expected.
-------
Hydrocarbons such as waste oil and
waste solvent are likely candidates for
combustion in industrial boilers. Waste
oils, however, are apt to contain con-
taminants which can pose environ-
mental as well as combustion problems.
Approximately two-thirds of the U.S.
waste oil comes from the crank cases of
automobiles and trucks and contains an
estimated 1 percent by weight lead as
well as other toxic materials. Pretreat-
ment prior to use is generally required
since waste oils frequently contain
sludge, grit, solvents, w^ater, heavy
metals, and additives added during
processing. Usually, however, this
involves only the removal of water and
solid particles by gravity settling and/or
filtration.
Waste solvents are generally contam-
inated with suspended and dissolved
solids, organic matter, organometallics,
or other solvents. Normally the contam-
inants compose less than 10 percent of
the solvent. Industries that produce
waste solvent include the drug industry,
solvent refineries, vegetable oil extrac-
tion, polymerization processes, and
cleaning operations. Fuels derived from
these hydrocarbon solvents are markedly
different from petroleum oil in chemical
' and physical properties. They differ in
flow characteristics, air/fuel ratio,
pumping requirements, and pressure
requirements in general. Since they
have a lower viscosity than fuel oils,
liquid hydrocarbons require lower pres-
sure for movement and atomization and
this can therefore affect any preset feed
rate. The heat content is also variable
and often, in order to achieve the
temperature and steam pressures re-
quired for plant processes, more of the
hydrocarbon must be used than normally
required.
The single largest group of solvents
used in industry are halogenated sol-
vents. Approximately 26 percent of the
205,000 metric tons of dirty solvent
reclaimed in 1974 were either chlori-
nated or fluorinated solvents. Physically
these solvents tend to behave like their
hydrocarbon counterparts; however,
marked differences are seen in the heat
contents. The heating value of these
wastes decrease as the percent by
weight of the halogen constituent in-
creases. This has been attributed to the
flame retardant effects of the halogen
atom. For example, chlorinated com-
pounds with a concentration greater
than 70 percent by weight chlorine can
require art auxiliary fuel source in order
to sustain combustion.
The use of halogenated waste as fuel
also presents problems with corrosion
in the boiler and in the heat recovery
devices. Care must be taken to maintain
the combustion products which are rich
in halogen acids above their respective
dewpoints in order to prevent conden-
sation and corrosion. This fixes the
minimum temperature in the heat re-
covery devices and thereby determines
the energy available for process streams.
In addition, sufficient hydrogen must be
provided usually in the form of an
auxiliary fuel to permit the combustion
of free halogen gases (such as chlorine
gas) to their respective hydrogen acids.
Otherwise, stress corrosion problems
can occur in the heat recovery units.
Many solid industrial wastes also
have potential for energy recovery. In
industrial situations, the solid waste
component can be varied, but generally
one class of constituents will predomi-
nate. It can consist of semisolid sludges
and still bottoms too viscous to be
handled as liquids or solid discrete
objects such as rubber or plastic straps.
Plastic wastes originate from both the
synthetic and fabrication processes.
These wastes consist of tars and still
bottoms, off-spec product, or shavings
and trimmings. Plastics have heat con-
tents similar to high grade fuel oils.
Burning characteristics vary from plastic
to plastic, and due to their density they
are normally fired as solids. Combustion
is accompanied by physical change
such as charring, melting, or vaporizing.
Polyolefins burn relatively easily and
give off no toxic gases. They do tend to
melt and run off the grates resulting in
molten pools of plastic which burn
under the grates. Polystyrene degrades
at 482°C with high heat release that can
lead to incomplete burning. Polyvinyl
chlorides (PVC) behave similarly to
halogenated solvents. Although high in
heat content, the presence of the halo-
gen atom retards flame and requires the
use of an auxiliary fuel to sustain
combustion. In addition, the high chlo-
rine content can generate large quanti-
ties of hydrochloric acid or chlorine gas.
It has been estimated that 50-lb of
hydrochloric acid is generated for every
100 Ib of PVC consumed.
The heat content, flammability limits,
flash point, and ignition and auto-
ignition temperatures generally govern
the choice of waste as a fuel and its
blend with other fuel in an operating
combustion system. Once injected into
the combustion zone, the thermal de-
struction of a given material is deter-
mined by the partial pressure of the
available oxygen, the combustion tem-
perature (Tc), and the time spent at Tc.
Another parameter that is difficult to
characterize, but essential for complete
combustion, is good mixing (turbulence)
of the fuel with the oxidant (air).
Gases and volatile hydrocarbons can
be well mixed with air during injection
through a burner nozzle to give the most
favorable situation for thorough com-
bustion—the premixed flame. Usually
additional air must be supplied to com-
plete combustion. With many liquids, all
semisolids, and solids, however, pre-
mixing is not achieved. Even though air
might be used (with or without steam) to
atomize or disperse the fuel, there is still
a region which is predominately fuel, an
external region that is oxidant-rich, and
a boundary region in which the combus-
tion reactions are occurring. This is the
situation of a diffusion flame, so-called
because the fuel and oxidant are trans-
ported by diffusion into the combustion
region.
When sufficiently high temperatures
for destruction are not achieved or
maintained for a sufficient period of
time or if there is not sufficient oxygen
present locally, the thermal cracking of
organic compounds (pyrolysis) may be
accompanied by synthesis of higher
molecular weight compounds. For ex-
ample, ethylene pyrolyzed between
480° and 588°C yields propene, butene,
butadiene, ethane, acetylene, and hy-
drogen. Higher olefins or diolefins may
form aromatic hydrocarbons. Even in
the presence of oxygen, pesticides have
been observed to form pyrolysis pro-
ducts. It is conceivable therefore that,
unless a uniformly high temperature is
maintained along with a plentiful supply
of air in the region where the waste is
being injected, additional chemical
species can be created as air pollutants.
Inventories
Over the past several years, the
quantities of various organic materials
suitable for energy recovery have been
estimated in a series of Federal and
State studies. These efforts have in-
cluded surveys of production and sales
data through extrapolations based on
the response to telephone surveys and
questionnaires of a relatively small
number of firms as well as in-depth
surveys and site visits. Although the
"error bars" for more in-depth studies
should be much smaller, the.re is still
much uncertainty about the ultimate
disposal fate of many of the organic
-------
materials used or generated by industry.
A series of overview studies of indus-
trial waste disposal practices were
conducted by the Office of Solid Waste
in the mid-70's. The types of material
generated were specified and the quan-
tities estimated. Technology for treat-
ment and disposal of waste streams
was also surveyed.
Information developed in these as-
sessments has been subsequently used
in further EPA studies of the issue of
energy recovery from waste burning. A
recent engineering study conducted for
OSW examined the energy conversion
potential of industrial waste streams.
Using the generation of low pressure
(125 psi) steam as the energy recovery
medium and defining a heat content of
18.4 MJ/kg (about 8,000 Btu/lb) as the
threshold for practical recovery, the
study proceeded to identify five indus-
trial categories as having sufficient
waste heat potential to justify more
detailed study on methods of implemen-
tation. These industries and waste
quantities are: organic chemicals, 1.5
million metric tons; plastics, 0.445
million metric tons; petroleum refining,
0.110 million metric tons; drugs, 65,000
metric tons; and tires, 31,000 metric
tons.
lERL-Cincinnati has compiled an
inventory of used and byproduct hydro-
carbon streams which includes volatile
orcianic constituents (VOCs), waste oils,
and solvents. Semisolids, sludges, and
solids were not included. This study
concluded that petroleum refineries
were the only major industry with
substantial recovery potential for VOCs,
with an estimated 8.9 x 105 metric
tons/year recoverable. Using data from
previous reports, the study estimated
that about 2.8 x 109 liters/year of
automotive lubricating oils and 5.4 x109
liters of industrial oils (of various types)
were generated in 1977. The energy
content of these oils ranges from 31.5
MJ/kg to 44.7 MJ/kg (13,000 Btu/lb to
19,300 Btu/lb). The ultimate fate of
most of this oil is not known.
lERL-Cincinnati also estimated the
1978 demand for solvents, to be 1.39 x
106 metric tons/year of halogenated
hydrocarbons, 1.45 x 106 metric tons/
year of ketones, and 1.53 x 106 metric
tons/year of alcohols, giving a total of
about 4.37 x 106 metric tons/year. A
previous EPA source assessment of the
solvent reclaiming industry has esti-
mated that only a little over 2 percent of
solvents are reclaimed.
Many states have completed surveys
to determine the types, rates of genera-
tion, and disposition of hazardous wastes
within their jurisdiction. The data from
these surveys is useful in understanding
the patterns that recently existed. How-
ever, how these patterns might change
under the impetus of new hazardous
waste disposal regulations is moot. As
might be expected, the units used and
the degree of detail vary considerably
from state to state. There are also
considerable differences in the reported
details of disposal practice. Some of
these surveys are sketched below.
The State of New York has conducted
an extensive survey contacting some
1,170 generators out of an estimated
4,000. More than 90 percent of the
firms contacted responded. The total of
1.0 x 105 metric tons/year of waste
accounted for in the survey was esti-
mated to represent 90 percent of that
actually generated in New York. Six
groups of industries in the state account
for more than 75 percent of the annual
hazardous waste production: organic
and inorganic chemicals, primary metals,
plastics, petroleum refining, and phar-
maceuticals. The New York survey
provides an in-depth view of the types of
waste generated by the various indus-
tries in the stateand how these materials
are disposed of.
The State of North Carolina conducted
a survey of hazardous waste generation
in the state in 1978 and collected data
by site visits to selected facilities repre-
sentative of the major industries of the
state.
The State of Illinois has also conducted
a thorough survey of industrial waste
generation and disposal practices. Out
of 21,000 industrial establishments
queried, 7,900 responded. These rep-
resented 62 percent of the industrial
employees in Illinois.
The State of California is in the
process of conducting an inventory of its
hazardous wastes and the State of
Maryland has also recently instituted
procedures to collect similar data.
The State of Massachusetts has for
some time maintained an inventory of
hazardous wastes collected by licensed
waste handlers which provides the
basis for understanding the pattern of
generation of waste in the state.
Current Disposal Practice
Information on current disposal prac-
tices and trends was obtained from
three sources: Federal, State, and
private industry reports and contacts.
The main points from each of these
sources are surveyed in this section to
indicate the pattern of information
developed during this initial phase of
study.
The Federal studies have been avail-
able for some time and were briefly
discussed earlier. Further discussion is
not warranted in this brief summary.
Published reports of state hazardous
waste inventories and disposal practices
were used, as well as telephone con-
tacts with state and local environmental
protection officials, in an effort to
develop more detail on the burning of
hazardous wastes for energy recovery.
Although the-quantitative detail was far
from what is needed to accurately
assess the magnitude and the impacts
of the various disposal practices, the
information developed was useful in
highlighting the enormous variety of
such practices.
In New York State, material "reclaimed
for fuel or material value," constitutes
about 26.5 percent of the waste disposal
onsite. Among these materials, it ap-
pears that the solvent mixtures and
nonemulsified waste oils along with
some portion of the nonhalogenated
solvents are likely candidates for cofiring
for energy recovery. If so, some 90,000
m3 of supplementary fuel at a nominal
heat value of 28,000 MJ/m3 is available
to industry each year by burning this
waste onsite.
Some plants in New York have applied
for permits to burn waste solvents, oils,
or both as fuels.
As specific examples of use [1]:
One plant operates a coal-fired, ce-
ment wet process kiln with a nominal
firing rate of 5 tons per hour of 12,500
Btu/lb coal. Particulates are controlled
by an electrostatic precipitator. Since
1976, this company has been blending
in waste solvents such as ketones,
alcohols, acetates, and benzenes which
contain colloids (paint sludges). In 1978
some 1,600 m3 (422,000 gallons) of
such solvents with a heat content
ranging 27.9 MJ/kg to 41.8 MJ/kg
(12,000-18,000 Btu/lb) were burned at
a rate of 315 cm/3 second (5 gallons/
minute)—about 25 percent standard
fuel (coal) replacement.
A second plant operates two light-
weight aggregate kilns—each with a
capacity of 16.8 metric tons/hour—
using solvents and oil as fuel on a 100
percent replacement basis. The con-
sumption rate is about 2.18 mVhourfor
-------
each kiln. The actual fuel composition is
varied. Typical fuel composition is 96
percent solvents and 4 percent waste
lubricating oil; 35 percent aromatics
(benzene, xylene, toluene); 35 percent
aliphatics (mineral spirits, petroleum
oils, hexane, heptane); 15 percent
alcohols (methanol, ethanol, isopropyl);
5 percent ketones (acetones, MEK,
MIBK); 5 percent esters (butyl or octyl
phthalates); and 5 percent polymeric
resins (alkyds, cellulose). When chlo-
rinated solvents are added, they are kept
to about 2 percent average because of
the corrosion problems they cause in
the scrubber and exhaust fan system.
Each kiln is equipped with an impinge-
ment type scrubber.
In a third plant's lightweight aggregate
kiln, waste solvents are burned at a rate
of about 2.16 mVhour (570 gallons/
hour). These have an average heat
content of 22,300 MJ/m3 (80,000
Btu/gallon). At this plant, halogenated
solvents are also used at about 2 percent
composition. Other constituents and
their composition ranges are: MEK (20-
80 percent); MIBK (0-10 percent); ace-
tone (10-30 percent); toluene (20-80
percent); mineral spirits (5-20 percent);
isobutanol (0-5 percent); methanol (0-
10 percent); ethanol (0-10 percent);
isopropanol (5-15 percent); acetates (5-
10 percent); sulfur (0.2 percent); and
ash (5 percent). Particles are controlled
by an impingement scrubber.
The State of Illinois EPA estimates
that almost 75 percent of industrial
wastes are disposed of onsite; and 22
percent, offsite. Of the materials disposed
of onsite, Illinois environmental protec-
tion officials estimate that 33,000
metric tons are burned as fuel. These
materials include: oils, solvents, dye
and paint sludges, fats-and waxes, and
organic solids.
In Illinois, a permit is required if
wastes are to be burned as fuel. Applica-
tion must be accompanied by an analysis
of the waste, but usually only sulfur and
trace metals content are of concern to
the Illinois EPA air quality officials. Only
a few companies have applied for a
permit. One company planned to burn
solvents, and two were burning fatty
acids and oily residues from vegetable
oil processing.
In the State of Maryland, although
recycling is encouraged, the burning of
waste oils and solvents is not discour-
aged. The state wants a typical sample
analysis along with a sample of the
material to be burned. This is checked
for PCBs and lead. If these are present,
the blend ratio is restricted to reduce
emissions. There are also operating
problems. PCBs corrode precipitators
and lead fouls boiler heat transfer
surfaces. Although at least one firm
collects waste solvents and sells mix-
tures such as MEK and toluene as a fuel
(at reportedly less than 10 cents/gallon),
only one firm has applied to the state for
a permit to burn waste solvents. This is a
printing firm that burns ethyl alcohol
and toluene in a conventional boiler.
This is blended at about 10 percent with
either No. 2 oil or gas. The state suspects
that burning of oil and solvents, both on
and offsite, for energy recovery is a
common practice and will become even
more prevalent, but at present the state
has little solid information on the prac-
tice.
In the State of North Carolina, at least
two organic chemical firms burn process
wastes (DMT sludges) for heat recovery:
a pharmaceutical firm burns solvents,
and a furniture manufacturer has applied
for a permit to burn pretreatment sludge,
scrapings and trash from a paint line,
and wood scrap with natural gas as the
primary fuel in a package boiler. Also,
one resin manufacturer uses fumes
from its process as its sole fuel.
In the State of South Carolina, several
examples of industrial burning of wastes
for fuel were given. An analysis of the
waste, must be supplied to the state
before a permit is issued. One asphalt
plant has tried burning phenols, but
problems occurred and the practice was
stopped by the state. An unspecified
firm received permission for a "one-
shot" burn of 55,000 gallons of tars
from a manufactured gas storage tank.
Another unspecified firm buys "all
burnable material" for energy recovery.
A small secondary aluminum foundry
uses waste oil in its smelting. State
environmental protection officials sus-
pect that a lot of waste oil, solvent, and
other chemicals are being burned in
small boilers, but they have no definite
information.
In the State of Georgia, "two or three"
facilities process waste oil for fuel. Such
reprocessed oil and some solvents are
used as fuel supplements in pulp mills.
This is also apparently common practice
in pulp mills in the State of Washington.
Blends of up to 20 percent reprocessed
lube oil and Bunker C are commonly
burned both in pulp mill boilers and in
cement kilns. One oil reprocessor esti-
mates that 95 percent of the motor oil
reclaimed in the Northwest is burned in
boilers, and most of the rest is used on
roads.
In the State of Oregon, one firm was
reported to be burning shredded rubber
tires and wood waste for energy recovery,
and two tallow firms were reported to
use waste oil for their process heat
units.
The heavy concentration of petro-
chemical and refining firms in the State
of Texas and the needs for process heat
in such operations make this state a
prime target for a study to determine the
nature and extent of such practices. The
Texas Air Control Board (TACB) has no
regulations concerning cofiring but
uses federal regulations which require
permits from appropriate state or local
agencies. Through these permits, in-
formation is available concerning pre-
sent practice. For example: one utility
has applied for permission to burn PCB-
contaminated mineral oil in a high
efficiency boiler; a coal tar plant is
burning waste creosote for heat recovery;
several chemical plants recover heat
from fuels obtained from the pyrolysis of
waste streams that were previously
landfilled; another burns vinyl chloride
monomer and ethylene dichloride
process wastes in a vapor/heavy liquid
incinerator equipped for energy recovery;
still another chemical plant is installing
incinerators with waste heat boilers to
recover energy from burning waste
chlorinated and other hydrocarbons; at
least three chemical plants are inciner-
ating PVC with heat recovery; and yet
another cof ires waste gases and organic
liquids in high efficiency boilers. Even
with these examples, TACB believes
that the tempo of such waste burning
will not change much in the future, but
that industry will try harder to suppress
waste generation or will try to recycle as
many materials as possible rather than
burning them for energy recovery.
The State of Massachusetts, through
a manifest system which has been in
operation for several years, has compiled
an inventory of the flows and disposal
methods for hazardous wastes generated
in the state. This was mentioned pre-
viously. Currently, it is estimated that
much of the waste oil and about one-
third of the solvents collected by waste
handlers in the state are used for fuel
either in the state, or in one of the
surrounding states. Much of this mate-
rial is burned in'small boilers supplying
heat to greenhouses. One large brick
manufacturer was using large amounts
-------
of waste oil in its kilns but recently
applied for a permit to switch from oil to
coal for its operations. Since the state
does not require permits for such waste
cofiring, there is no definite information
on the extent of the practice. However, it
is suspected to be widespread now and
should be even more so in th'e future.
A survey of the open literature over
the past decade or so did not yield a
large amount of information that would
provide a definitive picture of current
industrial practice. There is enough,
however, to indicate that the technology
has been steadily developing under the
impetus of rising fuel prices and stricter
waste disposal regulations.
The American Society of Mechanical
Engineers (ASME) has for many years
charged a Research Committee on In-
dustrial and Municipal Wastes (RCIMW)
with the responsibility of identifying
important research problems, sponsor-
ing surveys, research and prototype
installations and coordinating seminars,
and organizing conferences and similar
professional activities to exchange
information and stimulate professional
interest in the solution of the problems
associated with environmentally sound
waste reduction. This committee has,
among other activities, produced reports
on the thermodynamic properties of an
enormous variety of materials to aid the
design calculations of combustion en-
gineers [2,3], produced reports on state
of the art waste disposal installations
[4], and published the proceedings of a
conference on the status and research
needs of energy recovery from wastes
[5]. This committee also coordinated the
ASME response to OSW's proposed
hazardous waste regulations.
A paper presented at the 66th meeting
of APCA (1973) [6] gave an overview of
burning wastes in industrial boilers. The
physical properties and heat content of
various industrial wastes were discussed
and several methods of burning with
heat recovery were described. A recent
paper [7] has described the use of crude
tars from the coking process in a steel
plant to routinely replace Bunker C as
the backup fuel for conventional boilers
generating steam at 400 psi and 600
psi.
The use of package boilers to burn
gaseous, liquid, and solid wastes as
fuels has been described [8]. The author
has cited the environmental advantages
of such combustion over landfilling—
assuming, of course, that complete
combustion occurs. However, this au-
thor also points out that many of the
wastes will produce effects that require
proper design and maintenance to keep
under control. Some wastes will require
frequent sootblowing, or hand lancing
and scrubdown to remove deposits, to
reduce corrosion, and to maintain effi-
cient heat transfer. These maintenance
procedures will produce solid/liquid
waste streams that must be tested with
respect to the hazardous waste criteria
to determine classification and proper
disposal.
Solid-waste fuels have been burned
in industry for years [9]. The most
economical situation occurs when the
solid waste is burned as a supplemental
fuel in an existing boiler. The most
versatile design for such firing Is the
spreader stoker. Suspension firing is
also possible but requires that the waste
be finely divided to achieve total com-
bustion. These authors also discuss
new boiler designs for waste burning.
Considerations attendant to the retrofit-
ting of industrial boilers to accommodate
different fuels, including wastes, have
also been discussed [10].
A final example of some of the solid
wastes that could be expected to be
burned in industrial boilers is seen in
the test firing of a variety of solid wastes
(and some liquids) from-the rubber
industry in a small (20,000 Ib steam/
hour at 150 psig) batch-fed reciprocating
grate stoker. The unit was designed to
burn reject linoleum and roofing tar
paper from a production plant with.a
secondary fuel (oil) burner mounted
well above the grate. For the test burn,
the various kinds of scrap were either
mixed or individually injected in batch
fashion. The intermittent batch feed
caused sudden overload, resulting in
smoking that cleared toward the end of
the cycle: shredding and continuous
feeding reduced emissions. Test effi-
ciency was about 50 percent, although
it was suggested that 60 percent effi-
ciency could be attained with continuous
feed [11].
There .appears little doubt from the
previous survey that the burning of
waste materials by industry for energy
recovery is a viable growing practice.
Large quantities of materials that have
been landfilled or collected and trans-
ported to another location for dumping,
with or without containment, will be-
come increasingly diverted to onsite
burning. The increasing cost of fuel and
the cost of offsite disposal are both
"drivers" to this practice.
\
The combustion technology—design,
construction, and operating technique—
for waste fuel burning, either as a
primary fuel, secondary fuel, or as a
more or less constant blend, is well
established. There is sufficient operating
practice base to encourage further
exploration and use. Boiler and burner
equipment manufacturers are aware of
most of the attendant operational prob-
lems as well as the techniques for
getting around or "living with" these
problems.
Emission Data
Quantitative data are required to
assess the potential pollutant emissions
and the effectiveness of various control
methods in reducing such emissions to
acceptable levels. This data should
relate pollutant species and emission
rates to waste feed composition, com-
bustion conditions, and control methods
employed. At present, information on
emissions from the combustion of
waste materials in industrial boilers is
very limited.
There have been many studies of the
emissions from various kinds of waste
burned in incinerators. These combus-
tion conditions are generally quite
different from those obtained in indus-
trial boilers, so direct extrapolation is
not possible. However, such data on the
species evolved can be used as a guide
to some of the pollutants to be expected.
Tests were run on the combustion of
waste oil and No. 2 distillate blends at
Aberdeen Proving Ground early in the
1970's [12]. The waste oil was drained
crankcase oil from commercial-design
vehicles with traces of antifreeze,
hydraulic brake fluid, and transmission
fluid (in addition to water). Upon com-
parison of emissions obtained from
burning No. 2 fuel oil and blend of No. 2
with 27 percent waste oil in three low-
pressure, rotary-cup burners, it was
found that there was a fivefold increase
in particulate matter emissions. The
trace metal emissions increased from
44-fold to several hundredfold. A report
sponsored by EPA provided data from
seven different installations on lead
emissions from waste oil blended with
coal, No. 2 oil, No. 6 oil, or (as in one
case) burned alone [13]. The fraction ol
lead emitted in the flue gas as a percent
of the lead feed rate was found to range
from about 25 percent to over 50 per-
cent.
Tests on blends of various fuels,
designed to assess the problems ol
-------
burning industrial wastes in conven-
tional boilers [14], have produced data
on the relationship between particulate
emissions and volume percent 02 in the
stack gas from the combustion of four
fuels: naphtha, a heavy oil with a high
pour point (>150°C) denoted HPP, a
blend of naphtha and HPP, and a residual
oil.
The results generally agree with
those reported by several authors that,
with the burner designs and oil fuels
typically used in industrial boilers, the
particulate matter emissions generally
decrease as the excess air is increased.
An incineration system for atactic
polypropylene combined with a waste
heat boiler for energy recovery has been
described [15]. The system hearthburns
the polymer to pyrolyze the solid. Typi-
cally, the system operates at 922 K-1,
144 K, although a maximum of 1,367 K
could be achieved. The pyrolysis gases
are mixed with air at about 25 percent
excess of stoichiometric requirements.
The plastics may produce HCI and P205
as combustion products. Ash content
varies, but could be as high as 10
percent. The temperatures in the pyrol-
ysis zone and entering the heat recovery
boiler are kept below the ash fusion
point to avoid surface fouling.
In a study performed many years ago
on coal, oil, and gas-fired combustion
units, as well as incinerators, Hange-
brauck and coworkers found that under
certain firing conditions significant
amounts of polynuclear hydrocarbons
could be generated [16], It was found
that polynuclear emission rates were
generally large when CO and total
gaseous hydrocarbon emissions rates
were large, indicating incomplete com-
bustion. When benzo(a)pyrene (BaP)
was used as an indicator, a consistent
increase was demonstrated in polynu-
clear emissions proceeding from the
high efficiency pulverized coal units to
the low efficiency hand-stoked home
heating units. BaP from oil-fired units
was generally much lower than from
coal-fired units, but significant amounts
of polynuclear materials were generated
m an oil-fired unit that used a low-
pressure air atomizing burner.
This brief survey indicates that,
although particle emission data and
some trace metal emission data exist,
they are insufficient to prepare a proper
guidelines document and not nearly
adequate enough to form a basis for
setting standards. There are little or no
data available on hydrocarbon emis-
sions, particularly fhe higher molecular
weight species that are suspected of
posing potential health risks. It is well-
known that a sequence of pyrolytic and
synthetic reactions can occur in flames
to produce polycyclic molecules [17],
particularly where the hydrocarbon fuel
is not well mixed with air; i.e., in
diffusion flames that are typical of liquid
combustion.
In the ASME response [18] to EPA's
proposed regulation on incineration, an
example was cited of sampling for
hydrocarbon emissions from a 190
million Btu/hr industrial boiler cofiring
coal and chemical process wastes.
Practically no volatiles (Ci to C6 hydro-
carbons) were observed, and the gas
chromatographable (C7 to Ci6 hydro-
carbons) fraction amounted to only
about 5 percent of the organics. It was
noted that most of the heavy hydrocarbon
emissions condensed in the sampling
lines rather than passing through to be
deposited on a cartridge of XAD-2 resin
for subsequent GC analysis. There is a
serious need for careful sample acquisi-
tion and analysis procedures to be used
to ensure that representative hydro-
carbon emission measurements are
obtained.
Most importantly, data on particulates,
organic species, and trace metal emis-
sion rates should be correlated with an
analysis of the feedstock and combustion
conditions. The effects of the variation
in feedstock composition, boiler loading,
and excess air (or equivalently, stack
gas Oz) on emissions of particles, SO2,
NO,, PNA, and trace metals should be
determined to provide guidance on
permissible waste/fossil fuel ratios
under given conditions. The performance
of standard control devices under these
same variable conditions should also be
ascertained to determine if any pollutants
are not being adequately controlled and
to provide the basis for efforts to improve
performance where needed.
Source Testing
A large variety of materials used or
generated by industry can be burned for
energy recovery. These materials can be
and, in many cases, are burned in a
large variety of combustion equipment.
In view of this multiplicity of combina-
tions, it is difficult to select "representa-
tive sites" for the collection of emission
data to guide the development of regula-
tions. It is also difficult to determine
whether existing regulations can be
adequately applied for air quality protec-
tion.
Because of the meager amount of
emission data available on waste burn-
ing, it appears that the first requirement
for source characterization is a Level 1
assessment of several sources which
span the spectrum of waste utilization.
Once these sources have been char-
acterized and the actual nature of the
environmental problem is assessed, a
30-day (or other appropriate period)
continuous emission testing backed up
by appropriate reference methods and
quality assurance procedures can be
used to obtain legally defensible data for
standards setting.
The "spectrum of utilization" can be
conceptually portrayed by Figure 1. For
a given energy content of waste, the
achievement of high combustion effi-
ciency becomes more difficult as the
physical state of the waste proceeds
from a vapor or a nonviscous liquid up
through a semisolid or viscous liquid.
Similarly, the combustion type will
influence how well the waste is burned.
As seen in Figure 1, suspension firing
gives the best mixing of fuel and air, and
hearth burning, the poorest.
Physical state of the waste is, of
course, only one consideration. Another
is the chemical composition—including
both chemically bound and physically
included species. Another consideration
is how well the source is controlled.
Large coal-fired units are most likely to
have ESP or fabric filtration units to
provide efficient particle collection
whereas small units may have none at
all. A further consideration is how much
waste material is being burned or, more
properly, what the total pollutant emis-
sions are over a given period.
A tentative priority listing that would
lead to site selection is:
1. Sources burning off-spec resins or
plastics or rubber industry wastes
in a batch-fed mode.
2. Sources burning semisolid or vis-
cous chemical processing wastes
on a continuous or piecewise
continuous basis.
3. Sources burning waste lubricating
and/or cutting oils on a continuous
or piecewise continuous basis.
4. Sources burning waste solvents
from metal or semiconductor
processing operations on a con-
tinuous or piecewise continuous
basis.
The presumption made in this listing is
that incomplete combustion presents
the most severe environmental hazard
through polycyclic organics. Also the
-------
Organic Waste State
Combustor Type
Semisolids and
Viscous Liquids
Shreddable or
Friable Solids
Oily Liquids
Nonviscous Liquids
Vapor
Hearth Burning
Batch Mode Underfed
Stoker
Overfeed, Chain or
Moving Grate Stoker
Spreader Stoker
Suspension Fired
Figure 1. , Qualitative comparison of organic waste state and combustor
type in achieving high combustion efficiency.
burning of products (plastics and rubber
goods) that contain a variety of fillers
and additives offers more possibility of
inorganic emissions than those expected
from, say, settled or filtered lube oils or
solvents.
Control Technology
When waste materials are burned for
energy, the basis for sound environ-
mental control is to ensure that:
1. Complete combustion occurs.
2. Fly ash, particles, pollutant gases,
and hazardous vapors emitted to
the atmosphere are reduced to a
predetermined safe level.
3. Air emission control device residue
is properly classified and disposed
of.
4. Solid residue (bottom ash) is prop-
erly classified and disposed of.
Additional fuel handling steps prior to
combustion must also be considered
when planning an overall control strat-
egy. If the waste contains VOC, the
processing steps must occur under
conditions where the volatiles are not
allowed to escape to the atmosphere.
This has three advantages: (1) air quality
is preserved, (2) material with significant
heat content is reserved for burning,
and (3) the safe operation of the plant
(prevention of fire or explosion) is
maintained. In addition, if the waste is
treated prior to combustion to filter out
or chemically complex and settle out
sludge, the bottom waste from these
processes must be adequately handled.
For complete combustion there must
be adequate air, the fuel and air must be
thoroughly mixed (turbulence), the
exothe.rmic reactions of combustion
must provide enough heat to raise the
burning mixture to a high enough tem-
perature to destroy every organic con-
stituent, and transport of the burning
mixture through the high temperature
region must occur over a sufficient time
duration to ensure that even the slowest
combustion reaction has gone to com-
pletion.
Burner designs for liquid wastes must
ensure the adequate vaporization, mix-
ing, and initial combustion of the partic-
ular materials being burned. The waste/
fuel mixture is injected with pressurized
air at a sufficient velocity into a geometry
that promotes turbulence and circulates
some of the high temperature gases
back into the incoming stream to raise
the injected material rapidly toward
combustion temperature. The burning
mixture is then injected into a flame
zone where additional air is supplied to
fully develop the combustion.
The comminution of solid wastes
must be fine enough to promote rapid
charring and facilitate the distribution of
fuel into the combustion zone; e.g., by
overfeed from a spreader stoker or
crossfeed onto a traveling grate. Com-
bustion air must be fed through the char
bed and into the resulting volatiles to
promote temperatures and mixing suffi-
cient to achieve complete combustion.
As with many environmental control
technologies, the proper design to
achieve as complete combustion as
possible also provides operational bene-
fits through:
1. Better fuel use.
2. Less deposit buildup on the cooler
surfaces downstream from the
combustion zone.
The needs of and procedures for the
design and maintenance of proper
combustion process controls are well-
documented. The control system must
provide the proper fuel/air feed ratios
and ensure safe operation. Included in
the safety considerations are flame
failure detection, protective interlocks
for burner ignition, fan operation, fuel
valves, and fuel/air ratio limits. With
regard to the fuel/air ratio, the control
system must limit the fuel feed to
prevent air deficiency: it must phase
down fuel feed ahead of air feed with a
decrease in load, and must phase up air
feed ahead of fuel feed with an increase
in load.
If the waste fuel is not blended in a
constant ratio with the regular fossil
fuel or if the average heat content of the
waste fuel varies significantly, the
fuel/air ratio required for proper com-
bustion will also vary. This can be taken
into account by using an oxygen analyzer
(of appropriate response time) to set the
feed ratio.
Any guidelines document to promote
the environmentally safe use of waste
materials as fuels must also include a
discussion of and recommended design
practices for state of the art combustion
controls and interlocks. As with other
facets of good environmental design
practice there is also a benefit in this
case. A well-designed and well-main-
tained combustion control'and safety
interlock system can save fuel and
prevent unscheduled shutdowns.
Section 261.4(b)(4) of the Hazardous
Waste Regulations declares that the
following are not hazardous waste (by
definition):
"Fly ash waste, bottom ash waste,
slag waste and flue gas emission
8
-------
control waste generated primarily
from the combustion of coal or other
fossil fuels."
The meaning of the word "primarily"
must be determined in order to specify
the limits of the feed ratios of waste/
fossil fuel under which the exclusion
applies.
These same wastes derived from the
combustion of wood as the primary fuel
could conceivably be hazardous if they
do not pass the EPA toxicity test. Unless
the exclusion is broadened, the solid
wastes from the combustion of wood, or
wood and shredded tires, etc., could
conceivably require handling and dis-
posal as a hazardous waste.
It is doubtful that the combustion of
waste oils and solvents under properly
control led conditions will constitute any
more of a hazard than the burning of
coal or heavy oil. Crankcase oil, cutting
oils, and many solvents are apt to
contain appreciable quantities of metals,
but much of this detritus can be settled
or filtered out prior to combustion. This
not only has environmental advantages,
it has practical operational advantages.
Adequate pretreatment, along with the
state of the art particle controls, would
probably provide effective regulation
where wastes are cofired with coal or
wood. When cofired with oil, however,
there may be more of a problem in
achieving adequate stack gas cleanup.
The lead and other toxic metal content
of the feedstock would need to be
limited to limit emissions.
Current Regulatory Approaches
On May 19,1980, OSW published its
Phase 1 interim final regulations for a
hazardous waste management system.
As discussed previously, the current
definition of solid wastes specifically
excludes material "burned as a fuel for
the purpose of recovering'usable energy."
In commenting on energy recovery,
OSW states:
"The Agency has decided that the
burning of hazardous waste for energy
recovery will not now be covered
under the hazardous waste provisions
of RCRA. (However, storage or trans-
portation of listed hazardous waste
prior to energy recovery is covered by
these regulations.) Accordingly, if
waste oils and solvents are burned as
a fuel in a boiler primarily to produce
steam or usable energy, this action is
not now covered by these regulations."
Whereas the regulation on incineration
requires the achievement of steadystate
combustion by the use of an auxiliary
fuel before wastes are introduced, OSW
comments in another part:
"For example, air emissions generated
by the burning of waste oil for energy
recovery can probably be effectively
controlled without requiring boilers
to meet hazardous waste incinerator
requirements."
The implication appears to be that air
quality regulations should govern the
use of wastes as fuel.
This implication, if true, apparently
contradicts a previous comment:
"The procedures of the Clean Air Act
would be a less efficient way to
control a large number of hazardous
air pollutants than RCRA, under
which design, operation, or perform-
ance criteria (such as incinerator
destruction efficiencies) can be set
more easily for many pollutants emit-
ted by the facilities. Therefore the
Agency has chosen RCRA as the
primary vehicle for controlling air
emissions from hazardous waste
facilities."
In view of this contention and the
previous statement, the burning of
wastes for energy recovery appears to
be an area in which careful coordination
between OSW and OAQPS will be
required.
OSW has specifically listed a number
of solvents as "hazardous waste from
nonspecific sources." Under 40CFR
Part 262 of the new regulations, a
generator who treats, stores, or disposes
of these materials on site must obtain
an EPA identification number and sub-
mit an annual report, unless the total
amount generated is less than 1 metric
ton (100 kg) per month. A generator who
wants to have these substances trans-
ported for disposal elsewhere must
have first obtained an EPA identification
number that is used on a manifest to
identify the generator, type material,
and quantity.
The consequence of the regulations
as currently written is to enable tracking
of a portion of the materials that is apt to
be burned for energy (i.e., those listed
solvents) but to specify nothing about
the conditions under which these mate-
rials will be burned.
OSW is presently studying the problem
of waste oil disposal. Spent solvents are
also under study but lag behind the
waste oil effort. Residues from the
production of organic chemicals will be
subsequently addressed.
At present most states have filed
State Implementation Plans (SIPs) that
specify plans for implementation and
enforcement of regulations to protect
and enhance air quality. None of these
deal specifically with the problem at
hand.
The State of New York requires a
permit to construct and a certificate to
operate sources emitting to ambient air.
The materials to be emitted are classified
with respect to their potential for adverse
health effects and/or environmental
degradation. After classification, a pre-
determined percentage reduction is
imposed based on the uncontrolled
emission rate for the particular pollu-
tants involved. New York's Department
of Environmental'Conservation is cur-
rently considering a change in regula-
tions to specify that anyone who burns
other than fossil fuels must first get a
permit, for which an environmental
impact analysis would be made.
The State of Massachusetts currently
does not require a permit to burn waste
organics such as oils and solvents,
except for mineral oils containing less
than 50 ppm PCBs. A process weight
table is used to specify allowable emis-
sion rates of particles. With respect to
fuels, the state's regulations deal with
fossil fuels except for 301 CMR 7.05 (b)
which deals with fuel additives. These
are defined as "any substance which is
not a natural component of the fuel to
which it may be added or in conjunction
with which it may be used." This part of
the regulations calls for specific written
approval by the Department of Environ-
mental Quality Engineering (DEQE)
prior to use. Apparently this section is
not being construed broadly enough to
include cofiring of wastes. The State
Hazardous Waste Division permits waste
haulers and keeps track of materials,
quantities, where generated, and where
delivered.
The State of Maryland has a specific
regulation dealing with waste oils and
other combustible fluids. Maryland has
been concerned with the burning of PCB
contaminated oil. Their Air Quality
people want to ensure that these are
burned under carefully controlled con-
ditions. The state has a big problem with
liquid organic waste disposal and would
not mind if much of it is burned, as long
as it is done in an environmentally
sound manner.
Except for those sources burning less
than 2.93 x107W (100 million Btu/hr)
of No. 2 fuel oil or less than 7.3 x 107 W
(250 million Btu/hr) of natural gas, the
-------
State of North Carolina requires a
permit which includes a description of
the fuel to be burned. This also covers
fuel changes such as the burning of
wastes.
The State of South Carolina also
requires such notification along with a
sample of the fuel to be burned, which
must be submitted to the state for
analysis. This analysis includes: Btu
content, sulfur, ash, halogens, Pb, Hg,
Cr, V, Cu, Co, Ni, T, Sb, cyanide, and
nitrogen.
The State of Texas requires permit
application for cofiring to be submitted
to the appropriate state or local air
protection agency. Permit data, including
stack tests where performed, are on file.
Ohio has no specific regulations on
cofiring. Standard combustion regula-
tions are used. This has led to enforce-
ment problems. As an example, the
state is in litigation with a firm that has
been cofiring wastes on a No. 2 fuel oil
permit.
The State of Illinois has no regulation
that specifically applies to cofiring. In
contrast with recycling, the practice of
cofiring is not officially encouraged. The
only known permit application has come
from a chemical plant that wants to burn
solvents in a boiler. This is still under
consideration. The state EPA recognizes
that tighter landfill controls will force
cofiring for energy recovery into a
possibly viable option and plans to move
into this area of regulation.
The State of Oregon has no specific
regulations for cofiring. Standard air
quality permit procedures are followed
with variances issued to those applicants
requesting cofiring. To date the state
has encouraged the cofiring of RDF with
other fuels, and will probably do so with
other materials if the practice can be
shown not to degrade air quality.
Wherever feasible, recycling is encour-
aged. The Oregon Department of Air
Quality is closely following a 1 -year trial
in which Georgia Pacific is cofiring
shredded automobile tires and wood
waste at a paper mill in Toledo, Oregon,
in a 7.3 x 107 W (250 million Btu/hr)
stoker-fired boiler. The variance provides
that the tires provide no more than 10
percent of the total heat input; 40
percent opacity cannot be exceeded for
any period greater than 3 minutes and
particle emissions cannot exceed 2
gr/scf.
The current regulatory status con-
cerning waste combustion in boilers
could be fairly summarized as a state of
limbo. Heretofore, the combustion of
waste materials as fired represented
only a very small fraction of the total
material burned, both as fuel and by
incineration. As such, the problem was
minute. Now that there is a strong trend
toward more such combustion, there is
a question as to whether current regula-
tions are sufficient to provide adequate
control to ensure air quality.
This question cannot be answered
until substantially more is known (i.e.,
quantitative data is obtained) about the
waste fuel composition, the conditions
of combustion, the species emitted, and
their dependence on feed and firing
conditions. In addition, there is much to
be learned about the operating practices
and maintenance required to ensure
essentially complete combustion if
guidelines are to be prepared.
In the interim, it appears that enforce-
ment of existing paniculate emission
and opacity regulations are the first line
of air quality defense. Collection of
particles, especially at low enough
temperatures to effect adsorption of
higher molecular weight organics, may
serve to greatly reduce the emission of
metals and polycyclic organic com-
pounds.
Conclusions
The brief survey of existing data and
current industrial waste combustion
practice supports the following conclu-
sions:
1. Waste Inventory Data. Federal sur-
veys have, of necessity, been relatively
aggregated to provide overall estimates
of wastes generated by SIC industrial
categories. Many states have conducted
hazardous waste surveys which provide
more definition of waste types and
quantities, thus giving a better under-
standing of the diversity of materials
that can be burned for energy recovery.
Notable in the survey reported here are
the data available from the States of
Illinois, Massachusetts, New York, and
North Carolina.
In particular, the inventory data of
New York and Illinois offer the best
bases for an in-depth study of current
disposal practice and a projection of
future trends. Both states are heavily
and diversely industrialized, thus pro-
viding a convenient cross-section to
include many of the waste materials
and combustion equipments that are
used.
Using these two states as examples,
the present extent of waste combustion
and a future projection can be compared
In New York, as much a 90,000-100,OOC
m3 of wastes with an energy content o1
28,000 MJ/m3 may be burned annually
onsite as fuel. The rate of organic waste
generation is such that this figure coulc
double. Based on an industry survey ir
Illinois, only 20 percent (8,100 m3 out o'
40,500 m3) of waste oil isacknowledgec
to be annually burned onsite as fuel, as
is only 9.7 percent (2,605 m3 out ol
26,900 m3) of solvents. The other alter
natives for disposal is listed as "recycle/
reclaim." As the price of fossil fue
increases, these percentages will prob-
ably escalate.
2. Combustion Technology and Practice.
A wide variety of waste materials have
been burned in either standard combus-
tion equipment or equipment modifiec
to accept wastes with or without fossi
fuel. The combustion technology base
for increased utilization is available.
Costs of the RCRA manifest system for
tracking hazardous wastes and the
increasing price of fossil fuel can be
expected to push the technology and
practice to make waste use as a fuel an
accepted feature of industrial energy
supply.
3. Emission Data. Virtually no emission
data on waste combustion in industrial
combustion equipment (except incin-
erators) is available. Field tests are
needed to fully characterize sources
burning wastes and provide the basis
for formulating and implementing ade-
quate air quality controls, if needed.
4. Potential Air Quality Problems. Some
organic wastes contain relatively large
amounts of metals or metal-containing
compounds that can volatilize as meta
vapor or oxides, to produce fly ash in
much larger amounts than usual with
fossil fuels. This is supported by the
limited existing emissions data. Ir
addition, many wastes differ appreciably
from fossil fuels in their physical prop-
erties. This can lead to inefficient
combustion with the production of
carbonaceous particles and polycyclic
organic compounds. The latter has not
yet been verified by emissions measure-
ments—as far as could be determined in
the present study— but can be inferred
from the behavior observed when firing
fossil fuels inefficiently in conventional
combustion equipment.
5. Current Regulations. The current
regulatory status concerning waste
combustion in boilers can be fairly
summarized as being in a state of limbo.
Heretofore, the combustion of waste
-------
materials as fuel represented only a
very small fraction of the total material
burned. As such, the problem was
minute. Now that there is a strong trend
toward more'such combustion, there is
a question as to whether current regula-
tions are sufficient to provide adequate
control to ensure air quality.
This question cannot be answered
until much more is known; i.e., quanti-
tative data are obtained on waste fuel
composition, the conditions of combus-
tion, and the species emitted and their
dependence on feed and firing conditions.
In addition, there is much to be learned
about the operating practices and main-
tenance required to ensure essentially
complete combustion if guidelines are
to be prepared.
Many states now have regulations
that require a fuel analysis and notifica-
tion of the state agency before a permit
holder is allowed to burn a significantly
different fuel. There is abundant evi-
dence that requirement is not, and
perhaps cannot, be enforced.
In cases where notification and a fuel
analysis are provided, the states have
generally done some dispersion mod-
eling, looking at SO2 and perhaps lead.
PCB-contaminated oil is a special case:
there has been sufficient publicity,
public arousal, and EPA and state guide-
lines for compliance to be effected.
It is incumbent upon EPA to ensure
that field measurement methods that
develop representative data are made.
The presence of pollutant species must
be proved and quantitated, then health
risk assessments must be made in order
to provide the basis for regulation.
In the interim, it appears that enforce-
ment of existing particulate emission
and opacity regulations is the first line of
air quality defense. Collection of particles,
especially at low enough temperatures
to effect adsorption of higher molecular
weight organics, can serve to greatly
reduce the emission of metals and
polycyclic organic compounds. Whether
or not this is adequate must be decided
on the basis of field measurements.
The regulatory problem is to balance
air, water, and land environmental
quality with resource recovery.
Recommendations
Under the RCRA mandate, EPA has
the responsibility to promote resource
recovery commensurate with the pro-
tection of environmental quality. In or-
der to carry out this responsibility with
regard to the use of waste as fuel, EPA
must provide guidelines to industry to
promote environmentally sound usage
and must formulate regulations, if
needed, to ensure environmental pro-
tection. Fundamental to the preparation
of guidelines and regulations is an
understanding of the technology and
practice, both current and anticipated,
of waste/fossil fuel cofiring, the pollu-
tant emissions resulting from this
practice, and effective methods of
control.
1. Workshop. To promote communica-
tion between industry and EPA, a work-
shop on the environmentally safe use of
waste materials as fuel should be held
as soon as practicable. A proposed
agenda for such a workshop is shown in
Table 1. This event should be well
publicized through industry association
organizations, professional groups such
as NSPE, ASME, and the AlChE, and
state environmental protection officials.
It should be repeated periodically,
perhaps with a symposium format.
2. Disposal Practice Survey. A detailed
study should be carried out with the
cooperation of state environmental
protection officials using air emissions
permit information and hazardous waste
inventory information to develop a list of
specific sources, burning known waste
materials, that are representative of
those SIC classes which can reasonably
be expected to burn significant (with
respect to air quality) amounts of waste.
This study should be confined to two or
three States (e.g.. New York, Illinois, and
Massachusetts). The objective would be
to develop a list of potential test sites to
which selection criteria could be applied
to choose sites for field measurements
that would provide the basis for identify-
ing those waste materials, combustion
conditions, pollutants, andemission
rates that would cause air quality prob-
lems unless adequately controlled.
3. Site Selection. Criteria for selection
of field test sites should be formulated
and applied to the candidate source list.
4. Site Test Plan. Test plans specific to
each selected source should be devel-
oped. These should include screening
type measurements (Level 1) plus any
additional sampling and analysis re-
quired to characterize the source by
relating waste feed composition, com-
bustion conditions, and emissions. In
those cases where the source is known
to be representative of a large group of
similar sources, it may be desirable to
combine the screening measurements
with standard reference method mea-
surements, backed by suitable quality
assurance audits, to expedite future
regulations development.
5. Field Measurements. Actual mea-
surements should be performed accord-
ing to'the test plans atthe selected sites.
6. Environmental Analysis. Measure-
ment data from the field program should
be used to estimate potential health and
environmental impacts due to the ag-
gregate emissions from sources using
wastes as fuel. This aggregate emission
data should be obtained by extending
Table 1. Proposed Agenda for Joint Industry/EPA Workshop on the Environmentally
Safe Use of Waste Materials as Fuel
(All Plenary Sessions)
First Day
Introduction and Welcome (Invited)
Waste Materials as Fuel (Invited)
Combustion Equipment Design and Operation for Cofiring (Invited)
Emissions Measurement (Invited)
Environmental Controls (Invited)
Environmental Regulatory Concerns (Invited)
Second Day
Third Day
Charge to Panels - Plenary Session
Parallel Sessions of Panels on:
1. Combustion Equipment Design and Operation
2. Emissions Measurements
'3. Environmental Controls
Morning Session: Statement of Issues
Afternoon Session: Recommendations on Resolution of Issues
Panel Reports - Plenary Session
Discussion of Reports
Recommendations to EPA
11
-------
the in-depth waste inventory and com-
bustion practice survey to all states in
which waste combustion as a fuel can
•degrade air quality measurably. Control
technology to reduce emissions to
acceptable levels should be identified. If
the necessary control technology is not
available, the needs should be specified
to facilitate necessary research and
development.
7. Combustion Technology Research.
In parallel with the field program, a
research program should be carried out
to elucidate how various equipment
designs and operation parameters will
affect the combustibn efficiency of
various waste materials used as fuel.
This research should take into.account
recent and planned parallel research
efforts by private industry and profes-
sional organizations. The objective
should be a set of designs and operating
practice guidelines to promote the
efficient combustion of organic waste in
industrial boilers and related equipment.
8. Regulatory Analysis. Field data, the
results of the environmental analysis
and combustion technology research,
will provide a series of inputs for EPA's
regulatory offices for air, water, and
land quality. These inputs will enable
those offices to mutually assess the
environmental tradeoffs involved in the
exercise of regulation through their
respective legal mandates. These trade-
off:; should be explicitly comparable in
terms of quantities of pollutants gener-
ated, dispersion mechanisms, and health
and environmental risk analyses.
9. Regulation Preparation. Necessary
regulations would be prepared on a
schedule commensurate with existing
program office workloads and priorities.
The rationale for the recommended
program follows. It is desirable to get
industrial input in an advisory, rather
than an adversary, capacity. Establish-
ment and maintenance of a dialog will
enhance EPA's understanding of the
practice of waste fuel usage as well as
promote industrial efforts to do so in an
environmentally sound manner. The
initial focus on the industrial experience
in two states, the early selection of sites,
and the acquisition of screening data
will provide a better understanding of
the differences between emissions
from wastes and those from fossil fuels.
At the same time, this would generate a
more defensible set of data should a
decision be made early in the program to
press for regulations specific to waste
burning.
In parallel with these elements to
define current practice and its environ-
mental consequences, a program of
waste combustion technology research
would provide the basis for specifying
recommended designs and operational
procedures that would aid industry in
using waste fuels. There has already
been a great deal of research on refuse-
derived fuels (RDF). It should not be
repeated. The materials considered
should be those liquids, semisolids, and
solids that are apt to be generated and
used by industry.
Also, in parallel, the regulatory anal-
ysis element of the program considers
the environmental consequences of
various regulatory approaches. The
view taken is that effective regulation
will most probably take a coordinated
approach between the program offices,
with mutually supportive policies and, if
necessary, regulations.
The regulation preparation portion of
the program could start as early as mid-
1981 if justified by the severity of the
perceived environmental problems. If
not urgent, the regulation countdown
could start late in 1982, allowing the
accumulation of sufficient prior research
and development outputs and the output
of the regulatory analysis phase to set
the stage for the actual preparation and
promulgation.
References
1. Private communication. J. Lauber,
Toxic Unit, NYDEC to J. W.
Harrison, RTI, August 4, 1980.
2. ASME Research Committee on
Industrial and Municipal Waste.
Combustion Fundamentalsfor
Waste Incineration. ASME, New
York, 1974.
3. Thermody-
namic Data for Waste Incinera-
tion. ASME, New York, 1979.
4. Disposal of In-
dustrial Wastes by Combustion.
ASME, New York, Three Vol-
umes.
5. R. A. Matula, editor. Proceedings
of the 1976 ASME Conference
on the Present Status and Re-
search Needs in Energy Recov-
ery from Waste, Hueston Woods
State Park, Oxford, OH, Sep-
tember 19-24, 1976. ASME,
New York, 1976.
6. J. H. Fernandes and L. J. Cohen.
Burning of Waste as Fuels in
Industrial Boilers. 66th Annual
Meeting of APCA, June 24-28,
1973.
7. C. C. Ferguson. Tar Burning on
Boilers at Algoma. Iron and
Steel Engineer, July 1980, pp.
29-32.
8. E. M. Mockridge. Utilization of
Package Boilers for the Com-
bustion of Waste Fuels, pp. 649-
656 in Proceedings of the Am-
erican Power Conference, Vol-
ume 36, Illinois Institute of
Technology, Chicago, 1974.
9. J. H. Fernandes and R. C. Shenk.
Solid-Waste Fuel Burning in In-
dustry, pp. 663-670 in Proceed-
ings of the American Power
Conference, Volume 36, Illinois
Institute of Technology, Chica-
go, 1974. . "
10. W. J. Matthys. Retrofitting Indus-
trial Boilers to Meet the Fuels
Market, pp. 735-741 in Pro-
ceedings of the American Power
Conference, Volume 37, Illinois
Institute of Technology, Chica-
go, 1975.
11. C. A. Hescheles. Industrial Waste
Analysis and Boiler Perform-
ance Test Burning Wastes,
ASME Paper 66-WA/PID-11,
July 1966.
12. M. E. LePera and G. DeBono.
Investigating Waste Oil Disposed
by Direct Incineration. Report
2127, U.S. Army Mobility Equip-
ment Research and Develop-
ment Center, Ft. Belvior, VA,
February 1975.
13. S. Chansky, et. al. Waste Auto-
mative Lubricating Oil Reuse
as a Fuel. EPA-600/5-74-032
(NTIS PB 241357). U.S. EPA Of-
fice of Research and Develop-
ment, Washington, DC, Septem-
ber 1974.
14. H. Ikebe, et al. Some Examples
of Combustion Tests for Putting
New Fuels to Practical Use. IHI
Engineering Review 3(4), 1
(1976).
15. W. Hart. Combustion and Heat
Recovery from Polymeric Ma-
terials, pp. 371-379 in proc.
Conf. on Present Status and Re-
search Needs in Energy Recov-
ery from Waste, Houston, 1976.
New York: American Society of
Mechanical Engineers, 1976.
16. R. P. Hangebrauck, D. J. Von
Lehmden, and J. E. Meeker.
Emissions of Polynuclear Hy-
drocarbons and Other Pollut-
ants from Heat-Generation and
Incineration Processes. JAPCA
14. 267(1964). -
72
-------
17. B. T. Commins. Formation of Poly-
cyclic Aromatic Hydrocarbons
During Pyrolysis and Combus-
tion of Hydrocarbons. Atmos.
Environ. 3, 565(1969).
18. Task Force on Hazardous Waste,
American Society of Mechanical
Engineers. Comparison of Full-
Scale Incinerator Performance
with the EPA Proposed Hazard-
ous Waste Guidelines. January
21, 1980. Submitted to OSW.
J. W. Harrison, J. B. White, and W. J. King are with Research Triangle Institute,
P.O. Box 12194. Research Triangle Park, NC 27709.
Wade H. Ponder is the EPA Project Officer (see below).
The complete report, entitled "Assessment of Hazard Potential from Combustion
of Wastes in Industrial Boilers," (Order No. PB 81-221 889, Cost: $11.00.
subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Industrial Environmental Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
it US GOVERNMENT PRINTING OFFICE. 1981 —757-012/7311
13
-------
1 5
Is
£
o
o
5'
I.
O
I
•t*
(71
to
O>
CO
o
-
t-S
O
K
m > TJ m
w 03
------- |