United States
Environmental Protection
Agency
Industrial Environmental
Research Laboratory
Cincinnati OH 45268
Research and Development
EPA-600/S7-84-023 Mar. 1984
Project Summary
Cogeneration: Status and
Environmental Issues
Benjamin L. Blaney and John Dadiani
The purpose of this project was to
determine the planned cogeneration
development by the utility and
industrial sectors; to assess the
environmental impacts and energy
savings from cogeneration; and, to
identify potential environmental issues
associated with cogeneration develop-
ment. Major emphasis was placed on
environmental impacts. The study
investigated the energy savings and
environmental impacts of five industrial
facilities which are considering a
switch to in-plant cogeneration.
Potential regional environmental
impacts of cogeneration development
in New England, the Tennessee Valley
Authority service area and northern
New Jersey were investigated. Finally,
the environmental impacts of a cogen-
eration-based district heating system
were considered. It was found that
there are a number of factors which
determine the relative magnitude of
environmental impacts of a
cogeneration system compared to a
conventional energy supply system.
These include fuel type, control
technology efficiency and the type of
power source used. As a result, each
cogeneration system must be consid-
ered separately. Generally, it was found
that the most significant environmental
impacts were changes in air emissions;
these increased on-site, but usually
were reduced on a region-wide basis.
This Project Summary was developed
by EPA's Industrial Environmental
Research Laboratory. Cincinnati, OH,
to announce key findings of the
research project that is fully document-
ed in a separate report of the same title
(see Project Report ordering informa-
tion at back).
Introduction
This study examines the potential envi-
ronmental impacts of cogeneration during
the next two decades. Cogeneration, the
simultaneous production of thermal
energy and electrical power, has been the
subject of extensive studies since the
mid-1970's. It has the potential for signif-
icant energy savings for in-plant power
production, industrial energy parks, and
district heating systems.
The objectives of the current study
were to:
• Determine the status of planned Co-
generation development by the
utility and industrial sectors.
• Assess the energy savings and
environmental impacts from
cogeneration
• Identify potential environmental
issues which may impact cogenera-
tion development.
From this investigation, several areas
warranting further study were identified.
The major emphasis of this study is on
environmental issues. A considerable
amount of information is available on the
technical, economic, and institutional
issues associated with this technology,
and those areas are briefly discussed.
The final report upon which this
summary is based, describes the
research and development contributions
of utility, industrial, and government
agencies and personnel to cogeneration;
previous studies dealing with cogenera-
tion and a thorough review of literature
on the subject are also detailed in the
final report.
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Because industry has the best near-
term potential for utilizing cogeneration,
a review was made of five major studies
which project cogeneration development
in the industrial section over the next 15
to 20 years. The review included
combustion technologies currently
available or planned 'for cogeneration,
along with a survey of non-
environmental constraints which might
impede cogeneration systems
development.
The environmental impacts of pro-
posed cogeneration facilities and of
conventional power generating facilities
were analyzed. The environmental im-
pact analysis estimated waste residuals
emitted by cogeneration facilities and
compared them to residuals from conven-
tional power generation systems. In this
part of the study emphasis was on air
emissions; water effluents and solid
waste residuals were also estimated.
The environmental impact analysis
covered five proposed site-specific facili-
ties, and industrial park, and three
studies of regional cogeneration develop-
ment. The results of a case study on
district heating development are also
reported. The site-specific analyses were
made in five energy-intensive industries:
chemicals, textiles, food and kindred
products, petroleum refining, and pulp
and paper production. In the industrial
park study thermal energy was received
from a nearby utility power plant. Two of
the three regional studies examined
industrial cogeneration in utility service
areas: the Tennessee Valley Authority
and the Public Service Electric and Gas
Company in northern New Jersey. The
third regional study investigated the
potential for the use of cogeneration in
commercial establishments in New
England, with emphasis on development
in Massachusetts. The district heating
case study considered the development
of such a system in Minneapolis-St. Paul.
The project developed a simple model
for estimating the national energy
savings that could result from expanded
cogeneration. Recommendations were
also made for future research on the
environmental impacts of cogeneration
development.
Status of Cogeneration
Cogeneration systems are identified
under three general categories' in-plant
systems, industrial complexes, and
district heating systems. In-plant
cogeneration systems produce process
steam and electricity which are used on-
site; any excess electricitygenerated may
be sold to a utility. Industrial complexes
consist of a large, central power plant
(often utility-owned) which supplies
electricity to a grid and process steam to
nearby industries. Industrial cogenera-
tion systems must be within 2 or 3
kilometers of the power plant to keep
piping costs low. District heating systems
typically utilize a large electric generating
power plant which simultaneously
provides Hot water for space heating and
cooling to residential, commercial, and
industrial buildings that are usually
within 10 or 20 km of the generating
plant.
Renewed interest in cogeneration
technology over the last several years is a
result of known benefits of this technol-
ogy. For example, overall energy-use
efficiencies as high as 85% have been
obtained with cogeneration systems,
compared with 30-35% for conventional
systems which provide only electricity.
Cogeneration systems can reduce fuel
consumption, often with reduced
pollution emissions. Economic benefits
arise from reduced capital and operating
costs.
Some disadvantages have also been
identified: increased local pollution
around the cogeneration plant site, and
the need for scarce fuels such as oil for
small cogeneration systems which utilize
diesels.
Steam turbines, gas turbines, and
diesel engines are the most common
combustion devices currently used in
cogeneration systems; and probably will
remain so in the near term (mid-1980's).
Probably, by the end of this decade fluid-
ized bed combustion will be available. In
the 1990's, fuel cells and Stirling engines
may be commercially feasible.
Energy Savings
Estimated energy savings from cogen-
eration have ranged from between 0.60
to 1.83 quads for 1985, depending upon
which industries have been included in
the estimates, to between 1.33 and 3.65
quads by 1990. Much of the energy
savings will be in the form of residual oil,
distillate oil, and natural gas replaced by
coal and process residuals. The
industries in which the major energy
savings are expected to occur are
petroleum refining, chemicals, pulp and
paper, food, and textiles.
Although a few utility companies in the
U.S, (e.g., Gulf States Utilities Co., Texas;
Public Service Electric and Gas Co.,
of New Jersey) have been cogenerating
for decades, cogeneration accounts for
only a small portion of electricity
production nationally. Several studies
have assessed the potential for
cogeneration in selected regions of the
United States. In the Tennessee Valley
Authority service area, an estimated
annual savings equivalent to 1.8 to 6.2
million barrels of oil could be achieved in
the 1989-1998 time period with an
aggressive program to increase cogener-
ation operations. Likewise, in the New
England area, savings estimated at 3.85
million barrels of oil per year in
Massachusetts or 10.1 million barrels per
year throughout the region, could be
realized by the mid-1980's.
Environmental Impacts
A number of factors determine howthe
environmental impacts of a particular
cogeneration system differ from those of
a conventional energy supply system.
The influence of some of these factors
will vary depending upon which of the
three types of generic cogeneration
systems is under consideration; other
factors will have similar effects on all
three systems. It is important to note,
however, that the magnitude of environ-
mental impacts is very site-specific for
cogeneration and therefore each pro-
posed facility should be considered on a
case-by-case basis.
When cogeneration is being
considered as an energy-conserving
replacement, the fuels to be used in the
cogeneration system must be compared
with those used in an existing,
conventional energy system. Manyfuture
cogeneration systems will employ coal in
a new fossil-fueled boiler. Unless highly
efficient pollution control equipment is
employed m such cases, on-site emission
rates will be higher. The same is true
when wood or municipal wastes are used
in the cogeneration system. Since all
three of these "dirtier"fuels require more
efficient pollution controls and generally
have a higher ash content than oil or gas,
their use usually results in a higher
production of solid waste and
wastewater
Even if there is no fuel change or no
boiler modification, a net increase in
emissions at the site of the cogeneration
system combustion unit will result
because the boiler firing rate will have to
be increased to accommodate the addi-
tional load from either steam withdrawal
or electricity production.
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The relative efficiency of pollution
control devices used on system
combustion technologies also will affect
the net change in emissions. However,
conversion to cogeneration is often not
covered by existing environmental regu-
lations. Most in-plant cogeneration units
are so small that they are not covered by
current New Source Performance
Standards (NSPS). Also, changes in the
load factor of an existing boiler are
exempt from Federal Prevention of
Significant Deterioration (PSD) or non-
attainment regulations, although they
may be covered by state permits.
The analyses of five proposed in-plant
cogeneration systems indicated that on-
site air pollution emissions would
increase for each plant. In two cases,
associated reductions in utility emissions
due to reduced fuel use are projected to
offset the increases in cogeneration plant
emissions. Whether solid waste and
wastewater effluents will increase or
decrease with cogeneration depended
upon the degree of pollution controls on
either plant, as well as the type of fuel
switch. Thermal water pollution is
expected to decrease in all cases because
of reduced load on utility plants.
Analysis of an industrial park configu-
ration showed net decreases in panicu-
late, SO2, and NOx emissions of 34%,
11 %, and 27%, respectively. Reductions
in waste heat releases also occurred.
However, there were increases in
suspended solid effluents and in the
amounts of solid waste generated. The
environmental effects of an industrial
park are highly site-specific and depend
upon the number and types of plants
within the park, steam/heat demands,
and the types of fuel used by each of the
industrial plants.
The district heating case study
examined in this project indicated that
environmental benefits result in the form
of reductions in sulfur dioxide
concentrations and thermal effluents.
Ambient SO2 concentrations decreased
despite the fact that there was a net
increase in source SO2 emissions due to
oil and gas being replaced by coal.
Thermal effluents decreased because
waste heat was being used for space
heating, instead of being ejected to the
environment. However, water pollution
and solid wastes increased with addition
of the pollution control system and
process requirements in the heating
plants. From residential units there are
virtually no releases of these pollutants.
Analysis of the cumulative impacts of
developing utility and industrial
cogeneration throughout a region
showed important environmental
benefits. Table 1 indicates the annual
emission reductions attainable from
utility and industrial cogeneration of
varying amounts of electrical power in
the Tennessee Valley Authority (TVA)
service area. Coal characteristics for the
Widows Creek Station were chosen to
determine emissions changes.
Cogeneration of 1865 MW of electricity
represents approximately 16 percent of
the theoretical cogeneration potential in
the TVA region.
The near-term (mid-1980's) potential
for cogeneration has been predicted to be
644 MWin Massachusetts and 1683 MW
in New England. Utility residual fuel oil is
displaced by distillate oil used for cogen-
eration at commercial sites. Emissions
from cogeneration systems may cause
localized sulfur oxide and nitrogen oxide
problems, but substantial net reductions
in regional emissions would occur. These
net reductions in emissions would be on
the order of 10,000 tonnes per year.
Changes in carbon monoxide, hydrocar-
bon, and total suspended particulate
emissions would typically be one to two
orders of magnitude smaller.
Environmental Issues
The final report identifies two environ-
mental issues raised by cogeneration
use. System developers believe that the
costs of meeting stringent air pollution
control regulations, particularly in non-
attainment areas, will significantly re-
duce the economic benefits of cogenera-
tion. Local air quality control agencies
believe that the use of diesel engines and
gas turbines in urban areas may result in
significant increases in nitrogen oxide
and particulate emissions because
these sources may not be adequately
covered by current emission regulations.
Recommendations
The study recommends the following
research should cogeneration, as
expected, have significant market pene-
tration in the coming decade.
Develop an Environmental Data
Base Specific for Cogeneration
Systems
The development of an environmental
data base would facilitate the ability of
the Agency to communicate regulatory
policies to cogeneration developers and
would provide an up-to-date assessment
of this expanding energy supply
technique. Potential users of
cogeneration systems could employ this
information to assess potential impacts
and regulatory policies that have to be
considered when such systems are
installed. Emerging energy-technologies,
as well as conventional power sources,
should be included in this data base.
Increase Effort in Pollution
Reduction Techniques for Small
Combustion Devices
As a result of uncertainties associated
with future supplies of oil and gas, many
industrial firms have increased the use of
coal and other fuels, such as wood and
municipal wastes. The use of these fuels
jn small combustion devices is often
impractical because of the expense of
currently available pollution control
equipment. The development of suitable
control technologies/methods for small
combustion devices will allow the
utilization of these fuels with minimal
environmental impact.
Table 1. Emission Reductions from Cogeneration in the TVA Region*
Cogenerated
Flortririty Emission Reduction, Megagrams/Year (Tons/Year!
MWfeJ
530
1080
1865
TSP
486 (536)
970 (1.070)
1,675 (1.847)
SOX
7,015 (7.737)
14,025 (15.468)
23. 375 (25.670)
NOX
3,820 (4.213)
7,635 (8,421)
13, 155 (14,508)
*Coal Characteristics: Sulfur: 3.7%
Ash- 25%
Heat Content: 23.2 megajoules/'kilogram (10,000 Btu/lb)
Control Efficiency: 80% for SOi, 99.5% for TSP
(Note that since this study was completed, regulations have been revised
to regwre 90% SO2 removal.)
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John Dadiani is with TR W Energy Engineering Division, McLean, VA 22102; the
EPA author Benjamin L. Blaneyfalso the EPA Project Officer, see below) is with
the Industrial Environmental Research Laboratory, Cincinnati. OH 45268.
The complete report, entitled "Cogeneration: Status and Environmental Issues."
(Order No. PB 84-155 175; Cost: $ 11.50, 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
Cincinnati. OH 45268
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
Penalty for Private Use $300
*"* i>
U u u 0
U.S. GOVERNMENT PRINTING OFFICE: 1984-759-015/7620
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