United States
Environmental Protection
Agency
Air and Energy Engineering
Research Laboratory
Research Triangle Park, NC 27711
Research and Development
EPA/600/SR-92/005 March 1992
EPA Project Summary
Greenhouse Gases from Small-
scale Combustion in Developing
Countries -A Pilot Study in
Manila
i]
K. R. Smith, R.A. Rasmussen, F. Manegdeg, and M. Apte
This report presents the results of a
pilot study in Manila, Republic of the
Philippines, to evaluate the emission
potential of greenhouse gases (GGs)
from small-scale combustion devices
used for cooking in most of the world's
households. The results from the pilot
study suggest that this may represent
a more significant source than previ-
ously thought. As a result, it has been
decided to conduct a more compre-
hensive study in India and China. The
results from this work will be used in
EPA's Global Climate Change Program
to develop a more reliable estimate of
the GG potential of the fuel types and
types of small-scale combustion de-
vices being used in most of the world's
households.
This Project Summary was developed
by EPA's Air and Energy Engineering
Research Laboratory, Research Tri-
angle Park, NC, to announce key find-
ings of the research project that is fully
documented in a separate report of the
same title (see Project Report ordering
information at back).
Introduction
It is clear that the combustion of bio-
mass plays a significant role in global
atmospheric chemistry and thus in the po-
tential for global warming from an en-
hanced GG effect. As shown in Table 1,
for example, three recent reviews esti-
mate the contributions of biomass com-
bustion to global emissions to be as high
as 20 - 50% for some of the major GGs.
From biomass combustion, much of the
carbon dioxide (CO2) does not result in a
net increase in atmospheric concentration
because the gas is also taken up by ter-
restrial biomass and soil. Although the
other GGs are also taken up to some
extent, more of the releases from bio-
mass combustion may result in net atmo-
spheric additions. In addition, the uncer-
tainty in our knowledge is substantially
larger for the non-CO2 GGs than for COZ.
Estimates
Although uncertain, the contribution of
biomass combustion to the global carbon
cycle has been estimated in five catego-
ries. These are reorganized and expanded
in Table 2 along with estimated total car-
bon emissions. Four categories represent
processes of large-scale open combus-
tion, i.e., outdoor fires associated with
swidden agriculture, permanent defores-
tation, savannas, and crop residues. Much
crop residue is also burned in small-scale
closed or semi-enclosed conditions in
cooking and heating stoves. As shown,
estimated crop residues used in stoves
are about 350 million tonnes. In addition,
most firewood in the developing world is
burned in semi-enclosed conditions or
made into charcoal for use under such
conditions. Thus, the developing-country
biomass fuel flow (crop residues, fuelwood,
and wood for charcoal) represents much
of the total global carbon emissions from
all biomass combustion, more than 20%,
and perhaps approaching 50% (based on
Table 2).
In recent years, the wide uncertainty
about emissions from open large-scale bio-
Printedon Recycled Paper
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Ttblo 1. Estimates of Global GG Emissions from Biomass Burning fjgfyr, element basis) (1)'
Biomass Total % Blomass(2) % Biomass(3) % Biomass(4)
CO
CO
CH4
NpOfS)
TNMOC"
CH3CI
3500
350
38
0.1-0.3
24
0.51
8700
1100
380
12-14
100
2.3
40
32
10(5)
24
22
25-45%
15-50%
3-10%
0.8-2%
8%
0.4-2%
Data from source (1) unless otherwise noted by numbers in parentheses. All sources are
Identified in the full report.
Total non-methane organic compounds (including, but not limited to, NMHC; i.e., non-methane
hydrocarbons).
Tabla 2. Total Carbon Released by Biomass Combustion
To Ar
Open Burning (1)'
Swidden Agriculture
Permanent Deforestation
Savanna Fires
Crop Residues
Enclosed Burning in Developing Countries (2)
Crop Residues*'
Firewood
Wood for Charcoal
Wood in developed countries (3)
Total Biomass
Total Fossil Fuels
500-1000
200-700
300-1600
150-450
350
540
70
80 .
2100-4700
5700
Sources, indjcated by numbers in parentheses, are identified in the full report.
Includes animal dung used as fuel.
mass fires, has led to a substantial in-
crease in attention given to measuring
and understanding these processes. Sub-
stantially less attention, however, has been
given to two categories, firewood and crop
residues in small-scale combustion de-
vices.
In both categories, the uncertainty about
total emissions is partly due to uncertainty
in the source terms (i.e., how much is
burned each year) and partly to uncer-
tainty in the emission factors (i.e., how
much of each GG is emitted per kilogram
burned). In general, emissions factor esti-
mates are based on a rather small set of
measurements made in field and labora-
tory situations. Most of these have been
designed to duplicate the conditions of
open large-scale combustion. As a result,
emissions from fuelwood are rated in cat-
egory D in certainty, where A is most
certain and E is least certain.
This is unfortunate, for it is clear that
emission factors for biomass are quite sen-
sitive to changes in combustion condi-
tions. It should not be assumed, there-
fore, that emission factors derived for open
large-scale combustion can be appropri-
ately applied to small-scale semi- or com-
pletely enclosed combustion. Yet it seems
that perhaps 90% of the firewood and a
large fraction of the combusted crop resi-
dues in the world (Table 2) are burned
under such conditions in household cook-
ing and heating stoves. Although house-
hold heating stoves are an important fac-
tor in total wood combustion in developed
countries, the vast majority are used for
cooking and space heating in developing
countries. Globally, something like 50%
of the households in the world use simple
biomass fuels (wood, charcoal, crop resi-
dues, animal dung) for cooking.
Conclusions
More extensive field measurements of
GG emission factors for a range of fuels
and combustion devices would be useful
in pinning down global GG emissions in-
ventories that are now known within rather
wide ranges of uncertainty. In addition,
they would help in the design of GG-
reduction strategies, for it is possible that
changes in fuel and/or combustion condi-
tions in these small devices may be a
cost-effective way to address part of the
GG problem on a global basis.
To some observers, it might seem more
appropriate to monitor GG emissions from
such stoves in controlled settings, as is
done with other combustion devices, such
as gas stoves and automobiles. Unfortu-
nately, experience has shown that, be-
cause slight changes in combustion con-
ditions in small stoves (e.g., in the fire-
tending behavior of the cook) can have
large impacts on emissions factors, it is
difficult to know whether laboratory or simu-
lated conditions actually duplicate those
in the field sufficiently well to be relied
upon. A better database of field mea-
surements will be a necessary step in
eventually designing reliable laboratory
measurement techniques.
Since little is also known about emis-
sion factors from small-scale combustion
of other fuels in developing countries, it
would be valuable to test them as well.
Kerosene and liquefied petroleum gas
(LPG), for example, are often the fuels
that first substitute for biomass as devel-
opment occurs in developing countries.
Consequently, their emission levels pro-
vide a reasonable interim target for what
might be achieved by a program to re-
duce biofuel use in households.
A large-scale field monitoring effort for
GG emission factors in developing coun-
tries would entail significant costs and un-
certainties. In this situation, it seemed ap-
propriate to undertake a pilot study in ad-
vance.
Thus, to examine the feasibility of a
larger study to improve knowledge of GG
emission factors for small-scale biofuel
combustion, a pilot study was conducted
in Manila beginning in September 1990.
•&U.S. GOVERNMENT PRINTING OFFICE: 1992 - 648-080/40220
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K. Smith is with Environmental and Policy Institute, Honolulu, HI 96848; R.
Rasmussen is with R.A. Rasmussen and Consultants, Hillsboro, OR 97124; F.
Manegdeg is with the University of the Philippines, Dilliman, Quezon City 1101,
Republic of the Philippines; and M. Apte is with Lawrence Berkeley Laboratory,
Berkeley, CA 94720.
Susan A. Thorneloe is the EPA Project Officer (see below).
The complete report, entitled "Greenhouse Gases from Small-scale Combustion in
Developing Countries -A Pilot Study in Manila," (Order No. PB92-139 369/AS;
Cost: $19.00; subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield,VA22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Air and Energy Engineering Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC27711
United States
Environmental Protection
Agency
Center for Environmental
Research Information
Cincinnati, OH 45268
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PERMIT No. G-35
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Penalty for Private Use $300
EPA/600/SR-92/005
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