United States
Environmental Protection
Agency
National Risk Management
Research Laboratory
Cincinnati, OH 45268
Research and Development
EPA/600/SR-97/112
November 1997
&EPA Project Summary
Field Performance of
Woodburning Stoves in Colorado
During the 1995-96 Heating
Season
Robert Cornell, Dennis R. Jaasma, and Yagna Mukkamala
During the winter of 1995-96, the field
performance of 13 EPA-certified
woodburning stoves in Crested Butte
and Curecanti National Park, CO, was
evaluated. Measurements included par-
ticulate matter (PM), carbon monoxide
(CO), and weekly average burn rates.
Six non-catalytic Phase II stoves, six
catalytic Phase II stoves, and one cata-
lytic Phase I stove were monitored. The
study adds to the existing database on
the field emissions of newer and older
certified stoves. Average non-catalytic
stove PM and CO emission factors of
the study were 9.8 and 93 g/kg, respec-
tively. For the catalytic stoves the fac-
tors were 22.8 and 112 g/kg, respec-
tively. The report compares these val-
ues with results from previous studies
and suggests reasons that field perfor-
mance is poor relative to what might
be expected from certification test re-
sults.
This Project Summary was developed
by the National Risk Management Re-
search Laboratory's Air Pollution Pre-
vention Control Division, 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).
Objective
The purpose of this project was to quan-
tify the field performance of EPA-certified
woodstoves, both when stoves are rela-
tively new and after stoves have been in
service for an appreciable time. One-week
averages of PM and CO emissions were
measured for a variety of stoves, includ-
ing both catalytic and non-catalytic EPA-
certified models. The Virginia Polytechnic
Institute and State University (VPI) sam-
pler was used for all measurements, and
both PM and CO emissions are reported
as measured by the sampler.
The report summarizes the measure-
ment methods and the measured emis-
sion factors. The emission factors of the
current study are compared with earlier
data for PM and CO emissions of certified
and uncertified (conventional) stoves.
Introduction
Personnel from VPI measured woodstove
emissions in Crested Butte, CO, during the
winters of 1988-89, 1989-90, and 1991-
92. The 1988-89 and 1989-90 measure-
ments were intended to determine the ef-
fect of a town-wide changeover from con-
ventional to EPA-certified (mostly Phase
I) woodstoves. The 1991-92 study was
intended to focus exclusively on Phase II
stoves, but a limited number of Phase II
stoves in Crested Butte and reluctance of
owners to permit monitoring limited the
Phase II data obtained. Both PM and CO
emissions were measured during these
studies. A fourth study, in the winter of
1992-93, involved only CO and carbon
dioxide (CO2) measurements of catalytic
stoves.
The 1995-96 study obtained additional
data on the performance of Phase II stoves
in Crested Butte and in Curecanti Na-
tional Park, located outside of Gunnison,
CO. The intention was to monitor each
stove for four weeks to average the ef-
fects of weekly weather changes and other
uncontrolled variables, but for some stoves
fewer than four 1-week averages were
obtained. Sampling in Crested Butte oc-
curred from February 5 to March 4, 1996.
Sampling in Curecanti National Park oc-
curred from March 8 to April 13, 1996,
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when warm weather ended the heating
season.
Thirteen stoves were monitored: seven
catalytic and six non-catalytic. Household
profiles describing each site are in the full
report. One of the catalytic stoves was
Phase I certified and all other stoves were
Phase II certified. The full report also con-
tains a spreadsheet showing all measured
values and calculated emissions data.
The previous studies created a large
database of emissions from conventional
and Phase I stoves, giving baseline data
for comparison to Phase II models. Only
one of the 1995-96 stoves was monitored
in a previous study and can be directly
compared with previous data. However,
over the years, three Crested Butte stoves
have been monitored for PM and CO dur-
ing more than one season, and their data
can be examined for long term perfor-
mance changes. The 1988-1996 Colorado
work also includes several catalytic stoves
which were monitored for PM and CO
(using the VPI sampler) during one sea-
son and also had short-term (approxi-
mately an hour) monitoring for flue gas
temperature and CO and CO2 concentra-
tions under technician-controlled conditions
during the winter of 1992-93. The 1992-
93 CO, CO2, and temperature data can
give a rough estimate of the PM and CO
data that would have been obtained with
the VPI sampler.
Measurement Procedures
The hardware used for the measure-
ments is known as the "VPI sampler." It
has been compared to the EPA reference
method for woodstove PM and to the dilu-
tion tunnel method for CO measurement
and has been found to be accurate. The
methods for sampler preparation and
workup are documented in earlier reports
and are not repeated here.
Participants used their normal wood sup-
ply. Field personnel weighed a large part
of the participant's woodpile at sampler
deployment, marked the weighed part by
replacing the wood on top of a bright red
ribbon, and weighed any unused wood
from the pre-weighed supply at sampler
retrieval. Fuel moisture was measured
gravimetrically, using chips generated by
low speed drilling of representative logs.
Results
Forty-seven deployments resulted in
useful data on stove emissions. Eight
blanks were also run and were used to
correct the measured results and give an
idea of the uncertainties of this season's
measurements. Blanks were split equally
between Crested Butte and the Curecanti
National Recreation Area.
Table 1 compares the PM and CO fac-
tors for the current study with those of
previous studies. The listed values repre-
sent the average factors for all datapoints
for each type of stove in each study. The
average PM catch of the study was 30.5
mg, and the highest level of uncertainty
was 1.6 mg; thus, the average gravimetric
uncertainty is 1.6/30.5, or 5%. As in previ-
ous studies the uncertainty in CO emis-
sions is estimated to be +/- 10% of re-
ported value.
The average PM emission factor for the
Phase II catalytic stoves in the 1995-96
study was 22.8 g/kg, approximately equiva-
lent to that of conventional stoves and
133% greater than the average PM factor
of Phase II non-catalytic stoves. The CO
emission factors for catalytic stoves were
20% greater than for the non-catalytic
stoves and effectively the same as for
conventional stoves. The average PM
emission factors for catalytic stoves in-
creased by 30% from the 1991-92 study.
The corresponding CO factors gained
45%.
The non-catalytic stoves, on average,
show no definitive evidence of performance
degradation over the course of the study.
A strong dependence of emission factors
on burn rate has been noted for non-
catalytic stoves, and this dependence prob-
ably is the cause of the observed year-to-
year fluctuations in average performance
of these stoves.
Significant physical degradation has
been noted in catalytic stove models over
the course of this study. In some cases
the cause of poor catalytic stove perfor-
mance has been identified as mechanical
failures. In other cases one can only as-
sume that factors such as operator be-
havior or fuel variability are involved. In
non-catalytic models, the operation, fuel-
ing and design of the stoves (as opposed
to mechanical degradation) appear to be
the most likely determiners of emission
performance.
Table 1. Conventional and EPA Certified Woodstove Results
Year of
Study
1988-89
1989-90
1991-92
1995-96
PM Factors, g/kg
Com CAT NCAT
22.1 5.5 —
22.2 11.1 9.9
— 17.6 14.9
— 22.8 9.8
CO Factors, g/kg
Com CAT NCAT
115 40 —
111 52 76
— 77 107
— 112 93
Avg. Burn Rate,
kg/hr
Com CAT NCAT
1.35 0.86 —
1.64 0.93 1.10
— 0.85 0.82
— 0.77 0.98
#Stoves/#
datapoints
Com CAT1 NCAT*
11/37 2/9 —
7/27 72/72 5/29
— 9/31 2/7
— 7/27 6/20
Notes: * 1988-1990 catalytic models were all Phase I certified.
1991-92 included 7 Phase I and 2 Phase II catalytics.
1995-96 included 1 Phase I and 6 Phase II catalytics.
"All non-catalytic models tested were Phase II Certified.
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R. Correll, D.R. Jaasma, and Y. Mukkamala are with Virginia Polytechnic Institute
and State University, Blacksburg, VA 24061-0238.
Robert C. McCrillis is the EPA Project Officer (see below).
The complete report, entitled "Field Performance of Woodburning Stoves in Colo-
rado During the 1995-96 Heating Season," (Order No. PB98-106487; Cost:
$21.50, 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:
Air Pollution Prevention and Control Division
National Risk Management Research Laboratory
U. S. Environmental Protection Agency
Research Triangle Park, NC 27711
United States
Environmental Protection Agency
Center for Environmental Research Information
Cincinnati, OH 45268
Official Business
Penalty for Private Use $300
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EPA
PERMIT No. G-35
EPA/600/SR-97/112
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