Emissions from residential wood combustion - Uncertainties run amuck
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Transcript of Emissions from residential wood combustion - Uncertainties run amuck
NATIONAL ENVIRONMENTAL RESEARCH INSTITUTE
AARHUS UNIVERSITY
Emissions from residential wood combustion - Uncertainties run amuck
Ole-Kenneth Nielsen, Malene Nielsen & Marlene PlejdrupDepartment of Policy AnalysisNational Environmental Research InstituteAarhus University
12th Joint EIONET and TFEIP MeetingStockholm, May 2, 2011
NATIONAL ENVIRONMENTAL RESEARCH INSTITUTE
AARHUS UNIVERSITY May 2, 2011Ole-Kenneth Nielsen
Outline› Introduction
› Significance of residential wood combustion
› Uncertainties› Activity data› Emission factors
› Different technologies› Different operating conditions› Different measurement methods
› Conclusions
NATIONAL ENVIRONMENTAL RESEARCH INSTITUTE
AARHUS UNIVERSITY May 2, 2011Ole-Kenneth Nielsen
Introduction› Increased importance as legislative demands
have reduced emissions from energy industries and manufacturing industries
› Large public and media attention due to local nuisances caused by residential wood combustion – neighbour complaints
› Danish legislation from 2008› Emission limit values for PM from space heaters› Emission limit values for CO, HC and PM for boilers
NATIONAL ENVIRONMENTAL RESEARCH INSTITUTE
AARHUS UNIVERSITY May 2, 2011Ole-Kenneth Nielsen
Significance in DenmarkShare of national
total in 2009
SO2 5.7 %
NOx 3.1 %
NMVOC 15.3 %
CH4 1.9 %
CO 27.0 %
N2O 0.7 %
NH3 0.2 %
TSP 45.3 %
PM10 55.1 %
PM2.5 67.9 %
HCB 24.7 %
PCDD/F 47.1 %
Share of national total in 2009
As 5.6 %
Cd 17.5 %
Cr 8.8 %
Cu 0.6 %
Hg 2.6 %
Ni 1.4 %
Pb 12.9 %
Se 0.1 %
Zn 9.2 %
Benzo(a)pyrene 85.3 %
Benzo(b)flouranthene 82.2 %
Benzo(k)flouranthene 85.3 %
Indeno(1,2,3-c,d)pyrene 81.3 %
NATIONAL ENVIRONMENTAL RESEARCH INSTITUTE
AARHUS UNIVERSITY May 2, 2011Ole-Kenneth Nielsen
Activity data› Highly uncertain due to the large amount of non-
traded wood
› Large recalculation in Denmark in 2006
› Previously the official statistic was based on recorded sales and an assumed correction factor
› Now wood consumption is based on recorded sales combined with a survey every second year
› The survey uses telephone interviews to establish the wood consumption
› Total wood consumption in residential plants in Denmark in 2009: 33,384 TJ ≈ 2.1 mio. ton
NATIONAL ENVIRONMENTAL RESEARCH INSTITUTE
AARHUS UNIVERSITY May 2, 2011Ole-Kenneth Nielsen
Time-series for firewood consumption in residential plants
› The survey carried out in 2006 increased the firewood
consumption in 2004 by 40 %
0
5000
10000
15000
20000
25000
1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005
Fir
ewo
od
co
nsu
mp
tio
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TJ
Firewood consumption, 2005 statistics Firewood consumption, 2006 statistics
NATIONAL ENVIRONMENTAL RESEARCH INSTITUTE
AARHUS UNIVERSITY May 2, 2011Ole-Kenneth Nielsen
Emission factors› Heavily influenced by:
› Technology: boilers vs. stoves – old appliances vs. new appliances
› Operating conditions: batch size – log size etc.› Fuel quality: water content – wood species – ”clean”
wood› Measurement method
› EMEP/EEA Guidebook provides EFs for fireplaces, stoves, boilers, advanced fireplaces, advanced stoves and pellet stoves
› The following will focus on PM emissions
NATIONAL ENVIRONMENTAL RESEARCH INSTITUTE
AARHUS UNIVERSITY May 2, 2011Ole-Kenneth Nielsen
Technology› Large differences between boilers and stoves
and for old and new technologies
TechnologyEmission
factor Reference
Wood boiler (TSP, old boilers) 588-736Winther,
2008
Wood boiler (TSP, newer boilers) 96-335Winther,
2008
Wood boiler (TSP, modern boilers) 64-233Winther,
2008
Open fire place (PM10, conventional) 1188 Basrur, 2002
Open fire place (PM10, advanced) 313 Basrur, 2002
Wood stove (PM10, conventional) 875-1438 Basrur, 2002
Wood stove (PM10, advanced) 313 Basrur, 2002
NATIONAL ENVIRONMENTAL RESEARCH INSTITUTE
AARHUS UNIVERSITY May 2, 2011Ole-Kenneth Nielsen
Technology› High variability of emission factors. However,
clear indications that newer technologies have substantially lower emission factors compared to older technologies
› Need for more technology dependent emission factors in the Guidebook
› Important to have a detailed description of the technology for which the emission factors are applicable, due to significant technological development in later years
NATIONAL ENVIRONMENTAL RESEARCH INSTITUTE
AARHUS UNIVERSITY May 2, 2011Ole-Kenneth Nielsen
Operating conditions› Large differences in emissions for different
operating conditions
Derived from Klippel & Nussbaumer (2007)
PM g/GJ Reference
Wood boiler (Old) 87-2200 Johansson et al., 2004
Wood stove (Old) 344-5075 Glasius et al., 2005
Wood boiler (Old) 963-1481 Glasius et al., 2005
Open fire place 170-780 Purvis & McCrills, 2000
Pellet boiler 16-27 Tissari, 2008
Pellet stove 11-81 Boman, 2005
NATIONAL ENVIRONMENTAL RESEARCH INSTITUTE
AARHUS UNIVERSITY May 2, 2011Ole-Kenneth Nielsen
Operating conditions› A study showed that big batch size significantly
increased the emissions
› Regarding log size the same study found that small logs resulted in higher emissions than big logs
› Very difficult to completely take all conditions into account when deriving emission factors
› Focus should be on ”typical” operating conditions
› Important when using laboratory measurements that emission factors are not based on ideal conditions
NATIONAL ENVIRONMENTAL RESEARCH INSTITUTE
AARHUS UNIVERSITY May 2, 2011Ole-Kenneth Nielsen
Fuel quality› The water content will influence emissions. Most
studies have not isolated the effect of water content
› Studies have shown that PM emissions also depend on wood species. One study showed that oak had an emission factor (5.1 g/kg) of almost halve that of pine (9.5 g/kg)
› The use of treated (painted, impregnated) wood or other waste fractions can significantly increase emissions. This factor has not been isolated in studies for residential wood combustion
› All these elements will be extremely difficult to take into account in a national inventory
NATIONAL ENVIRONMENTAL RESEARCH INSTITUTE
AARHUS UNIVERSITY May 2, 2011Ole-Kenneth Nielsen
Measurement methods› There are several different methods available for
measuring PM emissions, e.g.› In-stack gravimetric methods (e.g. VDI2066 bl.2)› Out-stack gravimetric methods without dilution tunnel
(e.g. SS028426)› Gravimetric methods with dilution tunnel (e.g. NS3058)
› The main difference is whether the measurement is carried out in the hot flue gas or after the semi-volatile compounds have condensed
› To ensure comparability between emission inventories there is a need to establish a common method for deriving emission factors
NATIONAL ENVIRONMENTAL RESEARCH INSTITUTE
AARHUS UNIVERSITY May 2, 2011Ole-Kenneth Nielsen
The impact of measurement methods
› Emissions measured in a dilution tunnel are 2.5-10 times higher than the solid particle emissions measured in the hot flue gas
› A Danish test showed 4.8 times higher PM emissions when measured in a dilution tunnel compared to in-stack
Nussbaumer, T., Klippel, N. & Johansson, L., 2008
NATIONAL ENVIRONMENTAL RESEARCH INSTITUTE
AARHUS UNIVERSITY May 2, 2011Ole-Kenneth Nielsen
Comparison between countries› Denmark uses the EMEP/EEA EFs for e.g. old
wood stoves. This EF is very high compared to some other countries
g pr. GJ Denmark Sweden Germany Ireland Finland Austria
TSP EF for wood stoves 850 100 72 300 400 148
› The large difference can be attributed to different measurement methods
› Germany and Sweden uses in-stack or heated out-stack measurements
› Denmark (and e.g. Norway) uses out-stack measurements in a dilution tunnel
NATIONAL ENVIRONMENTAL RESEARCH INSTITUTE
AARHUS UNIVERSITY May 2, 2011Ole-Kenneth Nielsen
Conclusions› Residential wood combustion is in many
countries a key category for several pollutants
› Large uncertainties associated with:› Wood consumption› Technology› Operating conditions› Measurement method
› The vastly different emission factors depending on measurement methods will be a problem if/when PM is included in the emission ceilings for 2020
NATIONAL ENVIRONMENTAL RESEARCH INSTITUTE
AARHUS UNIVERSITY May 2, 2011Ole-Kenneth Nielsen
Conclusions› The reporting guidelines and/or the
Guidebook should address the issue of measurement methods to ensure consistent reporting and comparability between countries
› The Guidebook should be improved to cover more technologies including modern technologies with low emission factors
NATIONAL ENVIRONMENTAL RESEARCH INSTITUTE
AARHUS UNIVERSITY
Thank you for your attention