1. NATIONAL ENVIRONMENTAL RESEARCH INSTITUTE AARHUS UNIVERSITY Emissions from residential wood combustion - Uncertainties run amuck Ole-Kenneth Nielsen, Malene Nielsen & Marlene Plejdrup Department of Policy Analysis National Environmental Research Institute Aarhus University 12th Joint EIONET and TFEIP Meeting Stockholm, May 2, 2011

2. NATIONAL ENVIRONMENTAL RESEARCH INSTITUTE AARHUS UNIVERSITY May 2, 2011 Ole-Kenneth Nielsen Outline ›Introduction ›Significance of residential wood combustion ›Uncertainties ›Activity data ›Emission factors ›Different technologies ›Different operating conditions ›Different measurement methods ›Conclusions

3. NATIONAL ENVIRONMENTAL RESEARCH INSTITUTE AARHUS UNIVERSITY May 2, 2011 Ole-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

4. NATIONAL ENVIRONMENTAL RESEARCH INSTITUTE AARHUS UNIVERSITY May 2, 2011 Ole-Kenneth Nielsen Significance in Denmark Share of national total in 2009 SO 2 5.7 % NO x 3.1 % NMVOC15.3 % CH 4 1.9 % CO27.0 % N2ON2O0.7 % NH 3 0.2 % TSP45.3 % PM 10 55.1 % PM 2.5 67.9 % HCB24.7 % PCDD/F47.1 % Share of national total in 2009 As5.6 % Cd17.5 % Cr8.8 % Cu0.6 % Hg2.6 % Ni1.4 % Pb12.9 % Se0.1 % Zn9.2 % Benzo(a)pyrene85.3 % Benzo(b)flouranthene82.2 % Benzo(k)flouranthene85.3 % Indeno(1,2,3-c,d)pyrene81.3 %

5. NATIONAL ENVIRONMENTAL RESEARCH INSTITUTE AARHUS UNIVERSITY May 2, 2011 Ole-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

6. NATIONAL ENVIRONMENTAL RESEARCH INSTITUTE AARHUS UNIVERSITY May 2, 2011 Ole-Kenneth Nielsen Time-series for firewood consumption in residential plants ›The survey carried out in 2006 increased the firewood consumption in 2004 by 40 %

7. NATIONAL ENVIRONMENTAL RESEARCH INSTITUTE AARHUS UNIVERSITY May 2, 2011 Ole-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

8. NATIONAL ENVIRONMENTAL RESEARCH INSTITUTE AARHUS UNIVERSITY May 2, 2011 Ole-Kenneth Nielsen Technology ›Large differences between boilers and stoves and for old and new technologies TechnologyEmission factorReference 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)1188Basrur, 2002 Open fire place (PM10, advanced)313Basrur, 2002 Wood stove (PM10, conventional)875-1438Basrur, 2002 Wood stove (PM10, advanced)313Basrur, 2002

9. NATIONAL ENVIRONMENTAL RESEARCH INSTITUTE AARHUS UNIVERSITY May 2, 2011 Ole-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

10. NATIONAL ENVIRONMENTAL RESEARCH INSTITUTE AARHUS UNIVERSITY May 2, 2011 Ole-Kenneth Nielsen Operating conditions ›Large differences in emissions for different operating conditions Derived from Klippel & Nussbaumer (2007) PM g/GJReference Wood boiler (Old)87-2200Johansson et al., 2004 Wood stove (Old)344-5075Glasius et al., 2005 Wood boiler (Old)963-1481Glasius et al., 2005 Open fire place170-780Purvis & McCrills, 2000 Pellet boiler16-27Tissari, 2008 Pellet stove11-81Boman, 2005

11. NATIONAL ENVIRONMENTAL RESEARCH INSTITUTE AARHUS UNIVERSITY May 2, 2011 Ole-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

12. NATIONAL ENVIRONMENTAL RESEARCH INSTITUTE AARHUS UNIVERSITY May 2, 2011 Ole-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

13. NATIONAL ENVIRONMENTAL RESEARCH INSTITUTE AARHUS UNIVERSITY May 2, 2011 Ole-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

14. NATIONAL ENVIRONMENTAL RESEARCH INSTITUTE AARHUS UNIVERSITY May 2, 2011 Ole-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

15. NATIONAL ENVIRONMENTAL RESEARCH INSTITUTE AARHUS UNIVERSITY May 2, 2011 Ole-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. GJDenmarkSwedenGermanyIrelandFinlandAustria TSP EF for wood stoves85010072300400148 ›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

16. NATIONAL ENVIRONMENTAL RESEARCH INSTITUTE AARHUS UNIVERSITY May 2, 2011 Ole-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

17. NATIONAL ENVIRONMENTAL RESEARCH INSTITUTE AARHUS UNIVERSITY May 2, 2011 Ole-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

18. NATIONAL ENVIRONMENTAL RESEARCH INSTITUTE AARHUS UNIVERSITY Thank you for your attention