Criteria, Greenhouse Gas, and Hazardous Air Pollutant\nEmissions Factors from Residential Cordwood and Pellet Stoves Using\nan Integrated Duty Cycle Test Protocol

Air pollution from\nresidential wood heating (RWH) presents challenges\nat the intersection of climate and public health. With a revised National\nAmbient Air Quality Standard (NAAQS, at 9 μg/m<sup>3</sup>)\nfor particulate matter (PM) in the United States (U.S.), the Environmental\nProtection Agency (EPA) will likely classify new non-attainment areas\ndue primarily to emissions from RWH. Agencies will use emissions factors\n(EFs) to develop attainment strategies. Many will rely on EPA modeling\nplatforms based on data from the National Emissions Inventory (NEI).\nThe NEI uses RWH EFs based on data from mid-1990’s in-situ\nstudies and a speciation profile from a 2001 study of fireplace emissions.\nThe NEI does not include greenhouse gas (GHG) emissions for this sector,\nwhich plays a key role when assessing climate reduction strategies\nfor the buildings sector. Here, we tested seven wood stoves to determine\nEFs, representing various vintages and control technologies, using\na novel test method that reflects in-use operational settings called\nthe Integrated Duty Cycle. The study measured multiple pollutants\nconcurrently: criteria pollutants (particulate matter [PM], CO, and\nNOx), nonmethane total hydrocarbons (NMTHCs), GHGs, black carbon (eBC),\nbrown carbon (BrC), and multiple hazardous air pollutants (HAPs).\nWe found no significant difference in PM EFs between uncertified and\nnon-catalytic stove technologies. RWH EF results from this study exceeded\n2020 NEI RWH EFs for NMTHC and multiple HAPs. Applying our study’s\nEFs to the 2020 NEI suggests that RWH, compared to all other sources,\nranks as the 2nd largest source category of formaldehyde; the 3rd\nlargest of benzene, 1,3-butadiene, and acrolein; and the 4th largest\nof Pb emissions. RWH also emits more methane compared to natural gas\nor oil residential heating, raising questions about substitution of\nwood as a climate neutral heating fuel. However, compared to uncertified\nstoves, pellet stove EFs (except toxic metals) were significantly\nlower (<i>p</i> < 0.01). In summary, RWH appears to be\nan underestimated source of PM (non-catalytic technology), methane,\nNMTHC, toxic metals, and other HAPs, which has important implications\nfor climate and public health policy in the U.S. and globally.