Climate and health-relevant pollutant emissions from oil and natural gas boilers

Emission factor data for existing heating appliances are being used to estimate achievable emission reductions with emerging heating technologies. However, the emission factors currently being used for modeling were developed prior to low-sulfur fuel standards and rely on a small number of studies, mostly focusing on steady-state operation. In this work, detailed emission measurements of typical heating equipment fired with natural gas and No. 2 oil under relevant field-use conditions were made to update these emission factors. The work included the emissions and heating performance of three residential hydronic heating appliances (27-41 kW), two fueled with natural gas, one fueled with No.2 oil, and two commercial steam heating appliances (220-440 kW), one fueled with natural gas and the other with No.2 oil. The burner technologies employed include natural gas conversion burners, a natural gas Inshot burner, and single and dual-firing-rate pressure atomizing oil burners. The appliances were evaluated using a load-profile test method that captured transient conditions in cyclic operation, typical of field use. The emission factors of 17 pollutant compounds were measured in this work and compared with values currently published in United States Environmental Protection Agency (EPA) databases. These pollutants include particulate matter mass, methane, and speciated volatile organic compounds. Particulate mass was found to be 1.7 to 4.6 times less than the EPA 2020 National Emissions Inventory (NEI) value for No. 2 oil-fueled appliances and ranged 3.5 times more to 1.4 times less for natural gas appliances. Methane was 3.5 times higher for the residential natural gas appliances tested due to transient methane emissions during ignition and shutdown. Speciated volatile organic compounds were found to be lower than the closest related emission inventory values.<i>Implications</i>: The largest US building energy use is for space and water heating. In 2019, NYS established the NYS Climate Leadership and Community Protection Act, which mandates the state achieve a 40% reduction in GHG emissions by 2030 and an 85% reduction in greenhouse gas emissions by 2050, based on 1990 emission levels. This mandate will result in significant changes to the fuels and technologies used for heating. Emission factor data for existing heating appliances are being used to estimate achievable emission reductions with these changes. In this work, a new set of detailed emission factors has been developed through laboratory measurements which will greatly improve the knowledge about these existing sources nationwide.