Methane emissions from residential biomass combustion

Small scale biomass combustion can be a major source of air pollutants like hydrocarbons and particulate matters. Methane is one of the hydrocarbons emitted when burning biomass fuels and recent studies show that methane emissions from different kinds of residential biomass systems can vary significantly depending on type of combustion system and type of fuel. On a yearly basis Sweden is obligated to report air emissions of several pollutants to different international bodies. In previous reporting only one emission factor for methane is accounted for, including all technologies and all fuel types. This study aims to improve the reporting of methane emissions from small scale combustion of biomass by revising both activity data and emission factors. Further, the times series 1990-2003 for methane emission will be updated. New methane emission factors from small scale combustion of wood log, pellets and wood chips/sawdust was determined and an improved method was then used to calculate the emissions. In order to match the activity data categories, the emission factors were grouped by heating system category and fuel type. The result showed that methane emissions from wood log combustion are significantly higher compared to pellets combustion. However, significant variations in emission factors occur for specific combustion appliances and operation conditions. The recalculated time series for 1990-2003 showed higher values of methane emissions due to desegregation of emission factors by combustion technology.