Integrating aerosol emissions of forest biomass into a life cycle assessment of forest-based production

Climate change mitigation is globally increasing the demand for forest biomass to substitute for fossil-based materials. Consequently, fossil-based greenhouse gas emissions will decrease, but simultaneously, aerosol emissions may substantially change. The evaluation of the substitution effects of forest-based materials may be biased if aerosol emissions are not considered. We integrated aerosol emissions from the use of forest-based biomass and fossil-based materials into a life cycle assessment (LCA) tool and simulated the biomass production of Norway spruce under alternative harvest intensities of energy biomass in middle boreal conditions in Finland. For the forest management regimes, we calculated particulate matter (PM) emissions; i.e. total suspended particles (TSP), respirable particulate matter (PM10), fine particulate matter (PM2.5) and black carbon (BC), and gaseous emissions including nitrogen oxides (NOx), sulphur dioxide (SO2) and non-methane volatile organic compounds (NMVOC). We also considered how replacing fossil counterparts and peat with forest-based biomass energy affects aerosol emissions. The differences between the management regimes were minor for sawn logs and pulpwood. Energy biomass use, especially combustion in small-scale appliances, increased aerosol emissions. Energy biomass use produced higher PM (TSP, PM10, PM2.5, BC) emissions than the use of coal and peat as energy. Regarding construction materials, the highest aerosol emissions were found for sawn wood production, followed by steel production. Cardboard production emitted remarkably higher aerosol emissions than high-density polyethylene (HDPE) plastic production. The inclusion of aerosol emissions of forest biomass use seems to be important for assessing the climate and health effects of the transition to a forest bioeconomy.