Use of forest biomass may induce changes in the aerosol emissions, with subsequent impacts on the direct and indirect climate effects of these short-lived climate forcers. We studied how alternative wood use scenarios affected the aerosol emissions and consequent radiative forcing in Finland. In all alternative scenarios, the harvest level of forest biomass was increased by 10 million m3 compared to the baseline. The increased biomass harvest was assigned to four different uses: (i) to sawn wood, (ii) to pulp-based products, (iii) to energy biomass combusted in small-scale appliances or (iv) to energy biomass combusted in medium-to-large scale boilers. Aerosol emissions (black carbon (BC), organic carbon (OC) and sulphur dioxide (SO2)) under these scenarios were estimated using displacement factors (DFs). The global aerosol-climate model ECHAM-HAMMOZ was used to study instantaneous radiative forcing due to aerosol-radiation interactions (IRFARI) and effective radiative forcing (ERF), based on the differences in aerosol emissions between the alternative wood use scenarios and the baseline scenario. The results indicated that the use of sawn wood and energy biomass combusted in medium- to large-scale boilers decreased radiative forcings, implying climate cooling, whereas the increased use of pulpwood increased them. Energy biomass combustion in small-scale appliances increased IRFARI by 0.004 W m-2 but decreased ERF by -0.260 W m-2, specifically due to a strong increase in carbonaceous aerosols. Alternative use of forest biomass notably influenced aerosol emissions and their climate impacts, and it can be concluded that increased forest biomass use requires a comprehensive assessment of aerosol emissions alongside greenhouse gases (GHGs). Given the consequent reduction in radiative forcing from aerosol emissions, we conclude that the greatest overall climate benefits could be achieved by prioritising the production of long-lived wood-based products.

Open burning is commonly used to dispose of piles of forest residues generated by forest management activities; however, this method is associated with smoke emissions and damage to forest soil. Air curtain burners (ACB), such as the Firebox (FB) and CharBoss (R) (CB), offer an alternative to open burning. This study evaluated the performance of FB for biomass disposal and CB for biomass disposal and biochar production with the objective of quantifying the benefits and limitations of each machine. Ponderosa pine biomass obtained from harvesting after a wildfire event and freshly cut wood from ponderosa pine trimmings were used to evaluate the performance of each machine. We measured the combustion rate for both machines and biochar produced from CB. The burning rate for large-diameter (>10 cm) biomass using FB machine was 1.1 GT/h (924 degrees C) while small-diameter (<5 cm) biomass burned at the rate of 2.4 GT/h (814 degrees C), and for biomass consisting of mixed-sized materials it was 2.5 GT/h with the highest recorded temperature of 1089 degrees C. The biochar yield from CB operations ranged between 8.8 % and 17 % on a bone-dry ton basis. The size of biomass material, machine type and moisture content influenced the burning rate. The FB is most appropriately used in a centralized setting where large quantities of biomass are available near harvest operations, while the CB is better used for biochar production in a mobile setting. These results are useful for understanding alternative biomass management options, the long-term financial implications, and environmental benefits.