Carbon emissions associated with the procurement and utilization of forest harvest residues for energy, northern Minnesota, USA

Interest in the use of forest-derived biomass for energy has prompted comparisons to fossil fuels and led to controversy over the atmospheric consequences of its utilization. Much of the debate has centered on the carbon storage implications of utilizing whole trees for energy and the time frame necessary to offset the carbon emissions associated with fixed-life bioenergy facilities. Forest harvest residues may provide a cost-effective, carbon friendly alternative; however, robust empirical estimates of the carbon consequences of utilizing this feedstock are needed to inform policy and management related to forest-based bioenergy. This study used a modeling approach to assess the availability of harvest residues in northern Minnesota and compared the estimated carbon emissions from in-forest decomposition with emissions from processing, transport, and utilization of residues in a proposed 26 MW bioenergy facility. Model results suggest that the combined emissions from the proposed facility would be 42 percent greater – a net difference of 2,888,751 Mg of CO2 – than in-forest decomposition emissions over a 25-year period. The disparity in carbon emissions with and without the proposed facility decreases with increasing time, ultimately reducing to solely emissions from harvesting and transport 190+ years after establishment. These findings have important implications for the development of renewable energy standards including incentives aimed at increasing the use of forest-derived biomass.