Woody Biomass Substitution for Thermal Energy at Softwood Lumber Mills in the US Inland Northwest*

Using life-cycle inventory production data, the net global warming potential (GWP) of a typical inland Northwest softwood lumber mill was evaluated for a variety of fuel types used as boiler inputs and for electricity generation. Results focused on reductions in carbon emissions in terms of GWP relative to natural gas as the fossil alternative. Woody feedstocks included mill residues, forest residuals, and wood pellets. In all fuel-substitution scenarios, increasing the use of biomass for heat generation decreased GWP. Using woody biofuels for electricity production is somewhat less effective in lowering carbon emissions than when used for heat energy. Heat generation at the mill under the current practice of using about half self-generated mill residues and half natural gas resulted in a 35 percent reduction in GWP over 100 percent natural gas. The greatest reduction in GWP (66%) was from increased use of forest residuals for heat energy, eliminating the use of fossil fuels as a direct heating fuel at the mill. We summarize the results by documenting that greater use of woody biomass for heat energy will reduce carbon emissions over fossil-based fuels.