ThinTool: A Spreadsheet Model to Evaluate Fuel Reduction Thinning Cost, Net Energy Output, and Nutrient Impacts

We developed a spreadsheet-based model, named ThinTool, to evaluate the cost of mechanical fuel reduction thinning including biomass removal, to predict net energy output, and to assess nutrient impacts from thinning treatments in northern California and southern Oregon. A combination of literature reviews, field-based studies, and contractor surveys was used to develop a database and equations that are required to model these three components. The volume to be removed, tree size, slope steepness, and skidding/yarding distances were identified as key variables determining fuel reduction thinning treatment cost. The user of this model can estimate fuel reduction treatment costs for a wide range of thinning prescriptions using those key variables. Alternatively, users can enter their own assumptions to customize the tool for their own operations. The net energy output function can allow users to assess potential energy contribution for biomass recovery systems by comparing the amount of energy delivered with the total energy consumed to collect, process, and transport the biomass to an energy plant. Site nutrient removals from thinning treatments were calculated based on the biomass amounts and nutrient contents for each species and the tree components (e.g., limbs, tops, and/or bolewood) to be removed. The outputs can help users to examine the environmental effects of biomass recovery and provide nutrient retention information for sustainable woody biomass production. Additional model validation from future fuel reduction thinning projects would improve user confidence in the model. ThinTool should be a useful analysis program for forest managers and planners when they are developing fuel reduction treatments that are cost- and energy-effective as well as environmentally sound.