Impact of Process Emissions on Climate Offsets by Different Biochar Production Methods: Progress Report

This progress report describes work to develop a flexible spreadsheet algorithm for estimating greenhouse gas footprints, carbon-equivalent offsets, and carbon payback periods for different biochar production technologies and alternative biomass scenarios. The model incorporates factors such as biochar carbon efficiency, methane emissions, nitrous oxide and soot emissions, feedstock moisture, bioenergy co-production, biomass decomposition, wildfire scenarios, and soil organic matter effects. By the time of reporting, the project had added global warming potential calculations for nitrous oxide and soot, compiled emissions and production data for 23 biochar production methods, and developed several alternative biomass scenarios. Early results showed that climate outcomes depended strongly on the alternative fate of the biomass. For one modern slow pyrolysis method, biochar production required a 40-year payback period compared with natural biomass decay, but produced immediate carbon-equivalent benefits compared with efficient bioenergy combustion or wildfire. The report also notes plans for a peer-reviewed manuscript and open-source spreadsheet and coded versions of the algorithm.