Utilization of forestry waste materials in British Columbia: Options and strategies

The Canadian province of British Columbia has large forestry resources and therefore provides an informative example of the potential role of bioenergy in mitigating GHG emissions. Even in biomass-rich British Columbia, forestry resources are only sufficient to meet part of the energy demand. This paper compares different energy conversion routes for forestry waste materials: via hydrothermal liquefaction, thermochemical methanol and bioethanol, renewable natural gas, cogeneration of heat and power, heat-only boilers, and power-only generation. The GHG savings, health impacts, minimum selling prices, and GHG abatement costs for each option are estimated by combining life cycle assessment with a discounted cash flow model. The input-based functional unit of 1 oven-dry tonne biomass provides a better basis for comparing possible uses of finite biomass supply than the commonly-used output-based functional unit of 1 GJ bioenergy. Heat-only boiler for district heating gives the highest GHG reduction of 960 kgCO2-eq per oven-dry tonne feedstock, while power-only generation delivers minimal GHG benefit in British Columbia. Heat-only boiler and cogeneration offer the lowest GHG abatement costs (<$-20/tCO2-eq), due to lower costs and higher energy conversion efficiencies, and are already economically viable, but will not use all the available resources because health impacts generated by biomass combustion limit their deployment, despite life cycle health benefits for avoiding hazardous emissions from slash burning of forestry waste materials. Refined biofuel options are much less cost-effective (>$50/tCO2-eq); further technology improvement and policy support are needed to offset the cost disadvantage.