Life-cycle assessment and techno-economic analysis of biochar produced from forest residues using portable systems

摘要

Purpose Producing biochar from forest residues can help resolve environmental issues by reducing forest fires and mitigating climate change. However, transportation and storage of biomass to a centralized facility are often cost-prohibitive and a major hurdle for the economic feasibility of producing biobased products, including biochar. The purpose of this study was to evaluate the environmental impacts and economic feasibility of manufacturing biochar from forest residues with small-scale portable production systems. Methods This study evaluated the environmental performance and economic feasibility of biochar produced through three portable systems (biochar solutions incorporated (BSI), Oregon Kiln (OK), and air curtain burner (ACB)) using forest residues in the United States (US). Cradle-to-grave life-cycle assessment (LCA) and techno-economic analysis (TEA) were used to quantify environmental impacts and minimal selling price (MSP) of biochar respectively considering different power sources, production sites, and feedstock qualities. Results and discussions The results illustrated that the global warming (GW) impact of biochar production through BSI, OK, and ACB was 0.25-1.0, 0.55, and 0.61-t CO(2)eq/t biochar applied to the field, respectively. Considering carbon-sequestration, 1-t of biochar produced with the portable system at a near-forest site and applied to the field reduced the GW impact by 0.89-2.6 t CO(2)eq. For biochar production, the environmental performance of the BSI system improved substantially (60-70%) when it was powered by a gasifier-based generator instead of a diesel generator. Similarly, near-forest(off-grid) biochar production operations performed better environmentally than the operations at in-town sites due to the reduction in the forest residues transportation emissions. Overall, the net GW impact of biochar produced from forest residues can reduce environmental impacts (i.e., 1-10 times lower CO(2)eq emissions) compared with slash-pile burning. The MSP per tonne of biochar produced through BSI, OK, and ACB was $3,000-$5,000, $1,600, and $580 respectively considering 100 working days per year. However, with improved BSI systems when allowed to operate throughout the year, the MSP can be reduced to below $1000/t of biochar. Furthermore, considering current government grants and subsidies (i.e.,$12,600/ha for making biochar production from forest residues), the MSP of biochar can be reduced substantially (30-387%) depending on the type of portable system used. Conclusion The portable small-scale production systems could be environmentally beneficial and economically feasible options to make biochar from forest residues at competitive prices given current government incentives in the US where excess forest biomass and forest residues left in the forest increase the risk of forest fires.