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Techno-economic and environmental assessment of microwave-assisted catalytic pyrolysis of biomass Zhu, Hui


The conversion of abundant under-utilized forest residues into biofuels is a promising strategy for transitioning the energy structure and for decarbonizing the transportation sector. As one of the emerging thermo-chemical conversion technologies, microwave-assisted catalytic pyrolysis (MACP) is able to efficiently convert solid biomass into valuable products, including bio-oil (~36 wt%), biochar (~28 wt%) and non-condensable gas (NCG) (~36 wt%). As well as resolving technical obstacles, MACP was also assessed for its economic and environmental impact, at a systematic level, for the purpose of commercialization. The work described in this study involved a techno-economic assessment (TEA) and a life cycle assessment (LCA) based on process integration. This was used to evaluate the economic feasibility and environmental impact of a hypothetical MACP system for the co-production of biofuel and biochar from forest residues in British Columbia (BC). The minimum selling price (MSP) of MACP biofuel was shown to be $1.01/L, indicating that MACP biofuel was still not priced competitively to petroleum fuels. The on-site utilization of NCG and integration of an upgrading process helped achieve self-sufficiency in heat and hydrogen supply, but raised concerns about high capital costs. Sensitivity analysis suggested that future research efforts should focus on improving the process performance and reducing the capital investment to bring down the MSP. However, LCA results suggested that an MACP system could potentially make a considerable contribution to reducing greenhouse gas (GHG) emissions of transportation fuels. The cradle-to-gate (CTG) carbon intensity (CI) of MACP biofuel was shown to be -57.6 g CO2-eq/MJ, indicating that a carbon-negative system could be achieved with a GHG emission reduction of 162% compared to petroleum fuels. The key reasons were the green electricity mix and carbon sequestration of co-product biochar. The dominant influence was shown to be biomass-to-biofuel conversion step which accounted for 47.3% of the GHG emissions produced. Besides, the conversion efficiencies and location specific parameters also had significant impacts on the CI of MACP derived biofuels.

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