Enhancing woodchip utilization through resource circulation: environmental and economic trade-offs among thermochemical pathways

This study presents an integrated assessment framework to identify an optimal thermochemical conversion pathway for woodchip utilization by comparing combustion, pyrolysis, and carbonization through rigorous process design and simulation. The aim of this study is to evaluate and compare the environmental and economic performance of thermochemical technologies for the selection of biocarbon resource utilization strategies. Environmental performance was evaluated using a gate-to-gate life cycle assessment of CO2 emissions, while economic performance was assessed through techno-economic analysis (TEA). The robustness of each process was further evaluated through sensitivity analysis considering key parameters, including woodchip cost, electricity price, carbon price, and carbon black (CB) price. The results reveal a clear trade-off between environmental and economic performance. Combustion is the most economically favorable pathway, driven by high electricity generation, but results in the highest CO2 emissions. In contrast, pyrolysis reduces net CO2 emissions through biochar sequestration; however, its economic viability is limited by the low market value of biochar. Carbonization demonstrates a more balanced performance by producing a higher-value carbon black-like (CB) material while achieving the lowest CO2 emissions. At a current CB price of 0.940 USD/kg, the net income is estimated at 13 USD per tonne of woodchips. Increasing the CB price to 1.18 USD/kg makes carbonization economically comparable to combustion. These findings highlight the importance of product value in determining economic feasibility and suggest that carbonization, as an emerging thermochemical pathway, represents a promising option for environmentally favorable and high-value utilization of woodchips as a bioresource.