Holistic Comparison of Hydrothermal Carbonization versus Slow Pyrolysis for Biochar Production: Techno-economic Analysis and Life Cycle Assessment

Biochar has emerged as a promising sustainable alternative to fossil fuels. Among various production technologies, hydrothermal carbonization (HTC) and slow pyrolysis (SP) have become particularly critical due to their distinct process advantages and scalability. This study holistically compares the economic viability and environmental sustainability of these two biochar production processes. The performance of both processes in producing biochar is evaluated through life cycle assessment (LCA) and techno-economic analysis (TEA). The results reveal that the minimum price of biochar produced by HTC is 0.0063 USD/MJ, which is 23.2% lower than that of the SP process. While the cradle-to-gate LCA shows that HTC performs worse in certain environmental impact categories, its overall environmental burden remains markedly lower compared to SP. Sensitivity analysis further investigates the influence of various economic and process-related factors on the minimum price and environmental impact. Uncertainty analysis indicates a 71.8% probability that HTC will be the environmentally preferred option, with 30% lower price variability compared to SP. HTC demonstrates superior economic and environmental sustainability in the production of biochar. This study aids decision-makers in selecting the optimal biochar production technology, considering both economic and environmental factors.