Integrated Techno-Economic and Environmental Assessment of a Decentralized Biochar System Using Agricultural Residues

초록

This study presents an integrated techno-economic and environmental assessment of a decentralised 1 ton/day biochar production system using agricultural residues. A small-scale configuration including feedstock collection, pelletisation, and torrefaction was designed based on experimental data and literature-derived parameters. Capital expenditure was estimated using equipment scaling methods, and operating costs were calculated from market-based unit prices. Economic performance was evaluated through discounted cash-flow analysis and Monte Carlo simulation over a 20-year horizon. The capital structure was dominated by the torrefaction reactor and indirect installation costs, while operating expenditure was primarily driven by labour, followed by thermal and electricity demand. Under baseline assumptions, the project achieved a positive net present value and an internal rate of return exceeding the 5% discount rate, indicating moderate feasibility. However, scenario and probabilistic analyses revealed strong sensitivity to labour intensity and transportation costs. A cradle-to-gate life cycle assessment focusing on global warming potential was conducted using the Brightway2 framework. Off-gas energy recovery was incorporated into process heat demand to avoid carbon double counting. Although biogenic CO2 treatment significantly affected absolute GWP values, electricity and process heat consistently emerged as the dominant environmental hotspots. The integrated results indicate that economic performance is labour-driven, whereas environmental performance is governed by utility demand, highlighting complementary optimisation pathways for improving decentralised biochar sustainability.

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