Carbon Emissions Accounting and Techno-Economic Evaluation of Biochar and Organic Fertilizer Production from Distillers' Grains
Distillers' grains, the largest organic solid waste stream in the brewing industry, require efficient low-carbon valorization to support China's Dual Carbon Goals. This study employs life cycle assessment (LCA) to quantify CO2 emissions and carbon reduction benefits of two mainstream routes: pyrolysis to biochar and fermentation to organic fertilizer. Based on public process data, the total life-cycle CO2 emission for biochar production from 1 t of distillers' grains is 250.02 kg, with a carbon sequestration reduction of 120.29 kg, demonstrating superior long-term carbon fixation. In contrast, organic fertilizer production emits 536.14 kg CO2 per ton, achieving a carbon reduction of only 86.22 kg, indicating inferior mitigation performance. Techno-economic analysis reveals net profits of 471.97 CNY/t for biochar and 822.27 CNY/t for organic fertilizer, showing that the organic fertilizer route offers higher profitability. Both pathways effectively reduce CO2 emissions, with biochar prioritizing environmental sustainability and organic fertilizer excelling economically. This study provides data-driven insights for selecting organic solid waste recycling strategies, promoting low-carbon technologies, and establishing circular economy models in the brewing industry.