Life Cycle Assessment of Black Soldier Fly Technology for Sustainable Manure Management in Jing-Jin-Ji: Balancing Feed Protein Production and Carbon Mitigation

The Jing-Jin-Ji region in China has highly intensive agriculture but faces challenges of feed protein shortage and manure surplus, threatening environmental sustainability and industrial development. The black soldier fly (Hermetia illucens) is a promising sustainable feed protein source, capable of efficiently converting organic waste into high-quality insect protein to alleviate feed scarcity while mitigating waste pollution. Existing research on black soldier fly (BSF) treatment in this area is limited, lacking comprehensive benefit evaluations. This study, conducted in Hebei Province, integrated sub-county-scale manure resource mapping, life cycle assessment, and economic assessment to compare traditional composting with BSF-based manure management. Results show BSF treatment can produce 0.36 to 0.39 teragrams (Tg) of feed protein per year. Compared with conventional composting, BSF treatment reduced direct manure-treatment emissions, while additional mitigation benefits were obtained through feed-protein substitution, fertilizer substitution, and BECCS-related land-use savings. Overall, the BSF scenarios achieved a total GHG mitigation potential of 2.85–6.19 Tg CO2eq yr−1. Economically, low-technology BSF production is cost-competitive, with a total cost of $121 for treating 1 ton of fresh chicken manure. With its protein output roughly doubling the local soybean production capacity, BSF technology provides a viable, low-carbon solution to the dual challenges of feed security and waste management in intensive agricultural systems.