Dual-Carbon Flow Life Cycle Assessment of Mussel Aquaculture in Shengsi, Zhejiang: Decoding the Carbon Footprint of China’s Largest Mussel Production Base

The climate impact of bivalve aquaculture remains inadequately quantified for China, the world’s dominant producer. Prevailing carbon footprint assessments often overlook the complexity of biological carbon flows and fail to capture effects that evolve across different timescales. To address these gaps, we developed a novel multi-temporal dual-carbon flow life cycle assessment framework that systematically quantifies both the anthropogenic (ACF) and biological (BCF) carbon footprints and evaluates the climate impacts across different time horizons. Applied to China’s largest mussel farm, the framework reveals the system’s total carbon footprint decreases from +261.7 kg CO2-eq/t under a conventional Cradle-to-Gate perspective to +84.6 kg CO2-eq/t over a centennial scale and further to +27.9 kg CO2-eq/t over a geological timescale. With the ACF constant across all timescales (+256.2 kg CO2-eq/t), the transition in total carbon footprint is driven entirely by the BCF. The BCF changes from a minor positive contribution during farming (+5.5 kg CO2-eq/t, from enhanced sea-to-air CO2 efflux) to a major net sink at centennial (–171.6 kg CO2-eq/t ) and geological (–228.3 kg CO2-eq/t) scales, primarily due to long-term carbon sequestration from shell removal, burial, and weathering. Consequently, the net carbon footprint is not a fixed attribute but a function of temporal perspective, controlled decisively by shell-waste management. Aligning the industry with climate goals thus requires not only reducing the ACF through material and energy efficiency during the production chain but, crucially, also diverting shells from incineration to burial or weathering pathways to secure their long-term sink potential.