Toward low-carbon biofuel systems: Scale-dependent sustainability of solvent-aided crystallization for biodiesel purification

This study evaluates the environmental sustainability of solvent-aided crystallization (SAC) for biodiesel purification using a gate-to-gate life cycle assessment (LCA) integrated with techno-economic interpretation. The environmental performance of SAC was investigated across laboratory (10 L), bench-pilot (50 L), pilot (100 L), and pre-commercial (500 L) scales using experimentally validated mass and energy balances. Global warming potential (GWP) was selected as the primary environmental indicator and quantified using Ecoinvent v3.8 and IPCC 2021 characterization factors. Results showed that GWP decreased significantly with process scale-up, from 0.1472 kg CO₂-eq/L at laboratory scale to 0.0149 kg CO₂-eq/L at the 500 L configuration, corresponding to an overall reduction of approximately 89.9%. Electricity consumption was identified as the dominant environmental hotspot, contributing between 94–99% of total emissions. Sensitivity analysis confirmed that the overall environmental trends remained robust under ±20% variation in electricity-related parameters and solvent recovery assumptions. Comparative benchmarking demonstrated that SAC achieved 23.5% and 31.5% lower GWP than conventional water washing and dry washing purification methods, respectively, at pre-commercial scale. These findings confirm SAC as a scalable, low-water, and environmentally sustainable biodiesel purification technology.