Solvent Screening Methodology considering Techno-Economic and Environmental Sustainability criteria for Algae Lipid Extraction

Abstract

Abstract Solvent extraction plays a crucial role in biorefinery processes, such as the extraction of lipids from algae biomass to produce biodiesel. Volatile organic solvents, such as hexane, are typically used to extract algae lipids, but this involves high energy consumption for solvent recovery and negative environmental impacts due to its hazardous, volatile, and flammable nature. This study proposes a systematic methodology combining molecular simulation techniques, data classification methods, and process simulation to screen solvents for lipid extraction from wet algae biomass. The novelty relies on the integration of techno-economic, environmental and safety criteria, such that all three sustainability dimensions are considered in solvent selection. First, thermodynamic equilibrium data of solvent-lipid systems are predicted with the COSMO-RS method. Then, a clustering method (K-means algorithm) is used to identify and select the solvents with the highest partition coefficient and selectivity towards lipids. After this, the selected solvents are further screened considering their physicochemical properties (solubility in water, density, viscosity, boiling point) and health, safety, and environmental performance. Finally, the lipid extraction process with the shortlisted solvents is simulated in Aspen Plus to obtain techno-economic and environmental sustainability performance indicators. Out of 88 initial solvent candidates, limonene and ethyl tert-butyl ether are identified as promising alternatives to the benchmark solvent (hexane), as they are non-hazardous and have higher selectivity towards lipids. However, their use involves higher energy requirements, operating costs, and greenhouse gas emissions in the lipid extraction process. This methodology can be applied to other extraction processes to find sustainable alternatives for the conventional solvents and identify trade-offs from a techno-economic and environmental perspective at the early stages of process design.