Integrating Technoeconomic, Environmental, and Safety Criteria in Solvent Screening for Extraction Processes: The Case of Algae Lipid Extraction

Volatile organic solvents derived from fossil resources are typically used in extraction processes, but this usually involves high energy consumption for solvent recovery and negative environmental impacts due to solvents' hazardous, volatile, and flammable nature. This study presents a systematic approach to solvent screening, using molecular and process simulation techniques, data analysis, and classification methods applying technoeconomic, environmental, and safety criteria. This methodology is demonstrated for lipid extraction from wet algae biomass in biofuel production. First, relevant thermodynamic equilibrium data are predicted with the Conductor-like screening model for real solvents (COSMO-RS) method. The resulting solvents are clustered according to their partition coefficient and selectivity toward the target solute and then screened further, considering their physicochemical properties and health, safety, and environmental (HSE) performance. Finally, the lipid extraction process is simulated in Aspen Plus using all screened solvents to obtain technical, economic, and environmental performance data. Out of 88 initial candidates, cyclohexane, limonene, and ethyl tert-butyl ether are identified as potential alternatives to the benchmark solvent, hexane. While these solvents tend to be more expensive and their recovery is more energy-intensive (higher boiling points) compared to hexane, they have a higher selectivity toward lipids, thus reducing the solvent intensity of the process, and are less volatile and nonhazardous according to the HSE classification. This methodology can be applied to other extraction process applications or implemented at early stages in the process design to evaluate technoeconomic, environmental, and safety trade-offs when considering and selecting more sustainable alternatives to fossil-derived solvents.