(707d) Sustainable Upgrading of Food Waste Derived Biogas By Deep Eutectic Solvents

Problem Statement: Anaerobic digestion (AD) of food wastes in one of the most promising pathways to convert wastes to value added fuels (e.g., biogas) and products (e.g., fertilizer). As food wastes are heterogeneous and its composition varies from household-to-household, the resulting biogas composition varies significantly. Biogas from food wastes often contains 40-60% CO₂ and 1-5% other gases including H₂S. Due to the large concentration of impurities, upgrading of biogas from food wastes is required prior to use or injection into a natural gas pipeline. Common biogas scrubbers are able to reduce H₂S and water vapor but separation of CO₂ from CH₄ requires additional attention.

Proposed Solution: CO₂ from gaseous stream can be separated by physical (ionic liquid) or chemical solvents (amine-based solvents). Amine-based chemical solvents have higher adsorption capacity but are often expensive to regenerate and are often toxic for the environment. Meanwhile, physisorption solvents are often expensive and their adsorption capacity is lower meaning that significantly higher amount of physisorption solvents are required. In this study, deep eutectic solvents (DES) are evaluated to upgrade biogas. The benefit of DES is that they are made from the physical mixing of hydrogen bond donor (HBD) and hydrogen bond acceptor (HBA), generally made from a quaternary salt and acid/alcohols. In this study, conductor like screening model (COSMO) is adopted to screen suitable HBA and HBD for biogas based on hydrogen bond properties using a TZVP basis set. This model is evaluated compared to literature experimental studies as well to verify integrity of the results.