The conversion of organic waste into value-added chemicals provides a sustainable pathway toward a circular economy, but anaerobic digestion (AD) as an established technology has faced great challenges primarily due to the low value of its primary productbiogas. Recent developments on arrested methanogenesis allow the AD process to be rewired to suppress methanogenesis and promote the production of higher valued volatile fatty acids (VFAs). However, the separation and recovery of VFAs from the mixed reactor constituents (microbes, salt, and organic solids), remains a challenge. Membrane-based separation processes are showing increased promise compared to other methods, as recent studies reported high yield, high selectivity VFA recovery with low energy consumption and reactor footprint. However, competing membrane processes have not been quantitatively reviewed or compared, making it difficult to understand the current state-of-the-art. This study provided the first such analysis, comparing nanofiltration (NF), reverse osmosis (RO), pervaporation (PV), membrane contactors (MC), and membrane distillation (MD) for VFA separation and recovery. The study offers a comprehensive characterization of the different membrane’s selectivity and permeability under different conditions and compares them side-by-side using normalized measures. In addition, the energy demand and fouling potential were also analyzed. New opportunities such as mixed matrix pervaporation membrane, antifouling electroactive membrane, solar-heating membrane distillation, and integrated processes were also explored to provide insights on technology advancement and synergistic benefits.

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The healthcare industry emits significant amounts of CO 2 and has an imperative need for decarbonization. This study demonstrated a new hybrid electro-enzymatic process that converts waste CO 2 into highvalue C6 pharmaceutical precursor compounds. A novel three-chamber electrolyzer equipped with a Cu-based gas diffusion electrode converted gaseous CO 2 into ethanol at a high current density (40−60 mA/cm 2 ), high selectivity (43−81 mol %), and production rate (368−428 mg/L/h). Purified ethanol from the electrolyzer was then sent to an enzymatic bioreactor where ADH and DERA enzymes upgraded ethanol into C6 statin precursor molecules at high yields (29−35%) via acetaldehyde. Competitive C6 lactol synthesis rates (4.7−5.7 mM/day) and titers (712− 752 mg/L) were achieved, demonstrating the potential of the end-to-end process. The C6 lactol product can seamlessly be converted to statins, a class of lipid-lowering medication that is among the largest selling class of drugs in the world. This hybrid process provides a new pathway for CO 2 valorization to high-value products and accelerates healthcare sector decarbonization.

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