Low-Cost Pebax® 1657/PVDF Membrane for CH₄ Enrichment from Biogas

Biogas upgrading through membrane-based CO₂/CH₄ separation has attracted growing interest as a cost-effective and chemically inert alternative to conventional pressure swing adsorption (PSA) and amine scrubbing technologies. This work presents a systematic performance evaluation of a Pebax® 1657/PVDF composite hollow fiber membrane developed for low-cost CH₄ enrichment from municipal biogas. A full 2×4 factorial design of experiments (DOE) was employed, varying operating pressure over four levels (1.2, 1.5, 1.8, and 2.1 bar) and temperature over four levels (30, 35, 40, and 45 °C). Under optimal conditions (2.1 bar, 45 °C), the membrane achieved 31.2% CH₄ enrichment, 71.8% CO₂ removal efficiency, and a final methane purity of 91.4% from a raw biogas feed containing approximately 55–60% CH₄. Computational Fluid Dynamics (CFD) simulations using SimScale corroborated experimental findings with deviations below 5%. Analysis of Variance (ANOVA) identified membrane presence as the dominant performance variable, accounting for 86.8% of total response variance (F = 1,247.8, p < 0.0001). Temperature and pressure each contributed significantly, with their interaction amplifying CO₂ removal at high-pressure conditions. The fabricated membrane demonstrates strong potential for scalable, low-cost biogas upgrading in distributed energy systems.