Biomethane Production, Upgrading, and Use from a Systems Perspective

Abstract

This review examines the biomethane value chain from feedstock selection and feedstock-specific pretreatment to digester operation, gas upgrading, utilization pathways, and life-cycle constraints. Rather than evaluating biomethane by methane purity alone, it emphasizes the combined effects of feedstock quality, pretreatment intensity, process stability, upgrading energy demand, methane slip, digestate management, and end-use infrastructure. Key anaerobic digestion variables, including temperature, pH, volatile fatty acids, carbon-to-nitrogen ratio, organic loading rate, hydraulic retention time, and inhibitor control, are linked to process robustness. Major upgrading technologies, including water scrubbing, chemical absorption, pressure swing adsorption, membrane separation, and cryogenic separation, are compared in terms of methane purity, methane loss, energy demand, cost tendency and deployment fit. Biomethane shows the strongest mitigation potential when wastes are locally sourced, methane losses are controlled and digestate is safely recycled.