Compressed Biogas (Bio-CNG) from Agricultural Waste: Pathways to a Sustainable Circular Bioeconomy

Abstract

Compressed biogas, commonly termed Bio-CNG, has emerged as a credible route for converting surplus agricultural residues into a transport-grade fuel while addressing waste management, air quality and rural income challenges at the same time. This review synthesises the current scientific literature on Bio-CNG production from agricultural waste, tracing the pathway from feedstock characterisation through anaerobic digestion, biogas upgrading, compression and digestate valorisation. Particular attention is given to pretreatment strategies for lignocellulosic residues, the comparative performance of physicochemical and biological upgrading technologies, and the techno-economic and environmental trade-offs that determine commercial viability. The review also considers how digestate recirculation and nutrient recovery close material loops within a circular bioeconomy framework, and how national policy instruments shape adoption at scale. Persistent barriers, including feedstock logistics, capital intensity and inconsistent pretreatment selection criteria, are discussed alongside emerging solutions such as hybrid upgrading systems and improved digestate management practice. The review concludes that Bio-CNG is a technically mature but economically fragile solution whose further scale-up depends less on new laboratory breakthroughs than on coordinated feedstock aggregation, financing and clearer standards for digestate reuse.