Decarbonisation Technology August 2026 Issue

feedstocks, including agricultural residues, livestock manure, municipal organic waste, and wastewater sludge. This offers a unique opportunity to simultaneously reduce greenhouse gas emissions, strengthen domestic energy production, improve waste management, and reduce dependence on imported fossil fuels. As countries seek practical, scalable solutions to complement existing infrastructure, biomethane is increasingly being recognised not only as a decarbonisation fuel but also as a strategic energy security asset. Biomethane and Bio-CNG Biomethane and bio-CNG represent critical upgraded forms of biogas within the renewable gaseous fuel ecosystem, enabling the integration of organic waste-derived energy into existing natural gas infrastructures. Biogas is primarily composed of methane (CH₄: 50- 65%), carbon dioxide (CO₂: 35-50%), and trace components including hydrogen sulphide (H₂S), water vapour, and siloxanes. Due to its relatively low methane concentration and impurities, raw biogas is typically used on-site for heat and power generation. “ Biomethane and bio-CNG represent critical upgraded forms of biogas within the renewable gaseous fuel ecosystem, enabling the integration of organic waste-derived energy into existing natural gas infrastructures ” Biomethane, often referred to as renewable natural gas (RNG), contains 95-99% methane, making it chemically and functionally equivalent to fossil natural gas. This high-purity gas can be injected into existing natural gas grids or liquefied and compressed. Bio-CNG is biomethane that is compressed to high pressure (typically 200-250 bar) for use as a transport fuel. It serves as a direct substitute for conventional CNG in internal combustion engines, particularly in heavy-duty transport fleets. In terms of end-use sectors, biogas is mainly utilised in distributed combined heat and power (CHP) systems, industrial heat applications, and rural electrification. Biomethane extends

usage into residential and industrial gas networks, power generation, and grid balancing services. Bio-CNG is primarily deployed in the transportation sector, including buses, trucks, and municipal vehicle fleets, offering a low- carbon alternative to diesel and gasoline. Biomethane and bio-CNG are fully compatible with conventional natural gas or CNG, respectively, and are accepted as drop-in fuels. They utilise identical infrastructure, including pipelines, storage systems, and compression stations, while offering significantly lower lifecycle greenhouse gas emissions. This compatibility positions renewable gases as a strategic decarbonisation lever within existing gas-based energy systems, supporting gradual transition pathways without requiring large- scale infrastructure replacement. Biomethane production technologies Biomethane production is mainly based on the conversion of organic residues into methane- rich gas through biological or thermochemical pathways (see Figure 1 ). The most established route is anaerobic digestion, which can process a broad range of wet biomass streams, including agricultural residues, animal manure, municipal organic waste, food waste, and wastewater sludge. Agricultural residues, such as straw, crop stalks, and agro-industrial byproducts, represent abundant non-food resources. However, their lignocellulosic structure may limit hydrolysis and often requires pretreatment. Animal manure is a conventional and widely available feedstock that supports stable digestion due to its moisture content and microbial activity. Municipal organic waste and food waste generally provide high methane potential because of their readily biodegradable organic fraction, while wastewater sludge is commonly treated in existing municipal infrastructure and can be co-digested with other organic wastes to improve energy recovery ( Neri, et al., 2023) (Alengebawy, et al., 2024) . Anaerobic digestion is a multi-stage microbial process occurring in the absence of oxygen. Complex organic matter is first hydrolysed into soluble compounds, then converted through acidogenesis and acetogenesis into volatile fatty acids, hydrogen, and acetate. In the final