Biogas-Fueled Internal Combustion Engines for Sustainable Energy Applications

The global imperative to transition away from fossil fuels has intensified research into renewable energy carriers compatible with existing combustion engine infrastructure. Biogas, produced through the anaerobic digestion of organic waste streams, offers a chemically versatile, carbon-neutral fuel whose primary constituent—methane (CH₄, 50–75%)—is directly suitable for internal combustion engine (ICE) applications. This paper presents a comprehensive investigation of biogas as a fuel for spark-ignition (SI) and compression-ignition (CI) engines, encompassing feedstock characterization, biogas production and upgrading processes, engine performance analysis, combustion thermodynamics, and emission profiles. Experimental data from a 7.5 kW single-cylinder SI engine operating on biogas at varying CH₄ concentrations (55%, 65%, and 75%) and compression ratios (8:1, 9:1, and 10:1) are reported and analyzed. Results demonstrate that 75% CH₄ biogas at a compression ratio of 10:1 yields a brake thermal efficiency (BTE) of 28.6%, approaching compressed natural gas (CNG) performance benchmarks, while achieving CO₂-equivalent emissions 62% lower than diesel baselines. The paper further evaluates dual-fuel CI engine configurations and biogas-CNG blending strategies. Techno-economic analysis of three deployment scenarios—agricultural farm, municipal solid waste plant, and sewage treatment facility—demonstrates levelized cost of electricity (LCOE) ranging from USD 0.087 to USD 0.134/kWh, competitive with grid electricity in many developing regions. The findings affirm Biogas-fueled ICEs as a technically mature, economically viable, and environmentally beneficial pathway for decentralized sustainable energy generation.