A comparative study of biogas and biomethane with natural gas and hydrogen alternatives

Abstract

Biogas and biomethane are renewable fuels that can help to reduce greenhouse gas (GHG) emissions. However, their supply chains emit methane (CH₄), a potent GHG. This study explores the role of biomethane and biogas supply chains in decarbonising the energy system by comparing their life cycle emissions to alternative scenarios. These alternatives consider the entire life cycle emissions from different ways of treating biodegradable waste rather than anaerobic digestion (upstream), producing natural gas or hydrogen instead of biogas and biomethane (midstream), and using synthetic fertiliser instead of digestate (downstream). We present 22 life cycle assessment (LCA) GHG intensity models for biomethane and biogas and compare them with three primary counterfactual scenarios based on various midstream stages aimed at compensating for biogas and biogas generation. Our findings reveal that biogas and biomethane supply chains achieve an average of 51–70% and 42–65% GHG savings compared to midstream natural gas and all hydrogen production routes, respectively. Conversely, low-carbon green hydrogen at the midstream stage counterfactual scenario outperforms biomethane and contribute to an average of 13–24% GHG savings. Overall, the study suggested that biogas and biomethane have the potential to play a role in reducing GHG emissions as a cleaner and sustainable alternative to fossil fuels, but they are not the lowest-emission option.