A holistic view of biomethane: Insights from a systematic review of biomethane in Ireland

Highlights

•    Biomethane potential is strongly shaped by the national context.

•    Large fluctuations in estimates of biomethane’s energy & carbon abatement potential.

•    Wide range of social, economic, and environmental impacts of biomethane identified.

•    Need for a long-term vision of biomethane within the broader energy system.

Abstract

Biomethane is gaining traction as a renewable alternative to fossil gas. To map the complexity of biomethane as an energy source, we conducted a narrative systematic review of biomethane research in Ireland. Our case study investigates what a biomethane industry could look like in Ireland across the full biomethane lifecycle, and what impacts need to be taken into consideration in its development. From this, we isolated overarching themes that may extend beyond the Irish context. First, we searched the Web of Science and Scopus for the keywords “biomethane Ireland OR Irish” to identify academic literature and Google and Ecosia for grey literature. We then coded the 156 documents fulfilling our inclusion criteria for insights on feedstocks, end uses, infrastructure, cost, abatement potential, and wider impacts. We find that the national context shapes the potential for and impacts of a biomethane industry. In Ireland, grass and slurry from the livestock industry together could provide more than 5 TWh of biomethane. However, there is uncertainty around the scale of biomethane’s energy and carbon abatement potential based on differences in assumptions and system boundaries. Only if manure/slurry is included, does biomethane consistently meet the 80% emissions reduction threshold required for use as heat. Our research also highlights the importance of a socio-ecological systems analysis, as biomethane has socio-ecological impacts that, in Ireland, remain understudied. Finally, we outline the need for a long-term vision of biomethane’s role in the energy system, since it is frequently portrayed as interim solution until other technology matures.