Assessing greenhouse gas emissions and decarbonization potential of household biogas plant: Nepal's case study

Household biogas plants (HBPs) are widely promoted in developing countries like Nepal to decarbonize the cooking fuel sector, mitigating greenhouse gas (GHG) emissions associated with traditional, non-clean cooking fuels. However, their decarbonization potential mainly relies on the overall GHG emissions associated with HBP and the avoidable emissions to be substituted by the HBP, and there is a lack of systematic studies evaluating these emissions under Nepalese context. This study addresses this gap, probably for the first time in Nepal, by analyzing GHG emissions associated with HBP, assessing their decarbonization potential under various operational conditions, and identifying opportunities to enhance the potential. Using a life cycle assessment (LCA) approach, we examined the decarbonization potential of HBPs and evaluated the impact of their operational uncertainties through sensitivity analysis. Our results indicate that HBPs could decarbonize the cooking fuel sector in Nepal by around 150,000 kt of CO2 equivalent annually; however, GHG emissions from about two-third of HBPs exceeded avoidable emissions, hindering their overall decarbonization potential. To improve this potential, we recommend strategies such as effective operation and maintenance, efficient digestate utilization, and context (regional, socioeconomic etc.) specific intervention policies such as biogas yield enhancement through codigestion of locally available feedstock. These findings provide valuable insights for policymakers aiming to assess and enhance the decarbonization potential of HBPs in Nepal and other parts of the developing countries under similar contexts.