Abstract
Household biogas can significantly contribute to sustainable energy transition by supporting the decarbonisation and modernization of the cooking energy sector. Nearly 450,000 household biogas plants were reported to have been installed in Nepal as of 2023. This study assesses their sustainability using large-scale household survey data combined with statistical analysis. A face-to-face survey of 2,559 households with biogas plants was conducted across ten districts, spanning the three most inhabited physiographic regions of the country. The interviews were conducted using a structured questionnaire to collect demographic and socio-economic characteristics, information on the functionality of biogas plant components (including from visual inspections), and the reasons, if any, for biogas plant dis-adoption. This study used descriptive and logistic regression analysis to identify factors that influence sustained use and dis-adoption. At the time of the survey, 54% of biogas plants had been abandoned, primarily due to a malfunctioning mixer, the main valve or the gas pipe. Statistically significant contributors to dis-adoption included plant operators having too small a herd of livestock to produce sufficient biogas feedstock, failure to conduct routine digester and outlet cleaning, and lack of post-installation repair and maintenance services. Moreover, many systems that were still in use were not performing optimally, producing only 0.4 m(3)/day of biogas on average. As they have moved away from biogas, households have compensated by increasing use of liquefied petroleum gas (LPG); this effect is estimated to cost 5.2 million USD annually to Nepal's households and implies an increase in CO(2) emissions of 0.66 million tonnes (and global damages of USD 7.6 million). These findings inform recommendations to improve the performance and sustained use of household biogas systems in Nepal and other countries with similar geographical and socio-economic conditions. In particular, a paradigm shift in biogas promotion and support policy is needed, that more seriously considers the demand-driven, subsidy, and dissemination features of interventions, and that engages in thorough monitoring and evaluation to troubleshoot program challenges.