From Dung to Joules: Household Biogas Production and Use as a Socio-Technical System in Rwanda

Licentiatavhandling, 2026

Household-scale biogas technology is widely designed and promoted as a decentralised clean-cooking intervention in energy-poor communities. It is promoted in the framework of advancing Sustainable Development Goal 7 (SDG 7), particularly its indicator SDG 7.1.2 which tracks the proportion of the population with primary reliance on clean fuels and technologies for cooking. Beyond potential cooking fuel substitution, biogas systems can generate context-specific co-benefits: improved bio nutrient recycling through bio-slurry use for improved crop production (SDG 2), reduced exposure to household air pollution in cooking areas (SDG 3), time saving that may support women’s economic and educational opportunities where cooking and fuel collection are gendered responsibilities (SDG 5), capturing methane emissions from enteric fermentation of unmanaged cow dung (SDG 13), and reducing pressure on forests associated with tree cutting for cooking fuelwood ( SDG 15). Despite these promises, evidence from the sub-Saharan Africa indicate that the sustained use and functionality of the technology are limited, thereby constraining its expected benefits in a region with substantial clean-cooking access deficits. Existing literature provides limited explanation for why widespread deployment of small-scale biogas systems has not delivered anticipated benefits, especially regarding the influence of household livelihoods on technology use.

Using Rwanda as a case for the study, this thesis addresses this gap by analysing household biogas technology as a socio-technical system. The main body of the thesis is developed through two complementary analytical components: (i) a stratified survey that integrates thematic interpretation of user narratives with descriptive analysis of their closed-ended responses, and (ii) examination of behavioural, operational, and technology utilisation patterns interpreted through a household livelihoods framework. These core analyses are supported by two auxiliary mechanisms. First, a metering system was conceptualised and deployed to generate time-stamped traces of technology utilisation. Second, these utilisation traces were quantified to analyse household biogas consumption and venting, and the vented biogas was converted into household-level CO₂e estimates. Together, these approaches reveal behavioural and operational patterns that can undermine or promote the intended benefits of household biogas systems.

A countrywide survey revealed that about 9% of sampled household biogas plants remained fully functional, 70 % had been abandoned, while other plants remained in transitional conditions. Interpretive analysis from user narratives indicate that two themes dominated abandonment: (i) feasibility-assessment deficits arose where eligibility for household biogas support was reduced to oversimplified “two heads cattle + access to water” criterion, overlooking underlying household conditions and cross-sector policies that influence technology operation and use, (ii) unmet user expectations arising from insufficient raw biogas firepower, un expected labour requirements for the technologies daily operation, and limited mechanical robustness of locally fabricated biogas stoves which are often unsuitable for cooking Rwandan staple dishes. Triangulated analysis, interpreted through a household livelihood lens, revealed divergent patterns of technology utilisation. Regular operation and sustained use of the system were more feasible in households where cattle were kept indoors on consolidated land, with reliable water access and stable year-round household composition, whereas fragmented landholdings and fluctuating household size reduced available labour, constrained operation and biogas output, hence leading to intermittent system use. Where household biogas systems were sustained, the continued use appeared to be influenced by: the perceived agronomic benefits of bioslurry within mixed crop–livestock systems, improved kitchen cleanliness, and the relatively faster ignition process of biogas compared to firewood or charcoal for preparing light breakfasts under morning time constraints. Longitudinally metered data revealed heterogeneous patterns of biogas utilisation across households, including periods of underutilisation resulting in venting and associated greenhouse gas emissions. The monthly average emissions from HHs using 8m3 biodigester were estimated at ≈ 33–56 kg CO₂e per household per month (≈ 0.4–0.7 tCO₂e per household per year). Nevertheless, underutilisation did not necessarily imply the availability of surplus biogas following the satisfaction of household cooking energy demand or the complete substitution of conventional fuels. Instead, biogas was used selectively for certain dishes, while fuelwood or charcoal remained in use for others, resulting in only partial displacement of solid biomass fuels. This underscores the centrality of household livelihood dynamics within technology-user communities in shaping the design of more context-responsive clean cooking interventions, programmes, and policies.