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As Rwanda’s rapid population growth leads to increased energy demand, the government is pushing for a shift from the most used traditional energy source, firewood, to more sustainable alternatives. Household biogas digesters are installations that produce biogas and bio-slurry through the anaerobic digestion of organic waste. Biogas can be used for domestic cooking and lighting, while bio-slurry can be used as a high quality fertilizer for crops or plants. The Rwandan government launched a heavily subsidized National Domestic Biogas Program from 2007 to 2016 to install an initial target of 100,000 biodigesters by 2017. However, only 11,625 biogas plants were installed by 2021, of which 85% were abandoned or non-functional. Nevertheless, numerous biogas projects run by non-governmental organizations, including Vétérinaires Sans Frontières Belgium (VSF-B) and Imbaraga, have continued to promote the biogas technology. Therefore, this thesis researches the effectiveness of the EVE I and II projects implemented by VSF-B and Imbaraga in four districts of the Southern Province of Rwanda from 2014 to 2020. Within their area of operation, the most influential factors on biodigester functionality and the most prominent socio-economic benefits and costs for households are explored. Data collection was done through surveys with Rwandan biodigester users (n=116) and their neighboring farmers without digesters (n=85). Random sampling was carried out within the study area, which includes the districts of Huye, Nyamagabe, Nyanza and Ruhango. Additional interviews were done with the constructors of the biogas plants (n=6), a governmental representative of the biogas program, a representative of Imbaraga and a representative of a local Saving and Credit Cooperative (SACCO). Data was analyzed both descriptively and more in-depth using a binomial logistic regression model. The functionality rate of the biodigesters in this study is 73%, which is significantly higher than the national figure. This research found that the number of cattle per household and the presence of zero grazing had the most significant positive impact on the functionality rate. The limited availability of water to feed the digester was also found to be a critical factor. As a result, the struggle to feed the digester with sufficient raw materials resulted in low biogas production, with an average of only 40% of weekly cooking needs being met by biogas. In addition, the short life cycle of the CANVAS digesters was found to be the cause of the low functionality rate in Nyamagabe, as 82% of the digesters here were of the CANVAS type. Also, only 61% of all CANVAS digesters were functional, compared to 80% for the fixed dome type. VSF-B and Imbaraga achieved this high performance rate by distributing water tanks, improving the construction of stables with cement, and reducing the interest rates on biodigester loans from 24% to 16% through a guarantee fund at local SACCOs. Other recommendations to mitigate feedstock insecurity include the inclusion of pig manure and other organic waste in the biodigester feed, connecting toilets to the biogas plants, collecting cow urine in redesigned stables, and integrating digesters with aquaculture. Targeting the right farmers, monitoring livestock trends, commercializing bio-slurry, and considering carbon revenues as a way to attract investment may be useful for successful further uptake of the biogas sector in Rwanda.

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The heavy reliance on firewood and charcoal in household energy consumption, combined with the use of inefficient cooking stoves and low forest productivity, has resulted in unsustainable biomass utilization and socio-economic and environmental issues in Rwanda. In response, the Rwandan government has committed to achieving a sustainable balance between the demand and supply of woody biomass by 2030, by replacing inefficient cooking technologies with cleaner alternatives and increasing biomass supply through sustainable forest management. As part of the DeSIRA research project, which aims to scale up the use of sustainable biomass in the Eastern Province through effective agroforestry practices, this study updates and improves the biomass demand and supply model developed by MININFRA for Rwanda in 2018, tailoring it to the context of the Eastern Province. The developed model incorporates newly collected data on biomass import and export and estimates the energy potential of crop residues based on existing data. These analyses are performed using the Long-Range Energy Alternatives Planning (LEAP) software, which enables long-term energy planning and allows for various energy scenario analyses. The findings of this master’s thesis show that traditional biomass use still dominates the energy demand in the Eastern Province. Wood sources account for 90.23% of the energy demand, while charcoal contributes 5.46%. Rural households (79.96%) and urban households (17.03%) have the largest share of the energy demand. The results on biomass trade in Rwanda indicate that 15.27% of the consumed charcoal in the Eastern Province is imported from other provinces. Consequently, in 2022, more than 31.1 million GJ of energy was required to meet the energy demand in the Eastern Province, with 30.4 million GJ coming from biomass consumption. However, it was discovered that only 37% of this energy demand can be covered by a sustainable supply of wood resources in the Eastern Province. Furthermore, the findings suggest that in a business-as-usual scenario, the energy demand is expected to double to nearly 50 million GJ by 2050. This results in an increasing gap between biomass demand and supply in the Eastern Province, growing from 38,699 Mg of wood in 2022 to 3,612,038 Mg in 2050. Among the proposed energy scenarios, a rapid transition to clean cooking fuels (CCF scenario) proves to be the most effective in reducing the biomass gap to zero by 2030. However, more action is needed in the long term, as population growth is expected to increase the wood deficit to 16,988 Mg by 2050 under the CCF scenario. Additionally, this study identifies the significant energy potential of crop residues as a substitute for wood or as a source for biofuels. The Eastern Province theoretically has the capacity to produce 24.7 million GJ of energy annually from available surplus crop residues, accounting for 79.39% of the total energy consumption in the province. The energy potential of the banana crop, in particular, is immense. However, further research is needed to assess the effects of removing crop residues from fields on soil health and fertility, as well as the necessary infrastructure and conversion processes involved in leveraging the energy potential of the banana crop.