This study investigates the benefits and limitations of small-scale biogas technology at the household level in rural Sub-Saharan Africa. A literature study and a case study were done to explore if small-scale biogas production is a viable source of electricity in rural Sub-Saharan Africa. The results show that using cattle manure as feedstock requires a daily substrate flow of 750 L of the diluted substrate, i.e. 250 kg of manure and 500 L of water for a 24-hour electricity supply, using a 2-kW generator. This requires a minimum herd size of 25 cattle. Most households don’t have so many cattle. However, a herd of 10 cattle provides enough biogas to power several electrical appliances, significantly improving the household's energy situation. The study concludes that the uptake of biogas technology in Sub-Saharan Africa is slow. Common barriers include inadequate substrate supply, lack of water and variable temperatures, high initial costs, poor technical quality, intense labour operations and maintenance, and insufficient policy support. Improved uptake of biogas technology in Sub-Saharan Africa requires establishing national institutional frameworks and supporting policies, collaboration with the intended users of the technology and local support organisations, ensuring long-term local availability of spare parts and supplies, and, when household-level access to feedstock is limited, centralise biogas systems on the village level to combine feedstock into one production system.
This paper examines common barriers limiting the implementation of small-scale biogas systems in rural Southern Africa through a literature study and a case study of six small-scale biogas digesters installed in Maputo province in Mozambique. The study strives to understand why the implementation rate of small-scale biogas systems in rural Southern Africa is so limited despite favourable conditions. The literature study identified several common barriers to the successful implementation of small-scale biogas in rural Southern Africa related to financial, technical, socio-cultural, and institutional issues. The case study results show that only one digester was operational, and five failed and were abandoned. Low technical ability of constructors results in poor-quality installations. Lack of technological know-how and local capacity for operation and maintenance of digesters are primary reasons for the failure of the digesters. Possible solutions are to intensify research, demonstration, dissemination and application of small-scale biogas; adapt the design of biogas digesters to the local context, meeting the needs of users and using locally available materials; sharing knowledge and information about small-scale biogas technology and its potential would contribute to improving the rate of successful implementation in Southern Africa.
In this study, we investigated the biomethane potential of cassava peels from the four most common varieties of cassava grown in Inhambane Province in Mozambique, Chinhembue, Cussi, Cizangara and Nhassumbi. Agro-wastes from coconut wood and jambolan wood processing were also analyzed to give a complete analysis of the most significant sources of agro-waste in the province. The macromolecular composition (carbohydrates, lipids and proteins) was determined and used to calculate the theoretical maximum biochemical methane potential (BMP). The results show that cassava fiber and cassava peel, which are considered to be waste, are viable resources for biomethane production. Further, the results show that cassava fiber and cassava peel have a higher biomethane potential compared with sawdust, and are therefore more suitable for biomethane production. A study to investigate the effect of toxic cyanogenic glycosides and lignin on cassava peels, using pre-treatment techniques to enhance biogas yield, should be carried out. An estimate of how much electricity can be generated based on the availability of agro-waste (cassava residues) and the amount of biomethane produced in our laboratory experiment was carried out. The amount of electricity that can be produced is enough to provide a valuable contribution to the production process in small and medium sized enterprises (SMEs) and in the cassava industry, or some other use in the rural setting.