Potential for domestic biogas as household energy supply in South Africa

Biogas is a clean and renewable form of energy accessible to low-income households through anaerobic digestion of readily available organic waste. The objectives of this desktop study were to investigate the feasibility of biogas use for substitution of presently used solid fuels in rural and peri-urban households, the subsequent health co-benefits, and the constraints to adoption of domestic biogas technology in South Africa. The energy demand of low-income South African households for cooking with fuelwood was found to be 27 MJ/day and the total energy demand 68 MJ/day. This is equivalent to 2 500 L/day/household of biogas for cooking and 6 250 L/day/household of biogas for complete substitution of conventional domestic fuels. Complete substitution of fuelwood used for cooking and household fuelwood use with biogas can result in the avoidance of 43% and 85.4% respectively of total disability adjusted life-years lost (702 790) and mortalities (22 365) from indoor smoke as a consequence of solid fuel use. Approximately 625 000 households in South Africa can potentially benefit from bio-digester fed with cattle and pig waste, on the basis of livestock numbers. It is infeasible to operate a domestic bio-digester fed solely with human waste, chicken waste and food waste because of insufficient feedstock. Non-sewerec households with access to on- and off-site wate supply generate sufficient greywater for feeding a domestic bio-digester for cooking purposes. This is therefore, recommended over the use of drinking water.