Biogas production for smallholder energy needs: Experiences in Uganda

Abstract

Although the discovery of biogas dates back to the 18^th century, it was only in the early 1900s that the technology obtained some use in real life situations. In Uganda the first biogas plant was built in Mbarara district in the early 1950s. However, the first well-documented study on biogas technology was a PhD thesis by Boshoff (1970), then Lecturer at the Department of Agricultural Engineering, Makerere University. During the years that followed, world-wide threats of dwindling fossil fuel resources stimulated efforts to develop new and renewable energy resources including biogas technology. Uganda joined other countries in these efforts but drastically lost pace during years of civil strife. This paper briefly outlines developments in biogas technology with special focus on Uganda, it describes efforts NARO/AEATRI has made in the development of a floating gas-holder digester type, fixed half-dome type and a tubular digester type. The first two digester-types generate 0.20-0.25 m³ ofgas per m³ ofdigester per day at optimal production. AEATRI has also developed several designs of biogas stoves that operate at a pressure of 50-75 mm of water, consuming 0.15-0.2 m³ of gas per hr. The effluent (slurry) from AEATRI digesters has been chemically analysed for soil enhancement nutrients. The results show a significant increase in major nutrients: nitrogen - 18%, phosphorus - 24%, and potassium - 66%. The paper proposes a policy framework for integrated promotion of this technology with a view' to making its contribution more responsive to agricultural modernisation in Uganda.