Student develops a biogas digester
Ann Lenhart, an American Fullbright exchange engineering student at the University of Namibia’s Ongwediva campus developed a biogas digester. The school is currently experiencing a shortage of fuel because of the scarcity of wood therefore the digester will help the school to implement its feeding programe by creating an alternative energy supply as opposed to using wood.
Anna, who previously worked on a biogas project in Uganda in 2007, arrived in the country in October 2011 with the intention of exploring biogas as a solution to municipal waste and eventually ended at Enguwantale.
“Grant Copenhaver, a United States Peace Corps Volunteer was introduced to me through mutual friends, when he heard about my research he suggested that biogas technology could be a solution to the fuel shortage that threatens the school feeding program where he volunteers,” said Anna. Grant then submitted the proposal to the United States Peace Corps to open up the project for donations. He also oversaw the school community’s involvement in the project, to which Anna was the engineer and onsite project manager. Two lecturers from UNAM’s Ongwediva campus civil engineering department, Prof. Lother Hafner and Dr. Iyambo Ipinge acted as consultants on the project.
The digester is used by mixing cow dung with water into a slurry which is then added to the digester through an inlet pipe. In the digester, the bacteria is starved of oxygen and undergoes anaerobic digestion which produces biogas, which can then be used for cooking. An anaerobic condition is created and micro-organisms produce biogas which is composed of approximately 60% methane. According to Ann, the design used is of a GGC-2047 biogas plant that operates semi-continuously and is commonly used in developing countries. This design was chosen on the basis of builder experience and availability of local materials. The design includes an inlet tank, outlet tank, compost tank, digester and dome. The walls of all the components are constructed from bricks and lined with cement while the dome is constructed from concrete.
The digester was built in the school premises for the gas to be used to cook corn meal and porridge for the learner’s lunch. The digester consumes about 400ml of compost a week and because the school is located in a rural area with substantial cattle population, cow manure is readily available and will result in less trees being cut down. According to Ann, once the slurry is digested, it exits through an outlet tank and can be used as a fertilizer, which has a higher concentration of Phosphorous, Potassium and Nitrogen than undigested cow manure. The compost produced by the plant is considered to be better for long-term improvement of the soil than commercially produced fertilisers which are costly.
Construction on the digester started on 6 June 2012 and was completed on 30 June 2012.
The plant costs about N$16 000 to build with funds raised from the Fullbright student grant program and donations collected through the US Peace Corps. The digester at Enguwantale will be in operation from early August and will serve as a pilot programe and if successful, the digester will have potential to alleviate some of the pressure on scarce wood resources in semi-arid and/arid areas. “If the digester is successfull, hopefully the ministry will fund the projects at other schools in the area,” Ann said.