In the previous article, I introduced you to the Japanese bio-toilet technology, as one of the sanitation options for mountains. This article will focus on an Indian technology that converts human waste into biogas. The biogas can be used for cooking, lighting lamps, warming bodies in winter and other purposes. A camping cooperative can use this technology to safely recycle human waste. They can use the byproducts for brightening the camps during night and whiteouts and cooking meals for the guests and the operators.
Another benefit is that the effluent of the biogas plant doubles as manure that can add vigor to the camp kitchen gardens.
This technology is called Sulabh Model of Bioenergy. The Sulabh International, the technology developer, has improved its biogas generation design, ensuring ease of implementation. The new design does not need manual handling of human waste. The design has been approved by the Ministry of Non-Conventional Energy Sources, Govt. of India.
The technology is quite simple.
1000 cubic feet biogas = 600 cubic feet natural gas
1 cubic foot biogas = 0.6 cubic feet natural gas
About 11 cubic feet (300 liters) of biogas is required for cooking one meal for one person.
A digester (a container) is constructed underground. The human waste from the toilets is directed into the digester following the gravity principles. The methanogenic bacteria, living in the sewage, stimulate anaerobic fermentation inside the digester and produce biogas. The biogas collects in the liquid displacement chamber in the digester.
The biogas consists of methane (65-66%), carbon dioxide (32-34%), and other gases. The biogas burners neither produce odor nor soot.
Each person produces enough excreta daily to generate one cubic foot biogas. So in a five-day trek, ten (10) persons can help in producing fifty (50) cubic feet biogas. The amount of biogas generated from the waste also depends on amount and type of waste and design used. The kitchen waste can also be used to generate biogas.