At Cali, Colombia, a biodigester is an airtight container in which feces and wastewater are fermented by bacterias under anaerobic conditions. As a result of this process a gas with 66% of methane and 33% of carbon dioxide is obtained. The biodigester that is continually being reasearched and promoted is a polyethylene tube which is easy to install and has a low cost. In the biodigester wastes are reduced from 60 to 80% without loosing the availability of nutrients. The main advantages of the biodigester are: 1) Generation of energy (methane) from wastes, 2) Low cost, 3) Good quality of the effluent as fertilizer and 4) It is easy to install and to operate.