Bio-digester is a vessel or tank which is used for bio-degradation of human faecal matter using Anaerobic Microbial Inoculum (AMI). In essence Bio-digester provides environment for AMI to work on faecal matter in an anaerobic environment. During the Bio-degradation of the faecal matter, CO2, Methane and water are generated along with very little sludge. These digesters come in different sizes and types depending on the environment of installation. Dfferent kinds of bio-digesters are being used in trains, extreme cold climate like Laddakh and Siachen and in high water table areas. Depending on the number of users, the capacity of the bio-digester ranges from 500 ltr to 20,000 ltrs or higher.