A biodigester is a large dome-shaped tank (usually built underground) that is fed by human and animal manure. Possible sources of manure are toilets and stables (equipped with a pipe that feeds the digester). As the manure decomposes in the biodigester methane gas is released and accumulates at the top of the dome. By means of a gas-pipe that is attached at the very top this gas can be redirected to the kitchen to fuel gas stoves. As the digester tank fills up, older manure that has already released its gas flows into a second chamber – there it is either fully decomposed with the help of worms, or allowed to overflow into a designated “pond” or lagoon where heavy feeding plants and bacteria absorb the remains.