The Indian Appropriate Rural Technology Institute (ARTI) has developed a small biogas digester that uses starchy or sugary wastes as feedstock, including waste flour, vegetable residues, waste food, fruit peelings, rotten fruit, oil cake, rhizomes of banana, canna (a plant similar to a lily but rich in starch), and non-edible seeds.
These household digesters have a small footprint and are made from cut-down high-density polythene (HDPE) water tanks. A heat gun can be used to make them and standard HDPE fittings can be used. The standard ARTI biogas plant uses two tanks, with volumes of typically around 0.75 to 1 m3. The smaller tank on top is the gas holder and is inverted over the larger fermenter so it telescopes inside. It is the fermenter which holds the mixture of decomposing feedstock and water. The white tube you see in the picture above is the inlet, where the feedstock is added. The Grey pipe on the left hand side is the overflow.
This technology offers a solution not just for domestic waste disposal, but also for collective disposal of community waste. In villages, food waste was traditionally fed to animals or left by the side of the road for animals to devour. People continue to do this in cities but there are fewer animals to consume it. The result is that smelly, rotting food attracts flies and rats. Some authorities collect food waste and dispose of it in landfill.