ARTI biogas digester using waste foodstuffs
There are many people of course who don’t have livestock or who live in an urban environment where the two conventional systems discussed above are not appropriate and cannot be utilised. If you live in a built up area, the ARTI biogas system is for you!
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 and the household needs a space that is about 2m square and 2.5 m high. 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.
For best results the feedstock (stuff you put in the fermenter) should be blended so that it is smooth. The starter mix can be cattle dung blended in water or some waste flour. The feeding of the ARTI biogas plant is built up over a few weeks until it provides a steady supply of gas. This is typically 250-500 g of gas per day from 1-2 kg (dry matter) of feed. An inlet is provided for adding feedstock, and an overflow for removing the digested residue. The ARTI biogas digester should be set up in a sunny place close to the kitchen, so a short section of pipe can take the biogas to the kitchen.