Various designs of low cost digesters have been developed and often the biogas storage tank is combined with the digester. An example of such a digester is the 'gobar gas plant' designed to produce biogas from cowdung. The gobar gas plant consists of an underground circular pit lined with cemented brick wall, which serves as the digester.

The pit is covered with an inverted and vertically movable metal tank (closed on top, open on the bottom), which serves as biogas storage tank. A tank is made from bricks on a raised platform above the ground; this serves as cowdung mixing tank to feed the digester through an inlet pipe that delivers the cowdung slurry near the bottom of the digester.

The spent cowdung slurry is removed to a drying bed (using sun energy for drying) and is ultimately used as a manure. The gas flows out through an outlet pipe, which has a provision of drainage of the excess moisture.