Bio Gas Plant

The biogas plant consists of two components: a digester (or fermentation tank) and a gas holder. The digester is a cube-shaped or cylindrical waterproof container with an inlet into which the fermentable mixture is introduced in the form of a liquid slurry. The gas holder is normally an airproof steel container that, by floating like a ball on the fermentation mix, cuts off air to the digester (anaerobiosis) and collects the gas generated. In one of the most widely used designs, the gas holder is equipped with a gas outlet, while the digester is provided with an overflow pipe to lead the sludge out into a drainage pit.

Table 1
S.N. Size of Plant Daily Fresh Dung (Kg) Daily Water Liters Approx. No. Cattle Required
1 4 24 24 2-3
2 6 36 36 3-4
3. 8 48 48 4 – 6
4. 10 60 60 6 – 9
5. 15 90 90 9 – 14
6. 20 120 120 14 and more
* Plant size is the sum of digester volume and gas storage ** Based on a hydraulic retention time of 70 days

A biogas plant consists of five main structure or components. The required quantity of dung and water is mixed in the inlet tank and this mix in the form of slurry is allowed to be digested inside the digester. The gas produced in the digester is collected in the dome, called as the gasholder. The digested slurry flows to the outlet tank from the dig through the manhole. The slurry then flows through overflow opening to the compost pit where it is collected and composted. The gas is supplied to the point of application through the pipeline. Before deciding the size of plant, it is necessary to collect dung for several days to determine what is the average daily dung production. The amount of dung daily available daily, a 8 m3 plant has to be selected. It should be kept in mind that at least six kg dung is required for 1 m3 of plant capacity.