Classification of biogasplants Biogas plants are mainly classified as: • continuous and batch type (as per process) • The dome and drum types • Different variations in the drum type • Continuous digester plant process is of two types (a) single stage process (b) double stage process .Continuous type biogas plant • In this plant the supply of gas is continuous and the digester is fed with biomass regularly. Single stage process •The entire process of conversion of complex organic compounds into biogas is completed in a single chamber • This chamber is regularly fed with raw materials while the spent residue keeps moving out . . • in this we get serious problems with agricultural residues when fermentated in a single stage continuously . Double stage process In this stage acidogenic stage and methogenic stage are physically separated into two chambers. The first stage of acid production is carried out in a separate chamber and only the diluted acids are fed into the second chamber where bio methanation takes place And the biogas can be collected from the second chamber. . • The feeding is between intervals . .Batch type biogas plant • Batch type plants are appropriate where daily supplies of raw waste materials are difficult to be obtained.the plant is emptied once in the process of digestion is complete. • A batch loaded digester is filled to a capacity sealed and given sufficient retentation time in the digester. .• Gas production is uneven because bacterial digestion starts slowly. peaks and then tappers off with growing consumption of volatile solids • This difficulty can overcome by using minimum two digesters so that at least one is always in operation . • This plant needs additional fermented slurry to start the digestion process. . • Batch plants are good for long fibrous materials.Mains features of batch type plant • Gas production in batch type is intermittent depending upon the clearing of the digester. • It needs several digesters or chambers for continuous gas production .these are fed alternately. (1) Floating gas holder digester (2) fixed dome digester .Dome and drum type plants • As there are many types of biogas plants mainly two types of plants are usually used they are ……. Floating gas holder digester . Fixed dome digester . • In fixed dome digester .• The floating gas holder which is used in India is known as KVIC plant .in floating gas holder the gas holder is separated from the digester . • The fixed dome digester is called Chinese plant. • They can be constructed above or underneath the ground . . the gas holder and the digester are combined. Different variations in drum type • There are two main variations in floating drum design….. . (2) floating drum without water seal. (1) floating drum with water seal. Floating drum type biogas plants . Fixed dome plant . the danger of mixing oxygen with the gas to form an explosive mixture is minimized • No problem of gas leakage • Constant gas pressure .Advantages of floating drum plant • it has less scum troubles because solids are constantly submerged • no separate pressure equalizing device needed when fresh waste is added to the tank • In it. • No maintenance.Advantages of fixed dome type plant • It has low coast compared to floating drum because it uses cement but not steel • In this type heat insulation is better as construction is beneath the ground. .