As a major disadvantage, their gas-output is not steady. Continuous plants are fed and emptied continuously. They empty automatically through the overflow whenever new material is filled in. Therefore, the substrate must be fluid and homogeneous. Continuous plants are suitable for rural households as the necessary work fits well into the daily routine.
Gas production is constant, and higher than in batch plants.
Today, nearly all biogas plants are operating on a continuous mode. If straw and dung are to be digested together, a biogas plant can be operated on a semi-batch basis. The slowly digested straw-type material is fed in about twice a year as a batch load. The dung is added and removed regularly. In developing countries, the selection of appropriate design is determined largely by the prevailing design in the region.