Index >> Waste Water Microbiology >>Biogas

Biogas - Biogas is mixture of methane (50-60 per cent), CO2 (30-40 per cent), Hydrogen (5-10 per cent), H2S and nitrogen (traces), produced from the anaerobic digestion of animal, plant wastes or any cellulose containing waste material. The digester used for biogas production is called a Biogas plant.

A typical biogas plant using cow ­ dung as raw material consists of (a) digester and (b) gas holder. The digesters are either of batch type which are filled once, sealed and emptied when the raw materials stop producing gas or (b) continuous type, which are fed with a definite quantity of wastes at regular intervals so that gas production is continuous and regular. The nature of fermentation in the digester is anaerobic.

The first three groups of bacteria include facultative as well as strict anaerobes like Cellulomonas. Clostridium, Bacililus, Bacteroides, Ruminococcus, Eubacterium etc. while the methanogenic bacteria include Methanosarcina, Methanothrix. Methanobacterium and Meth­anospirillum.

The methanogenic phase is strict anaerobic and during this phase organic carbon is converted into micr9bial mass, CO2 and methane. These bacteria are sensitive to pH and the optimal pH for methane production is 6.8-7.2. If pH drops to 6.6 or below there is an inibition of methanogenesis.