Biogas

Definition of Biogas

Generally biogas refers to a gas, which is produced by the biological breakdown of organic matter in the absence of oxygen.

Methanogenic bacteria breakdown biogenic material in the absence of oxygen to produce methane as one of the major constituent of biogas, which is used as biofuel.

Constituents of biogas

Methane, Carbon dioxide, Hydrogen sulphide, Ammonia, Nitrogen, Water vapour, Siloxanes. Carbon dioxide concentration can constitute from 25 to 50% of the biogas produced. This may depend on various factors involved in the process. Carbon dioxide being soluble in water can be removed to give pure methane. Other gases are present in minute quantities and are called impurities.

Source of Methanogenic bacteria

The most common and well known source of methanogenic bacteria harbour in the rumen of cattle. The cowdung is thus used as a source of methanogenic bacteria.

Substrate for biogas production

Cowdung, human and animal waste was initially used as substrates for biogas. However, in order to get a better yield for household purposes high carbohydrate food material such as flour (rice, wheat, maida, etc.) are also being used. Presently, Kitchen wastes for a single house hold, whereas, municipal waste is found to be a good source as substrate to produce biogas.

Plant setup

For the municipal waste, the infrastructure set up would need –

  1. Screening platform – the place where the solid waste is screened to separate metal, glass, plastic, bones, shells, etc.
  2. Grinder-to make the biodegradable waste into a pulp.
  3. Predigestor-helps to primarily store the solid waste and secondly to allow initial phases of digestion.
  4. Anaerobic chamber-is the actual gas chamber where the gas is produced.
  5. Gas collecting chamber-the gas produced from the anaerobic chamber is temporarily stored in this chamber.
  6. Scrubber-makes the biogas free of contaminant gases.
  7. Storage chamber
  8. The size of the setup can range from 2-3 kgs per day upto 5 metric tons per day.

Wastes form biogas plant

The sludge that is produced form the biogas is non-odouress, composted black sludge which can be sun dried and used as soil enricher in gardens.

Bacterial pathogens

Most of the bacterial pathogens are reported to get eliminated within a week of inoculation. Hence, the process is medically safe.

Uses of biogas

Biogas is presently being used in various areas. The most common includes cooking, generation of electricity, use of compressed methane as vehicular fuel and water heating.