Question

Name the major constituents of biogas. Write the properties of biogas which make it a good fuel.

Answer 1

Biogas is similar to natural gas and is produced as a by-product from the biological breakdown of organic materials.

Complete answer
Biogas is a methane rich fuel gas produced by anaerobic breakdown or digestion of biomass with the help of methanogenic bacteria. Biogas consists of methane, carbon dioxide, and traces of other compounds such as hydrogen sulphide, ammonia and water vapours.
Biogas composition:

| Matter| Percentage
---|---|---
1.| Methane| 5-75%
2.| Carbon dioxide| 25-45%
3.| Nitrogen| 0-0.3%
4.| Hydrogen| 1-5%
5.| Hydrogen sulphide| 0-3%
6.| Oxygen| 0.1-0.5%

Properties of Biogas:
Biogas technology provides an alternative source of energy in rural India. It is considered as a basic model that provides appropriate technology for fulfilling the need for cooking fuel in rural areas.
Biogas is derived from the local resources such as cattle waste and other organic wastes, energy and manure. These waste materials are used for Biogas production.
Depending on places from where it is produced, biogas are also called swamp gas, marsh gas, landfill gas, digester gas, etc.
The amount and composition of biogas varies with the type of waste material used. The common sources include manure, sewage, sludge, cattle dung, municipal solid waste, biodegradable waste and any other biodegradable feed stock. Some weeds have also been very useful. Eg. Banana peels, Mirabilis , Cauliflower wastes, etc.
Biogas plant, also called a digester , is used for fermentation of waste materials. Generally, it is a 10-15 feet deep pit where waste material is filled.
On a commercial scale, where large digesters are used, the slurry is heated to 35°C or even higher depending upon the digester. Now, the anaerobic bacteria multiply and break down complex volatile solids, and are found in the manure. The biogas are produced as a by-product.
Biogas are a very important source of energy. The methane in biogas burns more cleanly than coal and produces more energy with less emission than carbon dioxide.
Biogas is also useful in water heaters, furnaces, compressor engines such as those of refrigerators and air conditioners, production of electricity.

Note:
For biogas production, the technology has been developed in our country by Indian Agricultural Research Institute (IARI) and Khadi and Village Industries Commission (KVIC).
The manure, especially cattle/dung, is rich in bacteria.
Slurry is a component of solid mixture especially of fine particles of cement, manure, etc.