Biology · Microbes in Human Welfare · NEET
A biogas plant has a concrete tank (10-15 feet deep) where bio-wastes are collected and a slurry of cattle dung is fed. Over this slurry sits a floating cover that moves up as gas is produced. The plant also has an inlet to add fresh slurry and a gas outlet fitted with a valve to draw the biogas for use. Used slurry leaves through an outlet and is used as fertiliser.
Methanogens produce the biogas. These are bacteria (a common one is Methanobacterium) that grow anaerobically on cellulose-rich material and release methane along with CO2 and H2. They are abundant in cattle dung (gobar) because they live in the rumen of cattle, so the dung fed into the plant already carries them.
As methanogens digest the slurry, gas collects at the top of the tank. The floating cover rises with the gas, so its height shows how much gas has built up and it keeps the gas trapped. The gas is then taken out through an outlet with a valve, and pipes carry it to nearby houses for cooking and lighting.
It is anaerobic. Methanogens grow without oxygen on cellulosic material. This is a common NEET trap: if a statement says methanogens grow aerobically, it is wrong. The absence of oxygen is exactly why methane (a reduced gas) is formed instead of only CO2.
The spent (used) slurry is removed through an outlet and used as fertiliser (manure) in fields. So a biogas plant does two useful jobs at once: it gives clean fuel and it recycles the waste into nutrient-rich manure, which is why it suits rural areas with plenty of cattle dung.
The primitive prokaryotes responsible for the production of biogas from the dung of ruminant animals, include the:
Which of the following statements about methanogens is not correct?
Try the real previous-year questions from this chapter — each with the answer and a full solution.
The concrete tank in a biogas plant is about 10-15 feet deep. Bio-wastes are collected in it and a slurry of cattle dung is fed for the methanogens to digest.
Biogas is a mixture of gases with methane predominating, along with CO2 and H2. Methane is the fuel component, which is why biogas burns and is used for cooking and lighting.
Cattle dung, the raw material, is available in large amounts in rural areas where cattle are kept. So it is convenient and cheap to build biogas plants there and use the gas locally.
Biogas technology in India was developed mainly through the efforts of the Indian Agricultural Research Institute (IARI) and the Khadi and Village Industries Commission (KVIC).
After the gas is taken out, the spent slurry is removed through an outlet and used as fertiliser in fields, so the plant recycles waste into manure while also giving fuel.
