8.4. Microbes in Production of Biogas

Biogas is a mixture of gases (containing predominantly methane) produced by the microbial activity and which may be used as fuel. You have learnt that microbes produce different types of gaseous end-products during growth and metabolism. The type of the gas produced depends upon the microbes and the organic substrates they utilise.

Biogas is primarily composed of methane and is generated through the metabolic processes of certain microbes. Microbes convert organic materials into gas depending on the type of substrate they utilize. This means the kind of food or waste the microbes consume can influence the gases produced. For example, using plant materials will typically produce different gases than using animal waste.

Think of biogas like cooking food on a stove. Just as using different ingredients can change the flavor of your dish, different substrates (like food scraps or animal dung) can influence the types of gas produced by microbes.

Certain bacteria, which grow anaerobically on cellulosic material, produce large amounts of methane along with CO2 and H2. These bacteria are collectively called methanogens, and one such common bacterium is Methanobacterium. These bacteria are commonly found in the anaerobic sludge during sewage treatment. These bacteria are also present in the rumen (a part of stomach) of cattle.

Methanogens are a group of bacteria that thrive in environments without oxygen. They break down organic materials, particularly those high in cellulose, like plant matter, and produce methane as a byproduct. Methanobacterium is one type of methanogen that can be found in places like sewage treatment facilities and the stomach of cows, where they help digest food and produce methane.

Imagine a compost pile in your backyard. While decomposing leaves and food scraps, certain microorganisms break down this organic matter and produce gases. Similarly, methanogens in cattle help digest grass, producing methane that the farmers may later harness as biogas.

The excreta (dung) of cattle, commonly called gobar, is rich in these bacteria. Dung can be used for generation of biogas, commonly called gobar gas.

Cattle dung is a valuable resource because it contains many methanogens crucial for biogas production. When dung is digested in a biogas plant, these microorganisms break down the material and produce biogas, which can be used as an energy source for cooking or lighting fires.

Using cow dung for biogas production is like utilizing leftover food for composting. Just as leftover food breaks down into rich soil for planting and returning nutrients to the earth, cow dung can be broken down by microbes to produce energy in the form of biogas.

The biogas plant consists of a concrete tank (10-15 feet deep) in which bio-wastes are collected and a slurry of dung is fed. A floating cover is placed over the slurry, which keeps on rising as the gas is produced in the tank due to the microbial activity.

In a biogas plant, organic waste and animal dung are mixed in a large concrete tank. As microbes break down this material, they release biogas, which causes a floating cover over the tank to rise. The gas produced can be collected and used for various purposes, ensuring efficient resource utilization.

Think of the biogas plant like a balloon. As you blow air into the balloon, it expands because of the air pumped inside. Similarly, as microbes produce gas from the waste, the gas collects under the floating cover, causing it to rise like the expanding balloon.

The spent slurry is removed through another outlet and may be used as fertiliser. Cattle dung is available in large quantities in rural areas where cattle are used for a variety of purposes.

After gas production, the remaining slurry from the biogas plant can be used as a nutrient-rich fertilizer for crops. This creates a sustainable cycle where waste is converted into energy, and byproducts can enhance soil fertility, benefiting agricultural practices.

Using biogas slurry as fertilizer is like using eggshells for compost. Just as you can enhance your garden soil with recycled eggshells, farmers can enrich their fields with biogas slurry, benefiting both the land and the waste utilized.

So biogas plants are more often built in rural areas. The biogas thus produced is used for cooking and lighting.

In rural areas, where access to electricity and fuel can be limited, biogas plants provide a sustainable energy source. The methane produced can be captured and used directly for cooking or lighting, reducing dependence on conventional fuels.

Imagine a rural household using biogas instead of wood or kerosene. Just like how some people use solar panels for energy in areas without regular electricity, biogas plants offer rural communities a reliable and eco-friendly alternative for daily energy needs.

The technology of biogas production was developed in India mainly due to the efforts of Indian Agricultural Research Institute (IARI) and Khadi and Village Industries Commission (KVIC).

In India, the development of biogas technology has been significantly influenced by research organizations and government initiatives aimed at promoting sustainable energy sources. These efforts have enabled local communities to adopt biogas systems and utilize resources efficiently.

Consider how innovations in solar energy technologies have helped rural communities gain access to electricity. Similarly, the development of biogas technology empowers villagers to harness their waste for energy and improve their quality of life.

If your school is situated in a village or near a village, it would be very interesting to enquire if there are any biogas plants nearby. Visit the biogas plant and learn more about it from the people who are actually managing it.

Visiting a local biogas plant can provide hands-on experience and deeper understanding of how biogas production works. Engaging with the operators will enable students to see the technology in action and grasp its real-world applications.

Just like field trips to solar farms can enlighten students about renewable energy, exploring a biogas plant creates an opportunity for immersive learning, showcasing how local waste is transformed into sustainable energy.

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