What Are the Main Steps and Advantages of Biogas Production?
We have become so advanced in technology that we are able to use the organic waste and produce a gas that can be used by the people living in that society, thus saving on the increased exploitation of the natural resources. Biogas energy is one such example of innovations. There are certain bacteria that are known to grow under anaerobic conditions, and they produce a lot of methane, carbon dioxide, and hydrogen. And this mixture of gases can be used for a variety of chores. Methanogens are the bacteria that produce the gaseous mixture. One such methanogen is Methanobacterium, which is present in the cattle food. The cattle digest these bacteria with the food, and the dung produced by the cattle contain these methanogens that are used in the production of gobar gas.
A mixture of gases that are produced by the anaerobic decomposition of the organic matter like municipal waste, plant residue, agricultural waste, food waste, etc. is called biogas. Biogas is usually composed of carbon dioxide, methane, and a small amount of hydrogen sulphide and moisture.
Biogas Plant
It is a dome-like structure in which the production of the biogas takes place. The biogas plant has a source to supply the feedstock, a digestion tank to produce biogas, a biogas recovery unit to separate the biogas that is produced and the heat exchanger to maintain the temperature of the digester that is required for the production of the biogas. The digester is a sealed chamber in which the biowaste and the slurry are decomposed using anaerobic decomposition. The slurry is then covered with a floating cover so that the gas produced due to microbial activity can make the cover rise upwards. The biogas thus produced is drawn out through the pipes and then supplied to the respective places through the connected pipes. This slurry is removed through an outlet and then later used as a fertilizer. This biogas can be used for cooking or lighting.
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Biogas Production in Landfill
Besides the gobar gas plant, biogas can also be produced in the Landfills. The organic matter present in the landfills decomposes naturally, and the biogas is produced as a result of the activity of these microbes. Methanobacteria that are present in the organic waste decompose the waste and produce a mixture of gases called biogas. There is a network of interconnected pipes present in the landfill to collect the biogas that is produced—the composition of the gas changes with time. After a year of production, the composition of methane and carbon dioxide changes to 60% and 40%, respectively. This is gaining popularity and acceptance as this method prevents the explosion that could be caused due to the collection of methane gas in the landfill, and it also prevents the loss of methane into the atmosphere. The biogas produced in landfills is used to create electricity.
Substrates Required in Biogas Production
Advantages of Biogas
The advantages of the biogas are: -
Renewable Source of Energy: Biogas is a renewable source of energy because the production of the biogas is dependent on the generation of the waste, which is an endless process.
Cheaper Technology: The installation of the biogas requires a very small cost, and it becomes self-sufficient in a duration of about 3-4 months.
Non - Polluting: The biogas burns without smoke, and thus no harmful gases like carbon dioxide, carbon monoxide, sulphur dioxide, and nitrous oxide are released.
Generates Employment: The setup of biogas creates a work opportunity for thousands of people in rural areas.
Reduces Landfills: The slurry that is leftover after the production of biogas is used as a fertilizer. The method of disposal is safe and environmentally friendly, and so no space is wasted in the form of landfills.
Disadvantages of Biogas
The disadvantages of biogas are:
Contains Impurities: The biogas contains several impurities which are difficult to remove even after a number of rounds of purification. Biogas, when compressed to be used as fuel, proves to be highly corrosive to the container.
Unstable and Hazardous: When methane comes in contact with oxygen, it reacts to produce carbon dioxide. The highly inflammable nature of the methane makes it prone to explosions.
Not Efficient on a Large Scale: Since it is not easy to enhance the efficiency of biogas, it is not viable economically to use biogas on a huge scale.
FAQs on Production of Biogas Explained: Key Steps & Benefits
1. What is biogas and what is its primary composition?
Biogas is a renewable fuel gas produced by the anaerobic digestion or fermentation of organic matter. It is a mixture of gases, primarily composed of methane (CH₄), which typically makes up 50-70% of the volume, and carbon dioxide (CO₂), which accounts for 30-40%. It may also contain trace amounts of hydrogen sulphide (H₂S) and water vapour.
2. What are methanogens and what is their specific role in producing biogas?
Methanogens are a group of anaerobic microorganisms (Archaea) that produce methane as a metabolic byproduct. In a biogas plant, they carry out the final stage of anaerobic digestion. After other bacteria break down complex organic matter into simpler organic acids, methanogens consume these acids and produce methane and carbon dioxide, which constitute biogas. A common example is Methanobacterium.
3. What are the key stages of biogas production through anaerobic digestion?
The production of biogas through anaerobic digestion occurs in three main biochemical stages:
- Hydrolysis: In the first stage, complex organic polymers like carbohydrates, proteins, and fats present in the biomass are broken down into simpler soluble molecules like sugars, amino acids, and fatty acids by hydrolytic enzymes secreted by bacteria.
- Acidogenesis (or Fermentation): Acid-forming bacteria further break down the simple molecules into volatile fatty acids (like acetic acid), along with ammonia, carbon dioxide, and hydrogen sulphide.
- Methanogenesis: In the final stage, methanogenic bacteria act on the intermediate products from the acidogenesis stage. They convert acetic acid and hydrogen into methane (CH₄) and carbon dioxide (CO₂).
4. Why is cattle dung (gobar) considered an excellent substrate for biogas production?
Cattle dung is considered an excellent substrate for biogas production because it is rich in cellulose and contains a high concentration of methanogens. These microorganisms are naturally present in the rumen of cattle, where they help digest cellulose. Consequently, when the cattle excrete dung, it is already inoculated with the necessary bacteria to start and sustain the methanogenesis process efficiently in a biogas plant.
5. How does a typical floating-dome biogas plant operate?
A typical biogas plant consists of a large underground digestion tank made of concrete. A mixture of water and organic waste, called slurry, is fed into the digester through an inlet pipe. As microbes anaerobically break down the slurry, biogas is produced. This gas gets trapped and accumulates under a floating metal dome, causing it to rise. The gas is then drawn out through an outlet pipe for use in cooking or lighting. The digested slurry is removed through another outlet and can be used as a nutrient-rich organic fertiliser.
6. What are the main advantages of using biogas as an energy source?
Biogas offers several key advantages:
- Renewable Source: It is produced from organic waste, which is continuously available.
- Eco-Friendly: It burns cleanly without smoke, reducing air pollution compared to burning firewood or dung cakes.
- Waste Management: It provides an effective way to dispose of and recycle organic waste from agriculture and households.
- Nutrient-Rich Fertiliser: The leftover slurry is an excellent, nutrient-rich manure that improves soil fertility.
- Reduces Deforestation: It provides an alternative to firewood, thus helping to conserve forests.
7. How is the spent slurry from a biogas plant more beneficial than raw animal manure?
The spent slurry from a biogas plant is more beneficial than raw manure because the anaerobic digestion process converts complex organic compounds into a more stabilised, nutrient-rich form. The nitrogen and phosphorus are more readily available for plants to absorb. Furthermore, the process destroys most pathogens and weed seeds present in the raw manure, making it a safer and more effective organic fertiliser for agricultural use.
