The gas or energy obtained as a result of the breakdown of organic matter is called biogas. As the name implies, bio is related to living beings and gas is the state of matter which is emitted on decomposition.
So, when you look for biogas meaning, note that you are aware that this is a form of energy that can be obtained naturally. Similar to other resources such as air, water, etc., biogas is also a significant source of energy.
All you have to do is trap this energy for utilisation in the desired areas. Therefore, students while studying this chapter need to be cautious about multiple aspects of biogas. Starting from how it is obtained to its advantages and disadvantages, along with its application in real life - everything is explained in detail below.
Biomass and Bioenergy
Biogas or bioenergy is obtained from biomass which consists of decaying animal waste, crop residues, household solid waste, food waste, agricultural waste, and other similar by-products. The gas emitted on the decomposition of such matter is what is meant by biogas.
Look at the diagram below for your reference.
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The image above shows the complete step by step process of the formation of biogas.
This obtained biogas contain gases like methane, carbon dioxide, small amounts of hydrogen, oxygen, nitrogen, etc. Besides, it also contains tiny portions of heavy metals, alkaline earth metals, and even alkali metals.
What are the Advantages of Biogas?
Although biogas seems to be useful in all dimensions, it might be hard to believe there are both advantages and disadvantages of biogas. Here is a list of both the features for your understanding.
Advantages offered by Biogas are as Follows -
It is environmentally friendly and does not contribute to pollution.
A renewable source of energy since waste production is constant.
Reduces land fillings significantly by decomposing them.
A cost-effective option of getting access to a significant amount of energy.
Establishment of a biogas plant leads to employment of innumerable people.
The Disadvantages of Biogas are Listed as Follows -
Traces of impurities remain even after multiple layers of purification.
Cannot be utilised or tapped for large scale production.
Presence of methane and oxygen make it hazardous and prone to explosion and inflammation.
Therefore, the above list of advantages and disadvantages of biogas plants or biogas as a source of energy provides a detailed explanation why this is an important topic. While students must know about both the advantages and disadvantages of biogas plants, they should also have a clear idea of its origin.
Biogas and Biogas Plant
The biogas plants are more like a miniature version of massive power generating plants that we generally see. There is a round-shaped dome-like structure which has an inlet to let in the organic wastes. These wastes are the primary sources of energy for a biogas plant, as already mentioned in biogas meaning.
Refer to the picture below, which shows a real-life biogas plant.
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The plant shown in this above picture is a comparatively smaller unit than conventional power plants. This is one of the major limitations of biogas plants which has restricted its universal use as a major contributor to energy creation.
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FAQs on Biogas Energy
1. What is biogas energy and how is it produced?
Biogas is a renewable fuel produced from the anaerobic decomposition (breakdown without oxygen) of organic matter. The primary components of biogas are methane (CH₄), which is flammable, and carbon dioxide (CO₂). It is produced in a special container called a digester where microbes break down raw materials like animal dung, agricultural waste, sewage, and food scraps to release the gas.
2. What are the main components and working principle of a fixed-dome type biogas plant?
A fixed-dome biogas plant, common in rural areas, consists of a few key parts:
- Mixing Tank: Where organic waste (like cow dung) is mixed with water to form a slurry.
- Inlet Pipe: Carries the slurry into the digester.
- Digester Tank: An underground, sealed chamber where anaerobic bacteria decompose the slurry over several weeks.
- Gas Holder (Dome): A fixed, dome-shaped roof on the digester where the produced biogas collects and builds pressure.
- Outlet Pipe: A pipe connected to the dome that supplies the gas for use in kitchens or for lighting.
- Overflow Tank: Where the spent slurry is discharged, which can then be used as a rich organic fertilizer.
3. What are the common examples and uses of biogas energy?
Biogas is a versatile energy source with several important applications. Common uses include:
- Cooking Fuel: It is supplied directly to household kitchens as a clean and efficient fuel for cooking, replacing firewood or LPG.
- Lighting: It can be used to power gas lamps for lighting in homes and on farms.
- Electricity Generation: On a larger scale, biogas can be used to run engines that turn turbines, generating electricity for a community or facility.
- Mechanical Power: Biogas can fuel engines for running water pumps for irrigation on farms.
4. What are the key benefits of using biogas as an energy source?
The importance of biogas lies in its numerous environmental and economic benefits. It is a clean fuel that burns without smoke, reducing indoor air pollution. It provides a sustainable way to manage organic waste, preventing it from releasing methane (a potent greenhouse gas) into the atmosphere. The byproduct, a nutrient-rich slurry, serves as an excellent organic fertilizer, improving soil health and reducing the need for chemical fertilizers. This makes it a cost-effective and eco-friendly energy solution.
5. Why is anaerobic digestion essential for producing biogas, as opposed to aerobic decomposition?
Anaerobic digestion (without oxygen) is critical because it involves specific microbes called methanogens. These microorganisms thrive in oxygen-free environments and are responsible for converting organic acids into methane gas (CH₄), the primary combustible component of biogas. In contrast, aerobic decomposition (with oxygen) would involve different microbes that break down waste into carbon dioxide, water, and heat, but would not produce the flammable methane needed for fuel.
6. How does the type of raw material affect the quality of biogas produced?
The quality and yield of biogas are highly dependent on the composition of the raw materials, specifically the Carbon-to-Nitrogen (C/N) ratio. For example, cow dung has an ideal C/N ratio and contains the necessary microbes, making it an excellent feedstock. Agricultural waste like straw is high in carbon but low in nitrogen, so it decomposes slowly. To optimise production, different materials are often mixed to achieve a balanced C/N ratio, ensuring the microbes have the right nutrients to efficiently produce methane.
7. What is the scientific difference between biogas and natural gas?
While both are gaseous fuels, their composition and origin differ significantly. Biogas is a mixture of gases, primarily consisting of 50-75% methane (CH₄) and 25-50% carbon dioxide (CO₂), along with traces of other gases. It is produced through biological processes. Natural gas, a fossil fuel, is almost pure methane (typically over 90% CH₄). Due to its higher methane concentration, natural gas has a higher calorific value (produces more energy when burned) than biogas.
8. What happens to the slurry left over from a biogas plant? Is it considered waste?
The slurry leftover from a biogas plant is not waste; it is a valuable co-product. During digestion, the organic matter is broken down, but the essential nutrients like nitrogen and phosphorus remain in the slurry. This makes it a high-quality, nutrient-rich organic fertilizer that is superior to raw manure. Using this slurry improves soil fertility and structure, completing a sustainable cycle where waste is converted into both energy and agricultural resources.
