How biogas is produced from anaerobic digestion of organic waste
Biogas is a renewable energy source. It is produced under anaerobic conditions by breaking down organic matters such as agricultural waste, food waste and animal dung by a specific bacteria. Biogas is produced in a bio gas plant. The major components of biogas are primarily methane (CH4), hydrogen (H) and carbon dioxide (CO2). As the decomposition of these organic matters happens in an anaerobic environment, the process is also termed as anaerobic digestion. One of the major components of biogas is methane, which constitutes about 50-75% of the biogas. Thus, it is highly flammable, and produces a deep blue flame. Biogas is also used to power various types of vehicles.
Bio Gas Plant
The anaerobic digesters we have mentioned earlier are called biogas plants. In this section, we will have an introduction of a biogas plant. A working bio gas plant has about five components- an inlet, a fermentation chamber, storage, an outlet and finally one exit pipe. The inlet is a path through which the slurry is fed to the consequent chamber, where the biogas reactors are at work which is otherwise known as the fermentation chamber. In this chamber, many biogas reactors or microorganisms play the role of a chef; they break down the organic matter to produce the biogas. Then the produced gas is stored in the storage tank from where the gas is channelled through the exit pipe. The outlet is used to clear out the fermentation chamber. A biogas plant diagram looks like this -
(image will be uploaded soon)
Breakdown of Organic Waste
Organic wastes such as agricultural waste, food waste or animal dung are first processed as a liquid or as slurry, which is mixed with water, and then they are fed to the bio gas plant. Now the stages are as follows-
The polymers of the organic waste are broken down in the first step, to make it more susceptible to the acidogenic bacteria present in the next step.
In this step carbon-di-oxide, ammonia, hydrogen and other organic acids are produced as the acidogenic bacteria convert the sugar and amino acid from the broken down organic waste.
These organic acids are further converted into hydrogen, ammonia and carbon-di-oxide.
All these are ultimately converted into methane and carbon-di-oxide, by methanogens.
Methane is a highly combustible gas and can also be oxidized with oxygen. The energy produced by the combustion of these gases can be used in various ways and can be used as fuel.
(image will be uploaded soon)
The Ecology of Biogas
Biogas is one of the most environmentally friendly energy sources. It takes care of the two harmful effects of fossil-fueled energy sources. We have been relying on fossil fuels for energy sources since the dawn of modern civilization. But it won't be easy to make ends meet if we keep on welling fossil fuel as our only energy source. Along with water pollution, air pollution, fossil fuel energy sources are a curse to mankind and the environment as well. By converting organic waste which is mass-produced in every household, in a reliable energy supply, we can alleviate both harmful effects at one. On the one hand, keep the fossil fuel depletion at bay and also cleanse the environment. Biogas takes harmful gases like methane and carbon-di-oxide and converts them into a much safer form.
Solved Examples
1. What is Biogas?
Biogas is a renewable energy source. It is produced under anaerobic conditions by breaking down organic matters such as agricultural waste, food waste, and animal dung by a certain bacteria. It is also environment-friendly.
2. Fill in the blanks the main component of biogas is______?
Methane
3. Name the components of biogas.
The components of biogas are- methane, carbon-di-oxide, hydrogen, nitrogen and other gases.
Did You Know?
The major components of biogas are methane and carbon-di-oxide. A bio gas plant has five components, an inlet, a fermentation chamber, storage, an outlet and finally one exit pipe. Biogas is a renewable energy source; it is also environment - friendly. In 2016, the amount of biogas obtained from households in the UK provided for 2 million families. 36% of the renewables collected throughout the world come from biogas.
FAQs on Biogas in Biology Meaning Composition and Applications
1. What is biogas?
Biogas is a renewable gaseous fuel produced by the anaerobic decomposition of organic matter by microorganisms. It is mainly composed of:
- Methane (CH₄) – 50–70%
- Carbon dioxide (CO₂) – 30–50%
- Small amounts of hydrogen sulfide and water vapor
2. How is biogas produced?
Biogas is produced through anaerobic digestion, a biological process carried out by microorganisms without oxygen. The process occurs in four main stages:
- Hydrolysis – complex organic matter is broken into simple molecules
- Acidogenesis – simple molecules are converted into organic acids
- Acetogenesis – acids are converted into acetic acid, CO₂, and hydrogen
- Methanogenesis – methanogenic bacteria produce methane gas
3. Which microorganisms are involved in biogas production?
Biogas production involves different groups of anaerobic bacteria and methanogens. Key microorganisms include:
- Hydrolytic bacteria – break down complex polymers
- Acidogenic bacteria – produce organic acids
- Acetogenic bacteria – form acetic acid
- Methanogenic archaea – convert substrates into methane
4. What are the main components of biogas?
The main components of biogas are methane (CH₄) and carbon dioxide (CO₂). Its composition typically includes:
- 50–70% methane (energy-rich component)
- 30–50% carbon dioxide
- Trace gases like hydrogen sulfide (H₂S), nitrogen, and water vapor
5. What is a biogas plant and how does it work?
A biogas plant is a facility that converts organic waste into biogas through anaerobic digestion. It works in the following steps:
- Organic waste (e.g., cow dung) is fed into a sealed digester
- Microorganisms decompose the waste without oxygen
- Biogas accumulates in a gas holder
- The leftover slurry is removed and used as fertilizer
6. What is the difference between biogas and natural gas?
Biogas is a renewable fuel produced biologically, while natural gas is a fossil fuel formed over millions of years. Key differences include:
- Origin: Biogas from organic waste; natural gas from fossilized remains
- Methane content: Biogas has lower methane percentage
- Renewability: Biogas is renewable; natural gas is non-renewable
7. Why is biogas considered an eco-friendly fuel?
Biogas is considered eco-friendly because it reduces waste, lowers greenhouse gas emissions, and is renewable. Its environmental benefits include:
- Recycling organic waste like dung and food scraps
- Reducing methane release into the atmosphere
- Producing organic fertilizer as a byproduct
- Lower carbon footprint compared to fossil fuels
8. What raw materials are used to make biogas?
Biogas is produced from biodegradable organic materials. Common raw materials include:
- Animal dung (especially cow dung)
- Kitchen and food waste
- Agricultural residues
- Sewage and wastewater sludge
- Plant biomass
9. What is the role of methanogens in biogas production?
Methanogens are microorganisms that produce methane during the final stage of anaerobic digestion. Their role includes:
- Converting acetic acid into methane and CO₂
- Using hydrogen and carbon dioxide to form methane
- Maintaining the stability of the digestion process
10. What are the advantages and disadvantages of biogas?
Biogas has both benefits and limitations as a renewable energy source.
- Advantages: Renewable, reduces waste, produces organic fertilizer, lowers greenhouse emissions
- Disadvantages: Initial setup cost, requires regular maintenance, gas production depends on temperature and feedstock quality
