[Biology Class Notes] on Biogas Pdf

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 –

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.

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.