Biogas Energy - Definition, Advantages

Introduction

Biogas energy is obtained from biomass through physical and chemical process. The Law of energy conservation says that - Total energy during any chemical or physical process for an isolated system is always conserved. It means it doesn’t increase or reduce but merely changes its form. But we often hear that the world is going to face an energy crisis very soon. It is because, in certain processes, energy gets converted in such a form that is unusable for us. There are various forms of energy, for example -Light, Sound, thermal, etc. We can reuse certain forms and certain forms can’t be reused, although they are present in the universe. Energy sources can be divided broadly into two categories.

• Renewable energy sources

• Non-renewable energy sources.

Renewable energy sources can be used again and again, Solar energy, Wind energy, and Bio-mass energy are some common examples of this category. Coal, natural gas, and nuclear energy are common examples of Non-renewable energy sources since they can be used only once. Nowadays the whole world wants to increase its dependence on renewable energy sources since non-renewable energy sources are limited. Bioenergy can be a good alternative to ,conventional energy sources.

Biomass and Bioenergy

Energy can be drawn from organic materials which arise from the plants. It is called Bio-energy. These organic matters are called Biomass. There are two types of biomasses -

• Raw Biomass: It is obtained from raw material. Examples - grass, crop, forest products

• Secondary Biomass: Some materials that were originally raw biomass but have undergone a significant change now are called secondary biomass. Examples: paper, cotton, rubber, etc.

The energy in Biomass comes from Photosynthesis and the energy is stored in chemical bonds. These bonds break in combustion or decomposition and release chemical energy stored in them. Cow Dung cake is a common example of biomass in villages. It can be used as fuel. But it is very low-yielding biomass. This means its energy output is very less. Also, it produces a lot of smoke which is not good for the environment.

Charcoal is high-yielding biomass, it can be obtained by burning wood in suitable conditions. Its heat generation capacity is very high. There are other methods also to convert biomass to energy. Biogas technology is widely used to convert plant materials to energy. These materials are decomposed in presence of oxygen and it produces Bio-Gas. Biogas plants are very useful in areas where there is no alternate source of energy. One can also use biogas as a fuel in liquid form and it is very efficient there.

Advantages of Biogas

These are the following advantages of biogas.

Renewable

As long as there is enough waste in the plant, biogas production remains uninterrupted. The only thing we need to do is to remove the used slurry at a regular time and add the new waste material.

Pollution Free

It is a clean source of energy. In the plant, the Bio digestion process takes place, which doesn’t produce any polluting gas. Since combustion doesn’t take place in this process, it also keeps checking on greenhouse gases. It doesn't leave any residue like the burning of wood.

Cheap

Its cost is very low. With the emerging new technologies, this cost will reduce significantly. It can be used for heating and producing electricity. Cooking with biogas can also be an alternative to conventional gases.

Fertilizer

The digestate coming out of the plan can be used as a fertilizer. Hence it can be an alternative to chemical fertilizers which adversely affect the soil.

Reduces Waste Material

Gas Plants mostly use the waste material. Hence it also helps us in countering water and land pollution.

The Disadvantages of Biogas

There is no question that Biogas is very useful in producing renewable energy. However, there are certain disadvantages too.

• Less technological advances - Although there is a lot of research going on in this field, unfortunately, new technologies failed in simplifying the process and making it cheaper. Hence mass-scale production for large-scale populations is not cheap.

• Unstable - The main component of biogas is methane. This is very flammable if exposed to oxygen. Therefore, there can be a danger of explosion.

• Impurities - Even though biogas is refined but still it has many impurities. They work as agents on engines and adversely affect them.

• Unviable in dense populations- Biogas production is viable only in those places where there is plenty of raw material for it. Hence it is suitable for only rural or semi-urban areas.

Biogas and Biogas Plant

The main component of biogas is methane, almost 75% of biogas is methane. It also contains Carbon dioxide and methane.

It is produced using the principle of anaerobic fermentation. Forms of biomass such as animal dungs, plant wastes, industrial wastes, and human excreta can be used in a biogas plant. It is also known as the gobar-gas plant.

A biogas plant is a dome-like structure. It has the following parts -

• Mixing chamber

• Digester tank

• Inlet and outlet pipe

• Biogas pipe

• Expansion chamber

Fmarree, Biogas plant sketch ENG

Process

• A mixture of biomass and water is prepared in a mixing chamber. It is usually on the ground level. This mixture is called slurry.

• The slurry is moved to the inlet chamber through a pipe called inlet pipe. This air-tight chamber is called a digester.

• The plant is left for 2-3 months. No new slurry is added in this duration.

• In this period, anaerobic digestion takes place inside the chamber. It produces the biogas.

• Biogas being a very light gas rises and gets collected near the gas holder. Since the chamber is air-tight additional gas then starts to push the slurry itself. Then the used slurry through the outlet pipe moves to the expansion chamber.

• The gas collected near the gas collector can be used through the biogas pipe. The used slurry has nitrogen and phosphorus. Hence it can be used in the growth of plants.

Conclusion

Bioenergy is the source of renewable energy. It is very clean and environmentally friendly. Biomass is used to produce such kind of energy. It has many advantages over other methods of energy generation but has challenges too. The biogas plant’s main component is methane. It can be used to produce fuel, thermal energy, or electrical energy. However, it still demands many technological innovations to increase its yield.

FAQs

Q1. Write the Photosynthesis reaction.

Ans. This process is essential for the food of plants. Water and carbon dioxide in presence of sunlight and chlorophyll produce glucose.

$$\mathrm{6CO_2 +6H_2 O \:\rightarrow C_6 H_12 O_6+6CO_2+6H_2 O}$$

Q2. What can be other energy sources of renewable energy in the future?

Ans. Oceanic, Geo-thermal and Hydrogen fuel can be very important sources of energy in the future

Q3. What is the composition of the gases in bio-gases?

Ans. Methane is the main component of biogas (75%). Carbon dioxide is 25-50% and nitrogen is around 2-8%

Q4. What is bio-fuel?

Ans. Bio-fuel is a fuel obtained from biomass. Bioethanol and Biodiesel are some of their common examples.

Q5. Which bacteria are responsible for the fermentation of biomass?

Ans. Methano bacteria is responsible for the anaerobic fermentation of biomass.