Single Cell Protein and Bioenergy NEET Notes | EduRev

Biology Class 12

NEET : Single Cell Protein and Bioenergy NEET Notes | EduRev

The document Single Cell Protein and Bioenergy NEET Notes | EduRev is a part of the NEET Course Biology Class 12.
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It is a microbial biomass. This biomass is obtained from both mono and multicellular microorganism.

Single cell protein can be produced using algae, fungi, yeast and bacteria. Commercial production of S.C.P. is mostly based on yeasts and some other fungi e.g. fusarium graminearum.

(i) SCP may be used directly as human food supplement, or else

(ii) It may be used in animal feed to at least partially replace the currently used protein-rich soyabean meal and fish proteins, and even cereals, which can be diverted for human consumption


The SCP processes and products offer several advantages as listed below :

1. The SCP is rich in high quality protein and is rather poor in fats, which is rather desirable.

2. They can be produced all the year round and are not dependent of the climate (except the algal processes).

3. The microbes are very fast growing and produce large quantities of SCP from relatively small area of land.

4. They use low cost substrates and, in some cases, such substrates which are being wasted and causing pollution to the environment.

5. When the substrate used for SCP process is a source of pollution, SCP productioe helps reduce pollution.

6. Strains having high biomass yields and a desirable amino acid composition can be easily selected or ptoduced by genetic enginnering.

7. Some SCPs are good sources of vitamins, particularly B-group of vitamins, as well, e.g., yeasts and mushooms.

8. Mushrooms are considered as delicacy in the human diet.

9. At present,SCP appears to be the only feasible approach to bridge the gap between requirement and supply of proteins.

Production of SCP reguire carbon source and other nitrogen, phosphorus and other nutrients needed to support optimal growth of the selected microorganism. SCP process are highly aerobic (except those using algae).

Therefore aeration must be provided.



Only about 0.2 percent of the solar energy that reaches the earth's surface is converted into biomass. Yet this energy trapped annually in the biomass is about ten times the non-biomass energy from other sources (conventional) used by the people the world over. "Bioenergy is the energy obtained from biological sources", broadaly classified into Animal energyandBiofules. Coal, petroleum and natural gas are also of biological origin, but are classified as fossil fuels. Bioenergy is widely used in the developing countries especially in the rural areas.


Animal energy is available in two forms- Human Muscle Power (HMP) and Draught (pronounced draft) Animal Power (DAP). HMP is widely used by women in their domestic chores and by marginal farmers, artisans and non-agricultural labourers HMP forms a sizable part of the energy utilised. It is approximately equivalent to one-fifth of the total electricity generated per year in India.


Biofules or fules of biological origin have been used by man since the discovery fo fire. In spite of the improved methods of obtaining energy, biofules continue to be a major resource. Biofules are renewable, and if used properly and efficiently they can help overcome energy problems of developing countries. With improvements in technology it is becomeing possible to substantially replace fossil fules by biofules. Biomass can be used to generate producer gas to run irrigation pumps, to obtain alcohol, to replace petrol, to generate biogas for cooking and lighting, or merely to generate electricity.

Biofules are obtained from wood and agricultural, agro-industrial and animal wastes, and from plants that produce alcohol, oil and petroleum.


Wood has been used by man from the time he discovered fire. Over half the global population still depends on wood for cooking and heating. Wood is also used as fuel in many industries. The consumption of fuelwood in the world was estimated at 1.7 billion m3 in 1984. Two-thirds of this was utilised by the developing countries in Africa and Asia.

Such massive use of fuelwood has resulted in extensive deforestation and consequent environmental degradation.

A major quantity of wood is used as firewood. The principal advantages of firewood are :

1. It is a widely distributed source of renewable energy.

2. It can be harvested by unskilled labour, using simple equipment

3. When perfectly dry, 99 percent of it is combustible.

4. It is a fuel which produces flame and is well-adapted to heating large surfaces.

5. As all wood is composed essentially of the same substances, wood from most species can be used as fuel.

Plantation of trees for fire wood is calledenergy plantation.

What determines the value of particular wood as fuel.

There are hundred types of wood in a vast country like India. Of these only a few are selected as suitable fuel.

Good firewool must

(i) be highly combustible,

(ii) have a high calorific value,

(iii) be easy to dry,

(iv) not split when ignited,

(v) be non-resinous and non-smoky and

(vi) be free from offensive odours.

Generally speaking hardwood (dicotyledonous) is better than soft wood (gymnospermous) as fuel. The former produces uniform heat over a long period of time. Soft wood burns rapidly to produce intense heat but only for a short period.

Cow Dung Cakes :-In rural areas of developing countries, it is a common practice to use animal dung for making dung cakes which are used for fuel. Thus a potential fertiliser of the agricultural fields is wasted in Burning.

The dung Can be put to a better use if it is used to generate Bio gas (Gobar Gas) and side by side a  stabilised residue to serve as the fertiliser.

Single Cell Protein and Bioenergy NEET Notes | EduRev

The energy yield of Biogas is lower than that of dung cakes but the efficiency of Biogas burners  is very high.
Thus over all result indicates that production of biogas is more cost effective.
The biogas plant consists of a concrete tank (10-15 feet deep) in which bio-wastes are collected and a slurry of during is fed. A floating cover is placed over the slurry, which keeps on rising as the gas is produced in the tank due to the microbial activity. The biogas plan has an outlet, which is connected to a pipe to supply biogas to nearby houses. The spent slurry is removed through another outlet and may be used as fertiliser. Cattle dung is available in large quantities in rural areas where cattle are used for a variety of purposes. So  biogas plants are more after build in rural areas. The biogas thus produced is used for cooking and lighting. The technology of biogas production was developed in India mainly due to the efforts of Indian Agricultural Research Institute (IARI) and Khadi and Village Industries Commission (KVIC)

Single Cell Protein and Bioenergy NEET Notes | EduRev

The organic wastes from the farmhouse cow dung, wastes, urine, faeces etc. can be used economically for producing of Gobar gas (Bio gas). It consists of methane (50-70%), CO2(30-40%) and traces of hydrogen, nitrogen and hydrogen sulphide.
Biogas produced by anaerobic fermentation of waste biomass.

Anaerobic fermentation of waste biomass can be visualised in three stages :-

1. The facultative anaerobic microbes degrade the complex polymers to simple monomers by enzymatic action.

The Polymers like cellulose, hemicellulose, proteins and lipids get degraded into monomers but lignins and inorganic salts are left as residue because they do not degraded.

2. In second stage, monomers are converted in to organic acids by microbial action under partially aerobic conditions which are finally converted to acetic acid.

3. In third stage acetic acid is oxidised in to methane by the acitivity of anaerobic methanogenic bacteria. These bacteria are commonly found in the anaerobic sludge during sewage treatment. These bacteria are also present in the rumen (a part of stomach) of cattle. A lot of cellulosic material present in the food of cattle is also present in the rumen. In rumen, these bacteria help in the breakdown of cellulose and play an important role in the nutrition of cattle. In this whole process digestion ofcellulosetakes place at very slow rate so that it is the "rate limiting factor in biogas production".

Advantage : 

1. Biogas can be easily stored to provide more efficient source of energy.

2. It can be used for various purposes in addition to its use for cooking.

3. One bye product of this process is a stabilised residue which serves as a good fertilizer.

4. It reduces the overgrowth of faecal pathogens because of non availability of exposed waste. Thus it is significant in improving sanitation.

5. It also reduces the chances of spreading of pathogens in the field condition, minimising the incidence of diseases in a crop year after year.

6. Its calorific value is about 23-28 MJ/m3.

Plants as Sources of hydrocarbons for Producing Petroleum Melvin Calvin has identified certain plants which produce hydrocarbons. The plants of Euphorbiaceae, Asclepiadaceae and Apocyanaceae produce latex a milky secretion which contains hydrocarbons.

The liquid hydrocarbon of the latex can serve as the liquid fuel which can replace the fuel requirement of automobiles either mixed with petrol or as entire fuel. Plantation of such type of plants are called Petro Plantation. This is the such type of method in which source is available only through the demand.

Alcohol as fuel :-

1. Ethanol (C2H5OH) can be partly or wholly substituted for petrol in automobiles after suitable modifications in Engines.

2. Raising of crops like Sugarbeet, Potato, Maize, Sugarcane, Tapioca and Molasses for producing ethanol is called energy croping.

3. Alcohol has been successfully used as motor fuel in Brazil and it is the first leading country in the world. "Ethanol from starch and lignocellulose"

Ethanol or Ethyl Alcohol obtained from starch sources.

Ex. Potato, Molasses, waste sulphite liquor and wood sugars (lignocellulose) Method :- The starch is hydrolysed into sugars which is then fermented in to alcohol.

Single Cell Protein and Bioenergy NEET Notes | EduRev

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