RBSE Class 12 Biology Notes Chapter 20 Bioenergy

Rajasthan Board RBSE Class 12 Biology Notes Chapter 20 Bioenergy

Introduction

1. Increase is living standard of humans, has led to increase in consumption of energy. At present developmental index of any country is measured in term of-energy consumption per person. Gross National production is equivalent to consumption of energy.

2. It is estimated that in the industrial projects operating world over approximately 85% of the t,ptal energy consumed is non-renewable energy. Of the non-renewable energy about 76% comes from fossil fules (Petroleum products, coal etc.) and only 6.0% is obtained from nuclear pow er resources (Radioactive substances such as Uranium etc.) Of the 18.0% renewable energy used, 11.0% is derived from biomass and remaining 7.0% from hydro power, solar energy, wind energy arid geothermal power.

Non renewable energy sources

1. The non-renewable source of energy are present in nature in limited amount and their continuous consumption is resulting in to their depletion. As the regeneration of these resources is not possible it is not far off that these will be completely exausted and shall not be available one day.

2. Renewable energy sources

3. The renewable sources of energy are those which exist in nature and can be regnerated. Hydro power, wind energy, bioenergy, solar energy, tidal energy and geotherma energy are collectively included in this category.

Bioenergy

1. The energy obtained from biomass or biosources is known as bioenergy. Normally biomass word is used for the material synthesized by plants in the process of photosynthesis. Hence the total dry weight of plants is considered as biomass, but we know that all other organisms directly or indirectly depend on plants for their survival. Hence the organic substances produced by the entire living world can be called as biomass.

Obtaining energy by burning plants and their wood has been a practice since ancient time. Regular and indiscriminate use of plants as source of energy has developed a pressure on forests and has caused environmental problems. With the progress in scientific research different forms of bioenergy have been developed. The immediate need of present age is to make maximum use of such energy sources which can be regenerated and are environment friendly, such as bioenergy, because bio-energy has following useful features :

Useful features of Bio-energy

Bio-energy is relatively cheaper, renewable and can be regularly generated at local level.
The amount of CO₂ and SO₂ produced by their use is much low and causes minimum harm to environment, hence less polluiton.
The raw material of generating bio-energy is easily available as even the dry dumping yard waste (Garbage & bio waste) can be utilized for production of bio-energy.
As it is renewable, hence it’s availability will never become zero.

Sources of Bio-energy

Following are the main sources of bioenergy

1. Biomass
2. Fire wood
3. Cow dung : Methane or Bio-gas
4. Biodiesel
(a) From vegetable fatty acids
(b) From petroplants.
5. Ethanol from starch and lignocellulose
6. Algal hydrogen factory.

Biomass :

The basic source of bioenergy is sunlight. Out of total solar energy reaching to earth, 0.2% of light is stored in
plants in form of bio-mass. Al l those materials formed from photosynthesis is called bio-mass. We can include all living organisms and their by products in category of bio-mass, which may be source of energy’.

Example :

Plants containing lignocellulose : Eucalyptus, Leucena, Maize, Sugarcane, Sugarbeet, Pine tree.
Aquatic plants : Water hyacinth (Jal kumbhi).
Waste products : Manure, refuse, wood, remains of crops-straw, lemon rinds, remains of sugarcane, jaggery, fibres of coconut, mahua, flower-leaf, cow-dung etc.

Wood

Wood is most commonly used fuel and is being used by human from long time back. About 50% of Indian population use wood fuel for domestic and cottage industries because it is easily available and it’s use does not require specific knowledge. It is used in maximum amount in developing and undeveloped countries of Asia and Africa. Use of wood as fuel in our country is a major cause of deforestation and destruction of wild life and also a major source of environmental pollution in our country.

Salient features of good wood fuel:

It must have high combustion potential.
It must have high calorie value so as to generate more heat on combustion.
It should not split and break into pieces on combustion.
The amount of moisture and resin content should be low.
It should not produce stinking odour on combustion and should produce minimum smoke.

Some plants which provide good quality fuel wood are as follows:

	Hindi Name	Botanical Name
1.	Desi babool	Acacia nilotica
2.	Kumpta	Acacia senegel
3.	Angrezi babool	Prosopois juliflora
4.	Kliair (Kattha)	Acacia catechu
5.	Siris	Albizzia lebbeck
6.	Jamun	Syzygium cumini
7.	Khejri	Prosopois sineria
8.	Ardu or Mahaneem	Aclenthes cixselsa
9.	Aam (Mango)	Mangifera indica
10.	Sali, Looban	Boswellia cirrela
11.	Dhokda	A nogeisus pendula
12.	Rouziz (Safed Kikar)	Acacia leucophloia

Cowdung and Bio-gas

1. More than 70% population of our country resides in villages where animal live stock is plentiful and easily available. Generally the dung obtained from cattle is used for burning by making cow dung cakes. Instea d of burning, the dung should be utilized for making biofertilizer. For this the dung should be filled into big pits regularly. Pits should be made on higher level and it’s depth should not exceed one metre.

2. Fermentation of organic compounds is done by bacteria and the gas so formed is known as bio-gas. In India, cowdung is used for bio-gas production. In many villages “Gobar” gas plant (bio-gas plant) is being operated for energy production. This is not only cheap source of energy’ instead it plays its important role in controlling environmental pollution.

3. In “Gobar” gas plant anaerobic fennentation is completed in three steps :

In first phase, anaerobic bacteria convert complex organic compounds such as cellulose, hemicellulose, into simple compounds.
In second phase both partially aerobic and anaerobic bacteria convert simple components first into carbonic acid and finally into acetic acid.
In third phase Methanobacteria convert acetic acid into methane gas. The residue in biogas plants is called slurry’. It is dried and further utlizied as manure.

Capacity’ of Biogas is little less than natural gas because of 31% carbondixoide gas present in Biogas. If the percentage of CO₂ can be reduced then the calorie value of this gas can be increased. Presently extensive research is going on so that calorie value of gases produced by’ fermentation of bio w’aste materials can be increased. In 1961, Gobar Gas Research Station was established at Ajeetmal in Ittawa district of Uttar Pradesh.

Biodiesel

Liquid substances derived from biological products resembling to diesel are called biodiesel. Biodiesel is environment friendly renewable fuel composed of vegetable oils, fats and latex. Chemically it is named as fatty acid methyl ester, FAME.

Solar energy is used by the plants and it is stored in the form of fats, sugar or starch. Plants also store hydrocarbon in a special form of storage oil in their seeds-which is used as source of energy at the time of germination of seeds. It is this hydrocarbon which has laid the foundation of the biodiesel hypothesis. Rudolf Diesel (1895) made engine by using these oils only.

Bioresources of Biodiesel

Bioresources of biodiesel can be divided into two parts
(i) Vegetable fatty oil
(ii) Petro plants.

(i) Vegetable Fatty Oil: Seeds of many plants such as of soyabean, mustard, castor, flax, sunflower, ground nut, Jatropha, Pongamia (Karenz) etc. contain adequate amount of lipids and fatty acids. ‘

(a) These lipids store high amount of energy.

(b) The liquid obtained by esterification of these lipids, is called biodiesel. In the pure form this liquid can be used in diesel engine wihtout any modification.

(c) But we know that the cost of the vegetable edible oil in developing countries is much higher than the cost of diesel.

(d) Moreover, the production of these vegetable oils is less in comparison to their demand.

(e) Hence the possibility of use of the vegetable oils as source of biodiesel in developing countries is negligible. However research is being done so that non edible oils obtained from other plants can be used for this purpose. In this contex following plants may play important role.

Jatropha curcas
Pongamia pinnata
Madhuca indica
Ricinus communis

(ii) Petro Plants :

(a) The shortage of conventional sources of energy and the apprehension of these getting exaust, has led the scientists to discover such plants, the products of which can be used in place of petrol and diesel. Several plants belonging to family Apocyanaceae, Asclepiadaceae, Euphorbiaceae,Sapotaceae, Urticaceae Compositae etc. produce petro products.

(b) The photosynthetic products in these plants convert in to latex. The latex is rich in hydrocarbons. Hence this can be used in place of petrol or can be mixed with petrol in petrol engine vehicles.

(c) Extensive research work is being carried out on hydrocarbons producing plants in Indian Institute of Petroleum, Dehradun. Chemical analysis of latex of Euphrobia lathyrus has led to formation of gas similar to gasoline. Latex obtained from Calotropis procera contains high amount of hydrocarbons of which 78.03% is carbon, 1.22% is hydrogen and and 10.71% is oxygen.

The ratio of carbon and hydrogen in this is equal to the gasoline or liquid fuel. As these plants are looked as source of alternative fuel in future, these are called as petroplants and their cultivation as petro crops.

Important Latex producing petroplants

Many species of Euphorbia such as lathyrus, E. antisyphilitica, E. canducifolia, E.tirucalli etc.
Hevea brasiliensis
Plumeria sps
Calotropis procera
Ficus sps.
Acharus zaposa.

Production of Biodiesel in Rajasthan and India

1. At present India is able to produce only 30% of petroleum products of its requirements, and rest 70% of petroleum products have to be imported. At present even if 5% biodiesel is mixed with diesel, then we will be able to save lot of foreign currency.

2. According to research, oil obtained from Jatropha curcas can be used as biodiesel. Planning Commission (now Niti Aayog) has planned to grow the trees of Jatropha and Pongamia pinnata as a source of biodiesek These can be grown even in barren land.

3. Planning commission has identified 200 districts in 18 states for growing Jatropha; which includes Rajasthan also. Rajasthan State Government under leadership of Chief Minister has constituted a “Biofuel mission”.

4. Transesterification plant (device) as well as oil producing units from seeds will be establishment. This will be a part of Biofuel mission.

5. Cultivation of Jatropha is not only important from view point of biodiesel production, but through this the uncultivated land can also be brought under cultivation.

6. This will be important for .ecology and conservation of bio-diversity. This will become a source of employment and will generate income for financially backward people and farmers. . ,

Importance of Biodiesel

Biodiesel also act as lubricant. Itincreases efficiency of engine and cost of maintenance is reduced.
By using this biodiesel, carbon monoxide and suspended particle emission is comparatively less.
This is alternative sources of energy and can lead to generate employment and increasing income etc.
The petro plants can be grown in less productive, barren, non irrigated and road side land. The biodiesel thus can play important role in proper use of waste land, economic stability and development of the nation.
Biodiesel is one of best alternative fuel. This can be obtained by growing petro plants in less productive and barren lands.
By growing petro crops high quality fuel can be obtained along with environmental protection and conservation, improvements in efficiency of automobiles, rural employment, and increased independence as well as savings in expenditure incurred on petro-products.

Production of Ethanol from Starch and Lignocellulose :

1. Starch crops (Rice, Millets) and Sugar plants (Sugarcane and Beet root) are important crops for biofuel production. By using these important sources of energy, we can produce many products. Starch and Sugars obtained from these plants can be converted in to ethanol.

2. Cellulose is an important product of plants and with the help of cellulase enzyme it can be broken down into glucose and finally into ethanol. In woody plants lignin is also found along with cellulose as With the help of enzymes lignocellulose can be converted into sugar and afterwards with the help of yeast this sugar is converted into ethanol by fermentation process.

3. Some plants such as sugarcane, potato, beet root are used as raw materials for ethanol production. These plants through which ethanol is produced are called energy plants. New techniques are being developed to use this ethanol in automotives. Brazil is the leading country to use this technique. In Brazil, Brazilian National alcohol programe was started in 1975. Now in Brazil all cars are running on alcohol or 20% mixture of ethanol mixed with petrol.

4. Sugarcane is one of the main cash crop grown in many states in India. Molasses (Black treacle is a viscous
product resulting from refining sugarcane or sugarbeets into sugars) are by product of sugar industry. 65.5% pure ethanol is produced from molasses but for mixing with petrol, 66.8% ethanol purity is required. By using distilliation plant, 66.8% ethanol can be derived from molasses by modification. Government of India has established three plants for mixing 5% ethanol with petrol for experimentation. These are established in Bareilly (UP) and Manmard and Meeraj (Maharashtra).

Algal hydrogen factory

Algae are photosynthetic aquatic plants and under normal conditions produce carbohydrates and oxygen by photosynthesis as of higher plants. In the year 2000 Anastasios Melis proved in his experiments that if during day time supply of Oxygen and Sulphur is stopped to algae then metabolic reactions in algae change and these starts producing II₂ in place of O₂ in photosynthesis. We know that II, is highly inflammable so can be important source of energy. If this experiments will be successful, this would become a great source of energy in future.