The consumption of petroleum and natural gas is maximum in the developed countries and has become the status symbol of a country. USA is the largest consumer of petroleum in the world (about 80 per cent of total energy consumption in USA).
The Industrial Revolution (1780) was initially fuelled by coal but later on preference was given to oil and gas which provide cleaner fuels and easy transportation. The world reserve of petroleum is about 800 billion barrels (1 barrel = 31.5 gallons = 120 litres) which will last for less than 100 years.
0 20 40 60
80 Fuelwood Coal Petroleum and Natural gas 100 1860 M aj or E ne rg y S ou rc es (% ) 1900 1940 1980
Fig. 2.9: Energy consumption patterns in USA 2.6.5 Hydroelectricity
The output from hydroelectricity (electricity from water) accounts for 21 per cent of total electricity generation, which is less than that from thermal power but greater than that from nuclear power. In Venezuela, South America, 10,000 mega-watts of hydroelectricity is produced which is equivalent to the production of electricity from 10 thermal power plants. In India, if water resources are properly utilised, it may be possible to generate more than 10,000 megawatts
of electricity. But at present, only 16 per cent or 6,500 megawatts of hydroelectricity is generated.
For generation of electricity from hydel project, it is nec- essary to utilise energy produced from the descent of water from higher to lower level. In practice, a water reservoir is constructed by means of dam in a river for storage of water. Subsequently the stored water is released from upper level into a water-driven turbine placed at a lower level (Fig. 2.10) whereby electricity is generated. The hydel projects of Maithon, Panchyet and Jaldhaka are typical examples.
Turbine Electricity River Water Reservoir Dam Water
Fig. 2.10: Hydroelectricity from hydel project
The merits of hydroelectricity are: (1) clean source of energy; (2) no emission of greenhouse gases; (3) no consumption of fuel; (4) no need of high technology. But there are several environmental issues—flora and fauna in the region are disturbed due to construction of dam; local people become refugees as they are uprooted from their houses; the capacity of the reservoir gets reduced due to siltation; occurrence of floods in the area when surplus water has to be discharged in monsoon season. Hydroelectric dams are costly and take a long time for construction. In order to make hydroelectricity generation viable, it is necessary to adopt a long-term programme of afforestation, environmental
conservation, housing, public health and transport and ensure close co-ordination among these departments. 2.6.6 Nuclear Power
It contributes only 5 per cent of total electricity generation. Nuclear power plants do not emit polluting gases such as carbon dioxide, sulphur dioxide, like thermal power plants. But they have some severe drawbacks, viz. they are costly and release large quantities of radioactive fission products.
The radioactive wastes remain lethal (deadly) for thousands of years and for this no foolproof disposal method has been devised. That is why big nuclear power projects have not succeeded in the long run.
In India, the production target was fixed at 10,000 megawatts by 2000AD, but the actual production is much less in the nuclear power stations at Tarapur, Rajasthan and Chennai. Nuclear power plants cannot match thermal power plants at present but in future, its unlimited resources will allow it to dominate the energy scenario when other energy resources are exhausted.
Zirconium–94 Caesium–140 Neutron Neutron Neutron Energy Uranium–235
At present, nuclear fission is used to produce nuclear power. Heavy large atoms like Uranium and Plutonium split up into smaller atoms when bombarded by neutrons (nuclear particles with mass 1 and charge 0). This splitting or fission liberates vast amounts of energy, which through conventional techniques is converted into electricity. Thus nuclear power is generated.
It has been calculated that 1 kg of Uranium-235 on a complete fission by slow neutrons releases energy equal to 1.7 × 1013 calories. This means energy-wise, 1 lb. of Uranium- 235 ≡ 5 million lbs. of coal ≡ 20 million lbs. of T.N.T. (highly explosive chemical).
This is the secret of nuclear energy/power. 2.6.7 Wood
Wood is a major renewable natural resource. The major important products are wood, paper, cellophane, rayon, plywood, plastic, particle board, turpentine, methanol, etc. In USA, the production of wood and wood products is the fifth largest industry. Ideally, as in USA forests cover 38 per cent. of the total land area; in India it has come down to about l5 per cent at present from 80 per cent, 2000 years ago.
It is interesting to compare between India and USA in respect of deforestation. In USA, the Sunday issue of the leading newspaper, New York Times consisting of 500 pages requires 25 hectares (1 hectare = 2.5 acres = 7.5 bighas) of forest. According to an estimate, an American destroys as much forest for his needs for paper as an Indian for his domestic fuel. The value of a 50-year-old tree has been estimated as about more than Rs 20 lakhs—the various functions of a 50-year-old tree are roughly evaluated as follows:
(i) Oxygen production (for 50 years) Rs. 2,50,000 (ii) Transformation into protein Rs. 20,000 (iii) Control of soil erosion Rs. 2,50,000
(iv) Recycling of water and control Rs. 2,50,000 of humidity and atmospheric
temperature
(v) Habitat for birds and other animals Rs. 2,50,000 and insects, etc.
(vi) Control of air and heat pollution Rs. 5,00,000 Total Rs. 15,20,000
This estimate excludes the value of timber/wood for furniture, fuels, medicines, etc. which will be an extra Rs. 3–4 lakhs.
Rayon Cellophane Paper Methanol Plywood Plastics Particle board Wood/ turpentine
Fig. 2.12: Trees—sources of many important products Thus the tree, with its 50-year services as above, costs about Rs. 20 lakhs (1980 estimate) which at present market prices will be around Rs. 40 lakhs. The public should be made aware of the value of a tree and its services to man and environment during its life time.
In India, 76 per cent of population lives in villages— almost all of them use wood as fuel for cooking. This is the main reason for extensive deforestation in rural areas: each
year we are losing about 1.3 million hectares forests. Deforestation helps increase in greenhouse gas, carbon dioxide concentration. Hence for the welfare of the country as a whole, it is essential to minimise deforestation by adopting alternative resources of afforestation on a large scale to meet the needs of domestic fuel.