The Ecology of Thermal Power

Beset with all these problems, yet forming the most important constituent of power generation, thermal power is invaluable. What are then the options available with us to ensure that power production is environmentally sustainable?

Curative strategies for emissions and effluent control exist in the form of bag-filter technologies, multicyclones or electrostatic precipitators, yet their design, operation and maintenance has to be in conformity to Indian conditions. With the higher ash content of Indian coals, electrostatic precipitators designed for non-Indian coals may not generally work in India. Another disadvantage with curative strategies is that they are resource intensive and enhance the environmental cost to the project. Nevertheless they have their own utility and in the present context are very important for pollution reduction. Regulation through legislation has found a place as an efficient tool for pollution control. The Water (Prevention and Control of Pollution) Act 1974 and the Air (Prevention and Control of Pollution) Act 1981 regulate the discharge of water and air pollutants. It is mandatory for all thermal power plants to obtain the consent of the Pollution Control Board to use an effluent outlet or to establish and/or operate a plant. Plants have to ensure that they conform to the standards prescribed by the state pollution control boards. The Environment (Protection) Act 1986 also regulates the discharge of air pollutants.

Standards for the discharge of emissions and effluents have been prescribed specifically for the thermal power plants. It is also provided that the standards prescribed under the E.P. Act have to be observed. The State Pollution Control Board can only make them more stringent but cannot relax them. Standards have been provided for condenser cooling waters, boiler blowdowns, cooling tower blowdowns, ash pond effluents, stack heights for the control of sulphur di-oxide emissions and particulate matter emissions from boilers.

Setting up of standards is a continuing process and more emphasis is being laid in recent times on low particle size pollutants. American standards aim at a regulation of particle size of two microns, while the Respirable Suspended Matter Indian standards generally relate to a particle size of 10 microns. Technology should therefore be always on the lookout for improvements and it is believed that in the coming times, curative strategies would be highly cost intensive and we would have to look at other strategy options.

Amongst other strategy options the first available to us, of course, is to look at alternative production options. Geothermal energy, wind power energy, solar voltaic cells and hydroelectric power generation are some viable options. In an estimate it has been said that a 250 kW wind energy generated system produces 600 MWh per year at a site having moderate wind and helps in pollution control by saving 250 tons of coal and consequently related emissions. By March 1997 India had a cumulative capacity of 900MW of wind farm energy and a potential of 20000 MW. The cost in India was estimated at Rs. 2.25 – Rs. 2.75 per kWh depending upon the site.

It almost compares with the cost of thermal power generation sans of course the environmental cost. Non polluting technology options for power production have therefore to be looked into and it is in this context that Microhydel power generation and generation of power from biomass needs a boost. Indian coal as stated earlier has a very high ash content. Most of the coal is transported from the mines to the power plant and it is apprehended that power plants are generally paying the price of transporting 3 wagons of coal while effectively transporting only 2 wagons. High ash content is also putting pressures on the emission control systems, the boilers and with a huge generation of fly ash, on the requirement of agricultural land for ash disposal.

Means would therefore have to be sought to minimize the impact of coal ash on the economics of power production both in terms of production and environmental costs. One of the options available is the conversion of coal to gas at the mine and transporting gas to power plants. The use of beneficiated coal by thermal power plants may also reduce a great amount of air pollutants and fly ash. Beneficiation is a process of removal of non-combustible matter from the mined coal through the process of pulverization, segregation and washing. The balance of advantage in using beneficiated coal lies with the power plant.

Beneficiated coal is likely to give fiscal benefits in terms of reduction in tonnage to be transported, savings in transportation costs, reduction in bottom ash, reduction in fly ash and a reduction in cost of pollution control apart from the opportunity costs derived out of reduced air and water pollution. Fly Ash can be used for manufacturing bricks, blocks, aggregates and cement. Only a very small percentage (3%-5%) of fly ash generated in India is being used in gainful applications, the corresponding figures for other countries vary from 30%-80%. The FAL-G process that is suitable to make low cost bricks and masonry blocks using fly ash, lime and gypsum involves less investment and needs no brick burning. These bricks are 3-4 times shorter than burnt clay bricks. Surplus fly ash can be used effectively for filling the abandoned mines and can be suitably planted with trees.

Agriculture is also one application which fly ash can augment. Environmentally compatible siting has received considerable attention in the post Bhopal period. While environmental impact assessments of development projects help in minimizing the adverse effects of the activity, environmentally compatible siting protects sensitive public health, life and property. The Environment Impact Assessment notification no. S.O. 60 (E) of 1994 required that all thermal power plants should be required to take an environmental clearance from the Ministry of Environment and Forest, Govt. Of India. These stipulations have been revised and a provision has been made for some clearances to be issued by the State Govt. too. This was through notification no. S.O. 319 (E) dated 10-4-1997.

The procedure involves public hearing also. The Ministry of Environment and Forest, Govt. of India has also notified compulsory utilization of fly ash. Power plants are expected to utilize fly ash in a phased and time bound manner. Brick kilns around 50 Kms. of power plants will have to utilize 25% by weight of fly ash failing which their licenses could be cancelled.

These are then some of the options available for management of pollutants from power plants. Thermal power plants are an essential part of all development activity, but the operation is beset with many environmental problems. The environmental costs of pollution and costs for pollution control are high. While curative strategies serve their purpose but they enhance costs. Solutions would therefore have to be found in choosing less polluting technology options, clean technology options, reuse and recycle of waste fly ash and finally in regulating consumption. This will reduce both the costs on society and the cost on the power plants.

Power projects would increasingly have to augment and upgrade technologies to be compatible with global costs and environmental standards. Environmental conservation should develop as a culture in order to achieve the best results.

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  1. Article is good but the figures are exaggerated,200Mw plant needs around 3000 MT of coal and not 9000 Mt , Average sulphur in indian coal is less than 0.8% and 2% in some coal mines . AS per TERI report sulphur dioxide quantity is 0.2tonnes /MW /day upto 500 Mw and 0.1MT /MW/Day after 500.

  2. Thank.You Mr. Bagchi.Although the text was quoted from reference yet you are absolutely right in your statement. We stand corrected.Thank you once again for your .
    interest in
    Dr. Yashpal Singh


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