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The Ecology of Thermal Power

by
Dr. Yashpal Singh
Chief Environmental Officer
U.P.Pollution Control Board
PICUP Building , Vibhuti Khand
Gomti Nagar
Lucknow -INDIA
Earth has evolved out of millions of years of intense Biogeochemical activity. Early earth did not have free oxygen, the environment was anoxic, the type you have besides polluted rivers and lakes, composed of marsh gases like Hydrogen Sulphide, Ammonia and Methane etc. It was within this environment and the large water masses that the precursors to early life developed. The system was chemoautotrophic and fermentative. The end products of metabolism were anaerobic gases, the type I have mentioned above. Out of a total of 5 Billion years of existence it was only about 2.8 Billion years ago that the most remarkable synthesis occurred on earth. The synthesis of chlorophyll triggered a process in which the Carbon Dioxide present in the atmosphere (probably about 10000 times more than of now) entered a reaction with water in the presence of sunlight. This was the beginning of a transition from the chemoautotrophic, fermentative and anaerobic mode of metabolism to the autotrophic, photosynthetic and aerobic form of metabolism. The process also heralded the way for the evolution of plants - for the fixation of carbon and nitrogen- the synthesis of biomass and all primary food production. Oxygen evolved as a by-product of the reaction but it took another about 0.8 billion years for earth to get free Oxygen. The all-important ozone layer was formed. As plant activity achieved dominance plant material became embedded in the lower crusts of the earth to finally form fossils. Coal is one such fossil, which has been thus formed. Man in his quest for excellence, saw this coal and recognized its potential as a slave. He had discovered fire already. This was the beginning of the Industrial revolution- of smoking chimneys serving as signatures of prosperity and development. Little did man know that the process could recoil as a danger to mans very existence on earth. That man would eventually cut the very branch on which he is sitting. Electrical energy is a very important part of all development activity. 1995 estimates for the per capita consumption of electrical energy in India were 360 units which compares very badly with 6000 to 10000 units from the industrially developed countries. Estimates for the demand for power during1992-1997 reveals a demand of 1783989 million kWh, a supply of 1626544 kWh and a deficit of 8.8% on the demand. Indias coal reserves are estimated to be just about 1% of the worlds reserves while its population is 16% of the global population. India has a coal reserve of 200 billion tons and a current annual production of 295.93(1997-1998) million tons. Seventy percent of the total coal production and virtually the entire lignite production goes into power generation. In the early years of this century India will be producing 400 million tons of coal and lignite of which about 330 million tons would be needed for power generation.

Interestingly the production of coking and non-coking coals for 1962-1963 was just 55.23 million tons. About 75% of electrical energy is produced by the thermal power plants in India. Emissions from the combustion of coal are one of the basic environmental problems associated with the thermal power plants. The World Health Organisation has prescribed the following emission factors for thermal power plants: Particulates- 3.5(A) Kg. per ton of Lignite burnt; 8(A) Kg. Per ton of Bituminous coal burnt; 8.5 (A) Kg per ton of Anthracite burnt. Here A is the ash content of combustible coal by weight. Sulfur Dioxide- 15 (S) Kg. Per ton Lignite burnt; 19 (S) Kg. Of coal and Anthracite burnt. Here S is the percentage combustible sulfur by weight. Nitrogen Oxides- 7 Kg. Per ton of lignite burnt, 9 Kg. Per ton of Anthracite and 9Kg. Per ton of Bituminous coal. Hydrocarbons- 0.5 Kg per ton of lignite, 0.015 Kg. Per ton of Anthracite burnt and 0.15 Kg. Per ton of bituminous coal burnt. Carbon monoxide- The emission of carbon monoxide from all sources is prescribed as 0.15 Kg. Per ton. Indian coal has a high Ash content sometimes exceeding 40%and a Sulfur content ranging from 0.2 to 8 % with an average of 2%. With low conversion efficiency, thermal power plants release almost about 1.5 to 2 MW of thermal energy per MW of power produced in the environment. About 15 % of this is released along with the flue gases and the rest is discharged along with cooling water. It is estimated that a 500MW coal fired power plant having no pollution control equipment would emit nearly 100 tons of Sulfur Dioxide, 20 tons of Nitrogen Oxides and 6 tons of Ash daily. Existing power plants produce about 50 million tons of fly ash per annum needing 40000 acres of precious land for disposal of fly ash during their span of 30 years. Combustion products from thermal power plants have great environmental significance. Acidic gases have a tendency to form acid rain. While the problem of acid rain is not yet severe in India yet the increasing use of coal is likely to increase the possibility. Soot from chimneys has a low particle size and may tend to deposit in the tissues of lungs where it embeds itself, may stay for two to six weeks and in the process because of adsorbent capacities, adsorb acidic gases, heavy metals and other particulate air pollutants which are inhaled. Heavy metals are an important constituent of fossils and combustion of coal releases in the atmosphere a number of heavy metals. These either come out as slag from boilers or are impregnated on the soot particles and with the slightest of acidic conditions may resolubilise in the environment causing metal pollution of air and water. This class of pollutants, because of bioaccumulative properties needs special mention. Bioaccumulation leads to magnification and long term exposure to very small concentrations may cause severe problems. Episodal pollution of this kind is best exemplified by the Minamata Bay incident where Methyl Mercury created problems of fish and human mortality. In a 200 MW power plant in India burning about 9000 tons of coal per day leaching of a mere 15% of heavy metals from the surface of Ash will cause a nearby river to receive daily 208 Kg of Iron, 56 Kg of Zinc, 45 Kg of Copper, 5 Kg.of Cadmium, 56 Kg of Nickel, 4.6 Kg. of Uranium, 16.5 Kg of Thorium, 60.6 Kg of Chromium and 11.2 Kg of Cobalt daily. The transformation, which these metals undergo in the polluted anaerobic waters, the effects of bioaccumulation on the flora and fauna and the impact of biomagnification need special attention. Chlorine and Fluorine are also constituents of coal and it is expected that photochemical reactions would trigger out a process of synthesis of Chlorofluorocarbons which may have far reaching consequences. We all know by now that Chlorofluorocarbons are causative in the catalytic breakdown of Ozone and the consequent depletion of the ozone layer. The life of these molecules (Chlorine) is almost 100 years and it is for this extent of time that it would go on damaging the ozone layer. We must be cautious. Most of the gases released from fossil fuel burning contribute to the green house effect. Global warming is a consequence. It is also significant that every three tones of carbon burnt consume 8 tons of oxygen and that we are drawing excessively on the oxygen resource of earth. Fly Ash disposal is a major concern for the thermal power plants. Generally, for every MW of installed capacity approximately one acre of land is required for the ash generated, the material accumulating to a height of 8 - 10 metres. Fly ash is a harmful environmental pollutant. Being light it gets air-borne very fast. Long inhalation causes silicosis, fibrosis of lungs, bronchitis and pneumonites etc. It corrodes structural surfaces and deposition effects horticulture. Slurry disposal lagoons/ settling tanks become sources of mosquitoes and bacteria. It holds the potential to contaminate the underground resources with traces of toxic metals present in it. The ash handling system may account for 5% of the total cost of a power project.

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.