30-11-2012, 04:38 PM
Environmental Impact of Emissions from Thermal Power Generation in India
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Introduction
India is the world’s fourth largest economy and has a fast growing energy market. India’s current
power capacity is 30% short of demand. Coal and petroleum are the primary sources of energy. High
ash content in Indian coal and inefficient combustion technologies contribute to India’s emission of air
particulate matter and other trace gases, including gases that are responsible for the greenhouse
effect. The USAID Office of Environment, Energy & Enterprise in India promotes clean energy
development through efficient energy use and pollution reduction. This organization has sponsored
the project, Anthropogenic Emissions from Energy Activities in India, to assess the emissions of
greenhouse and other trace atmospheric gases from energy activities in India.
In this project, we will study India’s present and projected inventory of emissions, study the transport
and patterns of emitted pollutants, and develop a long-term air quality database covering the country’s
various geographical areas. Part I is an estimation of greenhouse and other trace gases from India’s
coal-based thermal power plants. The emission estimates are made for each power plant based on
power generation per day and the coal used per unit generation of power. Part II deals with the
emissions from the vehicular transport using petroleum fuels. This study is currently in progress.
India’s population, second in the world, grows at a rate of about 2% every year and has grown from
300 million in 1947 to more than a billion today. Rising population and changes in lifestyles consistent
with rapid economic growth have accelerated the energy demand. Energy consumption in India has
grown 7,000% from 1950 to 1998. The present annual growth rate of energy consumption in India is
4%. Per capita energy consumption in India in 1997 was 19 million BTU (British Thermal Units),
compared to 323 million BTU in the United States and a world average of 65 million BTU. By the year
2010, per capita energy usage in India is expected to increase to almost 40 million BTU, a two-fold
increase in 13 years.
Thermal Power Plants in India
According to the Central Electricity Authority of India, as of March 31, 1998, 83 steam plants were in
operation in India. These plants generated almost 80% of total generated power for the nation.
Coal consumption by various plants in the country during the year 1997-98 was almost 203 million
metric tons. The consumption of fuels such as furnace oil decreased by more than 32.5%, while the
consumption of lignite coal, a low-sulfur heavy stock (LSHS), a high sulfur heavy stock (HHS), and
diesel oil increased by 7.54%, 31.91% and 33.9%, respectively. Decreased use of furnace oil has
decreased the emissions to some extent.
Emissions from Thermal Power Plants
The main emissions from coal combustion at thermal power plants are carbon dioxide (CO), nitrogen
oxides (NO), sulfur oxides (SO), chlorofluorocarbons (CFCs), and air- borne inorganic particles such
as fly ash, soot, and other trace gas species. Carbon dioxide, methane, and chlorofluorocarbons are
greenhouse gases. These emissions are considered to be responsible for heating up the atmosphere,
producing a harmful global environment. Oxides of nitrogen and sulfur play an important role in
atmospheric chemistry and are largely responsible for atmospheric acidity. Particulates and black
carbon (soot) are of concern, in addition to possible lung tissue irritation resulting from inhalation of
soot particles and various organic chemicals that are known carcinogens.
Carbon dioxide emissions
Utilities burn mostly coal with approximately 10 –30% excess air. The total carbon obtained from
analysis is converted to CO after the reaction (combustion) is complete. Total CO emissions for 1997
from all the power plants in India are estimated at 1.1 Teragrams (Tg) per day or 397 Tg per year.
Average CO emission per unit of electricity is 1.04 Gig grams (Gg). Technological improvements in
efficient combustion of coal can lead to greater production of electricity per unit of coal that will
effectively reduce CO emission per unit of electricity. Although the current per capita carbon dioxide
(CO) emission in India is only one quarter of the world average and about twenty times less than
United State’s averages, the growth rate of emissions is very high. Because of this growth, the region
is expected to soon become a major contributor of greenhouse gases, such as CO and other air
pollutants.
Sulfur dioxide emissions
The sulfur content in Indian coal is low compared to United States coal. Acid rain due to sulfur dioxide
emissions is presently not of great concern. However, increasing coal use or blending Indian coal with
imported coal of higher calorific value (further increasing electricity production) needs to be carefully
addressed through viable technological options. Average SO emissions per unit of electricity are
0.0069 Gg. Total SO emissions are estimated to be 7.33 Gg per day or 2.7 Tg per year.
Emissions of oxides of nitrogen
Oxidation of nitric oxide (NO) discharged in combustion products forms nitrogen dioxide (NO) in the
atmosphere. These oxides of nitrogen are responsible for the formation of photochemical smog. Nitric
oxide emission per unit of electricity is estimated as approximately 0.00056 Gg. Total NO emissions
are estimated to be 0.5 Gg per day and 0.185 Tg per year. Nitrogen oxides are important chemical
species in the atmosphere since they contribute to its acidity; they also act as precursor gases for the
formation of tropospheric ozone. Tropospheric ozone is a greenhouse gas responsible for global
warming and is also known to have an adverse affect on plants. NO emissions should be kept at a
minimum possible level. Lower concentrations of NO lessen the formation of tropospheric ozone even
when other precursor gases like carbon monoxide (CO) are present in higher concentrations.