12-11-2012, 04:07 PM
Carbon dioxide emissions from coal based power generation in India
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Abstract
Coal is the major fossil fuel used in industrial units and power plants for power generation in India. The
carbon dioxide emitted as a product of combustion of coal (fossil fuels) is currently responsible for over
60% of the enhanced greenhouse effect. The present communication is an attempt to provide a brief investigation
of CO2 emission from coal based power generation in India. Energy indicators, trends in energy
consumption and carbon dioxide emissions have been thoroughly investigated. Methodology for analysis
of carbon emissions and possible sinks is also provided.
Introduction
Energy is the basic component for development of industry, public service and transport. It is
the prime mover of economic growth and development. Throughout the history of the human
race, major advances in civilization have been accompanied by an increased consumption of energy.
Combustion converts coal into useful heat energy, but it is also a part of the process that engenders the greatest environmental and health concerns. Combustion of coal at thermal power
plants emits mainly carbon dioxide (CO2), sulphur oxides (SOx), nitrogen oxides (NOx), CFCs [1],
other trace gases and air borne inorganic particulates, such as fly ash and suspended particulate
matter (SPM). CO2, NOx and CFCs are green house gases (GHGs). CO2 produced in combustion
is perhaps not strictly a pollutant (being a natural product of all combustion), nonetheless it is of
great concern in view of its impact on global warming. Carbon dioxide is a stable molecule with
less than 10 years average residence time, i.e. 3 years in the troposphere [2], though its residence
time is over 100 years in the atmosphere, and its present concentration in the atmosphere is
increasing at an astonishing rate of 0.4% per year. The average residence time in the troposphere
means the number of years a molecule exists before it is reused by another biological process on
the earths surface or broken apart in the stratosphere.
Problems associated with CO2 increase in atmosphere
Projections by the International Energy Agency in World Energy Outlook 2000 have indicated
that global CO2 emissions would increase to 29,575 and 36,102 million tones in 2010 and
2020, respectively [7]. Fast accumulation of carbon dioxide in the atmosphere can evidently affect
the climate of earth rather quickly by warming the earth surface. This effect is associated with
the absorption of long wavelength radiation much more by CO2 than other GHGs. In particular,
the atmosphere of the northern hemisphere will be 1 C warmer because of anthropogenic
carbon dioxide when this contribution will have reached several billion tons, corresponding to a
60 ppm increase in concentration from now, such an increase could take place by the year 2010 [8].
The Intergovernmental Panel on Climate Change (IPCC) suggests that the global mean surface
temperature of the earth has increased by between 0.3 and 0.6 C since the late 19th century. Giorgi
and Hewitson [9] concluded that a doubling of CO2 would increase the temperature by 2–4 C
and decrease rainfall by 10–20% (>1 mm day1). Carbon dioxide has already risen by 30% since
the industrial era began [4].
National energy profile
The total installed capacity of the country was only 1362MW in 1947, which has increased to
over 108,000MW presently, and generation has increased from 4.1 to over 540 billion kW h during
this same period. The present installed capacity includes contributions of 76606.91MW by
thermal (coal, gas and oil), 22,000 MW by hydro, 2720MW by nuclear and the rest by biomass,
wind, etc. Electricity generation in India has doubled in the 10 years between 1988 and 1998 [11].
The total energy consumption in the country in 1998 was 12.5 quadrillion BTU, which is just 3.3%
of the world total energy consumption. Fig. 1 shows the source wise growth of power generation
since 1947 in India.
The main energy resources of India can be grouped into three broad categories, viz. commercial
(coal, oil, natural gas, hydroelectric and nuclear fuel); non-commercial (forest, dried dung cakes,
i.e. animal wastes, vegetable wastes); renewable (solar, geothermal, tidal and wind power). In
India, over 65% of the total energy consumption is met by commercial energy sources, and the
remaining 35% comes from non-commercial and renewable sources.
Energy indicators
India is one, among six, of the largest energy consumers of the world with the United States,
China, Russia, Japan and Germany. India, being the second most populated country, with a population
of 1049 billion, after China, is growing at a growth rate of 11.04% per year as observed
between 2001 and 2003 and 21% in the last decade, 1990–2000 (lower than 1980–1990, i.e.
24%). The United States requires 12,000 BTUs per dollar of GNP, while India requires 31,000
per dollar of GNP. This comparison shows that, although India is industrialising (developing)
fast, unless more efficient technologies are adopted, we will consume more energy per capita in
order to fulfill the demands of our one billion population.
Carbon dioxide emission from coal combustion
Carbon dioxide emission from combustion of coal depends on the quantity of coal consumed,
the average carbon content of the coal and a small percent of carbon that remains unoxidised,
largely as particulate matter. The high heating value (HHV) of coal (or gross calorific value,
GCV) is related to its carbon content. The GCV/HHV was calculated to be 14840.09 kJ/kg.
The fraction of carbon in coal was estimated by using the general molecular formula of coal,
i.e. C135H96O9NS. Of the total carbon burned, Marland and Rotty [20] have estimated that about
1% escapes unoxidised. Based on the input parameters and ultimate analysis of the fuel used for
power generation, the emission of carbon dioxide from thermal power plants has been computed.
The input parameters are coal consumed per annum, combustion system efficiency and carbon
content of the fuel. The combustion system efficiency has been considered equal to the average
value (26%) observed in pulverized systems.