Coal: Black gold or poison?

In recent times, western nations have tried to reduce their dependence on coal although reports indicate India’s dependence on the fossil fuel will rise in the next five years.

Published: 28th April 2017 08:31 PM  |   Last Updated: 28th April 2017 08:32 PM   |  A+A-

A coal yard (File photo | Reuters)

By Express News Service

Britain’s decision to do without coal-based power for a full day shows how countries are increasingly avoiding the fossil fuel that generates huge amount of poisonous gases. So, how bad are the effects?

On Saturday, Britain marked its first full day without using coal-generated power since the Industrial Revolution more than 100 years ago. 

According to the UK's National Grid, the milestone was a "watershed" moment as part of the country's plans to phase out the last coal plants by 2025 in order to cut carbon emissions. Friday is thought to be the first time the country has not used coal to generate electricity since the world's first centralised public coal-fired generator opened in 1882 at Holborn Viaduct in London.
A good part of the coal produced across the world is used directly or indirectly in the generation of electricity. For example, according to the United States Energy Information Administration, the electric power sector accounted for about 91% of the total US consumption.

Indeed, renewable sources of energy are increasingly being used to generate power but it will be a long time before the world could entirely depend upon them for electricity needs. 

Coal is not the best of the environment-friendly sources of energy. Burning the fuel releases harmful gases like Nitrogen oxides, Sulphur dioxide, carbon dioxide, among other gases. In recent times, western nations have tried to reduce their dependence on coal although reports indicate India’s dependence on the fossil fuel will rise in the next five years. 

This brings to light the negative effects of using coal for electricity generation. Here’s a look at some facts and figures that show how the fuel is used to generate electricity and what are the negative effects of using it in electricity generation. 

How is coal converted to electricity?

Steam coal, also known as thermal coal, is used in power stations to generate electricity. Coal is first milled to a fine powder, which increases the surface area and allows it to burn more quickly. In these pulverised coal combustion (PCC) systems, the powdered coal is blown into the combustion chamber of a boiler where it is burnt at high temperature. The hot gases and heat energy produced converts water – in tubes lining the boiler – into steam.

The high pressure steam is passed into a turbine containing thousands of propeller-like blades. The steam pushes these blades causing the turbine shaft to rotate at high speed. A generator is mounted at one end of the turbine shaft and consists of carefully wound wire coils. Electricity is generated when these are rapidly rotated in a strong magnetic field. After passing through the turbine, the steam is condensed and returned to the boiler to be heated once again.

The electricity generated is transformed into the higher voltages (up to 400,000 volts) used for economic, efficient transmission via power line grids. When it nears the point of consumption, such as our homes, the electricity is transformed down to the safer 100-250 voltage systems used in the domestic market.


The side effects of a coal plant

A 500 megawatt coal plant produces 3.5 billion kilowatt-hours per year, enough to power a city of about 140,000 people. It burns 1,430,000 tons of coal, uses 2.2 billion gallons of water and 146,000 tons of limestone. However, it also puts out the following each year:

—10,000 tons of sulphur dioxide: Main cause of acid rain, which damages forests, lakes and buildings.

—10,200 tons of nitrogen oxide: Major cause of smog, and also a cause of acid rain.

—3.7 million tons of carbon dioxide: Main greenhouse gas and a leading cause of global warming. 

—500 tons of small particles: Cause lung damage. 

—220 tons of hydrocarbons: When hydrocarbons don't burn completely, they are released into the air and are a cause of smog.

—720 tons of carbon monoxide: A poisonous gas and contributor to global warming.

—125,000 tons of ash and 193,000 tons of sludge from the smokestack scrubber: A scrubber uses powdered limestone and water to remove pollution from the plant's exhaust. Instead of going into the air, the pollution goes into a landfill or into products like concrete and drywall. This ash and sludge consists of coal ash, limestone, and many pollutants, such as toxic metals like lead and mercury.

—225 pounds of arsenic, 114 pounds of lead, 4 pounds of cadmium, and many other toxic heavy metals: Mercury emissions from coal plants are suspected of contaminating lakes and rivers in northern and northeast states and Canada. Health officials warn against eating fish caught in these waters, since mercury can cause birth defects, brain damage and other ailments. Acid rain also causes mercury poisoning by leaching mercury from rocks and making it available in a form that can be taken up by organisms.

—Trace elements of uranium: A study by DOE's Oak Ridge National Lab found that radioactive emissions from coal combustion are greater than those from nuclear power production.



How is coal formed?

Coal is formed by ancient plants and animals accumulating in moist peat bogs over thousands of years. As plants die off in a wet area, they pile up into peat. This process happens best in river deltas or coastal plains. Over time, these peat seams are compressed by further deposits and the carbon content of the coal is concentrated. The older the coal gets, generally, the harder and blacker it gets. 

What are the types of coal?

There are four "ranks" of coal: lignite, sub-bituminous, bituminous, and anthracite, from lowest to highest.

How is coal burned in power plants?

Coal is broken down into a powdery form. The pulverized coal is blown into the furnace where it burns while airborne.

How much electricity generation is dependent on coal?

Coal accounts for more than 40% of power generation across the world. In India, over 60% of the energy requirement is met through this fuel. It is believed that the available coal reserves in the country might be sufficient to meet the needs for the next 100 years or so.

Which countries are the largest exporters of coal?

Australia is the largest exporter of coal at 36% of the world’s total exports. It is followed by Indonesia at 20.8% and Russia at 11.7%.



Top coal producers in the world

Country   Coal Production (in MT)
China     3,538
United States 820
India 764
Australia 471
Indonesia   387
Russia 349
South Africa        248
Germany              186
Poland              136
Kazakhstan              107
Colombia   86
Canada            62


Top coal consumers in the world

Country        Coal Production (in MT)
China                3,732
India 990
United States 730
Germany    232
Russia 207
Japan 190
South Africa 179
Poland 131
South Korea 130
Australia 118
Kazakhstan 87

Year 2015

Source: Enerdata



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