Fuels - Part X

5. Pollution caused by fuels
When a fuel undergoes combustion or oxidation reaction, it produces carbon dioxide and water. In many fuels other reaction products are also emanated. These can be sulphur dioxide, carbon mono oxide, carbon or soot particles. The byproducts when mixed with air, change the balance of air that we breathe in. This results in many harmful effects to human beings and the environment. The imbalance caused in the atmospheric proportion of gases by burning of fuels is known as pollution.

Pollution caused by burning coal :  Coal contains chemicals like carbon, hydrogen, oxygen, sulphur and nitrogen. When coal burns we get carbon dioxide, carbon mono oxide, sulphur dioxide and smoke.

Carbon dioxide : When coal burns with sufficient supply of oxygen, then carbon dioxide or CO₂ is a byproduct. CO₂ is a pollutant and excess of this gas traps sun’s heat energy thereby increasing the atmospheric temperature. This is the reason CO₂ is called a greenhouse gas because this is exactly what happens in  glass house where plants are grown.

Carbon mono oxide : When coal burns with insufficient supply of oxygen, the carbon mono oxide or CO is formed. CO is a poisonous gas and is harmful to our bodies. When CO is inhaled, it creates respiratory problems, suffocation due to inadequate supply of oxygen in the blood, etc. Excess levels of CO may even cause death.

Sulphur dioxide : When coal burns, it produces sulphur dioxide or SO₂. This is a very poisonous gas. When this gas mixes with air and moisture in the air, it forms sulphuric acid. This acid may combine with rain and is called acid rain. The acid rain is corrosive and harmful to plants, crops, human beings and animal. For example, limestone or marble buildings such as the Taj Mahal is turning yellowish because of this type of pollution caused by a refinery that is in its close proximity.

Smoke : Carbon component that is not converted into either CO₂ or CO goes into the atmosphere as black smoke. This again causes air pollution. It is harmful to inhale smoke, as it will cause suffocation. Also the black smoke blackens clothes, buildings, etc.

Pollution caused by burning petroleum based products :  Vehicles run on diesel or petrol. These petroleum products contain hydrocarbons along with lead chemicals. Lead chemicals are added to make these fuels heavy and avoid knocking in vehicles. When these petroleum products burn, they emit unburned hydrocarbons, unburned carbon particles, some alcohols and acids and lead compounds. The internal combustion engines in cars and other vehicles, produce heat from petrol in a very short time. This gives rise to incomplete burning of petrol. The engine exhaust throws unburned hydrocarbons, carbon particles, carbon mono oxide along with some organic alcohols and acids in the air. The lead compound tetraethyl lead Pb(C₂H₅) added to petrol to slow down its rate of combustion  is also a very high risk pollutant. Thus the engine exhausts give off gases which are highly polluting and undesirable components in the atmosphere.

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