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How does using energy create carbon emissions?

We convert the energy stored in fuels such as gasoline, natural gas and coal to heat our buildings, power equipment, light up spaces and move our vehicles. Applying heat to fuels ignites a chemical reaction in which carbon dioxide (CO₂) is the by-product.

How is it, that when you use a litre of gasoline, weighing 750 g, you get 2300 g of CO₂?

Gasoline is made up of both carbon and hydrogen atoms. When gasoline is ignited, energy is released, which we convert to mechanical energy for moving a vehicle. The hydrogen (H) atoms combine with oxygen to produce water (H₂O). The carbon (C) atoms combine with oxygen (O₂) to form carbon dioxide (CO₂).

The additional weight of CO₂ comes from the oxygen combining with carbon.

What is the chemical reaction from using gasoline?

Combusting a hydrocarbon fuel like gasoline (or coal or natural gas) looks like this:

Fuel (Cx Hy) + oxygen (O₂) + spark → heat + water (H₂O) + carbon dioxide (CO₂).

In producing carbon dioxide (C + O₂ → CO₂), carbon has an atomic weight of 12. Oxygen has an atomic weight of 16. When they combine, CO₂ has a molecular weight of 44 (1 carbon atom [12] + 2 oxygen atoms [2 x 16 = 32]).

This makes CO₂ 3.67 times more heavy than carbon (44 ÷ 12 = 3.67).

That is how one litre of gasoline, weighing 750 g (and containing about 630 g of carbon), produces about 2300 g of CO₂ (3.67 × 630 g = 2300 g).

How much CO₂ is produced by using 1 kg of coal?

The same basic principle applies to using coal as to using gasoline. When coal is burned, carbon and hydrogen are released to combine with oxygen to form carbon dioxide and water. The amount of CO₂ produced depends on how much carbon is in the coal.

Anthracite coal averages about 90% carbon. Since 90% of 1 kg is 900 g, there are about 900 g of carbon atoms in 1 kilo of anthracite coal. Each carbon atom joins with two oxygen atoms to form CO₂ (C + O₂ → CO₂). As noted in our gasoline example, CO₂ is 3.67 times heavier than carbon. So, we multiply 900 by 3.67 = 3300 g of carbon dioxide. Burning 1 kg of anthracite will produce about 3.3 kg of CO2.

Bituminous coal, on the other hand, has an average carbon content of approximately 66%. Since 66% of 1 kg is 660 g, there are about 660 g of carbon atoms in 1 kilo of bituminous coal. Multiplying 660 by 3.67 gives us 2420. Burning 1 kg of bituminous coal will produce 2.42 kg of carbon dioxide.

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