When fossil fuels undergo combustion (burning) they release energy. This is useful for things like heating our homes, powering our cars, and generating electricity. However, the combustion of fossil fuels also creates pollution and contributes to global warming.
There are two types of combustion that can take place with hydrocarbons: complete and incomplete.
Most fuels contain carbon and hydrogen, and during combustion, they react with oxygen.
This type of combustion, where all the fuel burns and fully reacts with oxygen, is called complete combustion. During the complete combustion of hydrocarbon fuels, only carbon dioxide and water are produced. Therefore, if carbon dioxide forms, we can tell that complete combustion has taken place.
For example, let’s look at the combustion of methane, a hydrocarbon found in natural gas:
Methane + Oxygen → Carbon dioxide + Water
CH4 + 2O2 → CO2 + 2H2O
As you can see, the carbon and hydrogen atoms in methane combine with oxygen to form carbon dioxide and water. However, there needs to be enough oxygen present for complete combustion to take place.
Incomplete combustion is another process that can occur when hydrocarbons burn. This process takes place when there isn’t enough oxygen available for complete combustion to occur. Incomplete combustion forms carbon monoxide (CO) and water.
Methane + Oxygen → Carbon monoxide + Water
2CH4 + 3O2 → 2CO + 4H2O
However, incomplete combustion can also produce particulate carbon, also known as soot.
Methane + Oxygen → Carbon + Water
CH4 + O2 → C + 2H2O
Carbon monoxide is a colourless, odourless and tasteless gas, which makes it quite hard to detect. It is very toxic and often called the “silent killer”. However, it can be detected by carbon monoxide detectors.
When we inhale carbon monoxide, it binds to haemoglobin in the blood. This reduces the oxygen carrying capacity of red blood cells in our body.
If the cells around the body do not get a sufficient amount of oxygen, this can cause death.
Soot is made up of small carbon particles and is produced when hydrocarbons are burned incompletely. Soot can cause respiratory problems when inhaled, and it can also contribute to global dimming.