How does the combustion of ethanol differ from petrol?

The combustion of ethanol is cleaner than petrol, producing less harmful emissions and greenhouse gases.

Ethanol, also known as ethyl alcohol, is a renewable fuel made from various plant materials collectively known as 'biomass'. When ethanol is combusted, it reacts with oxygen to produce carbon dioxide, water, and a significant amount of energy. The chemical equation for this reaction is C2H5OH + 3O2 → 2CO2 + 3H2O. This reaction is exothermic, meaning it releases energy in the form of heat and light.

On the other hand, petrol, also known as gasoline, is a non-renewable fuel derived from crude oil. The combustion of petrol also produces carbon dioxide and water, but it also releases a number of harmful pollutants such as nitrogen oxides, sulphur dioxide, and particulate matter. These pollutants can contribute to air pollution and have harmful effects on human health.

One of the key differences between the combustion of ethanol and petrol is the amount of carbon dioxide produced. While both fuels produce carbon dioxide, a greenhouse gas, the carbon dioxide produced by ethanol combustion is part of a short-term carbon cycle. This means that the carbon dioxide released is reabsorbed by plants during photosynthesis, which are then used to produce more ethanol. This cycle helps to mitigate the impact of ethanol combustion on global warming.

In contrast, the carbon dioxide produced by petrol combustion is part of a long-term carbon cycle. The carbon in petrol was stored underground for millions of years before being released into the atmosphere, contributing to an increase in atmospheric carbon dioxide levels and global warming.

Another difference is the energy content of the two fuels. Petrol has a higher energy content than ethanol, meaning that a car running on petrol can travel further than a car running on an equivalent amount of ethanol. However, ethanol burns more cleanly than petrol, producing fewer harmful emissions and making it a more environmentally friendly fuel option.