Unit 3 - Biofuels

Liquids obtained from plants can help to lessen the amount of carbon imported to the present day from the past. Petrol can be diluted with a percentage of ethanol (an alcohol) that is made from the fermentation of plants. These plants are part of the current carbon cycle and so will not increase the overall level of carbon dioxide in our atmosphere. There are other advantages too, such as lower emissions of other gases like the toxic carbon monoxide. The main argument against this is that land that could be used for growing food crops will be taken up by crops grown to produce bioethanol to add to petrol. Diesel can be replaced with biodiesel. This is made from plant oils that have been treated to make them burn in diesel engines. Biodiesels can be made from used cooking oils, soya bean oil or even animal fats.

Biogas is made in a generator which is loaded with human waste, animal dung or food waste which would otherwise end up in the environment. Waste materials like these release methane and carbon dioxide into the atmosphere as they decay. This biofuel is mainly methane and is produced by anaerobic fermentation of the waste products. Aerobic fermentation would produce carbon dioxide instead of methane and that cannot be usefully used. Biogas can be passed through pipes to local homes where it can be used as a fuel for cooking. In some places, the biogas is used as a fuel for generating electricity for the local community.

Which biofuels are combustible liquids? Is methane a biofuel? See how much you understand about biofuels by trying this quiz.