Bioethanol is an example of plants being used for what function?

The principle fuel used as a petrol substitute for road transport vehicles is bioethanol. Bioethanol fuel is mainly produced by the sugar fermentation process, although it can also be manufactured by the chemical process of reacting ethylene with steam.

Basically, a plant can be considered as bioethanol becacuse it is a sugar fuel for animals. Animals consume plants for fuel to survive.