Answer: Bio-fuels
Step-by-step explanation:
Bio-fuels are the alternatives of fossil fuels and are directly or indirectly obtained from the plants and other waste materials that are of biological origin. It is much cheaper than the fossil fuels.
The above mentioned crops, algae sugar and other sewage products produces ethanol, undergoing fermentation process, that are essential for making bio-fuels.
Bio-diesel and Bio-ethanol are the two usual types of bio-fuels. Bio-diesels are made up of fats and oils, commonly used to run vehicles whereas bio-ethanol is made from the fermentation of plants and other crops, that are enriched in the production of ethanol.