@ Sahar, 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. The main sources of sugar required to produce ethanol come from fuel or energy crops. Ethanol burns to produce carbon dioxide and water. For more details , please go through the below article published in the journal Biotechnology and Bioengineering.
Simplified modeling of fed‐batch alcoholic fermentation of sugarcane blackstrap molasses
Attilio Converti Saleh Arni Sunao Sato João Carlos Monteiro de Carvalho Eugênio AquaroneFirst published:28 July 2003 https://doi.org/10.1002/bit.10750