Ethanol production from cellulosic feedstocks such as corn stover, straw and sugarcane bagasse can be summarized in four steps:
Pretreatment: The raw material is crushed and heated together with weak acid to release most of the pentose sugars (i.e. sugars with five coal atoms) from the hemicellulose fraction of the biomass. This is known as hydrothermal pretreatment.
Hydrolysis: Water and enzymes are added to release the rest of the pentose sugars from the hemicellulose and most of the hexose sugars (i.e. sugars with six coal atoms) from the cellulose fraction of the biomass. This is known as enzymatic hydrolysis.
Fermentation : The now free sugar molecules are fermented into ethanol with a genetically modified yeast such as Taurus Energy’s XyloFerm®, which ferments both glucose (hexose) and xylose (pentose). Taurus’ technology can for instance increase the ethanol yield from the corn crop by up to 40 % by also utilizing the hemicellulose fraction of the plant.
Distillation : The fermented solution is distilled to purify and concentrate the produced ethanol.