Production of bioethanol from lignocellulosic raw materials (second generation bioethanol, i.e., from non-food sources) normally comprises the process steps illustrated in the block diagram. Valmet provides solutions and equipment for the blocks marked in green.
Separation of the hydrolyzate after the prehydrolysis is applied when the sugars from the hemicellulose part of the biomass are treated separately from the glucose from cellulose.
Other versions of processes for 2G bioethanol production there is no separation of the hydrolyzate (liquor) from the prehydrolysis, instead the whole stream is sent to enzymatic hydrolysis where the carbohydrates are
converted to mono sugars in the solution. This process is called liquefaction.
Degradation of polysaccharides into mono sugars by enzymes can also be combined with fermentation to ethanol so
that saccharification and fermentation take place in the same vessel.