Cellulose Chemistry and Technology

The objective of this project is to develop a process for the parallel production of ethanol and cellulose in a pulp mill, by applying a prehydrolysis step to softwood chips to extract hexose sugars for their subsequent fermentation in ethanol. Two kinds of pretreatments were compared, an acid hydrolysis and a two-step treatment composed of an autohydrolysis and a post-hydrolysis of the resulting hydrolysate. The two-step treatment allowed the limitation of the sugar degradation and subsequently the production of the inhibitors (furfural and hydroxymethylfurfural). The amount of acetic acid was however stable, compared to the amount of monomers in solution. The effects of inhibitors, such as acetic acid, HMF and furfural, on fermentation were studied. At low concentrations, they had no detrimental effect when they were added individually and only a minor effect when they were added together. At high concentrations, acetic acid had a significant negative impact on ethanol production, whereas furfural and HMF did not impact ethanol production.