Abstract: A method for obtaining a concentrated alcohol solution from a lignocellulosic feedstock. The lignocellulosic feedstock is hydrolyzed to prepare a sugar solution. The sugar solution is fermented to produce a fermentation broth comprising alcohol and at least about 1 g ammonium ions/kg fermentation broth. The alcohol in the fermentation broth is then concentrated by distillation to produce an alcohol-enriched vapour. Either before distillation, during distillation or during the azeotrope breaking process, the concentration of ammonia in the alcohol-enriched vapour can be reduced by acid addition to at most about 300 ppm. The alcohol in the alcohol-rich vapour is then further concentrated by an azeotrope breaking process to provide the concentrated alcohol solution.

Abstract: A method for obtaining a concentrated alcohol solution from a lignocellulosic feedstock. The lignocellulosic feedstock is hydrolyzed to prepare a sugar solution. The sugar solution is fermented to produce a fermentation broth comprising alcohol and at least about 1 g ammonium ions/kg fermentation broth. The alcohol in the fermentation broth is then concentrated by distillation to produce an alcohol-enriched vapour. Either before distillation, during distillation or during the azeotrope breaking process, the concentration of ammonia in the alcohol-enriched vapour can be reduced by acid addition to at most about 300 ppm. The alcohol in the alcohol-rich vapour is then further concentrated by an azeotrope breaking process to provide the concentrated alcohol solution.