| abstract |
A process for hydrolyzing lignocellulosic biomass includes feeding lignocellulosic biomass into a pretreatment reactor, wherein the pretreatment reactor has a headspace charged with sulfur dioxide previously used in the pretreatment of lignocellulosic biomass. In addition, acid comprising sulfur dioxide and/or sulfurous acid is fed into the pretreatment reactor (e.g., with the lignocellulosic biomass, separate from the lignocellulosic biomass, or a combination thereof) and the lignocellulosic biomass is heated. As the pretreated lignocellulosic biomass is discharged from the pretreatment reactor, at least a portion of the sulfur dioxide used in the pretreatment is retained in the headspace. |