(396e) Fractionation of Corn Stover Using Aqueous Ammonia and Hot Water

Two-stage fractionation of biomass using hot water and aqueous ammonia was previously developed to improve overall biomass utilization. One of the problems encountered in this process is that xylan stream recovered from the first stage is significantly contaminated by solubilized lignin (~40% removal), which complicates xylan recovery in the downstream processing. Advanced technologies are needed to significantly increase the purities of separated components to level that will support economically viable biomass processing.

The ?three-stage fractionation process using hot-water and aqueous ammonia? was devised to solve this problem in our laboratory. The three-stage fractionation process consists of (1) low-molecular weight lignin separation using aqueous ammonia at low severity; (2) hemicellulose separation using hot-water at high severity; and (3) high-molecular weight lignin separation using aqueous ammonia at high severity.

In this method, the ammonia steeping (SAA: soaking in aqueous ammonia) at moderate temperature method is introduced to remove lower molecular lignin prior to hot-water hemicellulose extraction step. It removes lignin (50-70%) significantly in the first stage and remains most of hemicellulose (>80%) in the solids so that hot water treatment can produce uncontaminated hemicellulose hydrolysates from the remaining hemicellulose-rich solids in the second stage.

The optimal process conditions that achieve highest degree of fractionation were explored. The enzymatic digestibility tests were performed for the cellulose fractionated from corn stover. Other technical aspects pertinent to development of a three-stage pretreatment process are presented.