10-34: Effective utilization of barley straw for furfural and ethanol production using acidified zinc chloride and fermentation

Biomass consists mainly of three major components (cellulose, hemicellulose, and lignin). In order to achieve complete utilization of biomass, each component must be separated and subsequently converted into value-added product. Fractionation methods using various chemicals have been suggested and tested. Among these, acid and alkaline solutions have been known to be effective for separation of hemicellulose and lignin, respectively.

Acidified ZnCl₂ was reported to be an effective and strong swelling agent for cellulose. Zinc chloride also has high affinity to hemicellulose component. Moreover, the hemicellulose hydrolysate with acidified ZnCl₂ solution can be converted into furfural without addition of catalyst. Furfural can be a building block chemical for the production of medicines, resins, food additives, fuel additives and other special chemicals. In addition, fractionation by acidified ZnCl₂ results in the effective pretreatment of the remaining cellulose-rich solid cake; therefore, treated solid can easily be hydrolyzed and fermented into ethanol using commercial cellulose and conventional yeast.

In this study, RSM (response surface methodology) was adopted to find the optimized fractionation conditions for maximum recovery of xylan, i.e. maximum XM (xylan + mannan) recovery yield and high purity. Several process variables including reaction temperature, ZnCl₂ concentration, and reaction time, were selected as factors of experimental design by preliminary tests. Optimal reaction conditions of these three factors were determined by central composite design (CCD). The treated solid at optimum conditions was tested for ethanol production by simultaneous saccharification and fermentation (SSF), and C5 rich hydrolyzate was tested for furfural production by thermal conversion.