Impact of Torrefaction and Alkali Pretreatment on Glucose Production From Wheat Straw

Abstract

Highlights Glucose yield from torrefied wheat straw is improved when samples are subjected to alkaline pretreatment. Torrefaction time, temperature, and alkaline treatment all impact yields. Glucose yield from torrefied material, on a “per treated gram” basis, approaches that of raw feedstock in some cases. Optimized process and plant design could make torrefied feedstock a viable option for biofuel production. Abstract. The impact of torrefaction, alkaline pretreatment, and their combination on enzymatic hydrolysis was explored in terms of their effect on glucose yield from wheat straw. Samples were ground and torrefied at varying degrees of process severity, subjected to enzymatic hydrolysis, and analyzed for glucose yield. While glucose yield from raw biomass averaged 190.1 mg per g of dry raw biomass, the yield from torrefied samples was lower, ranging from 0.0 to 63.8 mg g-1, depending on the duration and temperature of the torrefaction process. Alkaline pretreatment increased the glucose yield of raw biomass to an average of 354.9 mg g-1. The highest glucose yield of 359.1 mg glucose g-1 was achieved for samples that were pretreated with a 1% NaOH solution. Alkaline pretreatment after torrefaction but prior to hydrolysis results in glucose yields ranging from 1.2 to 318.2 mg g-1, which are higher than the yields from torrefied-only samples but lower than those of raw, alkaline pretreated samples. When measured on a “per torrefied g” basis, yields of torrefied, alkaline pretreated samples approach those of raw biomass. These results indicate that there may be potential to use torrefaction and hydrolysis together when combined with an alkaline solution pretreatment. Keywords: Alkaline Pretreatment, Enzymatic hydrolysis, Lignocellulosic waste, Torrefaction, Wheat straw.