Ethanol production from residual lignocellulosic fibers generated through the steam treatment of whole sorghum biomass.

Cellulosic ethanol could play a major role in the upcoming circular-economy once the process complexity, low carbohydrate extraction yields and high costs are resolved. To this purpose, different steam-treatment severity factors were employed on whole sweet sorghum biomass, followed by the delignification and hydrolysis of resulted lignocellulose fibers. A modified ASTM International (American Society for Testing and Material) standard cellulose hydrolysis approach as well as a newly developed SACH (Sulfuric Acid Cellulose Hydrolysis) process were used, recovering up to 24.3 wt% of cellulosic carbohydrates. This amounted to a total extractable and constitutive carbohydrate recovery of 51.7 wt% (dry basis) when a mild steam-treatment of whole sorghum biomass and the SACH cellulose hydrolysis were employed. An ethanol potential of 6378 L/ha/year was determined, comparable to values obtained from biomass such as sugarcane in warmer climates, supporting thus the opportunity of implementing this novel approach on a wider scale.

Two-Step Thermochemical Cellulose Hydrolysis With Partial Neutralization for Glucose Production.

Cellulose hydrolysis processes using concentrated acid usually involve two steps in order to obtain high glucose yields. The first step (pre-treatment) decrystallizes cellulose while the second step (post-hydrolysis) converts the amorphous cellulose to glucose. The two-step process developed by the Industrial Research Chair on Cellulosic Ethanol and Biocommodities and its industrial partner CRB Innovations Inc., includes an intermediate partial neutralization step, whose purpose is to decrease the amount of dilution water to be added for post-hydrolysis thus minimizing handling costs. In this work, the effect of several operating parameters on the glucose yield of this process was investigated using triticale cellulose and the best conditions yielding fermentable glucose (close to 100%) were determined. These conditions involve pre-treating cellulose at 30°C using 72 wt% H2SO4 with a H2SO4/dry cellulose mass ratio of 36 over 2 h, followed by a partial neutralization using 20 wt% NaOH at an H+/OH- molar ratio of 2.3-2.5 and a post-hydrolysis at 121°C for 10 min. HIGHLIGHTS Influence of operating parameters on the glucose yield have been investigated.Conditions for producing cellulosic glucose with yields close to 100% have been identified.

A novel hybrid first and second generation hemicellulosic bioethanol production process through steam treatment of dried sorghum biomass.

Sweet sorghum was subjected to an impregnation step, which recovered most of the 1st generation sugars, prior to a steam-treatment extraction of the 2nd generation sugars, at three different severity factors (SF). A medium severity (3.56 SF) treatment proved to be an optimal compromise between the amount of sugars extracted and the fermentation inhibitors generated following the subsequent depolymerization approaches applied on the broth. Next, a series of detoxification approaches (ozonation, overliming and a combination of both) were investigated following a concentration and depolymerization step. Results show that higher steam-treatment severity required more intense detoxification steps. However, when combining the 1st and 2nd generation streams at a 2:1 ratio, the inhibitors did not affect the fermentation process and ethanol yields above 90% of the theoretical maximum were achieved.