The use of sweet sorghum fiber as feedstock for lignocellulosic biofuel production in the southeastern United States

Commercialization of lignocellulosic biorefining for fuels and chemicals requires a locally sourced biomass feedstock which is sustainably grown and economically refined. Sweet sorghum (Sorghum bicolour (L.) Moench) holds great potential to deliver these needs for the southeastern United States. Sustainable farming of sweet sorghum is a proven practice in this particular region. A dilute phosphoric acid steam explosion pretreatment, and subsequent enzymatic hydrolysis using Novozyme® Cellic CTec2, proved to be effective with several strains of sweet sorghum grown in Citra, FL. Pretreatment consisted of a 0.5% phosphoric acid soak, followed by 5 min at 190 °C. The enzymatic hydrolysis was carried out using a solids loading equal to 10% (w/v), an enzyme loading equal to 10% of the solids (v/w), and a 24 h reaction time at 50 °C and pH 5.0. Fourteen separate genotypes were tested, and the yield of total sugars released after pretreatment (1) and enzymatic hydrolysis (2) were found to be on average 12.5% (1) and 57% (2) per unit biomass, with maximum values of 16% and 74% respectively. These results correlate to a yield potentially exceeding 80 gal/dry ton. The high yields from a relatively simple process demonstrate the potential of using sweet sorghum as feedstock for a lignocellulosic biorefinery.