Evaluation of Sweet Sorghum for Fermentable Sugar Production Potential¹

Abstract

This study was prompted by the special interest in sugar crops, at a time of high petroleum prices and fuel shortages, as potential renewable resources which would supplement non‐renewable fossil resources. Four to six sweet sorghum [Sorghum bicolor (L.) Moench] cultivars were evaluated 4 yr for fermentable sugar production potential at eight locations in the continental USA and at one location in Hawaii. Latitudes represented ranged from 21 to 47° N with the average number of frost‐free days ranging from 120 to more than 350. Data were collected for biomass yield, percent lignin, percent cellulose, stalk sugar yields, and other agronomic characters. Total sugar yield for the continental USA ranged from 4 Mg ha‐1 to 10.7 Mg ha‐1 during 3 yr of the study and up to 12 Mg ha‐1 at the Hawaiian location. Accordingly, theoretical ethanol production in the continental USA ranged from 2129 L ha‐1 to 5696 L ha‐1. Results of the study demonstrated that sweet sorghum is far more widely adapted than was anticipated for a plant of tropical origin and certainly has the potential for providing a good source of fermentable carbohydrates across a wide geographic area.

Sorghum as a Multifunctional Crop for the Production of Fuel Ethanol: Current Status and Future Trends

“…The first group with a high content of sucrose (sugary type) and the second with more monosaccharides (glucose and fructose) compared to other soluble carbohydrates (syrup type). Smith et al (1987) in their evaluation of six sweet sorghum varieties throughout four years in nine different locations did not find significant differences in sugar content or composition. The typical composition indicates that around 70% was sucrose and the rest glucose and fructose in equal parts.…”

“…Woods (2000) reported for sweet sorghum cultivars (Keller, Wray and H173) an average of 7, 10 and 4 ton of fermentable sugars/ha respectively, significantly lower compared to the 17 ton/ha for sugarcane indicated by the same author. The varieties studied by Davila-Gomez et al (2011) yielded an average of 1.85 to 2.03 ton of sugar/ha, whereas Smith et al (1987) in a extensive study performed in several locations of continental United States and Hawaii, obtained from 4.5 to 10.6 ton/ha. In other varieties evaluated in China, the best yields reached 18 ton/ha (Zhang et al, 2010).…”

Sweet Sorghum as a Bioenergy Crop for the US Great Plains

“…Total sugar yield was 4.0 to 10.7 Mg ha -1 for several locations across the continental USA and up to 12 Mg ha -1 for Hawaii U.S.A. (Smith et al, 1987), equivalent to ethanol yields of 2129 to 5696 L ha -1 and comparable to ethanol yields with maize grain. Higher yields were reported for Florida U.S.A., ranging up to 17 Mg ha -1 (Vermerris et al, 2008).…”

Effect of Planting Date and Density on Insect Pests of Sweet Sorghum Grown for Biofuel in Southern Florida

“…Sugar yield (Mg ha -1 ) was calculated using the formula: FW ؋ %JE x Brix ؋ 0.75; where FW = fresh weight (Mg ha -1 ) of 4-m samples and % JE = percentage juice extraction. Potential ethanol yield (liter ha -1 ) was calculated based on the assumptions that 1.49 kg of sugar could produce 1 liter of ethanol and a 95% sugar-to-ethanol conversion efficiency (Smith et al 1987). …”

“…Sugarcane is a major crop in southern Florida produced on 160,660 ha in 2011 . Similar to sugarcane, the juice from harvested sweet sorghum stalks can be converted into ethanol using currently available, conventional fermentation technology (Smith et al 1987). Compared to sugarcane, sweet sorghum has advantages of shorter growing period, greater water-use efficiency and wider adaptability (Reddy et al 2005).…”