Evaluation of Sweet Sorghum as a Feedstock by Multiple Harvests for Sustainable Bioenergy Production

Mingli Wang, Zhanguo Xin, Brandon Tonnis, Glenn Farrell, David Pinnow, Zhenbang Chen, Jerry Davis, Jianming Yu, Yen-Con Hung, Gary A. Pederson

Department of Agronomy, Kansas State University, Manhattan, USA.
Department of Crop & Soil Sciences, USDA-ARS, PSGDU, Lubbock, USA.
Department of Experimental Statistics, University of Georgia, Griffin, USA.
Department of Food Science & Technology, University of Georgia, Griffin, USA.
USDA-ARS, PGRCU, Griffin, USA.

DOI: 10.4236/jsbs.2012.24019                

Abstract

Sweet sorghum has become an important feedstock for bioethanol production. Total sugar yield and multiple harvests can directly affect ethanol production cost. Little is known about stem traits and multiple harvests that contribute to sugar yield in sweet sorghum. Stem traits were evaluated from 25 sweet and grain sorghum accessions. Stems were harvested twice at the soft-dough stage and the stems were pressed with a hydraulic press. Sugars in the stem juice were quantified by high performance liquid chromatography. Sweet sorghum produced five times more fresh stem weight and dry stem mass (830 gand164 g) than grain sorghum (150 gand27g). Sweet sorghum produced a much higher volume of juice and higher yield of sugars (366 ml and42 g) per stem than grain sorghum (70 ml and4 g). Significant variability in fresh stem weight (72 - 1837 g), juice volume (31 - 753 ml), sugar yield (3 - 81 g), dry stem mass (14 - 383 g), and sugar yield/dry stem mass ratio (0.11 - 0.53) per stem was detected among sweet sorghum accessions. Stem sugar yield was significantly correlated with stem fresh weight and juice volume. Sorghum was harvested twice within one growing season resulting in some sweet sorghum accessions producing double amount of sugars. Sweet sorghum produced three times more dry mass weight (bagasse) than fermentable sugar weight. To reduce feedstock cost, methods have to be developed for efficiently utilizing bagasse. Our results showed high fresh stem weight, high ratio of sugar yield to dry stem mass, and double harvests are prime traits to boost sugar yield. Sweet sorghum may be suitable for multiple harvests in certain regions of theU.S.TheU.S.sweet sorghum collection needs to be screened for acces- sions that can be harvested twice with an extended feedstock-production season and used as a feedstock for sustainable and renewable bioenergy production.

Keywords

Sorghum Fresh Stem Weight; Juice Volume; Sugar Yield; Dry Stem Mass; Hydraulic Press (HP); High Performance Liquid Chromatography (HPLC); Multiple Harvest; Bagasse; Sustainable Bioenergy Production

Conflicts of Interest

The authors declare no conflicts of interest.

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