Planting Management Impact on Sweet Sorghum as a Biofuel Crop

Project Details

  • Kun-Jun Han
  • Louisiana State University
  • $29,890
  • Year: 2010


Project Summary

Sweet sorghum is adapted to a broad range of environmental conditions which makes it adaptable over a large part of the US. The sugar enriched stalks can produce up to 40 tons of biomass so it has attracted attention as a desirable biofuel feedstock. Corn-based ethanol production has been dominant in biofuel production. However, starch in corn grain must be broken down into a fermentable sugar. This process requires energy input and makes corn-based ethanol production less efficient than ethanol production from sweet sorghum. Although sugar concentration is lower than sugarcane, fermentable sugar composition in sweet sorghum is advantageous for immediate fermentation with lower crystallization of the sweet sorghum sugars. Recent field research with sweet sorghum varieties at LSU Agricultural Center Research Stations demonstrated the potential of sweet sorghum as a biofuel feedstock in northern and southern Louisiana. The potential for significant yield in a relatively short growing period could be advantageous since bio-refineries will require steady feedstock supplies over a long period. The southern US has a long growing season and it may be possible to more fully utilize the whole season to enhance production from sweet sorghum. Theoretically, sweet sorghum seed will germinate when soil temperature is around 64 oF and northern Louisiana soil temperature reaches that level around the second week of March. Therefore early planting in March with harvest in July may make it possible to grow another crop during the season. Sweet sorghum yield and sugar quality responses to various planting dates and possible multiple harvests have not been studied extensively. Therefore, we are proposing an integrated study combining field research and advanced sugar analysis technology. Data related to sweet sorghum parameters such as yield, maturity, stalk leaf ratio and seedhead yield will be collected at research units in both northeast and southeast Louisiana. The Audubon Sugar Institute will measure juice yield, sugar composition and ethanol production from juice, seedheads, and bagasse. Sweet sorghum will be planted at approximately 2-week intervals from mid-March to May and also in early June and July. Some plants will be harvested in the early seedhead development stage thus allowing an anticipated ratoon crop while others will be harvested only at the more traditional stage of late seed development. This growth stage is known to be one of the highest fermentable sugar accumulating stages. The total fresh yield of juice extractable stalks and days required for reaching target harvest maturity will be recorded. Sweet sorghum stems will be weighed and milled for determination of stalk and juice production per area. Sugar content will be measured and fermentable sugars (glucose, fructose, etc.) characterized and evaluated for purity. The amount of recovered bagasse will be recorded and fermented after pre-treatment. Ultimately, this information will provide an understanding of sweet sorghum growth behavior, stalk yield, fermentable sugar production and potential ethanol from a wide range of plantings throughout the growing season. Results will provide an informational base for planning a system for utilization of sweet sorghum as a biofuel crop.