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Processing Sweet Sorghum For a Dual Feedstock Bioenergy System

Processing Sweet Sorghum For a Dual Feedstock Bioenergy System. Dani Bellmer, Professor Biosystems & Agricultural Engineering Food and Agricultural Products Center Oklahoma State University. Why I Love Sweet Sorghum. Versatility Can be grown in temperate climates

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Processing Sweet Sorghum For a Dual Feedstock Bioenergy System

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  1. Processing Sweet Sorghum For a Dual Feedstock Bioenergy System Dani Bellmer, Professor Biosystems & Agricultural Engineering Food and Agricultural Products Center Oklahoma State University

  2. Why I Love Sweet Sorghum • Versatility • Can be grown in temperate climates • Adapts well to adverse environments (hot, dry, high salinity) • Relatively low input requirements • High carbohydrate production (in both the sugar & lignocellulosic fractions)

  3. Feedstock Yield Potential

  4. Lignocellulosic Feedstock Yield Comparison 1Source: DOE Update to the Billion Ton Sudy (2011) 2Ethanol yield assumes that 50% of d.m. can be converted to sugars

  5. Feedstock Yield Potential Sw. Sorghum: 3800 + 6446 10,246 L/ha

  6. Sweet Sorghum Processing Options: Scale Matters Scenario #1: 10,000 contiguous acres in a tropical climate • Use a System that Mimics Sugarcane Processing (large press roll train) Scenario #2: Smaller acreage in a temperate climate • Best Processing Options are Not So Clear

  7. Low Hanging Fruit for Biofuel Production: Immediate Uses for Sweet Sorghum Juice: • As a low-cost seasonal feedstock in existing ethanol plants • As a complementary feedstock during sugarcane processing (4-5 months when harvestable cane is not available)

  8. Considerations for the South Central U.S. • Short sorghum harvest window (3-4 months), juice is unstable • A dual feedstock system would improve process economics • Sugar beets could be alternated • Ideally, a similar process could be used for both feedstocks

  9. Sugar Beet Processing Beets are sliced into cossettes and then put through a diffuser system to extract the sugar

  10. Dual Feedstock Process Diffusion Milling Sweet Sorghum Sugar Beets

  11. Counter Current Diffusion Process

  12. Diffusion Studies with SS • Seydelman bowl chopper to generate 2 particle sizes • Batch process to simulate counter current diffusion • Tested effects of particle size, temp (60, 70, 80oC), L/S ratio (0.5, 1.0, 1.5)

  13. Simulation of Counter Current Diffusion Process in a 4-Stage Batch System

  14. Diffusion Studies

  15. Diffusion Results • Sugar extraction ranged from 45% to 91% of theoretical maximum yield • L/S Ratio had a significant effect on sugar extraction • Trend toward higher sugar extraction with fine particle size, but not significant • No significant differences with temperature

  16. Would it be more efficient to process the whole stalk, and take advantage of the starch and cellulose present? • Biomass • Liquid Sugar • Starch

  17. Proposed Dual Feedstock Process for Whole Stalks + Cellulases & Amylases Sweet Sorghum Counter Current Diffusion Process Twin Screw Press for Milling and Juice Extraction Sugar Beets

  18. Twin Screw Press • Interrupted flight design, which generates multiple stages of compression in overlapping screws, resulting in very high shearing action. • Shear forces may provide enough fiber development for either partial or complete cellulose hydrolysis • In addition, juice is extracted

  19. What can we learn from the pulp & paper industry? • Thermomechanicalrefining is a common method of fiber development for separation of lignin, cellulose and hemicelluloses. • Physical pretreatment with refiners rather than chemical treatment

  20. Whole Stalk ProcessingFuture Goals • Utilize a twin screw press for whole stalk processing and evaluate the extent of fiber pretreatment • Simultaneously hydrolyze starch and cellulose in an attempt to maximize carbohydrate production. • Evaluate the use of a mechanical refiner for stalk fiber pretreatment

  21. Sweet Sorghum Has Tremendous Untapped Potential • Can be used in both the sugar and cellulose arenas • A dual feedstock process with sugar beets may be advantageous • Biomass • Liquid Sugar • Starch

  22. Acknowledgements • Sorghum Checkoff Program • South Central Sun Grant Program • Robert M. Kerr Food and Agricultural Products Center

  23. Questions ? Thank You

  24. Sweet Sorghum Yields

  25. Energy Feedstock Yield Comparison Starch, Sugar, and Oilseeds *Source: FAO, The State of Food and Agriculture. Biofuels: Prospects Risks and Opportunities (2008)

  26. Potential Ethanol Yield (gal/acre)from Sweet Sorghum Juice Assumes .55 juice expression ratio and 90% fermentation efficiency

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