1. Processing Sweet Sorghum For a Dual Feedstock Bioenergy System Dani Bellmer, Professor Biosystems & Agricultural Engineering Food and Agricultural Products Center Oklahoma State University 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) 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 Liquid Sugar Biomass Starch Huge Biofuel Potential

4. Lignocellulosic Feedstock Yield Comparison CropLocation 1 Dry Yield (Mg/ha) 2 Ethanol Yield (L/ha) Corn StoverU.S.A123516 SwitchgrassU.S.A133809 MiscanthusU.S.A174981 Mixed Prairie GrassU.S.A6.71963 Woody CropsU.S.A113223 Energy CaneU.S.A267618 Sweet Sorghum BagasseU.S.A226446 1 Source: DOE Update to the Billion Ton Sudy (2011) 2 Ethanol yield assumes that 50% of d.m. can be converted to sugars

5. Feedstock Yield Potential Sugar Biomass Large Biofuel 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 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) 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 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 Sweet Sorghum Sugar Beets Milling Diffusion

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, 80 o C), L/S ratio (0.5, 1.0, 1.5) Seydelman bowl chopper to generate 2 particle sizes Batch process to simulate counter current diffusion Tested effects of particle size, temp (60, 70, 80 o C), 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 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? Would it be more efficient to process the whole stalk, and take advantage of the starch and cellulose present? Liquid Sugar Biomass Starch

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

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 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? Thermomechanical refining is a common method of fiber development for separation of lignin, cellulose and hemicelluloses. Physical pretreatment with refiners rather than chemical treatment Thermomechanical refining 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 Processing Future 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 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 Can be used in both the sugar and cellulose arenas A dual feedstock process with sugar beets may be advantageous Liquid Sugar Biomass Starch

22. Acknowledgements Sorghum Checkoff Program South Central Sun Grant Program Robert M. Kerr Food and Agricultural Products Center 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 CropLocationCrop Yield (Mg/ha) Biofuel Yield (L/ha) MaizeU.S.A9.4Ethanol3751 SugarcaneBrazil73.5Ethanol5476 Sugar BeetGlobal46.0Ethanol5060 CassavaGlobal12.0Ethanol2070 SoybeanU.S.A.2.7Biodiesel552 Palm OilIndonesia17.8Biodiesel4092 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 Biomass Yield (t/acre) Juice Sugar Content (%) 13 15 17 25250 288326 35351404457 45451518586 Assumes.55 juice expression ratio and 90% fermentation efficiency