Sweet Sorghum Ethanol: In-Field Fermentation Issues

1. Sweet Sorghum Ethanol: In-Field Fermentation Issues Dani Bellmer1, Ray Huhnke2 1Assoc. Professor, Biosystems Engineering & Food and Agricultural Products Center 2Professor, Biosystems Engineering Oklahoma State University

2. In the US, we currently import over 60% of our petroleum needs

3. Current U.S. Ethanol Production Facilities 117 operational, 57 under construction

4. Sweet Sorghum Has Great Potential as an Energy Crop • Can be grown in temperate climates • “More Crop Per Drop” - Low irrigation needs (1/2 corn and 1/3 sugarcane) • Drought tolerant • 12-21% directly fermentable sugar (i.e. no starch to convert)

5. Heat Energy Traditional Sugar Processing On-Farm Central Facility Distillation & Dehydration Fermentation Juice Press Sugarcane Bagasse

6. In-Field Production of Ethanol from Sweet Sorghum Harvesting, pressing, & fermenting the juice in the field…

7. Field Residue Heat Energy Silage Potential In-Field Processing On-Farm Central Facility Dewatering/ Distillation Dehydration Fermentation Juice Press Sorghum Bagasse

9. Potential In-Field Storage Bladders

10. Possible System Scenario in OK • Begin planting ~ mid April • Stagger plantings April- June • Harvest July – mid-November (4.5 month harvest window) • Producers owns 1 week juice storage capacity + partial dewatering system • Final dehydration conducted at central site

11. Evaluate Sweet Sorghum Ethanol Potential in Oklahoma Goals: • Evaluate In-Field Fermentation Issues • Determine Factors Affecting Juice Extraction Efficiency • Evaluate Potential for Expanded Harvest Window

12. Fermentation

13. Theoretical Ethanol Production Stoichiometry of sugar fermentation:C6H12O6  2C2H5OH + 2CO2Theoretical Conversion: 0.51 g etoh/ g sugar

14. In-Field Fermentation

15. Ethanol Production Results

16. Ethanol Production at Different Harvest Times (1 month apart)

17. Effect of Inoculation Time on Ethanol Production

18. Effect of Leaf Stripping on Ethanol Production

19. Effect of Storage Fermentation samples after 5 months

20. Effect of Storage Fermentation samples after 5 months

21. Juice Extraction Efficiency • Compare roller press and screw press • Evaluate juice yield as affected by time of harvest • Effect of stalk diameter on juice expression

22. Small Scale Roller Press

23. Screw Press

24. Finely Chopped Bagasse Out of Screw Press

25. Screw Press vs Roller Press Juice Expression Ratio (g juice/g biomass) • Roller Press: .36 - .4 • Screw Press: .45 - .5

26. Whole Stalks in Screw Press: Effect of Pressure

27. Effect of Harvest Time on Juice Expression(Roller Press)

28. Effect of Stalk Diameter on Juice Expression Large ~ 3 cm Small ~ 1.5 cm

29. Additional Ongoing Research • Determine level of sterilization needed between fermentation cycling in storage bladders • Develop on-farm partial dewatering process • Evaluate staggered plantings to determine effect of extended harvest window

30. Three Different Planting Dates

31. Potential Ethanol Yield(gallons/acre) * Assumes 0.55 juice expression ratio and 90% conversion efficiency

32. Trade-Offs Between Processing Scenarios On-Farm Central Facility • Lower Transportation Costs • Lower Capital Costs • More Feasible in Reduced Harvest Window Scenarios • Value to Rural Economies • Higher Juice Extraction Efficiency • Higher Conversion Efficiency • Economies of Scale

33. Critical Process Questions Remaining • Best technology for in-field, single pass pressing • Determination of extent of dewatering to be completed on-farm, and best technology • Sterilization Requirements

34. The Future is Sweet…

35. Acknowledgements • OSU Collaborators: Ray Huhnke, Dimple Kundiyana, Chad Godsey, Bill Raun, Rodney Holcomb, students • Lee McClune, LeeMax Energy, Knoxville, IA • Kerr Center for Sustainable Agriculture, Poteau, OK • OK Field Research Station Superintendents • Oklahoma Food and Agricultural Products Center, Stillwater, OK

36. Sugar Content Monitoring 115 Days After Planting