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Biomass Conversion to Biofuel and Biobased Product


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Samir Khanal, Professor of Biological Engineering Molecular Biosciences and Bioengineering at UHM, describes an integrated approach in converting biomass into biofuel and biobased products. Slides from the REIS seminar series at the University of Hawaii at Manoa on 2009-10-22.

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Biomass Conversion to Biofuel and Biobased Product

  1. 1. Samir K. Khanal, Ph.D., P.E. Assistant Professor of Bioengineering Dept. of Molecular Biosciences and Bioengineering University of Hawai’i at Mānoa October 22, 2009
  2. 2. Presentation Outline  Background  Cellulosic-ethanol with ultrasound pretreatment  Fungal fermentation of biomass to ethanol  Biofuel residues for fish feed production  Syngas fermentation to ethanol
  3. 3. Why is “Biorenewables” so Important?  Provide biofuels and biobased chemicals  Improve environmental quality  Improve national security  Contribute to sustainable development
  4. 4. What is Biomass?  Agricultural crops and residues, forestry residues, energy crops, municipal wastes and other organic waste materials.  Bana grass and guinea is a high yield energy crop readily available in Hawaii. (Yield: 45 to 100 Mg/ha-yr)
  5. 5. Cellulosic Biomass to Ethanol US Biomass Resource Potential Total resources 1366 Agricultural resources 998 Forest resources 368 0 500 1000 1500 Million dry ton per year Source: USDA and USDOE, Apr 2005
  6. 6. Cellulosic Biomass to Ethanol Gasoline (B gals) Ethanol equivalent (B gals) US consumption, 2004 139 200 60% from imports 83 120 30% displacemnt 42 60 Biomass need at 80 ton/acre gal/ton 750Mton Land requirement @ 10 ton/acre 75 Macre 100 MGY biorefinery 600 each @ 160 mile2 (125 K acr)
  7. 7. Lignocellulosic Biomass Structure • Cellulose • Hemicellulose • Lignin
  8. 8. How an Engineer can Visualize! Reinforced concrete Plant cell wall material
  9. 9. Biochemical Pathway for Biofuel Production Cellulose-based ethanol Starch-based ethanol VIDEO Sugarcane-based ethanol Sugar Ferment- Ethanol Sugar Distillation Drying Cane ation Starch Corn Conversion Kernels (Cook or Stillage Enzymatic Steam Hydrolysis) Cellulose Animal Feed or Boiler Separator Cellulose Conversion Solid fuel Biogas Cellulose Pretreatment Liquid (CH4) Hydrolysis Product Stream Dryer • Crop residues: corn stover, rice straw, wheat straw, bagasse etc. Anaerobic Digester • Forestry residues • Heat and Power Thermochemical • Energy crops: switchgrass, poplar, • Conversion Biofuels and Biochemicals Miscanthus, many others
  10. 10. Biochemical Conversion Feedstock Variation Enzyme Cost Enzyme Feedstock Quality Feedstock Cost Production HSF (Hybrid Saccharification & Fermentation) Co- Enzymatic fermentation Product Pretreatment Conditioning Products Hydrolysis of C5 & C6 Recovery Sugars Sugar Losses Glucose Yield Xylose Yield Xylose Degradation Solids Loading Residue Processing Solids Loading Reactor Costs Ethanol Yields Ethanol Concentration Rate Hydrolyzate Toxicity By-products NREL. 2007. Biochemical Ethanol Process and Barriers. 30by30
  11. 11. Why Pretreatment is Needed? Pretreatment is essential to facilitate easy access of enzymes to cellulose/hemi-cellulose: 1. To solubilize lignin. 2. To dissolve hemi- cellulose. 3. To disrupt a cellulose- hemi-cellulose-lignin interaction.
  12. 12. Enzyme hydrolysis of pretreated lignocellulosic biomass (animation) Enzyme Lignocellulosic G: Glucose biomass Lignin Hemicell ulose SEM (corn stover) Pretreatment CBH1 from T. reesei (from NREL) G Hydrolysis G G G G G G G G G
  13. 13. Biomass Pretreatment Alkaline or  Ultrasound pretreatment  increase in pore volume  30 to 500oA  Reduce crystalline structure of cellulose  Reduce the enzyme loading and improve the rate of reaction  Enhance sugar release  subsequent ethanol yield/ton of biomass
  14. 14. Ammonia Pretreatment of Switchgrass Ammonia Cellulase Washing Sonication Switchgrass treatment enzyme (with DI water) (30 and 90 µm) (40 g) 1:1.5 (29.6%) 24hr incub. Reducing sugar Cellulose: 45% Hemicellulose: 31.4% Lignin: 12% Hydrolysate HYDROLYSATE AT DAY 4 Weight Loss : 13.5%
  15. 15. Effect of Sonication on Microstructure Control Ultrasound treatment: 40 sec
  16. 16. Change in Microstructure Control Ultrasound treatment: 40 sec
  17. 17. Reducing Sugar Release
  18. 18. Fungal Fermentation of Biomass to Ethanol Brown rot fungi Yeast Lignocellulose Sugar-rich Ethanol liquor Cellulose & hemicellulose Sugar-rich liquor White rot fungi
  19. 19. Experimental Steps  Corn fiber (cellulose 16.5%, hemicellulose 45%, lignin ~ 1.5%, 37% others – protein, oil, ash etc.) Addition of Enzyme Anaerobic Corn fiber fungal Induction Incubation Ethanol determination (25 g) mycelia (2 days) (with yeast)
  20. 20. White rot Brown rot Soft rot (Phanerochaete (Gloeophyllum (Trichoderma chrysosporium) reesei) trabeum) Trained cormorants with neckrings led to the submergence of the culture idea Inside an incubator (37oC) during anaerobic incubation. Each bottle contained 25 gram corn fiber, 650ml of respective fungal pellets, 150 ml of yeast media without glucose and 2ml of yeast cells (S. cerevisiae)
  21. 21. SSF with white and brown rot fungi converted ~ 9 % of fiber to ethanol on weight basis SSF with T. reesei converted only ~ 5 % of fiber to ethanol on weight basis
  22. 22. Summary • Ultrasound pretreatment resulted a significant disintegration of cellulosic micro-fibrils • Following sonication of switchgrass, reducing sugar yield improved by 70% with respect to control • Fungal process was able to hydrolyze cellulosic biomass • Over 10% of the corn fiber was converted to ethanol through fungal fermentation alone
  23. 23. Fungal Fermentation  Source of protein for animals, even for humans.  Fungi prefer acidic condition (pH 4.0).  High in lysine, 5.5% (DDGS 0.62%, soybean meal 3.0%) → co-fed with DDG to non-ruminants.  Source of valuable fungal byproducts such as enzymes, chitin/chitosan, and lactic acids.  Easy recovery of fungal biomass with high quality water for reuse.
  24. 24. Fungal Species of Interest
  25. 25. Selection of Fungi Kingdom: Fungi Phylum: Zygomycota Order: Mucorales Family: Mucoraceae Genus: Rhizopus Species: microsporus 50 µm
  26. 26. Vinasse Characteristics Parameters Molasses Sugarcane juice vinasse vinasse pH 3.85 ± 0.00 3.88 ± 0.01 Chemical oxygen demand (g/l) 86.52 ± 5.32 86.79 ± 7.38 Soluble chemical oxygen demand 63.95 ± 4.84 68.35 ± 1.48 (g/l) Total solids (%) 5.12 ± 0.00 2.46 ± 0.04 Suspended solids (%) 1.25 ± 0.10 0.59 ± 0.02 Volatile solids (%) 3.55 ± 0.00 1.77 ± 0.02 Volatile suspended solids (%) 1.07 ± 0.06 0.53 ± 0.02 Total Kejdahl nitrogen (mg/l) 1088.36 ± 10.65 336.72 ± 4.61 Potassium (mg/l) 5598.00 ± 48.65 1533.33 ± 152.75
  27. 27. Some Findings Rhizopus oligosporus could directly utilize vinasses from both molasses and sugarcane juice fermentations as substrates for its growth without any treatment or nutrient supplementation. The optimal pH for fungal biomass production is 5. Fungal biomass yields of 0.61 and 0.60 (g fungal biomass increase/g fungal biomass initial) were obtained from growing fungus on molasses vinasse and sugarcane juice vinasse, respectively. SCOD removal of about 20 and 50% were obtained from effluents after harvesting fungal biomass from molasses vinasse and sugarcane juice vinasse, respectively.
  28. 28. Fungal Pellets
  29. 29. Draft-tube Batch Experiments Aeration on Aeration off → Floating mycelial pellets
  30. 30. Dried Fungal Biomass Sugarcane juice vinasse YM medium Molasses vinasse
  31. 31. Cellulose -Ethanol: Syngas Fermentation Lignocellulosic biomass - 40–50% cellulose, 20–40% hemicellulose and 10–20% lignin - can yield 60 billion gallons of fuel-grade ethanol per year in the US • Acid/enzyme hydrolysis of • Convert all the biomass to cellulose/hemicellulose to syngas (H2+CO) hexose/pentose • Ethanol fermentation from • Ethanol fermentation from syngas hexose/pentose • Gas/liquid mass transfer • High cost of pretreatment limitation due to poor and enzyme solubility of CO and H2 • Leaving lignin for disposal • Inhibitory acetic acid as by- product
  32. 32. 33 Mesoporous Silica (MPS) functionalized by amine group •Parallel structure of silica having homogenous mesoporous (2-50 nm) pores → high area-to-mass ratio and accessibility •Permanent bonding of amine on the silica structure → Selective adsorption of acetic acid (-NH3+…Ac-) → Regenerable by pH control R=-(CH2)3NH2 or –(CH2)3NH(CH2)2NH(CH2)2NH2
  33. 33. Some Issues with Biofuels • Potential impact on food/feed supplies due to land use. • Possible increase in agricultural products prices (due to biofuel feedstocks production). • Likely to impact biodiversity. • Degradation of soil quality/soil erosion. • Increased use of fertilizer and pesticides. • May impact water quality and quantity.
  34. 34. Acknowledgements  Graduate students: Prachand Shrestha, Mary Rasmussen ConocoPhillips  USDA and UDDOE ADM  P&G
  35. 35. Books Biofuel and Bioenergy from Biowastes and Biomass Samir K. khanal (lead editor) American Society of Civil Engineers
  36. 36. THANK YOU