bioethanol - iowa state universityhome.eng.iastate.edu/~tge/ce421-521/sonuki-pres.pdf · 1....
TRANSCRIPT
1. Introduction
A biofuel produced by the fermentation of plants rich in sugar/starch
Bioethanol
renewable resourcesimpact on air quality due to cleaner combustion reduced net carbon dioxide (greenhouse gas) emissionsexpanded market opportunity in the agricultural fieldenergy security: less dependence on crude oilMore than 90% of the bioethanol produced in the U.S. comes from corn
2. Outline
1. Production process1. Grinding2. Cooking3. Fermentation4. Stress management5. Distillation6. Dehydration
2. Lignocellulosic biomass3. Immobilized Cell System 4. Energy Balance 5. Concerns
3. Production Process
Grain
Ethanol
1. Grinding
2. Cooking
3. Fermentation
4. Distillation
5. Dehydration
3-1. Grinding
Less energy consumptionProvide more uniform particles
Advantage
High set up costHigh maintenance costDifficult to grind small grainsDifficult to grind hard shell grains
Disadvantage
Roller mill (Kohl, 2003)
3-1. Grinding
Less set up costLess maintenance costEasier to grind small grainsEasier to grind hard shell grains
Advantage
Higher energy consumption ( about twice as much)
Provide less uniform particles
Disadvantage
Hammer mill (Kohl, 2003)
3-2. Cooking
Hot water treatment
Micro-crystalline area
Broken
Hot water85°C
20~60 min
Super heated water110°C
High pressure
3-2. Cooking
LiquefactionAttack α-1,4 linkageConvert Starch into Dextrinendoenzyme10 times faster than glucoamylase
Alpha-amylase
Starch (Kohl, 2003)
3-2. Cooking
SaccharificationexoenzymeAttack α-1,4 and α-1,6 linkageConvert Dextrin into Glucose
Glucoamylase
Dextrin (Kohl, 2003)
3-3. Fermentation
Facultative anaerobicConverts sugar into carbon dioxide and water in an aerobic environmentConverts sugar into carbon dioxide and ethanol in an anaerobic environmentPropagation tank
Yeast
S. cerevisiae
3-4. Stress management
Fermentation is exothermicCooling system is required
Temperature
Simultaneous increase in the both concentrations of sugar and ethanol should beavoidedThe simultaneous saccharification and fermentation (SSF)
Concentrations of sugar and ethanol
Byproducts produced by contaminated bacteriaLactic acid: lactobacilli bacteriaAcetic acid: acetobacter bacteriaClose control is required
Lactic acid and Acetic acid
3-5. Distillation
Distillation step (Kohl, 2004)
Multiple vaporization and concentrationIt burdens on the cost
Initial concentration of ethanol isimportant
3-6. Dehydration
Entrainer: benzene or cyclohexaneStrong intermolecular reaction between water and benzeneComplicatedToxicity problem
Azeotropic Distillation
Pore size of molecular sieves: 3 ǺEthanol: 4.4 ǺWater: 2.8 ǺHigh energy required to regenerateFlammability of superheated ethanol
Molecular sieves
4. Lignocellulosic Biomass
Agricultural residue: bagasse, wheat straw, wheat husk, wooden wastePretreatment required: solubilization of cellulose, hemicellulose, and lignin
Lignocellulosic biomass
Acid treatmentLow costHigh reaction
Alkaline treatmentBe able to remove lignin without having big effects on the other parts
Thermal treatmentSteam explosionLiquid hot water
Biological treatment
Pretreatment
5. Immobilized Cell System
(a) attachment to a surface (b) entrapment within a porous matrix(c) containment behind a barrier(d) self-agitation
Immobilization
Immobilization methods(Verbalen et al., 2006)
Provide high densityEnable high flow rate
and short time operation
Advantage
Affect on yeast: flavor, odor
Disadvantage
6. Energy Balance
2,373NANANANA31,961129.9113Average
16,19315,05682,82453,277 (HHV)2.5322,159124.5122This study (1995)
-4,00010,00090,00057,000 (LHV)NRNRNR90Ho (1989)
25,65324,95075,29746,297 (LHV)2.5531,000127.0120Morris and Ahmed (1992)
18,3248,12773,93440,105 (HHV)2.5031,135127.0119Marland and Turhollow (1991)
-8,4318,07291,12748,434 (LHV)2.5637,958135.0119Keeney and DeLuca (1992)
-33,51721,500131,01773,687 (LHV)2.5037,551136.0110Pimentel (1991)
Btu/galBtu/galBtu/galBtu/galgal/buBtu/lblb/acrebu/acre
Net energy value
Coproductsenergy credits
Total energy use
Ethanol conversion process
Corn ethanol conversion rate
Inputs for nitrogen fertilizer
Nitrogen fertilizer application rate
Corn yieldStudy/year
Energy balance of bioethanol (Shapouri et al., 1995)
Energy converted into ethanol or its coproductsminus energy used to produce ethanol
Net energy value (NEV)
6. Energy Balance
Development of technologiesCorn yieldFertilizer
EnergyApplication rate
Ethanol conversionFarm machineryCoproducts
Causes of discrepancies
8. Conclusion
Many sophisticated techniques for productionof bioethanolIts energetic efficiency and environmentalfriendliness are still controversial.