BioethanolCE 521Shinnosuke Onuki1. Introduction A biofuel produced by the fermentation of plants rich in sugar/starchBioethanol9renewable resources9impact on air quality due to cleaner combustion 9reduced net carbon dioxide (greenhouse gas) emissions9expanded market opportunity in the agricultural field9energy security: less dependence on crude oil9More than 90% of the bioethanol produced in the U.S. comes from corn1. Introduction Imports as a percentage of total U.S. crude oil supply (McMillan,1996)2. Outline1. Production process1. Grinding2. Cooking3. Fermentation4. Stress management5. Distillation6. Dehydration2. Lignocellulosic biomass3. Immobilized Cell System 4. Energy Balance 5. Concerns3. Production ProcessGrainEthanol1. Grinding2. Cooking3. Fermentation4. Distillation5. Dehydration3-1. Grinding9Less energy consumption9Provide more uniform particlesAdvantage9High set up cost9High maintenance cost9Difficult to grind small grains9Difficult to grind hard shell grainsDisadvantageRoller mill (Kohl, 2003)3-1. Grinding9Less set up cost9Less maintenance cost9Easier to grind small grains9Easier to grind hard shell grainsAdvantage9Higher energy consumption ( about twice as much)9Provide less uniform particlesDisadvantageHammer mill (Kohl, 2003)3-2. CookingHot water treatmentMicro-crystalline areaBrokenHot water85°C20~60 minSuper heated water110°CHigh pressure3-2. Cooking 9Liquefaction9Attack α-1,4 linkage9Convert Starch into Dextrin9endoenzyme910 times faster than glucoamylaseAlpha-amylaseStarch (Kohl, 2003)3-2. Cooking 9Saccharification9exoenzyme9Attack α-1,4 and α-1,6 linkage9Convert Dextrin into GlucoseGlucoamylaseDextrin (Kohl, 2003)3-3. Fermentation 9Facultative anaerobic9Converts sugar into carbon dioxide and water in an aerobic environment9Converts sugar into carbon dioxide and ethanol in an anaerobic environment9Propagation tankYeastS. cerevisiae3-4. Stress management9Fermentation is exothermic9Cooling system is requiredTemperature9Simultaneous increase in the both concentrations of sugar and ethanol should beavoided9The simultaneous saccharification and fermentation (SSF)Concentrations of sugar and ethanol9Byproducts produced by contaminated bacteria9Lactic acid: lactobacilli bacteria9Acetic acid: acetobacter bacteria9Close control is requiredLactic acid and Acetic acid3-5. Distillation Distillation step (Kohl, 2004) 9Multiple vaporization and concentrationIt burdens on the cost9Initial concentration of ethanol isimportant3-6. Dehydration 9Entrainer: benzene or cyclohexane9Strong intermolecular reaction between water and benzene9Complicated9Toxicity problemAzeotropic Distillation9Pore size of molecular sieves: 3 Ǻ9Ethanol: 4.4 Ǻ9Water: 2.8 Ǻ9High energy required to regenerate9Flammability of superheated ethanolMolecular sieves4. Lignocellulosic Biomass 9Agricultural residue: bagasse, wheat straw, wheat husk, wooden waste9Pretreatment required: solubilization of cellulose, hemicellulose, and ligninLignocellulosic biomass9Acid treatment9Low cost9High reaction9Alkaline treatment9Be able to remove lignin without having big effects on the other parts9Thermal treatment9Steam explosion9Liquid hot water 9Biological treatmentPretreatment5. Immobilized Cell System (a) attachment to a surface (b) entrapment within a porous matrix(c) containment behind a barrier(d) self-agitation ImmobilizationImmobilization methods(Verbalen et al., 2006)9 Provide high density9 Enable high flow rate and short time operationAdvantage9 Affect on yeast: flavor, odorDisadvantage6. Energy Balance 2,373NANANANA31,961129.9113Average16,19315,05682,82453,277 (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/acreNet energy valueCoproductsenergy creditsTotal energy useEthanol conversion processCorn ethanol conversion rateInputs for nitrogen fertilizerNitrogen fertilizer application rateCorn yieldStudy/yearEnergy balance of bioethanol (Shapouri et al., 1995)Energy converted into ethanol or its coproductsminus energy used to produce ethanolNet energy value (NEV)6. Energy Balance 9Development of technologies9Corn yield9Fertilizer9Energy9Application rate9Ethanol conversion9Farm machinery9CoproductsCauses of discrepancies6. Energy Balance Change in NEV (Niven R.K., 2005 )7. Concerns Environmental impacts of ethanol in gasoline (Niven R.K., 2005)8. Conclusion 9Many sophisticated techniques for productionof bioethanol9Its energetic efficiency and environmentalfriendliness are still controversial.Thank