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An Analysis of the Current Waste to Ethanol Technology

An Analysis of the Current Waste to Ethanol Technology. Presented by Carole L. Gallagher. Ethanol is Made from the Aerobic Fermentation of Sugar by Yeasts. Four Types of Sugar Polymers:

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An Analysis of the Current Waste to Ethanol Technology

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  1. An Analysis of the CurrentWaste to Ethanol Technology Presented by Carole L. Gallagher

  2. Ethanol is Made from the Aerobic Fermentation of Sugar by Yeasts Four Types of Sugar Polymers: • Mononeric Sugars (simple sugar molecules) Five Carbon Sugars – xylose & arabinose Six Carbon Sugars – glucose, galactose & mannose • Starch, biopolymers of sugar with weak, amorphous molecular bonds

  3. Cellulose, biopolymer of sugar with strong, rigid hydrogen bonds • Hemicellulose, weak, short branched chains of sugar (together with lignin gives a plant its structure)

  4. Sugars Extracted From Cellulose and From Hemicellulose by Hydrolysis I. Acid Hydrolysis uses Sulfuric Acid • Dilute Acid Hydrolysis – Two Stages 1. Biomass & Dilute Acid Mixed, 100C (slurry of zylose from hemicellulose) 2. Pulp Reacidified and Heated to 220C (mostly glucose from cellulose)

  5. Methods of Hydrolysis Continued • Concentrated Acid Hydrolysis –Two Stages 1. Dilute Acid Pretreatment (separates cellulose/hemicellulose which breaks down into xylose) 2. Remaining Biomass Reacidified with Conc. Sulfuric Acid and Heated to 220C (cellulose breaks down into sugars)

  6. Methods of Hydrolysis Continued II. Enzymatic Hydrolysis 1. Traditional Enzymes Bacteria/Yeasts ex. “Cellulase” (stone wash denim) 2. Bioengineered Enzymes (NREL of DOE) III. Biotech Ferment Xylose Into Ethanol Saccharomyces (Ho glucose/xylose) Zymomonas Mobilis (Mex. Pulque from agave 5 times ethanol produced)

  7. Enzymatic Hydrolysis • Nutrient Feed is Sterilized • Cellulose Wastes Heated to 200C • Cellulose Biomass is Milled to 50 microns • Culture Submerged in a Fermenter • Enzymes Break Down Cellulose to Sugar • Glucose Solution is Separated by Filtration • Glucose Then Prepared for Fermentation into Ethanol

  8. Fermentation and Distillation • Acidity in sugar slurry is neutralized with lime and gypsum precipitates out • Nutrients supplied to the fermenting yeast • Sugar & yeast culture is aerated in fermenter • Mixture ferments and expands 200% • Yeast cells centrifuged from mixture • Ethanol is separated from the mash and distilled

  9. Air Emissions CO, NO2 SO2 and Heavy Metals Expensive to Sort MSW Acid Hydrolysis is Expensive & Dangerous Construction of Facilities Is Expensive Enzymatic Hydrolysis is Relatively Untested Ethanol May Not Be Competitive with Gasoline No More Landfills Less Incineration of MSW Make Profits on MSW Produce CO2 & Gypsum Reduce Costs to Produce w/ Bioengineering Less Use of Fossil Fuels Produce Alternative Fuels Benefits v. Problems 0f Waste to Ethanol Technology

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