Ethanol. Conversion of sugars to ETOH The manufacture of alcoholic beverages originated over 5000 years ago –Water was generally impure and thus fermented.
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Conversion of sugars to ETOH The manufacture of alcoholic beverages originated over 5000 years ago –Water was generally impure and thus fermented juices provided a level of protection from spoilage by their high alcohol content
Ethanol as a fuel Long History –Anhydrous ethanol used as an internal combustion engine fuel in the late 19th century –In 1906 Congress removed the tax on ethanol to encourage farmers to use it as a fuel –With appropriate pre-treatment various forms of biomass can be used Brazil National Alcohol Program –Effort to replace gasoline with ethanol –Since 1975 over 50 billion liters of alcohol made –40% of Brazil’s 14 million cars used ethanol (95% ETOH/5% H 2 0) –60% used 78% gasoline 12% ETOH US is the second largest alcohol producer –1980 Energy Security Act –Gasohol - 10% ETOH - about 7% of total nationwide gas sales lead free, produces less NOx and CO –2001 1.8billion gallons of Ethanol produced mainly from corn Cost-competitiveness based solely on government subsidies
Ethanol fuel properties in relation to fuel performance Energy density Heat of vaporization Lower flame temperature Relative volume of combustion products Octane Number 0.65-0.69 2.3 0.976 1.07 1.15 Lower mpg Larger tank More air to cylinder Increased power Decreased cooling needs Higher efficiency in optimized engine Increases work from gas expansion Allows increased compression ratio and hence higher Power and efficiency Property Ethanol/Gasoline Value Impact From Lynd 1996;Bailey 1996
Reasons to use Ethanol Energy security Ethanol offers substantial environmental benefits. –Ethanol makes gasoline burn cleaner. –Ethanol reduces greenhouse gas emissions. Ethanol is made from abundant renewable resources. Ethanol is good for farmers and rural economy.
Size Reduction Dilute Acid Pretreatment Liquid Solid Separation Detoxification Via Ion Exchange Enzyme ProductionSSCF Fermentation Separation Solids Processing Cogen Biomass Fuel Grade Ethanol Simplified Bioethanol Process
Current Ethanol Costs Net Feedstock Costs Other Operating Costs Total Production Costs Annualized Capital Costs Selling Price 0.54 0.42 0.96 0.26 1.22 0.48 0.46 0.94 0.22 1.16 $/gal Dry MillWet Mill 0.37 0.25 0.62 0.54 1.16 Cellulosic (estimate)
Effect of Biomass Cost on Ethanol Production Cost
Natural Vegetation and Ag/Urban Waste From Lynd (1996) Mixed paper Packing Urban wood Yard waste Agricultural residues Forest residues Wood processing residues Total 26 14 4 11 120 9 3 187 Waste category Availability (million dry tons)
Waste Ag Cellulosics Corn stover is available in the highest amounts - 100 to 200 million tons per year. Bagasse could contribute another 700,000 tons. If all of the corn stocks and bagasse were collected, about 6.5 billion gallons of ethanol could be produced annually. Only 30 to 60% of the total stover and bagasse could be collected, reducing the potential ethanol to 2 to 4 billion gallons annually.
Variability of the literature calculations Acres Land Need Ethanol Required Ethanol Yield Biomass Yield Acres Gallons Ethanol 1 () Tons Biomass Acre () Tons Biomass Gal Ethanol ()
Hohenstein & Wright Rainey & Mann Wright et al. Cook & Beyea Downing et al. Switchgrass General SRWC HEC Energy cane Hybrid Poplars Natural Forests Low High Low High Low High Low High Low High Low High 2 (4) 6 (14) 5 (12) 14 (32) 4 (10) 8 (17) 5(12) 9 (20) 16 (35) 4 (9) 10 (22) 2 (4) 11 (25) 5 (12) 21 (48) 1 (2) 2 (4) 4 (10) 7 (15) 9 (20) 5 (11) 10 (22) Plant Type Source tons/acre (metric tons/hectare) Biomass Yields from Literature
Gross Calculation 195 billion gallons of ethanol needed Using Switchgrass 195 to 600 million acres of land
Land Use in the Contiguous 48 States Use Acreage (Million Acres) Proportion of Total Area (%) Grassland Pasture & Range Forest Cropland Special Use Other Use 589 559 460 194 92 31 30 24 10 5
Environmental Impact Food vs. energy Land use competition Soil quality Water quality Chemical inputs Biodiversity –monoculture –suitability for wildlife habitat –landscape effects –stability
Greenhouse gas emissions reduction Burning fossil fuels converts “old biomass” into new CO 2 ” - this then contributes to the greenhouse effect Burning “new biomass” contributes no net CO 2 if we replant the harvested biomass or burn biomass specifically grown for energy generation (energy crops)