Bioethanol versus biodiesel
Feedstocks (competition with food industry)
Major producers Process Yields Production facilities
Feedstock
Any starch/sugar rich biomass» Agricultural biomass
– Corn– Wheat– Sugar cane – Sugar beets– Straws– Corn stover
» Woody biomass
History
1916 utilization of Clostridia acetobutylicum for acetone production by Chime Wizemann (fermentation process)» Smokeless gun powder
1945 the second most important commercial fermentation process
1960 growth of petroleum industry» Butanol production via petrochemical pathway
1980-2008» Biological pathway
Ethanol versus butanol
Energy efficiency» Butanol 96% of gasoline
Less volatile than ethanol Less corrosive than ethanol Water-tolerant alternate fuel
» Less hydroscopic than ethanol (it doesn't pick up water)
– pipeline High viscosity
» 2x ethanol» 5-10x gasoline» Problems in the fuel systems of butanol-fueled cars
Lower octane number compared to ethanol » Lower compression ratio and efficiency
Butanol-properties
Sweet smelling solvent Industrial solvent High melting point of 25.5°C causes it to
gel and freeze near room temperature » Additive in gasoline
Industrial commodity » 370million gallon/year» $3.75/gallon» Petrochemical route
Production of butanol (1)
Fermentation» Weizmann organism
(chemist Weizmann)» Anaerobic bacteria » Starch, sugars» Extracellular amylolytic
enzymes and amylase– Glucoamylase etc.
» Distillation (boiling point)
Clostridium acetobutylicum, the "Weizmann Organism"
ABE fermentation (2)
ABE fermentation (acetone, butanol, ethanol) butanol:acetone:ethanol (6:3:1)» Other by-products: » Acetic acid» Lactic acid» Propionic acids» Isopropanol
1 bushel of corn: » 1.3 gallons of butanol» 0.65 gallons of acetone» 0.22 gallons of ethanol (each 1-2%)
Ethanol versus butanol fermentation (1)
Ethanol» S. cerevisiae (yeast)» Temp 30°C» pH 6
» No extracellular enzymes» Monomeric sugars (6C)» Products: 50% ethanol,
50% CO2
» Toxicity of the final product over 100g/L of ethanol
Butanol» Clostridium (bacteria)» Temp 30-40°C» pH 6.8-7 drops to 5.0
(acidogenesis) and increases to 7.0 (solventogenesis)
» Presence of extracellular enzymes
» Starch, cellobiose and monomers (5 and 6C)
» Variety of products» Toxicity of the final
products– 20g/L max of acetone,
butanol, and ethanol
Pure sugar source» Toxicity of butanol to C.acetobutylicum» ethanol, thus butanol, higher recovery
cost of butanol Lignocellulosic substrate
» More inhibitors generated during pretreatment
» Lower butanol yields
ABE fermentation (3)
Fermentation improvements
C.beijernickii» Hydrolysis, fermentation and recovery of
butanol in 1 reactor GM E.coli
» Conversion of keto acids (components of a.a biosynthetic pathway) to butanol
Acetoacetic acid
Environmental Energy Inc.
Environmental Energy Inc. » 2.5 gallons of butanol per corn bushel no
acetone or ethanol» Other processes have not been able to
achieve better than 1.3 to 1.9 gallons of butanol per bushel+A+E.