Bioconversion of biomass to ethanol-an overview Renata Bura November 25 th, 2008

Overview What is bioconversion? Why bioconversion? Sugar cane to ethanol Corn to ethanol Biomass composition Bioconversion to ethanol process –Pretreatment –Hydrolysis –Fermentation Pros and cons of bioethanol

What is bioconversion? General: a process which uses biological agents (microorganisms or protein) to transform a feedstock into desirable products. Bioethanol A chemical/biochemical process by which lignocellulosic materials are converted to ethanol and other co- products.

Bioconversion Biomass Pretreatment Hydrolysis Fermentation Distillation Ethanol

Why bioethanol?

Ethanol (CH 3 CH 2 OH) Ethyl alcohol, grain alcohol –Clear, colorless liquid Ethanol made from cellulosic biomass instead of starch crops-bioethanol Advantages of bioethanol –Domestic renewable fuel sources –Reduces reliance on foreign oil –Cleaner fuel sources –Easily produced and stored –Increases fuel octane number for little cost

Energy content Gasoline Ethanol Biodiesel 100% 67% 86%

World ethanol production

Sugar cane, sugar cane bagasse Sugar cane bagasse Processing Ethanol

Sugar cane bioethanol Brazil produces 3,96 billion gallons of ethanol from sugar cane Production cost $0.87/gallon, the lowest in the world Fossil fuel energy used to make the fuel (input) compared with energy in the fuel (output) 1:8 Green house emission during production and use 56% less compared with gasoline

Corn plant Corn kernel (without the fibre)-starch alcohol Corn fibre-lignocellulosic alcohol Corn stover-lignocellulosic alcohol

Corn to ethanol US produces 4,86 billion gallons of ethanol from corn (2006) Production cost ~ $1.09/gallon Fossil fuel energy used to make the fuel (input) compared with energy in the fuel (output) 1:1.3 or negatives values Greenhouse gas emission during production and use 22% less compared with gasoline

“We can get fuel from apples, weeds, sawdust, almost anything….. And it remains for someone to find how this fuel can be produced commercially- better fuel at a better price than we now know.” Henry Ford Henry Ford

Why bioconversion? Energy –An alternative source of energy for the transportation sector produced locally Air pollution –Reduction in greenhouse gas emission Waste elimination –Elimination of problems with field burning/incineration, stockpiling, etc. Socio/economical benefits –Creation of new jobs, rural development

Possible lignocellulosic feedstocks Agricultural residues (corn stover, corn fibre, wheat straw, rice straw) Wood residues Paper waste Municipal solids waste

Biomass composition

Cellulose

Hemicellulose

Lignin

Bioconversion of biomass to ethanol (pretreatment) Biomass Pretreatment Liquid phase Solid phase Cellulose Sugars Ethanol Fermentation Ethanol Sugars Fermentation Hydrolysis Lignin Recovery

Pretreatment-”disruption” Helps in separation of main biomass components (cellulose, hemicellulose and lignin) Increase available surface area Reduce particle size

Steam explosion Treatment of biomass with high-pressure steam for a short period of time followed by sudden decompression Acid (H 2 SO 4, SO 2 ) impregnation of biomass increases SE efficiency Typical conditions: –Temperature: o C, F –Time: 10sec-10min

Steam gun Karin Fill valve Steam valve Blow valve Receiving vessel Receiving vessel Pretreated corn stover

Bioconversion of biomass to ethanol (hydrolysis) Biomass Pretreatment Liquid phase Solid phase Cellulose Sugars Ethanol Fermentation Ethanol Sugars Fermentation Hydrolysis Lignin Recovery

What are cellulases? Produced by many strains of bacteria and fungi Catalyzes the depolymerization of cellulose chains –Endoglucanases –Exoglucanases –β-glucosidases

Cellulases Endoglucanases (EG) cutting the cellulose chains randomly Cellobiohydrolyses (CBH) cutting cellobiose units of the ends of the cellulose chains Binding domainCatalytic domain

Bioconversion of biomass to ethanol (fermentation) Biomass Pretreatment Liquid phase Solid phase Cellulose Sugars Ethanol Fermentation Ethanol Sugars Fermentation Hydrolysis Lignin Recovery

Fermentation Defined as: Cellular metabolism under anaerobic conditions (absence of oxygen) for the production of energy and metabolic intermediates Many organisms can “ferment” (i.e., grow anaerobically) Not all produce ethanol as an end-product of fermentation

Strain selection Choice of microorganism for ethanol production has traditionally been a Yeast Yeast: –Single cell microorganism –Fungi –Facultative anaerobe Most common industrial fermenter is Saccharomyces cerevisiae (baker’s or brewer’s yeast) Why?

Fermentation Conversion factor g/L of glucose: 0.51g/L ethanol (maximum)

Biofuels-comparison Production (billion gallons) Production cost ($) Energy balance GHE reduction (%) Corn Cane LignocelluloseNA Biodiesel0.50NA2.568

Alternative options??…….

Flexible-Fuel Vehicles (FFV) Use E85 (85% ethanol and 15% gasoline) Cost of FFV is similar to traditional gasoline vehicle 1gallon of E85 provides the same energy as 0.72 gallons of gasoline (lower E content) Special materials required for fuel lines, hoses, valves, gaskets, fuel tank (corrosive ethanol) Washington state more than 35, 000 of FFVs (U.S. over 4 million FFVs) –Ford Focus, Chrysler Sebring, Dodge Stratus, Dodge Caravan, Chevrolet Avalanche

Summary What is bioconversion? Why bioconversion? Sugar cane to ethanol Corn to ethanol Biomass composition Bioconversion to ethanol process –Pretreatment –Hydrolysis –Fermentation Pros and cons FFV

References