Basic Chemistry of Ethanol Production presented at CCURI Biofuels Workshop Muskegon Community College Muskegon, MI October, 17 – 20, 2013 by Chuck Crabtree Director – Iowa BioDevelopment Indian Hills Community College Ottumwa, IA

Topics 1.What are carbohydrates? 2.What is glucose? 3.Why is glucose important? 4.What is starch? 5.What is cellulose? 6.How are the structures of starch and cellulose similar and how are they different? 7.How is starch used to make ethanol? 8.How is cellulose used to make ethanol? 9.What are some of the more common feedstocks used for ethanol production?

Carbohydrates – Starch and Cellulose What is a carbohydrate? Organic compounds that contain only carbon, hydrogen, and oxygen What do carbohydrates do? Store energy (food) – starch (corn, potatoes) Structural – cellulose (plant stems, wood) Basic component of both starch and cellulose? Glucose

= Oxygen = Carbon Glucose Basic Structure = Hydrogen

Glucose Basic Structure = Oxygen = Carbon

= Oxygen = Carbon Glucose Basic Structure

Glucose – Important Facts Also called “fermentable sugar,” “dextrose,” “corn sugar” or “sugar” Used by biological systems as food It is a “monomer” – Mono means “one” or “single.” Starch is a “polymer” – Poly means “many.”

What is a monomer? One unit of a string of units Monomers

What is a monomer? One unit of a string of units Example: Pearl necklace If a monomer is 1 unit of a string of units, then what is the monomer of a pearl necklace? Monomers

What is a monomer? One unit of a string of units Example: Pearl necklace If a monomer is 1 unit of a string of units, then what is the monomer of a pearl necklace? A pearl! Monomers

What is a polymer? A string of similar units Polymers

What is a polymer? A string of similar units Example: Pearl necklace If a polymer is a string of similar units, then what is the polymer of a pearl? Polymers

What is a polymer? A string of similar units Example: Pearl necklace If a polymer is a string of similar units, then what is the polymer of a pearl? A pearl necklace! Polymers

The pearl is a monomer – When connected with other pearls they make a polymer called a pearl necklace Same principle applies to chemicals – Glucose is a monomer – When connected with other glucose molecules they make a polymer called starch or cellulose Monomers and Polymers

Starch is a polymer > 500 glucose units Two types of starch

Starch is a polymer > 500 glucose units Two types of starch Amylose – straight chains

Starch is a polymer > 500 glucose units Two types of starch Amylose – straight chains Amylopectin – branched chains

Starch vs. Cellulose Structure Starch Structure Cellulose Structure

Cellulosic Structure Cellulose Structure Glucose Molecule

Cellulosic Structure Cellulose Structure Glucose Molecule Individual Cellulose Molecules

Cellulosic Structure Cellulose Structure Individual Cellulose Molecules Glucose Molecule

Cellulosic Structure Cellulose Structure Cellulose Microfibril Individual Cellulose Molecules Glucose Molecule Lignin

Cellulosic Structure Cellulose Structure Individual Cellulose Molecules Glucose Molecule Cellulose Microfibrils Cellulose Fiber Non-cellulose Polysaccarides Lignin

Lignin Structure Very complex structure Second most common molecule on earth. Lacks a defined structure Fills the spaces between cellulose

Hemicellulose Structure

Enzymes are proteins that speed up chemical reactions, but are not altered themselves (catalysts) Enzymes

Enzymes are proteins that speed up chemical reactions, but are not altered themselves (catalysts) Enzymes

Enzymes are proteins that speed up chemical reactions, but are not altered themselves (catalysts) Enzymes

Enzymes are proteins that speed up chemical reactions, but are not altered themselves (catalysts) Enzymes Reaction can go either way

Glucose Linkages and Enzyme Active Sites

Named for the way two glucose molecules are attached to each other. Glucose Linkages and Enzyme Active Sites ,6 linkage 1,4 linkage

Amylopectin – Branched Starch Molecule

Introducing the enzyme α -amylase.

Amylopectin – Branched Starch Molecule Introducing the enzyme α -amylase. α -amylase breaks down starch into shorter glucose chains called “dextrins.” Breaks 1,4 linkages that are not terminal.

Dextrins Amylopectin – Branched Starch Molecule Introducing the enzyme α -amylase. α -amylase breaks down starch into shorter glucose chains called “dextrins.” Breaks 1,4 linkages that are not terminal.

Dextrins

Introducing the enzyme glucoamylase.

Glucoamylase breaks down dextrins into individual glucose molecules. Acts on 1,4 and 1,6 terminal linkages. Introducing the enzyme glucoamylase.

What about Cellulose Since starch and cellulose are glucose polymers, why is cellulose so much harder to break down into glucose? So how do we get through the other stuff to get to the cellulose? Once we get to the cellulose, will the same enzymes work?

Cellulose Pretreatment Options Physical Breakdown (heat/pressure, grinding, chopping, sonication) Weak Caustic (NaOH, Ammonia) Weak Acid (Sulfuric, HCL) Heat with caustic and acid Pressure and heat with caustic and acid Enzymatic cocktails (cellulases, zylases, gluconases, ligases, hemicellulases, etc). Usually used after at least one of the above. Time can vary on all of these.

Cellulose as Other Forms of Fuel Straight Combustion – Most common PyrolysisPyrolysis (bio-oil)– Usually high temps and pressures. Some low temp technologies. Syngas – Gasification of organic material at high temps (without combustion) with oxygen and steam to produce CO, H, and CO 2

Ethanol Feedstocks

Feedstocks Three Types of Feedstocks Starch-rich feedstocks Sugar-rich feedstocks Cellulosic feedstocks Sugar Cane Cellulose Corn

Starch-Rich Feedstocks Two Types of Starch-rich Feedstocks Tubers Cassava Potato Cereal grains Corn Wheat Barley Rye Grain Sorghum Triticale Potato Barley Triticale Cassava Sorghum Wheat Corn

Starch-Rich Feedstocks Tubers Cassava Potato Cassava

Starch-Rich Feedstocks Cereal Grains Wheat Barley Wheat

Starch-Rich Feedstocks Cereal Grains Rye Grain Sorghum Triticale Rye Grain Sorghum Triticale

Sugar-Rich Feedstocks Three Primary Sources Sugar Cane Sugar Beets Sweet Sorghum Sugar Cane Sugar Beets Sweet Sorghum

Sugar-Rich Feedstocks Different process than for starch-rich feedstocks. Sugar Feedstock Process Washing Breaking Milling Straining Clarification Evaporation Mash Preparation Fermentation Distillation/Dehydration Starch Feedstock Process - Milling - Mashing/Cooking/Liquifaction Fermentation Distillation/Dehydration Sugar juice/syrup preparation

Sugar-Rich Feedstocks Sugar Cane

Sugar-Rich Feedstocks Sugar Beets Sweet Sorghum Sugar Beets

Cellulosic Feedstocks Cellulose What is it? General term – Biomass Straight chain polymer of glucose molecules Used by plants in cell walls Wood Chips Hay

Cellulosic Feedstocks Cellulose Where does it come from? Plant material Wood Grasses (e.g., switchgrass) Crop residue (e.g., corn stover)

Cellulosic Feedstocks Cellulose Where does it come from? Plant material Wood Grasses (e.g., switchgrass) Crop residue (e.g., corn stover) Advantages No food vs. fuel issues Worldwide distribution High glucose density

Cellulosic Feedstocks Cellulose Where does it come from? Plant material Wood Grasses (e.g., switchgrass) Crop residue (e.g., corn stover) Advantages No food vs. fuel issues Worldwide distribution High glucose density Disadvantages Difficult to breakdown Bulky

Sources of Information The Alcohol Textbook, Fifth Edition, W.M Ingledew, D. R. Kelsall, G. D. Austin and C Kluhspies, eds. Nottingham University Press, Nottingham, UK, Portaria Nº 143, de 27 de Junho de 2007 (in Portuguese). Ministério da Agricultura, Pecuária e Abastecimento. Retrieved This decree fixed the mandatory blend at 25% starting July 1st, 2007 Luiz A. Horta Nogueira ( ). "Perspectivas de un Programa de Biocombustibles en América Central: Proyecto Uso Sustentable de Hidrocarburos" (in Spanish) (PDF). Comisión Económica para América Latina y el Caribe (CEPAL). Retrieved UNICA: venda de veículos flex no Brasil cresce 13,9% em 2009 e frota ultrapassa 9 milhões de unidades (in Portuguese). UNICA Retrieved