ethanol production

04/22/23 1

Ethanol Production

John NowatzkiNDSU Extension Service

204/22/23John Nowatzki - Ag & Biosystems Engineering, NDSU (9-2006)

Introduction

What is Ethanol?Ethanol Production From BiomassEthanol Production From GrainsEthanol Engine Fuel CharacteristicsEthanol Strengths & Weaknesses


What is Ethanol?

Ethanol is a clear liquid made from fermenting sugars from: Grains – grain ethanol Biomass – cellulosic ethanol

Ethanol is an engine fuel that burns to produce carbon dioxide and water


Cellulosic Ethanol Production

Ethanol

Lignin

Lignin

CellulosicFeedstock

1st Pretreatment(convert hemi-cellulose into xylose and reduce size and open up structure of cellulose)

Fermentation ofxylose and other simple sugars from hemi-cellulose

2nd Pretreatment(convert cellulose into Glucose)

Simultaneoussaccharification & fermentation

Glucosefermentation

Distillationto recoverethanol

Fuel forheat and electricity


Cellulosic Ethanol Production Convert hemi-cellulose into pentoses (5 carbon sugars)

and partial breakdown of cellulose

Each type of cellulosic feedstock requires a unique combination of pretreatments. Physical methods:

steam explosion Chemical methods:

dilute acid, alkaline, organic solvent, ammonia, sulfur dioxide, carbon dioxide

Biological methods:

1st Pretreatment



Convert cellulose into hexoses (6 carbon sugars) The cellulose fraction is hydrolyzed by

acids or enzymes to produce glucose Enzymatic hydrolysis – biological

conversion of cellulose to sugars Acid hydrolysis – acid concentrations to

convert cellulose to sugars

2nd Pretreatment



The solids remaining after the hemi-cellulose and cellulose are converted to sugars are washed, dried and used as fuel source for power production.

Lignin (By-product)


Cellulosic Ethanol Production Hydrolysis breaks down the hydrogen

bonds in the hemi-cellulose and cellulose fractions into their sugar components: pentoses and hexoses.

The yeast contains an enzyme called invertase, which acts as a catalyst and helps to convert the sucrose sugars into glucose and fructose (both C6H12O6)

Hydrolysis (saccharification)


Cellulosic Ethanol Production The fructose and glucose sugars reacts with an

enzyme called zymase, which is also contained in the yeast, to produce ethanol and carbon dioxide.

The fermented mash, called beer, contains about 10% alcohol plus all the non-fermentable solids from the corn and yeast cells.

The mash and solids are separated

Fermentation

(After fermentation the cellulosic and grain ethanol production processes are similar and will be explained together.)


Grain Ethanol ProductionDry Milling Process

Ethanol

Saccharify

Liquify & Cook

Grain

Grind

Fermentation

Distillation Dehydration

Centrification

Evaporation Dryer

Distillers Solubles DistillersGrainsw/Solubles

DriedDistillersGrains

Enzymes

Saccharify

Liquify & Cook

Grain Fermentation

Distillation Dehydration

Centrification

Evaporation Dryer

Distillers Solubles

DenaturingCO2

Beer

Whole Stillage

Thin Stillage

190Proof

Syrup

Wet Grains

200

Proof


Grain Ethanol ProductionGrinding

The grain passes through a hammer mill which grinds it into a fine powder called meal.


Grain Ethanol ProductionLiquify and Cooking

The meal is mixed with water and cooked to liquify the starch. Heat is applied to enhance liquefaction resulting in a mash. Enzymes are added to facilitate starch

breakdown


Grain Ethanol ProductionSaccharify

An enzyme is added to the mash to convert the liquefied starch to fermentable sugars


Grain Ethanol ProductionFermentation

Yeast is added to the mash to ferment the sugars to ethanol and carbon dioxide.

In a batch process, the mash stays in one fermenter for about 48 hours before the distillation process is started.


Ethanol Production The distillation involves boiling the water

and ethanol mixture. Since ethanol has a lower boiling point (78.3C) than water (100C), ethanol vaporizes before water and can be condensed and separated

The distilled alcohol is about 96% strength.

Distillation (Cellulosic or Grain)


Ethanol ProductionDrying & Denaturing

(Cellulosic or Grain)

Most ethanol plants use a molecular sieve to water from the distilled ethanol.

Fuel ethanol must be denatured, or made unfit for human consumption, with a small amount of gasoline (2-5%)


Grain Ethanol ProductionDried Distillers Grains (DDG)

DDG is a by-product of grain ethanol production.

Drying the distillers grain increases its shelf life and reduces transportation costs

A bushel of corn (56 lbs) yields about 2.8 gallons of ethanol and 17 pounds of distillers grain


Grain Ethanol ProductionDried Distillers Grains with Solubles (DDGS)

DDGS is a by-product of grain ethanol production.

The liquid that is separated from the mash during the distilling process is partially dehydrated into a syrup, then added back onto the dried distillers grain to create DDGS


Ethanol Production(Cellulosic or Grain) Carbon Dioxide (CO2)

CO2 is given off during fermentation Ethanol production plants collect,

compress, and sell it for use in other industries


Ethanol Fuel CharacteristicsEthanol E100

E8585 % Ethanol – 15 % Gasoline

Gasohol10 % Ethanol – 90 % Gasoline

Gasoline

BTU,s/Gal 84,400 90,000 120,900 125,000

Octane Number

100 98 94 87 - 93

Equitable Value (BTU)

$2.02/gal $2.16/gal $2.90/gal $3.00/gal


Ethanol Strengths & Weaknesses Potential Strengths

Fewer air pollutants Renewable sources

Potential Weaknesses Fewer BTU’s per gallon Higher ethanol blends require engine modification


More Information

http://www.ag.ndsu.nodak.edu/abeng

John Nowatzki, NDSU Extension State Specialist

Telephone: 701-231-8213

Email: [email protected]

ethanol production

Documents

cellulose fractions

carbon sugars

glucose sugars

simple sugars

fermenting sugars

sucrose sugars

biomassethanol production

power production