Corn to ethanol

Agenda

Corn to to ethanol» Starch» Energy balance» Production

– Dry milling– Wet milling

» Problems Corn to ethanol subsidy Archer Daniels Midlands (ADM) Discussion

Rise of biofuels (history)

H. Ford 1908 R. Diesel 1987 Sugar cane ethanol 1920 OPEC oil embargo (1973) Methyl tertiary-butyl ether MTBE (started in

1992, phased out in 2000) (2-methoxy-2-methylpropane )» Good blending» Increase octant number» Cheap, produced from natural gas» Toxicity

Oil in Middle East $$$$

Corn in US

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

Starch

White powder

Corn, potatoes, tapioca

Carbohydrate, sugar

» Many glucose molecules

Chemical Composition of Starch

Plants contain two types of starch, linear (helix) amyloses and branched amylopectins.

The amounts of each of these starch types present is plant dependent.» Typical amounts are 25% amylose, 75%

amylopectin

Amylose

14 -D-Glucopyranose Because of the bonding, this molecule forms a helix

» It takes 6 gluopyranose units for each turn» Amylose is not water soluble

O

H

O

H

HO

H

O

OHHH

OH

O

H

H

HO

H

O

OHHH

OH

n

Amylopectin

14 D-Glucopyranose + 16 D Glucopyranose

Amylopectin is a branched polymer» Branching inhibits

helix formation» This starch is

therefore somewhat water (hot) soluble.

O

H

O

H

HO

H

O

OHHH

OH

O

H

H

HO

H

OHHH

OH

O

H

O

H

HO

H

O

OHHH

OH

O

H

H

HO

H

O

OHHH

O

n

US ethanol production

Corn versus crude oil (US)

Corn

One bushel of corn (56 pounds after husks and cobs are removed) provides:» 31.5 pounds of starch or » 33 pounds of sweetener or » 2.8 gallons of ethanol

+ 13.5 pounds of gluten feed 2.6  pounds of gluten meal 1.5 pounds of corn oil

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

Biofuels-comparison

Production (billion gallons)

Production cost ($)

Energy balance

GHEreductio

n (%)

Corn 4.86 1.09 1.3 22

Sugar cane 3.96 0.87 8.0 55-90

Lignocellulose

NA NA 2-36 91

Biodiesel 0.50 NA 2.5 68

Dry versus wet milling

Dry versus wet milling » Dry grind process: the entire corn kernel is first ground into flour and

the starch in the flour is converted to ethanol via fermentation– CO2 (used in the carbonated beverage industry) – Animal feed called distillers dried grain

» Wet milling: first the separating the corn kernel into starch, protein, germ and fiber in an aqueous medium prior to fermentation

– The primary products of wet milling include starch and starch-derived products (e.g. high fructose corn syrup and ethanol), corn oil, corn gluten, and corn gluten

Corn (starch) can be converted into ethanol in 3-5 days» Starch + water to form a mash» Mash + heat + enzymes (amlysases)=glucose» Glucose + yeast (fermentation) = CH3CH2OH + CO2 » “Beer”=10 - 15 % CH3CH2OH and 85 % H2O» The "beer" is then boiled in a distillation column to separate H2O and

CH3CH2OH up to 95%» Additional 5% of H2O removed by molecular sieves (size exclusion)

100% ethanol

pH 6+heat 110°C +-amylase30 min liquid, dextrins (5-10 glucose)

Yeast+ mash+glucoamylase (SSF)glucose and maltose fermented to ethanol and CO2, 48-72 hours

5% water removed by sieves

Conventional distillation 95%

52°C, sulfurous acid (0.2%) 30-36 hours

-amylase+heat 90°C+glucoamylase ,SHF, series of reactorssemicontinuous process

Corn wet milling process

Ethanol versus oil subsidy

Since 1968 ethanol industry had received $11.6 billion in tax incentives

Since 1968 oil industry had received over $150 billion in tax benefits.

Oil industry produced 1,068 times more energy

Subsidy per unit of energy was 54 higher for ethanol (ethanol gets 54 cents oil gets 1cent).

US General Accounting Office

Problems (1)

Environmental problems» Greenhouse gas emission

– Ethanol plants burn natural gas or coal to create the steam, adding to fossil fuel emission with CO2 from fermentation

» Energy value» Pesticides, herbicides (nitrogen runoff from fertilizers)» Fertilizers (N, made with natural gas and diesel farm

machinery)» Water demands: 3.6-6gallons of water/1 gallon of

ethanol Social problems

» Competing with food industry– Doubling the price of corn (food riots in Mexico)

Problems (2)land availability

Problems (3)

More environmental problems» “Most economic analyses of corn-to-

ethanol production overlook the costs of environmental damages, should add another 23 cents per gallon”

» Soil erosion– "Corn production in the US erodes soil about 12

x faster than the soil can be reformed, and irrigating corn mines groundwater 25 % faster than the natural recharge rate of ground water “

David Pimental Cornell University

Corn to ethanol (1)

1 acre of US corn =7,110 pounds of corn = 328 gallons of ethanol

Planting, growing and harvesting that much corn requires about 140 gallons of fossil fuels and costs $347 per acre.

Even before corn is converted to ethanol, the feedstock costs $1.05 per gallon of ethanol.

Corn to ethanol (2)

“The average US automobile, traveling 10,000 miles a year on pure ethanol (not a gasoline-ethanol mix) would need about 852 gallons of the corn-based fuel. This would take 11 acres to grow, based on net ethanol production. This is the same amount of cropland required to feed seven Americans”

David Pimental Cornell University

Corn to ethanol (3)

“If all the automobiles in the United States were fueled with 100 % ethanol, a total of about 97% of US land area would be needed to grow the corn feedstock. Corn would cover nearly the total land area of the United States”

David Pimental Cornell University

Corn to ethanol industry

Profits in 2006 for Archer Daniels Midlands (ADM) ~DOUBLED (increased from $259 million to $446 million)

August 2006 US 101 ethanol plants» 39 refineries are under construction» 7 existing are expanding

Corn to ethanol plants in US

Based on August 30th, 2006

Discussion

What do you think about corn to ethanol process, industry?» Something positive or negative?