Corn to ethanol

1
Corn to ethanol
2
Agenda

• Corn to to ethanol
• Starch
• Energy balance
• Production
• Dry milling
• Wet milling
• Problems
• Corn to ethanol subsidy
• Archer Daniels Midlands (ADM)
• Discussion

3
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-methylpropa
  ne )
• Good blending
• Increase octant number
• Cheap, produced from natural gas
• Toxicity
• Oil in Middle East

4
Corn in US
5
Corn plant
Corn kernel (without the fibre)-starch
alcohol Corn fibre-lignocellulosic alcohol Corn
stover-lignocellulosic alcohol
6
Starch

• White powder
• Corn, potatoes, tapioca
• Carbohydrate, sugar
• Many glucose molecules

7
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

8
Amylose

• 1?4 ?-D-Glucopyranose
• Because of the bonding, this molecule forms a
  helix
• It takes 6 gluopyranose units for each turn
• Amylose is not water soluble

9
Amylopectin

• 1?4 aD-Glucopyranose 1?6 ? D Glucopyranose
• Amylopectin is a branched polymer
• Branching inhibits helix formation
• This starch is therefore somewhat water (hot)
  soluble.

10
US ethanol production
11
Corn versus crude oil (US)
12
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

13
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) 11.3
  or negatives values
• Greenhouse gas emission during production and use
  22 less compared with gasoline

14
Biofuels-comparison
Production (billion gallons) Production cost () Energy balance GHE reduction ()
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
15
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
• Beer10 - 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

16
52C, sulfurous acid (0.2) 30-36 hours
pH 6heat 110C ?-amylase 30 min liquid,
dextrins (5-10 glucose)
?-amylaseheat 90Cglucoamylase , SHF, series of
reactors semicontinuous process
Yeast mashglucoamylase (SSF) glucose and
maltose fermented to ethanol and CO2, 48-72
hours
Conventional distillation 95
5 water removed by sieves
17
Corn wet milling process
18
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
19
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)

20
Problems (2)land availability
21
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
22
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.

23
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
24
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
25
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

26
Corn to ethanol plants in US
Based on August 30th, 2006
27
Discussion

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