President Bush and the Empty Promise of Ethanol or E-85

B14237 / Tue, 4 Apr 2006 09:11:43 / Environment

Question #1: Can ethanol from corn or other grain replace gasoline?

Answer: Certainly not, for several reasons.

There isn’t enough grain. The best process we have makes about 2.66 gallons of ethanol from a bushel of corn (maize). The 2004 maize harvest was about 11.8 billion bushels; if all of it was used for ethanol, it could make a maximum of 31.4 billion gallons of ethanol (with energy equivalent to about 22 billion gallons of gasoline). US gasoline consumption in 2003 was roughly 134 billion gallons, or more than 6 times the amount which can be replaced by ethanol production from corn. Total US motor fuel consumption (gasoline and diesel fuel) is approximately 200 billion gallons per year.

Ethanol requires too much other fuel to produce it. A gallon of ethanol (84,200 BTU) consumes about 33,000 BTU of heat in the distillation process alone. Some of this heat comes from coal or cogenerators, but most distillers burn natural gas or LPG. LPG is a petroleum byproduct, and natural gas supplies are tight and getting tighter. Ethanol producers are competing with people who need to heat their homes. The energy losses of the ethanol process make it more efficient to burn the grain for heat, and use the LPG or natural gas as motor fuel (source).

Question #2: Someone sent me an e-mail about bio-butanol as a replacement for gasoline. Could we get rid of oil this way?

Answer: No.

Environmental Energy, Inc ( claims a process which yields 2.5 gallons of butanol per bushel of corn (maize). They further claim 105,000 BTU/gallon of butanol vs. 84,200 BTU/gallon of ethanol (~25% more energy) which makes it a superior fuel. This is true so far as it goes, but this also runs into limits of raw materials; 11.8 billion bushels of corn would make 29.5 billion gallons of butanol. This would displace less than 1/5 of US gasoline consumption, with nothing extra to replace diesel fuel. The major advantage of butanol over ethanol is that it would require far less energy to separate it from water; it would be worthwhile to promote butanol rather than ethanol for energy-security reasons.
Source: Environmental Energy, Inc (

Question #3: Could ethanol from crop wastes replace gasoline?

Answer: Probably not; there almost certainly isn’t enough biomass available.

The surplus biomass of corn stalks and such (corn stover) is the largest single biomass source in the US; it yields about 2.5 tons/acre (source) at the average yield of 146 bu/ac. The surplus biomass over the entire 80.7 million acres planted to corn is roughly 200 million dry tons per year. Even if the entire dry mass was converted to ethanol with the same efficiency as grain (2.66 gallons per 56-lb bushel, or 31.3% by weight), it would only produce 62.6 million tons (19.0 billion gallons) of ethanol, equivalent to about 13.3 billion gallons of gasoline. In practice only 30% to 60% of this biomass could be made available for fuel production, and the energy requirements for distillation come on top of this.
Source (corn stover yield)
Source (2004 corn harvest)

The heating value of shelled corn has several different values published on-line; my first two results were 314,000 BTU/bushel and 381,000 BTU/bushel. (Unfortunately, the graph presented in the latter is not easily examined to determine if the two calculations are actually using very similar figures and the latter is merely a character-swapped typo.) Assuming the lower figure is relatively safe (favors the status quo), so here goes.

Converting corn to ethanol at a rate of 2.66 gallons per bushel and using 33,000 BTU/gal of gas for distillation yields 2.66 gallons (224,000 BTU) of ethanol, at a cost of 87780 BTU of natural gas.

Burning shelled corn (314,000 BTU/bu) at an efficiency of 75% yields 235500 BTU of heat at zero cost in natural gas. The natural gas freed up (87,780 BTU not used in distillation + 235500 BTU not used for heat) totals 323,280 BTU/bushel, or 32% more than the heating value of the ethanol the corn would otherwise produce. The first 235500 BTU of natural gas could be used to power NGV’s, and the rest would be surplus over the ethanol scenario. (This comparison would be far more lopsided in favor of burning corn if the 381,000 BTU/bushel figure was used.)

Conclusion: Not considering other value-added products, it is energetically more efficient to burn shelled corn for heating fuel and use natural gas for motor fuel than it is to use the corn and gas to make ethanol for motor fuel.

UPDATE 2005-Sep-08: temposter offers the figure of 392,000 BTU/bushel (citing an Ontario source) in the comments. Given that maize is a natural product and the fuel value is likely to vary based on oil content (which in turn depends on the exact strain and growing conditions), the value of 381,000 BTU/bu seems realistic. At the 381,000 BTU value, each bushel burned for heat would produce 285,750 BTU of useful heat and displace 373,530 BTU of natural gas or LPG. The ethanol which could have been produced from the maize would have produced 220,400 BTU at most, the net benefit from burning the corn as heating fuel is at least 153,000 BTU/bushel

Source The Ergosphere

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Think green, go yellow?


GWHunta @ 05/10/06 20:22:36

So how does Brazil manage to do it?

Shogo @ 05/10/06 20:43:15

They have more arable land per miles driven. Do the math.

Sly_UPer @ 05/10/06 21:48:52

So how does Brazil manage to do it?

Shogo, you read my mind. If ethanol is completely cost-ineffective, then how does a large yet comparatively poorer country with tons of vehicles get away with it?

Maybe the criticisms about ethanol are less than objective (corporate concerns spiking the science?). True enough, Brasil will have to sacrifice a fair amount of land to maintain ethanol production, but I doubt they will destroy their entire country just to drive.

It said on that Dateline show that Walmart will soon be offering Ethanol stations. Once the hybrid engines sneak in to the US economy, the Walmart infrastructure is large enough to make a serious dent in the equation. Part of their vast PR campaign? Or shrewd business projection of the future?

Continuity @ 05/11/06 00:49:51

I doubt they will destroy their entire country just to drive

I don’t doubt it, but for sure they will allow people to be forced off their land and allow others to starve. They aren’t that much better than Americans.

Brasil has 1/5 to 1/10 the # cars the US does, and those they have get much better mileage. They also don’t have the same degree of expansive suburban sprawl that exists here, yet.

Maybe the criticisms about ethanol are less than objective (corporate concerns spiking the science?)

I dunno, I somehow doubt it. Archer Daniel Midlands, Monsanto, Cargill, etc. are big players here so I would expect skewed science to be on both sides. From what I have read, I think that ethanol really is currently a net-energy loser but will eventually have a better EROEI (though never anything like crude oil/petrol).

sisyphus @ 05/11/06 01:31:35

Evolution of the fleet in Brazil – some numbers and the like on the fleet of cars there (a few years old).

sisyphus @ 05/11/06 01:33:09

Excellent breakdown of switchgrass and corn as fuelstock at the Oil Drum: Life in a Grass House

sisyphus @ 05/11/06 02:14:38

Have any numbers on the use of biomass from residential and commercial property? If each county had a central processing plant to produce ethanol instead of compost (Cobb County, GA has a composting facility), you may be able to supplement biomass processing from other sources (corn byproduct, pine chips, etc.)

gnnbeta @ 06/01/06 11:02:33

So how does Brazil manage to do it?

Brazil has an equitorial tropical climate where sugar cane is harvested three times annually and is used to produce Brazil’s ethanol.

North American corn based ethanol production is limited by the changing seasons to a single harvest and our agricultural process is heavily oil dependent.

Ethanol production is also dependent on fossil fuel. Coal is rapidly replacing natural gas as the fuel of choice.

For another sound reason that this technology isn’t going to help solve the “global warming issue” read this article.

GWHunta @ 06/11/06 15:57:00

This is obviously from the prices an old photo but part of the success of E85 fuel in Minnesota is price. Stations are able sell E85 for 40 to 50 cents less than regular unleaded gasoline.

I personally believe the whole GM: “Live Green Go Yellow” is simply an attempt to move vehicles off the lots. There’s is barely enough ethanol available to replace the MTBE, the use of which has been discontinued for liability reasons.

Getting sufficient ethanol on the market to provide enough E-85 to fuel just the existing flex fuel fleet would require redirecting the bulk of the surplus corn harvest to ethanol production.

However, owning a flex fuel vehicle if you happen to be one of those who can forsee the looming possibilities of wider war in the Greater Middle East and the resulting supply disruptions of crude oil.

It would do much to ease your personal anxieties about how your going to get around next summer, that is of course if your conscience will let you drive on the fuel that could have been used to feed someone else.

That’s the dirtiest part of this little “secret”.

Sometimes no Peace,

GWHunta @ 06/13/06 11:19:34

5 Responses to President Bush and the Empty Promise of Ethanol or E-85

  1. gwhunta says:

    An ethanol plant/distillery emits more CO2 directly to the atmosphere, pound for pound, than the end product ethanol it produces; which then has to be transported by tanker, because it is too corrosive to be transported in existing petroleum product pipelines.

  2. gwhunta says:

    Higher Crude Oil Prices Could Send More US Ethanol Overseas

    U.S. market saturated, yet with a Federal budget alleged to be in desperate need of deep cuts in domestic spending, ethanol subsidies remain in the President’s budget, effectively shipping U.S. taxpayer dollars oversees with every gallon of ethanol exported.

    At the same time U.S. consumers are warned to expect at least a 5% increase in the cost of food with current 2 1/2 year highs on cereal grains, due in no small part to the production of ethanol.

  3. GWHunta says:

    Facts about Corn Ethanol Production
    More Facts about Fuel Ethanol

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