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Myth: Government offers balanced information on ethanol

June 21, 2008

The US Department of Energy (DOE) has a new factsheet entitled “Biofuels & Greenhouse Gas Emissions: Myths versus Facts.” It’s a fascinating mix of wishful thinking, careful data selection, and occasional outright lies cobbled together to promote the big biofuel agenda.

US Energy Use, 1950-2025It begins with the assertion that US energy consumption will grow by 50% by 2030. That’s twice the increase predicted by the US DOE’s own Energy Information Administration (right). As I showed in a previous post, US energy consumption has actually been leveling off in recent decades, despite consistently incorrect forecasts of perpetual growth. If the trend were to continue, the nation’s energy consumption would peak in 2015. A more likely scenario is a near-term decline in energy consumption in response to rising energy costs, as occurred in the previous two energy crises.

The first “myth” the factsheet adresses is that biofuels emit even more greenhouse gasses than gasoline. That happens to be the conclusion of two recent studies published in Science by researchers at the University of Minnesota and Princeton University. The greenhouse gas emissions don’t necessarily come from producing or burning ethanol (“biofuels burn cleaner than gasoline,” notes the factsheet), but from converting forests and grasslands to biofuel feedstock crops. Studies that assume no loss of forest or grassland show a slight net reduction in greenhouse gas emissions from using biofuels. In the likely event that forests and grasslands are displaced by biofuel feedstock crops, the “myth” may well turn out to be true.

The factsheet goes on to tackle the “myth” that “Ethanol cannot be produced from corn in large enough quantities to make a real difference without disrupting food and feed supplies.” Last year the US dedicated 25% of its record corn harvest to produce 6.5 billion gallons of ethanol. Burning all of that ethanol released 0.6 exajoules of energy. As the graph above shows, the US currently consumes about 105 exajoules of energy each year, so burning ethanol accounted for less than than 0.6% of our energy use. If we had dedicated 100% of our corn to ethanol we might have met 2.5% of our current energy demand. Whether 2.5% constitutes a “real difference” is a matter of opinion, but it’s safe to say that using all or our corn for ethanol would have disrupted food and feed supplies. The “myth” is undeniably true.

The interesting thing is that the factsheet doesn’t actually address the statement it labels a myth. Instead, it talks about the potential for cellulosic ethanol, little of which will come from corn. Citing the Billion Ton Study as its source, it claims that “we can grow adequate biomass feedstocks to displace approximately 30% of current gasoline consumption by 2030 on a sustainable basis —  with no conversion of U.S. croplands.”

By the Billion Ton Study, I assume the factsheet refers to a 2005 report released by the USDA and the US DOE called Biomass as feedstock for a bioenergy and bioproducts industry: The technical feasibility of a billion-ton annual supply. The report concluded that, by 2030, “relatively modest changes in land use” could produce 1.3 billion tons of biomass annually (equivalent to a row of round hay bales circling the earth 75 times) for conversion to enough ethanol to replace 20% (not 30%) of the nation’s transportation fuel plus 5% of the nation’s electricity and 25% of the nation’s chemicals. The necessary “modest changes in land use” include:

  1. A 50% increase in all small grain yields (twice the rate of increase observed over the past 40 years, during an era celebrated as the “Green Revolution”);
  2. Conversion of all cropland to no-till (about one-third of US cropland is currently no-till after 40+ years of development and promotion of no-till systems);
  3. Conversion of 55 million acres of cropland to perennial biofuel crops (contrary to the factsheet’s claim that no cropland need be converted, the report calls for conversion of more than half as much cropland as currently grows corn);
  4. Recovery of 75% of all crop residues (which help build healthy soils).

Needless to say, the likelihood of any of these happening is slim, and the chance that they will all happen together in the next two decades is almost nil. The final, unstated, assumption is that economical means of converting cellulose to ethanol will be developed by 2030. Whether that will happen is still anybody’s guess. The claim that we can displace 30% of the nation’s gasoline consumption with biofuels is not supported by the DOE’s own report, which itself is based on unrealistic assumptions.

The next “myth” is that ethanol reduces fuel economy. Ethanol has about two-thirds the energy density of gasoline, so simple physics predicts that a car will go only two-thirds as far on a tank of ethanol as on a tank of gasoline. A recent industry-sponsored test of fuel economy in several cars running on a range of gasoline-ethanol blends confirmed that fuel economy tends to fall as ethanol content increases: In most cases the “myth” is true. The report has been celebrated by the ethanol industry, however, because of some interesting exceptions to the general rule: Some cars running on 20-30% ethanol blends got better mileage than would be expected from the fuel’s energy density (See figure below). The report offers no explanation for these interesting outliers.

Fusion Mileage

Highway fuel economy of a 2007 Toyota Camry running on blends ranging from pure gasoline to 65% ethanol. Purple line shows expected fuel economy, based on energy density of fuel blend. Diamonds show mean fuel economy for three test runs. In this case, a 30% ethanol blend gave significantly better fuel economy than would be expected, offering a 1% improvement over pure gasoline. Figure from Optimal Ethanol Blend-Level Investigation, 2007.

The final “myth” is that more energy goes into producing ethanol than it delivers as a fuel. This probably isn’t true, but it’s not far off. A range of peer-reviewed studies have found that producing ethanol from corn takes 60-95% as much energy as the ethanol delivers as fuel. The factsheet claims that ethanol can be made from corn using as little as 30% as much energy as the ethanol delivers. I wish I knew where they got that figure; I’ve looked all over for a study that can support it. There may be a net energy advantage to ethanol production from corn, but it’s not very big.

2 Comments leave one →
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