by DeAnander
Thu Jul 14th, 2005 at 07:58:33 PM EST
At Cornell, a skeptical voice is raised about optimism wrt fuel substitutability:
Turning plants such as corn, soybeans and sunflowers into fuel uses much more energy than the resulting ethanol or biodiesel generates, according to a new Cornell University and University of California-Berkeley study.
"There is just no energy benefit to using plant biomass for liquid fuel," says David Pimentel, professor of ecology and agriculture at Cornell. "These strategies are not sustainable."
[Full Text]
at Cornell, a skeptical voice is raised about optimism wrt substitutability:
Turning plants such as corn, soybeans and sunflowers into fuel uses much more energy than the resulting ethanol or biodiesel generates, according to a new Cornell University and University of California-Berkeley study.
"There is just no energy benefit to using plant biomass for liquid fuel," says David Pimentel, professor of ecology and agriculture at Cornell. "These strategies are not sustainable."
[...]"The government spends more than $3 billion a year to subsidize ethanol production when it does not provide a net energy balance or gain, is not a renewable energy source or an economical fuel. Further, its production and use contribute to air, water and soil pollution and global warming," Pimentel says. He points out that the vast majority of the subsidies do not go to farmers but to large ethanol-producing corporations.
Pimentel's work is discussed again here
Neither increases in government subsidies to corn-based ethanol fuel nor hikes in the price of petroleum can overcome what one Cornell University agricultural scientist calls it a fundamental input-yield problem: It takes more energy to make ethanol from grain than the combustion of ethanol produces.
At a time when ethanol-gasoline mixtures (gasohol) are touted as the American answer to fossil fuel shortages by corn producers, food processors and some lawmakers, Cornell's David Pimentel has taken a longer range view. He laments growing of corn for an energy-inefficient process that yields low-grade automobile fuel amounts to unsustainable, subsidized food burning as abuse of precious croplands. Pimentel, who chaired a U.S. Department of Energy panel that investigated the energetic, economics and environmental aspects of ethanol production several years ago, subsequently conducted a detailed analysis of the corn-to-car fuel process.
According to him, an acre of U.S. corn yields about 7,110 pounds of corn for processing into 328 gallons of ethanol. But planting, growing and harvesting that much corn requires about 140 gallons of fossil fuels and costs $347 per acre. Thus, even before corn is converted to ethanol, the feedstock costs $1.05 per gallon of ethanol.
The energy economics get worse at the processing plants, where the grain is crushed and fermented. As many as three distillations steps are needed to separate the 8 percent ethanol from the 92 percent water. Additional treatment and energy are required to produce the 99.8 percent pure ethanol for mixing with gasoline. Adding up the energy costs of corn production and its conversion to ethanol, 131,000 BTUs are needed to make 1 gallon of ethanol.
One gallon of ethanol has an energy value of only 77,000 BTU. About 70 percent more energy is required to produce ethanol than the energy that actually is in ethanol. In making 1 gallon of ethanol, there is a net energy loss of 54,000 BTU. Ethanol from corn costs about $1.74 per gallon to produce, compared with about 95 cents to produce a gallon of gasoline. Therefore, why fossil fuels, not corn are generally used to produce ethanol.
Most economic analyses of corn-to-ethanol production overlook the costs of environmental damages, which should add another 23 cents per gallon. Corn production in the U.S. erodes soil about 12 times faster than the soil can be reformed, and irrigating corn mines groundwater 25 percent faster than the natural recharge rate of ground water. The environmental system in which corn is being produced is being rapidly degraded. Corn should not be considered a renewable resource for ethanol energy production, especially when human food is being converted into ethanol.
The approximately $1 billion a year in current federal and state subsidies (mainly to large corporations) for ethanol production are not the only costs to consumers, subsidized corn results in higher prices for meat, milk and eggs because about 70 percent of corn grain is fed to livestock and poultry in the United States Increasing ethanol production would further inflate corn prices. In addition to paying tax dollars for ethanol subsidies, consumers would be paying significantly higher food prices in the market place." Apart from this, if all the automobiles in the United States were fueled with 100 percent ethanol, a total of about 97 percent of U.S. land area would be needed to grow the corn feedstock. Corn would cover nearly the total land area of the United States.
I would offer one caveat: Pimentel's study is based on the assumption of current insanely petro-intensive farming practise. The study does not mention what the energy math would look like using sustainable agricultural methods, nor does it examine canola as opposed to soya oil or corn ethanol. He also skips any analysis of non-corn ethanol -- sugar cane or beet ethanol for example. Less fossil-intensive farming methods might yield better payback rates, but nothing -- even in rosy scenarios -- solves the fundamental problem of a psychotically inefficient transport paradigm.
Here is some quantitative chitchat from the carfree list back in 2001:
The following webpage provides a table which estimates oil yield per agricultural land area:
http://journeytoforever.org/biodiesel_yield.html
From that table, Canoloa (rapeseed) a dryland crop may be estimated as yielding upwards of 127 gallons per US acre.
Petroleum Diesel has an energy content of approximately 138,000 Btu/gal. Gasoline has 124,300 Btu/gal. LP gas has 92,300 Btu/gal, when stored at 4.25 lbm/gal. Cold pressed, not converted to biodiesel, Canola oil has 121,904 Btu/gal. Thus the same Canola cooking oil as is found in many kitchens has 12% less energy per volume than Petroleum Diesel, 2% less energy per volume than gasoline, and approximately 25% more energy content per unit volume than LP gas.
My very rough estimate based on petroleum fuel use per acre in dryland wheat farming suggests that agricultural machinery could consume less than 20 gallons of Canola oil to plant and harvest enough seed to extract 127 gallons of oil. Ethanol from grain crops doesn't even come close to exhibiting the same favorable production use to product yield ratio.
Used as a utility bicyclist's food vegetable oils such as from Canola or Olive pits have sufficient calories per volume to suggest a "fuel" consumption rate from 900 miles per gallon to over 2,000 miles per gallon, depending on the bicycle's and cyclist's performance characteristics. This frugal resource utilization is primarily a direct consequence of a bicycle's mass which is scaled in proportion to the rider and use. [John Snyder]
Taking Snyder's figures for the moment at face value, he claims a profit of 107 gallons per acre in canola oil. If we subtract 12 percent for the energy density difference between canola and petrodiesel we get a diesel equivalent of 94 gallons/acre. How does that compare with current agricultural acreage and current fuel consumption for transport?
The EPA estimates over 1 billion gallons of petrodiesel consumed per annum in idling alone. This (PDF!) paper offers 1999 fuel consumption figures for the US vehicle fleet of 125 billion gallons of gasoline and 35.7 billion gallons of diesel. If we believe the somewhat optimistic canola scenario above, we would need about 379,787,250 acres (380 million acres) under canola to meet our diesel habit alone.
How many acres do we actually have in the US under various crops? Answers can be found at the fascinating ag statistics sites. I find these maps really interesting, but the real numbers are in another blasted PDF file. In 2004: 81 million acres under corn, 75 million acres under soya, 60 million acres under wheat, 14 million acres under cotton. For a total of only 230 million acres. In other words we could replace all agricultural activity in the US in corn, soya, wheat and cotton with canola plantings, and still not reap enough canola to replace only the diesel component of our transport fuel consumption.
Please, check my numbers!
But my point is that unless I am off by a couple of orders of magnitude, there is no way -- even at a net energy gain which the Cornell study suggests is unlikely -- that the US vehicle fleet and transport model in its current form [defended recently by asdf as a "good standard of living" indicator in which people will resist any cutbacks] cannot possibly be fueled by the amount of arable land available in the US. All food production would have to cease and agricultural activity be dedicated solely to feeding the transport model.
One reason for this energy gluttony is the gross oversizing of ICE vehicles for the job they do, and unreasonable, spoilt-aristo expectations of "performance" (i.e. moving that enormous mass quickly off the mark and defying aerodynamics to shove high-profile boxy vehicles along the roads in excess of 45 mph). The difference in fuel efficiency between a worst-case Hummer H2 and a best-case cyclist could be a factor of 100. Surely it makes more sense to grow human food to feed cyclists at 100x the efficiency than to grow fuel-optimised crops to feed Hummer H2s...
Anyway, some more numbers to ponder.
