Mr. Deutch, director of energy research and undersecretary of Energy in the Carter administration, and director of the CIA and deputy secretary of Defense in the first Clinton administration, is a professor of chemistry at MIT.
A survey of biofuel issues by John Deutch in the Wall Street Journal. He concludes US-grown ethanol might contribute 1 to 2 million BPD equivalent from 25 million acres of switchgrass [roughly 3% of USDA classified crop, range and pasture land].
Deutch is careful in this op-ed to describe some of the unknowns, and to characterize his enthusiasm for an unproven biotech enzyme conversion process:
…This approach merits genuine enthusiasm, especially as one can imagine engineering an organism to produce enzymes that (a) break down the cellulosic material, as well as (b) more efficiently ferment the sugars into ethanol. Realizing this exciting prospect will not be easy…
He also briefly cover some of the thermodynamics of current corn-based ethanol production [estimates on the net product vary, from negative to 50% more energy output than input]. Deutch assumes about 30%. Good – so the corn -> ethanol option is good for corn states, but not good policy.
Missing from the analysis are these assessments:
1) The impact on the water supply.
2) The impact on the soils [correctable to a degree with fertilizers, but then you have downstream effects].
Personally, I would favor policies that do not make the future war over water either worse or sooner.
President Bush has made the welcome point that the U.S. needs “to move beyond a petroleum-based economy,” and has lent his support to the need to develop energy from biomass, which refers to all bulk plant material. This is popular with the public and also enjoys significant support in Congress. Unfortunately, congressional subsidies for biomass are driven by farm-state politics rather than by a technology-development effort that might offer a practical liquid fuel alternative to oil. Meanwhile, major oil and chemical companies are evaluating biomass and investors are chasing biomass investment opportunities. But how much of this is practicable?
Biomass can be divided into two classes: food-crop and cellulosic. Natural enzymes can easily break down food-crop biomass such as corn to simple sugars, and ferment these sugars to ethanol. Cellulosic biomass — which includes agricultural residues from food crops, wood and crops such as switch grass — cannot easily be “digested” by natural enzymes.
Today, we use corn to produce ethanol in an automobile fuel known as “gasohol” — 10% ethanol and 90% gasoline. Generous federal and state subsidies, largely in the form of exemption from gasoline taxes for gasohol, explain the growth of its use; in 2005, over four billion gallons of ethanol were used in gasohol out of a total gasoline pool of 120 billion gallons. Politicians from corn-states and other proponents of renewable energy support this federal subsidy, but most energy experts believe using corn to make ethanol is not effective in the long run because the net amount of oil saved by gasohol use is minimal.
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As for the land required to support significant biofuel production from a dedicated energy crop, switch grass offers a basis for estimation. It grows rapidly, with an expected harvest one or two years after planting. Ignoring crop rotation, an acre under cultivation will produce five to 10 tons of switch grass annually, which in turn provides 50 to 100 gallons of ethanol per ton of biomass. Thus the land requirement needed to displace one million barrels of oil per day (about 10% of U.S. oil imports projected by 2025), is 25 million acres (or 39,000 square miles). This is roughly 3% of the crop, range and pasture land that the Department of Agriculture classifies as available in the U.S. I conclude that we can produce ethanol from cellulosic biomass sufficient to displace one to two million barrels of oil per day in the next couple of decades, but not much more. This is a significant contribution, but not a long-term solution to our oil problem.
Rising real prices of oil and natural gas reflect in part the progressive decline in low-cost reserves, and signal the wisdom of preparing now for a long transition from our petroleum-based economy. Almost certainly, future economies will exploit all possible technology options for replacing petroleum-based liquid fuels, especially technologies that do not produce net carbon dioxide, the major greenhouse gas. Biomass should, properly, be considered along with nuclear power and coal conversion with carbon capture and sequestration as important options for future energy supply.
A no-regrets policy option is to eliminate the tariffs on imported ethanol, as Brazil can convert from sugar cane at a favorable output/input ratio [8:1 {?} instead of US 1.30:1]. Maybe no-regrets isn’t apt, as then it is Brazil’s water and soil depletion.
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