Wednesday, May 31, 2006

Move over Ethanol, meet Butanol

So I was just about to blog about this genetically modified bacterium Bacillus subtilis that can ferment glucose sugar directly to ethanol with a high (86%) yield over at Green Car Congress, when I read this comment at the bottom:

Ah, the wonders of genetic engineering. Wish they'd tried butanol instead, though.
Butanol, what the hell is butanol?

A quick Google search leads me to the Wikipedia entry and this Green Car Congress post which then lead me to, and this Yahoo 360 blog. I learn quite a bit.
Butanol (C4H10O) is a four-carbon alcohol in widespread use as an industrial solvent, with a US market size of some 370 million gallons per year at a price of about $3.75 per gallon (approximately $1.4 billion).

Butanol has many superior properties as an alternative fuel when compared to ethanol. These include:

  • Higher energy content (110,000 Btu’s per gallon for butanol vs. 84,000 Btu per gallon for ethanol). Gasoline contains about 115,000 Btu’s per gallon. But as butanol's octane rating is 25% higher than petrol's, increasing the compression accordingly could make 25% more power and >10% more mileage than petrol.
  • Butanol is six times less “evaporative” than ethanol and 13.5 times less evaporative than gasoline, making it safer to use as an oxygenate in Arizona, California and other states, thereby eliminating the need for very special blends during the summer and winter months.
  • Butanol can be shipped through existing fuel pipelines where ethanol must be transported via rail, barge or truck
  • Butanol can be used as a replacement for gasoline gallon for gallon e.g. 100%, or any other percentage. Ethanol can only be used as an additive to gasoline up to about 85% and then only after significant modifications to the engine. Worldwide 10% ethanol blends predominate.
It also has reduced emissions compared to gasoline:
With over 60,000 miles on his Buick, Butanol reduced Hydrocarbons emissions by 95%, Carbon Monoxide to 0.0%, and Oxides of Nitrogen by 37%.
Like ethanol, butanol can be created from corn and other biological sources. So, why then is all the buzz on ethanol? Until recently, the yield from ethanol was much greater than butanol. But now:
According to the inventor, David Ramey, his butanol process delivers about 42% more energy than ethanol for a given amount of feedstock, based on the higher energy content of butanol (some 25% greater than ethanol), plus the hydrogen.

Ramey’s fermentation only produces hydrogen, butyric acid, butanol and carbon dioxide, and doubles the yield of butanol from a bushel of corn from 1.3 to 2.5 gallons per bushel—equivalent to corn ethanol’s fermentative yield, but with higher heat content and hydrogen as a co-product.
If you can get a yield close to that of ethanol, but have a product that has more energy per gallon, can go down the gasoline pipes, can run in a car without modification, this is going to be a winner. Now I see why people would like to see research into genetic bacteria that can increase the yield of butanol. Definitely one to watch.

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