Brewing Bigger, Better Biofuels
I’ve never sat down and thought about ethanol as a viable fuel source for the future until recently. Most of what I’ve picked up us from bits and pieces in the news, which rarely took a critical posture on the issues at hand.
Yes, some corn farmers are resistant to sell their crops, corn prices have increased dramatically, improper farming techniques could result in environmental problems, and some folks warn that converting food into fuel verges on insanity when millions around the world are starving to death.
Put all that aside. What about the fuel itself? How does it compare with gasoline? It sucks.
From the Transportation Energy Data Book of the US DOE, a file providing the energy densities of various fuels (wiki has this to say about it). When combusted, ethanol provides only ~65% of the energy per gallon compared to conventional gasoline. Methanol fares worse yet at ~48%. So you would need to combust a third more ethanol to achieve the same fuel mileage as the gas guzzling counterpart. But wait, all is not lost!
A recent report published in this week’s Nature (subscription required) outlines a novel method for producing higher chain carbon alcohols using the molecular geneticist’s favourite lab rat: Escherichia coli. The scientists were able to coerce E. coli to produce large pure quantities of isobutanol using various molecular techniques (which, I’ll be honest, I’m not at all privy to). Although I was unable to find the energy density and fuel efficiency of isobutanol, the author’s of the Nature paper assure the reader that, “Higher alcohols (C4 and C5), on the other hand, have energy densities closer to gasoline[…]”
Here are a few more words from the authors:
The strategy described above opens up an unexplored frontier for biofuels production, both in E. coli and in other microorganisms. This strategy takes advantage of the well-developed amino acid production technology, and channels the amino acid intermediates to the 2-keto acid degradation pathway for alcohol production[…]
[…]Specific strategies for producing other alcohols can be readily devised based on the synthetic pathways and metabolic physiology. These strategies can also be implemented in yeast or other industrial microorganisms.”
C o o l.