My ideal microbe for biofuel production would consume garbage, excrete gasoline, and die if it escapes into the wild. Excretion of longer chain hydrocarbons like gasoline would enable a less energy-intensive separation, because the product would phase out of water. LS9 is exploring this sort of pathway via microbes, and Virent is trying to do the same thing catalytically.
It is quite a challenging problem, but should be technically viable. And a company that can achieve an edge in this space could really dominate the biofuels arena. As I have said, it is difficult, but Holy Grail research.
Today a new and quite novel approach was announced in the Journal of the American Chemical Society:
Professor Christopher Voigt and his team at UC San Francisco are researching a multi-pronged approach to the problem. They are using a bacterium that was discovered at a landfill in France to consume cellulose and convert it to acetate. (This was exactly what I did in graduate school, except we were using microbes from the stomachs of cattle to convert cellulose into acetate. After all, the stomach of a cow is a cellulose conversion factory).
Once acetate is produced, Professor’s Voigt’s team utilized a yeast to convert the acetate into a methyl halide. The beauty of this approach is three-fold. First, the acetate poisons the bacterium as the concentration builds, but the yeast prevents that by consuming it as it is produced. Second, the product comes off as a gas, simplifying the separation of the product from the aqueous solution. Finally, methyl halides can be converted into gasoline catalytically.
So what’s the catch? Generally the yields and reaction rates via these sorts of approaches are too low to be economically viable. This means that even if you have something that phases out of solution (or a gas that bubbles out in this case) the reactor(s) may need to be enormous to produce commercial quantities of product. Another potential issue here is the possibility that other gases are produced along with the methyl halides, potentially requiring a separation after all. Finally, methyl halides have never been turned into gasoline at large scale. If the economics were attractive, we would probably be using this process to convert natural gas into gasoline.
Still, this is a very interesting approach and an avenue that appears to be worthy of much more research.
Finally, hat tip to a reader for bringing this story to my attention earlier today.