Bioengineering Algae for Fuels

Last week, the New York Times reported that Exxon Mobil had teamed up with Craig Venter's Synthetic Genomics to work on the production of algae-based biofuels. As president and founder of Celera Genomics, Venter became a powerhouse of the biotech world in the 1990s, having spearheaded that company's effort to sequence the human genome in direct competition with the public Human Genome Project.

Venter and Synthetic Genomics, along with Exxon Mobil, could add a much-needed boost to the prospect of using algae instead of more conventional feedstocks for the production of biofuels. Indeed, the possibility that algae can be harnessed in this way is about the only reason to hold out much hope that biofuels will ever provide the world with large amounts of renewable transportation fuel that is environmentally benign to produce.

Let me try to defend that brash statement. For argument's sake, consider the production of biodiesel, a gallon of which can run a car virtually the same distance as a gallon of petroleum diesel. To keep things concrete, let's also say that the target is to have all of the diesel used as transportation fuel in the United States be biodiesel--according the Energy Information Administration, that's about 45 billion gallons a year. (Keep in the back of your mind, too, that this is but a small fraction of the gasoline Americans use: some 141 billion gallons a year.) 

If you made all that biodiesel from, say, rapeseed oil, how much land would it take? For that you need to know that an acre of rapeseed can generate about 100 gallons of biodiesel a year. So the math is simple: It would take 450 million acres--about a fifth of the all the land area in the United States. This is roughly equal to all the cropland in this country (406 million acres, according to the U.S. Department of Agriculture).

And that just satisfies the need for diesel fuel; it does nothing to put a dent in the petroleum used to make gasoline.

How environmentally friendly would it be, after all, to double the area under cultivation? Replacing vast areas of fallow farmland and forests with monoculture would be a high price to pay for making the use of diesel in our cars and trucks be carbon neutral.

And it probably wouldn't even do that, if you account for the carbon released from the soil in process. This argument is well quantified by Joseph Fargione of the Nature Conservancy and four colleagues in a report last year in the journal Science.

So what's an environmentally conscious biofuel advocate to do? One answer is to look for a feedstock that provides many more gallons per acre.

Which brings us back to the possibility of using algae. These single-celled organisms grow much, much faster than more familiar plants, allowing perhaps several thousand gallons of biodiesel to be produced from each acre. That's almost two orders of magnitude better than rapeseed. So, in theory, it would be possible to satisfy U.S. needs for diesel fuel using a reasonable amount of real estate. Indeed, you can even imaging displacing the petroleum used for gas this way without sacrificing too great a fraction of U.S. land. 

The problem is that nobody has yet figured out how to turn algae into fuel economically. 

Closed bioreactors, in which you can control the growing conditions, would be terribly costly at the scale required. Shallow open ponds are a lot cheaper, but they are susceptible to being taken over by algal species other than the one was intended to be grown. Researchers ran into this problem in the 1980s when they set up demonstration facilities for growing algae as part of the U.S. Department of Energy's Algal Species Program.

Here's where I suspect that modern biotechnology can give this enterprise a real boost. Maybe molecular biologists will be able to engineer an oil-rich algal species that grows happily under conditions that would kill off the competition--say, a Monsanto-approved "Roundup Ready" species of algae that can thrive in water laced with this herbicide. Okay, maybe Roundup is too nasty to want to spread over an area the size of a small state. But perhaps some other tactic can be used, say, the absence of a key nutrient that only the genetically engineered species can compensate for. 

I don't claim to know what plant genetic engineers might pull out of their sleeves in the quest to make algae into a practical feedstock for biofuels, but I suspect that their contribution will prove larger than what the mechanical engineers working on closed bioreactors can come up with. That's why I'm excited to hear that Venter has this problem in his sights. Maybe, just maybe, he or others like him will finally figure out how to produce vast amounts of biofuel without doing great harm to the environment. Until then, though, it'll be strictly petroleum-based fuels for me.


Photo of algal bioreactor by Umberto Salvagnin, used under Creative Commons Attribution 2.0 license.

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