Algae fuels discussed at a U.S. Navy event: Algae cells close (inset).© Top: U.S. Navy, Inset: Solazyme
And algae thrive on carbon dioxide (CO2), which means that cultivation can function like a sink to reduce greenhouse gases. Some imagine algae cultivation around coal plants, sucking up CO2 before it can begin its deadly journey into the atmosphere.
Algae can also remove nitrogen and phosphorus from rivers and lakes, and convert agricultural runoff into "a much cleaner product," says Darzins.
There is one drawback, however: The effects of mass cultivation of genetically modified strains of algae are unknown. Darzins wonders about the "environmental impact of growing a certain species of algae" over thousands of square acres where it may release into the wild.
Growing algae for biofuels also poses some thorny technical problems. Grown in open sunlight, all sorts of undesirable organisms can get into the mix. Enclosed bioreactors are far more expensive, and the algae produce waste in the form of oxygen, poisoning themselves. Without further breakthroughs, "ways of harvesting and extracting algae are too expensive," says Darzins.
Still, Darzins is optimistic about the future. He foresees algal farms scaling up to a million square miles that can "start displacing 44 billion gallons of petroleum diesel" annually.
The company Solazyme’s algal biofuel production is achieved by using industrial wastes, sugar and wood chips to feed the algae. In this process, the algae take energy indirectly, from sunlight previously converted by other organisms. The algae start producing oil in a matter of days.
Overall, use of this biofuel "reduces greenhouse gas emissions by 85% compared to diesels from fossil oil," says Solazyme President Harrison Dillon.
Solazyme is ready to ship oil by the barrel to interested parties who can then test it, although "we are not yet selling it commercially," Dillon says. He believes his company is about "2½ years away from parity with $60- to $80-a-barrel oil."
While the total economic and environmental effects of large-scale algal production are unclear, it seems likely that algae will come to play a growing part in the nation’s energy supply.
ETHAN GOFFMAN is an environmental journalist and author of Imagining Each Other: Blacks and Jews in Contemporary American Literature (SUNY Press).