Algae Could Provide One-Twelfth of the US Fuel Supply Without Stressing Water Supplies

Algae biofuels have for several years now seemed like they were just over the horizon of widespread commercial availability. Despite genuine large-scale potential, the horizon always seems to move just a bit farther away. One major concern has always been how much water growing algae takes. Indeed there have been some seriously harebrained proposals put forward to build algae biofuel plants in water-stressed areas.

Now a new study, published in Environmental Science and Technology, has come up with a good estimate of how much algae fuel the United States may be able to produce without overly stressing the nation's land and water resources.

How much pond scum will we be able to grow? 25 billion gallons a year, according to the DoE's Pacific Northwest National Laboratory. It's a large increase from the 4 billion gallons estimated in previous DoE analyses. Nevertheless, that's just one-twelfth of what's needed to get us off fossil fuels.

This is based on growing algae in large manmade ponds, just 6-15 inches deep, and not in the bioreactor tubes being developed by some companies—a good thing considering that growing algae in bioreactors is far more carbon-intensive than outdoor ponds. It also assumes that watersheds would be able to divert 5 percent of their water towards algae farming.

That may not sound like a lot at first, but consider that it's a similar amount that the EPA allows power plants to use for cooling. In total it would be about one-quarter of all the water currently used for agriculture in the nation. In the plus category, the total amount doesn't all have to come exclusively from freshwater, with salty groundwater and seawater also being suitable.

Set against a recent report from the US Geological Survey showing that we're depleting groundwater at the fastest rate on record, with agriculture and the energy industry being the prime culprits, the 5 percent figure seems, at least in many areas, optimistic.

Indeed the DoE report notes, "In arid areas such as the Desert Southwest, 5 percent is probably an overstatement of the amount of water available, but in many other areas that are a lot wetter, such as much of the East, it's likely that much more water would be available."

Where are the ideal conditions? DoE hydrologist Mark Wigmosta says the Gulf Coast and the Southeastern seaboard are prime algae-growing regions, noting, "The Gulf Coast offers a good combination of warm temperatures, low evaporation, access to an abundance of water, and plenty of fuel-processing facilities."

As is so often the case with algae biofuels, there's a lot of theoretical potential on tap. But unlocking that potential and bringing a product to market at a large scale, without water use issues, and at a price comparable to traditional fuels is a much taller task.