For its analysis, the team limited the amount of freshwater that could be drawn in any one area, assuming that no more than 5 percent of a given watershed's mean annual water flow could be used in algae production. That number is a starting point, says Venteris, who notes that it's the same percentage that the U.S. Environmental Protection Agency allows power plants to use for cooling.
"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," says Venteris.
"While the nation's Desert Southwest has been considered a possible site for vast algae growth using saline water, rapid evaporation in this region make success there more challenging for low- cost production," Venteris added.
Venteris and colleagues weighed the pluses and minuses of the various water sources. They note that freshwater is cheap but in very limited supply in many areas. Saline groundwater is attractive because it's widely available but usually at a much deeper depth, requiring more equipment and technology to pump it to the surface and make it suitable for algae production. Seawater is plentiful, but would require much more infrastructure, most notably the creation of pipelines to move the water from the coast to processing plants.
The team notes that special circumstances, such as particularly tight water restrictions in some areas or severe drought or above-average rainfall in others, could affect its estimates of water availability.'/>"/>
|Contact: Tom Rickey|
DOE/Pacific Northwest National Laboratory