Algae growing in a heated pond at the University of Nevada test site. Credit: John Bebout |
Green algae, or common pond scum, have been held up as a renewable energy panacea. Highly refined strains of the fast-growing biomass can absorb CO2 straight from a power plant’s smokestacks, thrive in brackish water, and have the potential to yield far more biofuel per acre than corn does. One promising method of algae production involves nurturing the green goo in decidedly low-tech, open-air ponds. But the approach is plagued by a number of issues, including a fivefold drop in yields in cold winter weather.
Now a team from the University of Nevada has shown that simply cranking up the heat can avoid much of the seasonal production decrease. In late November, John Cushman and his colleagues inoculated an outdoor pond with a “starter” culture of halophytic (salt-loving) algae cells. Since then, they have circulated water heated by natural gas through the pond to keep it at a constant 29 °C (85 °F), despite subzero winter temperatures–an approach that simulates the use of heat from geothermal vents. Three weeks later, they harvested approximately five pounds of algae by dry weight–just half the yield anticipated for summer.
“This will allow us to move from a seasonal crop to optimal production 365 days a year,” says Cushman of the potential to combine algae production with geothermal heating. If the scheme proves a success, Nevada could be in a unique position to capitalize. The state is bathed in sunlight, has vast tracks of open desert, and sits on top of little-utilized saline aquifers and geothermal resources.
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