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Lab: Algae Can Produce Fuel Equivalent to 17 Pct of Imports

Pond with algae (Higetiger/Flickr)A study by the Pacific Northwest National Laboratory (PNNL) in Richland, Washington estimates that growing algae for biofuel could realistically replace 17 percent of the nation’s imported oil for transportation. The research team from the lab, part of the U.S. Department of Energy, and other colleagues published its findings in the journal Water Resources Research (paid  subscription required).

Biofuel can be made with algae by extracting and refining lipids, a type of oil that algae produce as they grow. Biofuels are considered a desirable replacement source of transportation fuel because they can create fewer overall greenhouse gas emissions than fossil fuels. There are also a wide range of biofuel feedstocks, including algae, in the United States. Plus algae is not a human food source, like corn, thus its growth as biofuel feedstock would not have an immediate impact on food costs.

In 2009, slightly more than half of the petroleum consumed by the U.S. was from foreign oil. The Energy Independence and Security Act of 2007 set a national goal of producing 21 billion gallons from advanced biofuel sources, which equals about 17 percent of imported oil in 2008. Mark Wigmosta, PNNL hydrologist and lead author, analyzed the land, water, and weather conditions to see the extent to which algae could meet that goal.

Wigmosta’s team conducted an in-depth analysis that began with developing a national geographic database that covered topography, population, land use, and other information about the contiguous United States. That database contained information about the land area for every 100 feet throughout the U.S., a finer level of detail than previous research. These data allowed the team to identify available areas that are better suited for large-scale algae growth, such as those with flat land that isn’t used for farming, and away from cities or environmentally sensitive areas like wetlands or national parks.

The researchers then gathered 30 years of meteorological data to help determine the amount of sunlight that algae could realistically photosynthesize and the warmth the ponds growing the algae would become. When combined with a mathematical model to calculate growing potential under specific conditions, the weather data allowed Wigmosta and team to estimate the amount of algae that could realistically be produced hourly at each specific growing site.

The researchers found that using all available space, the U.S. could grow enough algae for biofuel to meet nearly half (48%) of U.S. oil imports. But that level of production would take a land area about the size of South Carolina, and require 350 gallons of water per gallon of biofuel produced. That amount of water comes to about one-fourth of total U.S. irrigation needs.

To reduce the impact of commercial algae growth on available farm land and water resources, Wigmosta’s team identified the regions that would use less water to grow algae — those with the nation’s sunniest and most humid climates. The best candidates were the Gulf Coast, the southeast Atlantic seaboard, and the Great Lakes, which together could reduce the amount of water needed by 75 percent and land use by 67 percent.

Even when confined to these optimal growing areas, say the researchers, the U.S. can still grow enough algae for biofuel to meet the 21 billion gallon goal — equivalent to 17 percent of petroleum imports — stated in the Energy Independence and Security Act.

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Photo: Higetiger/Flickr

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