20 October 2010

Turning Algae into Energy

Just three years ago, Colorado-based inventor Jim Sears shuttered himself in his garage and began tinkering with a design to mass-produce biofuel. His reactor (plastic bags) and his feedstock (algae) may have struck soybean farmers as a laughable gamble. But the experiment worked, and today, Sears' company, Solix Biofuels in Fort Collins, is among several startups betting their futures on the photosynthetic powers of unicellular green goo.

The science is simple: Algae need water, sunlight and carbon dioxide to grow. The oil they produce can then be harvested and converted into biodiesel; the algae's carbohydrate content can be fermented into ethanol. Both are much cleaner-burning fuels than petroleum-based diesel or gas.

The reality is more complex. Trying to grow concentrations of the finicky organism is a bit like trying to balance the water in a fish tank. It's also expensive. The water needs to be just the right temperature for algae to proliferate, and even then open ponds can become choked with invasive species. Atmospheric levels of CO2 also aren't high enough to spur exponential growth.

Solix addresses these problems by containing the algae in closed "photobioreactors"—triangular chambers made from sheets of polyethylene plastic (similar to a painter's dropcloth)—and bubbling supplemental carbon dioxide through the system. Eventually, the source of the CO2 will be exhaust from power plants and other industrial processes, providing the added benefit of capturing a potent greenhouse gas before it reaches the atmosphere.

Given the right conditions, algae can double its volume overnight. Unlike other biofuel feedstocks, such as soy or corn, it can be harvested day after day. Up to 50 percent of an alga's body weight is comprised of oil, whereas oil-palm trees—currently the largest producer of oil to make biofuels—yield just about 20 percent of their weight in oil. Across the board, yields are already impressive: Soy produces some 50 gallons of oil per acre per year; canola, 150 gallons; and palm, 650 gallons. But algae is expected to produce 10,000 gallons per acre per year, and eventually even more.

"If we were to replace all of the diesel that we use in the United States" with an algae derivative, says Solix CEO Douglas Henston, "we could do it on an area of land that's about one-half of 1 percent of the current farm land that we use now."

Solix plans to complete its second prototype by the end of April and to begin building a pilot plant this fall. That plant will take advantage of CO2 generated from the fermentation and boiler processes of New Belgium Brewery, also in Fort Collins. The company's initial target is to be competitive with biodiesel, which historically sells for about $2 per gallon, wholesale. They believe they can reach this goal within a few years, and are ultimately aiming to compete with petroleum.

John Sheehan, an energy analyst with the National Renewable Energy Laboratory (NREL) in Golden, Colo., believes these goals are within reach. "There is no other resource that comes even close in magnitude to the potential for making oil," says Sheehan, who worked in the lab's algae program before it was shut down by the Department of Energy. One of algae's great strengths, Sheehan adds, is its ability to grow well in brackish water. In the desert southwest, where much of the groundwater is saline and unsuitable for other forms of agriculture, algae can proliferate.

GreenFuel Technologies Corp., based in Cambridge, Mass., is focused on cultivating algae that can produce high yields of both biodiesel and ethanol. There are more than 100,000 strains of algae, with differing ratios of three main types of molecule: oils, carbohydrates and protein. Strains of algae high in carbohydrates as well as oils produce starches that can be separated and fermented into ethanol; the remaining proteins can be turned into animal grains. GreenFuel hopes its pilot plant will see initial yields of 8000 gallons of biodiesel and 5000 gallons of ethanol per acre of algae.

The main focus now, says Cary Bullock, GreenFuel's president and CEO, is figuring out "how to grow algae fast enough and cheap enough that it makes sense economically. That's not easy to do."

With the science well in hand, the degree to which algae-based biofuels can replace petroleum—or the limited acreage of traditional feedstocks—rests upon that bottom line. Once the technology hits the ground, will a commercial-scale facility be on par with petroleum? Says Bullock: "You don't know until you've actually built the thing."

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