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Biofuel from Pond Scum


Diesel is one of the world's most widely used fuels. Diesel fuel powers trucks, boats, trains and other engines. Unfortunately, it produces significant air-pollution: the foul-smelling fumes are linked to increased rates of cancer and asthma, and they add greenhouses gases to the atmosphere.

Oil-rich plants such as soy offer a cleaner energy alternative, known as biodiesel but Jim Sears says these food crops can't meet all our diesel needs. The Colorado-based entrepreneur says, even in America's bountiful croplands, farmers couldn't grow enough oilseed crops to meet demand. "Right now," he points out, "if we were to use all the normal sources we know about, such as canola oil, soy, things like this to make biodiesel, the industry thinks they could make 3.7 billion liters a year." That sounds like a lot, but Americans currently use 227 billion liters of diesel a year.

Fortunately, Sears says, an unconventional crop could produce 100 times more biodiesel per hectare than either canola or soy. It can thrive in places where other crops can't grow at all, and it only requires the equivalent of 5 centimeters of rain a year. It's algae, a small but familiar plant, usually seen as a green scum that forms on ponds or aquarium glass.

To demonstrate his crop's potential, Sears leads the way inside a former coal-fired electric power plant, now the Engines and Energy Conversion Laboratory at Colorado State University. CSU and Sears' small company, Solix Biofuels, have teamed up for this research.

Sears passes a two-story tall engine that may soon be running on his biodiesel, and heads to a quieter room where test batches of algae grow in glass beakers. The water ranges from pale yellow to soft Irish green, thanks to millions of microscopic algae.

Biologist Nick Rancis lifts a favorite specimen. "Here we have a species of green algae that grows in fresh water. As you can see, it grows very high density. You can't even see through it when you hold it up to the light." He says this strain produces enormous amounts of fat: up to 50 percent of its body weight. And while producing oil from soy or canola generally requires a three to five-month growing season, some algae are so prolific, over half a batch can be harvested for oil production every day. "They can double or triple overnight," Rancis says.

For industrial production, the researchers are designing enormous growing troughs, wider than two trucks side by side, as long as a football field, and grouped by the thousands around processing plants. In this way, Sears says, algae could supply all the U.S. diesel power on a fraction of the nation's farmland, just one percent of the 400 million hectares now under cultivation. "Actually we wouldn't have to convert any of our arable land," he observes. "We could use desert land to grow this algae. It doesn't require good soil. Just flat land, carbon dioxide and sunlight."

Carbon dioxide helps algae grow fast and fat, so the team plans to siphon it from fossil fuel power plant exhaust, which will reduce greenhouse gas emissions. And Sears says there are other ways to get the gas. "It would actually start with biomass such as switch grass or wood, where in some countries are the only type of fuel that they have anyway. In that case, the grass, the trees, the wood is pulling the carbon dioxide out of the air, then we burn it as fuel and feed the carbon dioxide to the algae." He stresses that no carbon will be added to the atmosphere during all these energy conversion steps, making biofuel from algae is a truly carbon-neutral technology. "It's essentially solar powered fuel."

To conserve water, the growing troughs are sealed. The algae grows under a clear plastic lid that allows in plenty of sunlight, but keeps the water the plants are floating in from evaporating. "It is about 1,000 times more efficient to produce fuel from algae than it is from an irrigated crop," Sears says. "There's enough water even in the desert from natural rainfall to support this technology."

Affordable biodiesel is an important focus of the research team, and Bryan Willson, who directs this Engines and Energy Conversion Lab, says the projections look promising. "We believe the technology could be cost competitive with $50 a barrel oil, which is basically where we are right now. Even last year, we were up to $70 a barrel."

Because building a vast new production system is an enormous undertaking, Sears predicts that it will be five to ten years before biodiesel from algae becomes commonplace. However, Eric Jarvis, a senior scientist at the National Renewable Energy Lab, cautions that it may take longer. "I wouldn't expect it to meet a large demand for diesel in that time frame, but I'm hoping to see some good demonstration projects in the next 5 to 10 years." He adds that in the last two years, interest in developing systems for biodiesel from algae has grown tremendously, and he gets phone calls every week from people trying to get into this area.

Whether it takes five years, a decade or a little longer, Jim Sears says he's certain that biodiesel from algae will become commonplace. He calls it "by far the most scalable and reasonable way to make biofuels in the future in an endlessly sustainable method."

As he considers that future, a train whistle sounds in the distance. "That train is the train that used to bring the coal to this power plant," he comments, adding "it is one of the future customers."

The National Renewable Energy Lab plans to step up their development of biodiesel from algae within the year, and they estimates that along with Colorado State and Solix Biofuels, roughly a dozen other groups around the world are developing similar projects, increasing the likelihood that someday soon, clean-burning algae biodiesel will be the fuel of choice for trucks, boats . . . and trains.