Probing Question: Will algae become a fuel source?

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As corporations everywhere scramble to embrace environmental causes and "go green," ExxonMobil—the world's second largest publicly traded company—announced in July 2009 a $600 million investment that is, literally, green. The company, whose reputation was tarnished after the massive Exxon Valdez crude oil spill in 1989, will be producing algae-based fuel and hopes to be pumping out commercial amounts in five to ten years.

That's a long wait, but a realistic time frame, says Tom Richard, professor of agricultural and biological engineering at Penn State. He predicts that, primarily, "we'll be relying on fossil fuels for the next several decades, but algae-based fuels could be a great way to reduce our carbon footprint."

Algae include not only plant-like seaweeds, but also the microscopic organisms that are used to produce biofuels. According to Richard, the advantage of using algae to produce oil for fuel is, "they are photosynthetic, so they use carbon dioxide, CO2, as their carbon source. CO2 is a greenhouse gas, so some companies plan to set up algae-cultivating facilities near a power plant that burns fossil fuels. That way, they can direct the CO2 waste from the flues to the algae, instead of releasing it into the atmosphere."

Just like plants, algae use solar energy to turn CO2 into sugars or oils, and they are terrific photosynthesizers. Cultivating microscopic algae has the potential to yield up to 100 times more oil per acre than soybean, a common source of biofuels. Algae can be grown in open ponds or in closed tanks called photobioreactors.

"The challenge is not getting algae to grow in ponds," says Richard, "but to grow the algae that will produce the best feedstock for biofuels in a cost-effective way."

Researchers are working on achieving this goal, though, and Richard points to work by Wayne Curtis, professor of chemical engineering at Penn State, who develops the photobioreactor tanks in which algae grow.

In 2008, The National Science Foundation awarded half a million dollars to a team led by Curtis and Joseph Chappell of the University of Kentucky to collaboratively develop both process engineering and genetic engineering approaches to producing renewable, green-house-gas neutral biofuels using algae.

The project, "Development of a Sustainable Production Platform for Renewable Petroleum Based Oils in Algae," draws in part on Curtis's knowledge of bioreactor design and operational strategies to optimize hydrocarbon production. "We have already demonstrated that we can continuously grow algae at concentrations that are an order of magnitude higher than what can be done in a pond system," says Curtis, and "our oil production rates are many-fold higher than any that have been previously reported."

While he described the process of growing algae as straightforward, translating this technology to a commercial scale is like "inventing a new agriculture." Curtis states that "the question is not whether algae can produce fuels, the question is whether we can produce fuels from algae at a price that society can afford."

Whether algae are grown in ponds or photobioreactors, the typical extraction process involves collecting algal cells and breaking them to release their contents. Exxon is also working with algae that secrete oil that can be skimmed from the growth medium. After that, the oil is processed with methods that are similar to refining petroleum.

So, for the future, Richard says, "we need to start looking at CO2 as a resource instead of waste, and use solar energy to convert it to a fuel." He sees algal biofuels as just one element in a package of future fuel options.

Other options are electricity and hydrogen, which Richard sees as "exciting opportunities, especially for light-duty vehicles like automobiles." He points out that if you put an oil-based fuel of any kind in your car, "you're going to produce CO2 at the exhaust pipe. If you use electricity you don't have that waste, and if you use hydrogen, the exhaust is water, which is clean."

The important thing, says Richard, is "to get a more diverse set of fuels into our transportation system." In fact, algae-based fuels were used in a Continental Airline test flight in January 2009, and the U.S. Navy has contracted with the California company Solazyme for algae-derived fuel to test in their jets and ships. The future looks green, with not only electricity and hydrogen, but also algae-based fuels powering the cars, boats and planes of tomorrow.

Tom Richard Ph.D., Director, Penn State Institutes of Energy and the Environment, and Associate Professor of Agricultural and Biological Engineering, can be reached at trichard@psu.edu.

Wayne Curtis, Ph.D., Professor of Chemical Engineering at Penn State, can be reached at wrc2@psu.edu.

Last Updated October 14, 2006