Do Algae-Based Biofuels Make Environmental or Financial Sense?

January 26, 2009 — There's probably just one thing that country singer Willie Nelson and Kansas Senator Sam Brownback have in common: a belief in the value of crop-based biofuels as a potential solution to our dependence on foreign oil, as an answer to global warming, and as the salvation of the American farmer.

But reality fails to live up to these claims. Today, even the most optimistic backers of crop-based biofuels admit that they will never be produced in sufficient quantities to replace hydrocarbons like oil and coal as our primary source of energy. And though hypothetically carbon-neutral — the carbon dioxide released when they are burned is equivalent to the atmospheric carbon dioxide used to produce them — crop-based biofuels typically require gasoline and fertilizer to produce, and both are derived from fossil fuel.

Lisa Colosi and Andres Clarens, both assistant professors of civil engineering at the University of Virginia, have teamed with U.Va. McIntire School of Commerce associate professor Mark White to explore algae as a source of biofuel and to place the assessment of its potential on a firm factual basis. Together, they are engaged in a project to demonstrate how the environmental and financial sustainability of algae-based biofuel production can be measured and optimized.

In theory, biofuel production is relatively straightforward. The fatty acids that plants produce as a byproduct of photosynthesis are separated and processed to create biofuel.

Instead of using a food crop, Colosi, Clarens and White chose a well-studied microalgae, Chlorella protothecoides, as a feedstock. Algae offer a number of advantages over other plants. They are highly efficient photosynthesizers, generating 30 times more oil than comparable amounts of crop-based biofuel feedstocks like corn or soybeans. They are also not particularly picky about their surroundings, flourishing in salt, fresh, and contaminated water.

"Algae can be grown in ponds anywhere, as long as there is abundant sunlight," Colosi said. "With algae, you don't have to sacrifice arable land that could be used for growing food."

The three researchers are experimenting with a variety of approaches that could increase the environmental benefits of this algae-based system. For instance, they are exploring the value of venting carbon dioxide–laden smokestack gas from a power plant into the algae pond. This arrangement might increase the yield of fatty acids while preventing much of the carbon dioxide from entering the atmosphere.

They also are considering adding different kinds of wastewater to the ponds to determine if the carbon compounds in the wastewater might increase fatty acid production.

Finally, they are studying the use of high-pressure variants of greenhouse gases in the refining process, supercritical carbon dioxide to separate fatty acids from the algal biomass and supercritical methane and supercritical carbon dioxide to help convert the fatty acids to fuel-grade diesel.

"We think we know how much it costs to create biofuel using algae," Clarens said. "We are trying to create a system that adds other sources of value."

Colosi, Clarens and White bring complementary skills to the project. Colosi is an environmental microbiologist who has studied the use of living organisms to decontaminate polluted water. Clarens, an aquatic chemist, is an expert in using high-pressure carbon dioxide chemistry to reduce pollutants generated by manufacturing. He also uses life cycle software, a computer-based modeling tool that calculates the environmental impacts of industrial processes. And White, a finance professor, has created financial models that put a price tag on the services, such as filtered water or clean air, that ecosystems provide.

Colosi and Clarens are responsible for exploring different approaches to biofuel production in the lab and for passing their data to White. White then uses financial modeling tools to estimate the value of their ecosystem services for the alternative they are investigating. The information that he produces, in turn, suggests ways in which Colosi and Clarens can further refine their techniques.

"There are a number of formal and informal mechanisms at the University that encourage this sort of collaboration," White said.

When Colosi and Clarens came to U.Va. as candidates for positions in the Engineering School, the hiring committee invited White to meet them. There is also research funding earmarked for collaboration. Their biofuels project is supported by a U.Va. Collaborative Sustainable Energy Seed Grant.

— By Charlie Feigenoff

This story originally appeared on Explorations online.