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Is biofuel from algae ‘green’ enough yet?

U. ARIZONA (US) — “Algal biofuels are not quite ready for prime time,” says Joel Cuello, co-author of a new report evaluating the alternative fuel’s current drawbacks and its potential.

Increasing the production of biofuels made from algae to meet at least 5 percent of US transportation fuel needs would place unsustainable demands on energy, water, and nutrients, according to the report from the National Research Council, or NRC.

However, these concerns are not a definitive barrier for future production, and innovations that would require research and development could help realize algal biofuels’ full potential.

“In other words, if scaled up today, the resources that have to go into production would not be sustainable,” says NRC committee member Joel Cuello, a professor in the University of Arizona department of agricultural and biosystems engineering.

“However, in our report we say that this not a show stopper, because there are technology combinations that can be designed and developed to make the production process more environmentally sustainable.”

For algal biofuels to contribute a significant amount of fuel for transportation in the future, the committee says, research and development would be needed to improve algal strains, test additional strains for desired characteristics, advance the materials and methods for growing and processing algae into fuels, and reduce the energy requirements for multiple stages of production.

What will it take?

Biofuels derived from algae and cyanobacteria are possible alternatives to petroleum-based fuels and could help the US meet its energy security needs and reduce greenhouse gas emissions such as carbon dioxide.

Algal biofuels offer potential advantages over biofuels made from land plants, including algae’s ability to grow on non-croplands in cultivation ponds of freshwater, salt water, or wastewater.

The number of companies developing algal biofuels has been increasing, and several oil companies are investing in them. Given these and other interests, the National Research Council was asked to identify sustainability issues associated with large-scale development of algal biofuels.

Cuello says if current methods were to be scaled up to meet the 5-percent goal, algal biofuel production would consume too much water, energy, and nutrients to be environmentally sustainable at this point. Additional concerns voiced in the report are the amount of land area needed for algae ponds and uncertainties in greenhouse gas emissions over the production life cycle.

“For example, to produce those 10 billion gallons of biofuel, you’d need about 33 billion gallons of water,” Cuello says. “That is a huge concern.”

“Resource consumption is very dependent on which technology components you combine and how you combine them to constitute a biofuel production pathway that is both environmentally sustainable and economically viable,” he explains.

Most of the current development involves growing selected strains of algae in open ponds or closed photobioreactors using various water sources, collecting and extracting the oil from algae, or collecting fuel precursors secreted by algae, and then processing the oil into fuel.

All the factors

“Our report brings awareness to address the concerns of making production not only commercially viable but environmentally sustainable,” he says. “In my opinion, you can’t divorce the two. As a matter of fact, most efforts aiming at lowering the production costs is to make the process more sustainable in terms of energy, water, and nutrient use.”

To produce 10 billion gallons of algal biofuels, 6 million to 15 million metric tons of nitrogen and 1 million to 2 million metric tons of phosphorus would be needed each year if the nutrients are not recycled, the report says. These requirements represent 44 percent to 107 percent of the total nitrogen use and 20 percent to 51 percent of the total phosphorus use in the US.

“The most effective way of addressing the challenges our report identified would be in an integrative approach addressing all the factors together—water, nutrients, energy, land use, and greenhouse-gas emissions,” Cuello says.

“There is the biological component—the algae, and the engineering aspect—cultivating, harvesting, and processing “ he adds, “and there has to be a conversation between the two. For example, you could have high-yielding algae that excrete the oil or its precursor, which would eliminate the need for harvesting the algae biomass in the first place.”

Similarly, by using wastewater from agricultural or municipal sources to grow and feed the algae, one could address both the water and the nutrient issue, and lower the energy demands in the process as well.

Cuello points out that the report should not come as a surprise to experts. “All of the federally funded research projects on algal biofuels are, at least indirectly, already working to address these concerns that we identified and explicitly stated because people have been aware of these challenges—though perhaps not with the degree of process integration that is required.”

The report was sponsored by the US Department of Energy to aid the agency in its decision-making process regarding sustainable algal biofuel development.

The National Academy of Sciences, National Academy of Engineering, Institute of Medicine, and National Research Council make up the National Academies. They are private and independent nonprofit institutions that provide science, technology, and health policy advice under an 1863 congressional charter.

Panel members, who serve as volunteers, are chosen by the academies for each study based on their expertise and experience and must satisfy the academies’ conflict-of-interest standards. The resulting consensus reports undergo external peer review before completion.

Source: University of Arizona

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