This article was published in Scientific American’s former blog network and reflects the views of the author, not necessarily those of Scientific American
SAN DIEGO—Researchers are continuing to develop strains of algae that yield a greater volume of oily compounds that can be processed into biofuels. But as more new and established companies examine how to scale up lab processes to commercial levels, scientists and engineers seem to be finding that standalone operations may not be economically viable. Co-locating algae farms with other industrial facilities could be one strategy that makes algal biofuels pay.
Typical algae strains use sunlight and water to convert carbon dioxide into lipids. Nutrients such as nitrogen and phosphorus can boost production, depending on the process. At prototype scales, supplying the "inputs" is not a problem, but at industrial scales, large quantities will be needed. Plentiful sources of CO2 and other nutrients are not readily available in many places, and even where they are, purchasing them at market prices could make algal biofuels too expensive.
The answer? Turn the waste from other industries into a resource for this new one, helping to solve the waste problem at the same time. With or without realizing it, various scientists speaking at the American Association for the Advancement of Science annual conference, which wraps up here today, were promoting the notion that algae operations should be located next to industries that can supply one or more of the nutrient streams.
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For example, algae production facilities could be located next to coal-fired power plants, which happen to be under increasing pressure and regulation to reduce CO2 emissions. Instead of spending money to sequester that carbon, say, underground, why not sell it, cheap, to an adjacent algae facility? Indeed, the Seambiotic algae plant in Tel Aviv, Israel, is tapping the flue gas of a coal plant next door.
Similarly, algae producers could locate near municipal wastewater treatment plants. "Cleansed" water that is usually deposited in rivers or other water bodies is generally safe for the environment, but still usually contains too much nitrogen or phosphorus for human consumption. Algae, however, thrive on those very compounds, and the alternative of purchasing them as fertilizer leaves a large environment footprint. Of course, the water itself is needed for algae production. A pilot plant run by Sunrise Ridge Algae in Austin, Tex., is piping in this resource from the Hornsby Bend wastewater plant there. Sunrise was hoping that enough CO2 could also be extracted from the wastewater, but the flow coming from Hornsby's anaerobic digesters was inconsistent, not a big surprise since the system was not built to supply CO2, per se.
These integration concepts can be taken further, noted Norm Whitten, CEO at Sunrise. When the algae are harvested for their lipids, the remaining plant matter can be processed into animal feed, or converted into a syrupy liquid he calls bioleum that can be burned somewhat like oil, enhancing the economics of an algae biofuel plant. Whitten also noted that cement plants generate enormous quantities of CO2—about one ton for every ton of cement produced-which could be a nutrient stream for algae plants. And waste heat from cement or power plants could be used to warm algae ponds, bags or tubes to accelerate growth. Connecting all these dots, Whitten noted that the Route 35 corridor in Texas is home to many cement plants, which could supply CO2 and waste heat, and is also home to oil refineries, which could process the bioleum.
Whether such combinations will make algal biofuel commercially competitive remains to be seen, but it seems likely that co-location will be a big factor making a sizeable industry possible.
Photo of bottled algae from iStockPhoto/Rob Broek
