To stay within shrinking federal and state carbon emission allowances, companies in the U.S. and around the world are scrambling to take up innovative solutions and clean up or cut down carbon dioxide emissions.Amid ongoing gasification tests and carbon sequestration experiments, Massachusetts- based GreenFuel Technologies Corp. has been quietly conducting studies with several companies at their coal-fired plants to develop high-yield algae farm technologies.Its mission: to profitably recycle industrial carbon dioxide and produce feed, food, and fuel ingredients.

A few years ago, the concept would have been dismissed as ineffective, even though for some time now, algae have been used in wastewater treatment facilities to sop up toxic chemicals and at farms to capture fertilizers in runoff. As autotrophic organisms, algae can produce their own food from inorganic substances such as carbon dioxide and inorganic nitrogen. They are the fastest growing plants in the world, and they do not need clean water or land. And from several studies, GreenFuel has found that, as well as recycling atmospheric carbon dioxide, the entire biomass produced from algae can be used and that oil retrieved from the organism could be used as a renewable biofuel.

A company that began operations in 2001, GreenFuel has so far conducted successful pilot installations to recycle carbon dioxide at several plants, including the Redhawk and Four Corners plants owned by Arizona Public Service (APS), NRG’s D nkirk plant in New York and its Big Cajun plant in Louisiana, and a Sunflower Electric plant in Kansas. APS and GreenFuel partnered in 2005 and recycled 80% of daytime carbon dioxide emissions from APS’ 1,040-MW gasfired Redhawk Power Station using an algae bioreactor. The contraption was simple:

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An algae bioreactor system connected directly to the stack of APS’ 1,040-MW Redhawk Power Station successfully recycled greenhouse gases into renewable biofuels in 2006.

Carbon dioxide emissions coming out of the stack were directed through specially designed ipes and into specialized containers holding hungry algae. In the presence of sunlight, the algae consumed the carbon dioxide (Figure 6). GreenFuel then converted the carbon-rich algal biomass into transportation-grade biodiesel and ethanol. In 2007, APS announced that the team would attempt to replicate its success using emissions from APS’ coal-burning Four Corners Power Plant. Earlier that year, GreenFuel had teamed up with NRG to install the company’s Emissions-to-Biofuels process to capture NRG’s flue gas carbon dioxide.

GreenFuel indicated on its web site that both projects were successful, although it did not give any details.So will the use of algae bioreactors catch on as a commercial solution to the complex carbon dioxide emissions problem? “GreenFuel’s extensive economic analyses and cost estimates show that algae can be grown economically as a commercial product. Many estimates claiming that algae are not commercially viable use outdated economics for product values that are no longer valid, or assume use of initial generations of experimental technology that have since been upgraded,” the company says on its web site. “GreenFuel believes that ecological and energy issues are complicated and will require a variety of solutions—of which algae will be one.”

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