Scientists turning CO2 from coal-fired plants, algae into oil

By Jim Warren, General Science / Chemistry

They propose to employ algae to scrub carbon dioxide from the flue-gases of coal-fired power plants - of which Kentucky has many - and use the algae to produce an oil that could then be refined into fuel.

Carbon dioxide, or CO2, is the principal pollutant associated with global warming. But under UK's plan, algae would consume the power-plant CO2 as food, converting it into biomass from which algae oil could be removed and processed into biodiesel, jet fuel or similar products, researchers say.

Algae-based facilities to trap the CO2 would probably be located adjacent to coal-fired power plants in order to quickly receive and process their emissions.

"The reason algae is so interesting is that it can directly convert CO2 into biomass very quickly, more efficiently than anything else we know of," says Rodney Andrews, director of UK's Center for Applied Energy Research.

"Then, you basically squeeze the oil out of the algae and refine it as you would other natural oils."

The energy center is working on the project along with the UK College of Agriculture's Department of Biosystems and Agricultural Engineering. The state of Kentucky has provided more than $500,000 for the effort.

UK scientists say they hope to have a test facility operating within three to four years. If the algae-based system works, it could benefit both the electrical power industry and Kentucky's coal industry.

"The appeal is that if you have a power plant where you burn coal, and you capture the CO2 and use that to produce fuel with algae, you effectively become twice as efficient in the amount of energy achieved per ton of CO2 emitted," Andrews said.

As a first step in the research, Czarena Crofcheck, a biological engineer with the UK biosystems and agriculture engineering department, is searching for a strain of algae that would remove CO2 from power plant gases with the greatest efficiency.

In her search, Crofcheck watches over bubbling tanks called photo-bioreactors that contain various strains of algae in shifting shades of green. The darker the green, the more efficiently the algae in the tank is growing.

"These are my babies," she quips. "We're primarily interested in strains that grow quickly and consume CO2 very quickly."

Finding the right strain could take a while. Crofcheck notes that there are at least 50,000 species of algae.

And, as in many alternative energy projects, there are some problems to be overcome.

According to Andrews, capturing the carbon dioxide emitted from a 500-megawatt power plant would require 5,000 to 6,000 acres of ponds containing algae. To get around that, UK hopes to contain the algae in vessels that would operate more efficiently at much smaller size.

Expense is another issue. As of now, it costs $18 to $30 a gallon to produce algae oil, which then has to be refined into fuel.

But Andrews says producing fuel really is a secondary goal of the UK effort.

"The main idea is to get rid of the CO2 and then figure out what you do with the algae," he said.

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