April 6, 2009

Pressure pumps up algae biofuel

Put water under enough pressure and you can turn algae into methane fuel and at the same time pull carbon dioxide out of the atmosphere.

Supercritical water -- water heated beyond 374 degrees Celsius and pressurized beyond 218 atmospheres -- is a powerful solvent. Researchers have been exploring ways of using supercritical water to turn biomass into fuel over the past decade.

The proposed process uses supercritical water to turn microalgae into methane and concentrated carbon dioxide. Because the process separates out and stores carbon dioxide, it ensures that burning the methane fuel releases less carbon dioxide than the algae absorbs from the atmosphere.

The process uses the metal ruthenium to catalyze the reaction. The process turns 60 to 70 percent of the algae's heating value to methane. A material's heating value is the amount of energy it releases when burned.

Methane can be used in place of natural gas to power vehicles, generate electricity and provide heat. The concentrated carbon dioxide can be sequestered underground or under the ocean.

The closed loop system would use nutrient byproducts of the process and some of the carbon dioxide to feed the microalgae. Some of the methane would be used to heat the system's reactor.

Research paper:
Catalytic Gasification of Algae in Supercritical Water for Biofuel Production and Carbon Capture
Energy & Environmental Science, published online March 20, 2009

Researchers' homepages:
Samuel Stucki
Frédéric Vogel
Christian Ludwig
Gabriela Anca Haiduc
Martin Brandenberger

Related stories and briefs:
Algae-to-hydrogen system closes the loop -- related research
Engineered algae spreads the light -- related research

Back to ERN April 6, 2009



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