Green Design

Algae as a High-Temperature Hydrogen Source

A team of researchers from the University of Tennessee, Knoxville and Oak Ridge National Laboratory have found that the inner machinery of photosynthesis can be isolated from certain algae and, when coupled with a platinum catalyst, is able to produce a steady supply of hydrogen when exposed to light.

Barry Bruce, a professor of Biochemistry and Cellular and Molecular Biology at UT Knoxville and leader of the team, notes that we already get most of our energy from photosynthesis, indirectly.

The fossil fuels of today were once, millions of years ago, energy-rich plant matter whose growth was also supported by the sun via the process of photosynthesis. There have been efforts to shorten this process, namely through the creation of biomass fuels that harvest plants and covert their hydrocarbons into ethanol or biodiesel.

“Biofuel as many people think of it now — harvesting plants and converting their woody material into sugars which get distilled into combustible liquids — probably cannot replace gasoline as a major source of fuel,” said Bruce. “We found that our process is more direct and has the potential to create a much larger quantity of fuel using much less energy, which has a wide range of benefits.”

The team's method cuts out two large steps involved with using plants’ solar conversion abilities. The first is the time required for a plant to capture solar energy, grow and reproduce, then die and eventually become fossil fuel. The second is energy - in this case the substantial amount of energy required to cultivate, harvest, and process plant material into biofuel. Bypassing these two options and directly using the plant or algae’s built-in solar system to create clean fuel can be a major step forward.

Other scientists have studied the possibility of using photosynthesis as a hydrogen source, but have not yet found a way to make the reaction occur efficiently at the high temperatures that would exist in a large system designed to harness sunlight.

Bruce and his colleagues found that by starting with a thermophilic blue-green algae, which favors warmer temperatures, they could sustain the reaction at temperatures as high as 55 degrees C (131 degrees F). That is roughly the temperature in arid deserts with high solar irradiation, where the process would be most productive. The team also found the process was over 10 times more efficient as the temperature increased.

(UT Knoxville)