New CO2 Capturing Material Could Make Plants Cleaner

Scientists claim to have discovered a new compound that will capture damaging carbon dioxide from power plants using a technique commonly used to by the pharmaceutical industry to find new drugs.

The sponge-like material, called ZIF-69, promises to hold 60 times its volume in carbon dioxide, a greenhouse gas scientists say is primarily responsible for climate change.

The compound, along with twenty-four others like it, were discovered using so-called high-throughput screening, a massively parallel technique for testing chemicals. The new molecule could be used to capture the carbon dioxide generated by power plants when they burn coal, gas, or biomass.

"We're altering the environment irreversibly and something needs to be done or we might not have time to do anything about it," said Omar Yaghi, a professor of chemistry at UCLA, lead author of the paper. "If you can capture carbon dioxide that goes a long way towards a cleaner environment."

Capturing carbon dioxide requires that you can sort that CO2 molecule from other particles. That's a trick that has proven quite difficult. Previous efforts have required heat to trap the carbon dioxide particles. Heat requires energy, and that energy costs money. Making carbon capture more efficient could reduce the cost of the process and bring "cleanish" fossil fuel plants closer to reality.

Yaghi's paper, published online today in the journal Science, describes more than just the properties of one carbon dioxide capturing material. It defines a new process for creating materials with the properties that scientists want with unprecedented speed.

"The high-throughput method will get us into more and more complex structures and ultimately more useful materials," said Yaghi. "We were discovering so many new compounds that we asked the students to stop, so we can summarize our work and publish it."

Once they had a set of new compounds, the team of chemists went to work analyzing the properties using x-ray crystallography to define their shapes and topography. That's how they found the new high CO2 capacity material, ZIF-69.

ZIF-69 is like a carbon dioxide trap, allowing only CO2 in, while screening out molecules with different shapes. Under pressure, the compound allows the carbon dioxide in, but not back out. Then, when scientists decompress the material, the gas is released, allowing scientists to dump the captured CO2 into a storage system.

Such properties could make carbon capture substantially more efficient, although its efficacy under real conditions is unknown. Yaghi doesn't think the material will be ready for field tests for several years.

Franklin Orr, an earth sciences professor at Stanford, called the discovery "potentially quite significant," but noted that many of the details of how the material could be used in a carbon capture are still to come.

"They can be forgiven for not attacking every aspect of whether or not this is a commercially viable process in the first announcement of the finding," Orr said.

Orr noted that carbon dioxide capture is a major piece of the puzzle for making fossil fuel fired power plants cleaner. But carbon capture and sequestration is a multistep process. Once the carbon dioxide is captured, it has to be stored. Right now, engineers are planning to inject the CO2 into the ground in a process known as geological sequestration. Critics contend that such a strategy would require constant monitoring for leaks and would carry a very high level of risk.

These concerns lead environmental groups to deride carbon capture and sequestration as a pie-in-the-sky idea that entrenched fossil fuel companies promote to stave off the implementation of truly renewable technologies like solar and wind power.

"We are against coal carbon sequestration," said Daniel Kessler, a Greenpeace spokesperson. "The reality is that the technologies are going to require billions of dollars of investment. If we go that way, it's going to come at the expense of renewable energy."