Researchers have developed porous materials that can soak up 80 times their volume of carbon dioxide, offering the tantalizing possibility that the greenhouse gas could be cheaply scrubbed from power-plant smokestacks. After the carbon dioxide has been absorbed by the new materials, it could be released through pressure changes, compressed, and, finally, pumped underground for long-term storage.
Such carbon dioxide capture and sequestration could be essential to reducing greenhouse-gas emissions, especially in countries such as the United States that depend heavily on coal for electricity. The first stage, capturing the carbon, is particularly important, since it can account for 75 percent of the total costs, according to the Department of Energy.
The new materials, described this week in Science, were created by researchers at UCLA led by Omar Yaghi, a chemist known for producing materials with intricate microscopic structures. They absorb large amounts of carbon dioxide but do not absorb other gases.
Techniques already exist for capturing carbon dioxide from smokestacks, but they use large amounts of energy–15 to 20 percent of the total electricity output of a power plant, according to one estimate, Yaghi says. That is because existing materials, known as amines, need to be heated to release the carbon dioxide they’ve absorbed. Indeed, capturing and compressing carbon dioxide through these existing methods can add 80 to 90 percent to the cost of producing electricity from coal, says Thomas Feeley, a project manager at the National Energy Technology Laboratory.
Feeley says that Yaghi’s materials “compare favorably” with other experimental materials that absorb carbon dioxide that are being developed to help bring down these costs. Yaghi says that his materials could lower costs considerably since they use less energy, although exactly how much will require testing the materials at power plants.
Beyond being potentially useful in smokestacks, the materials could be employed in coal gasification plants. In these plants, coal is first processed to produce a mixture of carbon dioxide and hydrogen gas. The hydrogen is then used to generate electricity. The carbon dioxide could be captured using a solvent that increases energy consumption. But as in the smokestack-based process, the new UCLA materials could require less energy.