‘Solar Sponge’ Sops Up Carbon, Squeezes It Out

Maybe a new way to do carbon capture, one that uses renewable energy in the form of sunlight, will help a technology that is falling well short of the high expectations laid out for it in many climate-change mitigation strategies.

The development comes out of Australia, where the national science agency CSIRO says its metal organic framework can capture CO2 that is then wrung out, somewhat like a sponge, by the power of simple exposure to UV light. The process is called dynamic photoswitching.

solar sponge

Researchers Richelle Lyndon and Matthew Hill with the equipment used to make “solar sponge.” (image via CSIRO)

“This is an exciting development for carbon capture because concentrated solar energy can be used instead of further coal-based energy to drive the process,” the lead researcher, Matthew Hill, said in a statement.

Post-combustion carbon capture is done now by running flue gas through special liquid solvents that are aborb the CO2. These liquids are then heated with superheated steam, a process that frees the CO2, which can then be stored. The Australian researchers say this is an energy-intensive process, consuming up to 30 percent of a power plants productive capacity. (There are also a couple of pre-combustion methods like Oxyfuel and integrated gasification combined-cycle getting play, but each has own separate issues.)

While the researchers compare their MOF to a sponge, it is important to note that they also say their MOF adsorbs CO2, distinct from absorbing the gas. That’s because the CO2 actually adheres to the surface of the MOF. The fact that one gram of the material has the surface area of a football field, the researchers say, is what allows that single gram to grab as much gas as it does.

The release mechanism is “light-responsive azobenzene molecules” impregnated in the MOF that cause the MOF to bend and flex, essentially squeezing out the CO2 in the process.

The International Energy Agency has been counting on carbon capture (known similarly as CCS, for carbon capture and sequestration) to contribute 7 gigatons out of 42 gigatons in CO2 reductions under “2DS,” a least-cost scenario for keeping the global average temperature from rising more than 2°C. But a recent report from the Global CCS Institute said the scenario necessary to achieve that “looks very unlikely”

Pete Danko is a writer and editor based in Portland, Oregon. His work has appeared in Breaking Energy, National Geographic's Energy Blog, The New York Times, San Francisco Chronicle and elsewhere.