A team of researchers from the University of California, Berkeley; Lawrence Berkeley National Laboratory; and Exxon Mobil have developed a new material able to more effectively and inexpensively capture carbon dioxide emissions from natural gas power plants for eventual reuse or sequestration.
UC Berkeley announced the findings July 23 in advance of the paper's publication July 24 in the journal Science.
The material is a highly porous metal-organic framework, or MOF, which researchers modified with nitrogen-containing amine molecules. These materials are extremely porous, which means that an amount of the material equivalent to the weight of a paper clip has an internal surface area equal to that of a football field that can be used for adsorbing gases. Specifically, the researchers replaced diamines with tetraamines. The resulting material immediately outperformed their diamine-appended MOF when tested.
After capturing carbon dioxide, low-temperature steam can be used to flush the captured CO2 from the material for reuse or sequestration. The researchers found the material has a six-times-greater capacity for removing CO2 from flue gas than current amine-based technology. They also found it captures more than 90 percent of the CO2 emitted, and said it could cut the cost of capture in half.
Because this particular carbon-capture material is able to use low-temperature steam to regenerate the material for multiple uses, less overall energy is required in the process.
"For CO2 capture, steam stripping—where you use direct contact with steam to take off the CO2—has been a sort of holy grail for the field. It is rightly seen as the cheapest way to do it," senior researcher Jeffrey Long, UC Berkeley professor of chemistry and chemical and biomolecular engineering and senior faculty scientist at Berkeley Lab, said in a news release. "These materials, at least from the experiments we have done so far, look very promising."
The California Air Resources Board issued a study on carbon capture and sequestration, which was discussed at a Dec. 11 workshop. Natural gas-fired power generation plants and refineries were deemed ideal locations for such CCS technologies. The challenge for these types of projects is that they have been unable to overcome high upfront costs. Constructing a new facility with CCS—based on existing conventional technologies—could add between 25 and 90 percent to the price tag. Some facility operators currently using CCS technology are concerned that they will need to stop the process if reliable incentives are not available.
The researchers said that because there is not much of an existing market for captured CO2, power plants would likely either inject it back into the ground or sequester it. They also note there is a need for "the cost of scrubbing the emissions . . . to be facilitated by government policies, such as carbon trading or a carbon tax, to incentivize CO2 capture and sequestration, something many countries have already implemented."
Long's group at UC Berkeley's Center for Gas Separations, which is funded by the U.S. Department of Energy, discovered a chemically modified MOF six years ago.
The current work was funded by Exxon Mobil, which is working with both the Berkeley group and Long's startup, Mosaic Materials, on the development, scaling and testing of carbon-capture processes.