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Copyright © 2016 Albuquerque Journal
Researchers at Sandia National Laboratories and the University of New Mexico have developed a microscopically thin filter that could revolutionize the way power plants remove carbon dioxide – the major gas responsible for global warming – from smokestack emissions.
Every day, coal- and natural gas-fired electric power plants belch out millions of tons of greenhouse gases. The most plentiful of those gases is carbon dioxide, which accounts for roughly 80 percent of such emissions, according to the U.S. Environmental Protection Agency.
Researchers say they have created a more efficient, and far cheaper, way of removing C02 from flue gases.
If the new filter, which is still in the research phase, works as well on an industrial scale, it will be a game-changer, said Susan L. Rempe, a computational biophysicist at Sandia National Laboratories.
The process, Rempe said, has the potential to save the U.S. coal industry $90 billion a year compared with conventional technology.
“If we applied it to a single coal-fired power plant, then over one year we could avoid CO2 emissions equivalent to planting 63 million trees and letting them grow for 10 years,” she said.
There are about 600 coal- and natural gas-fired power plants in the U.S., including the coal-fired San Juan Generating Station near the Four Corners, which supplies about one-third of the state’s electricity.
Removing carbon dioxide from those power plants’ smoke stacks is expensive and requires about one-third of their electrical output, said Rempe.
“Most power plants don’t remove pollutants because the current state of the art is extremely expensive,” she said.
The San Juan power plant, operated by Public Service Company of New Mexico, has no system for removing CO2, said company spokesman Pahl Shipley.
Plants that do remove carbon dioxide from flue gases employ an amine scrubbing system that requires high pressure and high temperatures to remove and capture CO2. Such systems, Rempe said, are massive.
“You’ve got to attach a factory to the power plant in order to capture the CO2,” she said. Those systems are very expensive to build and operate, and they employ toxic chemicals that pose an environmental problem.
Industry, government and scientists have long sought a better way of removing CO2 from power plant emissions.
The Department of Energy is pushing for the development of new technologies that capture at least 90 percent of CO2 emissions at a cost-effective $40 per ton by the year 2025.
One approach to reaching that goal is to develop a filter that can efficiently remove CO2 from plant emissions.
But filters tend to be bulky, nonspecific in what chemicals they capture, and hard to maintain.
The key to efficient filtering, Rempe said, is to move gases through the filter quickly, and removing only the gases you want removed. That requires a very thin, very selective filter.
While Rempe and her team had been studying an enzyme that greatly speeds up the chemical reactions involved in CO2 capture, Ying-Bing Jiang, a chemical engineering research professor at the University of New Mexico, was developing a liquid membrane that is 2,000 times thinner than a human hair. Sandia and UNM teams had already worked together on membrane projects, so combining the two technologies was a fairly smooth transition, Rempe said.
But there was a major problem: Jiang’s membrane is extremely fragile, more fragile than a soap bubble.
Sandia researcher Jeff Brinker and Jiang developed a flexible “frame” for the liquid membrane that made it stable enough to handle CO2 capture. The membrane is impregnated with Rempe’s enzyme and has proven to be highly effective – at least on a laboratory scale.
“The special thing here is we have both high flux,” or flow rate through the membrane, Rempe said, “and high selectivity,” meaning it isolates only CO2. “That’s why we’re orders of magnitude better” than any current CO2 removal technologies.
The membrane is called the CO2 Memzyme – “mem” for membrane and “zyme” for the enzyme.
The CO2 Memzyme produces CO2 that is 99 percent pure, which makes it ideal for industrial uses ranging from enhanced oil recovery and beverage carbonation to biofuel production.
The membrane can be adapted to remove other flue gases, such as methane, by changing its enzyme, Rempe said.
The next step toward commercializing the technology is to secure partners and funding to build a larger model of the CO2 Memzyme and related infrastructure to test the system.
“We already understand the membrane and how it functions, so now we need to fabricate it at large scale and make sure its (laboratory scale) properties stay in place,” she said.
The researchers received a patent for the CVO2 Memzyme innovation earlier this year.