New Carbon Capture Research Emphasizes Recycling, Not Sequestration

January 21st, 2019 by Tina Casey

Fans of carbon sequestration swallowed a bitter pill back in 2015, when the US Department of Energy pulled the plug on the billion-dollar FutureGen showcase project. However, that doesn’t necessarily mean an end to “clean” coal. The related field of carbon capture is still humming along, bringing with it the prospect of gathering up carbon emissions and recycling them into fuels, plastics, and whatever else. So, is this a good thing?

The Bottom Line For Carbon Capture

To be clear, the less fossil fuel burning the better. Last fall, CleanTechnica noted that carbon capture is a poor cousin to simply not burning fossil fuels any more. That’s true enough, but carbon capture will still be relevant for many years to come.

The world will still be converting fossils into energy to some degree indefinitely, and then there’s the whole industrial sector to consider.

The real sticky wicket is the bottom line. Carbon capture and sequestration is prohibitively expensive. One potentially economical solution is offsetting emissions through biomass. However, that approach — planting new forests, for example — most likely can’t scale up enough to be effective, even in a low carbon economy.

What’s missing from the capture-and-sequester picture is added value, and that’s where the latest developments come in.

One good example came up last month, when a team of researchers at South Korea’s Ulsan National Institute of Science and Technology announced a new carbon recycling system that produces electricity and hydrogen from water.

The UNIST team (which includes a researcher at the Georgia Institute of Technology) was inspired by the connection between ocean acidity and ocean carbon sequestration. Here’s the short version:

If acidity increases, the number of protons increases, which in turn increases the power to attract electrons. If a battery system is created based on this phenomenon, electricity can be produced by removing CO2.

Does this sound like a method for reducing ocean acidity? Maybe! We’re guessing that the concentration of CO2 needs to be relatively high in order to achieve the desired result, but that’s just a guess. If you have some ideas about that, drop a note in the comment thread.

In any case, the new research is not based on ambient carbon dioxide in seawater. The team set up a fuel cell consisting of a sodium metal cathode, an NaSICON separator (that’s short for Sodium Super Ionic Conductor, typically used in sodium batteries), and a catalyst. Here’s the not-so-short version:

Unlike other batteries, catalysts are contained in water and are connected by a lead wire to a cathode. When CO2 is injected into the water, the entire reaction gets started, eliminating CO2 and creating electricity and H2. At this time, the conversion efficiency of CO2 is high at 50%.

For the long version, check out the team’s paper in the open access journal iScience under the title, “Efficient CO2 Utilization via a Hybrid Na-CO2 System Based on CO2 Dissolution.“

The research team is confident that the results of the new system justify further work. In addition to the conversion efficiency of 50%, the cell operated reliably for more than 1,000 hours.

The system also eliminated carbon emissions, which is a bug in certain non-aqueous (aka aprotic) cells. Aprotic cells also tend to lose performance as solids accumulate on the surface of the electrode.

What About Hydrogen?

It’s worth noting here that sustainable hydrogen is not necessarily the same as renewable hydrogen, but it is a step up on the sparkling green future scale.

Regardless of whether or not fuel cell electric vehicles crack the mainstream market for passenger cars, hydrogen demand is anticipated to skyrocket in the future partly due to rising demand for maritime uses and long-haul trucking.

In that regard, the UNIST team may have some catching up to do. The US company Fuel Cell Energy has already commercialized a carbon capture and recycling system that generates electricity and produces hydrogen.

Fuel Cell Energy crossed the CleanTechnica radar in 2016 for a carbon capture project at a power plant in South Carolina, supported by the Department of Energy and — for reasons — ExxonMobil. Earlier this month it embarked on a carbon capture project in California that deploys landfill gas to generate electricity and hydrogen. Fuel Cell Energy also has a similar biogas-enabled hydrogen project with Toyota under its belt in California.

For an entirely different take on carbon capture and waste gas recycling, check out another US company, LanzaTech.

No Future For Carbon Sequestration, For Now

Meanwhile, the FutureGen project appears to be all but dead. It already suffered one near-death experience when former President Bush nixed funding in 2008. Former President Obama revived it in 2009 as part efforts to kickstart the US economy after the global financial crisis, but by 2015 it became clear that more sustainable alternatives to “clean” coal were on the horizon.

Resuscitating the experiment under the Trump* administration appears nearly impossible, so that could be the end of large-scale sequestration.

The US Department of Energy is still actively pursuing research aimed at bringing down the cost of carbon capture, but now the focus appears to be on reclaiming CO2 for other uses rather than dumping it somewhere for the next generation to deal with.

CleanTechnica is reaching out to Fuel Cell Energy to see what’s in store for the future, so stay tuned for more on that.

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*Developing story.

Image: carbon recycling system via UNIST.









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