The typical carbon capture approach happens in two steps. The first involves using high-pH liquids to separate the carbon dioxide from mixed-gas streams.
Electrochemical Processes for Advancing Carbon Capture Efficiency
Emily Newton | Revolutionized
People are continually interested in improving carbon capture outcomes. Ongoing research suggests abundant promise in electrochemical carbon capture processes. Although most remain in the research and development phase, teams have already gotten results that could justify scaling up their efforts to market them to the public.
Engineering Multiple Improvements Over Existing Carbon Capture Processes
One such system developed by a Rice University engineering team has significant advantages over current electrochemical carbon capture processes. The typical carbon capture approach happens in two steps. The first involves using high-pH liquids to separate the carbon dioxide from mixed-gas streams.
In the second step, people regenerate the carbon dioxide from the solution by heating it or using a low-pH liquid. However, conventional methods require temperatures as high as 1,652° Fahrenheit, making them extremely energy intensive.
However, Rice University engineers developed a device that can handle the carbon capture process without people needing to heat up or pressurize it first. The invention also does not produce or require chemicals, and it plugs into standard power outlets.
Another notable advantage of this option over current processes is it is independent of large-scale or centralized infrastructures. Instead, this modular, point-of-use device offers flexibility for industrial use at power and chemical plants but also works in offices. Haotian Wang — who developed the device in his lab — even envisioned using it to take CO2 from the atmosphere and sending the concentrated gas into a greenhouse to promote plant growth.
The device has a cathode with an oxygen evolution reaction-performing anode and a solid-electrolyte layer. The resulting reactor showed carbon capture efficiency greater than 98%. Lab experiments also showed the electricity associated with using a 50-watt light bulb for an hour could generate 10 to 25 liters of high-purity CO2.
Wang confirmed the most eco-friendly way to do this carbon capture process is to power it with renewable electricity. Then, the approach has a minimal — or no — carbon footprint.
Addressing the Carbon Emissions Issue
University of Toronto researchers have achieved similar progress with electrochemical carbon capture by developing a device that functions as an electrolyzer and fuel cell. The people involved in this invention recognized carbon capture is not new, but the existing options have several shortcomings. For example, the processes often emit carbon, reducing the overall positive effects. This group hoped to find a more efficient alternative to maximize the climate-related benefits.
They turned their attention to a technique called the pH swing cycle to do this. It involves pumping air through a high-pH liquid. Carbon dioxide in the atmosphere gets captured as carbonates when it reacts with the liquid.
Then, regeneration occurs by adding chemicals to cause the carbonates to deposit as solid salt. This differs from the conventional process, which involves burning natural gas to heat the salt and turn the carbonates back into CO2. That gas then gets injected underground or used in other carbon-based processes.
The team took issue with the traditional process for the pH swing cycle due to the produced carbon. They clarified that 300 to 500 kilograms of CO2 generate for every ton of carbon dioxide captured.
However, building one device to function as a fuel cell and an electrolyzer allowed them to overcome that emissions problem. Researchers could switch the operation mode each second to cause two reactions on the surface of one electrode. Tests with this innovation showed it is about 40 times less carbon-intensive than current thermal-based carbon capture processes.
MIT Researchers Prioritizing Both Electrochemical Carbon Capture and Removal
Electrochemical carbon capture is only one of the many ways people are working to create a more sustainable future. For example, one company makes batteries with carbon footprints 80% lower than those produced with coal-based energy.
Individuals are also interested in creating more products that are easier to recycle at the end of their useful lives. Those things could all reduce the amount of CO2 in the atmosphere. But even after those efforts become mainstream, people will still need to deal with the carbon produced.
The people on MIT research teams are working on electrochemical-based processes for CO2 removal, as well as those that will capture the gas. The removal effort concerns a reversible process that uses membrane-free electrochemical cells to remove carbon directly from the ocean. It would cause major progress if successful.
That’s because the ocean contains 30 to 40% of the CO2 human activities generate. Although those who worked on this effort say it won’t tackle the whole planet’s emissions, they believe it could reduce ocean acidification caused by CO2 buildup.
Another MIT project centers on improving the efficiency of systems that rely on catalytic surfaces to enhance carbon-sequestering electrochemical reactions. The team says their approach could speed up and optimize them.
The systems that use catalytic surfaces usually have a CO2-containing gas stream that passes through water, bringing the carbon dioxide necessary for an electrochemical reaction. However, the gas stream moves through the liquid slowly, reducing the CO2 conversion rate.
The team engineered a new design that keeps the CO2 stream concentrated and close to the catalyst’s surface. Lab tests indicated the concentration could almost double the system’s performance. The reaction was also sustained, contrasting with previous attempts where it quickly faded.
A Bright Future for Carbon Capture Technologies Using Electrochemical Processes
These and further attempts will help the world approach a future where carbon capture technologies are widespread and affordable. Some of these innovations may not reach commercial scale or researchers may realize obstacles they’ve yet to encounter make their processes less feasible than they’d hoped. Even so, the people involved with or interested in these attempts can learn from these lab trials, using their new knowledge to improve the success of future work.
It will be a while before researchers determine which carbon capture technologies are the easiest to scale and have the highest potential for use. The most likely scenario is people will use various approaches. Fortunately, the research covered here and elsewhere helps create a foundation that will get the public interested in and confident about carbon capture options.
The content & opinions in this article are the author’s and do not necessarily represent the views of AltEnergyMag
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