Micromotors could remove carbon dioxide from the ocean

EvanEnvironment, Good News0 Comments

Image courtesy of Brian Skerry, National Geographic


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TLDR Still in development, newly engineered "micrometers" could one day autonomously swim the oceans to make the waters less acidic and save marine life

Engineers at the University of California, San Diego have developed and tested a new “micromotor” that can theoretically remove carbon dioxide (an acidic pollutant) from the Earth’s oceans. These micromotors would use enzymes to propel through the water, converting carbon dioxide (CO2) into calcium carbonate (CaCO3) as they swim by utilizing the flow of water with carbonic anhydrase. In experiments, the micromotors removed 88% of the carbon dioxide from the seawater.

“In the future, we could potentially use these micromotors as part of a water treatment system, like a water decarbonation plant,” said Kevin Kaufmann, co-author of the study. “If the micromotors can use the environment as fuel, they will be more scalable, environmentally friendly and less expensive.”

Micromotor designs

A drawing of the chemical process involved in the propulsion of the micromotor (University of California, San Diego)

What to do with the CO2 turned CaCO3, now in solid form? It could be stored or removed via a treatment plant such as the kind that Kaufmann describes. But what about letting micromotors loose in the oceans? It could prove difficult for such a tiny motor to store, let alone remove the CaCO3 it creates. Interestingly enough, though, calcium carbonate is a compound naturally found in marine organisms and fossils, such as coral and shells, respectively. So leaving behind CaCO3 may not be so bad…

The real drawback with the current micromotor designs, however, is that the seawater solution used in the experiments required a hydrogen peroxide additive, and the micromotors required a platinum casing. The platinum reacts with the hydrogen peroxide to propel through the water. Platinum happens to be expensive, and adding vast amounts of hydrogen peroxide to the oceans may not be sustainable, let alone feasible.

The upside is that the solution requires only a small percentage of hydrogen peroxide — as little as 2 – 4%. At this concentration, the micromotors were able to propel 100 micrometers per second. In the next stage of development, the nanoengineers will attempt to find a platinum alternative that happens to be in greater abundance (and consequently, less expensive).

Why bother with these micromotors in the first place? Earth’s oceans act as carbon “sinks” in that they naturally draw CO2 out of the atmosphere. While helpful in slowing climate change, mankind’s production of carbon dioxide has pushed the oceans to their limits. Absorbing that atmospheric CO2 comes at a cost of making seawater more acidic, and acidic seawater is proven to be lethal to marine life. We are already seeing coral reefs (home to much of the ocean’s fish species) around the world die in incredible quantities as a result of the ocean’s recent acidification. More historically, an article from this Spring tied acidic oceans to the greatest extinction event ever 252 million years ago.