Capturing carbon dioxide, a potent greenhouse gas, has long been a focus for researchers trying to slow down climate change. A chance discovery inspired by sea urchins could pave the way to clean, cheap, effective capture CO2 at coal-fired power plants and other "dirty-burn" industrial facilities.
Scientists at Newcastle University were researching carbonic acid chemical reactions; what happens when CO2 reacts with water. They needed a catalyst to speed up such reactions. Dr. Lidija Šiller, a physicist and Reader in Nanoscale Technology at Newcastle University, also happened to be studying how organisms like sea urchins absorb CO2 into their bodies.
Sea urchins’ prickly exoskeletons are made from calcium carbonate, also known as chalk. But sea urchins are not born this way. They have to build their spiny shell as they grow and they do this by absorbing CO2 dissolved in the oceans.
"When we analyzed the surface of the urchin larvae we found a high concentration of Nickel on their exoskeleton," Dr. Šiller said. Her team added nickel nanoparticles to their carbonic acid reaction, which removed all of the CO2, converting it into chalk.
Converting CO2 into calcium carbonate isn’t a completely new idea.
"One way to do this is to use an enzyme called carbonic anhydrase," explains Gaurav Bhaduri, lead author on the paper and a PhD student in the University’s School of Chemical Engineering and Advanced Materials.
However, in addition to creating chalk when reacting with CO2, carbonic anhydrase also creates carbonic acid. This is a big problem because the enzyme does not work in acidic conditions, limiting the time the process can be work. But the sea urchin-inspired nickel nano-particles don’t slow down in more acidic conditions.
They’re also magnetic, which means they can be recaptured and used repeatedly, and many times cheaper than carbonic anhydrase.
Human beings were responsible for emitting nearly 40 billion tons (36 billion metric tons) of CO2 into Earth’s environment in 2013, according to the Earth System Science Data Discussions, a peer-reviewed journal. China contributed the greatest fraction of that total, followed by the United States. The principal source of the emissions were coal-burning power generation utilities.
Most plans for preventing CO2 from escaping such plants revolve around driving captured carbon deep underground. But such Carbon Capture and Storage (CCS) or Carbon Sequestration systems are extremely costly. They also run the risk of carbon migrating through gaps in bedrock and emerging great distances from the storage site.
The Newcastle University researchers suggest placing a column of water and Nickel nano-particles on the chimney of a power plant or factory to capture CO2 directly from the waste gas. The safely inert calcium carbonate produced by the reaction could then be recovered and used to make cement, plaster medical casts, or a variety of other practical products.
"Our process would not work in every situation – it couldn’t be fitted to the back of a car, for example – but it is an effective, cheap solution that could be available world-wide to some of our most polluting industries and have a significant impact on the reduction of atmospheric CO2," Dr. Šiller said.