Posted on Oct 15, 2023 at 09:10 PM
Approximately 75% of the planet's surface is water, primarily salty seas and oceans, which absorb one-third of all carbon dioxide emissions, making them the most significant carbon sink globally.
Oceans naturally produce alkalinity, acting as the planet's thermostat, a slow process influenced by atmospheric CO2 levels, which can be improved by satisfying this process.
Rainfall dissolves atmospheric CO2, slightly acidifying rainwater. Rainwater reacts with antacid rocks, neutralising acidity and creating carbonate or bicarbonate, accumulating in the ocean.
Governments and organisations increasingly adopt carbon emission capture to solve global climate change, although the technology is not widely used in factories and power plants.
Researchers at the University of Pittsburgh are developing membrane-based methods for capturing carbon dioxide from the ocean, using computational analyses and experimental results to determine the cost of charging a million metric tonnes of carbon dioxide annually.
Katherine Hornbostel, professor of mechanical engineering and materials science at the University of Pittsburgh, pursued developing the technology five years ago when there was little research or funding for capturing carbon dioxide from the ocean, she stated. There are two approaches: one employs microencapsulated sodium carbonate solvents, and the other employs hole fibre membrane contactors containing sodium hydroxide. The geometry of the two models differs, but they operate similarly, according to Hornbostel.
Additionally, to achieve the most ambitious goal of the 2050 Paris Climate Agreement—keeping global temperatures from rising above 1.5 degrees Celsius—10 gigatons of carbon dioxide must be removed from the atmosphere annually by the year 2050.
The sodium capsules can be regenerated by steaming them to 100 to 120 degrees Celsius. This process would enable the captured carbon dioxide to be extracted and stored. The tablets can be recycled to absorb more carbon dioxide in subsequent cycles thanks to regeneration.
Scientists at the University of Pittsburgh have developed a game-changing technology for directly capturing carbon dioxide from the oceans, providing a novel approach to combating ocean acidification and global warming. The team's research shows promising results using clever microencapsulated solvents and hollow fibre membrane contactors.
The concentration of greenhouse gases in the ocean is 150 times higher than in the atmosphere, making ocean carbon dioxide removal more effective than air capture. Ocean capture can be combined with offshore wind and carbon dioxide storage, and Hornbostel claims it also requires less land area.
"Moreover, seawater has a density of one thousand times that of air, potentially leading to a reduced system size."
The PH of oceans is currently 8.1, down 0.1 since the Industrial Revolution, causing concern due to the acidity of calcium carbonate and bicarbonate used by corals and invertebrates.
The hollow fibre contactor, costing around $500/metric tonne, can compete with direct air capture technologies, while the bead-like material costs over $8,000 per metric tonne of carbon dioxide.
Reducing costs and scaling this technology up will require increasing the rate of carbon dioxide removal, according to Hornbostel.
Her current research focuses on developing unique chemical coatings for the membranes that will cause carbon dioxide to bubble out and simplify capture.
The crucial thing to remember is that "direct ocean capture is meant to complement direct air capture as another approach to reduce carbon dioxide levels and mitigate global warming, not to replace it," she continues.
The oceans are a massive carbon sponge, soaking up 25% of the world's CO2 emissions. More space for them to absorb is created when the gas is removed.