Rare mineral project offers means to tackle acid effect on ocean life
29 Jan 2023
Scientists at Heriot-Watt and Hamburg universities say they have developed a process to boost oceans’ ability to cope with increases in carbon dioxide.
Up to a quarter of all CO2 released into the air is absorbed in the sea, leading to increased acidification that harms marine life, particularly shell-bearing crustaceans and molluscs.
But research from academics in Heriot-Watt, Edinburgh and the University of Hamburg, Germany, published in the journal Joule outlines the means to increase marine-stored CO2 without a rise in acidification.
Dr Phil Renforth, from Heriot-Watt’s Research Centre for Carbon Solutions (RCCS) proposed using the mineral ikaite, which dissolves CO2 and converts it into bicarbonate (HCO3) ions.
Ikaite, however is rare in its natural form, necessitating development of an engineering process in order to produce the hydrated carbonate mineral at scale. Also, depends on waters of 15 Celsius or lower in order to maintain its chemical stability.
Said Renforth: “The oceans are a huge carbon dioxide reservoir and we want to enhance that sink providing it does not harm marine eco-systems and that it can be done safely and responsibly. What we put forward in this paper is a new method that overcomes the limitations of some of the previous proposals while maintaining the overall benefit to the ocean.”
The combination of geochemists and engineers have proposed a production method that operates by adding limestone and water to a reactor alongside pressurised CO2. When the limestone dissolves, the ‘hard water’ produced is exposed to low pressures in a second reactor, to create crystals of ikaite which can be removed from the reactor. This is then added to sea water to increase alkalinity and remove carbon dioxide.
Explained Renforth: “This technology could be scaled up to have a meaningful impact on climate change, and the costs could be comparable to other CO2 removal approaches. That is possible within the next 20 to 30 years, particularly as the raw materials are abundant.
He added that further research was required to test the limitations of the process as well as the benefits and problems of the social and environmental impact.
“There is further work to be done also around the potential social and environmental impact, both positive and negative, on how such proposals might be monitored and verified in the real world, and the most suitable national and international regulation for operating this technology at scale.”
“We are at a very exciting stage but it’s about how we access this potential in a safe and responsible way.”
Academic lead Professor Jens Hartmann from the Centre for Earth System Research and Sustainability at the University of Hamburg agreed that increasing oceanic alkalinity had “massive potential” but more information was necessary about the geochemical and ecosystem effects.
Project funding for the work research titled 'Using ikaite and other hydrated carbonate minerals to increase ocean alkalinity for 2 carbon dioxide removal and environmental remediation' came from the Climate Pathfinders Foundation and ClimateWorks Foundation. It will be followed by further pan-European work, as part of the EU funded OceanNETs consortium.
Pic: Phil Renforth plus scanning electron microscopy image showing a precipitated hydrated calcium carbonate mineral (Ikaite) by Dr Laura Bastianini, Heriot-Watt University.
