Is there a way to curb the rise in carbon dioxide (CO2) in the atmosphere and the acidification of oceans at the same time? The project DESARC-MARESANUS – a collaboration between Politecnico di Milano and the Foundation Euro-Mediterranean Center on Climate Change – attempts to answer this question. The researchers explore the process of ocean alkalinisation, relying on already existing maritime traffic to spread Ca(OH)2.
It’s now widely accepted that it’s impossible to reach the targets set by Paris Agreement simply by cutting carbon emissions. To keep the rise in global temperatures below 2°C, we need to develop and implement more active strategies to remove CO2 from the seas.
One method that has received much attention recently to counteract acidification is the artificial alkalinisation of water, achieved via dissolution of lime (Ca(OH)2). This is known as ocean liming, and it actually addresses two problems at the same time: global warming caused by increased levels of atmospheric CO2 and ocean acidification.
In the first paper published in Frontiers in Climate (1), researchers used a set of computer simulations to explore how alkalinisation could be achieved in the Mediterranean Sea. In contrast to previous studies, the team determined that this approach would significantly mitigate climate change, and doubling the amount of CO2 uptake in the Mediterranean Sea would only take 30 years of alkalinisation.
“The idea of ocean alkalinisation as a mitigation strategy for climate change is for the first time assessed on the basis of a technically feasible pathway of implementation providing a first step towards a real-world application”, states Momme Butenschön, a scientist at the CMCC Foundation Euro-Mediterranean Center on Climate Change (CMCC). “In addition, a solution is indicated that may stabilise the acidity of the seawater counteracting acidification without risking dramatic alterations of the seawater chemistry, which would have largely unknown consequences.”
Continuing this work, a second study also published in Frontiers in Climate (2), defended how maritime transport already in operation can be “highjacked” to perform ocean liming and spread enough lime to get a significant result. In fact, the team calculated that, for closed basins like the Mediterranean Sea, where traffic is high, the potential for ocean alkalinisation surpasses what is actually needed to counteract ocean acidification.
Although more research is needed to understand in detail all technical issues, these results clearly show the potential of implementing ocean liming to the Mediterranean Sea, relying on the existing network of cargo ships and tankers.
“These two publications provide a key contribution to the international and national scientific communities working to find solutions to these two issues – atmospheric CO2 removal and counteracting ocean acidification – which we will have to tackle in the future”, concluded Stefano Caserini, Project leader of the project Desarc-Maresanus. “Even if further investigations are needed, these results are encouraging”.
(1) Butenschön M., Lovato T., Masina S., Caserini S., Grosso M. (2021), Alkalinization Scenarios in the Mediterranean Sea for Efficient Removal of Atmospheric CO2 and the Mitigation of Ocean Acidification. Frontiers in Climate – Negative Emission Technologies, volume 3, 11 pages, DOI: 3389/fclim.2021.614537
(2) Caserini S., Pagano D., Campo F., Abbá A., De Marco S., Righi D., Renforth P., Grosso M. (2021) Potential of maritime transport for ocean liming and atmospheric CO2 removal. Frontiers in Climate – Negative Emission Technologies. 3:575900. https://doi.org/10.3389/fclim.2021.575900