REMOVING CO2 AND CONTRASTING SEAWATER ACIDIFICATION: SCENARIOS OF OCEAN LIMING IN THE MEDITERRANEAN SEA

Stefano Caserini1, Francesco Campo2, Dario Pagano2, Beatriz Barreto2, Tomas Lovato3, Momme Butenchon3, Simona Masina4 and Mario Grosso2, (1)Politecnico di Milano, Milano, 20133, Italy, (2)Politecnico di Milano, Department of Civil and Environmental Engineering, Milano, Italy, (3)Euro-Mediterranean Centre on Climate Change Foundation, Bologna, Italy, (4)Euro-Mediterranean Center on Climate Change, Ocean Modelling and Data Assimilation, Bologna, Italy
Abstract:
Artificial ocean liming has the potential of mitigating both ocean acidification and the increase of atmospheric CO2. While chemical processes are theoretically known, there is the need to prove the technical and economic feasibility of the whole chain of ocean liming, from calcium hydroxide production to discharge by vessels, in different contexts and scales.

This work presents the results of two research lines addressing these aspects in the framework of the DESARC (DEcreasing Seawater Acidification Removing Carbon)-MARESANUS project.

The efficiency of different lime spreading strategies in counteracting the increase of atmospheric CO2 and the acidification of the sea is quantitatively evaluated through a coupled physical-biogeochemical climate model (NEMO-BFM) for the Mediterranean Sea at 1/16 degree horizontal resolution (~6 km) under the RCP4.5 IPCC emissions scenario over the next decades. In particular, the analysis assesses the required time-scale of action and compares the effectiveness of different alkalinisation strategies on both spatial and temporal scales, in order to estimate the otimal strategy both in terms of mitigation potential (carbon dioxide removal) and ocean acidification reduction.

The environmental impacts on 15 categories (e.g. climate change, land use, marine eutrophication, etc) due to the production and discharge of slaked lime are also evaluated through a life-cycle assessment (LCA), based on a “cradle-to-grave” approach, that considers different feedstocks (biomass or coal) used for limestone calcination, different CO2 storage options (geological or confined submarine storage in glass capsules), and different types of vessels.