Description: This is the stylized description of our ocean liming case study, which we are using the introduce our life-cycle assessment to stakeholders in our consultation process

Description: Realistic alkalinization scenarios, under the global context, are proposed and examined, which can be extent to include spatial considerations and specific technical and regulatory constraints. Results provide a set of stylistic projections of total mineral (carbonate and silicate) addition, with its temporal timeframe spanning from as early as 2025 up to 2100). Among others, these estimates can be used to constrain model simulations that will be carried out in Work Package 4.

Description: A common challenge in many ocean-based negative emissions technologies (NETs) is the difficulty of developing new global industries and supply chains, which could be necessary for their much needed rapid and large-scale deployment. Therefore, to facilitate roll-out, existing industries and infrastructure should preferably be utilised. For ocean alkalinity enhancement (OAE) by CaO, i.e., ocean liming (OL), the lime can be produced by calcination of limestone using the spare capacity in the cement industry. For OAE by NaOH, i.e., electrochemical brine splitting (EBS), the NaOH can be produced by electrolysis of waste brines from the desalination sector. In this case study, we investigate the realistic OAE potential of Spain, because of its large availability of limestone, its increasing spare cement kiln capacity, and its large and growing desalination industry. This case study shows Spain has a high potential for alkalinity addition to the oceans. Specifically, the total CDR capacity of Spain via OAE is 24.4 Mt yr.-1 with contributions of 22.6 Mt of CO2 removed by OL and 1.8 Mt of CO2 removed by EBS, assuming these processes are driven solely by renewable energy. Further, this case study provides a realistic estimate of the CO2 removal potential and life cycle emissions for alkalinity enhancement for a given region, in contrast to more general global or continental studies before it. By doing so, Spain’s annual carbon dioxide removal (CDR) capacity by OAE is also identified. Future work will look to include coastal enhanced weathering of olivine to the portfolio of Spain’s OAE approaches.

Description: Ocean alkalinity enhancement (OAE) is an emerging strategy that aims to mitigate climate change by increasing the alkalinity of seawater. This approach involves increasing the alkalinity of the ocean to enhance its capacity to absorb and store carbon dioxide (CO2) from the atmosphere. This chapter presents an overview of the technical aspects associated with the full range of OAE methods being pursued and discusses implications for undertaking research on these approaches. Various methods have been developed to implement OAE, including the direct injection of alkaline liquid into the surface ocean; dispersal of alkaline particles from ships, platforms, or pipes; the addition of minerals to coastal environments; and the electrochemical removal of acid from seawater. Each method has its advantages and challenges, such as scalability, cost effectiveness, and potential environmental impacts. The choice of technique may depend on factors such as regional oceanographic conditions, alkalinity source availability, and engineering feasibility. This chapter considers electrochemical methods, the accelerated weathering of limestone, ocean liming, the creation of hydrated carbonates, and the addition of minerals to coastal environments. In each case, the technical aspects of the technologies are considered, and implications for best-practice research are drawn. The environmental and social impacts of OAE will likely depend on the specific technology and the local context in which it is deployed. Therefore, it is essential that the technical feasibility of OAE is undertaken in parallel with, and informed by, wider impact assessments. While OAE shows promise as a potential climate change mitigation strategy, it is essential to acknowledge its limitations and uncertainties. Further research and development are needed to understand the long-term effects, optimize techniques, and address potential unintended consequences. OAE should be viewed as complementary to extensive emission reductions, and its feasibility may be improved if it is operated using energy and supply chains with minimal CO2 emissions.