Offshore Carbon Capture and Storage: Environmental Impact Assessment, Monitoring and Research Synergies with OA

Chair: Zoë Hilton

Jerry Blackford(1), Gennadi Lessin(1), Jonathon M. Bull(2), Henrik Stahl(3)

1 Plymouth Marine Laboratory, Prospect Place, Plymouth, UK
2 University of Southampton, NOC, Southampton, UK
3 Zayed University, Dubai, UAE.

Background
Carbon Capture and Storage (CCS) is a key climate and OA mitigation option when coupled with fossil or biomass fuels and some industrial processes. Globally, considerable storage capacity lies offshore in geological formations below societally important coastal seas. CCS regulations require environmental impact assessments for CO2 leakage and effective monitoring for detection or assurance. Thus impact assessment is a high CO2 problem, but in contrast to OA, perturbations are spatially and temporally limited, primarily driven by organism stress responses and resilience rather than adaption and migration. Monitoring requires a detailed understanding of near bed carbonate chemistry dynamics and instrumentation capable of surveying large areas efficiently.

Methods
This talk will detail the linkages between OA research and R&D for CCS, in particular based on a sub-seafloor CO2 controlled release experiment coupled with local and regional modelling of carbonate chemistry, biological response and leakage dispersal.

Findings
For a moderate leak, impact is minimal, spatially restricted and recovery rapid, however carbonate dissolution in the sediments coupled with complex physical flow patterns result in significant patchiness. Modelling of a range of leak scenarios show a log-linear relation between leak rate and impacted area with ~two orders of magnitude variability, depending on hydrodynamic conditions and leak morphology. Impact models illustrate the relationship between pH, exposure time and impact, driven by physiological and ecological processes. In the absence of comprehensive near bed carbonate observations, regional climate models have enabled the development of site specific strategies for monitoring based on AUVs and benthic landers.

Conclusions
For most envisioned leak scenarios, however unlikely, impacts will be restricted and not sufficient to merit concern, especially when compared to climate change and OA. We propose that regulatory driven CCS monitoring, including baseline characterisation and instrumentation development has much synergy with global initiatives to monitor OA.