Potential impact of CO2 emissions on the seafloor

Giorgio Caramanna, Sebastian John Hennige

Research output: Chapter in Book/Report/Conference proceedingChapter

Abstract

Carbon Capture and Storage (CCS) aims to capture CO2 from fossil-fuel sources, transport and store it in suitable geological formations where it will be confined for extremely prolonged times. This is considered a feasible way of mitigating global warming. The seafloor is one of the target areas to safely store large volumes of anthropogenic CO2 through the development of sub-seabed CO2 geological storage. For the UK and large parts of Europe, the North Sea is potentially the most suitable location for CCS projects required to achieve planned targets in the reduction of CO2 emission. Other sub-seabed areas are studied for their storage potential in America and Asia. Even if the technology is considered proven, following the experience gained from the oil industry in using CO2 for enhanced oil recovery (EOR), and a few CO2 storage pilot projects, the risk of CO2 seepage must be addressed considering potential consequences on the marine environment. CO2 emissions may affect the seafloor with physical (e.g. sediments displacement), chemical (e.g. acidification) and biological (e.g. toxicity) effects. Laboratory experiments and the study of natural submarine CO2 vents are contributing to the development of a solid body of knowledge on these effects. The research is largely multidisciplinary, requiring expertise in natural sciences, engineering, chemistry and physics. The main observed consequences of CO2 emissions are a quick and strong acidification of the environment which may lead to the mobilization of pollutants, such as heavy metals, within the sedimentary cover of the seafloor diffusing within the overlying water column. Increased weathering of calcareous substrata is also likely following exposure to CO2- enriched fluids. Potential impacts upon local biodiversity would include displaced dissolved oxygen leading to anoxic regions, and localised ocean acidification. Consequences of increased CO2 would be a reduction in local seawater pH, and in the availability of carbonate ions required by calcifying organisms to grow. Predicted CO2 levels from potential seeps would lead to dissolution of exposed calcium carbonate shells and skeletons of local organisms. While some species would be able to tolerate and survive in such situations, others would die or suffer reduced growth rates. This is particularly pertinent for sessile benthic organisms which could not migrate following the onset of seepage. Naturally occurring submarine CO2 vents located along active tectonic and volcanic areas provide a good example of how organism communities change depending on their proximity to released CO2. For example, coral survival and growth decreases the closer they are to the CO2 vents, with macroalgae dominating the habitat instead. The timing and duration of potential industrial CO2 seeps would preclude the possibility of organism genetic adaptation over successive generations, and as such, possible impacts would depend upon organism acclimation potential and resilience. This chapter reviews the physical, chemical and biological implications of subseabed storage of CO2, and the consequences of potential seep events.

Original languageEnglish
Title of host publicationAdvances in Environmental Research
EditorsJustin A. Daniels
PublisherNova Science Publishers
Pages41-54
Number of pages14
Volume33
ISBN (Print)9781631178139
Publication statusPublished - 2014

ASJC Scopus subject areas

  • Environmental Science(all)

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  • Cite this

    Caramanna, G., & Hennige, S. J. (2014). Potential impact of CO2 emissions on the seafloor. In J. A. Daniels (Ed.), Advances in Environmental Research (Vol. 33, pp. 41-54). Nova Science Publishers.