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The Dark Oxygen Hypothesis

A scientific paper published in Nature magazine earlier this week hypothesized that a phenomenon termed “dark oxygen” production may be occurring on the seafloor in the Clarion-Clipperton Zone (CCZ) of the Pacific Ocean whereby a slight voltage differential between different metals contained in the polymetallic nodules found in the area may drive an electrochemical dissolution of water (H20) into oxygen (O2) and hydrogen (H2), although no increase in hydrogen presence has been noted by the researchers. Latching onto a headline. The timing of the publication of the study to coincide with the ISA meetings currently underway in Jamaica and the speed and breadth with which media outlets, such as CNN and CNBC, among many others, picked up the story, suggest a last ditch effort by anti-mining NGOs to influence the ISA decision-making process, renewing the calls for a deep-sea mining moratorium. However, as we discussed previously, there is no provision for such a moratorium in the ISA charter and the authority reiterated its goal of completing and issuing the final mining code by the end of 2025, which would coincide with TMC’s goal of obtaining the exploitation license at that time. Questionable scientific rigor. TMC issued a statement addressing the research paper findings, in which the company questioned the study’s methodology, pointed out that the paper was submitted to and rejected by several peer-reviewed scientific journals before being accepted by another, and its conclusions are contradicted by previous studies, such as Khripounoff et al (2006) and Vonnahme et al (2020), while An et al (2024) failed to replicate the results and, in fact, observed a directly opposite phenomenon of oxygen consumption. It is expected that other scientists investigating the matter may publish their research in the weeks and months ahead, further calling into question Sweetman’s hypothesis. Yes, but what if…? Even taking Sweetman’s hypothesis at face value, in other words, accepting the premise that polymetallic nodules provide a mechanism for splitting water into oxygen and hydrogen, deep-sea mining stakeholders should keep in mind the following, so as to consider the possibility in a proper context: (1) minuscule amounts of O2 thus produced pales in comparison to the oxygen-producing capabilities of ocean organisms carrying out photosynthesis reactions, rain forests, and other terrestrial “carbon sinks”; (2) the ISA designating 43% of the CCZ as conservation areas that will never be mined thus preserving the local environment; (3) the exploitation (mining/collecting) of polymetallic nodules in the CCZ will be carried out over decades, mitigating whatever environmental disruptions that may occur; (4) the NORI-D license area represents just 0.007% of the ocean floor; and (5) TMC’s environmental study of the area where large-scale collection has been carried out shows recovery in biodiversity and bioactivity a year after the collection of nodules disrupted the local ecosystem. Science over politics. The NGOs’ latest attempt to muddy the waters (pun intended) on the environmental impact of DSM aside, we continue to expect TMC to submit its application by the end of 2024 and for the ISA to approve the project by the end of 2025, as scientific data replaces politically motivated speculations.