Flexens, Lhyfe, and Stockholm University Share Findings on Ocean Reoxygenation Effort

Flexens, Lhyfe and Stockholm University published the full report on the ‘BOxHy’ project launched in October 2023. Its conclusions outline the ‘BOxIn’ offshore oxygen injection pilot project, which will be announced in a few months’ time and is expected to last around 6 years. The partners also welcome the growing interest among scientists, industry and institutions in the major issue of ocean “asphyxiation” (deoxygenation) and the option of reoxygenation, with the prominent example of the United Nations, which endorsed this project as part of the UN Decade of Ocean Science for Sustainable Development 2021-2030 until October 2024.

The ‘deoxygenation’ of the oceans is a growing global phenomenon that is impacting humankind

All around the world, the oceans have been reportedly losing oxygen since the 1950s, caused by global warming and water pollution. On one hand, global warming is increasing the surface temperature of the water, thereby altering the concentration of oxygen in the water, altering the stratification and marine currents (their routes and properties). On the other hand, the nutrients discharged into the coastal environment through run-off from land (coming notably through fertilisers or wastewater) generate excessive algal blooms.

As bacteria break down algae and consume oxygen, an increase in algae leads to more oxygen being used by the bacteria—this process is called eutrophication. When there is no longer enough oxygen, the bacteria start to mobilize substances, such as phosphorus, formerly stored in the sediment, which helps to feed new algae. This vicious circle depletes the oxygen content, which at a certain point is no longer sufficient to sustain underwater life.

Oxygen is necessary for underwater life, and in particular, for the fish that feed us. As well as underlining the urgent need to drastically limit CO2 emissions and nutrient pollution in order to counteract deoxygenation, Lhyfe, Flexens and the University of Stockholm stress the importance of exploring, in parallel, the possibility of restoring it. Among the possible solutions, the reinjection of oxygen into these deoxygenated dead sea regions is now being studied.

This project, aiming to reoxygenate the oceans by producing hydrogen at sea, is ambitious. It aims to take advantage of the future offshore hydrogen production sites built by Lhyfe in conjunction with offshore wind farms to provide a service to the environment. Lhyfe is building sites both on land and at sea, such as the HOPE project scheduled for 2026. When hydrogen is produced by electrolysis of water, the water molecule is split in to hydrogen and oxygen. The manufacturer proposes to make this oxygen available to the ocean.

Work on reoxygenation must be carried out using a scrupulously strategic and scientific methodology, and over a long period of time, at the risk of further destabilising ecosystems, which is why the BOxHy project has been carried out by a consortium originating from industry and science in a collaborative manner.

A methodology to define the contours of an oxygen injection pilot project

The report published by Flexens, Lhyfe and Stockholm University details the results of the BOxHy project, which involved assessing the feasibility of injecting oxygen to combat hypoxia and anoxia in the Baltic Sea, evaluating suitable coastal locations for setting up the small scale pilot project, and defining in what quantities, at which depth, how to proceed, and so on.

Thanks to a detailed survey, 19 coastal sites in the Baltic Sea were studied and 3 were identified as potentially suitable for a pure oxygen injection pilot project. Around ten criteria were taken into account in selecting these sites: the presence of anoxia, a pre-existing observation programme, the possibility of installing the pilot infrastructure, an existing high-resolution bathymetry (measurement of marine depths), the assessment of the local socio-economic situation, applicable regulations, human presence, the accessibility of the site, etc.

This pilot project is expected to last around 6 years, so that baseline measurements can be taken beforehand, oxygen can be injected for at least 3 years, and the area can then be observed for another year after the experiment is completed. The project is expected to cost between 5 and 6 million euros.

In a few months’ time, Lhyfe will be releasing details of the next phase, the pure oxygen injection pilot, known as BOxIn (Baltic Sea Pilot for Pure Oxygen Injection). The final location, size and duration of the project will depend in part on the funding obtained.

This project has also made it possible to explore the industrial phase of reoxygenation. With the emerging production of offshore wind energy and the growing demand for renewable hydrogen, the development of offshore production sites for the co-production of hydrogen and oxygen was deemed feasible.

Growing recognition of the problem and the rise of reoxygenation

In 2023 and 2024, the partners saw a growing recognition of artificial reoxygenation as one of the additional potential ways to mediate ocean deoxygenation after measures to limit CO2 emissions and the run off of nutrients have been installed.

In March 2024, the BOxHy project was endorsed until October 2024 by the United Nations as part of the Decade of the Ocean, validating its importance and alignment with the UN’s goals for sustainable ocean management. As part of this, Lhyfe’s reoxygenation expert was invited to the UNESCO in September 2024 to take part in a workshop led by the co-chairs of the Global Ocean Oxygen Network (GO2NE). Participants discussed the theoretical feasibility and possible environmental impacts of artificial ocean reoxygenation in order to prevent or reverse their deoxygenation. Participants will develop draft recommendations to guide the planning and regulation of sustainable reoxygenation research and deployment, including pilot studies.

In addition, as part of its ongoing work on reoxygenation, Lhyfe is now in contact with several industrial and scientific project leaders working on the same subject around the world, in order to compare the results of their R&D work, with the aim of improving knowledge on the subject and further connecting industry and research.

Finally, in 2023 and 2024, at least 3 other reoxygenation projects in the marine environment have been announced in Europe, demonstrating the convergence towards a response that is increasingly explored and perceived as relevant, and enabling to exchange with complementary project leaders featuring industrial, scientific and policy backgrounds.

This project is a groundbreaking tripartite collaboration:

• Flexens, a leader in the development of hydrogen projects with a strong regional focus;
• Lhyfe, a global front-runner in the onshore and offshore production of green and renewable hydrogen for mobility and industry, whose founding ambition is to reoxygenate the oceans through its offshore activities;
• The Department of Ecology, Environment, and Plant Sciences (DEEP) at Stockholm University, with expertise in marine ecology monitoring and a focus on both fundamental and applied Baltic Sea research.

Szilvia Haide, coordinator of the BOxHy consortium from Flexens said,  “We are proud to have coordinated this project and delighted by the interest shown in it by the scientific, industrial and institutional communities. This BOxHy project has two major advantages: it advances research on the subject of reoxygenation, and it enables the next steps towards Baltic-sea wide implementation. We’ll all be keeping a close eye on its progress as Lhyfe leads the piloting phase.”

Matthieu Guesné, member of the BOxHy consortium and founder and CEO of Lhyfe said,“Reoxygenation is at the heart of our project. Back in 2017, we imagined a way of massively decarbonising transport and industry by producing and supplying renewable hydrogen and, at the same time, contributing to the reoxygenation of the oceans as part of our offshore projects. We are now embarking on the second phase, which we will be able to present in detail as soon as we have more visibility of the funding for the BOxIn pilot project.”