Published the 20/07/2023

IRD Brest publishes a first article on its work in conjunction with Lhyfe in the scientific journal Environmental Research Letters


Right from 2017, when Lhyfe was still in early development, the founding team led by Matthieu Guesné had a clear ambition: to massively decarbonise transport and industry by producing and supplying renewable hydrogen, while at the same time helping to re-oxygenate the oceans. But how?


The team imagined a completely climate-friendly process with a double impact:

  • On the one hand, it would produce hydrogen at sea (using seawater and wind energy) to decarbonise uses that emit high levels of CO2, such as heavy vehicles (e.g. trucks, buses, waste collection vehicles, etc.) and industry (e.g. chemicals, metals, glass, steel, etc.).
  • On the other, it would re-inject the oxygen by-product from the electrolysis of water into aquatic environments – which due to global warming and polluting industrial activities are increasingly depleted of oxygen – in order to re-oxygenate them.


Lhyfe’s production of offshore hydrogen is progressing step by step. It launched the production of renewable green hydrogen with Sealhyfe (a pilot plant capable of producing up to 400 kilos of hydrogen a day off the Atlantic coast, installed at sea in the second half of 2022), and announced the HOPE project (HOPE stands for Hydrogen Offshore Production for Europe), which will produce up to four tonnes of offshore hydrogen a day, off Ostend in Belgium, by 2026. In parallel, the company is conducting research into ocean re-oxygenation and hopes to one day realise this project, in conjunction with the deployment of future offshore production platforms.

Lhyfe began working, back in June 2020, with a number of research organisations, such as the Institute of Research for Development (IRD) in Brest. Lhyfe financed all the work involved in this project, and commissioned some of its experts, including offshore project manager Stéphane Le Berre, to help move this research forward. The Physical Oceanographer Dr. Patricia Handmann has been in charge of this work since June 2022.


The published article – available here in full – discusses:

  • The role of oxygen in aquatic environments;
  • How the production of renewable green hydrogen produces oxygen as a by-product;
  • The contents of the research carried out by the physical and biogeochemical ocean modelling experts of IRD Brest;
  • The results of the research, which revealed highly contrasting regional oxygen inventory responses, highlighting the extent to which the large-scale industrial artificial re-oxygenation of oceans could have an impact on Oxygen Minimum Zones (OMZ) worldwide, and must be treated with extreme caution.


Based on these initial results, Lhyfe is initiating a series of next steps in order to take the necessary precautions when approaching this issue.


Patricia Handmann, Oxygenation Advisor at Lhyfe: “Ocean deoxygenation is a major issue for our planet, which deserves our full attention. To see a young company like Lhyfe dedicating resources to exploring the potential for providing ecosystem services is a profoundly inspiring example for our society. This first work is very encouraging, and with our partners, we will be pursuing it in the coming months, rigorously and responsibly. We now aim to build an adequate scientific, legal and technological basis, which will pave the way for the effective implementation of ocean re-oxygenation at our future offshore green hydrogen production sites.”


A summary and commentary by Patricia Handmann is included below: 


What could be the global potential of Artificial Ocean Reoxygenation linked to offshore hydrogen production ?

– a study with an ocean model –

The ocean represents an enormous capacity buffering global warming and the anthropogenic CO2 emissions, taking up about a quarter of the anthropogenic CO2. Due to the warming of not only the atmosphere but also the ocean, this capacity will be weakened. The ocean will warm, acidify and deoxygenate in the future, which will change its physics, chemistry and biology and will lead to less capacity to take up carbon and oxygen [1].

Roughly 50 % of the oxygen on earth originates in the ocean [2]. Oxygen, produced by marine cyanobacteria, started to accumulate in earth’s atmosphere and the shallow ocean 2.5 billion years ago [3]. It has a crucial role defining ocean nutrient cycles and marine habitat. Oxygen therefore has a substantial impact on fisheries and the coastal marine economy. Scientists observe declining dissolved oxygen levels in the global ocean since the 1950’s and predict a further decrease of up to 7 % of the current inventory by the year 2100 as a result of ocean warming and nutrient pollution [4].

There is a need for urgent CO2 emission reduction and decarbonization of our lifestyles and industries, but also a need to actively stabilize and/or restore the functioning of ecosystems in order to limit global warming to 1.5°C.  Sustainable green hydrogen production is one part of the solutions to decarbonize our lifestyles and industries.

Yet, during the production of 1 kg of sustainable green hydrogen, through electrolysis of water, 8 kg of oxygen are produced as a by-product. Our vision, at Lhyfe, is to give back this oxygen to the ocean to support its resilience and/or restore the functioning of marine ecosystems. In order to push this subject with a profound understanding of reoxygenation and its influences on the functioning of the ocean, Lhyfe started a collaboration with experts in physical and biogeochemical ocean modelling at Institut de recherche pour le développement (IRD) in Brest. A first article has just been validated and published in Environmental Research Letters (IOP Science) [5].

During this collaboration a coupled physical-biogeochemical numerical ocean model was used. It represents ocean currents, stratification as well as basic ecosystem cycles and interactions including oxygen, nitrogen and phosphorous. The oxygen produced during offshore green hydrogen production was then injected on an industrial scale, in dedicated areas based on predictions of population growth in coastal regions and wind energy potential. The impact of this oxygen on the regional and global oxygen inventory was then analyzed in the coarse resolution ocean model.

The results show, that the global oxygen inventory was slightly increased by 0.07% with strong variations in the regional responses. In the Bay of Bengal, situated in the Indian Ocean, the OMZ (Oxygen Minimum Zone) expanded, contrary to the global response, by up to 25% (table 1 in [5]) resulting from an increase in biological productivity. This increase is linked to changes in the region’s biogeochemistry, which affected the production of phytoplankton and other life (organic matter). After its lifecycle, the organic matter gets transformed by bacteria under the usage of oxygen in the mid depths (200-1000m). Hence, more production of organic matter leads to an increased oxygen uptake and to an increase in volume of the low oxic zone. Contrary, in the Atlantic and North Pacific a shrinking of the volume of the Oxygen Minimum Zones (OMZ), linked to the physical transport of oxygen into this area, was found. Depending on the oxygen concentration limits used to compute the OMZ the volume decreased by up to 30% within the 100 years of the experiment (table 1 in [5]).

The results show that industrial large scale artificial ocean reoxygenation could have an impact on the global OMZs and has to be treated with great care. Further studies are needed on a regional scale. Additionally, the technique how the oxygen is supplied (e.g. at which depth in the water column and where relative to the currents) can strongly influence the results as well.

At Lhyfe, we have the ultimate ambition to responsibly implement ocean reoxygenation as a measure to mitigate ocean deoxygenation.

So here are the next steps we’re committed to:

  • We will focus our collaborative efforts more on a regional scale, specifically the European shelf seas. They have been identified as a potential relevant zone for artificial ocean reoxygenation majorly due to their episodic to permanent low oxic conditions and the wind energy potential.
  • We will continue to build on previous knowledge and work with experts in the targeted regions as well as reoxygenation experts from both, research institutions and industry.
  • We will further and evaluate the technical options to inject oxygen to the sea.

While keeping the Unites Nations Decade for Ocean Science and Sustainable Development Goals ( in mind, we want to promote our vision of ocean reoxygenation as an environmental service of offshore hydrogen production. And we want to do it rather today than tomorrow. Our ambition is to build the sufficient science, legal and technological basis needed to pave the way for the effective implementation of ocean reoxygenation at our future industrial green hydrogen production sites.

(Regarding the Sustainable Development Goals of the UN, Lhyfe activities contribute to : 7 – Ensure access to affordable, reliable, sustainable and modern energy for all, 13 – Take urgent action to combat climate change and its impacts,14 – Conserve and sustainably use the oceans, seas and marine resources for sustainable development, 17  – Strengthen the means of implementation and revitalize the Global Partnership for Sustainable Development (



[1] Laffoley, D., Baxter, J. M. Ocean deoxygenation: Everyone’s problem-causes, impacts, consequences and solutions 2019 IUCN Gland, Switzerland

[2] Grégoire, M., Oschlies, A., Canfield, D., Castro, C., Ciglenečki, I., Croot, P., Salin, K., Schneider, B., Serret, P., Slomp, C.P., Tesi, T., Yücel, M. (2023). Ocean Oxygen: the role of the Ocean in the oxygen we breathe and the threat of deoxygenation. Rodriguez Perez, A., Kellett, P., Alexander, B., Muñiz Piniella, Á., Van Elslander, J., Heymans, J. J., [Eds.] Future Science Brief No. 10 of the European Marine Board, Ostend, Belgium. ISSN: 2593-5232. ISBN: 9789464206180. DOI: 10.5281/ zenodo.7941157

[3] Canfield, D. E. (2005). The early history of atmospheric oxygen: homage to Robert M. Garrels. Annu. Rev. Earth Planet. Sci.33, 1-36.

[4] IPCC, 2021: Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [Masson-Delmotte, V., P. Zhai, A. Pirani, S.L. Connors, C. Péan, S. Berger, N. Caud, Y. Chen, L. Goldfarb, M.I. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J.B.R. Matthews, T.K. Maycock, T. Waterfield, O. Yelekçi, R. Yu, and B. Zhou (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, 2391 pp. doi:10.1017/9781009157896.

[5] Beghoura, H., Gorgues, T., Fransner, F., Auger, P-A., Memery, L., Contrasting responses of the Ocean’s Oxygen Minimum Zones to artificial re-oxygenation 2023 Environmental Research Letters  Url:


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About Lhyfe

Lhyfe is a European group devoted to energy transition, and a producer and supplier of green and renewable hydrogen. Its production sites and portfolio of projects intend to provide access to green and renewable hydrogen in industrial quantities, and enable the creation of a virtuous energy model capable of decarbonising entire sectors of industry and transport.

In 2021, Lhyfe inaugurated the first industrial-scale green hydrogen production plant in the world to be interconnected with a wind farm. In 2022, Lhyfe inaugurated the first offshore green hydrogen production pilot platform in the world.

Lhyfe is represented in 11 European countries and had 149 staff at the end of 2022. The company is listed on the Euronext market in Paris (ISIN: FR0014009YQ1 – LHYFE).



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