Artificial oxygenation of the Baltic Sea: Prerequisites for a pilot study in a sheltered archipelago bayShow others and affiliations
2024 (English)Report (Other academic)
Abstract [en]
Despite extensive measures to reduce the supply of nutrients to the Baltic Sea, the oxygen situation in the deep areas of the Baltic Proper is still very strained. Practically, in all water depths that exceed 70 meters, oxygen concentrations are so low that higher animal life cannot thrive. Moreover, the conditions for the nutrient phosphorus to be retained in the sediments are reduced at low oxygen levels. Some researchers believe that the Baltic Sea is stuck in a vicious circle. As long as there is a lack of oxygen, phosphorus circulates in the system and perpetuates the production of microalgae and cyanobacteria, leading to continued strained oxygen conditions as oxygen is consumed in the decay of the seston.In the transitioning to fossil-free energy production, large offshore wind farms are planned to be built in the Baltic Sea. In some of these, hydrogen gas production on-site through electrolysis is a part of the process concept. Hydrogen production on these scales releases substantial amounts of oxygen as a by-product, which could potentially be used to oxygenate the oxygen-depleted bottoms of the Baltic Sea. Artificial oxygenation, dissolving pure oxygen gas in the water mass, is common in North American inland waters but has never been tested in a coastal sea like the Baltic Proper.
This report discusses the potential and challenges of implementing large-scale oxygenation measures in the Baltic Proper. Existing oxygenation techniques were evaluated to determine the most suitable ones to establish on the Baltic Sea scale. Using the Bornholm Basin in the southern Baltic Proper as a study case, we calculated the oxygen demand to maintain oxic conditions over time and compared it with the output from a tentative wind park. Furthermore, Slätbaken Bay, an enclosed coastal area in the archipelago of the central Baltic Proper, was identified as an appropriate site for a pilot experiment to test and evaluate the oxygenation technique in a brackish environment. Assuming three years would be sufficient to assess oxygenation's pros and cons, we pre-designed a land-based technical system to oxygenate the bay using the microbubble technique (DOI). The cost to establish, run, and evaluate a three- year pilot study was estimated to be 25 MSEK.
Undoubtedly, there is immense potential if the excess oxygen from large-scale hydrogen production can mitigate eutrophication's effects in the Baltic Sea. However, it is necessary to test oxygenation under controlled conditions for a sufficient time before implementing the technology on a larger scale.
Place, publisher, year, edition, pages
Stockholm: IVL Svenska Miljöinstitutet, 2024.
Series
B report ; B2493
Keywords [en]
eutrophication, oxygenation, hypoxia, phosphorus, benthic fauna, Baltic Sea
National Category
Environmental Sciences
Identifiers
URN: urn:nbn:se:ivl:diva-4442ISBN: 978-91-7883-623-9 (electronic)OAI: oai:DiVA.org:ivl-4442DiVA, id: diva2:1907138
Funder
IVL Swedish Environmental Research Institute2024-10-212024-10-212024-10-21