Can offshore wind power improve the Baltic Sea environment?

At several of the offshore wind farms under development in the Baltic Sea, the plan is to store the generated energy as hydrogen. This process generates large amounts of oxygen as a by-product. Researchers at IVL Swedish Environmental Research Institute have explored the possibility of using this resource to improve the environmental situation along the deep seabeds of the Baltic Sea.

Despite extensive measures to reduce nutrient inputs to the Baltic Sea, the oxygen situation in the deep areas of the Baltic Sea is still very difficult. At virtually all depths beyond 70 metres, oxygen levels are so low that they negatively affect marine life. For example, several of the areas where cod used to spawn are so oxygen-depleted that the conditions for effective reproduction are no longer present.

"The idea of artificially oxygenating the Baltic Sea in order to improve its environment is not new, but with the large-scale investment in offshore wind power that is planned, the conditions have changed radically, as hydrogen production would generate enormous amounts of pure oxygen. In the study, we calculated the oxygen demand of the Baltic Sea and compared it with the amounts of oxygen that would be generated by the planned wind farms, and we concluded that there is considerable potential", says Magnus Karlsson, project manager at IVL.

In North America, the practice of oxygenating lakes and reservoirs using various technical systems is well proven, but the technology has not been tested in the brackish water environment of the Baltic Sea, and not on the scale that is now being considered.

"We have reviewed the existing literature on oxygenation, and our assessment is that it would be possible to use microbubble technology to dissolve the large amounts of oxygen involved. However, the method would need to be tested and evaluated under controlled conditions on a pilot scale to see if it really works. We have calculated and sketched out the technical conditions for how such a unit could be constructed in a limited coastal area with conditions similar to those in the open Baltic Sea", says Joakim Hållén, engineer at IVL.

Although the presence of oxygen is a requirement for higher life in aquatic systems, it is not clear that oxygenation is an appropriate measure in the Baltic Sea. For example, opinions are divided as to whether an improved oxygen situation would lead to an increased immobilization of the nutrient phosphorus in the bottom sediments and whether this in turn would lead to a reduced production of phytoplankton in the water mass, which drives eutrophication. Some scientists also question whether an increase in benthic fauna, which would be a direct consequence of improved oxygen conditions, would in practice mean improved food resources for ecosystem-important fish species such as cod and herring.

"Clearly, the method needs to be carefully tested and evaluated on a smaller scale over several years before it can be considered for a larger-scale programme in the open Baltic Sea. But it would be a shame not to open-mindedly explore whether the method is effective, as it would be extremely resource- and energy-efficient compared to many other measures that society is currently taking to mitigate the effects of eutrophication", says Magnus Karlsson.

Download the report: Artificial oxygenation of the Baltic Sea External link, opens in new window.

For more information, contact:
Magnus Karlsson, magnus.karlssson@ivl.se, tel. +46 (0)10-788 66 03
Joakim Hållén, joakim.hallen@ivl.se, tel. +46 (0)10-788 65 54

The study was funded by the energy park developer OX2 with government co-financing via IVL's research foundation SIVL.