Offshore Solar and the Environment:
The Perspective of Blue Carbon

One of the key initiatives of the European Commission’s Green Deal is the Net Zero Initiatives Act (NZIA), a provisional framework of measures established to capture and effectively store 50 million tons of carbon dioxide (CO2) per year by 2030. Reducing carbon emissions is simply not enough to curb the effects of climate change, so carbon capture and storage (CCS) of ambient CO2 is a necessary additional step to limit global warming. Removing carbon from the environment can be done in a few different ways. For industrial processes with high emission rates, the most effective method is to extract CO2 before it is even released into the atmosphere, and then store it underground.

But what about the CO2 already released?

More than half of all carbon emissions from human activities are captured and stored through the metabolic processes of organisms in the sea and on land. When CCS occurs extensively in marine environments, this is known as blue carbon, a concept that is increasingly gaining traction and the reason why it is so important to continue promoting the conservation of key blue carbon habitats like seagrass meadows, mangrove stands and …mussel/oyster beds!

How can offshore solar play a part?

Inherently, the development of marine energy renewables, like offshore solar, offset carbon emissions by producing clean energy; a pivot away from humanity’s reliance on fossil fuels and a step towards net zero targets. But it might also contribute to CCS through natural means. In one of our previous posts, we discussed how Oceans of Energy’s platforms act as floating reefs that host a mussel community attached beneath. On our North Sea projects, we have observed a 10- to 15-centimeter-thick layer of mussels on the floater undersides.

As they grow, shellfish (like mussels and oysters) take dissolved CO2 from the ambient seawater and convert it into calcium carbonate, an essential element in their shell production. In this way, they act as a blue carbon sink; once the shells are formed, the carbon is permanently stored. Mussel beds are also known to sequester (bury) organic carbon in the seabed sediment. According to the European Environment Agency, blue mussels (Mytilus edulis, the most prevalent mussel species in the North Sea) sequester around 15 grams of carbon per square meter per year.

Oceans of Energy designs solar farms with an anticipated lifespan of 25 years. Throughout this lifespan of a farm, blue mussels (and other species) will continue to grow and attach to the underside of the floaters, so we anticipate. During storms and through natural processes, some mussels will be dislodged and settle to the seafloor. When this happens over and over again, and on a large scale, the mussels bind together and form a complex hard structure on the seafloor, eventually becoming a place where more mussel larvae attach and grow, forming a mussel bed. Over 25 years, many thousands of kilograms of mussels will be able to grow and capture blue carbon.

The potential for our floating structures, to help restore hard substrates on the seabed, is truly exciting and a research topic we really want to dig into. Oyster reefs and mussel beds are essential for a healthy, rich underwater North Sea life, and the restoration of these habitats  therefore a focus in the Dutch policy (Natuurambitie Grote Wateren, Uitvoeringsagenda Natuurlijk Kapitaal).