Last year, China installed more offshore wind capacity than any other nation for the third year running. This year it is set to overtake the UK as the largest offshore wind market. With the sector booming, some are looking at opportunities beneath the turbines. Could their bases be turned into aquaculture farms or “marine ranches” – habitats where marine life can live, breed and be harvested for human consumption?
So far, no mixed wind power and marine ranching projects have been completed in China. Projects are being built in provinces including Shandong, Jiangsu and Zhejiang, according to the Ministry of Agriculture. If successful, they could enable more efficient use of limited space at sea, help develop fishery resources, and support more sustainable development.
But it is too soon to talk of a large-scale roll-out. There are currently no China-specific research findings on how the wind and seafood elements affect each other, and many questions remain to be answered. How, for example, will the noise of building and operating a wind farm affect marine life?
The advantages
Most of China’s offshore wind power potential is concentrated around the southeastern coast and nearby islands, where the water is between 5 and 50 metres deep, according to the 2019 China Renewable Energy Development Report. Some of this area is suitable for marine ranching.
China’s marine aquaculture is already relocating from coasts and shallow waters out into deeper waters. Aquaculture takes up large expanses of shallows and wetlands, and intensive operations pollute the ocean. Central government has therefore ordered a clean-up, meaning aquaculture will be pushed further offshore, into wind power territory.
‘Aquaculture’ vs ‘ranching’
Marine aquaculture involves farming sea life in enclosures, and relies on continued input of materials such as feed and fingerlings. Marine ranching, by contrast, involves creating environments suitable for life, allowing it to grow naturally and then harvesting the resulting seafood. Some marine ranching projects involve rehabilitating damaged habitats using artificial reefs.
Marine ranching is being seen as way to upgrade the sector and even help restore the ocean environment. Wang Songlin, president and founder of the Qingdao Marine Conservation Society, told China Dialogue that most aquaculture farms and marine ranches are found near the coast, in waters up to 20 metres deep. There are some ranches in waters 40 metres deep near islands, but none deeper than 55 metres.
Combining wind power with aquaculture or ranching could benefit companies on both sides. Aquaculture firms can use the turbine bases to anchor fish cages or rope-and-raft systems for growing shellfish and kelp. The base itself could be turned into an artificial reef for fish, oysters or kelp, and any power needed to run the aquaculture farm or marine ranch could be drawn directly from the turbines.
For the wind power firms, making fuller use of the site would reduce maintenance costs and they could sell some of the power they generate to the aquaculture firms.
The combination could also help China make better use of its ocean. He Guangshun, director of the National Marine Data and Information Service, wrote in a 2019 research paper that “the ocean is three-dimensional, with differing geographical and environmental conditions across the air, water and seabed. A single site can be suitable for energy, shipping and fishing.” Combining these activities would allow for more intensive use of space.
Global and domestic practice
Bidding for the chance to construct China’s first purpose-built offshore wind and marine ranching project began in 2019, with a 300-megawatt (MW) project in Shandong’s Laizhou Bay. In 2020, construction started on a pilot project in Yangxi county, Guangdong. Meanwhile, in the city of Dongfang, Hainan bids were solicited to do feasibility studies for a similar 500 MW project. Of these three, construction of the first two is expected to finish in 2024. It is not yet known when the third will be done.
Currently, the only completed project claiming to combine offshore wind with marine ranching is in Pingtan, Fujian province. It was initiated by CGN New Energy, with participation from the Fujian Fisheries Research Institute and a local aquaculture firm. That firm placed metal cages containing 1,500 juvenile fish near the base of one of the turbines, 28 metres down. The fish are regularly fed and checked up on. Mussels and abalone are also raised on the concrete base the cages are attached to.
But an expert familiar with aquaculture and ranching says marine ranches are about creating or restoring good underwater environments for aquatic life to prosper, with the primary aim of sustainable production without the need for inputs. “The term ‘marine ranch’ is a stretch if you are using cages and providing feed.”
The term ‘marine ranch’ is a stretch if you are using cages and providing feed
The mixed wind power and aquaculture model is more common overseas. European countries such as Germany, the Netherlands, Belgium and Norway started trialling it in 2000, fixing fish cages and shellfish and kelp rafts to turbine bases, as Yang Hongsheng, deputy head of the Chinese Academy of Sciences’ Institute of Oceanology, explained in a 2019 article. Asian countries, such as South Korea, got started in 2016, finding that valuable seafoods such as kelp, mussels and scallops increased around offshore wind farms.
Increases in marine organisms like kelp can be one of the benefits of projects like these. “Kelp fixes carbon and provides a habitat for small fish and shrimp,” said the aquaculture expert. That could mean it is possible to use aquaculture as a basis for promoting the development of more eco-friendly marine ranches.
Hopes and concerns
Turbine bases attract fish, much like artificial reefs, said Yue Weizhong, a researcher at the Chinese Academy of Sciences’ Institute of Oceanology, in an interview with the journal Fishing and Fisheries. When ocean currents meet turbine bases and semi-submerged platforms, water is diverted upwards, taking seabed nutrients with it. That encourages growth of phytoplankton, or microalgae, which attracts other ocean life. On the other side of the base, eddies form where water flows more slowly, which suits certain fish. The eddies can also bring together phytoplankton and crustaceans with fish.
An example in the Netherlands has demonstrated the potential of offshore turbines to attract marine life. Biodiversity has increased at the Egmond aan Zee offshore wind farm, with new or larger populations of oysters, sea anemones and crabs appearing at the turbine base and nearby rocks, according to a two-year study.
The key factor in those changes may in fact be the lack of human activity, coupled with changes to the seabed. On the busy Dutch coast, a wind farm is a relative oasis of peace and quiet, free from commercial fishing, oil extraction and shipping. The turbine bases also offer the kind of solid habitat shellfish prefer attaching to, when compared to the softer seabed found locally.
But with little research or practice to refer to, many questions still hang over the offshore wind and marine ranching model. In his 2019 paper, Yang Hongsheng raised several issues: Do turbine bases really attract marine life in the same way artificial reefs do? How should the management of the ranch and the wind farm be coordinated? What effect will the noise, vibration and electromagnetic fields produced during construction and operation of the wind farm have on marine life? According to his paper, wind farm noise can be sensed by cod and herring four kilometres away, and by flounder and salmon a kilometre away, and those noises may affect fish behaviour and biology.
The government is not currently pushing ahead with integrated offshore wind and marine ranching development. In a response to a comment from a National People’s Representative, the Ministry of Agriculture said academics are studying how the two operations could work together, but there are no findings yet. “Establishing the impact of wind farms on the fishery resources in marine ranches will require long-term monitoring and evaluation. It is too early for the state to put the necessary policies and plans in place,” its statement said.
It may come down to the success of the local trials. The ministry is to continue monitoring these and will, in partnership with the National Energy Administration, carry out research into how the turbines and ranches interact. Meanwhile, the Ministry of Natural Resources is looking into managing usage rights at different ocean levels, to allow for more precise management of marine resources.
