Innovative plastic technology revolutionizes aquaculture

A Norwegian company has successfully implemented a pioneering aquaculture project. The Marine Donut, a closed, floating fish culture system made of the particularly tear-resistant plastic PE 100-RC, was installed on a salmon farm in Norway. This innovative system, supplied entirely by AGRU Kunststofftechnik GmbH, marks the beginning of a new era of sustainability in salmon farming.

With an outer diameter of 55 meters, a height of over 17 meters and a total weight of about 600 tons, the Marine Donut is the world's largest thermoplastic structure. The unique design of this floating fish hatchery has the potential to revolutionize salmon farming methods. The Marine Donut's outstanding design creates a controlled environment that reduces stress for the fish and allows them to grow healthier. Because of its durability and cost-effectiveness, this solution is intended to replace conventional mesh cages in the future. The Marine Donut accommodates up to 200,000 salmon weighing 2.5 kilograms, which remain in the facility until they reach their harvest weight of 5.5 kilograms. 

Groundbreaking innovations

The innovation of the Marine Donut lies in its closed structure. It makes it possible to protect salmon from parasites such as fish lice and keep them healthy. The discharge of filtered deep water prevents the introduction of salmon lice. Inside the plant, food waste and fish excrement are collected in the form of silt. This is then pumped ashore for environmentally friendly disposal. This process not only minimizes the environmental impact of salmon farming, but also prevents the spread of disease. 

Another striking feature of the Marine Donut is the use of an artificial flow channel that simulates a river. There is a permanent flow in the annular structure of the plant. Thus, the fish are constantly moving, which has a positive effect on their flesh quality. In addition, the structure is equipped with ballast tanks, which allow the donut to be raised and lowered or tilted in the sea. Fish ready for harvesting can be fed into an attached hose by tilting the structure and transported without injury to the factory ship for further processing.

Plastic technology from Austria

The Bad Hall-based company AGRU Kunststofftechnik GmbH played a central role in the implementation of this ambitious project. It produced and delivered all PE 100-RC components for the 22,000 m³ Marine Donut. Deliveries included 400 tons of agate gray and black PE 100-RC plastic sheets and 200 tons of PE 100-RC pipe systems and E-fittings with outside diameters of up to 1,200 mm. In addition, AGRU made a significant contribution through its extensive application technology consulting.

"We are proud that with our expertise and high-quality materials, we were able to make a significant contribution to the realization of this revolutionary aquaculture technology," explained Albert Lueghamer, AGRU Head of Technical Services. "The close cooperation with our customer and AGRU's in-depth knowledge of the challenges of plastic products in salt water contributed significantly to the successful implementation of the project."

To facilitate the handling of the plastic sheets during installation, AGRU manufactured them in a special format. At the construction site, the precise curvature of the sheets was ensured by bending on a circular formwork. Once they had the correct shape, the plates were joined together by butt-welding. The construction of the Marine Donut also uses special stiffening ribs made from black PE sheets. They are the result of a finite element calculation, which was performed for the precise strength and deformation analysis of the complex geometric shape.

Durability thanks to plastic

Peter Undeutsch, Head of Sales at AGRU, emphasizes the forward-looking importance of using plastics in marine applications. "The Marine Donut is a milestone in aquaculture and demonstrates the enormous potential of thermoplastics in this field. We will continue to use our extensive experience and knowledge in plastics technology to support the development of the aquaculture industry."