Offshore aquaculture: the future of algae farming

06-Nov-2024

In the wave pool, the Braunschweig scientists have recreated the seaweed farm on a scale of 1:20.

Kristina Rottig/TU Braunschweig

Aquaculture is the world's fastest growing food sector. In order to meet the increasing demand, solutions are needed outside of coastal waters, which are polluted by shipping, tourism and the expansion of coastal structures. The international joint project "Ngā Punga o te Moana - Anchoring Our Open Ocean Future", in which TU Braunschweig is involved, addresses precisely this issue. It aims to shift aquaculture from congested coastal regions to open, exposed offshore areas. Experts from the fields of hydraulic engineering, statics and marine biology are working together to develop technologies that can withstand the extreme conditions on the high seas.

The relocation of aquaculture to offshore areas has tangible benefits. Offshore locations offer more space for expansion, cleaner and cooler water, less marine animal fouling of farming structures and an abundant food supply for farmed species. In addition, aquaculture here has less negative impact on the seabed habitat. "This means that the agricultural potential of the open sea could be tapped," says Professor Nils Goseberg, Head of the Leichtweiß Institute of Hydraulic Engineering at TU Braunschweig.

However, these areas also pose significantly greater challenges: Deeper waters, stronger currents and higher waves place high demands on the stability and resilience of aquaculture facilities. A crucial aspect is therefore the precise determination of the forces acting on the infrastructure in order to avoid oversizing, which leads to high costs for the anchors and their components, as well as undersizing, which would result in the system failing during storms. Greater distances from the coast also have an impact on the cost of travel and maintenance, which requires low-maintenance systems.

Innovative seaweed farm off the coast of New Zealand

One of the aims of the international project "Ngā Punga o te Moana - Anchoring Our Open Ocean Future" is therefore to develop a new type of seaweed farm, which is to be installed as a prototype off the coast of New Zealand. Seaweed is extremely flexible and moves with the waves, which means that its surface area is constantly changing. "This additional dynamic makes it difficult to calculate the forces acting on the kelp and the entire farm - an aspect that has been insufficiently researched scientifically to date," explains project team member Henrik Neufeldt from the Leichtweiß Institute of Hydraulic Engineering.

The research work of the scientists at the Leichtweiß Institute of Hydraulic Engineering includes experiments in the wave channel and wave basin as well as computer modeling to analyse the behaviour of the kelp and farm structure under real conditions. In the first series of experiments, the researchers investigated the forces and movement of seaweed on longlines in the 2-meter wave channel. These are plastic ropes on which the seaweed grows, which are held to the water surface by floats and whose ends are anchored to the bottom. Substitute bodies with the same stiffness and thickness were created to realistically reproduce the deformations of the seaweed. "The shape was also modeled on seaweed," says Henrik Neufeldt. Special sensor systems, such as the particle tracking velocimetry (PTV) system, record the flow field around the structure, while the forces acting on the plants are determined by so-called load cells.

The aim of the series of experiments is to find out how the forces and movements of the seaweed change under different wave conditions and how neighbouring cultivation lines influence each other. These findings are incorporated into computer models in order to check and further optimize the load determination for the overall system.

Realistic offshore conditions in the wave pool

In a second series of experiments in the wave pool, the Braunschweig scientists recreated the kelp farm on a scale of 1:20. The focus here was on determining the usability of the system under realistic offshore conditions. Different materials for the head lines, which connect the cultivation lines and thus serve as connection points between the anchor and the farm, as well as different types of anchoring systems were tested to ensure optimal conditions for kelp growth. "The tension and stability of the lines are particularly important to ensure consistent growth conditions in terms of light and nutrients," says Henrik Neufeldt. By combining force sensors, wave levels, speed sensors and motion tracking cameras, the researchers were able to record and analyze the deformations and movements of the system in detail.

The overarching goal of the research is to make offshore aquaculture sustainable and efficient in order to meet the growing demand for marine resources - always with an eye to ecological responsibility. By developing new technologies, the future of aquaculture should not only open up enormous production opportunities beyond pure food production, but also help to protect the marine environment.

Project data

The open ocean aquaculture project led by the Cawthron Institute in New Zealand, "Ngā Punga o te Moana", is a five-year (2021-2026) national research program. The project is funded by the New Zealand Government's Endeavour Fund with around 11 million New Zealand dollars and aims to overcome the challenges to enable the expansion of the aquaculture industry into the open ocean. Researchers from New Zealand, USA, Ireland, Chile, Norway and Germany are involved in the international project. TU Braunschweig is involved with the Leichtweiß Institute of Hydraulic Engineering in cooperation with iTUBS, the innovation company of TU Braunschweig.

Note: This article has been translated using a computer system without human intervention. LUMITOS offers these automatic translations to present a wider range of current news. Since this article has been translated with automatic translation, it is possible that it contains errors in vocabulary, syntax or grammar. The original article in German can be found here.

https://www.yumda.com/en/news/1184831/offshore-aquaculture-the-future-of-algae-farming.html