A student project, funded by the Exeter Marine Student Fund, exploring new techniques for seaweed farming on land.
Seafood is a crucial source of food and livelihoods for millions of people around the world; however global fish stocks are under pressure. The latest report from the Food and Agriculture Organization (FAO) shows that fisheries catches have plateaued, reflecting declining fish populations due to overfishing, a trend well known to scientists. To provide seafood, a vital source of protein, for a growing population, aquaculture is crucial. This industry, the farming of marine organisms, is growing rapidly and has the potential to help provide food security and employment worldwide.
But not all aquaculture is sustainable. Some systems can cause environmental damage through pollution or rely on inefficient feeding practices. Finding ways to farm seafood responsibly is key to meeting global demand while protecting the planet.
Why Seaweed?
Seaweed stands out as one of the most sustainable products in aquaculture. Its popularity in Europe is growing by 7–10%, a large proportion of which is consumed by humans. Seaweed is rich in vitamins, minerals, and bioactive compounds, making it an increasingly popular healthy food choice.
Beyond the plate, seaweed can also be used as feed in fish farms, making this practice more environmentally friendly. By substituting conventional feeds with seaweed, fish farms can reduce reliance on wild-caught fishmeal, which in turn decreases pressure on wild fish populations. Seaweed can also clean up aquaculture systems itself. In Integrated Multi-Trophic Aquaculture (IMTA), seaweed is grown alongside fish, using the waste produced by fish as food. This helps keep water clean and reduces environmental impacts, creating a more sustainable cycle.
However, currently in Europe over 99% of seaweed is still harvested from the wild. While wild-harvested seaweed is currently meeting demand, the increasing popularity of seaweed products means this approach may no longer be sustainable. To meet future demand while maintaining ecological balance, we need efficient and scalable methods of cultivating seaweed on land.
At the University of Exeter, in collaboration with the Cornish Seaweed Company, researchers have been developing tank-based systems for land-grown seaweed. These systems grow seaweed on vertical screens exposed to thin, flowing water. This method achieves roughly double the growth of traditional tank approaches while using far less water. So far, these systems have only been tested at a small scale (around 1–2 m²), scaling up this system requires addressing challenges in both efficiency and labour costs.
Scaling Up: Making Land-Based Seaweed Feasible
My project, supported by the Exeter Marine Fund, aimed to help scale up this system by making land-based seaweed aquaculture more efficient and cost-effective. I focused on two main areas:
- Reducing labour costs, and
- Choosing the most suitable seaweed for cultivation.
Both elements are critical if land-based seaweed farming is to become a commercially viable and sustainable method of production.
Cutting Costs with Automation
Labour costs are one of the biggest barriers to large-scale, sustainable seaweed farming. To tackle this, I used the awarded funds to build a prototype automated sensing system. This included a Raspberry Pi, an Arduino, and force sensor resistors (FSRs).
The Raspberry Pi is a small, energy-efficient computer that can run continuously for long periods. This makes it ideal for aquaculture systems, which may be located in remote or hard-to-access areas. The Raspberry Pi can be accessed remotely, reducing the need for daily site visits, a major source of labour cost.
I programmed the system to track three key pieces of information automatically: the weight of the seaweed, water temperature, and nutrient levels. This reduces the need for manual weighing and water testing, which are time-consuming and labour-intensive.
Testing showed the prototype could successfully record the increasing weight of seaweed as it grows over time. This proof-of-concept demonstrates the potential for automated monitoring in commercial systems, which could significantly reduce labour requirements and make land-based seaweed aquaculture more viable.
Choosing the Right Seaweed
Another key factor in successful seaweed farming is selecting the right seaweed species and populations. Different populations of the same species can develop different growth properties depending on the local environment in which they live. Understanding these differences can help farmers select the best seaweed for cultivation, improving efficiency and yield.
We focused on Ulva lactuca, commonly known as sea lettuce, collecting samples from Penzance, St Ives, and Falmouth. The goal was to identify which populations performed best in aquaculture systems.
There was found to be a large range of suitability within each location, suggesting that exact harvesting site along the shore is important when sourcing seaweed for cultivation. This finding could help refine harvesting strategies and improve the efficiency of land-based seaweed farms.
Next Steps
Future research at the University of Exeter can build on these findings by exploring how the precise location of seaweed on the shore affects its performance in aquaculture systems. For example, factors such as sunlight exposure, water flow, and local nutrient availability could influence growth and suitability for cultivation.
Regarding automation, nutrient dosing systems, which adjust nutrient levels in real time based on seaweed growth and water conditions, are currently being trialled. These systems could further reduce labour requirements, helping land-based seaweed aquaculture become a truly scalable and sustainable industry.
In addition, integrating data from multiple sensors could allow farmers to monitor growth patterns and predict harvest times more accurately, ensuring consistent quality and yield. This combination of automation and careful selection of seaweed could transform the economics of land-based aquaculture.
A Personal Note of Thanks
I would like to sincerely thank the Exeter Marine Fund for supporting this project. The work contributes to the development of sustainable, commercial land-based seaweed farming in collaboration with the Cornish Seaweed Company, and it helps inform strategies for harvesting seaweed effectively.
On a personal level, this project has allowed me to develop practical skills in coding, electronics, and experimental design, giving me valuable experience for a future career in sustainable aquaculture. I am extremely grateful for the opportunity to contribute to this exciting area of research.
Written by Benjamin Grecic
The Exeter Marine Fund has been designed to respond to the most urgent threats by bringing together small gifts to have a big impact when and where funding is needed. The Fund enables us to continue to play a crucial role in monitoring and protecting our marine ecosystems and shape positive change in practice, policy and innovation, and has successfully funded a number of student research projects over the last few years.
If you’d like to talk to us about supporting a particular area of marine research, please email alumni@exeter.ac.uk or call +44 (0)1392 723141.