Agrisea Bioremediation Project

Agrisea is an innovation driven operation, producing seaweed-based products from food additives to skincare. They’re well-known for animal nutrition products, and soil supplements, including biostimulants that are used by farmers, beekeepers, equestrians, and other sectors across our primary industries.  

Agrisea is driven by a commitment to provide better, more sustainable solutions for the land. The company has recently teamed up with scientists and other stakeholders to investigate growing seaweed (on land) for remediating polluted water. The results to date are very promising and it is hoped the technology will be readily picked up by others to help revitalise waterways and improve farm environments. 

The family-based company is helmed by CEO Clare Bradley with her husband, Chief Innovation Officer Tane Bradley. It has an ethos of providing sustainable solutions for farmers and others working on the land. Agrisea has a significant history of research and innovation behind their products. Research and development work is also undertaken with an aim to benefit their local community, Aotearoa, and the planet. 

The Hauraki Bioremediation Project is a recent collaboration that has resulted in a successful trial, using seaweed to clean up excess nutrients in a waterway close to their base in Thames. It has been supported by the Ministry for Primary Industries Sustainable Food and Fibre Futures fund, the Agricultural and Marketing Research and Development Trust (AGMARDT), Agrisea, and the Thames-Coromandel District Council, with the blessing of local Iwi. University of Waikato is the research partner and has conducted extensive tests during the trial. 

The project came about when Tane was visiting the University of Waikato Coastal Marine Field Station in Tauranga.  (Agrisea regularly collaborates and contributes to research with Associate Professor of Aquaculture Dr Marie Magnusson and Professor Chris Battershill among others). Tane was intrigued by a bioremediation set-up with seaweed being used to absorb excess nutrients to clean polluted water. He wondered if a similar system might be able to clean up some of the polluted water flowing from the Waihou River into the Thames estuary.  

Of particular concern to the Bradleys is nutrient run-off. Both are quick to say this is not a blame game. They acknowledge land use impacts on water are a challenge and believe it is the responsibility of all who either work on the land, or benefit from the food and products produced from it. 

Marie Magnusson explains, “Bioremediation technology is already in use internationally and has been proven for point source discharges, like land-based prawn and abalone farms, but this concept is about cleaning up nutrients from diffuse sources.” Diffuse sources are those where contaminants are coming together from multiple places and reach a scale where they’re problematic at points, such as estuaries. 

Alongside Clare and Tane, the scientists visited the Firth of Thames where the Waihou flows into the ocean. Their assessment was that there was a real possibility of using a bioremediation system to address water quality issues in the area. Thames Valley District Council were as excited by the potential as Agrisea, and meetings were held with local iwi, and applications made for trial funding. A trial plant was established at Kopu near the Firth of Thames and has been in operation since 2022. 

Water is taken from the Waihou River, prior to the point where it enters the estuary, and is directed through three large bioremediation tanks. Each tank is seeded with a local species of sea lettuce (Ulva australis). Like most seaweeds, sea lettuce has no roots but feeds directly on nutrients in the water – removing nitrogen, phosphorous, some heavy metals and potentially other contaminants. The water ‘filtered’ by the sea lettuce is then returned to the river. 

Three tanks were set up to measure the efficiency of different flow rates and different amounts of seaweed (‘stocking density’) to determine what the best parameters are for removing excess nutrients. Seaweed was harvested weekly, with the tanks resown with young seaweed grown from spores in the University of Waikato hatchery in Tauranga. Agrisea Research Technician Taylor Moore collected the samples for testing by Marie at her lab. 

The harvested sea lettuce was dried and weighed at the Agrisea workrooms in Paeroa. Water samples from the input and outputs on each tank were collected twice weekly for comparison testing of nutrient levels, such as dissolved inorganic nitrogen (like nitrate) and phosphorous. These were sent across to Marie’s lab along with the bales of dried seaweed for chemical analysis and measurement. 

Alongside the environmental benefits of cleaner water, there is additional value in the harvested seaweed. It is anticipated that it could form part of a circular economy where it would be on-sold for use in a range of products from fertiliser to food.  

Tane believes any future bioremediation plants will be able to set up a tender process to get the best price for the biomass harvest to off-set costs.  

The initial trial is now winding up with highly encouraging data. Tane notes, “Everyone was blown away by the results. I’m not sure any of us expected the sea lettuce to be so effective at absorbing nitrogen and phosphorous.”  Results of the filtered water showed reductions of 90% of nitrates and 70% less phosphorus. 

Agrisea are now working to get the backing required to scale up the technology. They’re clear that it is not a business-driven model for the company, and they are not interested in owning the IP, but about working for a better environment. The Bradley’s are adamant that their contribution to the research is driven by the opportunity to give back to their community, and to Aotearoa. They want to see the technology adopted by organisations like councils, in areas where it can have an impact. The infrastructure is affordable and will likely include the need for hatcheries to produce the seaweed spores.  

“We’ll need technicians to run the set-up and hatcheries. We anticipate the opportunity for good jobs for young people in provincial areas will be another positive outcome of this work,” said Clare.