Nutrient-sucking seaweed on clean-up duty in one of New Zealand’s dirtiest waterways – Stuff

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A seaweed trial could prove a game-changer in water restoration, says AgriSea managing director Tane Bradley, right. Hes pictured with, from left, University of Waikato scientists Chris Glasson, Marie Magnusson, and Clare Bradley.

Seaweed could be the key to cleaning up some of New Zealands dirtiest waterways.

Nearly $1m has been poured into a trial soon to start in the Waikatos Waihou River, testing how well the seaweed can filter its water.

This will be New Zealands first land-based seaweed trial, and three tanks of the plants will grow for 12 months, drawing water from the estuary, with data collation and analysis to follow.

If successful, AgriSea managing director Tane Bradley said it could become a game-changer in water restoration on top of growing seaweed that can be used for other products.

The Paeroa seaweed innovation company began experimenting with seaweed 26 years ago, manufacturing high-value macro-algal products to boost plant immunity, for animal and human health on farms.

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WAIKATO REGIONAL COUNCIL

Waikato Regional Council prosecuted a company responsible for an effluent discharge into a tributary of the Waikato River that turned a waterfall green.

Now, with the backing of Ministry for Primary Industries Sustainable Food and Fibre Futures fund, the company alongside University of Waikato scientists will expand into environmental restoration with trials to begin in June.

Theres so much you can do with seaweed, Bradley told Stuff.

We are really pushing the boundaries with this, bringing technology that is already existing and readapting it to New Zealand and seeing were it can benefit us.

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Seaweed will be used to clean excess nutrients from the Waihou Estuary in the project, a process known as bioremediation.

Seaweed, unlike many plants, doesnt have root systems and grows by pulling nutrients from the surrounding water.

The seaweed in tanks will act in the same way, filter feeding on excess minerals like nitrogen, phosphorous and other heavy metals currently unable to be soaked up by freshwater plants.

The water will then be returned to the sea, filtered and clean.

Similar models have been used in Australia alongside prawn farms to clean defecation, but this will be a first for New Zealand, Bradley said.

It is estimated that up to 50 tonnes of dry ulva seaweed per hectare could be produced from a scaled-up facility, providing the biomass for added value products.

I can see hectares of these machines being built all down the country.

The Government has invested more than $697,000 into the project through the Ministry for Primary Industries Sustainable Food and Fibre Futures fund.

AgriSea is contributing $108,000 and the Agricultural and Marketing Research and Development Trust (AGMARDT) is investing $150,000.

Thames-Coromandel District Council is gifting the land lease for the project term, worth $40,000, with support from Ngti Maru and Ngti Hako. Hauraki District Council and Te Waka are also assisting with the consent process.

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Similar models have been used in Australia alongside prawn farms to clean defecation, but this will be a first for New Zealand, AgriSea managing director Tane Bradley said.

Agriculture Minister Damien OConnor said this research supports many of the goals set out in Fit for a Better World, the Governments 10-year food and fibre sector roadmap aimed at lifting productivity, sustainability and creating jobs to drive New Zealands economic recovery from Covid-19.

If successful, this will be an environmentally-friendly way to improve water quality, create jobs in the science sector, revitalise our waterways and improve our on-land farming systems Damien said.

Bradley estimates the potential value of the project as up to $219,000 per hectare of production each year.

This is based on nitrogen credits coming into effect in New Zealand and the value of ulva-based products which are on AgriSeas Innovation pipeline," he said.

While New Zealand doesnt yet have a nitrogen trading scheme, if one was introduced the biomass produced in one year from one hectare of ponds would be worth $82,000 in nitrogen credits, based on international values for nitrogen trading.

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Three ponds totalling 60 square metres will grow the locally present green seaweed species ulva.

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Nutrient-sucking seaweed on clean-up duty in one of New Zealand's dirtiest waterways - Stuff