In a New Zealand first, a waterway-cleaning seaweed trial was officiated at Fieldays last Thursday by Agriculture Minister Damien O’Connor, marking the beginning of a potential solution to several issues confronting the sector.
The seaweed, called Ulva, which has been trialed by Agrisea for several months, absorbs excess nutrients like nitrogen and phosphorus from polluted waterways to aid its growth, and then the biomass can be used as fertiliser after being harvested.
The current pilot is located at the rivermouth of the heavily-polluted Waihou River, which Agrisea research technician Taylor Moore says was the perfect location for the research programme to take place.
“We’re drawing water from the Waihou River system at high tide, so it’s got some saltwater and freshwater inputs,” he said.
“It needs the freshwater for those excess nutrients that are flowing down. As the Waihou River is one of the worst polluted rivers in the country, there needs to be something to buffer the impact of those land industries up the river coming into these marine ecosystems.
“We pump it through our pond systems, and the species we use of Ulva sucks up all of these nutrients and incorporates them into its tissue during normal growth.
“And then when the seaweed is removed from our pond systems, those excess nutrients are taken with it.
“This would be tackling this excess nutrient issue from both ends. We’re drawing them out from the mouth of the river, and then you’re able to turn that product into the seaweed biomass which could then help farms reduce some of their nitrogen and phosphorus inputs.”
Taylor Moore
Moore says that although there are several viable uses for the seaweed, it would be best used as a biostimulant to partially replace certain fertilisers. When used as a biostimulant, the product works with the soil biology to provide a balanced and more complete food source for the different microorganisms, resulting in healthier soils and subsequently plants.
“From Agrisea’s perspective it would be a great opportunity to use it as a biostimulant, which is in line with what we are already making – bio-stimulants out of seaweed and organic fertilisers out of seaweed,” Moore said.
“This would be tackling this excess nutrient issue from both ends. We’re drawing them out from the mouth of the river, and then you’re able to turn that product into the seaweed biomass which could then help farms reduce some of their nitrogen and phosphorus inputs.”
Agrisea has an open IP on the technology, as the hope is that farmers will get on board with growing the seaweed on unviable land as a passive income source.
Moore says that it could provide farmers with another income stream in two ways: one, through growing the seaweed and companies like Agrisea purchasing it from them, and two, from earning nitrogen credits.
“We would approach farmers and say, here’s all the information you need to grow this species, here’s all the supplies that we use, here’s the how-to guide on how to do everything, you set it up, you grow it and we will buy the seaweed back off of you,” he said.
“And then hopefully NZ will get into a position where we’re adopting nitrogen credits, like others have been overseas, in the same way that carbon credits are used.”
“From there a farmer would then be able to have a steady income stream from the nitrogen credits that they are producing.”
Moore estimates that from on a hectare scale, someone could remove up to two tonnes of nitrogen a year, with the international average sitting around $30 per kilo.
As well as that, the dried seaweed biomass is fetching around $2-6 per kilo depending on the quality, and one hectare scale could be producing up to 25 tonnes a year.
“So it will be quite a big capital investment, but your return on investment has the potential to be really high as well, as well as knowing you are making a positive impact on the environment by removing excess nutrients from the waterways (arawai).
The announcement included O’Connor’s praising of the project, as well as justification of the government’s contribution in funding through the Sustainable Food and Fibre Futures partnership (SFFF).
“This is about nutrient recycling, about clean water going out, capturing the nutrients and maybe being able to put them back out on the paddock, it really is game changing.” O’Connor said.
“We’ve put some of your money as taxpayers into it and I think it’s a great investment and I look forward to the results.”