Why Seaweed?

When I tell people I want to grow seaweed, they ask "What for?" and often follow up with "For sushi?"

Graham Harris  is a key member of the ReGenSea team and has an extensive background in the seaweed industry.

Graham Harris is a key member of the ReGenSea team and has an extensive background in the seaweed industry.

The answer is "Yes, and..."

There are very many kinds of seaweed, and just as many things you can do with them. Several kinds are delicious to eat as well as very healthy. I will blog about eating seaweed at another time. Seaweed as sea vegetables are just a part of a very diverse picture.

I like to think of it as a casdade of different uses, for different species, farmed in different places.

New Zealand is a long, thin country with ocean temperatures spanning a range from the sub-tropical to the sub-Antarctic. This gives us a huge range of native species we could farm, some with uses we already understand well, and some with uses just being researched and discovered now.

One emerging area is as food for livestock. This has been usual in parts of northern Europe for centuries, where stock have been turned onto the beaches to feed on washed-up seaweed. More recently, several sets of scientists have reported that some seaweeds have benefits beyond just replacing other feeds. Quite small amounts added to the usual diet can change cattle's gut bacteria to produce dramatically less methane. 

Other seaweeds are also effective against worm parasites, and livestock seem to enjoy them. All seaweeds bring from the sea a variety of key minerals like selenium, which we need in food but our soils lacks. Feeding seaweed to our livestock may therefore aid in nutrition, whilst avoiding the import of palm kernel, or using traditional fertiliser to grow feed crops.


Speaking of fertiliser, several Kiwi companies are already producing organic fertilisers (or biostimulants) made from seaweed. Currently, their seaweeds are collected from beaches or from mussel farms. These businesses are limited by their supply of seaweed, and we would like to work with them to improve their supply so they can expand production, reduce costs and export more product. The complex biochemicals in seaweed stick to the soil for slow release, rather than washing into streams like artificial fertilisers do. They build and enhance the soil as well as providing the nutrients for the growing crops. Changing to seaweed based fertilizers could also dramatically impact greenhouse gas emmisions from farms.

1L Milk ~ 1kg CO2


59 % of emissions = Methane (Cows),

17 % are Carbon Dioxide (Various),

24 % are Nitrous Oxide (Fertiliser)

There are effective ways to make farming profitable while achieving good environmental outcomes.

There is much that we can do in NZ to put in place effectual measures to reduce the application of such large amounts of nutrient (and in particular N and P) , and to apply them in bio-friendly and less water-soluble forms.
— Graham Shepherd of BioAgriNomics

Estimates and Quotes adapted from articles published in STUFF 17 JULY 2019 and 19 APR 2017.

Towards the top end of the value cascade of seaweed products, come the nutraceutical uses. Just as seaweeds can provide valuable nutrition to animals, they can also add valuable nutrients to our diet that we don't easily get elsewhere.  Nutraceutical simply means that these supplements are formulated so they don't look or taste like seaweed - also that you don't need to consume much to gain the benefit.  Seaweeds are rich in vitamins, minerals, anti-oxidants, carotenoids and even omega-3 oils and many health benefits are being studied worldwide.

Importantly, seaweed’s ability to act as an effective carbon sink is very promising, a topic that is getting widespread media attention. Other exciting uses for seaweeds are also being pioneered. Companies in Europe and Indonesia are successfully producing fully biodegradable plastics using seaweed as source material and research into seaweed’s use as renewable source for biofuel (bio-ethanol for cars ) and biogas (renewable electricity) is also expanding.   All of these industries continue to reduce our reliance on fossil fuels, thereby reducing our overall carbon footprint.

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Seaweed as a product is therefore increasingly useful from an ecological, food and fuel perspective. 

And, Just to be clear, I am interested in the regenerative farming of seaweed.

Harvesting fragile natural beds of seaweed is very heavily restricted, for good reason. Many of our native fish and shellfish depend upon thriving natural seaweed beds for food, shelter and reproduction. Seaweed farming depends on fertile natural beds for the seed farmers will plant out. We need to ensure we are not damaging those natural stocks - in fact over time, farms should become sources of seed to rebuild natural stocks already depleted. 

Farming seaweed can be productive and ecologically positive. 

I hope to help the New Zealand’s seaweed industry achieve these objectives.

Graham HarrisComment