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The Seaweed Solution

Giant kelp. Photo by Shutterstock

Seaweed is having a renaissance. For years it has been undervalued; out of sight, out of mind. However, researchers around the country and the world have begun to explore its amazing potential as an alternative to many products and practices which are proving to be unsustainable in the long-term.

The seaweed industry is growing rapidly. Not only in food production where it currently accounts for $5 billion worldwide, but also in the medical and agricultural sectors. In Australia, research into seaweed is still in its infancy, but there are many exciting findings suggesting that seaweed may become a solution to many problems affecting our planet.

Oceans cover 71 per cent of the earth’s surface and with overpopulation and the destruction of natural ecosystems, it makes sense to utilise this vast space as a resource for our growing needs. As well as farming seaweed in our oceans, scientists are exploring potential methods of farming it in man-made ponds and pools.

So what is it that makes seaweed so special? Seaweed acts as a biofilter, cleaning and deacidifying the water around it. As it does this it takes up minerals and nutrients from the surrounding water, whether this is in the ocean or aquaculture farms. The seaweed then becomes dense in these essentials minerals and nutrients, making them available for use elsewhere.

Seaweed grows at a very rapid rate. In ideal conditions some species can grow as much as 60 cm in length in one day. Large quantities can be grown with minimal inputs and just like forests, seaweed captures and stores CO₂ as it grows. With such rapid growth rates and vast underutilised regions in which to grow, seaweed has great potential to help offset the excess carbon produced by human activity.

Professor Tim Flannery has been exploring seaweed’s potential and has come up with some very interesting findings from scientists and entrepreneurs from around the world.

Pacific Reef Fisheries, Ayr, North Queensland. Photo by MBD

Combating Climate Change

As Tim Flannery states in his book Sunlight and Seaweed: An Argument for How to Feed, Power and Clean Up The World (Text Publishing 2017):

‘The stupendous potential of seaweed farming as a tool to combat climate change was outlined in 2012 by the University of the South Pacific’s Dr Antoine De Ramon N’Yeurt and his team. Their analysis reveals that if nine per cent of the ocean were to be covered in seaweed farms, the farmed seaweed could produce 12 gigatonnes per year of biodigested methane which could be burned as a substitute for natural gas. This, they say:

‘…could produce sufficient biomethane to replace all of today’s needs in fossil-fuel energy, while removing 53 billion tonnes of CO₂ per year from the atmosphere… This amount of biomass could also increase sustainable fish production to potentially provide 200 kilograms per year, per person, for 10 billion people. Additional benefits are reduction in ocean acidification and increased ocean primary productivity and biodiversity.’

‘Nine per cent of the world’s oceans is not a small area,’ writes Flannery. ‘It is equivalent to about four and a half times the area of Australia. But even at smaller scales, kelp farming has the potential to substantially lower atmospheric CO₂, and this realisation has had an energising impact on the research and commercial development of sustainable aquaculture. But kelp farming is not solely about reducing CO₂. In fact, it is being driven, from a commercial perspective, by sustainable production of high-quality protein.’

‘If kelp farming is to reach its full potential, a model for mid-ocean farms is required,’ states Flannery, referring to the marine permaculture systems being designed by Dr Brian Von Hertzen of the Climate Foundation.

These mid-ocean ‘permaculture arrays’ will grow kelp at a large scale, creating a free-range aquaculture system based on providing habitat to keep fish on location. Cool nutrient rich water will be pumped up over the kelp, from below.

Von Hertzen’s vision is to produce not only seaweed and fish for eating, but also feed stocks for animals, fertiliser and biofuels. The kelp could also be harvested and sunk in the deep ocean. ‘Once in the ocean depths, the carbon the kelp contains is essentially out of circulation and cannot return to the atmosphere,’ states Flannery.

‘Given the transformative effect that marine permaculture can have on the ocean, there is much reason for hope that permaculture arrays can play a major part in globally balancing carbon,’ writes Flannery, with these systems looking to be ready towards the end of this year.

This is but one possible solution in reducing our carbon levels, with Flannery exploring others as well. In an interview aired this year on the ABC’s Catalyst, Flannery spoke with Professor Rocky de Nys, a seaweed expert from James Cook University, about an experimental seafood farm in Queensland he is working on; Pacific Reef Fisheries. They use seaweed to feed the fish and clean the water.

The levels of wastewater produced by a fish farm this size would normally present an environmental hazard. But by running the water through a seaweed filtration system, the nutrients are channelled into the seaweed’s growth, which occurs at a phenomenal rate. Tripling in size each week, the seaweed takes nitrogen, phosphorous and carbon out of the system and broader environment, creating a useful by-product packed full of nutrients that can be used elsewhere.

Aside from the fish produced from this farm, the seaweed is used as a food source and also turned into biochar. This is used as an organic fertiliser on banana plantations, adding those nutrients to the soil and allowing them to be stored there, reducing the need for chemical fertilisers.

Flannery reports that seaweed is also beginning to be developed for use in clothing and medical applications (such as artificial connective body tissues). He spoke with researchers at the University of Melbourne who are looking into its capabilities as a building product, making a hard brick-like substance that could potentially replace concrete and bricks. This would not only save on carbon that would otherwise be generated during concrete production, but actually sequester carbon from the atmosphere into our buildings.

Collecting sea-weed for making seaweed fertiliser. Photo by The Horticult

Garden Additive

Even for those not focused on saving the world, seaweed can also play an important role in our own health and wellbeing.

Adding seaweed to your garden introduces a range of minerals and trace elements from the ocean that aren’t always readily available in the soil. Seaweed accumulates these elements from the ocean and makes them available to our plants, which in turn makes them available to us. Generally speaking, Australian soils are lacking in zinc and iodine, which seaweed is high in.

Seaweed supplements increase the health of your plants, making them more resistant to pests and diseases. They increase frost tolerance, stimulate root growth and add a range of nutrients, minerals and trace elements. They also boost microbial life in the soil.

There are several ways to make seaweed available to your plants. You can collect it yourself and add it to your garden as a mulch, put it into your compost or use it as a liquid fertiliser. You can make your own liquid fertiliser, or there are a wide variety of commercially produced liquid concentrates available.

If you are collecting seaweeds yourself, keep in mind that they can also take up dangerous metals and toxins that exist in polluted areas. Be careful where you collect the seaweed from and avoid highly urbanised areas (refer to our Foraging Seaweed Sustainably article on page 46).

There are different state laws around how much seaweed you can collect. In NSW for instance, you can collect 20 kg a day from the beaches for personal use, excluding marine parks. For more information, check with your local fisheries department.

Seaweed As A Food Source

You may want to just ingest this green gold directly. Seaweed as a food source is increasing in popularity. In countries such as Japan and Korea, seaweed has been part of the diet for millennia, but in the Western world we have only been catching on in the last few decades. We’re all familiar with the seaweed wrapped around a nori roll, but seaweed comes in many forms and there are countless ways to include it into our diet.

In Australia, we are only just getting to know all the different types of seaweed available to us. Seaweed-based food production is a fledgling industry, where cutting-edge scientists and entrepreneurs are busy discovering and researching its many health benefits and applications.

According to Dr Pia Winberg, founder and CEO of Venus Shell Systems (a company creating seaweed products for commercial use), seaweed contains 40% protein and all of the essential amino acids, soluble and functional dietary fibre, omega-3 fats and B12, making it suitable for vegetarians. Jo Lane from Sea Health Products claims that sea kelp is actually the richest known source of natural iodine. There are a growing number of companies out there selling dried and ready-to-eat seaweed, so you can add it to your diet without the fuss of harvesting it yourself.

Thanks to the pioneering work of these innovative people, seaweed is proving to be a sustainable resource that may help to offset or replace many currently unsustainable practices. Research and use is still in its infancy, so watch this space. Seaweed may become the solution to many of the problems facing our planet today.

Make Your Own Seaweed Fertiliser

Gather beach strewn seaweed, preferably from a non-polluted area (checking local laws). Place directly in a large container and cover with water. Let sit for several weeks. If the container has a lid, it’ll help contain the somewhat putrid smell and stop mosquitos breeding in it. When the concoction is ready for use, dilute 1:10. Add it to your soil and plants once a week.

* Catalyst Show Series 18, Can Seaweed Save the World. Available on ABC iView until August 15 2020.


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