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76 Seaweed and Carbon Sequestration | #worldorganicnews 2017 08 07




How farming giant seaweed can feed fish and fix the climate

Sunlight and Seaweed: An Argument for How to Feed, Power and Clean Up the World


This is the World Organic News for the week ending 7th of August 2017.

Jon Moore reporting!

This week we are focussing upon a piece entitled: How farming giant seaweed can feed fish and fix the climate from the blog Kevin's Walk on the Wild Side. This covers a new book by Tim Flannery: Sunlight and Seaweed: An Argument for How to Feed, Power and Clean Up the World. Links in the show notes.

In the past, I’ve been surprised at some of Flannery’s statements. A while back he was surprised at how quickly solar rooftop panels had taken off in Australia. After all, he’s projected 2030 or thereabouts for the level of usage we achieved by 2015. Little did he realise that price signals, rising power bills and increasingly cheaper solar panels, would drive the uptake of this technology.

In this book young Flannery seems to have cottoned onto the possibilities of price signals combined with science. The sort of thing which created the Industrial Revolution and should reverse its unpleasant side effects, just in time, we all hope.

So to the article.

Kelp, a form of seaweed much less studied than it should be. You will recall the huge drop off in cattle methane production when fed seaweed as part of their diet from a few shows back. The phenomena discussed on this occasion continues the greenhouse gas abatement line.



The kelp draw in so much carbon dioxide that they help de-acidify the water, providing an ideal environment for shell growth. The CO₂ is taken out of the water in much the same way that a land plant takes CO₂ out of the air. But because CO₂ has an acidifying effect on seawater, as the kelp absorb the CO₂ the water becomes less acid. And the kelp itself has some value as a feedstock in agriculture and various industrial purposes.

End Quote.


The kelp then becomes part of the solution to our current situation. But it is a supercharged part of that solution. The startup problems are enormous and subject to the vagaries of weather. The example cited in the article and the book is that of an enterprise off the coast of New Haven, Connecticut. Beginning in 2011 the kelp farmer, Bren Smith, was wiped out by storms, twice, Hurricanes Irene and Sandy. His enterprise 3D Ocean Farming is now profitable and ecologically stable.

Because once a critical mass is achieved, kelp forests will survive these storms. They are have further useful effects as the Chinese have been aware for centuries.



The general concepts embodied by 3D Ocean Farming have long been practised in China, where over 500 square kilometres of seaweed farms exist in the Yellow Sea. The seaweed farms buffer the ocean’s growing acidity and provide ideal conditions for the cultivation of a variety of shellfish. Despite the huge expansion in aquaculture, and the experiences gained in the United States and China of integrating kelp into sustainable marine farms, this farming methodology is still at an early stage of development.

End Quote


There are other advantages to ocean cropping beyond those already discussed is the relative speed of growth. Seaweed grows like bamboo in the wet w=season and every season is the wet season for seaweed. Growth rates 30 times those of land based agriculture are common. This provides many opportunities. As trees remove carbon dioxide from the atmosphere to create timber so the growth rates of seaweeds suck much more carbon dioxide from the oceans than do trees from the atmosphere. As the oceans are huge carbon sinks, absorbing carbon as a buffer to excessive atmospheric carbon, they are also somewhat supercharged to feed seaweed. One of the consequences of ocean carbon absorption is the acidification of oceans. This in turn leads to shellfish suffering thinning shells and weakening of already threatened coral reefs.

The benefits keep piling up.

And there has been academic work on the potential of kelp farming for biomass production of methane at the University of the South Pacific way back in 2012.



…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.

End Quote


They further calculated that 9% of the ocean surface area would need to be converted to kelp farms. This is not inconsiderable area but a smaller area combined with terrestrial regenerative agriculture could still achieve useful results.

Dr Brian von Hertzen has gone as far as to design kilometre square arrays for creating oceanic permaculture structures:



...a frame structure, most likely composed of a carbon polymer, up to a square kilometre in extent and sunk far enough below the surface (about 25 metres) to avoid being a shipping hazard. Planted with kelp, the frame would be interspersed with containers for shellfish and other kinds of fish as well. There would be no netting, but a kind of free-range aquaculture based on providing habitat to keep fish on location. Robotic removal of encrusting organisms would probably also be part of the facility. The marine permaculture would be designed to clip the bottom of the waves during heavy seas. Below it, a pipe reaching down to 200–500 metres would bring cool, nutrient-rich water to the frame, where it would be reticulated over the growing kelp.

End Quote


The possibilities this technology provides are only limited by our imaginations. The key is to avoid a monoculture of kelp which, in the wilds of the ocean, would be even more difficult to achieve than it is on land. Remembering that terrestrial monocultures are created with the use of herbicides, pesticides and artificial fertiliser, it seems financially prohibitive to grow anything other than a polyculture in the ocean. Win/win! I recommend you read both the article quoted from and Flannery’s monograph. There is hope in this time. The forces which created the industrial pollution, the rising levels of carbon dioxide, the possible release of methane from the tundra and rising sea levels will fight to maintain their entrenched positions of privilege within the economy but the alternatives are developing and developing in such a cost effective manner that price signals will overwhelm the rent seeking trenches being held by the remnants of the old order.

There is indeed nothing more powerful than idea whose time has come.

And on that happy note we will end this week’s episode.

If you’ve liked what you heard, please tell everyone you know any way you can! I’d also really appreciate a review on iTunes. This may or may not help others to find us but it gives this podcaster an enormous thrill! Thanks in advance!

Any suggestions, feedback or criticisms of the podcast or blog are most welcome. email me at

Thank you for listening and I'll be back in a week.





How farming giant seaweed can feed fish and fix the climate


Sunlight and Seaweed: An Argument for How to Feed, Power and Clean Up the World

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