Seaweed to save the world!

Either read the page below or just kick back and watch the first 2 TED talks by Bren Smith and Dr Tim Flannery

Bren Smith TED talk from December 2013 – it remains a classic introduction to the coastal seaweed and shellfish farming system which is gradually growing and spreading. It could feed a world of 10 billion all the protein and nutrient rich food we need.

Tim Flannery TED talk: 17 minutes – takes the concepts above out into the open ocean. (But note – engineers have now found it is too expensive to replace oil or jet fuel, or geoengineer away ALL our carbon emissions. We should be grateful it’s another way to feed the world while restoring some oceans!)

On this page:-

  1. Coastal kelp farms could feed the world while repairing the oceans!
  2. Open oceans are starving to death
  3. Solar powered barges let us repeat this trick out in deep water
  4. Too expensive to replace jet fuel or geoengineer away ALL our carbon emissions.
  5. But feeding the human race and restoring some oceans are worth it
  6. Ocean Conservation – groups that help save what is left

1: Coastal kelp farms could feed the world while repairing the oceans!

The claim is that kelp seaweed and shellfish farms could feed 10 billion people! Both the shellfish and the seaweed are great sources of protein – and the seaweed can be dried and powdered and put into almost everything (like soy beans are in many vegan-burgers and dairy alternatives).

Agriculture on land requires huge amounts of energy to make fertilisers and pump huge volumes of fresh water – these kelp farms don’t need any of that. They get everything they need from the sun and nutrient rich coastal waters.

Instead of just growing seaweed – these farms are called “3d seaweed farms” in that they hang seaweed lines and shellfish cages from buoys. See the illustration below.

Indeed, as the graph below shows, many of our coastal areas are actually over-fertilised with agricultural and sewage nutrients. Over fertilisation grows the wrong algal blooms and causes dead zones. Fortunately, seaweed and shellfish farms would gobble up these excessive nutrients and could convert them into food. This is different to aquaculture which tries to grow fish in captivity in big pens in the ocean or on land (often relying on ocean-destroying ‘by-catch’ to feed their captive fish). Instead seaweed and shellfish farms can help clean up the mess!

As the map from Inlet Keeper shows:-

Bren Smith claims an area of Washington State, or 71,000 square miles (or 185,000 km2) could feed the world. That’s all the nutritious omega 3 seaweed and shellfish we could eat, restoring the health of our coastlines and stimulating the local ocean ecosystems.

Seaweed can be used as a fertiliser – bringing some of the NPK fertilisers that wash out to sea back on the land. Bren develops relationships with local farmers to bring high quality seaweed onto land as fertiliser. That’s a sustainable cycle, as normal erosion drags nutrients off the coasts and seaweed farms bring them back.

While 3d seaweed and shellfish farms have expanded around the UK, legislative opposition and NIMBY groups have slowed expansion in the USA as Scott Lindell explains in his 2020 TED update.

2: The open oceans are starving to death

Now we move out from the narrow band of coastal ocean that is nutrient rich. Further out it’s a nutrient desert where kelp would starve to death. There are nutrients, but they are trapped down under the warm water (called the thermocline), and they’re hard to get to. Especially since we’ve overfished the larger fish species and of course the whales, eliminating the larger creatures that used to swim up and down the water column, turning the water over.

3. Solar powered barges let us repeat this trick out in deep water

The answer to growing kelp out in the nutrient poor majority of the oceans is to build barges with solar-powered pumps. They run hoses that pump the deeper nutrients up around the barge. We can use these to grow kelp in almost any ocean we want to! They can scale up simple seaweed and shellfish farming to any scale we need – and help restore the oceans as we do so!

This floating seaweed farm runs on wave-power to get those nutrients.
3 minutes.

Tim Flannery explains more about MPA’s

Von Herzen’s objective is to create what he calls “permaculture arrays” – marine permaculture at a scale that will have an impact on the climate by growing kelp and bringing cooler ocean water to the surface. His vision also entails providing habitat for fish, generating food, feedstocks for animals, fertiliser and biofuels. He also hopes to help exploited fish populations rebound and to create jobs. “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,” he says.

The addition of a floating platform supporting solar panels, facilities such as accommodation (if the farms are not fully automated), refrigeration and processing equipment tethered to the floating framework would enhance the efficiency and viability of the permaculture arrays, as well as a dock for ships carrying produce to market.

4: Too expensive to replace jet fuel or geoengineer away ALL our carbon emissions.

It hurts to write this. For years I’ve raved about seaweed as a possible cure-all for climate change – aware that there is no technical reason we cannot expand these floating seaweed farms over vast areas of the ocean. I mean, if just 0.5% of our oceans could produce all the airline fuel and diesel that the world needs – without logging forests or competing for farmland – you can see why it’s so attractive!

But there’s a problem. It’s expensive! It will only ever work out economical with the highest value food and pharmaceutical products. For example, the oceans are vast – in fact they are a huge 361 million square km in area.

Which means that little 0.5% of the oceans is actually 1.8 million km square!

Brian Von Herzen says his floating seaweed farms are going to be $3 million at the start, but with volume should come down to $1 million per hectare. How much is that to replace jet fuel and diesel – our 0.5% of the oceans?

Well, there are 100 hectares in 1 km square.

Therefore 1 km square is $100 million.

Multiply that by 1.8 million km square, and the capital cost is an insane $1,800 trillion! The entire world’s GDP is only $96 trillion a year. That’s close to 19 years of the entire world’s GDP. For just 0.5% of the ocean!

In the past – before engineers had costed the floating seaweed farms – scientists did back of the envelope claims we could farm 9% of the world’s oceans to sequester all our annual CO2 emissions! (N’Yeurt.) This is using the oceans for geoengineering. But 9% is 18 times larger than the 0.5% of the world’s oceans, so would actually be 342 times the world’s GDP! 342 years to pay off a 9% seaweed farm. (19 years GDP at 0.5% oceans multiplied by 18 times larger.)

It just ain’t gonna happen – (not unless a revolution in AI allows a Robot Economy to break out – in which case we’re in a Post-Scarcity economy and none of these concerns will matter any more anyway!)

5. But feeding the human race and restoring some oceans are worth it

To join the coastal kelp farm movement or even work in the field, see

For more information on open ocean floating farms, see Ocean Visions who also have a discussion forum for questions.

6: Ocean Conservation – creating enormous marine parks and no-fishing zones

While we are talking about how the ocean can save us let’s also talk about how we can save the oceans. These conservation groups work to create marine parks and save threatened reefs and fisheries and protect the oceans from pollution.


Conservation International have a beautiful page dedicated to the oceans.