COASTAL WATERS could feed the world – 6 minute summary video
If you’re rushed for time, just watch this 6 minute video
Podcast version for long form storytelling:- Freakanomics interviewed Bren Smith 43 minutes – June 2021. Spotify’s “How to save a planet” is even longer. Part 1 and Part 2
No inputs, just cheap equipment
Coastal seaweed and shellfish are sustainable foods. They use no arable land, no fertiliser, and no fresh water – and no energy to mine or manufacture or pump all these around. Indeed, oceans around agricultural zones are often suffocated in fertilisers. Excess nutrients wash off the farms and suffocate many coastal waters – causing dead zones. The seaweed and shellfish love these nutrients and gobble them up. They clean the water as they grow.
All it requires is a boat (which does not have to go out very far at all), and some buoys, ropes, and cages. The start up costs are low and Bren Smith has made the plans open-source at Greenwave.
A yield 2.5 to 7.5 times higher than wheat or legumes!
Bren Smith claims an area of Washington State, or 71,000 square miles / 185,000 kilometres square could feed the world. That’s all the nutritious omega 3 seaweed powder food-additive and delicious shellfish we could eat. Remember that kelp grows 30 times faster than land plants – up to a foot a day. This yields 30 tons of wet kelp per acre, but that’s a lot of water weight.
A great deal can be grown in a short time: annual yields average 19.4 metric tonnes of dry weight per hectare. By comparison, about 11 metric tonnes of maize can be harvested per hectare in the highly productive fields of the United States. Gro-Intelligence September 2016
About half of that is protein – but it’s hard to extract and concentrate with variation according to each species.
The protein yield in tons per hectare per year (ton/ha/yr) for macroalgae is in the range of 2.5–7.5. This value is two to five times higher than that of wheat or legumes. In addition, they can be harvested throughout the year and may be cultivated and some species of macroalgae contain all the essential amino acids required for human nutrition. National Library of Medicine – 2005
Used as a fertiliser
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.
Feeds fish, fixes acidity, creates habitat, and 20% breaks off and sequesters carbon at the bottom of the ocean!
Those reasons are myriad. For one, it’s a zero-input crop that is grown underwater, so there’s no carbon footprint outside of distribution. “It also sequesters carbon dioxide at a much faster rate than land agriculture,” says Bettinson. “Additionally, as it’s growing, it’s constantly shedding bits of itself into the ocean. And 20 percent of the total growth of sea vegetables — and kelp in particular — gets left in the ocean for long-term carbon sequestration.” That absorption of C02, Bettinson notes, is doubly useful, as it helps to locally de-acidify water systems — a necessity for the health of coral reefs, shellfish and many other elements of the ocean ecosystems. Johnson and Wales University – October 2022
So many uses as food – but the main challenge is marketing it!
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. But this is not the real issue.
Eating seaweed has only made it into very niche sushi and boutique restaurants that serve up exotic seaweed salads. There are a few niche products – like seaweed beers and pickles. Yet this is challenging, as the moment it leaves the water they only have 12 hours before it goes limp and degrades. So – the majority of seaweed that we eat will probably be invisible to us much like soy beans are in everything and we hardly know it. Seaweed is dried and powdered and turned into a sort of flour. Then it can become a supplement for everything from veggie-beef burger patties through to protein bars. It’s also used for plastics and paper and cosmetics and even some chemistry for concrete! Most market analysts I quickly googled then (Sept 2023) predict seaweed demand will double or triple by 2030. That’s encouraging – but not fast enough!
A plea to activists
If you are interested in this field please write to the big food companies in your state and ask them if they have considered the role of sustainable seaweed in their foods? (EG: Pressure is growing on McDonald’s to include an alt-meat seaweed burger.) Or if you know big farming groups – write to them about using seaweed as a fertiliser. Google about the different types of seaweed and what they can do – and see if it inspires you to action. Read The Regeneration action items. The very idea that we can get so much food while restoring the ocean is exciting.
Or if you’re looking for a whole new career change – to join the coastal kelp farm movement or even work in the field, see Greenwave.org
The OPEN OCEAN – enormous potential but expensive at this stage
Tim Flannery TED talk: using solar powered barges to pump nutrient rich water up to adapt this system for the deep ocean with enormous claims, but they had no idea of the costs back during this TED talk. Unfortunately the costings are in and I explore them below. Until something fundamental changes in the design and approach, we will not be doing some of the more extreme build outs Tim discusses, such as using 9% of the oceans just to sequester all our carbon. It will simply cost too much. But the good news is if our coastal zones become too crowded with the standard seaweed farms above – this is another option for premium market sectors.
This is away from coastal erosion and up-welling areas that fertilise about 5% of the oceans – now we’re thinking about the other 95% that is nutrient starved and deep. (See the map near the end of this paper to see how comparatively small the nutrient rich regions are – yet they are big enough to feed the human race!)
Out in the open ocean there are nutrients, but they are trapped hundreds of metres down under the warm water (called the thermocline). Indeed that layer is getting worse. Larger fish and whales once swam up and down through the water layers so much they would mix them, bringing food up for phytoplankton. But we have so over-fished them this has actually decreased. Climate change has also made the surface waters warmer, which makes them float more – solidifying the layer below. We can fix this!
Solar powered barges can pump those nutrients up to the shellfish and seaweed!
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.
But the open-ocean farms seem too expensive to replace jet fuel – let alone sequester all our carbon as hoped in the TED talk above
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? 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 alone 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 work on geoengineering sized farms. Apparently 9% of the world’s oceans would sequester all our annual CO2 emissions! (N’Yeurt.)
But 9% is 18 times larger than the 0.5% of the world’s oceans we costed above – which would be 342 times the world’s GDP!
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.
Eclipse Now 
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