Raphael Thys
Seaweed Generation AlgaRay robot rendering — Seaweed Generation
“Here there be monsters” hasn’t appeared on nautical maps for centuries. Yet, there is a monster brewing in the Atlantic. This foul creature is strangling vast ecosystems, decimating corals, and even destroying human infrastructure. Every year it grows in strength, thanks to our wasteful industries feeding its insatiable appetite. I’m not talking about a Kraken, sirens, or even my uncle Barry on a Lilo. No, this scourge is far more real. I am, of course, referring to sargassum seaweed and its enormous blooms. Fortunately, there is hope amid the devastation, as Seaweed Generation plans to turn this oceanic apocalypse into a planet-saving carbon sink using adorably cute robots. So, how?
Sargassum is a type of floating seaweed. It looks like a bundle of tangled brown string with air sacs mixed in, and you have most likely seen it washed up on the shore during your summer holiday. Normally, limited nutrient resources keep it from overcrowding its native ecosystem, which extends from the Caribbean over to the west coast of Africa. But not anymore. Human activity, such as intensive soya farming in the Congo, the Amazon, and the Mississippi, floods the Atlantic with nitrogen and phosphorus, allowing the sargassum to spawn at an astonishing speed, causing vast blooms that stain the surface of the ocean golden brown.
In April of 2022, NASA used satellite data to measure the sargassum levels in the Atlantic and discovered the largest sargassum bloom ever, containing a whopping 4 million metric tons of the stuff!
So why is this bad?
Well, sargassum can stop light and oxygen from reaching the water levels beneath it, literally starving and choking the underlying ocean creatures. Its string-like texture also means some marine animals, like turtles, can get caught in it and drown, which clogs up our ocean-based infrastructure, damaging it beyond repair. Sargassum also contains some toxic compounds. After all, it evolved protection to avoid the average free-floating seaweed’s fate of being munched on, but this means it can literally poison the environment around it. And it doesn’t end there! When the sargassum washes ashore and dries out, it releases hydrogen sulphide and ammonia, which can cause severe headaches, nausea, vomiting, respiratory difficulty, and even vertigo in humans.
This means a bad sargassum bloom can severely impact ecosystems, the environment, and even the economies of nearby countries.
This is where Seaweed Generation comes in.
This, quite frankly, brilliant startup saw an opportunity in the chaos. You see, sargassum is rather good at capturing carbon from the atmosphere. As a surface-dwelling photosynthetic alga, it creates its sugary food and even builds its cells from the carbon in atmospheric carbon dioxide. This works out to around 1 tonne of atmospheric carbon captured for every 10 tonnes of sargassum.
However, this carbon would typically return to the atmosphere when the seaweed is eaten and digested or rots away at the surface.
Seaweed Generation knew this and devised an eloquent solution to manage sargassum levels and stop this captured carbon from reentering the atmosphere.
They plan on using a manta ray-shaped autonomous submarine robot called AlgaRay to glide along the surface, scooping up the sargassum much like the manta’s filter-fed plankton. Once their robot bellies are full, they will descend to a depth of 135 m (443 ft), belch up their robot meals, and then float back to the surface to repeat the process. At that depth, the water pressure is so great that sargassum’s air sacs are compressed, and it becomes negatively buoyant and sinks to the deep ocean. Down there, microbes and detritus-eaters digest it, turning it into the carbon-rich sediment that coats most of the ocean floor. This traps sargassum’s captured carbon away for at least a few hundred years, if not longer.
With a large fleet of AlgaRays, Seaweed Generation hopes to be able to stop these ocean disasters and, in the process, sequester millions of tonnes of carbon dioxide from the atmosphere. For example, the current four million tonne bloom could be cleaned away and, in the process, remove a massive 400,000 tonnes of atmospheric carbon dioxide!
Now, you have probably noticed that the largest sargassum bloom ever couldn’t meet Seaweed Generation’s targets. This is why, once AlgaRay has got sargassum blooms under control and back to natural levels, they plan on releasing a second robot called AlgaVator, which will actively cause sargassum blooms for AlgaRay to remove and so boost the levels of carbon sequestration.
All this sounds good in theory. But many are worried about the effects this will have on the deep ocean. Luckily, Seaweed Generation has thought of this. Mike Allen, their CSO, says, “We’ve spoken to a lot of scientists about this. The ones on our team, the ones on our Scientific Board, and many who are working on and thinking about the oceans, seaweed, carbon cycling, air sea flux and more. Our conclusion from these conversations is: we don’t know for sure. Some feel that naturally occurring biomass may stimulate deep ocean life, some worry it will impact it, often, this will depend on the amounts of additional biomass you’re talking about. Scientists studying the oceans often have wildly differing opinions. The reason for that is fairly simple — there isn’t a lot of data, especially about the deep ocean. That’s one thing that most scientists do agree on, we need more data. That’s an ongoing effort that we will contribute to in our 2023 pilot.”
It’s great to see that Seaweed Generation is working hand-in-hand with scientists and is proactively engaging in studies to assess the ecological impacts their technology will have before they work to scale it up. Even if the results show that AlgaRay is a no-go, we will have learned a hell of a lot more about the precious ocean ecosystems and therefore know how to protect them better.
But the chances are that at least a sensible level of carbon capture will be possible with sargassum blooms and AlgaRay. The deep ocean contains roughly 37 trillion tonnes of carbon, mainly in that thick muddy ooze carpeting the ocean floor. In comparison, the upper ocean only contains 900 billion tonnes, and the atmosphere only 875 billion tonnes. This means that if humanity’s total emissions from pre-industrial times were captured and stored down there, it would only increase the carbon levels by 2%. Now, that may still be significant, but it shows the scale that Seaweed Generation is looking at.
So that’s how a swarm of autonomous biomimicking robots could turn a climate disaster into a powerful carbon sink. There are still plenty of hurdles in the way for this technology to come to fruition. For example, environmental studies could kneecap this idea, and the development and production of enough AlgaRays to make a difference might become too much of a challenge. So this likely won’t be the climate silver bullet we are looking for, but it seems set to make a significant difference in our efforts to save this beautiful planet that we call home.
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