Sargablock: Bricks from Seaweed | Hacker News Reader

Sargablock: Bricks from Seaweed

fortomorrow.org

168 pointsthunderbong63 comments

I watched something on YT recently about this. I think it was https://youtu.be/2fXiboAGQvM (8m 12s, "How Bricks Made From Invasive Seaweed Clean Mexico's Beaches | World Wide Waste | Insider Business")

It shows a bit of the process if you're curious.

The guy seems to have a big heart, and (naively) appears to be turning a stinky problem into a win-win-win.

naively?

I lack both the firsthand experience and research background to understand if there are ~obvious reasons (to people with domain knowledge) that this isn't actually a win-win-win.

Oooooh I thought you were implying "the guy" was naive. Thanks for clearing that up.

Fair :)

I also had the same impression. Only commenting to add another data point and point out it might be worth rewording if you're not outside the edit window :)

Long past, unfortunately.

In short: sargassum seaweed is washed onto shores anyway, why not use it to make bricks? They form the bricks using a standard block-making machine, dry them at the sun, build small houses out of these, and plan to donate these houses to local families in need.

They say that they use 40% of seaweed in the bricks, and 60% is "other organic material". I wonder what material is this.

I also wonder how well the sargassum bricks withstand weather.

> 60% is "other organic material". I wonder what material is this.

IIRC from the YT video in my top-level comment, it's dirt.

> I also wonder how well the sargassum bricks withstand weather.

dopa42365's comment (https://news.ycombinator.com/item?id=37176903) links a paper with the following claim:

> Studies carried out by the Secretariat of Ecology and Environment of Quintana Roo state, Mexico, found that the resistance of the bricks is 75–120 kgf/cm2, while its durability can be up to 120 years, regardless of the region or climate type where they are used (Desrochers et al., 2020). Currently there is no other sustainable material as resistant, or with such a long useful life. Sargabricks are therefore seen as a viable and safe material for the creation of ecofriendly buildings.

(edit: But the OP link also contains this 120y assertion. I haven't checked the paper's citations, so I'm not sure if everyone's depending on the cited study's analysis, or if that study is laundering claims by the people making the bricks)

> I also wonder how well the sargassum bricks withstand weather.

In the video they mention the first house built using these bricks was in 2018. It's still standing and looks like it's in good condition. They also mention the homes they build with these bricks are strong enough to withstand hurricanes.

Worth noting that these characteristics generally hold for most cob bricks as well. It doesn't seem like it's particularly special because of the seaweed except that it's a way to use an abundant resource. Significant imo because of the minimal treatment necessary and lack of ecological harm in construction.

Wanna renovate? Wanna expand your building? Wanna take it apart and rebuild it entirely? It's basically just dirt so it's flexible to future growth and needs with minimal costs. The West tends to build buildings as if they're permanent but of course even skyscrapers need to come down eventually. All that glass, plastic, and even stuff like asbestos previously, is eventually gonna be taken apart. Usually mostly dumped to a landfill

Round homes without sharp corners fare better than rectangular homes in hurricanes probably because the wind shearing force is lower. Deltec Homes sells round, radial homes: https://www.google.com/search?q=deltec+youtube+hurricane

Hempcrete on structural forms like LEGOs another type of CEB Compressed Earth Block: https://en.wikipedia.org/wiki/Compressed_earth_block

Radial blocks make turning corners with various radii easier; so that the wind doesn't grab the ~K'Nex cube of the structure and shear it under the roof and around the stairs.

I wonder what material is this.

Maybe old fishing nets and random plastic trash, considering its all recovered from beaches? Heh. Nah, perhaps hay/grass? Not sure what acts as a binding agent, either.

Incorporating old, strong plastic filaments would be a terrific reuse idea.

I don't think the get enough disused fishing nets for that, and these nets would need a lot of cutting.

I helped with a study of the compression strength of concrete blocks when I was in high school. It was a long time ago, but IIRC, the blocks augmented with monofilament (it was fishing line) performed well.

> and 60% is "other organic material". I wonder what material is this.

I'm guessing some binding agent like clay?

Clay is inorganic, it's a mineral

They're not kiln-fired, are they?

It feels like they're just making adobe with seaweed instead of straw.

Sure, but why not?

The linked article says they are dried in the sun for four hours.

Yeah, that's distinctly different from kiln firing. Various clays take on significantly different physical characteristics depending on heat treatment.

It is possible to build a solar powered kiln, but "dried in the sun" is a different process than what clay goes through- which makes sense, since organic matter and dirt wouldn't benefit from a kiln anyway.

That's how it was described as in a video about it too.

> sargassum seaweed is washed onto shores anyway, why not use it to make bricks?

I mean the obvious question is whether that is a safe construction practice

What kind of safety are you thinking of?

What I'm wondering is: are there other impacts from removing the seaweed from the shores; does it change the ecosystem around the shore in undesirable ways?

Also: is the supply really up for the demand?

Will the house collapse is what I’m wondering

Why would they make bricks out of seaweed if they thought the house would collapse?

Why would someone build an MVP for a product that has no clear or viable path to monetization? Because someone wants the product to exist enough that they're willing to give you money to make it happen.

Because someone will buy it. Hence regulations.

But that’s the question. The question is has it been tested to be surely safe.

The Bible describes Egyptians making bricks from mud and straw. In europe and the US it's referred to as "cobb" which if you plug that word in to youtube is a deep rabbit hole of building sturdy and sustainable homes for cheap, even today. You need thicker walls (about triple) than what you might see in a lightweight modern home made by 2x4s and drywall, but the lower cost of materials (and much lower cost of labor) offsets this. The incredible thermal mass of the walls also helps to regulate internal temperature during the daytime. But to answer your question, typically no they do not collapse unless the roof goes without any maintenance, which is unlikely in a tropical region.

Well they do say the seaweed is invasive, so removing it seems like it would actually be plus for the beach ecosystem (unless it's replacing some native seaweed that no longer washes up, I suppose).

The seaweed is removed anyway; resorts and beach authorities remove it because it makes for an unpleasant beach.

Create it into a slurry and extrude it though an oven and use material for all commercial and civic projects... make curbs or asphalt alternatives from this.

In the 50s, my grandparents were making bricks from hay and mud. You’d be surprised, the houses are still standing. Very eco-friendly, should make a startup selling this.

They can even call it something catchy, like "mudbrick™".

Straw and mud is cob. That's how houses were made in the UK (for example) for quite some time. It is a bit more modern than wattle and daub.

An aunt and uncle of mine owned a house in a village in Devon for a decade or so with 1660 scratched rather neatly near the front door. That cottage is quite old but no where near the oldest cob and thatch building hereabouts. Horse piss or any piss (nitrogenous waste) is also used, presumably with another admixture. I'm not a cob expert but I did study Civ Eng and graduated.

You pop a lime wash on it for water proofing, without sealing it completely - it needs to breathe - ie avoid rot and decay. When it eventually breaks down, you cut out the bad bits and replace with more of the same.

Not sure about making bricks of the stuff - that might introduce potential fault lines but that might not be an issue and may even allow the structure to flex more in response to say earthquakes or weather.

(EDIT: hay -> straw)

Sargassum is a disaster for the economy of caribbean countries because many rely on tourism (read white sand beaches), so it may be a good idea to take advantage of it, but how can we be sure that enough sargassum will wash up on the shore for the next 6 months ? Wether we view sargassum as a disaster or sargassum as a raw material, the problem is that we can't control its flow.

In that case it's probably smart he's doing this as a non-profit rather than a business. A business might go under if the sargassum stops, a non-profit can just wait or just go to other localities where they are getting sargassum and help them build homes there instead.

A non-profit is still...a business...its just a non-profit business. I don't think being non-profit exempts a business from staying alive without funding, wherever that comes from. I'm not saying your last point isn't valid though.

cached version - https://webcache.googleusercontent.com/search?q=cache:BvdFhn...

The link seems to be Slashdotted into oblivion.

Here's an article in the Mexico News Daily explaining it:

https://mexiconewsdaily.com/news/mr-sargassum-built-13-house...

From the article https://fortomorrow.org/explore-solutions/sargablock ::

> I adjusted a machine designed to make adobe bricks so that it can process a mix of 40% sargassum and 60% other organic materials for the Sargablock. The machine can turn out 1,000 blocks a day, and after four hours of baking in the sun, they are dried and ready to be used

https://www.frontiersin.org/articles/10.3389/fmars.2021.7684...

> Studies carried out by the Secretariat of Ecology and Environment of Quintana Roo state, Mexico, found that the resistance of the bricks is 75–120 kgf/cm2

That's far below concrete, isn't it?

Yeah I'm thinking, one 5-point earthquake and this falls apart? I mean it's better than mud bricks, but...

I'm not an expert, but I'd be surprised if concrete is at all earthquake resistant without rebar.

Ancient Romans didn't use rebar in their concrete but they did use aggregate of different densities depending on what section of the building would be under stress. Plus if cracks form their concrete self heals due to the compounds used in it.

How many earthquakes did ancient rome suffer?

Quite a few through the centuries, with the moderate to large quakes originated from the Apennine mountains’ Mount Vettore fault about 80KM away from the city.

https://www.researchgate.net/publication/236950808_Beyond_th...

https://blogs.agu.org/geospace/2019/03/04/seemingly-dormant-...

You should be able to reinforce this while building, just like with other masonry.

Additionaly, if the structures are fairly small, and the walls are properly tied together, that may be enough.

Concrete isn't known for being very earthquake resistant. If you're building for that wood is a much better choice

The primary link doesn't explain the other 60% of the formulation, but IIRC (from watching the video linked in my top-level comment) the other component is waste dirt from construction projects.

I'd expect it to be less strong than concrete, so I guess more fair comparisons might be mud bricks, other mud-brick + X formulations, and traditional clay bricks?

edit: but worth noting that the paper you linked does mention that someone else is making "sargacreto" that is 40% sargassum and 60% concrete, though it says there aren't numbers to cite for its strength yet.

Wouldn't the proper comparison be other bricks?

Yep, and well below titanium as well. So, if you've got a beach where a bunch of titanium washes up every year, my advice is to use that instead.

whats the compressive strength of sand?

could just use that.

- First-class brick has a compressive strength of 105 kg/cm².

- The compressive strength of a second-rate brick is 70 kg/cm².

- Common building bricks have a compressive strength of 35 kg/cm²

- The compressive strength of sun-dried brick is between 15 and 25 kg/cm².

Source: https://housing.com/news/compressive-strength-of-bricks-mean...

"Concrete" is a composite material that can vary wildly depending on composition and process. These tests on grade M10 concrete for example concluded with 136, 131, and 147 kg/cm2 for their 3 samples. For plain cement, generally grade M15 is used[1] which is about 153 kg/cm2

[0] https://civilplanets.com/compressive-strength-of-concrete/

[1] https://theconstructor.org/concrete/grades-concrete-strength...

I guess this solution would also be carbon negative due to the locked carbon in the organic material.

As long as the bricks aren't fired, but that looks like it's the case.

That said, I'm sure the carbon will be released again if the bricks are broken and wetted. Best thing is to bury it somewhere dry I suppose.

Ah, and indeed it will eventually be released.

I'm aware of hemp solutions locally that are marketed as carbon negative locally to me

https://www.indinature.co/uk/products

When you make a brick from the Sargassum, does it release or hold onto the CO2?

If it's dried, it should hold onto the CO2. Of course, if the brick is broken, weathered and wettened it'll probably release it again, plus if it's fired that process will emit more CO2 than it sequesters.

I don't think it's a carbon sink, but more like a way to make something useful (that isn't compost) out of something unwanted. Note that the people collecting it also get paid by the seaside hotels to do so.

Don't they mould?

Yes, but only on prolonged contact with moisture.

Same with wood.

Like any adobe-style brick, they need to be protected from moisture.

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