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Comment by sverhagen | Hacker News Reader

Anyone can comment on this? Just reading this article, and not bothered by any relevant knowledge here, I'm scared that they're turning "harmless" wood into some sort of super product that is hard to break down later for recycling? Like how we did a nice job switching from Styrofoam to paper cups, except they now have a plastic liner that makes the paper hard or impossible to recycle? Or how I wonder what the city recycling is going to do with those "wooden" kitchen cabinets that I dropped off, that are completely covered in a plastic finish?

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Cross Laminated Timber (CLT), which I assume this is closely related to, is being used in construction more often now. It's much lighter and stronger than steel, easier to work with, holds up well in a fire because it doesn't go soft and loses structural integrity like steel does. And while wood of course can be burned, the char layer that forms on the outside protects the inside so it actually has some safety properties that buy people time when there is a fire. Also, wood is an excellent insulator.

Laminated timber is also very construction-friendly. It can be worked with simple tools, and CNC machines allow for prefab components to be shipped to the site and assembled quickly with minimal fuss.

There are some plans for high rise construction with this material. E.g. there is a plan for a skyscraper in Tokyo (350 meters, 70 floors).

The adhesives used in laminated timber aren’t perfect. They’re very durable, which is great for structural integrity. But it also means the material breaks down more slowly in a landfill (if you decide not to recycle the material for some reason). However, newer adhesives used for this these days are less toxic and not that harmful in a landfill. And importantly, most of the material is actually just wood, not glue.

(I know nothing about this)

Is it possible to make smaller scale CLT, with thinner boards or something, and build like cars or airplanes out of it?

Early cars and planes were made out of wood. So, I see no reason why not. The mosquitto which was one of the most successful planes in WW II was made out of plywood, which you could think of as an early form of CLT.

A lot of modern cars are made with a lot of composite materials that probably have better properties. But I imagine CLT could work well for things that are currently made out of steel or aluminium on such cars. I'm not sure if there's a big advantage to doing that in terms of strength, weight, or durability though. Aluminium might be lighter. And composite materials provide better strength and weight.

CLT is in no way similar to the product InventWood is working on, besides that it uses the same base material, and I guess requiring some pressing. You can think of CLT as being like plywood, but for beams instead of for sheets.

That said, CLT has 2 major advantages over regular wood:

1. It is more dimensionally stable, it expands/contracts less and in a more uniform way.

2. It is cheaper at larger dimensions. I.e. 0.5m x 0.5m x 20m wooden beams would take decades to grow and even then not realiably, but you can just manufacture CLT beams with those dimensions easily out of <10yr old trees.

Those two advantages are not limiting factors for the construction of cars or airplanes, so CLT is not super relevant to them.

Dimensional stability isn't irrelevant to planes. Thermal cycling is inevitable when going from the ground to cruising altitude and back.

Certainly would be better to laminate IF you're using wood. But it's still got a long road ahead.

Aluminum still has a higher strength/weight ratio which is everything in aero. Also, I'm not finding any information on cyclic strain behavior. Dimensional stability is only part of that.

Edit: There could be room for this in experimental aircraft. Once we tease out all the failure modes and properly characterize cyclic behaviorof course.

RIGA chair factory tour >> https://youtu.be/IndP2IKXTP0

Make CLT from thin enough boards and you got plywood

Aircraft grade plywood is still a thing. Often used for model aircraft, but you can make small planes from it.

If you follow the link from the article [1], then there's an abstract that describes the process. It sounds like they boil the wood with sodium hydroxide and sodium sulphite, then heat and compress the wood, which somehow leads to better alignment (and/or linking?) of the cellulose polymers.

I don't know what the implications are for recyclability, but there's no mention of injecting other materials so perhaps it decomposes in a similar way to ordinary wood?

[1] https://www.nature.com/articles/nature25476

The pressure treated wood used for railway lines is already damned near impossible to get rid of.

My understanding is that wood isn’t only pressure treated, but also soaked in chemicals that bugs and decomposers don’t like to eat.

Your fence probably has chemicals like that too.

then the carbon trapped in that wood is staying there for much longer than it would otherwise

That's true, at least around here [Germany]. Plus the nasty stuff might leak into the environment over the decades, and it's a pain to dispose of.

IIUC, they replace them with plastics since the plastic is seemingly more ecologically friendly and easier to recycle.

Mind concrete sleepers are what's used these days. You'll find wood only in shunting or cargo yards. (Or museums. Or the US - see linked commen by LeonM).

Source: I randomly met someone involved with that project. A proper train enthusiast can probably elaborate here, but I think I remember the core idea correctly. Also this obviously doesn't necessarily hold globally, though I can imagine many track operators face similar challenges.

Edit: While I wrote the above, LeonM wrote a nice reply on a sibling comment - https://news.ycombinator.com/item?id=44028161

I think pressure treated implies chemical impregnation--the pressure is used to diffuse the preservative through the wood.

Depends a bit on the country and era of the sleepers ('ties' in US), but traditional wooden sleepers are treated with creosote [0], which is tar/oil impregnation.

I'm no expert on this subject by any means, but I happen to volunteer at a museum where we have steam trains running. We build our tracks to look traditional, so we use wooden sleepers and no ballast. Most of our sleepers are donated from the commercial railroad companies, typically they are old stock but we also receive used ones occasionally. In my part of the world wooden sleepers aren't common anymore, so it's getting harder to find usable ones. This is a concern for us, as apaearantly there aren't any suppliers left in our part of the world for new ones. At our museum they typically last for about 15 years, mainly because we place our sleepers directly on the soil (no balast). The tar/oils will eventually dry out and the wood will just rot/decompose naturally. Wooden sleepers are considered chemical waste in my part of the world, though I do believe we are allowed to let them decompose fully as biomatter, which goes quite quick if in contact with moist soil. Though we typically dispose our used sleepers at a specialized waste facility, I'm not sure how they process it there.

Oh, and in case you are wondering: no, they don't burn, so we can't use them as firewoord for our steam engines ;-)

Appearantly in the USA, at least as of 2008, around 90% of all track was still using wood [1]. I didn't expect that. For most of the world we have used concrete sleepers for a long time already. Plastic sleepers are also common nowadays, which are typically made from recycled materials.

[0] https://en.wikipedia.org/wiki/Creosote [1] https://en.wikipedia.org/wiki/Railroad_tie

> Appearantly in the USA, at least as of 2008, around 90% of all track was still using wood [1]. I didn't expect that. For most of the world we have used concrete sleepers for a long time already. Plastic sleepers are also common nowadays, which are typically made from recycled materials.

This is for a few reasons, but the two primary ones are that wood is very cheap and plentiful in the US compared to most of the rest of the world, and we haven't banned creosote in the US like most of the rest of the world, so creosote treated wood is still the most common type of railroad tie.

You'd think that there'd be a robust secondary market for treated rot resistant timber that's "too rotten for trains, but perfect for landscaping". Sure, there's chemicals in it but if it's safe enough to be embedded in untold miles of rail bed then surely it's safe enough for comparable landscaping use.

Like everything else there's probably some 2nd/3rd order consequence of regulatory perversion that prevents it. Like because of the circumstances it wrongly gets classified as hazmat or something.

In the UK you can buy used railway sleepers for landscaping, as well as new ones: https://www.uksleepers.co.uk/

I know you "can" buy them but I've never seen them for sale in my state or surrounding ones save the occasional classified posting. Perhaps you can buy them in parts of the country with different regulatory priorities.

Same with telephone poles.

My big orange and blue hardware stores have them and I have used them for landscaping.

creosote railroad ties are commonly found in landscaping around here. unfortunately, they are hazardous waste, thusly getting rid of them is a bit of a hassle.

Not sure the point is to recycle it but rather to have a more carbon friendly alternative to steel. It would also have the benefit of making us less reliant on steel in places where wood supply is ample.

It's entirely possibly to make steel with an electric arc furnace powered by your choice of energy input.

And steel is 100% recyclable, indefinitely.

Hard to beat.

“your choice of energy input” is carrying a lot of weight in your statement. producing steel from iron ore is extremely energy intensive. it’s true that once produced, recycling steel is less expensive.

but steel doesn’t store carbon (except the small carbon input used to turn iron to steel)

wood, on the other hand, is a carbon sink.

Remember to factor in all the trees that will need to be cut down in order to provide the wood.

Of course, over time we can increase the amount of industrial forest, but that will take 40-50 years.

That's the whole point, to remove trees from the land, so new trees can grow and extract carbon from the atmosphere.

no, wood is not a carbon sink. its gets turned back into co2 as it decomposes.

actually recycling steel is not 100% lossless in that everytime you decrease purity which leads to a point where the still can only be used in low grade products. building materials is usually one of the low tiers though.

Iron ore is contaminated with all sorts of crap, far worse than scrap steel. If what you are saying were true, it would be impossible to make high-grade steel from iron ore.

Impossible in an electric furnace (which could be powered by renewable sources).

Virgin steel requires the higher temperatures of a coke-fed blast furnace.

It does require a reducing gas such as the CO produced by coke, but an electric arc furnace can of course reach higher temperatures. Iron can be smelted successfully from ore even without a high enough temperature to melt it, as in bloomery smelts, but the quality of the resulting metal is quite uneven.

then again we have hundreds of years of economies of scale in place for that process, and (presumably) far less for repurifying steel. I'm not saying it's not possible, of course it's not, but is it financially viable with current infrastructure? I'm genuinely asking, I don't know anything about this.

I'm no expert either but I think you can use the same process, though most steel recycling is instead done more cheaply done in EAFs.

Sure but the infrastructure required to do that is probably (my guess) more extensive than a wood press and some chemicals

> > a more carbon friendly alternative to steel.

> Hard to beat.

Since wood is actually carbon negative, it still manages to beat steel.

The article cites them on the carbon impact, as if to say it's an environmentally more-sustainable option. And the reduced carbon impact is great, but I'm sure it's not the only factor to consider in the overall sustainability and my attention was drawn to the ability to recycle, since we (not you, but certainly _me_) are being lulled into thinking that it's "just wood".

Well, as they say, "Perfect is the enemy of wood".

I suppose if it doesn't decompose that makes it a decent option for Carbon sequestration. That might actually be better in a strange way than if it did break down.

It's probably the same process as this video on making bulletproof wood: https://youtu.be/CglNRNrMFGM?si=hfDKE33s7YlB1e9L

Compress the wood and then inject it with resin to stabilize it. Effectively it's only very partially wood and more resin at the end.

After double checking, the video references the science paper from the article, so yes, it's 100% the same process.

Where in that video do you see the injection of resin mentioned? I didn't immediately see that step from skipping through, and it's not mentioned in the abstract of the paper.

Yeah, just watched that very entertaining video and there is no resin in that bulletproof wood - it's just had all the lignin squeezed out and cooked under pressure.

Yeah my bad I confused it with another one of his videos.

No, this process doesn't involve adding any resin or other binders. The result is still entirely wood.

In addition to recycle issue, paper cups also have PFAs that goes to our bodies.

Call me cynical but I expect that if it's anywhere as good as the promoters claim competing industries will lobby and astroturf until whatever glues they're using get neutered or rendered economically much less viable on an environmental basis or they'll find some niche performance area where it's worse and get the building code written in a way to use this deficiency to make it much less frequently usable and it'll be 20yr of that incrementally getting rolled back it actually gets used it in any volume.

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