Carbon-negative concrete

https://spectrum.ieee.org/concrete

by mfiguiere • 3 years ago

141 118 3 years ago

spectrum.ieee.org

mchannon7• 3 years ago

Making cement releases carbon dioxide in the conversion of flimsy calcium carbonate to sturdy calcium oxide by roasting it.

Reversing the process by injecting carbon dioxide in curing cement is turning sturdy calcium oxide into flimsy calcium carbonate. Every pound of CO2 you sequester this way necessitates multiple pounds of CO2 released elsewhere to get that oxide to your construction site (production + transportation).

The economics and carbon footprint are similar to corn ethanol- attractive and green if you pay no attention to the total balance.

A corn belt politician I’d expect this from. IEEE should know better.

Y_Y• 3 years ago

I'm surprised a publication aimed at professional engineers thinks it could get away with a sleight of hand like that.

mchannon7• 3 years ago

I doubt it's intentional. It's just the modern day equivalent of a perpetual motion machine or a "machine that makes water out of air" (dehumidifier).

This particular subject matter area falls in a blind spot where electrical, chemical, and environmental engineering meet, and nobody gets rich pulling the rug out like I just did.

I write about this in my book Fat Gas. Plenty of modern-day snake oil salesmen out there.

ZeroGravitas• 3 years ago

They covered a few products and techniques. Which one specifically are you talking about?

The CarbiCrete one for example uses CO2 to cure the concrete, but doesn't use cement.

https://www.sciencedirect.com/science/article/abs/pii/S09596...

steel slag has shown the potential to replace cement as an alternative binder if carbonation activation is performed.

mchannon7• 3 years ago

Since Elsevier is hiding the meat in that journal article, I can only go off what I read, but it looks identically flawed.

• Compressive strength of normal concrete: 25-50MPa

• Compressive strength of their slag concrete with 2h CO2 added: 12MPa

• Compressive strength of their slag concrete with 24h CO2 added: 24.3MPa

My takeaway:

Using slag instead of cement = good idea.

Using slag OR cement plus CO2 = bad idea.

henearkr3• 3 years ago

In this new process, it's not the cement (by its classical definition) that is cured by the CO2 in the air, it's the calcium-enriched biochar. Thus the cement part is still sturdy, and the biochar part avoids making it flimsy because this calcium treatment enhances its binding with the cement.

It looks like the main problem with previous experiments with biochar added in cement was that the biochar did not bind well, making a crumbling result, but this article is about solving precisely that.

mchannon7• 3 years ago

The article claims "[t]his calcium carbonate strengthens the biochar" but this runs counter to my understanding and I'd like to see some numbers, particularly versus alkalized biochar that is never exposed to CO2.

How important is binding in compression (which is what concrete is used for)? Not very.

Carbonate doesn't strengthen, it weakens. And if forming carbonate in biochar strengthens versus standard biochar, I would imagine forming oxide in biochar would strengthen even more.

blurbleblurble• 3 years ago

Why does it have to be either or? Aren't there plenty of use cases for the concrete with less compressive strength? Stuff like floors and walls of smaller buildings could be perfectly fine with the 25 MPa, couldn't they? Patios? Foundations of smaller buildings?

If there's a good amount of stuff that doesn't need the higher compressive strengths, I'd think there could be some decent potential to offset with this stuff. Applications that really need higher strength wouldn't need to use this carbonized stuff.

lostlogin• 3 years ago

For some of those scenarios, couldn’t concrete be abandoned altogether?

Wooden building work pretty well, though forestry has plenty of its own problems (see New Zealand and it’s series of slash disasters).

tristor9• 3 years ago

There's need, and there's expect. Unless you expect every homeowner or other property owner to do expensive and destructive testing prior to a reconfiguration, remodel, or bringing in heavy semi-stationary loads onto their property, it's somewhat critical that concrete behave like concrete regardless of its initial use case.

A simple example is in my previous home when I had a section of the master bedroom closet partially walled around a Class C TL-30 rated firesafe, and the room partially reconstructed with ballistic armor in the walls and a vault door, to turn it into a safe room for valuables + home protection. The safe had a weight of nearly 9000 pounds in a footprint of 64 by 30 inches on the floor. I was only able to do this because the house was a slab on grade construction and we knew the footing depth and slab thickness of the concrete would handle the weight.

If this had been some sort of "eco concrete" it would have cracked and eventually failed under that weight, and we would not have known this because the slab thickness would have been the same.

P.S.: Since everyone always asks because it's hard to find actual safes (most "safes" are garbage RSCs), it was custom built by a local safe-maker and expect to pay $$$$$. The safe I had installed was $35k, and that didn't include the room tearout/rebuild or the vault door, just the freestanding safe that went into the room.

hinkley3• 3 years ago

I don’t think it’s an accident that a lot of the carbon sink concrete companies are doing precast products.

Factory conditions allow for tighter tolerances, which means you can dial in the product. Concrete poured outside has a range, and the worst case scenario is tightly controlled, but at the cost of potentially overspecced concrete. Or at least more expensive workers.

coryrc• 3 years ago

Then you can just use a higher share of aggregate and/or partially substitute cement with weaker but more carbon-friendly pozzolans.

Mystery-Machine• 3 years ago

Transportation can be carbon neutral. So you can remove that from equation. At least there are many ways people are trying to reduce transportation carbon emissions to as close to zero as possible.

moffkalast2• 3 years ago

It can be. But is it? Will it be any time soon? Isn't the Tesla Semi the only EV truck on the market and isn't being produced in any major quantities yet? It'll probably be decades before any of those reach your average concrete production site where they're still using trucks from the 90s.

palata4• 3 years ago

Nothing that uses energy can reasonably be carbon neutral in a world that depends mostly on fossil fuels.

Transportation uses energy, therefore transportation is not carbon neutral.

manojlds• 3 years ago

Could you give some links on claim on ethanol mixing not being a great alternative?

mchannon7• 3 years ago

First one's on me, the rest you can pay for, or google:

https://e360.yale.edu/features/the_case_against_ethanol_bad_...

rch• 3 years ago

I don't immediately see any claims that this material is fit for all purposes regular concrete would be.

The first application that comes to mind for me is an alternative to styrofoam-fill insulating concrete forms. Biochar sounds like an improvement vs even waste diverted styrofoam.

cultureswitch• 3 years ago

Why do you write like Yoda?

xchip• 3 years ago

Spot on, and add you say, IEEE should know better

krick• 3 years ago

Weird to assume IEEE or any other large enough organization that has people being paid money to write posts on the internet (i.e. PR dept) is somehow different from "corn belt politicians" and won't be pushing the same agenda. The main point of doublethink is that people that are not good at it, are not allowed to speak publicly anyway, so it's kinda besides the point if some random engineer has problems evaluating how come that worse concrete is better concrete.

hosh• 3 years ago

It would be interesting to see if:

- this concrete formulation is self-healing like Roman concrete

- Whether that absorption property is dependent on other factors like heat (our cities create a heat island effect)

- Whether adding in things like rebar give rise to any unexpected interactions

photochemsyn2• 3 years ago

The best options appear to be replacing the heat source that drives the calcination step for making cement from limestone with either an electric plasma arc furnace or green hydrogen, both sourced from solar/wind inputs:

https://arstechnica.com/science/2022/11/the-road-to-low-carb...

hannob3• 3 years ago

Replacing the heat source only solves around 1/3rd of the problem. Most emissions come from the calcination, aka the conversion of CaCO3 to CaO and CO2.

photochemsyn2• 3 years ago

Capture the CO2 from the calcination and make diamond out of it?

cptskippy• 3 years ago

Maybe it's my misunderstanding but isn't concrete usually prepared local to the construction from ingredients like cement that are shipped in from remote locations?

To get around that problem, the duo first treated the biochar with waste water that was produced during concrete production.

Is the waste water from biochar-cement based concrete suitable for use in creating subsequent batches of biochar-cement?

How feasible is it to capture this waste water from producing the concrete and ship it back to the cement factory for producing cement?

ThorsBane• 3 years ago

This is really amazing news. This in addition to rapid global adoption of renewables at the present rate are remarkable and encouraging breakthroughs.

dylan604• 3 years ago

Hate to burst your bubble of excitement, but just today (or over the weekend) Texas is in the news for the wrong reasons (yet again, and no guns involved in this particular news). Legislation is being pushed to encourage natural gas and slowing down wind/solar. New regulations to place annual permits on wind farms because of the blight on the scenery type excuses. The people are gas lighting the public (pun intended) to the point that they blame renewable energy for the failures of the gas plants during the '21 freeze and the public is accepting it. So in Texas, discounts for fossil fuels, extra fees for renewables.

palata4• 3 years ago

This, plus the fact that nothing remotely competes with fossil fuels. The simple fact is that after fossil fuels, we will have less energy, and there is no silver bullet: we need to start doing less with less energy, and stop hoping for a technological breakthrough that will save us.

Bad news is that we still have enough fossil fuels to finish screwing up the climate.

gregwebs• 3 years ago

Finally, he adds, biochar is made from “biomass that otherwise will be landfilled where it releases carbon dioxide, or methane, which is a stronger greenhouse gas than carbon dioxide.”

I thought biochar is a carbon stable form that is in demand as a soil amendment?

Sharlin2• 3 years ago

Biochar is simply charcoal with some specifics as to how it's made, and charcoal is just pyrolysed biomass.

waldothedog• 3 years ago

Yes. The quoted line is saying that NOT using the materials to make bio char would mean losing the 100 years of carbon stability, and instead generating methane if dumper into landfill.

dumpHero2• 3 years ago

Here's a VOX video about this problem, pretty cool! : https://www.youtube.com/watch?v=asLWBGtAhZk

betimsl• 3 years ago

BOOM! -- with ONLY one move, world is getting better and better everyday!

I know this sounds idealist, but, They should make this patent free to all.

clnq• 3 years ago

A startup called CarbiCrete is also developing carbon-negative concrete. Instead of cement, the company uses waste slag from steel-making in its concrete mix, and uses carbon dioxide captured from industrial plants to cure the concrete. One downside is that the concrete has to be pre-formed and cannot be poured and set on site.

What a big obstacle to adoption — too many building techniques rely on on-site pouring, I hope they can engineer some solution.

yetihehe• 3 years ago

I've used a lot of prefab concrete blocks for my house. For foundations - big concrete bricks, for ceilings - big prefabricated long strips with rebar. Of course, not all, but it's most of concrete used in my house. You could also make small pavement bricks from that, it doesn't need to be poured in place and uses noticeable amounts of concrete, it's used a lot in Europe.

Sharlin2• 3 years ago

Most multi-storey buildings are made from prefab elements at least where I'm from. Making those carbon-neutral would be a big deal, even if the concrete couldn't be used for bridges and whatnot.

tastyfreeze2• 3 years ago

biochar != charcoal

Charcoal is black carbon produced by incomplete combustion of ligneous material. Biochar is charcoal that has been filled with nutrients, bacteria and fungi.

jdmichal• 3 years ago

https://en.wikipedia.org/wiki/Biochar

Biochar is the lightweight black residue, made of carbon and ashes, remaining after the pyrolysis of biomass. Biochar is defined by the International Biochar Initiative as "the solid material obtained from the thermochemical conversion of biomass in an oxygen-limited environment".

You may be thinking of biochar specifically as a soil amendment, where it is sometimes loaded with probiotics and such:

https://en.wikipedia.org/wiki/Biochar#Soil_amendment

She pointed out that when pre-charged with these beneficial organisms, biochar promotes good soil and plant health.

tastyfreeze2• 3 years ago

Charcoal has been the word used for "the solid material obtained from the thermochemical conversion of biomass in an oxygen-limited environment" far longer than the word biochar has existed. Biochar is a portmanteau of biological charcoal.

It also looks like the quote from the biochar wiki page is a near copy from the charcoal page.

https://en.wikipedia.org/wiki/Charcoal

There is plenty of confusion over the word "biochar" even among gardeners that use it. It is always pre-charged before adding to soil. Adding raw charcoal will rob the soil of all nutrients and kill plants.

Yay pedantry!

throw0101b• 3 years ago

Vox recently had a good video on the topic:

* https://www.vox.com/videos/2023/4/20/23691222/cement-carbon-...

* https://www.youtube.com/watch?v=asLWBGtAhZk

mbfg• 3 years ago

For those wanting to know more about concrete and cement, Veratasium has a newish video:

https://www.youtube.com/watch?v=rWVAzS5duAs

hannob3• 3 years ago

It seems that there is now an increasing number of startups and researchers trying some form of completely unusual cement production to lower the carbon footprint. This is in principal a good thing, but...

I can't help to think that such overhyped reporting isn't helpful. Concrete will not be caron-negative any time soon. This is very early research. It's good that it's being done, but it should also be clear that this is very far away from an industrial process that can be used for real.

dheera• 3 years ago

What if the lifetime of the building is considered? Don't concrete buildings presumably last much longer in the face of fires, tsunamis, and other disasters? Whereas entire towns of wooden houses get ravaged by fires every year in California?

Speaking of which, is there any possibility of making a brick that is 80%+ carbon (for the purpose of sequestration) and non-flammable? Like some sort of low-cost carbon fiber brick?

MobiusHorizons• 3 years ago

Corbin fiber != co2. Carbon fiber is unburnt carbon. It is pretty heat resistant, but is still flammable under the right conditions. I’m not sure how you would use that for sequestration. Ideally you would want the co2 to bind to a solid chemically so you get better density of co2 storage. I suppose you could just fill cavities in a brick with co2 gas, but that would store very little carbon dioxide and runs the risk of leaking back out.

stronglikedan• 3 years ago

If Veritasium is to be believed, we use more cement than any other substance apart from water, so imagine the impact that lowering the carbon footprint of concrete, even just a little, would have.

https://www.youtube.com/watch?v=rWVAzS5duAs

porkbeer• 3 years ago

He is not.

akira2501• 3 years ago

such overhyped reporting

What part of the reporting did you feel was hyped?

What I took from it is: Some researchers and companies are working on similar projects to reduce carbon footprint of concrete. Some have some interesting results but with some rather extreme compromises. It ends with industry not being interested yet, but work continues anyways.

Isn't the exactly the level of reporting you would expect from an insider publication like IEEE?

hannob3• 3 years ago

The headline implied something that isn't true.

broguinn• 3 years ago

Biochar is made today by heating waste materials like wood chips, rice husks, or *water-treatment sludge* at high temperature in a low-oxygen environment.

Holy shit.

hinkley3• 3 years ago

I don’t see if they way where they source the biochar. I think ultracap people switched to bamboo biochar for superior structure. There’s probably a different trade off for structural materials. Say poplar or Osage orange.

AgentOrange1234• 3 years ago

I love the privacy policy. We will do whatever we want, we don’t respect DNT, you cannot opt out. No thanks IEEE.

Carbon-negative concrete

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