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Comment by nebopolis | Hacker News Reader

Poured concrete actually is a passive remover! The issue is the process of baking carbonate rocks at high temperatures to form the cement. This not only takes a lot of energy, but it inherently drives off CO2 from the rock. Over the decades as concrete slowly gets stronger and stronger it absorbs back a small but substantial fraction of the CO2 it emitted.

The way to make this better is to be able to have mixes with lower fractions of cement for a similar level of strength - hence using graphene in this case.

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I found out the hard way that the older concrete gets, the stronger it gets.

Was trying to make a 30cm x 60cm hole in a DIY concrete wall that the last owner of my house had placed over the mains pipe that was leaking from two joints underneath it (I suspect he also DIYed the piping, given its rather unorthodox setup). I had to make room for a plumber to access it.

It was poured in the early 70s, looked pretty, well, homemade, so I figured, easy! Borrowed a concrete breaker, got to it.

3 weeks, very painful wrists from the vibration, and a hired concrete saw, later, I finished my hole.

But holy crap, I had vastly underestimated concrete.

It takes about 40 years for concrete to reach about max strength. I've also experienced the fun of it having lived in a concrete building from the 70s :)

Couldn't this be addressed best by driving the heat on green energy and directly siphoning off the produced CO2 into either underground capture or even green fuels?

I'm still a bit at loss why Climeworks or Prometheus Fuels would pump ginormous amounts of normal air through their respective setups to extract the 0,0004% of CO2 instead of feeding from pure CO2 by industrial processes like this one.

It seems like an easy win on the low hanging fruit to me, and I think there's work on making that practical from Noya Labs: https://techcrunch.com/2021/02/24/noya-labs-turns-cooling-to...

good point, but CO2 is ~415ppm = 0.4 per thousand = 0.04%

It could in theory, but as you say, nobody has created a practical way doing either of those things yet.

CO2 was actually too expensive for enhanced oil recovery for which it is often used since in many cases capturing it in an effective way from industry is just not possible or nowhere near economically viable even at high prices. Hence trump signed a subsidy for co2 sequestration to fight the climate change he didn't believe in.

Since pumping CO2 into the ground is technically just that (even if they don't really care much whether it actually stays there and oil comes out in the process).

Generally the solution to these problems whether it's co2 capture or power to gas at scale is not some future way to defy physics or edge our way up in efficiency towards a distant future where it might be viable but to just emit less. I suspect we'll look at this in the future the same way many look at the plastics industry's takes and propaganda about recycling.

If the CO2 from cement production is mostly sequestered, it ends up being a net negative CO2 emitter. But that's not cheap.

A passive remover but still a net emitter?

Yes, the concrete manufacturing process emits more CO2 than aging concrete absorbs.

Maybe the solution is dense, high rise concrete buildings surrounded by woodland. The size of the woodland being determined by the net emissions from the concrete.

The emissions occur during production. Concrete itself doesn't emit CO2, it's the cement being made from limestone that generates emissions.

I might even prefer that to living in suburbia if you also added room for commercial zoning.

I think the way we designed cities around cars could really stand a serious second look. Cars are really a necessary evil for me. I just bought one after 6 years of not having a car. I wish I didn't need it.

I hear that. We can put bike lanes and a tram track beside the building, shops and amenities at the bottom, and room for food trucks to come and go. It'll be perfect.

More seriously, sorry to hear about the car. It sucks to be that way. I've always been lucky enough to arrange my life around access to public transport (I don't drive) but I've been tempted many, many times.

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