Live data from Hacker News

Robotic 'trees' can turn CO2 into concrete

engadget.com

41–50 of 125 posts

Re: Robotic 'trees' can turn CO2 into concrete

#41
post #21

Earlier quoted context omitted.

You'll also need to store it in a way that does not release the wood's CO2 back to the atmosphere by biodegradation.

Wood used in construction seems to degrade very slowly. I've lived in houses whose the floor alone was a couple hundred years old.

That's in dry conditions though, it'd probably be gone by now if there wasn't a roof.

Re: Robotic 'trees' can turn CO2 into concrete

#42

Unless we stop burning fresh carbon, this makes no sense. The power has to come from somewhere , and if that isn't renewable energy, it's going to be a net loss. If it is, we should be substituting it in for fossil fuel instead of spending it on capturing carbon.

Also nuclear, unless you're counting that as renewable.

In any case, this process also produces concrete, and regular concrete production accounts for 5% of our CO2 emissions. So this reduces our emissions on top of absorbing ambient CO2.

Re: Robotic 'trees' can turn CO2 into concrete

#43

I wish more people realized the concrete thing is snake oil. When you make cement, you heat up natural CaCO3 -> CaO + CO2. The heat itself also requires combustion, so more CO2. Some cements have perhaps 10% CaCO3 added to their mix. It’s not so much desirable as cheap filler. What the media fails to realize is pumping CO2 into curing cement reverses the CaO reaction. In other words, every CO2 molecule you capture re…

How about this?

https://money.cnn.com/2018/06/12/technology/concrete-carbonc...

Re: Robotic 'trees' can turn CO2 into concrete

#44
post #32

Earlier quoted context omitted.

I think all these comments about wood eventually releasing the carbon back into the atmosphere are missing the point. We don't need to capture it forever, we just need to get the ratio between carbon output and input under control in the next couple of decades. That should give us enough time to come up with longer term and sustainable ways of our planet... until we encounter the next problem, and so on. "Solutions"…

Additionally, if you permanently dedicate 1 acre of land to growing trees, then an acre of trees' worth of wood is permanently captured - though the individual trees may die and rot, more will take their place.

Or use it to build homes, which still keeps it out of the atmosphere

Re: Robotic 'trees' can turn CO2 into concrete

#45
post #13
post #12

Earlier quoted context omitted.

If you use it to build homes you provide shelter for more people.

Building houses is great, but if you're growing the trees in order to sequestrate carbon , you'd better be reasonably sure a decent proportion of the wood doesn't release it's carbon within the next fifty years. I don't live in a country where wood is a major building material, but I'm imagining that most wood that goes into building gets discarded within a few decades and ends up decomposing or being burnt.

If treated and maintained right it can last hundreds of years. So this is not really an issue and if you replace it with new wood it will still store carbon.

Re: Robotic 'trees' can turn CO2 into concrete

#46
post #19
post #13

Earlier quoted context omitted.

Building houses is great, but if you're growing the trees in order to sequestrate carbon , you'd better be reasonably sure a decent proportion of the wood doesn't release it's carbon within the next fifty years. I don't live in a country where wood is a major building material, but I'm imagining that most wood that goes into building gets discarded within a few decades and ends up decomposing or being burnt.

and wood doesn't make for a building material that can go higher than a few stories.

Of course you're not getting skyscrapers from them but nowadays you can build at least five floors which is not that bad. Most buildings are below that I think.

Re: Robotic 'trees' can turn CO2 into concrete

#47
post #32

Earlier quoted context omitted.

I think all these comments about wood eventually releasing the carbon back into the atmosphere are missing the point. We don't need to capture it forever, we just need to get the ratio between carbon output and input under control in the next couple of decades. That should give us enough time to come up with longer term and sustainable ways of our planet... until we encounter the next problem, and so on. "Solutions"…

Additionally, if you permanently dedicate 1 acre of land to growing trees, then an acre of trees' worth of wood is permanently captured - though the individual trees may die and rot, more will take their place.

The only problem is that we don't have nearly enough space for that.

An acre of trees stores ~393 tonnes of carbon dioxide permanently (in Vermont anyway, other areas probably vary a lot) [1]

Humans generate ~40 Gtonnes of CO2 a year. That means we need to be adding ~100 million acres of trees every year to capture that. There's currently 4 billion hectares of forest cover - that's around 10 billion acres.

If we replanted every area which has seen deforestation since 1990 we'd get another 400 million acres, or 4 years of emissions. After that, we're fighting an uphill battle. Forests currently cover 31% of the earth. 29% of that surface is desert, 3% is urban areas and 10% is covered in ice. To keep on top of emissions we'd need to add 0.3% of the total each year globally, or 1.2% of the land which could actually grow trees.

That might be doable in 5 years, but 10 years? 15 years? 30 years?

Re-forestation may be part of the solution, but it can't be the only part.

[1] (PDF}: http://fpr.vermont.gov/sites/fpr/files/Forest_and_Forestry/T...

[2]: http://www.earth-policy.org/?/indicators/C56/

Re: Robotic 'trees' can turn CO2 into concrete

#49

I wish more people realized the concrete thing is snake oil. When you make cement, you heat up natural CaCO3 -> CaO + CO2. The heat itself also requires combustion, so more CO2. Some cements have perhaps 10% CaCO3 added to their mix. It’s not so much desirable as cheap filler. What the media fails to realize is pumping CO2 into curing cement reverses the CaO reaction. In other words, every CO2 molecule you capture re…

Read the page of the company doing it, that's not exactly what they're doing (which you correctly point out it would be pointless) - http://www.blueplanet-ltd.com/

I read it again, twice. That is exactly what they’re doing.

Their starting material is CO2-source cement, not some natural “rock”.

Counterexamples are substantially more helpful than downvotes.

Post reply on HN