
Robotic 'trees' can turn CO2 into concrete - rbanffy
https://www.engadget.com/2018/09/11/robot-trees-co2-into-concrete-climate-change/
======
throwaway5752
Seriously, everyone suggestions a crackpot idea for sequestering carbon should
do the basic arithmetic for how much annual human emissions are (40 billion
metric tons).

I like [https://blogs.scientificamerican.com/life-unbounded/the-
craz...](https://blogs.scientificamerican.com/life-unbounded/the-crazy-scale-
of-human-carbon-emission/) for the perspective it offers: current human CO2
emissions are equivalent to the entire continent of Africa being covered in
coniferous forest and burning to the ground in forest fires, every year.

 _If_ there is any way we save ourselves from this, it's from reduced
emissions.

~~~
OscarCunningham
How is that possible? Surely the volume of fossil fuels being burnt isn't
remotely comprable to the volume of that forest.

~~~
ksdale
I don't know if the math is correct, but oil and coal are far more energy
dense than wood which may account for the discrepancy.

~~~
LeifCarrotson
> _oil and coal are far more energy dense than wood_

In addition, a block of wood is a lot more dense than an acre of forest, which
is a lot more dense than the difference in carbon content between an acre of
forest and an acre of charred burned forest.

While reading the article, I mentally substituted "a forest the area of
Africa" with "an oil tank the size of Africa and as deep as a forest is tall",
which is clearly unreasonable. And they mention "4.81 tons" in passing - a ton
is a lot, and surely 4.81 tons is a huge volume of gas, but how much?

We need to run the numbers. Crude petroleum has a density of about 0.8 g/cc =
0.8 ton/m^3 and a carbon composition of 85%.

    
    
        4.81 tons of carbon x (1 kg crude / 0.85 kg carbon) x (1 m^3 / 0.8 ton crude) 
    

= 7 m^3 of crude. Looking it up, a typical tractor-trailer tanker truck might
carry 40 m^3 of crude...so this can be stated as mankind burning a yearly
volume of one truckload of fuel for every 6 acres in Africa, which is a lot
more believable.

Going back to the oil-per-acre analogy, an acre is a little more than 4000
square meters, so (assuming it's all oil - ignoring coal, natural gas, and
other CO2 producers like, I don't know, human-initiated forest fires) _this is
a film of oil over the continent of Africa 1.7mm deep._ That's a lot more
believable than imagining a towering petroleum forest.

~~~
OscarCunningham
Thanks for doing the maths! That gives an intuition more in line with what I
would have suspected.

Equivalently it's the anount of oil needed to cover Costa Rica to a depth of
1m. Still quite a lot!

------
innocentfelon
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 releases 2 or
more. You’d be better off using less CaO and more CaCO3 to begin with.

~~~
raverbashing
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/](http://www.blueplanet-ltd.com/)

~~~
innocentfelon
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.

~~~
raverbashing
It seems they're not replacing the quicklime, but the gravel. The left column
is confusing, the right column is better.

> A rock particle is coated with our synthetic limestone, forming a carbon-
> sequestering coating that is 44% by mass CO2.

That's where the CO2 goes, not in curing the CaO

~~~
08-15
But where does the Ca come from? Obviously not from limestone...

------
arlindohall
I have a hard time taking an article seriously who uses an image of water
vapor coming off nuclear cooling towers as an example of carbon emissions from
energy production.

~~~
tlb
Those sort of cooling towers aren't just for nuclear power. They're the most
efficient way of cooling anything, unless you're next to a river. Judging from
the railway and storage around it, I think that's a coal plant.

~~~
hanoz
Indeed it appears to be Drax coal-fired power station in Yorkshire
([https://en.wikipedia.org/wiki/Drax_power_station](https://en.wikipedia.org/wiki/Drax_power_station)),
Britian's largest emitter of carbon dioxide.

------
6nf
Every time one of these articles come up I wonder about the price per tonne of
CO2 removed by simply growing wood and not burning it. I'm not really sure
what that price is, but it seems to be around $20-$40 per tonne? Does anyone
have a more accurate number?

~~~
ovi256
If the purpose is carbon sequestration, you'll have to include the cost of
storing that wood. Indefinitely. Won't be cheap.

~~~
bastawhiz
You could sell it, maybe trick people into doing stuff with it, like making
buildings or durable goods.

~~~
Already__Taken
This was interesting:
[https://www.ted.com/talks/michael_green_why_we_should_build_...](https://www.ted.com/talks/michael_green_why_we_should_build_wooden_skyscrapers?language=en)

------
acjohnson55
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.

~~~
DennisP
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.

------
xupybd
“Climate change is killing our planet“

I wouldn’t go that far. Sure it’s making it less hospitable for us and much of
the complex life here. But life will go on without us.

~~~
stronglikedan
I guess you're being downvoted for pedantry, because your statements are
accurate.

~~~
TangoTrotFox
More like sensationalism. I don't downvote, but the comment is absolutely
ridiculous. Even the absolute worst case scenarios for climate change are not
species ending events _with current technology._ And we have many decades
ahead of us yet where can solve the problem with future technology yielding a
negligible overall impact.

That said even the mild effects are undesirable and seeing how close we'll
come to the worst case scenarios is not really a very smart experiment to be
carrying out, but somebody stating climate change is going to kill off
humanity is a perfect example of the horseshoe of idiocy that's affecting
people as they surround themselves only with agreeable voices. It's how some
people today can still try to argue that the climate isn't changing. It relies
on echo chambers that all agree to ignore all facts and just go further and
further off their respective deep ends.

~~~
stronglikedan
You seem to have read a lot more into the parent comment than I did. I read it
as a simple rebuttal to the articles opening statement saying climate change
is killing the planet. While it's impossible for climate change to kill the
planet, it is possible to render it too hazardous for humans if left
unchecked.

~~~
xupybd
That is all I was trying to say

------
thinkcontext
With costs of $100/ton and up Direct Air Capture should be researched but not
deployed today. We should first concentrate on more cost effective solutions.
We'll likely need DAC eventually but there's lower hanging fruit.

------
mirimir
In order for non-biological CO2 capture to be workable, we'll need to ramp up
energy production maybe 5-10 fold. Without releasing substantially more CO2.
Covering the Sahara and US Southwest with PV (and wind farms, where
appropriate) might make the nut. But if we manage to dig too huge a climate
change hole, we'll likely need more like 20-100 fold more energy. Maybe
fusion, or massive orbital solar arrays.

~~~
roryisok
I read some encouraging recent reports that a Sahara PV project would not only
generate about 5 times the energy requirements of civilization, it would also
increase rainfall in the Sahara and probably lead to greening. Meanwhile
offshore wind in the North Atlantic could also supply multiples of the energy
we need. These combined would be sufficient to free us from fossil fuels,
future proof us against the increase required from electric vehicles for a
decade or two and have plenty left over to power carbon capture projects.

~~~
mirimir
Yes, thanks :) That's what I was thinking of, and ought to have mentioned it.
It was on HN within the past week or so.

And yes, that could be a great outcome. But sadly enough, I suspect that the
situation will get a _lot_ worse before the US, at least, does anything
substantial.

------
KirinDave
So, this $600/ton plant sits on top of... an incinerator. So uh, they're
literally starting a fire for the sole purpose of capturing SOME of the carbon
and shuffling it off to... be released into the atmosphere again elsewhere in
greenhouses which will not capture it.

Ugh. 𐑜𐑸𐑚𐑩𐑡 𐑐𐑰𐑐𐑳𐑤.

Why do people like this take the future of our species for granted? This isn't
funny.

------
stephengillie
Grow these on top of hills and mountains, then use the tech from the other
thread[∆] to lower the blocks and generate electricity too.

[∆][https://news.ycombinator.com/item?id=17958700](https://news.ycombinator.com/item?id=17958700)

------
roryisok
I've read a lot about carbon capture lately, and this is one of the most
promising approaches. Another very interesting idea is simply splitting the
CO2 into oxygen and carbon monoxide

------
hendryau
If only someone would invent something that could be stuck into the ground
that would just suck CO2 out of the air. Hmmm...

~~~
konschubert
... and never release it again, unlike trees.

~~~
hendryau
It doesn't need to be stored forever. As trees die and are farmed, they are
replaced by new ones. Large forests in conjunction with reduced CO2 emission
and renewables is the best answer to climate change, not some band-aid to mask
the problem.

Land usage is abysmal, and there's a lot of waste. Stop cutting down trees and
stop urban sprawl.

As a side effect we might just be able to stop a mass extinction due to loss
of habitat.

~~~
roryisok
I agree there's a lot of waste but with the population expected to go up by
3-4 billion in the next decade that urban sprawl is not going to stop, and
we're going to need 2x more land for food, especially as we're overfishing our
acidified oceans _today_. Bio capture it's just not feasible because of the
land required

