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Robotic 'trees' can turn CO2 into concrete

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Re: Robotic 'trees' can turn CO2 into concrete

#101

Post by roryisok »

mirimir wrote: post #75

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.

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.

Re: Robotic 'trees' can turn CO2 into concrete

#102

Post by gascan »

ForHackernews wrote: post #26
torpfactory wrote: post #18

Earlier quoted context omitted.

Doesn’t a forest tie up the carbon in live trees? A mature forest will be more or less carbon neural but a certain amount of carbon won’t be available to the atmosphere.

The trees will die eventually. The problem is that we've released a lot of CO2 from trees that died millions of years ago.[0] If you want to get that out of the atmosphere, it's not good enough to grow trees today because in 50-100 years (or whenever a tree dies) you're right back where we are today. [0] https://www.nationalgeographic.com/science/phenomena/2016/01...

The tree which dies is replaced by a new tree.

You're right that we've added more carbon than can be stored in living forests. But reversing deforestation can & should be part of the solution.

Re: Robotic 'trees' can turn CO2 into concrete

#103

Post by roryisok »

TangoTrotFox wrote: post #63
stronglikedan wrote: post #58

Earlier quoted context omitted.

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

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 wors…

> 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.

I'm not sure that we should keep telling ourselves we have many decades to fix this problem. If (ok, when) the arctic permafrost melts we could see runaway warming. Even without that, we put more carbon in to the air every year, every year this problem is harder to solve. Thinking we have decades to fix it is the main reason we're here, now, with heatwaves and wildfires and acidifying oceans

Re: Robotic 'trees' can turn CO2 into concrete

#104

Post by Reason077 »

logfromblammo wrote: post #84
throwaway5752 wrote: post #64

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... 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 f…

How about this? Create an Africa-sized algae bloom with iron and urea fertilization, in the middle of the waste-plastic zone in the north Pacific gyre. Krill eat the algae. Baleen whales eat the krill and the plastic. Then we train/drug the older whales, so they swim far away from the continental shelf, dive deep, and commit suicide on the bottom. We solve two problems with one stroke. (Then the gorillas just freeze…

Algae/phytoplankton tend to sink to the bottom of the ocean and become a long-term carbon store when they die anyway. That's how much of the oil and gas we're burning today was formed in the first place. No need for elaborate training of whales :)

Re: Robotic 'trees' can turn CO2 into concrete

#105

Post by roryisok »

hendryau wrote: post #51
konschubert wrote: post #48

Earlier quoted context omitted.

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

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…

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

Re: Robotic 'trees' can turn CO2 into concrete

#106

Post by roryisok »

aeternus wrote: post #100
leoedin wrote: post #47

Earlier quoted context omitted.

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 repl…

There is a lot more area in the ocean and seaweed grows very quickly. Perhaps we could even accelerate the sequestration by building large seaweed farms over the deep ocean, then sinking the seaweed once it grows large enough, & repeat. Related: https://oceana.org/blog/seaweed-could-be-scrubbing-way-more-...

I think this is going to have to happen for bio capture to work at all. We need land for food, and we'll need increasingly more of it in the next decade thanks to overfishing, and population growth

Re: Robotic 'trees' can turn CO2 into concrete

#108

Post by 08-15 »

throwaway5752 wrote: post #91
08-15 wrote: post #86

Earlier quoted context omitted.

You know what's the problem with that idea? There are no "sequestration and efficiency innovations". Sequestration doesn't work and takes too much energy, and efficiency cannot be improved much thanks to thermodynamics. Besides, if the IPCC is correct about how bad CO2 is, the only sensible cap for emissions is zero. You don't get there with tiny improvements in efficiency.

I'm sarcastically saying that we had proposals for a cap and trade system that would have mitigated it but it was destroyed for political reasons.

Obviously. I'm non-sarcastically saying that cap-and-trade won't work, because any meaningful cap is unrealistic to achieve. The political reason is: We want cheap energy. The politically acceptable choices boil down to burning coal or gas, no matter how bureaucracy is layered on top.

Re: Robotic 'trees' can turn CO2 into concrete

#109

Post by LeifCarrotson »

ksdale wrote: post #80
OscarCunningham wrote: post #76

Earlier quoted context omitted.

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

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.

> 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.

Re: Robotic 'trees' can turn CO2 into concrete

#110

Post by OscarCunningham »

LeifCarrotson wrote: post #109
ksdale wrote: post #80

Earlier quoted context omitted.

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.

> 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…

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!

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