Robotic 'trees' can turn CO2 into concrete | Hacker News Reader

Robotic 'trees' can turn CO2 into concrete

engadget.com

97 pointsrbanffy118 comments

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 fires, every year.

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

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.

This would have been my explanation too, but to my surprise, wood is only about 1/3 of the energy density of diesel fuel. I'm not sure why i expected it to be an order of magnitude difference.

https://en.wikipedia.org/wiki/Energy_density#Energy_densitie...

Interesting! I too, would have expected a much larger difference.

I think the math is somewhat wrong. The original source link for that "4.81 metric tons per acre" number is broken, but it appears to be talking about tons of carbon, not CO2 (which is roughly 27% carbon by mass). The article underestimates the amount of CO2 released by forest fires by roughly a factor of 4, and therefore overestimates the required land area by the same factor.

It's still a pretty staggeringly huge amount of land, though.

> 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.

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!

Living trees are only about 15...18% carbon by weight. [1] Other greenery is probably even less, given that significant proportion of trees' mass is in the trunk as cellulose (some 50% of it)[2], which is about 44% carbon.

On the other hand, CO2 is only about 27% carbon (also by weight). [3]

[1] https://web.extension.illinois.edu/askextension/thisQuestion...

[2] https://www.britannica.com/science/cellulose, https://en.wikipedia.org/wiki/Cellulose

[3] mostly O16, mostly C12, 12 / (12+16+16)

> should do the basic arithmetic

North America is sitting at around 6.5Gt p/a, three [experimental] plants sequester 0.55Mt p/a. You'd need 35000 plants in just North America. 216000 plants world-wide.

Concrete production accounts for about 5% of CO2 emissions, so this does reduce emissions.

And turning a source into a sink is better than stopping. Assuming that this process takes more energy than the current process, you could still be looking at a target of, say, 8% reduction of anthropogenic carbon.

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 to death when winter comes.) ~

I think the only workable schemes for active carbon sequestration involve artificially weathering calcium and magnesium containing oxide rocks to expose more surface area, and turn them into carbonates. That has to be done on a scale that far exceeds the entire global demand for concrete. Like building a 1:1 scale replica of the white cliffs of Dover, every year, for no economically exploitable reason. Grind up olivines, pyroxenes, calcium-rich plagioclases, periclases, perovskites, spinels, etc. into sand, eventually get chalk.

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 :)

Reduced emissions are not enough. Even if we got to zero emissions worldwide in the next 20 years (impossible), the excess carbon in the atmosphere already needs to be dealt with. There are greenhouses gases coming from the permafrost. The forest carbon sinks we depend on are being reduced every year by logging and wildfires. The ocean is heating up and probably becoming less effective as a carbon sink. Basically, not only are we putting out more carbon per year, we're also removing less of it. We need more crackpot schemes, and we need them yesterday. Not instead of emission reduction but in conjunction with it

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.

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.

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

But where does the Ca come from? Obviously not from limestone...

How about this?

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

so you're claiming this isn't a functional perpetual motion machine that (bonus) outputs useful building materials? come on

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.

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.

Yes. But whatever, they're still cooling towers. No CO2 comes from there, just water vapor. But many, I suspect, think that they're squat smokestacks.

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

Oh cool! I didn't realize that design was widely used, although it makes sense. If it can cool water for a nuclear plant then no reason it can't cool water for anything else!

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?

Rotting wood releases carbon dioxide too.

You don’t let it rot. You mill it, and scorch it. That will give you a couple hundred years of protection. Then you start stacking the timbers in a pyramid. As you add more and more layers to the pyramid, the bottom layers compress, eventually becoming totally uninhabitable by bugs and bacteria. Over time you end up with a giant pyramid made of coal, and possibly diamond. (haven’t done the math on how tall you have to stack coal to get diamond)

this is starting to sound like minecraft

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

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

If you turn it into charcoal you keep most of the carbon locked up in a non-biodegradable form.

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.

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.

Here's a 14 story wood-based apartment building in Norway:

https://www.youtube.com/watch?v=e5XsqauBCX4

http://treetsameie.no/

There are many other wood-based buildings higher than that being planned. The key for most of them is the use of various hybrid wood-laminates.

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.

> if you replace it with new wood it will still store carbon.

Good point, although you need to be sure you aren't counting the wood you replace it with as more carbon storage. Every wooden house essentially provides a fixed amount of carbon storage, no matter how much of it is replaced, and only as long as it stands.

We need to unburn roughly as much coal as we've burned. We're talking about hundreds of billions of tons. You could probably plaster the whole surface of the planet with homes and not have used enough wood.

And you can add it to soil where it works wonderfully at increasing biomass, reducing water runoff and increasing the number and variety of microorganisms in the soil, sequestering more carbon.

http://en.wikipedia.org/wiki/Terra_preta

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.

Scorched timber can last a hundred years. I have seen a cabin from 1740 made of timber from trees that were scorched in a forest fire but remained alive.

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

Best comment I have read all day.

This was interesting: https://www.ted.com/talks/michael_green_why_we_should_build_...

Burn them for their energy and keep more coal in the ground seems like a good first step.

but wood burns so much more dirtier than coal, and leaves much more uncombusted remains that then have to clean.

The problem is energy (or lack thereof) - and so why not solve it directly by adding ever larger sources of renewables, which eventually will becomes enough that there's no need to burn any fossil fuels!

Is that so? Even when ground fine and with enough oxygen? For local heating, I heard good things about the efficiency and cleanliness of wood pellet heaters.

Did you hear those things from either people trying to sell you a wood pellet burner, or people who've just spent a lot of money money on a wood pellet burner?

Personal anecdote- i bought a house with a wood pellet stove as a primary heat source. There was smoke damage to the paint everywhere.

We can bury it until it becomes oil again.

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.

For comparison. A ton of CO2 is roughly the equivalent of a London-NYC roundtrip in the economy class. https://calculator.carbonfootprint.com/calculator.aspx?tab=3

There's got to be something that grows faster, and is easier to sequestrate, than trees. Bamboo, maybe? Seaweed? Algae? Dry it off in salt pans and dump it in the deep, cold ocean?

That's just dumping more carbon into one of our natural sinks, I think, rather than trying to create a new artificial sink. Even just using it as fertilizer has got to be an improvement over using inorganic fertilizers.

Iron fertilization

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

Thank you for posting this - the link is very interesting.

Cool idea, I'd never heard of this. TL-DR is that there are huge portions of the ocean that are nutrient-rich but have little life, and one hypothesis is that iron is the limiting factor here. Since various phytoplankton need iron to survive, why not dump iron in these places, watch the phytoplankton now thrive, and enjoy their carbon sequestration?

The answer seems to be "well, we don't really know what the effect would be". Some algae blooms are not good (red tide), deliberately altering an ecosystem is generally dangerous, it's not clear whether the positive local effect on carbon has some side effect elsewhere (maybe we're just moving phytoplankton around the ocean). Even doing experiments on this is difficult (the world's oceans are weirdly regulated), and current financial incentives don't make it all that enticing either.

But a cool idea.

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" don't have to be perfect forever. They just need to work long enough till better solutions are discovered.

You could also just bury it. That’s effectively putting coal back into the ground.

Wood is not dense enough for this to be cost effective.

You could burn it – the ash from burning a tree takes up only a fraction of the original volume.

Don’t know if this is sarcasm, but burning the wood releases most of the carbon dioxide back into the air. The ash is just the unburnt carbon residue and other leftovers.

Yes, it was a joke. Sorry for that.

Jokes aside, you could partially burn it, into charcoal, then grind down the charcoal, soak it in urea, and mix it with soil. The charcoal bits remain stable in soil for quite a long time, and helps retain plant nutrients.

If a woodpile isn't dense enough, then surely building homes and furniture out of wood isn't dense enough either.

Can you think of a better way to store carbon!

Not very dense compared to the cost of digging a big hole in the ground with Caterpillars and the number of truck loads of pellets you would need to bring in. This is all assuming that just covering the wood over with dirt is enough to keep it sequestered, a big pile of biomass could start emitting methane.

> Can you think of a better way to store carbon!

BECCS like they referred to in the article.

Building with it is a lot more effective as there's economic incentive in preventing it from decaying back to base elements

Good point.

I have a better idea. Leave the coal in the ground. You get the same result with literally no work!

Way too reasonable, it'll never happen.

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

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/

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.

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

And if we could forest up some places where there's no forest at the moment, a large fraction of that carbon would be tied up there basically as long as that forest stays up.

For the most part we have been doing that for decades. The US has a lot more forests now that 100 years ago (the height of logging).

It is hard to know for sure, but there is reason to believe we have more trees than even 1000 years ago. We are not allowing forest fires to clean out the dead trees which allows them to build up. This is a negative, regular forest fires burn colder and leave a lot of charcoal in the soil, while the less regular forest fires burn hotter and so release that carbon back into the atmosphere.

So I didn't believe this statement (eg: more trees than 100 years ago), bc I'm the skeptical sort. You're right though. I looked at "US Forest Resource Facts..." page 8 and the numbers are higher for millions of acres across different types. https://www.fia.fs.fed.us/library/brochures/docs/2012/Forest...

Well, according to Energy and Civilization forest stores an average of 1 watt per square meter in burnable wood. Wood burning is pretty carbon intensive as energy goes so I imagine that each square meter of forest, if the fallen trees are buried deep underground, could offset several watts of internal combustion engine use.

Nope. The energy density of gasoline and wood per carbon atom is about the same. So a watt is a watt, and forest are inefficient (about 0.4%) at converting sunlight into chemical energy.

Carbon in trees is still part of the carbon cycle, it will eventually be released again though it may be buffered for a time. That's merely neutral as opposed to negative that you get with sequestration.

True, and the current CO2 problem is exactly because of that eventual release - it's just that the CO2 was locked in oil and coal from millions of years ago. Growing trees would work, but only as long as their decomposition can be stopped (like it did when coal formed) or at least limited so that not all their CO2 is released and a big part of it returns into the ground.

But, major tree growing operations are already being done, lots of companies are into the CO2 trading business where growing trees = an X amount of CO2 emission rights they can sell to CO2 producing companies / factories.

A 1 hectare (10k m^2) poplar plantation yields 30 tons of wet biomass per year; average carbon content of wet wood is 15-20%; that would translate into 4.5 tons of co2 sequestered per year (assuming that all the carbon comes from the atmosphere).

To offset 5GT of carbon dioxide emissions per year, you'd need 110 million hectares, or 1.1 million square km, that is 13 times the surface of Kansas. Then of course every year you'd have to cut down something like 1/7th of the trees, throw them in a big hole, and replant them. Just about doable, I'd say. :)

Taking your estimated numbers it's interesting to add that cost to the price of fuel and see where it gets you. A gallon of gasoline on average produces about 20 pounds of C02, so 100 gallons gives a ton of CO2.

You can then calculate the cost of adding capture to gas prices.

* At $200 per ton gas prices increase $2 per gallon.

* At $100 the increase is $1 per gallon.

* At $40 the increase is $0.40.

* At $20 the increase is $0.20.

It looks as if we need to get numbers into the low tens of dollars for this to be feasible on a widespread basis.

The numbers are optimistic since they don't cover the CO2 from refining and transport. That seems to be around $2 but it's somewhat hard to get accurate values.

Yea that's what I mean. It seems that cheap fast growing timber can be purchased for $20 per tonne. Dry timber is about 50% carbon and CO2 is about 30% carbon, so that means we can grow CO2 out of the atmosphere at a price of around $12 a tonne. We'll need to stack the wood somewhere but I don't think that will be terribly expensive.

The problem we're seeing in the US West is that wood has an increasing tendency to burn up. For this to work at least where I live we need to reforest using species that grow fast and are also relatively fire-resistant.

It seems people have been thinking of the fire-resistant part for a while: http://blog.davey.com/2017/08/fireproof-landscapes-with-fire....

If only they had a soft cap and let people trade credits to try to keep emissions under that cap to incentivize sequestration and efficiency innovations.

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.

~$6 per (short) ton ($0.10 per tree planted, which removes ~34 lbs of carbon per year). More here: http://shindyapin.tumblr.com/post/141034501197/climate-chang...

I've often wondered (half jokingly) if a solution to CO2 in the atmosphere is to grow trees, chop them down and bury them in disused coal mines.

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.

“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.

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 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.

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.

That is all I was trying to say

> 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

I don’t actually think climate change will kill off humanity.

I’m very optimistic about our ability to solve this and also think the sensationalism is out of control.

But even in that worse case the planet is far from dead.

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.

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.

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.

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.

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

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

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

... 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 of habitat.

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

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