There is not one solution for Global Warming and CO2 emissions. No silver bullet, just as in software. This is one more tool, which needs to be used when appropriate. But we also need better legislation, technological improvements, and changes in consumption behavior, locally and worldwide. If we look at each of those things and do the math, the answer will be "it's not enough" or "it's too expensive". We mustn't let that be a showstopper. Of course some solutions are really not viable at all and should be ignored in favor of others, but every solution that helps enough (for some definition of enough) needs to be pursued.

The year is 21XX. Multi-story "tree towers" pierce the skyline in every direction, competing for vertical supremacy with even the tallest of skyscrapers. Solar and other renewable energy sources provide the lighting necessary for the unexposed levels.

Grow 100 foot trees, fell them into central points into a teepee like structure. Move soil to the points plant a new tree on top.

Not every year. Given the article's assertion of the 103 tons per acre per year, your Alaska of Empress trees would do it until they all die and presumably those forests will be maintained into perpetuity.

When the tree dies, it will release 99% of the stored carbon back to the atmosphere. Unless you bury the tree in an anaerobic environment or treat it in some other way, the tree is just a time-delayed release mechanism.

New forest can store a buffer in perpetuity, e.g., a new trillion trees can store 133 Gt. But current emissions are > 40 Gt/year, so this is < 4 years worth of emissions.

> When the tree dies, it will release 99% of the stored carbon back to the atmosphere.

It's not the tree which does that. It's the organisms consuming the tree during the decomposition process which do that. And that doesn't happen all at once. Indeed, if you grow another tree then you're likely to still be net-positive.

If you use the tree for other purposes -- construction, for example. Or burning for energy production -- then it becomes a useful part of the lifecycle.

> Or burning for energy production

Doesn't that just release the C02 again? Construction purposes might help, or any other way of sequestering.

Yes, but its net-zero carbon, so still an improvement over using fossil fuels.

Net-zero CO2.

Probably other factors are small, but hard to predict (particulates, volatile chemicals, other effects of growth). Might be positive or negative.

Fair, so that implies it doesn't really help, but at least isn't actively making things worse.

Makes me wonder if in the future the solution will be to create synthetic crude and pump it back into the ground.

Or just:

>Once the trees reach maturity, farmers harvest their wood for use in houses or musical instruments

as in the article. You could make chunky log cabin type buildings to use more. I'd quite like a log mansion.

Maybe this is where the oil came from In the first place. A desperate attempt to dump co2 by a doomed civilisation in the deep past. Obviously not, but could make a good short story :)

It definitely seems like the ideal solution is bacterial sequestration of carbon into some inert, non-toxic, storable chemical.

Make charcoal and then bury it

There is a guy here who cuts them down and regrows them from the stumps, selling the timber and feeding stock with the leaves and small branches. Presumably this increases the carbon capture.

https://thisnzlife.co.nz/how-a-small-waikato-farm-harnesses-...

Ironically the stored CO2 destroyed the 'civilisation' that fixed it in the first place

The carbon stored in a tree is proportional to its weight, about half its dry weight is carbon [https://scied.ucar.edu/sites/default/files/images/long-conte...].

Also in all those discussions of processes(!) I find people even here seem to be looking at points in time only, and usually at the start of the process. That also includes the issue of looking at just one tree instead of a forest. When you look at the whole system individual tree life cycle doesn't matter any more. Some trees grow old and die or are harvested (what happens?), others grow in their place, overall the forest remains at a pretty stable and fixed weight. Unless you find trees that keep growing for miles and miles higher for thousands of years.

Look at total biomass, not at tree life cycles! The equations at that point of a mature forest are balanced. The whole forest stores a fixed amount and that's it. As long as we keep bringing carbon from very ancient forests back out of the earth, it does not matter how many forests there are. You will only get a temporary dip.

This whole thing is ridiculous: Even if we decided to bury grown trees deep underground to remove their carbon from the surface forever - why not save the huge effort (and the energy that process needs which again has to be fed somehow - with even more fossil fuels for quite some time to come) and simply leave the ancient forests where they are (deep underground)?

You can plant trees as much as you like, as long as we continue to bring up carbon from underground it is useless - apart from a temporary (small) dip. The above-ground forests will never be big enough to compensate for the below-ground forests being brought back up.

A quick search shows links and links of opinion and "studies" all about "we can store carbon underground!" Well, wait, what?? I don't get it. - it's already (down) there!! Earth did just that a long time ago! Just stop bringing it up, then you don't need to find ways to get it back down, which according to the laws of physics is a net-negative process. For the same amount somehow stored underground we need far more for the energy to do so, as long as we rely on carbon for energy (which won't change any time soon at scale across the world). And if we don't need the carbon for energy we won't bring it up any more (about three quarters of oil is used for energy or heating, an even higher share of natural gas and coal).

I really don't understand the discussion at all. It seems like a great distraction, all those studies and headlines and discussions about storing CO2 underground? For the reason mentioned. After you get it out and burn it (i.e. turned it into CO2), you will need even more of it to get the energy to get it back down where it already was to begin with. Even if we would have 100% solar/wind, the whole scenario does not sound very useful to me at the imagined scale. Even using it as temporary energy store/source for energy demand when wind/solar are not available should be done with what already is above ground, or if it involves a blow-ground cycle it should be one far smaller than the current extraction and the imagined reburying.

Having more forests is wonderful for many reasons (even though at this point vast areas are removed - https://www.livescience.com/27692-deforestation.html). However, the attention it gets as some sort of "solution" for global CO2 levels amazes me (in combination with the fact I just linked even more - stopping what we are doing would be soooo much more impactful, both destruction of current and previous forests above as well as underground).

You don't bury the trees underground to store their carbon.

You bury them in buildings. As lumber.

Replace concrete (which produces CO2) in new buildings with wood (which sequesters it) and you've tackled quite a bit of carbon emissions.

You again look only at points in time or short periods and only at individual items instead of systems. Buildings are not a final permanent storage and they are not a different storage compared to trees, they basically serve the exact same purpose if you model global CO2 storage and have pretty much the same characteristics. Nothing changes by including buildings, you could just model it as a larger forest.

Unless you add additional options by having two different items (tress + buildings), e.g. the option to stack them on top of one another, it does not matter if the carbon is stored in a tree or a building made from it. They all share the same limited surface space and you could just replace all buildings with trees in the model, or vice versa and it does not change the total storage capacity here on the surface. I refer back to everything I wrote.

You again look only at points in time or short periods and only at individual items instead of systems. Buildings are not a final permanent storage and they are not a different storage compared to trees, they basically serve the exact same purpose if you model global CO2 storage and have pretty much the same characteristics. Nothing changes by including buildings, you could just model it as a larger forest.

Unless you add additional options by having two different items (tress + buildings), e.g. the option to stack them on top of one another, it does not matter if the carbon is stored in a tree or a building made from it. They all share the same limited surface space and you could just replace all buildings with trees in the model, or vice versa and it does not change the total storage capacity here on the surface. I refer back to everything I wrote.

Maybe carbon pricing schemes will do that - shift the economics to more closely match the physics. If what you say is true, then eventually the price of dug-up carbon should roughly equal the price of digging it up, processing it, and shoving it back in storage. That should incentivize leaving it there in the first place.

well, if you convert it all to biochar (say with a 50% volume fudge factor to account for non-carbon components and packing density), you just have to stack an area the size of pennsylvania with 1 meter of biochar each year to zero emissions.

And the carbon cost of the energy it takes to convert it all to biochar?

The energy and carbon come from burning off the volatile organics from the wood. It impacts the amount of carbon sequestered but it's still a net positive.

Presumably you don’t have to harvest and replant them every year though. I’m guessing it takes them several years to get to the point that they’re full grown.

Sure, but there's also got to be some sort of diminishing return.

Definitely. We’d have to do something with all the trees every few years or whatever.

and even if this were possible, it requires a significant amount of freshwater to supply that many trees.