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Comment by polytronic | Hacker News Reader

Plant trees

Trees eventually decay and rot. The problem is fundamentally that we're taking carbon from outside the biosphere and putting it into the biosphere. The Earth has self-regulatory mechanisms to keep that balanced with increased rock weathering going against constant levels of volcanic CO2 emissions but that solves the issue on the order of 10,000 years and trees don't last nearly that long. Plus, growing forests only absorb enough carbon per square meter to offset about watt of coal power production.

Increasing the world's forest cover is worth doing for its own sake, on biodiversity grounds, but its at best a small part of the solution to global warming.

Trees eventually decay and rot.

Not if they keep growing, which if there's plenty of CO2 to feed them, they will.

https://news.ycombinator.com/item?id=27876366

Can we plant a ton of trees and every twenty years (or whatever) cut them all down and throw them in a pit, lake, or ocean?

If they're under water they'll probably decay to methane instead of CO2 which is even worse. If you can put them somewhere dry, though, that might work. Bury them in the dessert maybe?

It has been suggested. Compress gigatons of them them to make something that won't float, and dump the result in a deep mid-ocean trench.

If carbon-free energy were money-free...

My third grade idea for trapping CO2 was to fill upside down buckets with gas and put them push them to the bottom of the ocean. The pressure would eventually compress the gas into a solid, so it would sink and remain there.

I'm still accepting funding in the from of rare stamps.

Do decay and rot, as processes, capture carbon? (I mean that I do not know)

You've gotten good answers, but allow me to expand with an eye towards a Cunningham's law situation. We have to address "how did all that carbon get underground in the first place?" I can't tell you much about oil, but coal is buried trees. They buried because there were not yet microorganisms that could break them down. So atmospheric carbon ended up underground due to the extraordinary circumstance of 1) there were tons of trees 2) the trees died 3) the trees could not decompose, so their carbon ended up buried then subjected to geological processes that turned them into a kind of rock. This takes the thick, CO2 and O2 rich atmosphere that gave us 3 foot wide dragonflies (which, honestly, pretty cool), and turns it into the one where we can live now. This process will never happen again, because now trees can break down.

If you wanted to zoom out and squint and get a little biblical, this is a Garden of Eden situation. There was an atmosphere that could not support our lives. There was a perfect mix of things at the same time to change that atmosphere into the one in which humans flourished. It was something too powerful we'd never be able to replicate ourselves. All we had to do was not exploit buried hydrocarbons. But we've instead made a race to dump as much carbon in the atmosphere as possible, it would seem. And now the comfortable world we live in will doom us to live outside of paradise.

No, they release the stored carbon from the tree in various cycles.

Unless you're doing deep carbon extraction, nature is pretty well carbon neutral. A forest of some given density, over time, will remain carbon neutral. If it gets thicker, the carbon captured is more, but it's also more prone to fires (which obviously then release that carbon).

Nature is circular. Any "waste" from one process is an input into another process. It's humans that think in linear "Resources into products into waste" ways.

Carbon is fungible, so trees will consume carbon emitted by any source. So in equilibrium the carbon consumed by trees and other sources will be equal to carbon emitted by decaying trees, or wildfires, or any other source, whether man made, or coming from a comet or volcano. To the trees, it's all food.

But outside equilibrium, the forest canopy will expand until equilibrium is reached, or the forest canopy will shrink until equilibrium is reached. You will also see more hungry plant life supported in environments with more carbon again until starvation levels are reached.

It is like any other kind of food. We can think of food as sequestered in the living bodies of a population, with deaths matched by births, a constant amount is sequestered. But increase food and population goes up until starvation levels are reached and now more is sequestered. Decrease food and population falls so less is sequestered. It doesn't matter where the food comes from. Currently 20% of the earth's carbon is sequestered in plant biomass. This is why various carbon offset programs do include increasing forests as a legitimate offset, but the land has to be allocated to the forest in perpetuity. It's not like you can grow 10 trees, the point is to support a bigger forest where there are 10 more trees permanently.

Thus nature regulates carbon levels at those altitudes that trees can feed from. I have no knowledge about equilibrating mechanisms in the atmosphere as a whole, this discussion is for carbon accessible to plants.

>Unless you're doing deep carbon extraction, nature is pretty well carbon neutral. A forest of some given density, over time, will remain carbon neutral. If it gets thicker, the carbon captured is more, but it's also more prone to fires (which obviously then release that carbon).

No, you can get it to sequester carbon if you plant trees (or other plant matter), harvest it, convert it to charcoal, then spread that around. Apparently in that form (biochar) it stays sequestered for a few thousand years: https://en.wikipedia.org/wiki/Biochar

Yes, but that's neither geological scale times, nor something nature does. I can make a forest sequester carbon if I dig big holes and bury trees in them, but that's not a particularly natural process either.

Left alone, nature's cycles are mostly carbon neutral.

I am not a scientist but I don't think that's right. A decay and rot situation should put some amount of carbon in the ground. Where else would all the peat that formed coal have come from otherwise?

Obviously violent combustion will put a great percentage in the air, but I don't see a strong reason to believe that a rotting tree trunk will completely put carbon in the air and none of it in the ground.

Thats a good question!

All the carbon that makes up most of the mass of plant is from the CO2 in the air. Decay and rot release whatever carbon was captured back into the air.

The same way the food you eat turns to CO2 you breathe out but due to fungi and bacteria.

If we can increase forest cover, yes. But also, bury trees and plant new ones in their place.

Diversity in tactics will be necessary, and trees will not be fast enough. We need this carbon gone by 2050, that is drastically short timelines.

Regardless of Ethiopia or #TeamTrees, trees are not fast or permanent enough to sequester anything substantial.

Not all tactics will be equally effective. It's worth investing in the approach(es) that are most effective in proof-of-concepts trial runs guided by a first principles perspective. That's how to maximize change. GMO kelp and phythoplankton for oceanic BECCS seem like the leading candidates.

Is there any reason we don't genetically modify trees so that they grow huge? GMOs are some of our most advanced technologies, yet it seems no one has thought to modify trees to grow more.

Wildfires

In the long run this is carbon neutral because more trees will grow.

That's a rosy, invalid assumption and equivocation. Climate drying, and effectively biome changes in the direction of desertification, across much of western North America and other parts of the world due to climate change isn't conducive to replacing biomass lost to forest fires caused by multi-year droughts.

I'm assuming this is done as a part of an effort to actually regrow and maintain forests as natural carbon sinks, and not some weird thing where trees are grown in the desert.

TeamTrees vs REALITY!!

https://youtu.be/gqht2bIQXIY

Doing "something" is futile if it's ineffective, not permanent, and not scalable.

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