[mdavis6890]

I still do not understand how any human-developed carbon capture techniques is going to be better or more efficient than just planting a tree. A (living, growing) tree can capture quite a lot of carbon for almost no cost, directly from the atmosphere. More generally, vegetation biomass growth is carbon (and hydrogen) capture in action on planetary scale - almost for free.

[jjk166]

Trees capture carbon, but they don't sequester it. You need additional steps to prevent the biomass from decomposing. This isn't too hard, generally just burying plant material below enough earth will do the trick, but it's a substantial expense at scale.

And scale is really the issue. All the world's forests combined currently absorb about 20% of CO2 humans currently emit. To go neutral, you're looking at planting around 12 trillion trees. Worse still, about 30% of Earth's land surface area are already covered by forests, so you can't simply expand the forests to get the required carbon capture.

The only realistic way to achieve 100% carbon capture by biological means would be to seed algae blooms in the ocean, which for short term carbon uptake would work pretty well, but when that algae dies it is way harder to prevent it from decomposing, meaning you don't get long term sequestration. Further, you are talking about terraforming-level changes to marine environments all over the world. Beyond the catastrophic effects that can have on other species, the full effects of what that might do to us are impossible to fully predict.

Artificial carbon capture might have higher capital costs since the equipment is not self replicating, but it can be orders of magnitude more efficient in terms of energy, CO2 capture rate, and land use requirement.

[runarberg]

Can’t you just use the wood for something instead? I’ve seen a lot of innovative use for wood in large construction projects. For example, there was a recent proposal to replace the West Seattle bridge with a timber through arch bridge, and timber skyscrapers are apparently now a thing. This is especially true since concrete is a really polluting industry, and finding ways to use less cement is a pretty solid climate action.

[jjk166]

There simply isn't that much demand for wood. It is already used extensively as a building material, but only a tiny fraction of the world's forests are used for lumber production. Indeed lumber production doesn't even make up a large portion of trees that humans clear. For context 12 trillion trees of lumber would be enough to build 100 to 500 two story residential homes per human being on earth.

Again, this doesn't really matter since this wouldn't physically fit on the planet.

[stevage]

Not much demand? Prices for timber have skyrocketed lately, demand is enormous.

[jjk166]

The price of lumber is currently the same as it was in 2018. The price spike during the pandemic was due to reduced saw mill capacity and subsequent panic buying. At no point in time were we running low on trees.

We would need to consume timber at about 1000 times the current rate for timber demand to equal the necessary tree planting rate for carbon capture.

[runarberg]

Do you think there is any room for induced demand of timber? Like in 40 years we cut down a bunch of trees to sequester the carbon and people find new innovative things to do with the lumber, not just in construction but also in material science, packaging, etc.

I’m thinking about salt as an example. It is a by-product of many industries and cost have gone down a lot since the industrial revolution. I’m imagining that today’s salt demand is heftily induced as a result. I mean, it is cheap enough to spray on highways to melt the ice.

[MichaelZuo]

Agree, it's such a bizarre statement that their other opinions seem suspect.

[brnt]

Some say concrete should be replaced wholesale with wood (CLT). I imagine that would make a dent?

[jjk166]

Every year humans use approximately 9 Billion tons of concrete. The mass of 12 Trillion trees is approximately 1100 years worth of concrete. This much lumber would need to be used every 200 years or so.

[runarberg]

I see, so we are never going to be able to use trees to capture our current current CO2 emissions. However would it be possible to use trees (and other photosynthetic organisms) to capture our historic emissions in a mass global atmospheric cleanup efforts, after we’ve mostly gone carbon neutral? Or is that also like a 1000 year effort even if we became carbon neutral tomorrow?

[ninju]

Of course the creation of concrete has its own environmental impact

https://psci.princeton.edu/tips/2020/11/3/cement-and-concret...

[krallja]

There isn’t enough wood used, by several orders of magnitude.

[njarboe]

Many trees live for over 500 years (Redwoods, Cedars, Douglar Fir, Oaks, etc.). They can be part of the solution of keeping CO2 levels down while our energy system is de-carbonized. Go ahead and plant trees. They are great in many other ways also.

[jjk166]

Again, the real deal breaker is needing 1.6 earths worth of land. No one is saying planting trees is a bad thing, but there is no escaping the need for other methods of carbon capture.

Trees tend to stop growing after about 150 years, so trees left standing longer than that will delay releasing the CO2 they've already captured, but will not continue to capture carbon. Indeed you probably want to cull trees before their growth rates start to decline around the 100 year mark to maximize your carbon capture rate.

[robocat]

Do you have a link that summarises the “FAQ” answers you have made?

[adregan]

If you don't mind videos, these are a pretty good explainer: https://www.youtube.com/playlist?list=PLxlgF_EchG56YnW2bLDk-...

[kiliantics]

How are you arriving at the 12 trillion trees number? I think there are some less obvious ways that trees can capture more carbon. For instance, trees build soil over time. Much of the deforested land in the world has had its topsoil washed away without trees to hold it in place. That soil is also a form of captured carbon.

[jjk166]

Earth currently has about 3 trillion trees, this population captures about 20% of current human co2 emissions (which includes soil creation). To get to 100%, you need 5 times as many trees, which means increasing the current population by 12 trillion.

Of course this is a crude estimate, not all trees are equal and planting trees in such large numbers would undoubtedly have other effects, but no matter what you are talking about an absurdly large number.

[stevage]

Soil carbon sequestration is definitely well known.

Eg https://carbonfarmersofaustralia.com.au/carbon-farming/soil-...

[ch4s3]

Photosynthesis is pretty inefficient and trees release the CO2 when they rot, so they aren’t great for long term storage. At certain phases of growth, forests are actually carbon positive. DAC can bind carbon to rock or pump it deep underground where it will stay potentially forever(on any meaningful human timescale). You can also directly account for the tons of CO2 removed by DAC which makes it more used for carbon trading schemes that financially incentivize capture.

[njarboe]

Many trees, if they are not cut down, grow for hundreds of years. And trees are just great to have around in general.

[ch4s3]

That's true, but they don't fix any more carbon after they're fully grown. I'm not against tree planting, but it's probably a bit oversold as a solution. Kelp probably presents a more interesting opportunity.

[njarboe]

I know at least conifer trees are never "fully grown". I imagine it is the same for deciduous trees. Trees continue to add wood to there structure every year. You count the tree rings to know its age. A 500 year old redwood, cedar, or Douglas fir can be 15 or more feet in diameter. That is a lot of wood. Unlike what many people thought, studies have found that the volume of wood added to trees in a mature forest is similar to a young one.

[photochemsyn]

I think the example to look at is biological nitrogen fixation, vs. the Haber-Bosch process, which operates at high pressures and temperatures and therefore has a small area footprint. You can do biological nitrogen fixation with legume (pea, bean) crops in symbiosis with nitrogen-fixing bacteria nodules, and then compost the crop to generate a nitrogen-rich fertilizer, but this means devoting large fields to the process. The Haber-Bosch process in contrast can produce much greater amounts of pure ammonia in a single location.

Haber-Bosch traditionally has relied on large fossil fuel inputs, but it's possible to get the hydrogen from the process via hydrolysis of water, powered by renewable energy (or nuclear), and use electricity instead of fossil fuels to run the high-temperature, high-pressure catalytic reaction (H2 + N2 -> NH3).

The same arguments apply to carbon capture and fixation: you can do it in an industrial setting, for example the North African desert (which doesn't support much plant growth), you could use seawater as the hydrogen source and plentiful sunlight and PV/concentrated thermal for electricity to drive the carbon capture (fans etc.) and the analogous version of Haber-Bosch (Fischer-Tropsch) for CO2 - CO + H2 -> hydrocarbons.

[kitkat_new]

you only can plant so much trees, with no guarantee that they even will grow old; currently we do everything but increase tree "population", because instead of going vegan we have ever rising meat consumption demanding more and more land for agriculture.

Even restoring all the forests that have existed pre the industrialization will not help much, because it only resets a small part of the emissions. All fossil fuel burned is still in the atmosphere, likewise increasingly more methane.

Additionally, it's easily used for green washing.

Plant trees -> Yai carbon is offset, can emit like before; then trees are cut down, burn or don't even grow, and the next company can plant trees at the same land

[hbossy]

There's more trees in Europe than in roman times.

[L_226]

Because trees cannot be grown just anywhere, they require specific [land, water, nutrient] conditions that also happen to be the same things that are already under pressure from our civilisation. This is caused by things like extensive monocrop agriculture, grazing etc. Furthermore, trees do not necessarily sequester carbon beyond their lifespan - the sequestration is an additional process that may or may not occur naturally. Think of old trees dying, falling down and decomposing vs old trees dying and being covered by mud.

[NegativeLatency]

I read The Ministry for the Future recently and it was largely centered around the idea of a Carbon Coin (money based on how much carbon you sequestered or didn't emit). https://en.wikipedia.org/wiki/The_Ministry_for_the_Future

Would be interesting to try it IRL, as you'd potentially have lots of different approaches being tried vs some kind of top down solutions

[bequanna]

From your source:

> Specifically, a coordinated global round of unconventional quantitative easing through the issuance of a complementary currency, called the carbon coin, to be issued in proportion to the mass of carbon that is mitigated.

That is just nuts.

The result would be like every other time money is printed: Wealth flows to those that know how to game the system while inflation erodes the wealth and income of normal people.

[nanomonkey]

Totally agree, woody biomass is being under utilizes these days. Gasification produces syngas which can be used to produce heat and electricity when wind and solar aren't producing. The biochar that is left over can be introduced into the soil to improve it's nutrient and bio-activity (terrapreta). This is essentially reverse mining of carbon and is stable for thousands of years in the soil. It also keeps the biomass from producing greenhouse gases from decomposition.

Beyond trees, we should also be growing algae and other plant mater to sequester more carbon and produce oils, sugars and other useful ingredients for our lives. This can be done at sea or in areas where water is scarce and normal vegetation grows poorly.

[samatman]

In much the same way that a solar panel is more efficient than a tree at capturing energy from the Sun.

Or a jet is more efficient than a blackpoll warbler at migrating across the Atlantic.

Or a knife is more effective than a claw at cutting through things.

In a world full of examples, why should carbon capture be any different?

Trees weren't designed to capture carbon, so there's every reason to think something which is can do a better job.

[midoridensha]

>Trees weren't designed to capture carbon, so there's every reason to think something which is can do a better job.

They weren't, but just like jets and knives require a lot of human labor to manufacture in mass quantities, any artificial solutions are likely to be the same for a while. Trees, on the other hand, are fully automatic, self-replicating machines that require almost no human labor (perhaps for initial plantings in a place where they don't already grow, or don't grow in sufficient quantities with their natural self-replication). Basically, if you plant a bunch of tree saplings somewhere suitable, you can leave it alone for 300 years and come back and find a forest.

[elif]

Considering that most of the energy supply is currently going into brake pads, designing an efficient regen braking system is quite reasonable.

Once we are on renewable energy, the efficiency argument will make it undeniably efficient.

This drought is teaching us that "just grow a tree" is not always viable, and the resulting water crisis is also begging the question "with who's water?"

[fgeiger]

Who's water? Planting trees usually helps to prevent droughts because they keep water in the local climate with effects like shading the ground and containing rainwater (instead of the rain just washing down the next river). I'm that sense watering them is a good investment.

[elif]

If you look at actual reforestation projects in the actual world, putting a seedling in the soil with a mesh fence is about 5% of the effort.

Irrigation is about 95%.

[TremendousJudge]

Or at least create the hydrocarbons in a factory, sucking the carbon from the atmosphere, and using energy from renewable sources or something of the sort. This would be carbon neutral at least, and still allows liquid fuels to be used. I have never seen anybody invest into this research. Somebody please correct me if I'm mistaken here.

[noplsbecivil]

Not quite there yet, but https://solugen.com/ are trying

[tunesmith]

It's not either-or. Planting more trees is necessary but not sufficient.