[umvi]

Build buildings out of wood -> Plant more trees -> build more buildings out of wood -> plant more trees, etc. This can sequester a lot of carbon over time, especially if said wood buildings are in places trees can't easily grow.

[jrace]

Cutting down trees can cause a release of stored carbon dioxide.

Structures composed of wood do not remove carbon dioxide from the atmosphere.

When old trees are cu down they should be replaced with new ones

[umvi]

> Structures composed of wood do not remove carbon dioxide from the atmosphere.

Why not? Just some napkin math here but:

Say you have three 10K kg trees. Wood is ~50% carbon, so that means they collectively contain around 15K kg of carbon. Cut them down and turn them into framing lumber and build a house. You now have a house frame with roughly 15K kg of carbon.

Now plant 3 trees where the old ones were. Once grown you have now collectively sequestered 30K kg of carbon - half of it is in the trees themselves, half in the house.

Keep doing that. After a decade you now you have 1000 houses that have each sequestered 15K kg of carbon from the atmosphere, or 15M kg of carbon.

[Pfhreak]

I think you might be holding a spherical cow.

Does your math include the carbon necessary to harvest, transport, cut the lumber? And to haul away the existing structure?

[umvi]

> Does your math include the carbon necessary to harvest, transport, cut the lumber? And to haul away the existing structure?

True. I don't know how many lbs of carbon it takes to cut down, transport, and harvest a tree. But I would hope less than 15,000 kg.

If the trade off isn't worth it, use electric machinery and transportation powered by nuclear plants.

[jrace]

A building comprised of wood does not continue to remove carbon - but if that tree continues to live it continues to remove carbon.

[toasterlovin]

Yeah, but you can plant a new tree, which will sequester carbon at a much faster rate than the mature tree it replaced.

[jrace]

yeah....but you do not need to cut down a tree to plant a new one.

[toasterlovin]

There is limited surface area on the earth where trees will grow. If you want to utilize that maximally to sequester carbon, then you need to cut down mostly grown trees (which have stopped sequestering carbon) to make room for new trees (which can sequester lots of carbon). Then, in order to prevent the carbon contained in the trees you cut down from re-entering the atmosphere, you need to use the wood in some way where it does not decompose or get burned (to build houses, basically).

[dragonwriter]

> > Structures composed of wood do not remove carbon dioxide from the atmosphere. Why not?

> Why not?

On average, does wood in structures release carbon through decay, fire, etc., faster or slower than if the wood was left in a living tree? Intuitively, I don't see any reason to expect effective sequestration.

Your analysis seems to suppose that if wood was not used to make a structure, the trees would instantly release their carbon and not be replaced, rather than continuing to grow.

[umvi]

> On average, does wood in structures release carbon through decay, fire, etc., faster or slower than if the wood was left in a living tree?

Trees don't grow at the same rate forever. They sprout up quickly and rapidly sequester carbon until they reach maturity, at which point there are diminishing returns in terms of carbon sequestration.

Treated wood is much more resistant to decay and fire than untreated wood.

> Your analysis seems to suppose that if wood was not used to make a structure, the trees would instantly release their carbon and not be replaced, rather than continuing to grow.

No, I'm saying that a mature tree sequesters carbon much more slowly than growing trees. Think about it. It's the same for animals. Babies grow like crazy and gain mass at an amazing rate. Adults... don't. I've been 150 lbs for the past 10 years. My son, however, was 6 lbs 2 years ago, 20 lbs last year, and 40 lbs this year. That means his body is locking away 20 lbs worth of matter per year.

Take a mature tree, turn it in to a building. Grow another mature tree in its spot and you've now sequestered effectively twice as much as having never turned the tree into a building. That's what I'm suggesting.

[dragonwriter]

> Take a mature tree, turn it in to a building. Grow another mature tree in its spot and you've now sequestered effectively twice as much as having never turned the tree into a building.

It takes several (in many cases 5+) decades for a tree to mature (in the sense of growth levelling off.) The average proportion of original wood building remaining after 50 years is, well, less than 100%.

Probably significantly, more than if the old tree died and fell, so you could have some net gain, but it's not going to be 100%. (And its going to be even less if you are clearing land for the building.)

[jonas21]

This has been studied pretty extensively, for example: https://www.fs.usda.gov/treesearch/pubs/38598

Some key points are:

1. Forests reach their maximum level of carbon sequestration after around 70 years. After this point, they are no longer a net carbon sink.

2. If you periodically cut down the trees, turn the wood into long-lived products (like buildings), and then replant, you can sequester more carbon.

3. Exactly how much more depends on assumptions about the length of the useful life of a building and what is done with the wood after the building reaches the end of its useful life.

4. If you're looking at net carbon emissions, you also need to consider substitution -- by using wood in a building, you're decreasing the need for other building materials like concrete and steel, which emit a lot of CO2 in their production. They model various scenarios on the paper.