Would planting trees across an earth-like planet to reduce the CO2 and produce O2, be enough to keep it in balance?

Question

An IPCC report of Oct 8, 2018 indicates - to keep the world temperature rise at or below 1.5 C, we need to reduce our CO2 emissions globally from the 2010 level by 45% by 2030, and a further 55% reduction by 2050, bringing us to zero CO2 emissions from then on.

An average tree should be able to ‘eat’ or sequester some CO2 each day. It is certainly a no-risk, low tech solution that everyone could understand and maybe even support if it worked (on this earth-like planet...)

Answer 1

Trees and other types of plants consume (eat) CO₂ during their life, but after grow and die their bodies (wood) release all they stored Carbon due putrefaction.

So, in order to permanently (or at least for a very long time), you need to store their corpses (wood) in some place and by some way that doesn't release their carbon again to the environment.

We have a perfect solution for that:

Charcoal

Charcoal is the lightweight black carbon and ash residue hydrocarbon produced by removing water and other volatile constituents from animal and vegetation substances. Charcoal is usually produced by slow pyrolysis — the heating of wood or other substances in the absence of oxygen. This process is called charcoal burning. The finished charcoal consists largely of carbon.

The advantage of using charcoal instead of just burning wood is the removal of the water and other components. [...]

Under average conditions, 100 parts of wood yield about 60 parts by volume, or 25 parts by weight, of charcoal

^{Emphasis mine.}

Charcoal is a good way to store that annoying carbon from the atmosphere. I would suggest storing that charcoal at the bottom of seas or in abandoned mines. Obviously, after chopping the tree you need to replant it, don't forget that.

Answer 2

Trees are part of the carbon cycle; they consume CO2 while growing (since they eat CO2), but they will release it when they die - either by putrefaction or combustion. So trees are only going to remove CO2 from the atmosphere if not only we plant a lot of them, but when they die new trees take its place - or in other words, we have to increase the forest area of the Earth.

Now, forests don't grow in the oceans. Nor in deserts. Nor in cities, factories, crops or pastures - in these last cases, because they are not allowed to. Actually, 23% of our CO2 emissions comes from deforestation, so it's not that no one has thought in planting trees to fight climate change - it's that they would settle for a stop in cutting them down.

Answer 3

To expand on Rekesoft's answer and Jannis' comment... after your trees are fully mature, you need to work out how to remove their stored carbon from the biosphere to/from atmosphere cycle, to prevent them turning back into CO2. Options are:

1. Chop them down, and treat the wood with toxic preservatives which will prevent things like termites and fungi eating it. Then work out where on earth you are going to put all these thousands of tons of wood. Perhaps you could fill old mine workings with it? Meanwhile, plant more trees where the old forest was.
2. Chop them down, then store the timber somewhere where there is no oxygen. This is to limit the rate of decay and to try and avoid CO2 as a byproduct. The bottom of the Black Sea, where the mud and water is anaerobic, for instance. You'll need a microbiologist to tell you how long the carbon will stay locked away, and whether the anaerobic decay products for that particular location will also be greenhouse gases (if they produce methane, for instance).
3. As for option 1, but sink them to the bottom of the sea bed over an active subduction zone and trigger a few underwater landslides to bury them in marine muds. Hopefully they will not release much carbon before geology (slowly) pulls them down into the mantle. Some of the carbon will eventually be erupted out of a volcano in the volcanic arc associated with the subduction zone, but that is on a scale of millions of years, so the carbon is effectively gone in the long term.

Answer 4

Two things to approach are:

1) How to increase capture of carbon dioxide.

• Plant trees and other plants. There are many things to consider what to plant as different plants for different climate employ different photosynthesis methods, have different speeds of growth, usefulness and ease to deal with.

Plants with C4 photosynthesis can decrease need for water some 4-5 times and use less nutrients and still produce a few times more mass to store away. Most of them are grasses, but you can harvest and store them too. There are labs working to make use of C4 in more abundant C3 plant-life.

You would want to let the mass to mostly dry before moving and storing.

2) How to decrease & prevent carbon dioxide re-emissions.

• Bury most of your harvested plant-life in mud, under sand, some old pits and mines or other unwanted depressions can be used. Dry and anaerobic conditions will prevent most decomposition and let you store carbon. Many old cities and huge structures were build on wooden foundations and stand for centuries.

• Part of the mass can be used to combat desertification, so you will increase your carbon holding capacity.

• Use wood for something instead of concrete. Or give it away as building material.

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How useful, cheap and cost effective it is?

Well planting in the free areas, when that does not damage ecosystems is good thing by me. Fighting desertification and expansion of more friendly-for-life-areas are welcome.

But to store it is a tricky thing as you do work and pay for all that to in the end get zero profit. And you will need to move a lot. So you would need to pay for it from taxes and donations. Well sometimes desperate times need desperate measures.

Answer 5

You need to hydrate more of the world. For example, in our Earth, you might hydrate the Sahara. That way, the trees replace desert rather than grasslands. Even if the trees will release the carbon dioxide back to the atmosphere, increasing the amount currently in living plants helps.

Where do you get the water? Saltwater greenhouses. Instead of clearing out rain forest to grow crops, grow crops in the greenhouses and pipe the excess fresh water into the desert. Rain forests are teeming with organic life, all of which traps some carbon.

Don't just consider trees either. We actually have more trees in the United States now than a hundred years ago. That hasn't been enough to offset increasing fossil fuel use.

Look at what produces fossil fuels. Coal was produced from peat moss in bogs. So really overhydrate your Sahara. Dying vegetation will drop to the bottom of the swamp mud and the carbon will be trapped rather than releasing into the air.

Oil comes from algae and plankton. Encouraging greater growth in the ocean can be more effective, as the dead plants sink to the bottom. Again, trapping the carbon rather than releasing it back into the atmosphere.

Answer 6

Some numbers to help you: An acre of maximum production forest (more than seedlings, less than mature trees) fixes between 1 and 2 tons of carbon a year. Certain grasses can to 3-4. Tropical forests that aren't suffering nutrient deficiencies do better than this, but also decompose faster. Both due to longer growing season.

The best grass for this right now for temperate regions seems to be switch grass. It's perennial so it reuses the roots every year. It moves most of the scarce nutrients (P, S, N, K) out of the stems and into the roots in the fall.