Bioenergy Plantations to Drive Down CO2 Levels

[BillTre]

Since it seems unlikely (to me) that current approaches will very rapidly stop the increase in CO₂ levels driving climate change, alternative approaches involving removing CO₂ from the atmosphere are being explored.
Here is a link to a Science mag news article about using plantations to do carbon sequestration.
It discusses several different approaches but focuses on growing plants to take CO₂ out of the atmosphere, burning them for power, and then stashing the CO₂ underground.

 

[phyzguy]

The problem with these plans is the scale required. The article estimates that to do what they are suggesting requires a 50% increase in cultivated land to grow the plants that will pull the CO2 out of the atmosphere. This article estimates that the current world agriculture industry is a $2.4T/year industry and employs a billion people. So you need to marshal an effort that will cost $1.2T/year and require 500 million people, not to mention finding a land area the size of Australia that is not already spoken for to grow the crops and building the power plants to burn the plants and sequester the CO2, a technology that doesn't really exist today. It just seems beyond the realm of the possible to do these things.

 

[Tom.G]

...and sequester the CO2, a technology that doesn't really exist today.

Quoting from http://www.sciencemag.org/news/2016/06/underground-injections-turn-carbon-dioxide-stone

After about a year and a half, the pump inside a monitoring well kept breaking down. Frustrated, engineers hauled up the pump and found that it was coated with white and green scale. Tests identified it as calcite, bearing the heavy carbon tracer that marked it as a product of carbonation. Measurements of dissolved carbon in the groundwater suggested that more than 95% of the injected carbon had already been converted into calcite and other minerals. “It was a huge surprise that the carbonation happened so fast,” (emphasis added)

 

[dabunting]

Tree Carbon Sequestering

First, consider a square acre of fully mature forest a thousand years old. We could remove and measure the carbon in all substances, trees and other plants with their roots, all dead and decaying substances on and under the ground. Then we could make the same measurement of an identical acre 100 years older, at 1,100 years old. As both acres were fully mature, the carbon content of the two would be the same. The acre has no way to store carbon except in its living and dead-decaying organic matter. The acre is fully mature and static in carbon content. Carbon taken from the air by the mature vegetation and other growing life is equal to carbon released by dead decomposing trees and other forest materials on the ground. The acre stores no carbon.

Most of the carbon contained in the acre is in the large, heavy tree stems. A way to stop most of the reverse damaging carbon-into-air decomposition, and to secure and sequester most of the carbon contained in the acre is to cut these stems into conveniently-storable shapes, and to store them in dry conditions, under roofs and out of contact with the ground.

An efficient way to accomplish this, without wasting valuable dry storage space, to sequester permanently most of the carbon contained in the acre, is to store the wood in a useful way by using it in the construction of the dry spaces, homes and buildings.

An additional benefit is that, when the trees have been removed, the acre can be replanted so that the new growing forest is again strongly removing carbon from the air in the growth of its trees and other forest substances, with almost none of the damaging reverse carbon-into-air decomposition occurring. The acre is no longer static and carbon-neutral, but dynamically removing carbon.

 

[Nugatory]

The acre is fully mature and static in carbon content. Carbon taken from the air by the mature vegetation and other growing life is equal to carbon released by dead decomposing trees and other forest materials on the ground. The acre stores no carbon.

That's not quite right. The amount of carbon coming in is (by hypothesis) equal to the amount of carbon going out so the system is in equilibrium and the amount of carbon it contains doesn't change; but that amount may be very large, and it certainly counts as stored carbon. If anything happens to disturb the equilibrium that stored carbon could be released. For example...

A way to stop most of the reverse damaging carbon-into-air decomposition... is to cut these stems into conveniently-storable shapes, ... to store the wood in a useful way by using it in the construction of the dry spaces, homes and buildings.

When a tree is cut down, a surprisingly small amount of it turns into lumber. There's bark, milling waste, the stump and root system, and a huge amount of slash ("slash" is the term for the leaves, twigs, and branches too small to use - essentially the entire canopy ends up as slash), all of which contains carbon that goes back into the atmosphere. Thus, cutting the trees turns the acre into a net carbon emitter for many years to come.

That's not to say that the idea of sequestering carbon in milled lumber suitable for building construction is necessarily hopeless, but there's a fair amount of quantitative thinking needed to see if we're even in the right order of magnitude. One possible starting point: In round numbers you can get about one thousand board feet per year out of an acre of softwood.

 

[BillTre]

a huge amount of slash ("slash" is the term for the leaves, twigs, and branches too small to use - essentially the entire canopy ends up as slash), all of which contains carbon that goes back into the atmosphere.

Sadly, at least in Oregon (formerly the home of many huge old growth trees), almost all of the slash is burned in the field after the lumber containing parts are removed. Straight to atmospheric CO₂.

They do replant (with seedlings) though. However, seedlings won't fix too much carbon for several years though.
The article talks about poplars, which grow fast but don't have particularly dense wood (not so much carbon?).

 

[Rive]

It discusses several different approaches...

I'm happy to see that ocean fertilization is mentioned. What's missing is that it is more or less the only option, which has enough space available and also: it is a process which is not expected to stop merely at the point of 'let the CO2 sink'.

Regarding forest - instead of such plans I would be more happy to see old forest properly protected first.

 

[russ_watters]

Here is a link to a Science mag news article about using plantations to do carbon sequestration.
It discusses several different approaches but focuses on growing plants to take CO₂ out of the atmosphere, burning them for power, and then stashing the CO₂ underground.

There's often a critical and ridiculously difficult - and often totally independent - step tossed in as if it were trivial and secondary. If we could do carbon sequestration, we would already.

 

[bhobba]

Regarding forest - instead of such plans I would be more happy to see old forest properly protected first.

So would I. Trouble is a lot happens in ways that can't be controlled eg the Brazilian Amazon forest deforestation. Its done illegally either due to lack of resources from the Brazilian authorities or they are complicit with it (eg bribed). That's the huge problem with global warming - how, in practical terms, can we actually do something about it. I am personally very pessimistic and side with Brian Cox who thinks the politics of doing anything actually meaningful is basically impossible. Of course that does not mean we don't do the things we can do - that will delay catastrophe hopefully until technological advances allow us to actually tackle it. I am also so pessimistic I agree with Hawking that the human race will survive only 100 years unless we colonize off world.

Thanks
Bill

 

[BillTre]

If we could do carbon sequestration, we would already.

What about post #3?

Quoting from http://www.sciencemag.org/news/2016/06/underground-injections-turn-carbon-dioxide-stone

After about a year and a half, the pump inside a monitoring well kept breaking down. Frustrated, engineers hauled up the pump and found that it was coated with white and green scale. Tests identified it as calcite, bearing the heavy carbon tracer that marked it as a product of carbonation. Measurements of dissolved carbon in the groundwater suggested that more than 95% of the injected carbon had already been converted into calcite and other minerals. “It was a huge surprise that the carbonation happened so fast,” (emphasis added)

 

[russ_watters]

What about post #3?

The first word of @Tom G 's link is "Researchers". They are researching the technology, trying to develop it. Hence I concur with @phyzguy ; that means the technology to actually implement it does not exist yet ("researchers" are also building "working" fusion reactors, but don't expect to see one of those supplying you power anytime soon either).

Either way though, you're looking at this from the wrong angle: we emit billions of tons of CO2 from coal plants. You don't have to build a new grass plantation power plant to make as big impact with sequestration if it can be done; you could just attach it to an existing power plant. That it isn't being done - despite harsh/putative regulations - tells us that it is a difficult thing to do.

 

[OCR]

You don't have to build a new grass plantation power plant to make as big impact with sequestration if it can be done; you could just attach it to an existing power plant.

Yes, I've been wondering about that very same scenario since I started reading this thread, if pumping CO₂ into the ground worked as claimed... why not ?

...just attach it to an existing power plant.

It discusses several different approaches but focuses on growing plants to take CO₂ out of the atmosphere, burning them for power, and then stashing the CO₂ underground.

It just seems beyond the realm of the possible to do these things.

IMO, it would be a total and absolutely, counter productive, logistical nightmare... !

BTW... .

despite harsh/putative regulations

I think I would have used the word... punitive ! .

 

[Tom.G]

BTW... .
I think I would have used the word... punitive !

For those that have a passing familiarity with large construction projects, putative is at least as accurate!

 

[OCR]

I also disagree with this statement, to the extreme... !

When a tree is cut down, a surprisingly small amount of it turns into lumber.

Carry on...

 

[russ_watters]

I think I would have used the word... punitive ! .

Yep: engineer, not a writer.