Geoengineering

So. Science can fix anything, right? Only if we have lots of time and money. And grad students that function as indentured servants in a pyramid scheme to get tenure.

Back to the point. The truth is that science can't fix everything on short time scales. Climate is one of them. Geoengineering can help to a degree, but it will only get us part of the way there to avoid the worst consequences of climate change. Let's discuss some.

White roofs, white roads, white buildings.

Two articles back, we discussed albedo, or reflecting sunlight. Ice reflects 90%, water reflects 90%. Whatever is reflected tends to go to space and not stay in the Earth system and warm it up. In fact, whatever is absorbed then gets in the greenhouse trapping loop, warming up the Earth a good bit. Dark surfaces (our roofs, our roads, most of our buildings) reflect little and absorb a lot. So, paint them all white, and more light is reflected. Excellent!

"But Jason," you say, "Cities are only a small percentage of land area. How could this possibly help? I mean, the rest of the Earth will still absorb just as much heat. Right?"

And to you I say, "Excellent, sir! That is true. Making all our stuff white won't do much for the overall heat budget of the Earth. I am so proud of you for reading most of my website so you quickly figure stuff like that out."

So what does it do?

 

The heat island effect is based on the fact that cities are covered in dark buildings and pavement, and have a very low albedo, so they absorb heat

Cities are fucking warm. They suffer from this thing called the "heat island effect." That is a fancy way of saying that they are so dark, they absorb the sunlight and are easily 10 degrees F (around 5 degrees C) warmer than they should be. Turn everything white, and you can cool the city. This will actually have a very large effect on how hard our AC units have to work in the summer. Imagine if your city was suddenly 10 degrees F cooler. How sweet would that be? I posit that it would be pretty rad.

This one seems to help a bit, but we will still be using tons of energy and producing CO2 in all other ways. Moreover, it won't solve the problem of the agriculture, ice caps, and acidifying ocean.

Putting CO2 in the ground

There are two ideas of sequestering CO2 in the ground. The first is capturing it at the source. Like power plants. This sounds like an easy idea, but the first problem is the energy it takes to capture it. Thermal power plants take in atmospheric air. Which is 78% nitrogen, and 21% O2. Even if all the O2 were converted to CO2, what comes out of the power plant stack is still 78% nitrogen. Separating the two to store the CO2 takes more energy. In fact, the power plant is roughly 30% less efficient. So it needs to burn a lot more coal or natural gas to produce the same amount of power, and will cost a lot more to build. And any fancy idea you have to get around this 30% efficiency hit won't work. No matter what, you either have to pre-concentrate O2 to get a pure stream of CO2 on the other side, or separate the CO2 on the emission side.

The next problem is where to store it once you get it. Gases like to leak out of things. Some companies are trying to store the CO2 underground, much like petroleum is stored underground in a lot of places. This is why you need to separate it from the nitrogen in the air. There just isn't enough space to store both the CO2 and the nitrogen, and also it is expensive to pump stuff underground. Another issue is that it is unclear how long storing CO2 will last in the ground, since it more or less needs to be done indefininately.

Finally, since 35% of our energy use is from cars driving down the road, and it is impossible to capture that CO2. So Carbon Capture and Storage (CCS) from the source still won't do everything we need.

Direct Capture
The next idea is to capture CO2 directly from the air. We have increased CO2 in the atmosphere from 280 parts per million (.028%) 400ppm. The idea of direct capture is to do the opposite. Draw down the CO2 and then store it somewhere. Some might suggest we store it in trees, but that is an awful lot of trees, and unless we bury them trees somewhere underground, they are just gonna get consumed by bacteria and become CO2 again. Other options are to mechanically and chemically separate CO2 from the air, and them store it underground as above. This is very expensive. It might work in the future, but for now it won't.

The bonus of this, if it ever works, is that it is the best way to reverse our issues from an engineering standpoint. We can turn back the clock.

Stratospheric Injection

Injecting small sulfur or other particles into the atmosphere cools the entire globe by reflecting some small portion of sunlight before it hits the rest of the Earth. We know this cause when mountains like Pinatubo and St. Helens explode, they launch particles into the stratosphere and we get a cold year.

SO2 increase in the stratosphere by exploding volcano

Some people have suggested that we could do this. Just inject stuff into the stratosphere to reflect sunlight. The problem? It turns out that everything small enough to cause the proper scattering just happens to be the right size to promote adsorption of water particles. Which then allows for rapid recycling of CFCs in the stratosphere.

"But Jason," you say, "I thought recycling was good!"

Recycling plastics is good. Stratospheric recycling of CFCs is bad. Cause what happens is a CFC reacts with ozone, breaking it apart, wrecking the ozone layer, and then usually is all like, "Man, I am exhausted from catalyzing that reaction, I am gonna take a break." But that water that adsorbed onto our reflective particle provides an excellent place for it to re-radicalize. Which means it is ready to take out another Ozone particle. That's right, our CFC goes to chill out on some water droplets, effectively taking a restful timeout at a pool, and gets ready for work again destroying the ozone layer.

Let's pull this all back together. We try to put stuff in the upper stratosphere, if could make CFCs more effective at destroying the ozone layer, and then we are all screwed in a much much larger way than climate change. Cause the ozone layer is what protects us from getting fried by a lot of UV rays.

Here's where things get fun. Imagine you are a small country of 1 million people living on an island. And that island is going to get inundated with water in 20 years unless climate change is reversed. You don't give a damn about a chance of destroying the ozone layer. You only care about saving your people and your country. Stratospheric injection isn't exactly nuclear science. We aren't going to have rogue nations stumbling through how to do this, and failing all the time.

I'll leave you to ponder what all that means, cause it is more fun that way, and we are already at 1200 words.

The upshot of this is that it also fails to solve the acidifying of the ocean, we don't know how well it will work, and we don't know what will go wrong.

Solar Reflector

Another idea is to put huge mirrors in space and reflect a chunk of the sunlight coming in. This could work. Wasn't this a plot in some Bond movie, though? Also, it would be mad expensive. Probably much more expensive than some other options. And much like the option directly above, we still acidify the ocean.

Review

Hokay, so. Most of the technologies for fixing our problem don't exist, don't work, are too expensive, or could kill us all. And if they do work in the future, they won't solve all the problems we are creating. Even the one that does solve all the problems, direct capture from the atmosphere, won't do crap for our plight if we rely on that alone. As a species, we can easily outstrip any CO2 removal measures just by burning more things. Even if after rigorous testing proved all these work, we would need to some combination together to get anywhere. And even with that, we need to reduce the continued growth of emissions worldwide, otherwise no science or engineering solution will stop climate change.

Depressing, eh?

Thanks for reading,

- Jason Munster

2 thoughts on “Geoengineering

  1. Hey Jason, I know you don't usually put a ton of references, etc, in your blog, but some more info about the stratospheric injection of sulfur is definitely needed. It definitely does reflect sunlight and it definitely does also accelerate ozone damage, but my impression is that the reflection (and associated cooling) is dramatic, while the ozone damage is small. Thus the ozone damage would be an unpleasant but very small side effect of offsetting lots of global warming. If you've got some references to back up your case that'd be great - I'm not an expert on this so I'm just relying on what I've heard from others .

    Thanks for another post!

    • In this case, the information came from a public PhD defense in my department. I don't think the work is published yet. If you check out the recent Science article that came from my group, the chemistry is there. Just make the rate of the reaction much faster because this chemistry happens faster on water that is adsorbed to a particle.

      I've not seen David Keith's talk on stratospheric injection, however. Have you, by any chance?

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