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Comment by erikrothoff | Hacker News Reader

Why isn't there a billion dollar reward to any person or company that comes up with a cost-effective way to capture carbon from the air and convert back to solid carbon? I'd love to understand the physics (or chemistry? maybe economy?) that prevents this from materialising.

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The thing that prevents this from materialising is that it requires energy. For the most part, we get energy from.. converting solid carbon to CO2. Unfortunately, due to 2nd law of thermodynamics, this conversion always incurs a loss of energy in the form of heat.

We can also get energy from other sources, such as solar radiation, but I think you get the gist - the most cost-effective way to carbon capture is not to release the carbon in the first place.

Whatever the solution we could find to turn CO2 into C back it would require to roughly spend as much energy as it has been already spent in the XIXth and XXth century combined burning coal or oil to go back to pre industrial level of CO2 in the atmosphere.

I'm not a physicist, but isn't the second law of thermodynamics puts a limit on what we can do with the excess energy, most of which are being absorbed by the oceans.

Besides most of the damage is already done.

  EPA: It’s as if you’re sitting in your car, in your garage, with the engine running and the door closed, and you’ve slipped into unconsciousness. And that’s it.

  McAvoy: What if someone comes and opens the door?

  EPA: You’re already dead.

  McAvoy: What if the person got there in time?

  EPA: Then you’d be saved.

  McAvoy: OK. So now what’s the CO2 equivalent of the getting there on time?

  EPA: Shutting off the car 20 years ago.

https://www.youtube.com/watch?v=6CXRaTnKDXA

Yes, we are too late.

Emissions affect the climate decades later, some 40 years later. So we're now only seeing the consequences of the emissions from the 70s-80s.

We've emitted more CO2 since the 80s to today, than the previous 150 years.

Too late for what? Yes, there are going to be more impacts. No, it won't mean the extinction of humanity or life on Earth. There still better or worse. Choose better.

If the entire world went to zero carbon emissions tomorrow, the effects would still be serious. Given that's not going to happen, the effects are likely to be catastrophic.

You're right that it won't mean the extinction of life on earth or humanity, but it might turn out to be the end of advanced human civilization if the bad end of the predictions come to pass. If there's not enough arable land left to support the human population, things will get very ugly very quickly.

I doubt it will mean the extinction of humanity, but unless a couple of miracles happen it will mean the end of our current industrial civilization.

If we had started working on this 40 years ago reaching zero emissions would be a realistic goal today, but even that is not enough now. Not only we need to reach zero emissions ASAP, but we also need strong negative emissions. And after that we need to figure out how to slow down the feedbacks (Arctic ice melting, methane, etc).

Maybe if ALL humanity was working towards those goals we would have a chance, but it's not even a priority for the vast majority of humans.

It's not really a thermodynamics problem. We're not trying to get rid of excess energy in a system, we're trying to get rid of carbon. We need to do something roughly equivalent to growing massive tropical rainforests and burying them over and over again.

Of course it's a thermodynamics problem. It takes less energy to split a hydrocarbon chain into CO2 + Water than it does to capture the CO2 out of the air and turn it back into solid carbon.

In essence, what we have to do is "all the energy output since the industrial revolution--do it again (plus then some), except this time instead of building civilization, capture co2 out of the air. And you must get all that energy from clean sources."

"Growing massive tropical rainforests" just means "inefficiently use solar energy (via photosynthesis) to bind carbon out of the air". We could do the same with solar panels and a carbon-binding chemical process.

But the issue is, again, the sheer magnitude of the problem.

We have a solution - reduce carbon/methane emissions. Why bet the bank on a technology that hasn't been invented yet? If you said to somebody with 100 billion dollars: capture as much carbon as you can. What would they do? I would just plant trees for that money. Sure, we need basic research on carbon sequestration, but we need fundamental breakthroughs to make it happen. Time, we don't have.

>We have a solution - reduce carbon/methane emissions. Why bet the bank on a technology that hasn't been invented yet?

Unfortunately we haven't invented the technology to implement your broad brush "solution" either.

In fact, I'm skeptical about the claim Climate Change could have been solved generations ago, given that we still haven't developed the means to do it yet.

Edit: okay, perhaps nuclear could provide us with the masses of power generation we need, but that's been ruled out.

> In fact, I'm skeptical about the claim Climate Change could have been solved generations ago, given that we still haven't developed the means to do it yet.

Path dependence. We have not developed the means to solve climate change from where we are now.

Why bet the bank on us humans collectively being able to reduce all our emissions? There are problems will all approaches, a quick Google search pokes some holes in why planting trees is not a good idea: https://earthscience.stackexchange.com/questions/2639/how-ma...

So the billion dollar reward would be quite small sum in the grand scheme of things. And for example with a carbon tax, where collectors could offset emitters, it might also become a quite lucrative business.

> Why bet the bank on a technology that hasn't been invented yet?

Because it's too late. Unless magic non-existent carbon capture technology materializes soon, we're basically fucked.

https://www.vox.com/2016/10/4/13118594/2-degrees-no-more-fos...

Check out that middle graphic. If we really want to avoid 1.5 degrees, and we can’t rely on large-scale carbon sequestration, then the global community has to zero out its carbon emissions by 2026.

Ten years from now.

That article is two years old and, to state the obvious, global CO2 emissions are not on track to reach zero in the next eight years.

But the world doesn't end when we hit 1.5. We'll still be here, and we can still shape how much things change.

> we can still shape how much things change.

No we can't, because most of the CO2 has already been emitted: https://www.carbonbrief.org/analysis-four-years-left-one-poi...

Unless you invent a time machine, or as postulated by OP, some magic sequestration technology to pull CO2 out of the atmosphere and put it back in the ground, it's too late.

It's like we're in a car that's driven over a cliff, and you're saying "Well, we're still here, as long as we invent a way for this car to fly in the next 15 seconds before impact, then we'll be okay"

Atmospheric concentrations are low so you need to harvest a lot of air. To put in context the earth has ~2E9 km^3 air, if you wanted to process every cubic meter of air in the world once in 10 years you'd have a system that could process ~6km^3/s , using air flowing at 30kph(18mph) would require ~800km^2 of collecting area.

There is a cost-effective way: Planting trees, cutting them down and turning the wood to charcoal. You'd need huge areas dedicated to such forests. You'd also need to "unburn" most of the coal and oil we burned so far. That's a mind-boggling amount of matter we're talking about here.

But who would pay for that? If there were the political will we would long have passed a simple carbon tax that, after some adjustment period, would be tied to the price of unburning a ton of CO2.

What about vegetal roofs ? not strong enough ? because there's a huge surface area to tap into.

Just having the biomass is nice, but the crucial step is turning it into charcoal. Roofs also don't produce a lot of biomass per area.

Ok, I get it, too little. But I heard it's also good for insulation.

Sure go for it if you have a house. It looks really nice too. It just doesn't do too much for global warming.

The global CO2 production dwarfs what you could do with trees, I'm fairly certain even if we planted a tree on every square centimeter available, it would not be sufficient to counter our production sufficiently.

What we need is to invest in technology to reduce CO2. Nuclear fusion/fission, solar, wind, electric or alternative fuel cars, redesign CO2 industry processes, etc.

The petrol and coal industry would have to go entirely bankrupt. No exceptions.

If you understand French, there's an engineer called Jean-Marc Jancovici who is deep into the 'nuclear is the only solution so far'. He made talks on youtube on how to decarbonate economies.

I don't think nuclear will be the only solution, solar and wind may be useful in a post-fusion-energy world.

his point is that by looking at numbers, solar and other renewables are orders of magnitude off from being enough. With today's energy consumption of course. If we change our ways, models can be remade.

The surface area of a roof is tiny in comparison to planting miles and miles of forest. It's also very weight sensitive, but the goal is to capture, remove, and continuously replace a huge mass of solid carbon. Finally, green roofs select succulents and other plants that grow slowly, but for this goal you want a species that grows like a weed and produces literal tons of biomass that have to be trucked away and be buried.

The "plant trees for charcoal" idea is basically the bio-engineering method of "build huge photovoltaic solar plant, use electric energy to power chemistry to convert CO2 to oil". Photosynthetic plants are pretty efficient, compared to silicon solar cells, and they're (literally) dirt cheap.

but it's also quite close to CO2 pollution since a lot of emission are in cities (low efficiency use of ICE I believe)

Why burn them to charcoal? Living trees continue to be efficient carbon sinks for potentially hundreds of years. If you have to cut them down you should use the material for construction, to reduce dependency on energy-intensive steel and concrete industry.

But it’s a moot point anyway, because trees simply grow too slowly to be an effective carbon buffer at the timescales that are relevant right now.

You burn them because that prevents decay from releasing CO2, stabilizing the carbon for at least a millennium. Young trees also add biomass much faster than old growth.

Using them for building material is okay as well, but the amount of wood needed to get rid of the excess CO2 is far above any reasonable demand for building material. (We're talking about a trillion tons of carbon here)

”Young” here still means ”decades old” (and large, mature trees keep growing thicker fairly consistently which leads to carbon fixation to be a superlinear function of tree age). Plus recent research indicates that old-growth forests actually continue adding biomass quite efficiently. So any planted trees should at least be allowed to grow a lot longer than your standard tree plantations.

Whatever you do with the biomass a hundred years from now doesn’t really matter; either climate change is in control by then or the humanity is screwed.

Physics/Chemistry: Solid carbon (e.g coal) is more energy-dense than CO2 (per molecular weight unit). This is why you can gain energy from burning coal. To go the other way round you need to add this energy back in to break the very stable double-bonds in the CO2 molecule. This energy is what makes it expensive and there is no way around (except finding a really cheap energy source, but then you probably wouldn't burn coal in the first place)

I would, however, propose that once we have CO2-neutral energy production, we use some of it to recapture CO2 if the effect would be even minimal.

The problem is that "once we have CO2-neutral energy production" is way too late. There are several tipping points where the rising temperature sets off other processes that speed up warming even further.

For example, when the Russian permafrost melts, it will release gigantic amounts of methane, a very potent greenhouse gas, into the atmosphere. Once that happens, not only do you have to capture all the CO2 you emitted, you also have to capture all that methane.

Also, you'll want to recreate the kilometers-thick ice sheets in the arctic. When those are gone, the earth's albedo will drop, which means that it heats up even more quickly since less sunlight is reflected.

Yes, the clathrate gun hypothesis.

Let's also not forget the methan hydrate deposits on the coasts. Even minor temperature increase or pressure change at depth would cause them to explosively abandon their place.

We have found 3km wide crates in the deep sea formed by such methane deposits going nuclear, I doubt such an event would be pleasant for nearby coastal regions.

I did a back of the envelope calculation or maybe better a guesstimate on this awhile back. At perfect conversion efficiency you could turn emitted CO2 back to carbon using 15-20 average sized nuclear power plants. If you realistically get 10% overall efficiency then maybe you need 200 of them. All that assumes you can actually build chemical cells that don't need continuous replacement. It also just compensates for current emissions, and doesn't turn the clock back. My numbers could be very wrong in either direction.

My takeaway was just like losing weight. It's more effective to eat less than to exercise. Here, it's bound to be better to burn less.

This was an electrochemical approach however. It's possible some bio guy will figure it out using photosynthesis.

Just to address the "also just compensates for current emissions" point--the way this tends to be thought of in the research is that, if you assume a completed Step 1 of "develop perfect carbon capture technology", Step 2 is "apply that solution to power plant smokestacks and fuel those power plants by burning and replanting trees / crop waste (corn stalks etc)". So you're not carbon negative on the capture process itself, but can be on the broader system by converting to a fuel source that regenerates through carbon capturing via photosynthesis.

This poses it's own problems though, one of which being the enormous amount of land you would need to dedicate to this process to have a meaningful impact.

The problem here is that uranium extraction and other elements of nuclear power production (e.g. concrete manufacturing) is itself carbon intensive process and takes a while to pay off.

While I don't really know much about the area, one option that I hear has possible potential is forests and then convert them to biochar. Downside is that you obviously need huge quantities of land that some would want to use for farming etc.

There are tons of ways of doing it, but all of them necessarily cost more energy than you extracted from the fossil fuel. So, from an energy economics point of view, first we stop extracting the so-called "unburnable" fossil fuels - end conventional and shale oil exploration and phase out their extraction. Then, with our spare renewable energy, we can start condensing fuel out of the atmosphere; there are several processes for this, including one the US Navy is pioneering for at-sea refuelling of planes on nuclear carriers.

There is the Carbon Prize which is part of the way there [0]:

> A $20 Million global competition to develop breakthrough technologies that will convert CO₂ emissions from power plants and industrial facilities into valuable products like building materials, alternative fuels and other items that we use every day. Teams will be scored on how much CO₂ they convert and the net value of their products.

[0]: https://carbon.xprize.org/

One source of such an incentive could be a cap-and-trade emissions trading scheme with strict caps [0], in which air-capturers are granted emissions rights they can sell.

The EU's ETS [1] is currently the biggest carbon market, regulating about 40% of EU emissions.

It does not grant rights to capturers that take CO2 out of the atmosphere - only to those that reduce the emissions at some plant or factory. Apparently this choice is partly because it's not clear how to make sure that the carbon sink is stable - that the CO2 won't get out again. [2]

Lets assume you could get emissions rights for removing CO2. Would this provide the incentive we want?

The current price for emissions rights is 15€ per 1000 tons of CO2 [3], so an operation to sequester all of the EU's emissions (3.4 * 10^9 t, 2014, [4]) would get a revenue of at most 50 million euro / year. Probably much less since the market would get flooded.

Why is this price so low? The ETS' cap could be too low. Also, the ETS does not really cap emissions at all. Only certain industries, like power or aluminium manufacturing need to present certificates [1b], hence the 40%. Also, industries which would be 'at risk' to leave the EU if they were forced to pay, get free certificates [5] - arguably these would pay the most for rights.

Overall the EU does seem to be doing something right though, since the overall emissions are going down [4]. But the ETS does not seem to internalize the carbon externality.

[0] https://en.wikipedia.org/wiki/Emissions_trading

[1] https://ec.europa.eu/clima/policies/ets_en

[1b] https://ec.europa.eu/clima/sites/clima/files/factsheet_ets_e...

[2] https://en.wikipedia.org/wiki/European_Union_Emission_Tradin...

[3] https://www.theice.com/products/197/EUA-Futures/data?marketI...

[4] https://data.worldbank.org/indicator/EN.ATM.CO2E.PC?location...

[5] https://ec.europa.eu/clima/policies/ets/allowances/leakage_e...

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