6 ms·

I really don't see the point of this...it takes at least as much energy to "unburn" the CO2 in the air back into organic molecules, as burning the coal/oil rele

by rhelz 3y ago

I really don't see the point of this...it takes at least as much energy to "unburn" the CO2 in the air back into organic molecules, as burning the coal/oil released in the first place. (If it took less, we could make a perpetual motion machine by burning and unburning coal) Are we really supposed to expend as much energy as we expended in the entire industrial age just to remove the excess CO2 in the atmosphere?

genter 3y ago
Gasoline and diesel are much more energy dense than lithium batteries. Tesla has shown that this doesn't matter too much for cars, but lithium battery powered trains and planes are a long way off, if ever. This could be the first step of creating renewable gasoline/diesel for them.
- alexose 3y ago
  Totally agree. We're a lot closer to sustainable aviation fuel (SAF) than we are to electric airliners. Another thing to consider is that aviation only accounts for around 2% of global carbon emissions. If SAF ends up being harder to make than expected, it might end up making sense to keep extracting + refining some fossil fuels and mitigate them using some other means (mineralization, perhaps). Cheap carbon dioxide removal could end up leading to some rather unintuitive outcomes.
  - MrVandemar 3y ago
    > aviation only accounts for around 2% of global carbon emissions You mean: “aviation accounts for around 2% of global carbon emissions”. There is no only about it. 2% is actually a meaningful and substantial number when you consider the pie-chart it's sliced out of represents a collossal problem.
  - rhelz 3y ago
    After a plane burns all its jet fuel to fly where it is going, we will have to expend even more than that much energy to suck the C02 out of the air again. Flying will cost at least 2x as much as it does today.
    - Slava_Propanei 3y ago
      [dead]
    - zamfi 3y ago
      Jet fuel is less than 25% of the cost of running an airline. Flying will cost more, but not necessarily 2x more. Plus that's only if we can't synthesize jet fuel from all that CO2 we're extracting from the air.
    - topkai22 3y ago
      That assumes that price is entirely determined by energy cost, that you need to convert CO2 to a chemical with the same potential energy level as jet fuel, and that energy costs are the same and constant across sources. That’s not true. Fuel accounts 30-50% of the costs of air travel. A straight doubling of fuel costs would not double air travel costs (although it would hurt) The CO2 emitted from air travel wouldn’t necessarily need to be converted back to a very high energy molecule like jet fuel. I’m not a chemist, but I’m pretty sure there are polymers that you can bind the carbon into and not be nearly as energy intensive as recreating petroleum molecules. Finally, wind and solar electricity generation are already generally cheaper than any fossil fuel generation besides nat gas. The EIA (via Wikipedia) had that at around 2x cheaper solar versus diesel generation, and solar and wind continue to see cost improvement. All that being said, any carbon elimination scheme is going to have a cost, but the theoretical cost efficiency can be much better than if you assume energy is 1-1 with cost.
- Zardoz84 3y ago
  Why do you need batteries on trains ? Just electrify the railway. It's a solved problem like a century ago! PD: Yes, you could use a not electrified railway, but simply makes more sense to electrificate all railways
- constantcrying 3y ago
  >lithium battery powered trains If only trains were traveling at predictable routes and you could supply them with electricity while traveling. Let's call it an electric locomotive. Planes, at least passenger yets, will never use lithium ion batteries. Which is why the industry is pivoting to "green" aviation field.
- cbsmith 3y ago
  We've already got electric trains. It's way more efficient to have the energy delivered to the trains on the track than to carry a battery on the train. Planes is another problem.
gyanreyer 3y ago
If the "unburning" could be done using zero-emission renewable energy it seems like that would the best or only way to effectively remove excess CO2. I'm skeptical that there will ever be a true magic bullet carbon capture technology like that though.
- rhelz 3y ago
  We have the tech today. Its just 1) too expensive, and 2) thermodynamics says it always will take more energy to suck the C02 out than we got from putting it there, so what's the point?
alexose 3y ago
> Are we really supposed to expend as much energy as we expended in the entire industrial age just to remove the excess CO2 in the atmosphere? Basically, yeah! The last IPCC described the need for carbon removal in their last report[1]. The gist of it is that we'll need to decarbonize virtually everything, and use removal for the last 5-10% of residual emissions. That ends up being like six billion tons per year by 2025. [1] https://www.ipcc.ch/sr15/faq/faq-chapter-4/ https://www.ipcc.ch/sr15/faq/faq-chapter-4/
- rhelz 3y ago
  But....I mean, for that 5-10%, we have to spend MORE THAN DOUBLE the energy we get from burning carbon....wouldn't we just be better of not burning the carbon? It doesn't compute. I mean, you get my point, right? That 5-10%, supposedly we couldn't get it from some renewable source....we could only get it from burning fossils fuels. So where is the energy going to come from to suck the CO2 back out of the air again? By hypothesis, we didn't have any more renewable energy to use. But you can't clean the air by burning fossils fuels--thermodynamics says that you will always release more C02 than you could recapture.
  - graeme 3y ago
    You’re correct, but: 1. Just stopping burning carbon isn’t enough. We need to take the existing excess carbon from the atmosphere. 2. It would be rational to move on an emergency basis to renewables + nuclear and burn less carbon in order to save future energy. But….well that’s difficult and we need energy now and humans aren’t famous for being rational all the time or having great long run planning in groups So either we figure out how to eventually do it with renewables, nuclear or some other method, or we fail
    - rhelz 3y ago
      > Just stopping burning carbon isn’t enough. We need to take the existing excess carbon from the atmosphere. Yeah, I just don't see that happening. E.g. suppose we only wanted to take the CO2 out of the air that we put in last year. It would take more energy to do that than we got from burning fossils fuels last year. I don't remotely see how that would at all be feasible. I mean, yeah, 100 thousand of years of plants doing photosynthesis--taking that energy slowly but surely from the sun--would do it. But the shorter of a timeframe you want it done, the more energy you are going to need--and since energy is conserved, that will eventually end up as waste heat and heat up the earth anyways.
photochemsyn 3y ago
The only way to remove CO2 permanently from the atmosphere using these technologies is to seek endpoints like diamond and carbon fiber. Regardless, achieving steady state (atm CO2 extraction == atm CO2 injection) would be desirable, then at least we'd stabilize the atmosphere's chemical composition.
UncleEntity 3y ago
> Are we really supposed to expend as much energy as we expended in the entire industrial age just to remove the excess CO2 in the atmosphere? I'm not sure that's the correct argument. We only really need to expend as much energy to convert stuff into coal as was needed to turn it into coal in the first place. If we can do it more efficiently than Nature™ then we are energy positive since all the effort to extract it is already expended and (reading the terms & conditions) nonrefundable. It seems to me... could be wrong.

by rhelz 3y ago

genter 3y ago

Gasoline and diesel are much more energy dense than lithium batteries. Tesla has shown that this doesn't matter too much for cars, but lithium battery powered trains and planes are a long way off, if ever. This could be the first step of creating renewable gasoline/diesel for them.

alexose 3y ago
Totally agree. We're a lot closer to sustainable aviation fuel (SAF) than we are to electric airliners. Another thing to consider is that aviation only accounts for around 2% of global carbon emissions. If SAF ends up being harder to make than expected, it might end up making sense to keep extracting + refining some fossil fuels and mitigate them using some other means (mineralization, perhaps). Cheap carbon dioxide removal could end up leading to some rather unintuitive outcomes.
- MrVandemar 3y ago
  > aviation only accounts for around 2% of global carbon emissions You mean: “aviation accounts for around 2% of global carbon emissions”. There is no only about it. 2% is actually a meaningful and substantial number when you consider the pie-chart it's sliced out of represents a collossal problem.
- rhelz 3y ago
  After a plane burns all its jet fuel to fly where it is going, we will have to expend even more than that much energy to suck the C02 out of the air again. Flying will cost at least 2x as much as it does today.
  - Slava_Propanei 3y ago
    [dead]
  - zamfi 3y ago
    Jet fuel is less than 25% of the cost of running an airline. Flying will cost more, but not necessarily 2x more. Plus that's only if we can't synthesize jet fuel from all that CO2 we're extracting from the air.
  - topkai22 3y ago
    That assumes that price is entirely determined by energy cost, that you need to convert CO2 to a chemical with the same potential energy level as jet fuel, and that energy costs are the same and constant across sources. That’s not true. Fuel accounts 30-50% of the costs of air travel. A straight doubling of fuel costs would not double air travel costs (although it would hurt) The CO2 emitted from air travel wouldn’t necessarily need to be converted back to a very high energy molecule like jet fuel. I’m not a chemist, but I’m pretty sure there are polymers that you can bind the carbon into and not be nearly as energy intensive as recreating petroleum molecules. Finally, wind and solar electricity generation are already generally cheaper than any fossil fuel generation besides nat gas. The EIA (via Wikipedia) had that at around 2x cheaper solar versus diesel generation, and solar and wind continue to see cost improvement. All that being said, any carbon elimination scheme is going to have a cost, but the theoretical cost efficiency can be much better than if you assume energy is 1-1 with cost.
Zardoz84 3y ago
Why do you need batteries on trains ? Just electrify the railway. It's a solved problem like a century ago! PD: Yes, you could use a not electrified railway, but simply makes more sense to electrificate all railways
constantcrying 3y ago
>lithium battery powered trains If only trains were traveling at predictable routes and you could supply them with electricity while traveling. Let's call it an electric locomotive. Planes, at least passenger yets, will never use lithium ion batteries. Which is why the industry is pivoting to "green" aviation field.
cbsmith 3y ago
We've already got electric trains. It's way more efficient to have the energy delivered to the trains on the track than to carry a battery on the train. Planes is another problem.

gyanreyer 3y ago

If the "unburning" could be done using zero-emission renewable energy it seems like that would the best or only way to effectively remove excess CO2. I'm skeptical that there will ever be a true magic bullet carbon capture technology like that though.

rhelz 3y ago
We have the tech today. Its just 1) too expensive, and 2) thermodynamics says it always will take more energy to suck the C02 out than we got from putting it there, so what's the point?

alexose 3y ago

> Are we really supposed to expend as much energy as we expended in the entire industrial age just to remove the excess CO2 in the atmosphere? Basically, yeah! The last IPCC described the need for carbon removal in their last report[1]. The gist of it is that we'll need to decarbonize virtually everything, and use removal for the last 5-10% of residual emissions. That ends up being like six billion tons per year by 2025. [1] https://www.ipcc.ch/sr15/faq/faq-chapter-4/ https://www.ipcc.ch/sr15/faq/faq-chapter-4/

rhelz 3y ago
But....I mean, for that 5-10%, we have to spend MORE THAN DOUBLE the energy we get from burning carbon....wouldn't we just be better of not burning the carbon? It doesn't compute. I mean, you get my point, right? That 5-10%, supposedly we couldn't get it from some renewable source....we could only get it from burning fossils fuels. So where is the energy going to come from to suck the CO2 back out of the air again? By hypothesis, we didn't have any more renewable energy to use. But you can't clean the air by burning fossils fuels--thermodynamics says that you will always release more C02 than you could recapture.
- graeme 3y ago
  You’re correct, but: 1. Just stopping burning carbon isn’t enough. We need to take the existing excess carbon from the atmosphere. 2. It would be rational to move on an emergency basis to renewables + nuclear and burn less carbon in order to save future energy. But….well that’s difficult and we need energy now and humans aren’t famous for being rational all the time or having great long run planning in groups So either we figure out how to eventually do it with renewables, nuclear or some other method, or we fail
  - rhelz 3y ago
    > Just stopping burning carbon isn’t enough. We need to take the existing excess carbon from the atmosphere. Yeah, I just don't see that happening. E.g. suppose we only wanted to take the CO2 out of the air that we put in last year. It would take more energy to do that than we got from burning fossils fuels last year. I don't remotely see how that would at all be feasible. I mean, yeah, 100 thousand of years of plants doing photosynthesis--taking that energy slowly but surely from the sun--would do it. But the shorter of a timeframe you want it done, the more energy you are going to need--and since energy is conserved, that will eventually end up as waste heat and heat up the earth anyways.

photochemsyn 3y ago

The only way to remove CO2 permanently from the atmosphere using these technologies is to seek endpoints like diamond and carbon fiber. Regardless, achieving steady state (atm CO2 extraction == atm CO2 injection) would be desirable, then at least we'd stabilize the atmosphere's chemical composition.

UncleEntity 3y ago

> Are we really supposed to expend as much energy as we expended in the entire industrial age just to remove the excess CO2 in the atmosphere? I'm not sure that's the correct argument. We only really need to expend as much energy to convert stuff into coal as was needed to turn it into coal in the first place. If we can do it more efficiently than Nature™ then we are energy positive since all the effort to extract it is already expended and (reading the terms & conditions) nonrefundable. It seems to me... could be wrong.