4 ms·

Its important to remember the time constraint in these conversations. Engineering is about constraints, and if you simply remove the biggest one (time) it beco

Its important to remember the time constraint in these conversations. Engineering is about constraints, and if you simply remove the biggest one (time) it becomes facile and easy to endlessly talk about future, hypothetical, optimistic "someday" solutions. It is vapid empty happy-talk. When you factor in the time constraint, specifically the timeframes outlined in the IPCC SR 1.5 report, then you simply cannot claim that direct air capture fuels are a meaningful part of the conversation of what to do with air travels footprint. I am 100% in favor of continued and increased investment in R&D for DAC. I am 0% delusional that it will be a viable solution in the timeframe we need it to be (same goes for thorium and fusion). If you're not solving for the time constraint and the curve shape in this graph, you're not talking about "solutions" you're just chit chatting about (cool) tech: https://www.ipcc.ch/site/assets/uploads/sites/2/2019/02/SPM3a.png https://www.ipcc.ch/site/assets/uploads/sites/2/2019/02/SPM3...

Erlich_Bachman 7y ago
This is an amazing comment that puts it very well into words and sadly it should be added as a disclaimer under about a half of the articles that end up on HN about any future tech.
thinkcontext 7y ago
Airplanes are not going to stop flying. We can try raising the price to make them fly less than they would otherwise but there will still be a need to lower the carbon footprint of flight. Synthesizing fuel from captured CO2 seems like a much better pathway than batteries. Also, I don't think its valid to compare it to thorium or fusion. We can make synthetic fuel from captured CO2 today whereas those are science projects. Synthetic fuel isn't cost effective given economic and political realities but its likely this will occur within the next 10 years in at least some places. Minor point, people seem to marry DAC with synthesizing fuel, probably because Carbon Engineering has gotten a lot of press. Fuel can be synthesized from CO2 from any source. It is my understanding that DAC is currently more expensive than capturing from a point source, like a natural gas power plant. This is due to CO2 being such a small percentage of the atmosphere vs 10%+ from plant flue gases. So, while DAC is more expensive and there are still substantial point sources of CO2, fuel made from DAC will be more expensive from point source capture.
- cagenut 7y ago
  point source capturing co2 from burning fossil fuels and then turning it into more liquid fuels that you then burn again is madness. you get that right? it makes less sense than simply saying "fuck it" and pumping the same amount of fossil fuel up. at least then you don't have to pay the energy cost of the transitions. this kind of high-anxiety circular reasoning is hopefully the 'bargaining' phase before you move onto acceptance.
  - thinkcontext 7y ago
    I don't get that because its not true. In both scenarios after the energy consuming activities are done the same amount of CO2 is in the air (ignoring operational efficiency). One just costs more than the other because a more difficult path of capturing the CO2 is chosen.
    - cagenut 7y ago
      oh well if we just ignore efficiency and cost! you are living in a world of spherical cows, not in the reality of the climate emergency. please understand that as the body counts rise this level of "technically correct" pedantry will be seen for the rather gross complicity it is.
      - thinkcontext 7y ago
        The operational efficiency of both is probably within 10% of each other, so not that significant compared to the big picture of what we are discussing. My guess is that DAC actually fares worse because you have to run an enormous bank of fans to suck in all that air which is why it costs more. As for cost, I'm not ignoring it, it was my point. Fuel from one pathway costs more from another pathway. High cost is a barrier to taking a solution out of the lab and actually putting it into action to causing less CO2 to be emitted. If 2 fuel pathways have the same carbon footprint but one costs less than the other why would you choose the one that costs more? I'm willing to listen if you would like to explain why you think DAC is better but so far you haven't done that, you've just been insulting which I don't get.

Erlich_Bachman 7y ago

This is an amazing comment that puts it very well into words and sadly it should be added as a disclaimer under about a half of the articles that end up on HN about any future tech.

thinkcontext 7y ago

Airplanes are not going to stop flying. We can try raising the price to make them fly less than they would otherwise but there will still be a need to lower the carbon footprint of flight. Synthesizing fuel from captured CO2 seems like a much better pathway than batteries. Also, I don't think its valid to compare it to thorium or fusion. We can make synthetic fuel from captured CO2 today whereas those are science projects. Synthetic fuel isn't cost effective given economic and political realities but its likely this will occur within the next 10 years in at least some places. Minor point, people seem to marry DAC with synthesizing fuel, probably because Carbon Engineering has gotten a lot of press. Fuel can be synthesized from CO2 from any source. It is my understanding that DAC is currently more expensive than capturing from a point source, like a natural gas power plant. This is due to CO2 being such a small percentage of the atmosphere vs 10%+ from plant flue gases. So, while DAC is more expensive and there are still substantial point sources of CO2, fuel made from DAC will be more expensive from point source capture.

cagenut 7y ago
point source capturing co2 from burning fossil fuels and then turning it into more liquid fuels that you then burn again is madness. you get that right? it makes less sense than simply saying "fuck it" and pumping the same amount of fossil fuel up. at least then you don't have to pay the energy cost of the transitions. this kind of high-anxiety circular reasoning is hopefully the 'bargaining' phase before you move onto acceptance.
- thinkcontext 7y ago
  I don't get that because its not true. In both scenarios after the energy consuming activities are done the same amount of CO2 is in the air (ignoring operational efficiency). One just costs more than the other because a more difficult path of capturing the CO2 is chosen.
  - cagenut 7y ago
    oh well if we just ignore efficiency and cost! you are living in a world of spherical cows, not in the reality of the climate emergency. please understand that as the body counts rise this level of "technically correct" pedantry will be seen for the rather gross complicity it is.
    - thinkcontext 7y ago
      The operational efficiency of both is probably within 10% of each other, so not that significant compared to the big picture of what we are discussing. My guess is that DAC actually fares worse because you have to run an enormous bank of fans to suck in all that air which is why it costs more. As for cost, I'm not ignoring it, it was my point. Fuel from one pathway costs more from another pathway. High cost is a barrier to taking a solution out of the lab and actually putting it into action to causing less CO2 to be emitted. If 2 fuel pathways have the same carbon footprint but one costs less than the other why would you choose the one that costs more? I'm willing to listen if you would like to explain why you think DAC is better but so far you haven't done that, you've just been insulting which I don't get.