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The main issue with CO2 is that the concentrations in air are pretty low. A couple of hundreds of parts per million. So, most synthetic fuel generation is bottl

The main issue with CO2 is that the concentrations in air are pretty low. A couple of hundreds of parts per million. So, most synthetic fuel generation is bottle necked on getting enough CO2. If you are processing a kg of air, you'd be getting only a fraction of a gram of CO2. So if you want to produce say a ton of fuel, you are looking at processing many millions of tons of air. That's why a lot of synthetic fuel generation is often paired with carbon capture schemes or bio mass (like this one). But of course a lot of those carbon sources aren't actually that clean. Biomass sounds nice until you realize that farming is a big emitter of CO2. And generating fuel from carbon capture of course defeats the purpose. You capture it at great cost and then you create a fuel. Which you then burn and dump in the atmosphere. This particular scheme in Germany exists because of the influence of car manufacturers there. Companies like BMW are dragging their heels getting rid of their ICE car manufacturing operations and pretending that there are unicorn solutions like hydrogen, synthetic fuels, etc. are great excuses to keep their factories going for a few years longer. Of course EVs are eating their lunch at this point and they are now actually producing lots of those as well.

chii 2y ago
> You capture it at great cost and then you create a fuel. Which you then burn and dump in the atmosphere. But if the need for carbon based fuels is not able to be eliminated, this is the next best thing. It is better than digging more of it out of the ground, and then burn and dump it into the air!
- jillesvangurp 2y ago
  Mainly jet fuel. Cars and trucks will do just fine on batteries. The point with carbon capture is that the captured carbon still comes from fossil fuels. You burn it, you capture it, make fuel, and then you burn it again. So, it's slightly less worse than burning it only once but 100% of it still ends up in the atmosphere. Synthetic fuels made with biomass are more sustainable but only if the biomass is produced sustainably. Which it often isn't. Dumping a lot of CO2 in the air to produce corn and then turn it into ethanol would be the classic example here of something a lot of countries do at scale that isn't really all that green.
  - usrusr 2y ago
    > The point with carbon capture is that the captured carbon still comes from fossil fuels That's not a property of carbon capture, it's a property of the fuel coming in on the other side of the (stationary) process. We certainly won't be seeing carbon capture of jet fuel any time soon, so the fuel preceeding the capture will definitely not be the one produced. Think waste incineration, think bioplastics (don't waste that precious energy on some pointless biodegradation!), think single use paper, think moving the part of the natural carbon cycle that happens in bushfires and the like into a controlled environment.
    - jillesvangurp 2y ago
      Actually jet fuel is already being synthesized from a mix of biomass and captured carbon. A lot of the carbon capture schemes propose capturing carbon from coal plants or similar sources where massive amounts of fossil fuels are being burned. But you are right that there are clean sources as well. But mostly with carbon capture, the source is fossil fuel.
      - usrusr 2y ago
        Fossil burning plants that capture carbon do it for the greenwashing, not because there might be some use for the concentrated CO2. Renewable burning plants have little incentive to greenwash. Renewable burning does exist, and I suppose that group is much bigger than the tiny subset of fossil burning plants that actually do capture. If we include waste incineration plants in the renewable group (the true multifuel specialists) then the conclusion is that capacity is already abundant, and some of those might actually be considering capture (but their greenwashing pressure isn't remotely as big as in e.g. the coal business, where the greenwashing is nothing less than an existential last ditch hail mary attempt)
        pfdietz 2y ago
        > Renewable burning plants have little incentive to greenwash. That just reflects lack of sufficient CO2 price. Make that high enough and it would become profitable for the CO2 to be sequestered rather than released, assuming the CO2 tax applies to negative CO2 emission.
usrusr 2y ago
That's why for every very high value use case (see chii sibling post) you keep some low value use cases running that don't really require high energy concentration fuel. Burn shrubs, waste (e.g. bioplastics), whatever for heat and stationary power and capture that CO2. Low concentration fuels are well available in renewable form and will be forever. Bottleneck solved, at least as long as you don't imagine you could keep up fossil age consumption rates with synthfuels (you can't). Leave those many millions of tons of air to processes we already run on them anyways. You are right (also with that last paragraph), direct air capture is usually a scam. I might be willing to grant a weak exception to projects that put serial self-containedness front and center, e.g. terraform industries (not to be confused with terraform labs...) would certainly be overwhelmed if they tried to tailor a capturing biomass plant to the local situation with each installation. But even they should better spell out in their advertising "optional, could be substituted with:" for the DAC.
generic92034 2y ago
> Of course EVs are eating their lunch at this point and they are now actually producing lots of those as well. Are actual EV sales numbers reflecting this, in Germany?
- swiftcoder 2y ago
  Despite their loud complaints about electric cars, yes. EVs sales are rising rapidly, and account for >30% of new car sales in the past year (and that's not counting PHEVs)
  - generic92034 2y ago
    In the past year EV sales went very well, agreed. But recently I am seeing articles like this one: https://www.tagesschau.de/wirtschaft/unternehmen/vw-elektrostrategie-100.html https://www.tagesschau.de/wirtschaft/unternehmen/vw-elektros... A sharp decline in EV sales for Volkswagen, so they are asking for subsidies.
- pfdietz 2y ago
  Battery prices are falling very quickly this year, so EV sales globally are set to explode.
  - generic92034 2y ago
    That might be the case, but currently EV prices are generally still significantly higher than ICE car prices of the same class, hitting a slow economy in some EU countries. Maybe Chinese EV can fill that gap.
pfdietz 2y ago
The proposal described was using methane from biogas. But the microbial decomposition of carbohydrates that creates biogas also creates CO2, in equal molar quantity: (CH2O)2 --> CH4 + CO2 So, if you want to get as much fuel as you can out of the carbon in biomass, you want to use extra hydrogen (and in this case, it would mean they wouldn't have to separate out the methane in the biogas; just add hydrogen and reform the whole mixture). That extra CO2 is available without the need for expensive direct air capture: the plants already captured it. You could even directly hydrogenate biomass (or, perhaps, molecules derived from aggressive depolymerization of biomass) instead of going through biogas. This is Virent's approach. It avoids the need to break all the C-C bonds before recreating them in the synfuel. There have been efforts to use solar energy to directly gasify biomass. A company called Sundrop, out of Colorado, was trying to commercialize this 15 years ago. But then fracking dropped the price of natural gas and it all collapsed; the remnants of the company were bought by Chesapeake Energy (a natural gas producer) not long after.
mgerdts 2y ago
> If you are processing a kg of air, you'd be getting only a fraction of a gram of CO2. So if you want to produce say a ton of fuel, you are looking at processing many millions of tons of air. If this could be within piping distance of lime kilns, the concentrated CO2 emitted in cement production could be used. Both processes need a bunch of heat so maybe they could get that from the same solar collectors.
- pfdietz 2y ago
  This still causes net CO2 emission to the atmosphere (cement does end up absorbing some CO2 later, but it cannot absorb all of it.) Eliminating CO2 emission from cement production is actually a considerable problem. It's either going to require complete sequestration of all this unavoidable CO2 production, or it's going to require production of calcium oxide from silicates. For example: CaSiO3 + 2 HCl --> CaCl2 + H2O + SiO2 CaCl2 + H2O + heat --> CaO + 2 HCl The last step occurs at high temperature, driving the reaction to the right.

chii 2y ago

> You capture it at great cost and then you create a fuel. Which you then burn and dump in the atmosphere. But if the need for carbon based fuels is not able to be eliminated, this is the next best thing. It is better than digging more of it out of the ground, and then burn and dump it into the air!

jillesvangurp 2y ago
Mainly jet fuel. Cars and trucks will do just fine on batteries. The point with carbon capture is that the captured carbon still comes from fossil fuels. You burn it, you capture it, make fuel, and then you burn it again. So, it's slightly less worse than burning it only once but 100% of it still ends up in the atmosphere. Synthetic fuels made with biomass are more sustainable but only if the biomass is produced sustainably. Which it often isn't. Dumping a lot of CO2 in the air to produce corn and then turn it into ethanol would be the classic example here of something a lot of countries do at scale that isn't really all that green.
- usrusr 2y ago
  > The point with carbon capture is that the captured carbon still comes from fossil fuels That's not a property of carbon capture, it's a property of the fuel coming in on the other side of the (stationary) process. We certainly won't be seeing carbon capture of jet fuel any time soon, so the fuel preceeding the capture will definitely not be the one produced. Think waste incineration, think bioplastics (don't waste that precious energy on some pointless biodegradation!), think single use paper, think moving the part of the natural carbon cycle that happens in bushfires and the like into a controlled environment.
  - jillesvangurp 2y ago
    Actually jet fuel is already being synthesized from a mix of biomass and captured carbon. A lot of the carbon capture schemes propose capturing carbon from coal plants or similar sources where massive amounts of fossil fuels are being burned. But you are right that there are clean sources as well. But mostly with carbon capture, the source is fossil fuel.
    - usrusr 2y ago
      Fossil burning plants that capture carbon do it for the greenwashing, not because there might be some use for the concentrated CO2. Renewable burning plants have little incentive to greenwash. Renewable burning does exist, and I suppose that group is much bigger than the tiny subset of fossil burning plants that actually do capture. If we include waste incineration plants in the renewable group (the true multifuel specialists) then the conclusion is that capacity is already abundant, and some of those might actually be considering capture (but their greenwashing pressure isn't remotely as big as in e.g. the coal business, where the greenwashing is nothing less than an existential last ditch hail mary attempt)
      - pfdietz 2y ago
        > Renewable burning plants have little incentive to greenwash. That just reflects lack of sufficient CO2 price. Make that high enough and it would become profitable for the CO2 to be sequestered rather than released, assuming the CO2 tax applies to negative CO2 emission.

usrusr 2y ago

That's why for every very high value use case (see chii sibling post) you keep some low value use cases running that don't really require high energy concentration fuel. Burn shrubs, waste (e.g. bioplastics), whatever for heat and stationary power and capture that CO2. Low concentration fuels are well available in renewable form and will be forever. Bottleneck solved, at least as long as you don't imagine you could keep up fossil age consumption rates with synthfuels (you can't). Leave those many millions of tons of air to processes we already run on them anyways. You are right (also with that last paragraph), direct air capture is usually a scam. I might be willing to grant a weak exception to projects that put serial self-containedness front and center, e.g. terraform industries (not to be confused with terraform labs...) would certainly be overwhelmed if they tried to tailor a capturing biomass plant to the local situation with each installation. But even they should better spell out in their advertising "optional, could be substituted with:" for the DAC.

generic92034 2y ago

> Of course EVs are eating their lunch at this point and they are now actually producing lots of those as well. Are actual EV sales numbers reflecting this, in Germany?

swiftcoder 2y ago
Despite their loud complaints about electric cars, yes. EVs sales are rising rapidly, and account for >30% of new car sales in the past year (and that's not counting PHEVs)
- generic92034 2y ago
  In the past year EV sales went very well, agreed. But recently I am seeing articles like this one: https://www.tagesschau.de/wirtschaft/unternehmen/vw-elektrostrategie-100.html https://www.tagesschau.de/wirtschaft/unternehmen/vw-elektros... A sharp decline in EV sales for Volkswagen, so they are asking for subsidies.
pfdietz 2y ago
Battery prices are falling very quickly this year, so EV sales globally are set to explode.
- generic92034 2y ago
  That might be the case, but currently EV prices are generally still significantly higher than ICE car prices of the same class, hitting a slow economy in some EU countries. Maybe Chinese EV can fill that gap.

pfdietz 2y ago

The proposal described was using methane from biogas. But the microbial decomposition of carbohydrates that creates biogas also creates CO2, in equal molar quantity: (CH2O)2 --> CH4 + CO2 So, if you want to get as much fuel as you can out of the carbon in biomass, you want to use extra hydrogen (and in this case, it would mean they wouldn't have to separate out the methane in the biogas; just add hydrogen and reform the whole mixture). That extra CO2 is available without the need for expensive direct air capture: the plants already captured it. You could even directly hydrogenate biomass (or, perhaps, molecules derived from aggressive depolymerization of biomass) instead of going through biogas. This is Virent's approach. It avoids the need to break all the C-C bonds before recreating them in the synfuel. There have been efforts to use solar energy to directly gasify biomass. A company called Sundrop, out of Colorado, was trying to commercialize this 15 years ago. But then fracking dropped the price of natural gas and it all collapsed; the remnants of the company were bought by Chesapeake Energy (a natural gas producer) not long after.

mgerdts 2y ago

> If you are processing a kg of air, you'd be getting only a fraction of a gram of CO2. So if you want to produce say a ton of fuel, you are looking at processing many millions of tons of air. If this could be within piping distance of lime kilns, the concentrated CO2 emitted in cement production could be used. Both processes need a bunch of heat so maybe they could get that from the same solar collectors.

pfdietz 2y ago
This still causes net CO2 emission to the atmosphere (cement does end up absorbing some CO2 later, but it cannot absorb all of it.) Eliminating CO2 emission from cement production is actually a considerable problem. It's either going to require complete sequestration of all this unavoidable CO2 production, or it's going to require production of calcium oxide from silicates. For example: CaSiO3 + 2 HCl --> CaCl2 + H2O + SiO2 CaCl2 + H2O + heat --> CaO + 2 HCl The last step occurs at high temperature, driving the reaction to the right.