Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Engineers are developing new ways to convert greenhouse gases to fuel

uc.edu

Post reply on HN
Print view View original

131–140 of 213 posts

Re: Engineers are developing new ways to convert greenhouse gases to fuel

#131

Post by MauranKilom »

ncmncm wrote: post #116
_Microft wrote: post #27

Earlier quoted context omitted.

It can make sort of sense for applications for which the energy density of the fuel (like for airplanes or rockets) matters a lot. The energy density of current generation lithium ion batteries is insufficient to allow for long-range flights. Synthetic fuels could allow planes to still travel around the world while being effectively net zero emitters because the CO_2 was harvested from the atmosphere (or another, una…

Liquid hydrogen LH2 electrically synthesized on-site at airports from excess peak production will be important in aviation after maybe 2035 (provided civilization doesn't collapse first). Aside from LH2's usefully extreme energy density, pumping less CO2 directly into the stratosphere would be good. We may reasonably expect production of the needed aerogel-insulated LH2 tankage to be mature by then.

Asking as someone only remotely familiar with hydrogen as a fuel: Don't you have the problem of tanks and pipes becoming brittle from hydrogen diffusing into the material? Are there existing/upcoming solutions for this? I was under the impression that this is a pretty fundamental problem with hydrogen being just a proton essentially..

Re: Engineers are developing new ways to convert greenhouse gases to fuel

#132

Post by FirstLvR »

robbrown451 wrote: post #108

Title on HN should probably read "University of Cincinnati" rather than UC. Even I, a graduate of University of Cincinnati now first thought "University of California." (Admittedly I live in California now)

Can you imagine us non Americans trying to remember this things...

Re: Engineers are developing new ways to convert greenhouse gases to fuel

#133

Post by Manuel_D »

ehsankia wrote: post #130
generalizations wrote: post #115

The problem, in general, is obtaining the CO2. Ironically, in industries where massive amounts of CO2 is needed (including biodiesel production from algae), one of the cheapest ways to get it is to just make it. Pulling it out of the air isn't feasible.

Pulling it out of the air isn't feasible. What about pulling it right where it's mostly produced (heavy polluting factories or electricity generators).

Capturing it is difficult. It's coming out the end of a turbine or smelter at very high temperatures. You need to cool it and compress it down.

Then you need to secure a source of hydrogen. Over 90% of industrial hydrogen comes from steam reforming which emits CO2. So you'd need to build out massive electrolysis plants, and power these plants with carbon-free energy.

Finally you'd need to run the Sabatier process, which also needs energy.

It's much, much easier to drive down emissions by just reducing the CO2 released in the first place.

Re: Engineers are developing new ways to convert greenhouse gases to fuel

#134

Post by Manuel_D »

CodeGlitch wrote: post #118
mlindner wrote: post #80

Converting CO2 into fuell isn't the hard part. The hard part is getting the CO2 out of the atmosphere in the first place. We've known how to convert CO2 into fuel since the end of the 19th century. https://en.wikipedia.org/wiki/Sabatier_reaction

This I do not understand... why do we not build a nuclear reactor out in the middle of no-where - easily accessible via shipping - that has the job of taking CO2 out of the atmosphere, and converting into liquid methane? It can run 24/7. Little running costs? No one complaining about NIMBYISM.

It'd be much, much, more effective to hook up a nuclear reactor to the grid to take fossil fuel plants offline, and avoid releasing CO2 in the first place.

Though in the long term, it might be useful to do what you propose to produce carbon neutral hydrocarbon fuel for things that need exceptional energy density. Like air travel or space launch vehicles.

Re: Engineers are developing new ways to convert greenhouse gases to fuel

#135

Post by NickNameNick »

makeitrain wrote: post #123
fho wrote: post #111

Earlier quoted context omitted.

> 1kg of CO2/day which is crazy low if you put it in perspective and see that (gas powered) cars release about 0.2 kg of CO2 ... per kilometer.

That's insane, I didn't realize it was that much. If we could see cars drop carbon turds on the road instead of venting it invisibly in the air we'd all be freaking out right now.

Well, we used to have horses...

There's a reason all the old buildings in big cities are elevated a few steps above street level...

Re: Engineers are developing new ways to convert greenhouse gases to fuel

#136

Post by amelius »

mlindner wrote: post #80

Converting CO2 into fuell isn't the hard part. The hard part is getting the CO2 out of the atmosphere in the first place. We've known how to convert CO2 into fuel since the end of the 19th century. https://en.wikipedia.org/wiki/Sabatier_reaction

> The hard part is getting the CO2 out of the atmosphere in the first place.

From the article: The Martian atmosphere is composed almost entirely of carbon dioxide.

Re: Engineers are developing new ways to convert greenhouse gases to fuel

#137

Post by CodeGlitch »

Manuel_D wrote: post #134
CodeGlitch wrote: post #118

Earlier quoted context omitted.

This I do not understand... why do we not build a nuclear reactor out in the middle of no-where - easily accessible via shipping - that has the job of taking CO2 out of the atmosphere, and converting into liquid methane? It can run 24/7. Little running costs? No one complaining about NIMBYISM.

It'd be much, much, more effective to hook up a nuclear reactor to the grid to take fossil fuel plants offline, and avoid releasing CO2 in the first place. Though in the long term, it might be useful to do what you propose to produce carbon neutral hydrocarbon fuel for things that need exceptional energy density. Like air travel or space launch vehicles.

> Though in the long term, it might be useful to do what you propose to produce carbon neutral hydrocarbon fuel for things that need exceptional energy density. Like air travel or space launch vehicles.

Yes that's what I had in mind - thanks.

I do remain sceptical that electric cars will save us. If everyone buys an electric car, and then plugs them in the evening to charge - I'm not sure the grid will cope very well. IMHO there is still a valid case for running cars, trucks and trains on hydrocarbons.

Re: Engineers are developing new ways to convert greenhouse gases to fuel

#138

Post by orthecreedence »

jl6 wrote: post #11
throwaway894345 wrote: post #2

The actual title is "UC reactor makes Martian fuel" and the subtitle is "A gas station on Mars? Engineers envision the possibilities." But the submission title is "UC reactor converts carbon dioxide to fuel to address climate change"? While it does talk about applications with respect to carbon capture, if we consume the fuel byproduct, presumably we just end up with co2 in the atmosphere? > “In the future we’ll deve…

> if we consume the fuel byproduct, presumably we just end up with co2 in the atmosphere? The process would still be great news if true, as it could be a carbon-neutral source of hydrocarbon fuel for applications that are hard to electrify, like aviation.

From what I know, it's electricity intensive to make the fuels. Now, if only we had a very scalable way to make immense amounts of electricity that didn't depend on weather in a world where the climate is now in disarray. Hmm...

Re: Engineers are developing new ways to convert greenhouse gases to fuel

#139

Post by _Microft »

ncmncm wrote: post #116
_Microft wrote: post #27

Earlier quoted context omitted.

It can make sort of sense for applications for which the energy density of the fuel (like for airplanes or rockets) matters a lot. The energy density of current generation lithium ion batteries is insufficient to allow for long-range flights. Synthetic fuels could allow planes to still travel around the world while being effectively net zero emitters because the CO_2 was harvested from the atmosphere (or another, una…

Liquid hydrogen LH2 electrically synthesized on-site at airports from excess peak production will be important in aviation after maybe 2035 (provided civilization doesn't collapse first). Aside from LH2's usefully extreme energy density, pumping less CO2 directly into the stratosphere would be good. We may reasonably expect production of the needed aerogel-insulated LH2 tankage to be mature by then.

You need to consider the volumetric energy density, not the specific energy (which is energy per mass). LH2 has a high specific energy but pretty low volumetric energy density which means that much larger tanks are needed to store the same amount of energy than for other fuels.

The conditions for storage of LH2 and demands on materials in contact with LH2 are much harder than for e.g. methane.

Re: Engineers are developing new ways to convert greenhouse gases to fuel

#140

Post by _Microft »

yholio wrote: post #106
_Microft wrote: post #27

Earlier quoted context omitted.

It can make sort of sense for applications for which the energy density of the fuel (like for airplanes or rockets) matters a lot. The energy density of current generation lithium ion batteries is insufficient to allow for long-range flights. Synthetic fuels could allow planes to still travel around the world while being effectively net zero emitters because the CO_2 was harvested from the atmosphere (or another, una…

There is already a good solution for planes: ammonia, manufactured efficiently from green hydrogen. You will never be able to use gaseous or liquid hydrogen on planes due to the high volume, weight and risk associated with known storage methods. Ammonia seems to strike the right balance: https://www.ammoniaenergy.org/articles/zero-emission-aircraf...

How are they planning to work around ammonia's toxicity problem? It's fatal if breathed in at concentrations like we currently have CO_2 in the atmosphere (> ~400ppm). If a tank with conventional jetfuel or methane springs a leak or has to be dumped, you've got a huge problem. If that happens with an ammonia tank, you are most likely toast either way.
Post reply on HN