Methane Production -- Sabatier Process

[Ace]

As requested:

I'd love a thread that dug into the best way to do methane production and the nuances of it. Don't fret too hard about where to put it. Just start it. We can always move it later. It is very helpful for the starting post to link to other relevant threads. The chemical industry one seems apt to me and this one.

Other threads:
Power Options for a Mars Settlement
ISRU Sabatier; Cost of fuel on Mars (power & water excavation)

I've attached a copy of the fuel production diagram from Musk's 2016 presentation. He has repeatedly said that they plan to use the Sabatier process.

The main engineering problems appear to be:

-- CO2 extraction from the atmosphere (starting from 1% of the pressure on Earth, at roughly -40C)
-- Obtaining water ice (perhaps embedded with subsurface regolith, as a Martian form of permafrost)
-- Melting the ice
-- Refining the resulting water to some degree (filtration? distillation?)
-- Electrolysis of the water into H2 and O2
-- H2 handling (will it require storage?)
-- O2 liquifaction and storage
-- CH4 production using the Sabatier process (H2 + CO2 --> CH4 + H2O)
-- CH4 liquifaction and storage
-- Recycling generated H2O back into the system
-- Doing all of the above at the required scale
-- Power generation and control systems

The Sabatier process itself requires high temperature (~300 to 400C) and pressure, along with a catalyst, such as Nickel or Ruthenium on Alumina. Efficient electrolysis requires corrosion-resistant high-surface-area electrodes.

Here's a relevant paper:

Mars Atmospheric Conversion to Methane and Water: An Engineering Model of the Sabatier Reactor with Characterization of Ru/Al2O3 for Long Duration Use on Mars
http://hdl.handle.net/2060/20170007818

[gongora]

There have been several conversations about this before on the forums, here is one:
ISRU Sabatier; Cost of fuel on Mars (power & water excavation)

[DigitalMan]

It would be interesting to see something using methanogens. 

I see there are posts in one of the ISS threads about experiments with methanogens.  And there are other methane production threads that mention it.

[Ace]

It would be interesting to see something using methanogens. 

I see there are posts in one of the ISS threads about experiments with methanogens.  And there are other methane production threads that mention it.

Certainly would be interesting to see the engineering trade-offs between methanogens and the Sabatier process.

My guess is that trying to use an organic approach on Mars would be risky. Methanogenic organisms would have to be kept alive, and doing so requires more than just hydrogen, water, CO2 and anerobic conditions. Plus, if something goes wrong that kills the cultures (or if they just can't live on the surface of Mars for some reason), the entire mission is at risk. Whereas with a Sabatier reactor, there might be a setback, but it's just a machine, and can be repaired.

I would also be concerned about impurities in the output stream from organics, although purification is possible, of course.

FWIW, in the end-to-end fuel production system, I think the Sabatier reactor itself will end up being a pretty small part. Methanogens would undoubtedly be much more complex.

I wonder what the most useful initial figure of merit is here to compare alternatives. Something like energy required per kg of CH4 and O2 produced?

[ModeHopper]

At last, a thread where I am vaguely qualified to give some meaningful input, how exciting! (I'm an exoplanetary quantum physicist). This is an interesting and relevant paper:

Radar evidence of subglacial liquid water on Mars, R. Orosei et al. (2018)

The presence of liquid water at the Martian South pole (if true) would eliminate the need to melt the ice, which is a non-trivial improvement because it reduces the total energy required (a precious resource for a Martian colony). Additionally, the South pole has dry ice reserves, which might be an alternative way of obtaining CO₂ (as opposed to extracting it out of the thin Martian atmosphere - I'm not sure which is easier).

I also saw some people on Reddit jumping at the idea of extracting methane directly from the apparent methane reserves on Mars after Curiosity detected those methane spikes. I'd just like to pre-empt those suggestions by pointing out that the evidence we have of methane is still quite tentative. It was only confirmed independently in April of this year by Giuranna et al., and we don't know the size or abundance of these methane reserves yet. So it certainly seems like the Sabatier process is the safest route for the time being. You don't want to rock up on Mars (pardon the pun) under the assumption that you'll find methane aplenty only to quickly realise it's not the case and you're now stranded with no way to get home.

[Ace]

At last, a thread where I am vaguely qualified to give some meaningful input, how exciting! (I'm an exoplanetary quantum physicist). This is an interesting and relevant paper:

Radar evidence of subglacial liquid water on Mars, R. Orosei et al. (2018)

The presence of liquid water at the Martian South pole (if true) would eliminate the need to melt the ice, which is a non-trivial improvement because it reduces the total energy required (a precious resource for a Martian colony). Additionally, the South pole has dry ice reserves, which might be an alternative way of obtaining CO₂ (as opposed to extracting it out of the thin Martian atmosphere - I'm not sure which is easier).

It's possible that the liquid water at the south pole is being kept in liquid form only due to the high pressure it's under. If that's correct, it would add significant complexity to the drilling process. If it's super-cooled, once obtained, it may actually need to be heated before it can be used. Reports are that the liquid water is 1,500m deep, but in a zone only about 1m deep, which may further add to the complexity of drilling.

Although it would be interesting to run the numbers, my expectation is that you wouldn't want to trade more complexity (cost, schedule) on the drilling side for the energy savings from avoiding melting.

One of the best ways to purify CO2 out of the Martian atmosphere would be through freezing, so having it pre-frozen would be good from an energy perspective. Would the energy savings there be worth the trade-offs of much less efficient power generation and more difficult living conditions? Again, sure, run the numbers -- but my guess is that it's not even close.

[Selenaut]

Decompression would surely happen while ascending through the borehole so you would need to have some heating system for the casing or it would get plugged of ice very fast.

[wannamoonbase]

I’ve thought for years that SpaceX would be wise to start testing sabatier hardware by making their own fuel for Raptor and SS/SH.

Get some solar panels from Tesla build a couple reactors and start will some veto tanks at the launch sites.

[lamontagne]

At last, a thread where I am vaguely qualified to give some meaningful input, how exciting! (I'm an exoplanetary quantum physicist). This is an interesting and relevant paper:

Radar evidence of subglacial liquid water on Mars, R. Orosei et al. (2018)

The presence of liquid water at the Martian South pole (if true) would eliminate the need to melt the ice, which is a non-trivial improvement because it reduces the total energy required (a precious resource for a Martian colony). Additionally, the South pole has dry ice reserves, which might be an alternative way of obtaining CO₂ (as opposed to extracting it out of the thin Martian atmosphere - I'm not sure which is easier).

I also saw some people on Reddit jumping at the idea of extracting methane directly from the apparent methane reserves on Mars after Curiosity detected those methane spikes. I'd just like to pre-empt those suggestions by pointing out that the evidence we have of methane is still quite tentative. It was only confirmed independently in April of this year by Giuranna et al., and we don't know the size or abundance of these methane reserves yet. So it certainly seems like the Sabatier process is the safest route for the time being. You don't want to rock up on Mars (pardon the pun) under the assumption that you'll find methane aplenty only to quickly realise it's not the case and you're now stranded with no way to get home.

The problem I see with using existing methane on Mars is that you don't have the required oxygen.  Methane on its own is interesting as a chemical feedstock, but it won't rock your rocket!
You need oxygen as well.  Water electrolysis is an energy hog, but I think CO2 separation is also pretty difficult, and I don't really see other significant oxygen sources that don't also require a lot of energy.  There is some oxygen in the martian atmosphere, but not much.

[A_M_Swallow]

At last, a thread where I am vaguely qualified to give some meaningful input, how exciting! (I'm an exoplanetary quantum physicist). This is an interesting and relevant paper:

Radar evidence of subglacial liquid water on Mars, R. Orosei et al. (2018)

The presence of liquid water at the Martian South pole (if true) would eliminate the need to melt the ice, which is a non-trivial improvement because it reduces the total energy required (a precious resource for a Martian colony). Additionally, the South pole has dry ice reserves, which might be an alternative way of obtaining CO₂ (as opposed to extracting it out of the thin Martian atmosphere - I'm not sure which is easier).

I also saw some people on Reddit jumping at the idea of extracting methane directly from the apparent methane reserves on Mars after Curiosity detected those methane spikes. I'd just like to pre-empt those suggestions by pointing out that the evidence we have of methane is still quite tentative. It was only confirmed independently in April of this year by Giuranna et al., and we don't know the size or abundance of these methane reserves yet. So it certainly seems like the Sabatier process is the safest route for the time being. You don't want to rock up on Mars (pardon the pun) under the assumption that you'll find methane aplenty only to quickly realise it's not the case and you're now stranded with no way to get home.

The problem I see with using existing methane on Mars is that you don't have the required oxygen.  Methane on its own is interesting as a chemical feedstock, but it won't rock your rocket!
You need oxygen as well.  Water electrolysis is an energy hog, but I think CO2 separation is also pretty difficult, and I don't really see other significant oxygen sources that don't also require a lot of energy.  There is some oxygen in the martian atmosphere, but not much.

Mars has perchlorate. These can be used as oxidisers in solid boosters. It may also be possible to extract oxygen from them. Methane may even be able to burn perchlorate.
https://www.nasa.gov/ames/ocs/workshops/pom

[Ace]

Mars has perchlorate. These can be used as oxidisers in solid boosters. It may also be possible to extract oxygen from them. Methane may even be able to burn perchlorate.

Microorganisms exist that produce oxygen from perchlorates. Since the percholorates (Ca & Mg salts, not the acid) will have to be removed from water anyway, it would certainly be better to do something like that than to just have them pile up as a kind of toxic waste.

On the CO2 side, obviously the atmosphere is the most accessible source. From what I've read, freezing and re-thawing seems to be a good way to extract and purify it. However, I've been wondering whether carbonates might be also be a good source. Carbonates from hydrothermal precipitation have been detected on Mars. Mixing them with even a mild acid should release CO2 gas. The obvious follow-up question is how to make a mild acid given the materials available.

[Ace]

I’ve thought for years that SpaceX would be wise to start testing sabatier hardware by making their own fuel for Raptor and SS/SH.

Get some solar panels from Tesla build a couple reactors and start will some veto tanks at the launch sites.

Yes, absolutely! There's no reason basic reactor flow and function shouldn't be ironed out on Earth long before use on Mars. Issues such as operating at scale are likely to present significant engineering challenges.

[KelvinZero]

There have been several conversations about this before on the forums, here is one:
ISRU Sabatier; Cost of fuel on Mars (power & water excavation)

Offtopic but this is a problem I have always noticed with the forum format. There have been some really good threads here on things like what we really know about radiation risks or the real world trade offs of atmospheric pressure and partial pressure of oxygen.. but they all fade or the nuggets become buried. The useful data does not naturally accumulate in an easily referenced form.

Im always thinking there is some format, like a wiki format with discussion threads only in the background?, or perhaps automatic indexing of popular posts and references, that would just ace this problem.

[lamontagne]

There have been several conversations about this before on the forums, here is one:
ISRU Sabatier; Cost of fuel on Mars (power & water excavation)

Offtopic but this is a problem I have always noticed with the forum format. There have been some really good threads here on things like what we really know about radiation risks or the real world trade offs of atmospheric pressure and partial pressure of oxygen.. but they all fade or the nuggets become buried. The useful data does not naturally accumulate in an easily referenced form.

Im always thinking there is some format, like a wiki format with discussion threads only in the background?, or perhaps automatic indexing of popular posts and references, that would just ace this problem.

I agree, and have no automated solution.  But I have started integrating what I manage to gather from the discussion into the Marspedia Wiki.  So some of the Sabatier data has found its way there.

https://marspedia.org/Sabatier/Water_Electrolysis_Process

It's a pretty hands on and work intensive process, of course. There is a Spacepedia wiki, maintained by the same group. but with, apparently, less active leadership.  It's not very full and would certainly benefit from input from the people in this forum.

http://spacepedia.wiki/index.php?title=Home

[lamontagne]

Another chemical reaction worth noting:

Olivine (Fe,Mg)SiO4 has been reported as being a common component of Martian regolith in the form of basalts, at least in the Southern Highlands. Olivine is an igneous, ultramafic or mafic mineral that's also readily available on Earth, either in aphanitic (small crystals) form as a basalt, or phaneritic (larger crystals) as peridotite or gabbro.

The interesting part is that when olivine is mixed with H2CO3 (carbonic acid), it forms oxygen gas and water. Carbonic acid is easy to make by bubbling CO2 through water. The reaction would allow you to recycle the water, while also generating oxygen. Should take a lot less energy than electrolysis.

The downside is that you still need hydrogen for the Sabatier process, which suggests olivine might be best used as a secondary oxygen source -- but even in that role, it could still be very useful.

That's interesting; if you could find methane on Mars, it might be the cheap way to get oxygen to go with it?
However, a bit of digging suggest the rate may be quite slow, and the amount of carbonic acid held in water quite small?  Catalysts perhaps?  This does sound a bit too magical, if it was that simple, there would be no CO2 problem and therefore no global warming problem....

[A_M_Swallow]

An alternative to burning methane is to burn carbon monoxide. This removes the need to obtain hydrogen.

2CO₂ => 2CO + O₂

[wannamoonbase]

An alternative to burning methane is to burn carbon monoxide. This removes the need to obtain hydrogen.

2CO₂ => 2CO + O₂

All you need to find or take to Mars is Hydrogen.

2H₂ + CO₂ => CH4 + O₂

It is a lovely balanced equation.  We'll find the water below the surface eventually, until then it's the least amount of mass to take with.

[lamontagne]

An alternative to burning methane is to burn carbon monoxide. This removes the need to obtain hydrogen.

2CO₂ => 2CO + O₂

All you need to find or take to Mars is Hydrogen.

2H₂ + CO₂ => CH4 + O₂

It is a lovely balanced equation.  We'll find the water below the surface eventually, until then it's the least amount of mass to take with.

It's lovely but it doesn't work that way.  4H2+C02=Ch4 +H2O is what happen in real life.  So you will bring a lot of hydrogen to produce water.  That is the Sabatier reaction.

You can electrolyse that water to produce more hydrogen, and combine it again with CO2 and eventually use up all the hydrogen.  But you will need quite a bit of power.

Plus, for a Starship, you need 240 tonnes of return fuel.  CH4 is 12C and 4H for a total of 16 so 240/16*4= 60 tonnes of hydrogen, plus the hydrogen tank.  60 tonnes of hydrogen is 850 m3.  So you have very little place left for anything but the hydrogen in Starship.  And you get leaks, as hydrogen is very leaky.
Better to bring extra solar panels, to produce your hydrogen in-situ.  Mars is lousy with water.

[LMT]

CAVoR

One existing system:  Carbonaceous Asteroid Volatile Recovery (CAVoR), provisional patent application:

Berggren, Mark, Boris Nizamov, Robert Zubrin, and James Siebarth. "Methods and Apparatus for Recovery of Volatile and Carbonaceous Components from Unconventional Feeds." U.S. Patent Application 15/861,557, filed July 12, 2018.

Hallmarks:  CAVoR processes carbonaceous ices, thereby avoiding the energy expense of martian ambient atmosphere compression.  The same hw would run on Mars, moons, asteroids and comets. 

Benchmarks:  mass numbers in Fig. 9 and Table 13, thermal power numbers in Tables 14 and 15.  Caveats:  A CO2-rich clathrate lacking hydrocarbon would give less reformer H2 for methanation than assumed in Table 14 (5 wt% hydrocarbon feed).  More water would be processed, raising electrolysis electrical power requirement.  See [0157].  Also Table 14 assumes 80 wt% inorganic inert asteroid matter; material with less rock would be processed with lower thermal energy input.  See [0033].

Prospects:  CO2-rich clathrate ices should be stable on Mars within 10 m of the surface at many mid-latitude sites, where found in ice-cemented soils, glaciers, ice lenses or crater-fill ice.  Any such CO2 clathrate would be a candidate CAVoR feedstock.

[Rondaz]

Carbon dioxide converted to methanol using 'artificial leaf' process: Study

The Canadian Press Liam Casey, November 4, 2019 12:06 PM EST

Last Updated
November 4, 2019
12:07 PM EST

https://nationalpost.com/pmn/news-pmn/canada-news-pmn/carbon-dioxide-converted-to-methanol-using-artificial-leaf-process-study

[Twark_Main]

Another chemical reaction worth noting:

Olivine (Fe,Mg)SiO4 has been reported as being a common component of Martian regolith in the form of basalts, at least in the Southern Highlands. Olivine is an igneous, ultramafic or mafic mineral that's also readily available on Earth, either in aphanitic (small crystals) form as a basalt, or phaneritic (larger crystals) as peridotite or gabbro.

The interesting part is that when olivine is mixed with H2CO3 (carbonic acid), it forms oxygen gas and water. Carbonic acid is easy to make by bubbling CO2 through water. The reaction would allow you to recycle the water, while also generating oxygen. Should take a lot less energy than electrolysis.

The downside is that you still need hydrogen for the Sabatier process, which suggests olivine might be best used as a secondary oxygen source -- but even in that role, it could still be very useful.

That's interesting; if you could find methane on Mars, it might be the cheap way to get oxygen to go with it?
However, a bit of digging suggest the rate may be quite slow, and the amount of carbonic acid held in water quite small?  Catalysts perhaps?  This does sound a bit too magical, if it was that simple, there would be no CO2 problem and therefore no global warming problem....

No magic. There does exist a proposal to combat climate change by artificially accelerating the weathering rate of olivine. https://projectvesta.org/

[Joseph Peterson]

Here are two technical points about electrolysis stacks that I have previously discussed in other threads linked above.

Water for the electrolysis stack needs to be purified.  Most companies trying to sell electrolysis stacks do so with a eye to hydrogen being the final product.  These use reverse osmosis for water purification.  Since our hydrogen is fed into a Sabatier reactor, an exothermic process, waste heat can be used for distillation, saving a lot of complexity.

Most companies trying to sell electrolysis stacks use a chiller system to ensure only hydrogen exits the hydrogen side of the electrolysis system.  As far as I can tell this is because chillers are the way we've always done it.  A simpler and cheaper option is to use membranes[1] to purify the hydrogen and metal hydrides[2] for pressurization and storage.

[1] http://www.tanaka-europe.eu/products/equipment-measuring-devices/palladium-membrane-for-hydrogen-purification/
[2] https://www.fuelcellstore.com/hydrogen-equipment/hydrogen-storage/metal-hydrides

[Genial Precis]

Silly basic questions here. There are clearly deposits of mostly-water at the poles, but if you want to use solar power you definitely don't want to be at the poles. Are there known deposits of high-quality "water ore" at latitudes with reasonable insolation? If not, what are some options if you want to extract water from some lower-quality ore such as a hydrate mineral, and are there some reasonable deposits of those near the equator? I've done a little research but not found anything clear-cut on these issues.

[Mark K]

Silly basic questions here. There are clearly deposits of mostly-water at the poles, but if you want to use solar power you definitely don't want to be at the poles. Are there known deposits of high-quality "water ore" at latitudes with reasonable insolation? If not, what are some options if you want to extract water from some lower-quality ore such as a hydrate mineral, and are there some reasonable deposits of those near the equator? I've done a little research but not found anything clear-cut on these issues.

High areas around the poles are where you definitely want to be for Solar Power on the moon. You get better than every other fortnight insolation. If you are very near the pole only a few stations will keep you having one always in Sun and there is no air to attenuate at low angle.

[Genial Precis]

High areas around the poles are where you definitely want to be for Solar Power on the moon. You get better than every other fortnight insolation. If you are very near the pole only a few stations will keep you having one always in Sun and there is no air to attenuate at low angle.

Uh, I was asking about Mars. TBH putting solar panels on the moon sounds silly, in the long run. The moon is super dusty, and it's relatively easy to ship things in and out of lunar orbit with various fixed installations, so it's probably more cost-effective to put solar panels in orbit and beam power down as soon as you get to a large enough scale to support launch infrastructure.

[high road]

If you think the moon is so dusty it would reduce overall solar power effectiveness by more than the 40% you lose by SBSP power conversions, why would you go with solar power on Mars? Plenty of dust + an atmosphere to carry it.

However, a methane plant on the moon would need a source of carbon dioxide

[Genial Precis]

The moon doesn't have winds to blow dust around, but that's OK because the dust electrostatically levitates! There's a carpet of hovering dust on the moon, and it clings to everything because there's no atmosphere to dissipate charges. You have to account for the dust on Luna and Mars.

If you can easily put things in orbit around the moon, and at a certain scale of settlement this could well be the case, it might be cheaper per unit delivered power to eat the inefficiency and put more solar panels in a dust-free environment. Especially since the solar panels in orbit can produce most of the time, so 60% transmission losses is not such a big hit.

Oviously I don't know if this works out, but there you have it.

[LMT]

...a methane plant on the moon would need a source of carbon dioxide

Some useful carbon source, yes:  e.g., potential endogenous and exogenous sources for carbonaceous lunar ices.

Lunar ice is OT in Mars context; still, refinery methods could be much the same, especially if CO2-rich clathrate is present in martian ice.

[sdsds]

Regarding the off-the-shelf cake mixer they use in their Sabatier process: "We voided the warranty pretty thoroughly."

https://twitter.com/freethinkmedia/status/1895193498107916772

[Slarty1080]

I’ve thought for years that SpaceX would be wise to start testing sabatier hardware by making their own fuel for Raptor and SS/SH.

Get some solar panels from Tesla build a couple reactors and start will some veto tanks at the launch sites.

Yes, absolutely! There's no reason basic reactor flow and function shouldn't be ironed out on Earth long before use on Mars. Issues such as operating at scale are likely to present significant engineering challenges.

Testing will definitely be required for the specifics on Mars, but the basic chemistry and the process is very well known in the chemical industry it's gas light era technology and not something exotic. The main challenges will be in getting a good supply of pure water and enough power for electrolysis. The reaction itself is exothermic so will be self sustaining.