Clean hydrogen at a crossroads: Why methane pyrolysis deserves attention | Hacker News Reader

Clean hydrogen at a crossroads: Why methane pyrolysis deserves attention

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34 pointsgeorgecmu54 comments

Never trust anything written by lawyers/economics/MBAs on climate change - only analysis by chemical or mechanical engineers is worth reading.

Methane pyrolysis is an old technology from early days of oil refining for production of hydrogen & Ammonia/fertilizer/Methanol. it yields half as much H2 than SMR/ATR so it can't compete on cost, unless there is carbon tax/CO2 penalty. Also, coke produced by pyrolysis is lower quality than that produced by Delayed Coking of crude oil refining.

Most of the comments seem to confuse pyrolysis (no O2) with reforming (H2O), which produces CO2. ATR uses partial O2 & H2O and is more energy efficient & cheaper.

Commonsense should tell you e- generated by H2 can't compete with CH4, because Ch4 is the feedstock & H2 is the product!

Never trust anything written by lawyers/economics/MBAs on climate change - only analysis by chemical or mechanical engineers is worth reading.

Just so we know if we should keep reading, which one are you?

It's not appropriate to call it "technology," in the same way it's not appropriate to call "combustion" a "technology." There's a very wide variety of technological solutions to realize this family of chemical processes, and some are going to be better than other, depending on the use case or scenario. The report actually covers those pathways reasonably well.

Also, coke produced by pyrolysis is lower quality than that produced by Delayed Coking of crude oil refining.

Ideally, you would not be producing coke at all, but a higher value material. However, even coke will be of much higher purity than petcoke (before calcining) -- i.e. it would be intrinsically zero-sulfur carbon material, - but I'm not sure what applications it would have that don't involve production of CO2.

But obviously the carbon co-product should have value, which would provide a cost offset to the hydrogen. With a high-quality co-product (> $1/kgC), this offset would be significant enough to provide that hydrogen essentially free of charge.

SMR and ATR generate significant amounts of CO2 (~10 kgCO2/kgH2), which does not provide a cost offset, and in a fair world would instead incur a significant added cost.

Electrolysis requires 4x more energy (also electric, not thermal) and does not have a marketable/valuable co-product. Just on the energy cost alone (50 kWh/kgH2 * 0.12 USD/kWh = 6 USD/kgH2 > 40 USD/MMBTU) electrolyzer hydrogen is not competitive with any of the above.

Commonsense should tell you e- generated by H2 can't compete with CH4, because Ch4 is the feedstock & H2 is the product!

Didn't parse this statement, sorry. Can you rephrase?

> > Commonsense should tell you e- generated by H2 can't compete with CH4, because Ch4 is the feedstock & H2 is the product!

> Didn't parse this statement, sorry. Can you rephrase?

They might have meant something like: if you process A through B to C while you could also process A to C directly, then the latter direct process will usually be more economically viable.

While this heuristic sounds broadly reasonable, it neglects so many details of any real production processes and value chains that it seems hardly applicable to real world situations.

> Never trust anything written by lawyers/economics/MBAs on climate change - only analysis by chemical or mechanical engineers is worth reading.

> Methane pyrolysis is an old technology from early days of oil refining for production of hydrogen & Ammonia/fertilizer/Methanol. it yields half as much H2 than SMR/ATR so it can't compete on cost, unless there is carbon tax/CO2 penalty.

Sounds like never trust anything written by chemical or mechanical engineers on costs, only economists/MBA :) ?

To be competitive on cost, not only the percent of used input should be taken into account, but also how much the one and another ways of processing are costing independently. If old technology methane pyrolysis produces half as much H2 but is quarter as cheap per unit of H2, it still wins whatever modern method is.

Interesting to see this on the HN front page. On the subject of methane pyrolysis, it turns out if you look at the Gibbs free energy calculation, about half of the energy of methane combustion is released from the formation of water, and the other half from the formation of carbon dioxide. That suggests that if you can be efficient with conserving the heat of pyrolysis, you can make a methane power plant that starts with a pyrolysis step to separate out the carbon atoms in an oxygen-free environment, and then burn the remaining hydrogen to power the cycle, and the end result would be a zero-emissions natural gas power plant. It would require twice as much gas to run, but if you can find a good value-added use for the carbon, it could potentially still be cost effective.

This would probably be much more efficient than doing pyrolysis to extract the hydrogen for use in electricity generation somewhere else, because you don't lose the substantial stored heat energy in the process of cooling that hydrogen back down.

And I can't help but wonder if fossil fuel companies might suddenly start endorsing aggressive zero-emissions targets if there's a way for this to double the demand for their products, rather than eliminating it.

> hydrogen for use in electricity generation

Hydrogen is way more valuable for chemical production, especially fertilizer. That would be a way to use the excess heat you mention.

On the subject of methane pyrolysis, it turns out if you look at the Gibbs free energy calculation, about half of the energy of methane combustion is released from the formation of water, and the other half from the formation of carbon dioxide.

About 70% of the energy is in hydrogen, 30% is in carbon. 1 GJ of methane weighs about 20 kg, 5 kg of which comprise hydrogen. At 142 MJ/kgH2 (higher heating value, which implies condensation of the produced water), 710 MJ out of that 1 GJ is due to hydrogen.

With a 60%-70% efficient hydrogen fuel cell, about 50% of the electricity generated from hydrogen from pyrolysis of methane would drive the process, and 50% could go into the grid.

You have to account for the energy required to break the bonds of the CH4, though. This means if you burn methane the usual way you get (CH4 + 2O2 --> CO2 + 2H2O + 803 kJ/mol); if you burn it with an ideal zero-emissions reaction, you get (CH4 + O2 --> C + 2H2O + 409 kJ/mol), or just a little more than half the energy from the same gas.

Your accounting works if someone else does the pyrolysis for you and you're left with just the H2 and C at the end, but mine includes the energy consumed by the pyrolysis step that breaks the methane molecule (albeit neglecting any thermodynamic losses, which there will be several -- for example you need to recapture the heat carried away by the hot carbon atoms). On the other hand, you can hardly wish for a better feedstock for CVD diamond production...

It requires more input energy, but it's been really good to see electrolysis of H2O for hydrogen generation take off. There are honestly industrial/grid scale operations actually starting now (as opposed to being constructed). E.g. Aces Delta in Utah. 220MW of wind/solar as input (i.e. equivalent to power for a medium sized city) As a disclaimer, my wife works on that project, but I think it's incredibly cool regardless.

Pyrolysis is a less energy intensive way to produce hydrogen, and does deserve more attention. But it still requires methane as a feedstock.

Hydrolysis let's use use hydrogen as essentially a fixed loss battery. It's perfectly complimentary to seasonally variable renewables like wind and solar. Batteries have too high of a loss though time for seasonal or multi-year storage. If you can store it (big if... Not everywhere has a salt dome like Delta, UT), hydrogen really is a great solution.

Pyrolysis is a less energy intensive way to produce hydrogen, and does deserve more attention. But it still requires methane as a feedstock.

So why is methane as feedstock a problem?

Isn't it better to spend less energy convert a ubiquitous, but environmentally harmful gas into hydrogen along with useful materials, than spend 4x more energy to convert a critical resource -- fresh water -- into hydrogen without any valuable by-products?

Methane is not abundant, as such. There are specific sources of it, mainly through manual agricultural processes, or in natural systems. Natural gas is mostly methane, I guess.

Water is critical but not hard to get. The energy and cost required to take a m3 of dirty water and turn it into pure water is a rounding error compared to the energy required to hydrolyze it.

Yes methane is an environmental problem, even small methane leakages have a large GHG impacts. But the best way to deal with that environmental problem is to not pull it out of the ground in the first place

Plus for pyrolysis, you have to deal with the carbon which makes up 75% of the methane by weight. A non-trivial issue.

Water is critical but not hard to get.

Right. https://en.wikipedia.org/wiki/Water_scarcity

You would want to use solar power for electrolysis. In the US, regions with abundant solar power are also the ones that: - have true water scarcity - Nevada and Arizona - have low population and industrial density, so any generated hydrogen would need transported to the point of use.

The bigger problem is the energy disparity. Electrolysis of water requires 50 kWh/kgH2 or more. Even a 70% efficient fuel cell would get ~25 kWh/kgH2 -- horrible roundtrip efficiency. With pyrolysis, that equation is exactly inverted: at 9-12 kWh/kgH2, you can generate excess electricity with no CO2 emissions.

Plus for pyrolysis, you have to deal with the carbon which makes up 75% of the methane by weight. A non-trivial issue.

Exactly. 20 kg of methane costs $3 today, but contains 15 kg of carbon that could be worth $20-$30. It's a non-trivial issue if you hate generating value.

https://www.chemanalyst.com/Pricing-data/carbon-black-42

A lot of those countries with water scarcity are oil rich. A lot of those countries that don't have water scarcity are oil poor.

Seems one forward step would be for countries that have an abundant source of alternative fuel to go for it and stop importing so much oil. Countries that don't have much water can import alternative energy sources or keep using the oil that they're rich in.

> In the US, regions

First of all the US isn’t the whole world.

Like you said transportation is a problem which is why you would produce it close to where it’s needed (say Nebraska). You don’t need an “ideal” solar output location.

Yes I am well aware of the energy difference.

> Exactly. 20 kg of methane costs $3 today, but contains 15 kg of carbon that could be worth $20-$30. It's a non-trivial issue if you hate generating value

If carbon free hydrogen is going to be worth doing at scale it will be because there is a price on the carbon. So the input methane will go up in price.

As for the output, global demand for carbon black is currently ~14 million metric tones a year [0].

Current hydrogen demand is ~100 million metric tones a year [1].

100 Mt of hydrogen needs ~400 Mt of methane and produces ~300 Mt of carbon.

300 Mt vs 14 Mt of current demand. What do you supposed will happen to that carbon black price when you produce even a fraction of total hydrogen demand through pyrolysis?

It’s non-trivial cause you’re gonna be having to create reverse coal mines to store all that shit.

[0]: https://www.chemanalyst.com/industry-report/carbon-black-mar...

[1]: https://www.iea.org/reports/global-hydrogen-review-2025/dema...

Except we already pull it out of the ground, and people are heavily invested in that process. Working with what we have is the best option here: far easier to enthusiastically go after methane leaks when the industry is otherwise being told "we will buy a lot of your product forever.

Which is really the stakes here: if you can "burn" fossil fuels without putting GHG in the air...there's no reason to stop using them at all. In fact we should vastly expand their use.

Why would the go after me than leaks if they know people will by their products?

A lot of the methane leaks are not “leaks” but intentional releases to “protect” equipment or to simply get rid of it. Until there are fines on the pollution it won’t stop.

> So why is methane as feedstock a problem?

There is inevitably leakage, and if even a small fraction does that it negates any global warming advantage on relevant timescales.

Methane in the form of natural gas is piped all over almost every city in North America, at least those areas where people need to heat their homes in the winter.

Any leakage from a pyrolysis plant is going to be negligible compared to what's undoubtedly already leaking from gas infrastructure installed in the 1950s (or earlier), as well as the continual accidental leaks caused by excavating.

Yes, leakage of methane for direct use is also a problem. Especially problematic is leakage upstream, near the wellheads.

I tend to be a fan of methane for its high hydrogen content per unit carbon as well as how much easier it is to store than hydrogen. However the argument against methane that I do find convincing is that the infrastructure for transporting and distributing methane leaks a lot. The argument is most compelling against residential distribution, where maintenance is harder to justify, but large leaks regularly occur, and that is very bad for greenhouse emissions.

I’ve always been curious about generating methane in industrial composting or from landfills and using it onsite for hydrogen generation. Not sure if the generating capacity is enough though, there is probably a reason it isn’t being done.

An under considered side effect of adding renewables to the grid is that electricity prices occasionally approach zero during times of over production. No reason not to use that energy for electrolysis its going to be wasted otherwise.

The problem with electrolysis is the high capital cost. As long as / where the price of electricity near zero only some of the time, it is too expensive. (With batteries and more photovoltaics this might change a bit.)

This comes up on a regular basis in the discussion around hydrogen, sometimes it's also known as turquoise hydrogen. The claims made here are very misleading, let me quickly explain why.

The idea here is that you make hydrogen from fossil methane by splitting it into hydrogen and carbon. Now, the claim is that you now have "clean" or "climate neutral" hydrogen. But it's made from fossil gas, and there's carbon. If you would now bury that carbon or do something else that guarantees that carbon never ends up in the atmosphere, ok, you might claim that. (Still with caveats: your fossil gas production has upstream emissions you need to account for.)

But that is not economically feasible. So the idea is: sell that carbon as a co-product. But now, that carbon will in almost all cases eventually still end up as CO2 emissions. But these pitches never talk about that. Claiming that hydrogen is "climate neutral" is, then, more an accounting trick. If you are honest, you would have to do something like associate half of the eventual emissions to it.

I wrote about it in more detail before: https://industrydecarbonization.com/news/the-problem-with-tu...

Some back of the envelope calculations from fellows I work with suggested that the waste heat from a single gas turbine exhaust could supply enough H2 for 3 gas turbines - so a CC power plant with 3 gas turbines, 2 with standard HRSGs that use the exhaust gas to run a steam turbine, and the 3rd using the exhaust heat to run a methane pyrolysis process, would be the preferred configuration. Slightly less efficient, but 0 carbon emissions. The biggest issue would be running the plant at varying loads - you would need storage for excess H2 to run more efficiently.

Hydrogen isn’t “clean” in any sense and I dislike that adjective is used so commonly with hydrogen.

When burned in air it produces far more NOx than burning methane due to higher temperatures. For example, one popular idea (hydrogen blending - HENG) is to mix it into the natural gas people burn in their homes. But burning a 15% hydrogen blend leads to a ten fold increases in health damaging NOx over burning natural gas.

And leakage during transportation is much worse than NG - particularly in liquid form. Combined with fact that leaked hydrogen is an extremely potent (indirect) greenhouse gas with more and more studies arriving at a number between 10 and 13 for its GWP100 (https://cicero.oslo.no/en/hydrogen-leaks-add-to-global-warmi... for example).

Hydrogen isn’t burned in fuel cells, though? So hydrogen used in fuel cell, such as hydrogen powered vehicles, is indeed clean.

Sure - but I wasn’t claiming that consuming it always produced huge amounts of NOx - I was pointing out that having hydrogen involved doesn’t make a process “clean”. And burning hydrogen in air is being pushed/proposed - not just domestically in the form of hydrogen enriched NG but also for grid scale electricity generation in gas turbines.

Splitting methane to get hydrogen and carbon seems like exactly the wrong direction to move. Just because we like the idea of hydrogen fuel?

It's a great move! Methane economy already exists. Methane storage and transport is reasonably simple and scalable.

Convert to hydrogen at point of use, and you can claim all the hydrogen hype without having to do all the hard things with hydrogen. If you accidentally oxidize methane instead of converting to hydrogen and oxidizing hydrogen, whoopsie-doodles, but it might be a simpler system.

Sure, but how is methane obtained if not from a byproduct of drilling up oil? Isn't it the "gas" in oil&gas?

It's probably a good move to "hydrogenize" the economy if we can, but it sure would be nice to move away from extraction into something that's more sustainably produced in-situ. Either electricity, or even methane synthesis.

We will always need some oil in near future. And gas is considered a byproduct only because oil is more economically attractive. It is technically perfectly feasible to obtain gas only and leave oil in the ground.

Why is it the wrong direction? It seems to me to be the perfect direction, if we can make it happen. Methane is plentiful and cheap. If we can burn it without emitting CO2, what's not to like?

What's the actual point of doing this? This is another sneaky fossil fuel "idea" that just wants to make sure their product is still required in the electrified future. Hydrogen isn't an energy source, it's a storage medium. It compares poorly to batteries is a variety of use cases, fuel cells can be a consumable component, and you have to deal with storing the hydrogen before you convert it to electricity or burn it (have fun assembling all of those parts for a combustion engine).

I get it - it's cool science and there's probably a couple of edge cases or whatever where this does make sense, but solar panels, batteries, and electric motors are all here and mostly work. The technology for all of that will continue to get better and make any hydrogen use cases even less practical. Just leave the oil in the ground.

> What's the actual point of doing this?

Hydrogen is heavily used industrially, and today the most common and economical way it is produced is via steam reforming of methane, which emits CO2 as a byproduct. This method has the benefit of outputting solid carbon instead of CO2 while still being economically viable unlike most other ways of generating hydrogen.

In this case hydrogen is an energy source. You split CH4 into C and 2H2, put the solid carbon in some storage, and either burn the hydrogen in a regular power plant, or you put it in a fuel cell. Either way, you generate electricity. With methane pyrolysis, hydrogen is not a storage medium, it becomes a regular fuel.

We already need carbon black, graphite, etc. This process makes production have dramatically less carbon emissions with hydrogen as a bonus. Of course we use millions of tons of hydrogen for things like fertilizer. What's not to like?

Exactly right.

Carbon black has the average CO2 intensity of almost 4 kgCO2/kgC [1] and its conventional production is so dirty and low-margin, that companies have been walking away from their plants rather than implement EPA-mandated upgrades. [2]

[1] https://static1.squarespace.com/static/5fd161c5b1bc2872873bd...

[2] https://www.ledger-enquirer.com/news/business/article2703292...

The other commenters are myopically, dangerously wrong in the worst possible way. We must stop pulling carbon out of the ground yesterday. Climate change isn't a hoax, isn't going away, and is an existential crisis that must be addressed by eliminating carbon extraction to the greatest degree possible sooner rather than never.

Pulling carbon out of the ground doesn't cause climate change. Neither does consuming energy. Burning carbon into CO₂ or releasing other carbon-bearing gases like CH₄ or C₂H₄ causes climate change. Methane pyrolysis avoids that. Too bad it's uneconomic next to solar panels.

leaking methane definitely does though, and pretty much all natural gas pipelines and facilities are leaking it at levels way higher than producers care to admit

You're not wrong, but you're not right either.

In 2015, the Department of Energy estimated that the CO2 footprint for production, processing, and pipeline transportation of natural gas averaged between 8 and 14 kgCO2-e per MMBTU of natural gas [1].

The average natural gas CO2 emissions (kgCO2/MMBTU) has been going down over time [2], and will be reduced even further in the next few years thanks to increasing fines [3] on one hand and financial incentives to reduce flaring and venting [4] on the other hand. A large percentage of these emissions are not due to accidental leaks, but are essentially intentional -- due to flaring, venting, and high-bleed controllers and actuators [2].

For an idea of how much emissions can be reduced, consider that the so-called certified gas has 90% lower CO2 footprint than the average today [5]. For example, the methane emissions for a natural gas utility in Oregon are 90% lower than EPA nationwide assumptions [6].

[1] https://greet.es.anl.gov/files/EERE-LCA-NG

[2] https://www.epa.gov/ghgemissions/inventory-us-greenhouse-gas...

[3] https://community.citizensclimate.org/resources/item/19/530#...

[4] https://www.epa.gov/inflation-reduction-act/methane-emission...

https://www.epa.gov/sites/default/files/2020-04/documents/us...

[5] https://www.cfindustries.com/newsroom/2023/bp-certified-natu...

[6] https://www.nwnatural.com/about-us/environment/less-we-can

Serious cognitive dissonance and strawmanning. Using the sky as an open-air sewer does. No amount of "clean coal" or "clean hydrogen" will change the problem of normalization of continued ff extraction by greenwashing it.

You don't seem to have addressed my argument, and parts of your response aren't even coherent, such as "Using the sky as an open-air sewer does." Possibly you are too upset to have a conversation successfully right now.

> Be kind. Don't be snarky. Converse curiously; don't cross-examine. Edit out swipes.

> Comments should get more thoughtful and substantive, not less, as a topic gets more divisive.

> When disagreeing, please reply to the argument instead of calling names. "That is idiotic; 1 + 1 is 2, not 3" can be shortened to "1 + 1 is 2, not 3."

> Don't be curmudgeonly. Thoughtful criticism is fine, but please don't be rigidly or generically negative.

> Please don't fulminate. Please don't sneer, including at the rest of the community.

> Please respond to the strongest plausible interpretation of what someone says, not a weaker one that's easier to criticize. Assume good faith.

https://news.ycombinator.com/newsguidelines.html

Yes, if you begin to follow these guidelines, you may find that ypur attempts to converse here are more successful.

The carbon extracted in this manner is a solid - carbon black, essentially graphite particles. It could be dumped in old coal mines and recovered - essentially burying the carbon we took out again.

Looks like you yourself are dangerously wrong here.

You know which way we will not solve the problem?

By failing to recognize technologies that are going to help solve the problem.

It's the same with CCS.

The "green" mantra of "this is all just a strategy to help the fossil industry survive and we must boycott it" is shooting in one's foot.

As long as the world's energy infrastructure can not be built solely on renewables - which will still be the case in at least 2-3 decades - it makes sense to develop/use technologies that make the footprint of fossil energy smaller.

H² is unsolved.perenialy so.but oh so amazing on paper, some much energy in such a small package! and therein lies the problem, H² is so tiny that it is impossible to contain. It goes strait through solid steel, and the pumps and hose'es to move it from storage to tankage in a retail environment are yet to be proven, even NASA and other rocket companys still have cancelations due to leaks. And sure H² is used in large enough quantities in industrial settings,but those in no way reflect any way of implimenting retail domestic sales and use. The notion.that we can take a hydroCARBON, and magicaly make it a clean fuel is a twist too far, and scheems like this regularly run there course where they end up bieng proven worse than just burning coal. The only green hydogen will come from the solar powered hydrolosis of sea water at some point after a number of experimental technologies under investigation now are developed and introduced at scale, which luckily, happens quite fast these days.

Monolith was the first mover here, they are making carbon black for Goodyear. Last year they were running into problems meeting targets for a $1B DOE loan, haven't seen if they've managed to get on track.

https://www.wsj.com/business/energy-oil/a-high-profile-clean...

Is there some reason this wasn't done 100 years ago? 50? 30?

Methane outgassing/flaring from oil extraction operations has been going on the entire time we've been oil drilling. Why didn't the oil companies extract this resource?

And who is c3es? Wikipedia says they are a rename from the Pew Center for Global Climate. It may be a logical fallacy to question the motives of an argument, but it isn't a policy fallacy to know the motives.

If there is a good, easy way to generate methane using atmospheric CO2, then, we could have a chemical battery in the form of methane, which is far easier to handle than Hydrogen.

But I wonder what the round trip efficiency of such a system would be. Current lithium batteries have it at around 80%

The key feature of hydrogen as energy storage wouldn't necessarily be round trip efficiency but cost effectiveness (compared to batteries) of long-term storage over months.

Think about transporting peaks of renewables electricity generation that are not economically usable at the time when they're produced to times when renewables produce too little to meet demand. (Mostly in regions where generation depends significantly on seasons.)

Hydrogen is dead. It was a perfect example of green washing - even Greenpeace (Greenpeace Energy)(Green Planet Energy) was using it to greenwash import fossils to Germany from russia.

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