Fuel out of thin air: CO2 capture from air and conversion to methanol (2020) | Hacker News Reader

Fuel out of thin air: CO2 capture from air and conversion to methanol (2020)

research.american.edu

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Quick summary: "Given sources of Carbon and Hydrogen plus massive energy inputs, you can synthesize hydrocarbons!"

I feel like the headlines always try to pretend you're getting energy out of the CO₂ rather than putting energy into a hydrocarbon energy storage chemical.

Question of course is economics of converting some (hopefully clean-ish) energy into stored hydrocarbon chemical bond energy and then combusting it in a vehicle vs. just digging up hydrocarbons and combusting them.

I think it's totally plausible actually, there's lots of stranded renewables and otherwise flared natgas that could be used for this process

There are places you can get energy from to do this for sure. But you're still putting energy into an energy conversion, not getting energy out of CO₂. (Unless you're doing some kind of late stage stellar nucleosynthesis fusion, which... you're not)

The headline should be: "Fuel components from air synthesized into liquid fuel using energy from some other energy source"

An inefficient process is still infinitely more efficient than nothing.

I think there’s an opportunity to formalise an excess energy marketplace, established with an inefficient process to get the ball rolling. From there, market forces can dictate winners.

The big thing here is in theory we could put something like a nuclear plant(which people are afraid of) in a remote area and produce fuels we are already equipped to use from that pretty major energy source.

Combine that with Solar storage and geo-thermal storage using that and maybe we will continue to have enough movable energy to have long distance travel that isn't wind driven.

There is even talk of using a nuclear heat source to drive petrochemical transformations in China as well as the US

https://www.osti.gov/biblio/23032635

If you are producing fuels at remote location, solar in the sahara will be more cost efficient.

Thw whole advantage of nuclear over renewables is it's reliability for powering critical infrastructure

If you are producing fuels, they can be stored, reliability doesn't matter - only cost.

The flared natural gas is happening because it's too expensive to ship it away versus what it's worth. I'm not sure what you gain by burning the natural gas into CO2, and then converting it back into a hydrocarbon again only for it to again be marooned...

Very similar technology is used to turn CH₄ to motor fuels

https://en.wikipedia.org/wiki/Gas_to_liquids

they say

https://en.wikipedia.org/wiki/Pearl_GTL

in Qatar makes about 95 million barrels of liquid a year at $40 a barrel.

Well we might want to consider the externalities of "just digging up hydrocarbons and combusting them."

Of course, and we are. But let's not pretend there is free fuel floating around in CO2 as part of that consideration.

I think the primary idea is that eventually we'll still need carbon source inputs for making certain things (fertilizer for one, most types of rocket fuel for another) and so this is an alternative to that. If we're not getting hydrocarbons from fossil fuels, we need to get it from somewhere else for the petrochemical industry.

It's also a nice thing to do when the spot price of energy goes negative or extremely low when there's tons of surplus renewable energy.

I also heard one example assuming a future with nuclear fusion being cheap and you put a nuclear fusion plant at larger airports to produce jet fuel on-site.

You don’t need carbon for fertilizer. Hydrogen is harvested from methane which is added to atmospheric nitrogen to make ammonia, the basis for all nitrogen compounds used for fertilizers. You can change the process slightly to use other sources of hydrogen but they’re considerably more expensive. If you were synthesizing anyway, you would not take a detour to methane.

I wasn't suggesting that methane be produced.

What were you suggesting be produced for fertilizer inputs?

Biodiesel and ethanol (form corn, or better from sugarcane). Instead of a lot of tall gras, just imagine them as self-assembly solar panels with a mini chemistry factory attached.

Much less efficient than solar panels.

I guess you are comparing the efficiency of solar panels (20%) with the efficiency of photosynthesis (1%-2%). The problem is that solar panels have a 20% producing electricity, but using that electricity to make fuel has a very low efficiency.

From the article:

> When air was bubbled through potassium hydroxide dissolved in ethylene glycol and the CO2-loaded solution subsequently hydrogenated in the presence of H2 and a metal catalyst, complete conversion to methanol was observed at 140 °C.

Even with catalyst, organic reactions have an awful efficiency. In many of them the reactives produce not only what you want but also other molecules. In this case it's hard to imagine, because methane is very small and all side products I imagine like COH2 can probably be converted to methane inside a hot recipient full of H2.

Anyway, even if you lose no CO2 as side products, the reaction may lose a lot of energy as heat. Photosynthesis has many intermediate steps that help the conversion to be more efficient (and also because photosynthesis builds a bigger molecule that is harder).

The photosynthesis isn't the end of the biofuel equation. Corn ethanol is energy negative (switchgrass, sugar cane or beets are better but still abysmal).

If you consider a hybrid PV-CSP plant, the H2 step can be done at 20% from air. CO2 capture is under 10%.

So you'd need to show that the ethylene step is under 5% efficient when you also had an available free low quality steam input (or high quality at 50% sunlight-efficiency).

I almost agree. From https://en.wikipedia.org/wiki/Sugarcane#Ethanol

> One hectare of sugar cane yields 4,000 litres of ethanol per year (without any additional energy input, because the bagasse produced exceeds the amount needed to distill the final product). This, however, does not include the energy used in tilling, transportation, and so on. Thus, the solar energy-to-ethanol conversion efficiency is 0.13%.

but I'm still pessimistic about the efficiency of the new method.

The thing that will kill as an energy storage method it is capital and labour expenses more than efficiency. I'd expect something like it to be viable for chemical feedstock once the fossil fuel subsidies start to die out and less investment goes into extracting more and worse sources cheaply though.

Let me add another pair of goalposts here: Solar can be done without water

Much less efficient at producing watts perhaps, but less efficient at producing liquid, transportable hydrocarbons? I doubt it.

> fertilizer for one

Fertilizers don't contain carbon. Plants need nitrogen, potassium and phosphorus, which they can't easily get from their surroundings, so we provide these via fertilizers. They get their own carbon out of the CO2 in the air.

We do need hydrogen to make fertilizers, and currently the cheapest way to make hydrogen is to start with methane, CH4. But this is just a matter of convenience.

Yeah, these articles are consistently vague about the energy inputs and outputs of the process.

This isn't even a closed cycle. It uses up potassium hydroxide.

Electrolyzing water into hydrogen and oxygen is more promising, if you like that sort of thing. Once you have hydrogen, you can make hydrocarbons, if you want to. That's good to have as a technology for when we use up all the natural hydrocarbons and still want to make plastics. As an energy storage system, it sucks.

The described process relies on hydrogen.

Well they get some KOH loss, true, but that's why it's called industrial process development, those kinds of things can often be solved.

> "When air was bubbled through potassium hydroxide dissolved in ethylene glycol and the CO2-loaded solution subsequently hydrogenated in the presence of H2 and a metal catalyst, complete conversion to methanol was observed at 140 °C. Moreover, regeneration of the hydroxide base occurred at mild temperatures of 100-140 °C. Notably, a fraction of the base was deactivated in an unwanted side reaction. Currently, the researchers are aiming to minimize the side reactions to efficiently recycle the potassium hydroxide."

Having to use large volumes of ethylene glycol might be an issue, however. There's a whole literature on this particular reaction, for example, as of 2019:

https://www.frontiersin.org/articles/10.3389/fenrg.2019.0008...

> "The methanol production from direct CO2 (using pure sources of CO2 and H2) has several advantages over the conventional process—it results in significantly less byproducts, and requires less energy in product purification (Marlin et al., 2018). However, the methanol production cost via direct CO2 hydrogenation is 2–2.5 times higher than the cost of conventional process (Atsonics et al., 2015)."

The advantage is you can apply the past 100 years of organic chemistry development to specifically build whatever molecule you want without having to deal with separating out the desired hydrocarbon molecules from the complex glop called 'crude oil'. This is essentially what's going on in modern natural-gas-fed petrochemical facilities (although natural gas is often itself contaminated with sulfur and mercury species, like H2S / H2Hg etc.).

The disadvantage is that there's a high energy cost involved in stripping oxygen off carbon dioxide and replacing it with hydrogen (it is storing energy in C-H and C-C bonds). As the cheap easy-to-extract oil is mostly gone at this point, however, these costs are approaching parity.

The real necessary use cases of hydrocarbon fuels are for rockets and jet airplanes, as battery energy density is just too low. Long-distance oceanic shipping is another area where hydrocarbon fuels might be necessary, although there are some other options (wind/solar/iron redox).

> Long-distance oceanic shipping is another area where hydrocarbon fuels might be necessary, although there are some other options (wind/solar/iron redox).

Yeah, and nuclear, which is deployed at huge scale in seafaring vessels in the Navy. Merchant nuclear propulsion had an early start and is likely to see a revival imho.

https://en.wikipedia.org/wiki/NS_Savannah

https://corepower.energy/

https://en.wikipedia.org/wiki/Nuclear_marine_propulsion

Only if they can do it cheaper than the Navy. Nuclear isn't used because it saves on fuel. It's used because the operational advantages it bestows are worth more for the largest carriers and submarines than the extra cost it adds.

I agree that merchant nuclear-powered vessels will need to be cheaper than Naval nuclear-powered vessels. That is the goal. An international carbon tax or other credits for low-carbon/low-emission shipping would help.

Wow, I had no idea that there's currently a nuclear powered cargo ship in service: https://en.m.wikipedia.org/wiki/Sevmorput

I'd love to see it, but I'm a bit pessimistic about the political viability of a significant revival of civilian nuclear ships.

I was excitedly watching its journey down to Antarctica a few years ago. Sadly it had a propeller maintenance issue and had to turn around. :'(

A major reason military naval systems are efficient is that they don't need to be refueled very often - but that's because their fuel is highly-enriched uranium, bomb-grade HEU which 'burns' much cleaner (and can be diverted to an actual gun-type nuclear weapon, Hiroshima-type). That's just not going to happen with commercial shipping.

A commercial nuclear-powered cargo ship would have to be refueled on the same time scale as a commercial MOX or LEU reactor, likely raising costs quite a bit over any other fuel. Plus, what harbor would allow commercial nuclear reactors, given the costs of catastrophic failure, without ridiculously expensive levels of security and safeguards?

The major threat to a nuclear reactor is loss of afterglow heat cooling, which is extra unlikely when you're surrounded by water.

That said, one interesting approach is to use ocean-faring nuclear-powered tugs that basically stay out in international water and hand off massive container barges to little fossil fueled short-haul ones that can take it in to port where people are afraid of nuclear fission but don't care about air pollution or climate change.

As for refueling, it's true that submarines don't need to refuel for 30 years. But there's a lot more room on a container ship, so you can make a big core and run it at less than full power. This way you can get it to only need refueling every 5 years or so with low-enriched uranium. Not bad.

Nuclear tugs: https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1559-3584....

Or use battery for tugs given low duty cycle and access to shore

Ah yes that would actually be a great combo.

> Plus, what harbor would allow commercial nuclear reactors, given the costs of catastrophic failure

These ports already handle tens of thousands of tons of explosives - the blast in Beirut wa over 1 Kt of TNR equivalent, and all that ammonium nitrate arrived on a single ship. It was basically a small nuclear detonation.

How many billions did dredging all the Caesium out of the harbour and evacuating the entire area for a few months to avoid the Iodine plume from the nitrate explosion cost?

> As the cheap easy-to-extract oil is mostly gone at this point, however, these costs are approaching parity.

KSA can 10M bbl per day for 40 more years at $20...

It is an answer for the complaint "but solar doesn't work at night" and "transmitting energy over long distances is inefficient"

You see you could cover enough desert in Nevada with enough solar panels to provide 100% of the current electricity use of the United States. But you couldn't transmit it over the current grid to the rest of the country and it would "turn off" every night. So stupid right? Except maybe you are using that energy to create natural gas and you're shipping natural gas around through pipelines to standard gas electric power plants.

The math works, and the BLM has enough land (caveat the endangered tortoises) and so it is a "technically possible" solution to carbon neutral energy (you're taking CO2 out of the air and then returning it when you burn the natural gas).

This also works with fission power plants as the source of energy, and really shines with fusion power plants (fewer externalized issues like waste management).

In other words, given a solar or nuclear plant near a chemical / metallurgy plant, you can also produce some liquid fuels.

Or, if you're concerned with the climate impact of using fossil fuels, you can consider the economics of shifting to a technology that cab use the energy more directly; I.e, replacing aviation with electric railways.

Amen. Fuel out of thin air: CO2 capture from air and converted to methanol takes way more energy than can be recovered from the created fuel.

I've seen a bunch of these over the years; still waiting for one that will get traction. The changing cost of oil (mainly making externalities fiscally concrete) may change the equation.

The most interesting I ever ran across was people doing artificial photosynthesis to produce H2 and combustable oil, e.g. Nate Lewis' group at Cal Tech. Same problem: contemporary economics.

I'm glad people are still working on these problems.

>still waiting for one that will get traction.

There is one, got traction since millions of years..it's called trees:

https://www.britannica.com/science/methanol

>>wood alcohol, or wood spirit

Also, this Wikipedia article specifically discusses the use of methanol as a fuel: https://en.wikipedia.org/wiki/Methanol_fuel

Or wood gas. At the end of WW2 there were about 500,000 vehicles with wood gas generators in use in Germany to make up for the lack of other fuels.[1] But under today's conditions, this possibility does not seem to make economic sense.

[1] See: https://en.wikipedia.org/wiki/Wood_gas

Nora-Korea has still wood gas generators attached to cars:

Unfortunately it consumes a tree, which takes a while to replace. Better to be able to build a facility that can produce what you need on a continuous basis.

Interestingly I had to reword my comment (plant->facility and evergreen-> continuous) to avoid looking like I was trying to pun. Natural metaphors are a deep part of our thinking about the world.

Bamboo seems like an intriguing alternative to trees.

>Better to be able to build a facility that can produce what you need on a continuous basis.

Yeah see that's the wrong thinking of us humans. The best systems are those established by nature. Remove and bind CO2...yes trees and algae and shellfish have some million years of training in that.

Lets see this at scale..you need so many solar-panels that you already wasted mw's of energy, just to waste that energy for a process nature is already much better.

It just to make stocks and money...not to safe the climate, well maybe it's meant to make vodka in space-stations, then i am ok with it.

Terraform industries used to claim that their natural gas would be cheaper than local natural gas in 2027. They now say that the IRA has moved that timeline up to 2024.

https://terraformindustries.com/

The problem is energy conversion efficiency. Sure you can make synthetic jet fuel from solar panels, water and CO2 but the efficiency is miserable[1]. It's something like 4% efficient and the metal catalysts sometimes aren't cheap. I guess it's important to start somewhere and work on efficiency improvements until it makes economic sense.

[1]https://www.cell.com/joule/fulltext/S2542-4351(22)00286-0

As solar becomes cheaper and cheaper, low efficiencies may still be worth it. We're never going to power a 747 on solar, but if the energy in the fuel comes from the sun, even if 90% of that is "wasted," it's still greener.

Doing the process with standard technology will always be a PITA, partially because catalytic agents tend to not just be expensive but primarily sourced from questionable or enemy nations.

I think the eventual answer will be in genetically engineered microbes or plants, if only because it is easier to scale up vats with microbes and nature already has figured out synthesis paths for ages.

The 4% efficiency is starting from sunlight. This overstates the case, because any solar scheme wastes most of it. That doesn't mean solar energy is impractical, any more than the roughly 1% conversion (if that) of sunlight to food calories in a farmer's field would make agriculture impractical.

Also, that scheme is a thermochemical scheme for sunlight to hydrogen. Producing H2 gas by electrolysis driven by PV would be more efficient.

It's a common nuclear talking point that solar is impractical because of efficiency. This is a bogus argument, since comparing efficiency of schemes that use different inputs is comparing apples and oranges. Sunlight is cheap and abundant and can be wasted without intolerable pain.

I mostly hear nuclear talking points of the fact that it’s a guaranteed GW/year production versus intermittent weather-dependent allocation.

As if various storage schemes to deal with that don't or can't exist.

Energy storage at scales necessary to buffer solar/wind at 100% of the grid do not exist.

Nor does nuclear at the scale necessary to power the world. Today's commercial reactors can't do it; breeding is needed. This would mean scaling up breeder reactors by roughly a factor of 1000. This is actually a larger scaleup than would be needed for storage, I believe.

What, you're allowing nuclear to scale up, but not storage? Very high double standards you all have in Nuclearstan.

Breeder reactors are such an overlooked technology. Only Russia and India are seriously pursuing them. The thing about breeder reactors is they can get rid of the nuclear waste problem and use 100x the energy of the input fuel vs conventional reactors. It's much more technically complicated, and the biggest ones are only 800 megawatts right now, but they could conceivably go much larger.

How much Pu240 does the BN800 fission?

How much does it produce?

No breeder program has ever closed the fuel cycle, and the "closed" cycle doesn't even aspire to get rid of the fertile isotopes which will just be more high level waste.

What reprocessing does do though is let out all the Kr, Cs, Tc, T and so on that was safely contained in your spent fuel bundle. Much of which is just vented or dumped in the ocean.

How efficient is a leaf? Hoe is efficient is collecting and compressing algae for 40 million years?

The 4% efficiency number doesn't matter, because you get the sun light for free. What matters is how much such a system costs.

Which is where efficiency matters since the cap ex amortization is divided by production.

Lewis retired last month I believe.

I like this one: https://www.aircompany.com/products/air-vodka/

That is some beautiful eco-washing. Will definitely purchase for my pseudo-activist + vodka drinker friend.

The cost is steadily dropping (see this from 2018):

https://www.science.org/content/article/cost-plunges-capturi...

If someone asked me for a current cost calculation for a large-scale facility producing methane or methanol, off the top of my head I imagine it's still 5-10X as expensive as mined fossil fuels are. Economies of scale might bring that down to parity fairly soon, however.

A problem with ideas like these is that they have to be cheaper than burning fossil fuels and then capturing and sequestering CO2 to compensate. Both schemes capture CO2, so that part of the cost cancels out. Sequestering CO2 once you have it shouldn't be very expensive, especially if it can be used to stimulate more petroleum production.

If you're going to capture CO2 from the atmosphere it may be very favorable to do it at high latitude, where air is colder. I wonder if this could be sold to Russia as a way for them to make money in a post-fossil fuel world.

https://www.cell.com/iscience/fulltext/S2589-0042(22)01836-3

Capturing the CO2 is the most expensive part of the process.

Pumping fossil fuels out of the ground and then capturing and storing the resulting carbon is likely going to be more expensive then capturing carbon, synthesizing the fuel and burning the synthetic fuel. But in both scenarios capturing the carbon is the dominating cost so they're always going to be roughly comparable.

Who says the fossil fuel carbon will be captured? It's certainly not now and who says carbon capture is ever going to be enforced?

The only hope I have is that solar energy becomes so cheap that it can be profitably used to produce synfuel and so drive petroleum from the market. Actual regulation would be better but that seems as far as ever.

Who says solar energy can possibly get that cheap?

If you are skeptical of carbon capture being mandated by regulations then I think you should be equally if not more skeptical of the market restructuring itself so renewable energy based petroleum substitution becomes a reality spontaneously. It makes no sense economically or politically.

Why is fossil fuel carbon capture likely to be more expensive than atmospheric capture? The CO2 can be captured in a concentrated form directly from an exhaust so surely it has to be more efficient and thus less expensive.

From a very high level I wonder if we could use nuclear power to drive a CO2 capture mechanism to ‘make up’ for all the time spent burning fossil fuels instead of nuclear?

If we were willing to significantly overbuild nuclear power production capability yes, but from what I understand with current carbon capture efficiency it's more effective to have that nuclear power directly offset current energy consumption instead.

From a logical standpoint carbon capture is a scam [0]. The argument is "if you don't have spare energy, why are you spending it on carbon capture? And if you have spare energy (you don't), why not spend the money you usee to build the over capacity to bring clean energy somewhere else?"

That is all assuming your entire power grid is 100% clean (it isn't) because otherwise you fall in case 0 where you spend energy that could be spent on offsetting non-clean energy usage.

[0] https://youtu.be/nJslrTT-Yhc

It depends on the speed of capture. If you can capture faster than conversion reduces, and there are time constraints that mean reducing carbon now is better than later, then it can make sense.

It's the same as whether you should reduce expenses or increase income. Both yield a net increase, but there are variables than can make one better than the other in the short term. Whichever yields the most benefit for the effort is probably the best one, or if one has a time constraints and the other doesn't, that might be the best one to focus on.

Except that energy production is local, while carbon capture is global.

If you power a carbon capture device in Greenland using geothermal, you can probably get a lot more energy than you can reasonably give you the grid. In that case, using the rest for carbon capture makes sense.

Further, carbon capture is going to need to be part of our future mix, as we'll never be able to be 100% green in the reasonable future. It's good to spend a tiny percentage of our resources now improving the technology.

This videos shows the perverse mindset of climate activists that you "have to change your lifestyle" and personally suffer to solve the problem. It's a common refrain and erroneous, but here particularly so as only carbon capture, mechanical or natural, can fully solve the problem -- that is, there's already too much greenhouse effect and even an extreme agrarian lifestyle won't solve the problem.

Climate change is a problem nobody can personally solve and I think this personal suffering makes them feel like they're doing something.

The counterpoint is that energy can be difficult to transport, but the atmosphere dissipates carbon for free. So it might sense to do this where you produce energy, to use up extra energy which could be otherwise wasted.

I wouldn't go as far as to argue that it's a scam, I do think it's a complex issue which might require rethinking the way we geographically distribute infrastructure.

Carbon capture from the atmosphere is certainly extremely inefficient and not too practical (yet, at least), but carbon capture straight from large emitters like at factories should be much more efficient as it isn't having to go through as much air.

Combined with the difficulty of transporting electricity in many circumstances, carbon capture solutions which involve cleaning up the output from factories using something like an on-site small-modular reactor are probably a lot more practical. While of course the SMR would be better spent replacing a fossil fuel plant in the immediate term, in the longer term the output from the factory would also need to be cleaned up anyway.

So given enough serious interest in building SMRs/getting rid of fossil fuels, the temporary cost of allocating an SMR to carbon capture at a factory would be small compared to allocating it to replacing a fossil fuel plant (since another would be built soon enough to replace the latter).

So far, nobody needs a permit to capture CO2 from the atmosphere. You can harvest it without license, at any scale. Building a power line, possibly across international borders, is a logistical and bureaucratic nightmare.

Carbon capture is not a scam, but it is premature. It could make sense once fossil fuels are abolished, or at least we stop using them at fixed locations where CO2 can be captured without releasing it to the atmosphere.

There are many many many startups focused on this. If we engage in the amount of carbon capture that is predicted to be necessary in the second half of the century, we will be moving the same order of mass of air-extracted carbon to its fins resting place each year that we are currently moving for fueling. So a massive massive economy is expected to be built around this.

Nuclear power is unlikely to make financial sense as a source of electricity for this process. Many of the early pioneers were big supporters of nuclear for it last decade, but solar photovoltaic has made nuclear obsolete in comparison. I think the name of that startup was Carbon Engineering, bawd out of Canada... the founder was completely shocked at the advancement in solar, and at the time (a few years ago) thought that, by 2030, it would be possible to make liquid hydrocarbon fuels out of air+solar for roughly the same cost or lower as fossil fuels.

Originally, these types of systems relied not only on the electricity but also some of the heat output of the nuclear plant. If you’re having to do both with solar, then the efficiency is that much lower.

With that said, according to the abstract, this implementation doesn’t require excessive heat energy so you could probably get away with solar thermal for that bit.

Or because you don't need to do it on a schedule, just do it in a cold desert with high DNI like mongolia and use 60c/W thermal heliostats which are capable of higher temperatures for the heat rather than $4/W thermal nuclear.

> If we engage in the amount of carbon capture that is predicted to be necessary in the second half of the century, we will be moving the same order of mass of air-extracted carbon to its fins resting place each year that we are currently moving for fueling. So a massive massive economy is expected to be built around this

That whole uncosted industry is a fairy tale at this point. We dont gave political will to price carbon properly abd stop burning coal, there is no chance this industry will be funded

Your prediction does not take into account the cost of not building the industry.

Right now in the US, the political climate is completely irrational, unscientific, and hyper-partisan because one of the major parties has been completely bight off and brainwashed their followers into ignoring rational thought.

When the effects become more clear, and the actual costs of inaction become more clear, there is a good chance that humans will behave more rationally. Not certain, but it's a chance that we must plan for now.

I really hope you are roght, but I am not holding my breath

This would be a good investment once the grid is over 100% renewable. Until then, just use the renewable power for consumption.

Figuring out the technology so we'll be ready when we get there sounds like a good plan.

Using such a process on plain air is not likely to ever be economically feasible as air only contains a tiny amount of CO₂, around 400 parts per million. If you want to run such a process run it on the exhaust stack of a gas-fired power plant since that contains a good amount of CO₂. Of course this only makes sense if the capture takes less energy than the power plant produces which can not be the case since it would violate the second law of thermodynamics [1].

[1] https://www.britannica.com/science/second-law-of-thermodynam...

Well the good news is that every year that 400ppm goes up

>violate the second law of thermodynamics

This is directionally correct, in that coal emissions sequestration is unlikely to be economical, but with two caveats:

1) Most coals are not actually pure carbon, they do contain a small percentage of hydrogen. If you don't capture the resulting water vapor† then that gives you some combustion energy for free.

2) If you had to spend energy to split the carbon off CO2 and sequester the carbon, then yes, it would be a pointless round trip. Which is why most "clean coal" schemes just compress the CO2 and sequester it underground.

---

†: Water vapor is itself a powerful greenhouse gas, but it varies between 4,000 and 25,000 ppm, so clean coal, which is intended to be a short term stopgap measure operated only for a few decades until the global PV solar infrastructure is built out, shouldn't have time to affect global gas balances.

CO2 can also be sequestered by reaction with silicates to make carbonates. This process is mildly exothermic, if slow, and is how nature will draw down the CO2 we've been releasing, eventually.

Can you please explain why it violates the second law of thermodynamics? I thought the 2nd law would only apply if you are reversing the reaction, i.e. CO2 -> C + O2 , whereas we are simply moving the CO2 underground.

To me the critical measure would be how much energy the CO2 needs to be compressed to get it underground.

> Additionally, methanol, which is a liquid with a boiling point of 64.7 °C, is a superior fuel for internal combustion engines and fuel cells, as well as a convenient high density liquid hydrogen carrier. Methanol can be converted to ethylene and propylene through the MTO (methanol to olefins) process. Hence, the production of renewable methanol and the associated methanol economy holds significant potential to replace current fossil fuel-based economies.

No! Quite toxic. Don't want that around consumer-facing products. (Any more than in the engine coolant and wiper fluid it's already in)

Am I missing something? Isn't the need for hydrogen gas here a constraint?

It's either gonna be refined (steam reforming) or split from water.

H2 is necessary, yes. It can be provided by electrolysis of water, air captured if necessary.

Yeah that feels like it defeats the point. Not that I know the math, but it feels like there's a potential for it to be a net contributor of carbon emissions by encouraging more steam reforming of cng (and thus more cng pumping) or through power consumed to split water—power which invariably will come from dirty sources until we've done a better job moving away from dirty power.

I'd be curious to see someone graph out where this transitions from being carbon positive to being carbon negative (or vice versa)

No, e-Fuels like this are a way to make fuel from carbon free sources and that means splitting water to make hydrogen and sucking CO2 out of the air.

The navy is interested in making e-fuels from electricity on nuclear aircraft carriers since a gallon of jet fuel delivered to an aircraft carrier costs a lot more than a gallon of jet fuel delivered to a civilian airport and the aircraft carrier has to slow down a lot so a tanker it refuels from can catch up with it.

The point is not to get free energy. The point is to turn energy into hydrocarbon fuels that can be used without net carbon emissions, especially for vehicles that aren't easy to electrify.

Yes, this sort of thing is best thought of as a different sort of battery. You put energy in, and later get energy out. It's not a fuel.

If you could do it with solar power, it's sort of like free energy but no more than charging batteries from solar is. There are still infrastructure costs at minimum.

Potentially also as way of storing excess wind/solar generated energy

Here's a scale model of a methane production plant

https://twitter.com/TerraformIndies/status/15912554725728952...

If you burn gas to create gas, you end up with less gas than you started with. It'd be cheaper to burn dollar bills. It only works when the input energy is cheaper than the output energy. Right now solar and wind are the only energy sources cheaper than fossil energy.

The point is that methanol is a liquid which you can pour into a tank like regular gasoline and will run with many existing engine designs. It is also useful for a variety of industrial purposes. Similarly, methane can be piped in existing natural gas infrastructure and burned in existing boilers. Hydrogen, by comparison, is hard to store, harder to work with, and lower density.

There is no readily available carbon-neutral substitute for aviation fuel, gasoline, artificial fertilizers, or even natural gas. Synthesis from carbon-neutral power would provide it. Germany liquefied coal into methane and methanol at an industrial scale during WW II due to lack of oil imports. This is the same idea, just switching the heat and CO2 and H2 to a different source besides coal.

It's also possible to synthesize ammonia (fundamental to synthetic fertilizers and all kinds of chemistry) from H2 + N2 + C02 + heat in the presence of a catalyst.

Why is hydrogen itself, turned into ammonia, not a substitute for use of fossil fuels to make artificial fertilizers. Sure, urea contains carbon, but there are plenty of N fertilizers other than urea.

Ethanol is a carbon-neutral substitute for gasoline, no?

Ethanol can be potentially carbon neutral, given a ton of terms and preconditions.

It can be, but methanol is produced catalytically, unlike ethanol, which is made via fermentation and competes with crops for arable land. You can make ethanol catalytically as well, but afaik it typically involves making methanol first. Methanol has slightly less energy density, but it has the advantage of burning cleaner than any other fuel (no carbon-carbon bonds, so no soot), and it's easier to crack using waste heat, which is a pathway to more efficient engines (you can boost the LHV of the fuel by around 20% this way).

Crop ethanol uses an extremely large amount of land for the energy. US corn ethanol uses about 2 acres to support one car. And this has a large fossil fuel input (possibly with a net carbon output depending on fertilizer use and how it's distilled).

For a rough efficiency comparison, if there were some hypothetical 80% efficient solar panel and annual storage wasn't a concern, it could power the car with just the sunlight that hit it.

Yes it still requires hydrogen like normal gas to liquid processes. The innovation is that carbon capture and methanol production happen as part of the same process. This has the potential to make it much more efficient than doing two separate processes.

This scheme is combining synfuel production with CO2 capture, which is kind of cute. The hydrogen is serving two functions: it makes methanol, but it also regenerates the alkaline CO2 capture solution.

Brought to you by the Loker Hydrocarbon Research Institute. Mission statement:

"The final solution to the hydrocarbon shortage will come only when mankind can produce unlimited cheap energy as with the promise of safer atomic energy and other alternate sources. With abundant cheap energy, hydrogen can be produced from sea water and then combined with carbon dioxide to produce hydrocarbons. In the meantime, however, it is essential that solutions be found that are feasible within the framework of our existing technological base. The Loker Hydrocarbon Research Institute is at the forefront of this effort."

That would be growing plants to convert CO2 to carbohydrates and sugars, sprouting them to uplift more carbohydrates to sugars, fermenting them and extracting the ethanol?

OK. Wrong -ol. So, do it wood chips..

I'd love to have a small scale synthesis setup that I can use to store my excess production of solar electricity in the summer. I waste many MWh curtailing solar production.

Some napkin math suggests I throw away enough photovoltaic energy in one summer season to more than cover all of my pickup truck driving.

Why don't you get an electric car and battery instead?

I already did. But I still have a gas car and I still have excess production in the summer.

I just feel like there has to be a better use for your power than converting it into a hydrocarbon at single-digit efficiency.

The low temp requirements look promising, but wake me up when the cost of the system at scale is known.

Obviously things like long haul aviation need synthfuels, but I wouldn't hold my breath that this will be the magic bullet for keeping the ICE relevant in the next century.

Methanol is a feedstock for lots of industrial chemicals too.

Methanol can be turned into gasoline by the ExxonMobil MTG process.

https://www.exxonmobilchemical.com/en/catalysts-and-technolo...

This is not really new, lots of people are writing papers on different paths to this.

There was a huge interest in synthesizing motor fuels from coal or natural gas up to 1980, it makes for depressing reading because the Fischer-Trospch chemistry for building up hydrocarbons from hydrogen and carbon monoxide has awful economics. For anything else people would be happy that iron works as a catalyst but they scoured the rest of the periodic table looking for something better and didn’t find it. You have to run the reaction at low temperatures otherwise you get nothing but methane, but under those conditions reactions that build up and break down hydrocarbons are closely balanced so you have a huge machine which makes a trickle of fuel so the capital costs are high.

Looking at the history you’d think somebody would tell the airplane engineers that they should just go clean sheet and figure out how to fuel airplanes with hydrogen or methane but they are so used to being coddled (like that time the FCC couldn’t make them upgrade their broken altimeters or how they are just barely starting to remove lead from GA fuel after all these years) that they are sending chemical engineers on what’s been a lost cause for more than a century.

Given how inefficient ICE is to begin with, I can't imagine something like this being used for any transportation that can be easily electrified. This is really for niche cases like air travel, I assume.

ICEs are incredibly efficient. Electricity is only efficient if you only care about kwh delivered to the car doing to the wheels. The efficiency of getting kwh from the grid to the car puts it well worse than most battery setups.

The heat engines at fixed generating facilities are typically much more efficient than the engines in automobiles. Nearly a factor of 3 more efficient in some cases.

Grid losses are a few percent with modern tech (which exists in countries rich enough for EVs). Charger losses are another few percent. If you were to burn the same fuel in a closed cycle turbine you'd get about 1.5x the raw energy to the wheels after losses, but the turbine also doesn't need to use as high emissions fossil fuels. Regen and other efficiency features that are tolerated on EVs but not ICEs bring it up to about double well to wheel.

Then you can also provide 50-90% of the energy without it ever being made into AC by parking it under $1000 worth of solar panels.

Note: This is from 2020

There are a million ways to produce smaller amounts of energy from larger amounts of grid energy. This isn't really useful.

Yeah it's like the old snark about investing. It's being easy to make a million dollars. Just start with two million dollars.

The gross thing about this stuff is it's predicated on the average person not being able to do the engineering and accounting calculations to realize it's all lies.

With enough energy input you can do a lot of interesting things. Question is where you get the energy from.

And a related question is whether there are more interesting/efficient things you could do with that energy.

It's a question that relates to the laws of thermodynamics as well which dictate that the conversion between different forms of energy has some theoretical upper limits in terms of efficiencies and those inefficiencies multiply if you have a series of such conversions of e.g. solar power to carbo hydrates to mechanical energy or electrical energy. The longer that chain, the worse it gets.

You are better off charging a battery and using the stored energy directly. Almost no losses that way. It's the most efficient way to use energy for a lot of things.

There is a market for synthetic fuels of course but it is going to have to be a market that is willing to pay at least 3-5x the energy cost they would have if they were able to use electricity directly. A good example is long haul aviation. Batteries don't work for that (too heavy). Shipping might be another one.

Does anyone know whatever happened to Prometheus Fuels?

Still burning money, but looking for things where green premiums can be paid like for woke Zero Net Carbon aircraft.

It was anecdotal, but I met someone who worked with folks who worked there, there's a lot of smoke and mirrors and they don't really have what they say they have. Unfortunate as it looked really promising.

As in, it flat doesn't work, or it's just not economical enough at current energy prices?

The former. They're working to eliminate the need for an energy intensive distillation process and they haven't been able to get it to do what they've promised. They say they have a carbon nano-tube filter that can separate water and ethanol but no one's seen it work at high efficiency.

https://en.wikipedia.org/wiki/Fischer%E2%80%93Tropsch_proces...

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