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YC backed a company in this space: Prometheus Fuels. The science is sound, and the scaling is economical as you look at renewables for the electricity. Some links:

https://www.prometheusfuels.com/

https://www.sciencemag.org/news/2019/07/former-playwright-ai...

Prometheus Fuels looks cool, but (yeah, standard HN comment) their website is janky on firefox.

Fusion + Syn Fuel is definitely in the playbook to reverse climate change.

There are many power-to-x chemistries that I think are much easier than methane once you grow out of easily available concentrated CO2. They don't quite reach the energy density of hydrocarbons, but that's not much of an issue for stationary storage in the "seasonal scale battery" use case. Almost everything can serve as an "oxidizable" in reduced form, and if the resulting oxide isn't gaseous you lose the "tank gets lighter" effect that is only really important for aircraft but win a solution to the capture problem for completing the cycle. Iron for example is said to get an energy density roughly comparable with coal. Another x in power-to-x is ammonia, which could be used in an open cycle scenario where DAC would be trivial because so much of our air is nitrogen.

Honestly, good-old heat pumps work well for most climates. You heat up the ground underneath your house in the summer, and harvest that heat during the winter. That seems a lot more economical than synthesizing methane and hoping it doesn't leak back out into the atmosphere.

If we can get synthetic methane from atmospheric CO2 to work in an economic fashion, I imagine we could also use it to directly reduce atmospheric carbon (maybe by permanently fixing it into a solid). Problem solved!

Heat pumps are certainly a good option in some cases, but other times they are not practical.

For dense urban areas, there may not be enough open ground available to bury the heat pump coils. Also, in colder climates, many houses and buildings use hot water or steam radiators, and heat pumps can't efficiently heat water hot enough for this type of system. Retrofitting ducts to replace radiators and switching to forced air heating can be prohibitively complex and expensive.

Methane leaks are certainly a valid concern, but if we mandate better monitoring systems and do a better job of repairing leaks when they occur, it seems plausible we could get leaks down to acceptable levels. Methane is indeed a potent greenhouse gas, but it doesn't last nearly as long as CO2 before it breaks down, so if leaks are kept to a minimum I don't know whether they would ultimately be a huge deal in the long term.

> Methane is indeed a potent greenhouse gas, but it doesn't last nearly as long as CO2 before it breaks down

Obviously, methane breaks down to CO2 but there is no need to state this when referencing methane emissions. The Global Warming Potential can be used to relate the magnitude of damage over a given time horizon, for methane over 100 years it has 34 times more global warming potential. Obviously you can take exception to some of the methodologies used to calculate these but in general it's better than leaving the impression that CH4 emissions aren't important.

It definitely is doable, but the efficency of the process probably prevents market adoption, until fosil gas gets more expensive. (cheap fracking gas)

And if you use a methan fuel cell - you can use its surplus heat for heating while generating electricity.

I don't think they are market ready, though. But there are lots of options out there and the best solution is likely to combine what works now.

Btw. I think there was a breakthrough with natrium based batteries. (No lithium needed). They were just not as energy dense as lithium based ones, but that matters not so much for stationary use. So with no ressource limitation, you could produce them in very big quantities..

the efficency of the process probably prevents market adoption

I think this is correct right now, but the biggest cost by far for generating green methane at scale would be the energy costs for electrolysis to get the hydrogen from water. If renewables continue to fall in cost, we may rapidly reach a point where we have a huge surplus of green energy for parts of the year. There are already places in the US where energy prices regularly go negative due to excess wind energy, for example.

Folks have talked a lot in the past about using excess energy from renewables to generate hydrogen gas, but hydrogen alone is a lot harder to manage, is much less energy-dense by volume, is impractical to liquefy for storage and transport, and isn't compatible with existing infrastructure. Methane solves all of these issues, and doesn't take much additional energy to create beyond what you must spend for hydrogen alone.

Sodium ion batteries[1] are another promising one for stationary batteries that pop up from time to time. Sodium is obviously abundant and cheap, and has similar properties to lithium. For grid storage, it’s heavier weight and less energy density isn’t a big issue. However like many alternative battery solutions it it’s the there yet for whatever reason.

1 https://spectrum.ieee.org/energywise/energy/batteries-storag...

Lithium batteries are mostly nickel, despite the name. AFAICT the main benefits are replacing the nickel.

In the very long term converting excess generation into methane is almost sure to happen provided that can get accurately carbon priced versus ground extracted gas.

It's not even just seasonal capacity shifting, any situation that weight matters in will favor LNG over electric batteries for the foreseeable future even if batteries get 10x better.

Doesn't this simply mean you increase baseload during winter? Solar isn't a baseload power option, it's best used in a portfolio of energy sources.

Energy fluctuations are what cost Texas so much the last month, and that could be greatly mitigated with battery storage solutions.

To an extent.

But imagine you were writing a plan for northern europe to become carbon-neutral for electricity, heating and transport.

If you need the most power in the coldest, darkest months, and you manage to meet that demand with renewables that aren't solar, why have solar in the portfolio at all?

Interesting, I'd never heard of this before. If we didn't use carbon-neutral CO2 sources would it still be an improvement over status quo?

I thought apple was already going to do something with methane and power, from what I recall when they announced the new campus.

There was recently on HN a discussion about a proposed solution for seasonal heat storage based in aluminum - air batteries.