[V__]

> In the future, we will still have CO2 credits. But instead of allowing companies to release CO2 into the air… Credits might allow companies to capture co2.

The article then goes on to explain that solar + co2 capture results in methane. But isn't this at best co2 neutral? Since nearly all use-cases for methane would release the co2 again and would make the credits' comparison pointless?

Besides that, will methane actually be needed in the future? Looking at the common uses [1], it's mostly used for fuel and hydrogen generation. Both things, which solar, can be used for directly without the conversion loses of using methane as an intermediate step.

[1] https://en.wikipedia.org/wiki/Methane#Uses

[photochemsyn]

Essentially all current petrochemical processes use methane as the primary feedstock, including my favorite, carbon fiber:

https://arpa-e.energy.gov/technologies/projects/carbon-fiber...

You can similarly make diamond from atmospheric CO2 (very energy intensive however), which is a pretty stable material.

Hydrogen itself is very difficult to store and transport, but it's critical for things like making steel without fossil fuels and for ammonia fertilizer production. Currently it's all made via steam reforming of natural gas at the industrial point of use, so if you can make methane from air and water, you don't have to rebuild all that infrastructure.

It's implausible to expect much effect on reducing global warming, however, at best we'll be able to stabilize atmospheric CO2 (assuming we don't run into major natural positive feedbacks from permafrost melt and shallow marine sediment outgassing, anyway). Any such speculation is also predicated on elimination of fossil fuels from the energy mix, which doesn't seem to be likely for decades at best.

[ZeroGravitas]

I think they mention it further down, but some fraction of methane isn't burned but turned into things like plastic and other industrial chemicals.

> And not all of it will be re-released into the atmosphere. As we saw in the Ocean Farming article, some of it will sink in the oceans13 . Even today, 3% of methane is not burned, but used in other ways like plastics production, thus leaving the carbon cycle altogether...

[pfdietz]

3% of Natural Gas, not methane. Natural gas contains other gases, in particular ethane, which is the feedstock for making ethylene and then polyethylene.

US fracked gas is quite high in ethane.

Some of the natural gas used for plastics is to make heat, for example to drive ethylene crackers (which decompose ethane at high temperature). Methane could be burned for that.

There was a process for oxidative coupling of methane to make ethylene (a Bay Area startup named Siluria created it, using a cool phage-based combinatorial method to find structured catalysts) but I don't think it could compete with all that cheap natural ethane.

[detourdog]

Anaerobic digestion produces methane. The thinking is recently produced carbon and will be presumably immediately re-absorbed by the surrounding plants in the next growing season. This acting as carbon balanced energy source.

A smaller amount of hydrogen is also produced.

[pfdietz]

Biogas is a mixture of methane and CO2. It's been discussed to separate out the CO2 (easy because it's at such a high concentration) and sequester it. This makes biogas net carbon negative. Alternately, hydrogen can be added to convert the CO2 into additional fuel.

The downside is the large land area needed to make the biomass that gets digested. In a fossil fuel free future, carbon-containing waste streams will be valuable as feedstocks (for chemicals, for liquid fuels that cannot be electrified easily), so there will be competition for these streams.

[AdamTReineke]

You can seequester the methane back in the ground if you are capturing more than is consumed.