This is better. Terraform believes they can make methane from the air for cheaper than it can be extracted from the ground, leading to a preference for "carbon neutral" fuels. Part of their thesis though is the requirement for solar to keep getting cheaper and cheaper (as it has).

Excess manufactured methane could also be injected underground, presumably.

What's a more efficient way to split water into hydrogen and oxygen: using electricity from a solar panel or using photosynthesis in a plant?

Electrolysis is orders of magnitude more efficient, but your equipment isn't self replicating.

That is a good question.

Do you have any uses for the plant, or does it create interesting byproducts for you? Photosynthesis is not very efficient, but it is great at making complex organic molecules like sugar or cellulose.

But a plant needs more than power. It needs nutrients, usually in the form of fertilizer.

They also don't generally make hydrogen, not directly at least.

Another thing to consider: plants currently require a lot of natural gas or other fossil fuels to grow. Droughts and heat waves can disrupt production.

You are talking about use of natural gas to make nitrogen fertilizer; ammonia made with "green hydrogen" replaces this.

These are orthogonal concepts this is an attempt to create a carbon neutral hydrocarbon for energy use, the other is an attempt at carbon negative sequestration.