[beanjuice]

What I don't understand about the proposal is that every c-c bond the fungus could make still has to be shipped from earth.

[xolox]

Might it not be possible to "harvest" carbon from sources on e.g. the moon [1], thereby requiring less effort to launch those resources into orbit? Feel free to point out if I'm talking (thinking) nonsense here...

[1] https://en.wikipedia.org/wiki/Lunar_resources#Carbon_and_nit...