[HarHarVeryFunny]

As long as we have air and water (i.e. as long as we're alive), then we can make propellants such as Methane or Liquid Hydrogen and LOX, Hydrazine & Dinitrogen Tetroxide (or Hydrogen Peroxide).

[macintux]

None of which are, I assume, as easy/efficient/effective to integrate into a new civilization's tech tree as coal & oil.

[crazygringo]

So? We build nuclear power plants and it's not exactly easy/efficient to extract uranium. Hard things are done all the time.

Having coal/oil is pretty irrelevant in terms of whether a civilization can build spacecraft.

[macintux]

"and when we drain the planet dry of easily-accessible fossil fuels we’ve deprived any successor civilization of its opportunity to escape the planet."

Successor. Whoever comes along after we've done ourselves in.

[crazygringo]

Huh? "We" is the human race, whatever civilization. What point are you trying to make? What I said stands, exactly how I said it.

[HarHarVeryFunny]

What has that got to do with energy dense rocket fuels for getting to orbit ?!

[macintux]

The key phrase was "successor civilization".