As long as we have enough energy, we can make fertilizers. Of course, petrochemicals are a nice raw material, but not necessary.
And we are not running out of energy, anytime soon. (Though we may run out of oil.)
If you wish to make an apple pie from scratch, you must first invent the universe - Carl Sagan
On the practical side: Using coal as a raw material, you should be able to make fertilizers with only somewhat more energy than from oil.
Rather than the government funding everything, the mere possibility of being able to find a 100 ton lump of gold (or whatever) would get multiple space exploration efforts kicked up the butt immediately ;-)
If we want to advance our Space Travel technology, we need to keep trying to do things beyond our reach, to force us to improve.