You can use a small black hole for mass transmutation of lighter elements (like all that surplus hydrogen just sitting idly in your local gas giants or star) into much more useful heavier elements (metals, carbon, oxygen, etc.):
The extreme temperatures and pressures in the accretion disk are basically used to fuse the lighter elements together into heavier ones, which are then pulled out by machinery in close orbit.
https://www.orionsarm.com/eg-article/464790d2497de
The extreme temperatures and pressures in the accretion disk are basically used to fuse the lighter elements together into heavier ones, which are then pulled out by machinery in close orbit.