A Possible Fusion Power System
According to Next Big Future, there are antiprotons orbiting the Earth and these could be used to catalyze fusion reactions:
In other words, a gigawatt could produce 95 megatons of low-fallout hydrogen bombs. Those bombs, if used in a nuclear-powered piston engine at 33% efficiency, would produce 4 gigawatts of power.
A one gigawatt power system inside of an earth orbiting superconducting traps could produce 95 milligrams of antimatter per year.
One microgram of antihydrogen would be theoretically by enough to be the trigger for one kiloton antihydrogen bombs. By not having a nuclear fission trigger the amount of fallout is massively reduced.