I talked with the director of Fermilab's antiproton source. This is the most efficient facility in the world for the production of antimatter. So, can we manufacture anti hydrogen in bulk, to fuel spacecrafts?
The total annual world production of electric power is 19 trillion kilowatt hours. If that energy could be converted into antimatter with perfect efficiency, m = E/c**2, it would yield 760 kilograms.
Unfortunately, antimatter is made by slamming protons into a metal target at 120 GeV. For every million protons, only about 8 antiprotons are produced among many other random particles, radiation and heat. The accelerator itself is not a very efficient machine. Consumming several megawatts of electricity, it yields an antiproton beam current of 80 milliwatts.
If the total world electrical output was used in this way, it would yield about 20 milligrams of antimatter per year.