Chemistry texts from college.
Light reading, huh?
Well...I've reread some intriguing
portions from some of those college text books over the past few weeks.
The subject matter was dealing with isotopes from the lighter elements,
and their radioactive transformations/trasmutations into other elements and isotopes.

What struck me as promising, as far
as distant-future possibilities for "anti-matter" production was that certain light isotopes like 6Carbon(11) [six protons; five neutrons] naturally emit positrons. The shorter the isotopic half-lives, the greater the intensity of the positron emission flux.

Positrons, like any antimatter particle
[eletrically charged or neutral], when
they collide with their matter/antimatter counterpart
[electrons] are 100% annihilated in
a burst of gamma-rays.
The energy released is calculated by E=MC^2.

So, for example, approximately 1800 grams [about four pounds] of
common carbon isotope, 6carbon(12},
contains 6-grams worth of electrons.
If those 6-grams of electrons collide
with 6-grams worth of positrons, the
energy unleashed would be equivalent
to about 288 metric tons of TNT.

Equation:
(24metric-tons TNT/gram)x
[(6-grams positrons) + (6-grams electrons)].

So 6-grams of positrons annihilating
with 6-grams of electrons would also unleash the energy equivalent of well over 1,000 tons of common rocket-fuel like LOX/LH2.
And 12-grams of positrons/electrons have about the same mass-equivalent as a couple of small french fries.

Jacob