  We study washout processes in post-sphaleron baryogenesis, a mechanism where
the matter-antimatter asymmetry is generated in the decay of exotic particles
after the electroweak phase transition. In particular we focus, in a quite
model independent way, on those scattering processes that have an amplitude
proportional to the CP asymmetry. We find that when the scatterings involve
only massless particles, the washouts are very severe for light decaying
particles (with masses below a few hundred of GeV) and successful baryogenesis
is only possible in a small portion of parameter space. Instead, if even a very
light particle participates in these processes, the allowed region of parameter
space opens considerably, although the final amount of baryon asymmetry may
differ significantly from the expression which is typically used and neglects
washouts. Furthermore, we analyze washouts from the non-thermal spectrum of
energetic particles produced in cascade decays and indicate in which models
they can be relevant.
