  Leptogenesis typically requires the introduction of heavy particles whose
out-of-equilibrium decays are essential for generating a matter-antimatter
asymmetry, according to one of Sakharov's conditions. We show that in Dirac
leptogenesis, scatterings between the light degrees of freedom - Standard Model
particles plus Dirac neutrinos - suffice to generate the asymmetry. Sakharov's
conditions are satisfied because the right-handed neutrino partners are out of
equilibrium. Consequently, heavy degrees of freedom never needed to be produced
in the early universe, allowing for a reheating temperature below their mass
scale. We solve the Boltzmann equations and discuss the viable parameter space
together with observational signatures such as an increased number of effective
neutrinos in the early universe as well as proton decay for some realizations.
