  Within the framework of adiabatic regularization, we present a simple
formalism to calculate number density and renormalized energy-momentum density
of spin 1/2 particles in spatially flat FLRW spacetimes using an appropriate
WKB ansatz for the adiabatic expansion for the field modes. The conformal and
axial anomalies thus found are in exact agreement with those obtained from
other renormalization methods. This formalism can be considered as an
appropriate extension of the techniques originally introduced for scalar
fields, applicable to fermions in curved space.
