  Fluctuating entropy production is studied for a set of linearly coupled
complex fields. The general result is applied to non-equilibrium fluctuating
hydrodynamic equations for coarse-grained fields (density, temperature and
velocity), in the framework of model granular fluids. We find that the average
entropy production, obtained from the microscopic stochastic description, can
be expressed in terms of macroscopic quantities, in analogy with linear
non-equilibrium thermodynamics. We consider the specific cases of driven
granular fluids with two different kinds of thermostat and the homogeneous
cooling regime. In all cases, the average entropy production turns out to be
the product of a thermodynamic force and a current: the former depends on the
specific energy injection mechanism, the latter takes always the form of a
static correlation between fluctuations of density and temperature
time-derivative. Both vanish in the elastic limit. The behavior of the entropy
production is studied at different length scales and the qualitative
differences arising for the different granular models are discussed.
