  In classical thermodynamics, irreversible processes are accomplished with an
increase of entropy and a release of heat into the environment. In the case of
black hole thermodynamics, instead, the increase of entropy is related with the
absorption of energy from the outside of the black hole. Based on this analogy,
the black hole is considered as a thermodynamic open system in the
non-equilibrium regime during the absorption. Applying a novel result, we
obtain a detailed balance relation for the macroscopic absorption of an
astronomical object by an static spherically symmetric black hole. Because of
the special characteristic of the thermodynamic system, it is necessary to
include an additional term for the entropy produced by the absorption, allowing
us to set a lower bound for the entropy production due to internal processes
associated to the fluctuation.
