  In the context of an homogeneous and isotropic universe, we consider the
degeneracy condition at background level between two scenarios in which
processes out of equilibrium are possible to explore their cosmological
implications; this consideration allows us to deviate from the perfect fluid
description and in this case bulk viscosity represents a viable candidate to
describe entirely such effects. The cosmological model describing an unstable
dark matter sector is mapped into a slight modification of the $\Lambda$CDM
model characterized by a viscous dark matter sector; under this consideration
our description does not depend on a specific formulation of viscous effects
and these can be fully reconstructed and characterized by the parameter that
determines the decay ratio of dark matter. However, in this new scenario the
cosmic expansion is influenced by the viscous pressure and the dark energy
sector given by the cosmological constant is translated into a dynamical one.
As consequence of our formulation, the test against observations of the model
indicates consistency with quintessence dark energy but the crossing of the
phantom divide can be accessible.
