  The emergence of a classical spacetime from any quantum gravity model is
still a subtle and only partially understood issue. If indeed spacetime is
arising as some sort of large scale condensate of more fundamental objects then
it is natural to expect that matter, being a collective excitations of the
spacetime constituents, will present modified kinematics at sufficiently high
energies. We consider here the phenomenology of the dissipative effects
necessarily arising in such a picture. Adopting dissipative hydrodynamics as a
general framework for the description of the energy exchange between collective
excitations and the spacetime fundamental degrees of freedom, we discuss how
rates of energy loss for elementary particles can be derived from dispersion
relations and used to provide strong constraints on the base of current
astrophysical observations of high energy particles.
