  We compute the bulk viscosity in holographic models dual to theories with
Lifshitz scaling and/or hyperscaling violation, using a generalization of the
bulk viscosity formula derived in arXiv:1103.1657 from the null focusing
equation. We find that only a class of models with massive vector fields are
truly Lifshitz scale invariant, and have a vanishing bulk viscosity. For other
holographic models with scalars and/or massless vector fields we find a
universal formula in terms of the dynamical exponent and the hyperscaling
violation exponent.
