  We consider a one-dimensional totally asymmetric nearest-neighbor zero-range
process with site-dependent jump-rates - an environment. For each environment p
we prove that the set of all invariant measures is the convex hull of a set of
product measures with geometric marginals. As a consequence we show that for
environments p satisfying certain asymptotic property, there are no invariant
measures concentrating on configurations with critical density bigger than
$\rho^*(p)$, a critical value. If $\rho^*(p)$ is finite we say that there is
phase-transition on the density. In this case we prove that if the initial
configuration has asymptotic density strictly above $\rho^*(p)$, then the
process converges to the maximal invariant measure.
