  In this paper we study the hydrodynamic limit of a B.G.K. like kinetic model
on domains with boundaries via $BV_{loc}$ theory. We obtain as a consequence
existence results for scalar multidimensional conservation laws with kinetic
boundary conditions. We require that the initial and boundary data satisfy the
optimal assumptions that they all belong to $L^1\cap L^\infty$ with the
additional regularity assumptions that the initial data are in $BV_{loc}$. We
also extend our hydrodynamic analysis to the case of a generalized kinetic
model to account for forces effects and we obtain as a consequence the
existence theory for conservation laws with source terms and kinetic boundary
conditions.
