In this paper we consider scalar conservation laws with space dependent flux functions u_t + f(u, x)_x = 0 . The space dependency of the flux may be discontinuous. There exists several entropy conditions in the literature giving rise to uniqueness. The same initial data may give rise to different entropy solutions, depending on the criteria one selects. This motivated us to derive the PDE together with an entropy condition as a hydrodynamic limit from a microscopic interacting particle system. We are inclined to prefer the entropy solution selected by this method. We prove existence of weak entropy solutions to these equations, where the entropy is a modified version of the Kruzkov entropy, taking into account the case that the flux depends on space in a discontinuous fashion. The proof uses an approximation sequence coming from a microscopic interacting particle system. This is joint work with G.-Q. Chen