To maximize the utilization of limited energy and material resources, a new design methodology for chemical processes is proposed based on a multiscale optimization approach. The different levels of the process hierarchy are presented and design aspects are discussed. The methodology is further exemplified by considering a methane steam reforming process for operation of a proton exchange membrane fuel cell (PEMFC) in an automotive application. The method delivers an optimal technically feasible process based on an integrated steam reforming reactor, operated in autothermal mode.