Driven by the high fuel flexibility of entrained flow gasifiers, the aim of this dissertation is to examine the conversion behavior of different fossil and renewable solid feedstock. The main factors influencing entrained flow gasification, such as volatile release, surface kinetic, structure evolution and thermal deactivation, are experimentally investigated and described by model equations. The model parameters are summarized in a database and applied in a validated 1D-model to determine their sensitivity on the overall conversion behavior.