In Reunion Island, most of household wastes (HW) are landfilled. Residual household wastes (RHW) represent 44.6% of HW produced and are totally landfilled. Indeed, significant environmental burdens are caused by current waste management system. Hence, a new system that will ensure the energy recovery of waste was implemented. With the aim of integrating gasification into the waste management system in Reunion Island, a study of gasification of RHW through modeling is suggested in this work. Indeed, a 3-step methodology was adopted, the first step is waste characterization, 3 mixtures of waste have been established based on local context and data from the last waste characterisation campaign in Reunion. The second step is the modeling of a stratified downdraft reactor using an optimized steady-state equilibrium-based and kinetic model. Optimization consists of using correction factors to modify the equilibrium constants of the methanation and water gas shift reactions. The models were validated against extensive experimental data from literature. In addition, the effect of equivalence ratio and moisture content was studied in the steady-state equilibrium model. Furthermore, a sensitivity analysis of the kinetic model was conducted by investigating the effect of solid residence time and reduction temperature on the composition of producer gas.