Abstract: The aim of this study is utilizing weighted residual method, a kind of numerical models, which leads to a simpler model for users. Utilizing the simplified numerical models helps landfill owners and decision makers for an easier understanding of methane emission. In this study, three different numerical models with five bench marks have been developed to estimate methane gas generation of a considered landfill: (i) linear polynomial function for boundaries and trail function, (ii) linear function for trail and second order polynomial function for boundaries satisfaction and (iii) second order polynomial function for boundaries satisfaction and Sin shape function for trail function. Second one as the best fitted one with SD of 0.76 has been selected.