The anaerobic digesters have been playing a significant role for generation of biogas and energy from solid wastes as a source of clean & green energy as well as to reduce the emissions of greenhouse gases. Hence the design and development of anaerobic digesters are very important for the process of stabilizing and reducing the excess biological sludge from wastewater treatment plants. Recently, Computational Fluid Dynamics (CFD) technology has been extensively used for the purpose of design and development of anaerobic digesters. In order to study mixing phenomena inside anaerobic digesters, Computational Fluid Dynamics (CFD) technology has been used for in present case. In the present paper, a two-dimensional CFD-turbulent-model has been developed for a non-Newtonian fluid in anaerobic digester by using COMSOL software. The basic Non-Newtonian flow model has been successfully validated with experimental data for a pipe by comparing axial velocity along radial direction. The CFD model has been used to predict flow fields qualitatively and quantitatively for various flow conditions.