Anaerobic digestion is a simple decomposition process of organic matter by microorganisms while producing biogas in a low (absence) of oxygen environment. Anaerobic microorganisms are slow in growth and metabolism which require large volume of reactors in an industrial scale. Immobilization of anaerobic microbia on solid media such as zeolites can increase and maintain its population in the reactor and hence may speed up the decomposition process. The addition of essential micronutrients such as Fe2+ into the zeolite as microbial support may further increase the affinity of microbial film to attach and grow on the zeolite surface. This study aimed to evaluate the effect of Fe-loading into zeolite packing on an anaerobic digestion system for biogas production using stillage as the substrate. During experiment, 0.033 mg Fe2+ was loaded into each gram of zeolite rings by wet impregnation method. Then, the rings were put inside batch anaerobic reactors filled with stillage in various organic contents represented by soluble Chemical Oxygen Demand (sCOD). The observation of sCOD reduction, Volatile Fatty Acid (VFA) concentration, and biogas production were conducted for 28 days of batch mode anaerobic processes. It is shown that the Fe-loaded support has significant effects on enhancing the organic digestion process in the reactors with high concentration of stillage. On the other hand for lower concentration reactors, the iron impregnated media have similar effect on the digestion process with the media without impregntion. A mathematical model was developed for simulation of the methane generation from sCOD with VFA as the intermediate product. The simulation supports the evidence that the presence of Fe2+ in the immobilization media had a noticeable impact on accelerating volatile fatty acids conversion into methane and preventing acidic condition in the reactors.