An adaptive neuro-fuzzy inference system was applied for modeling anaerobic digestion of primary sludge in a wastewater treatment plant [8]. The model satisfactorily predicted effluent volatile
solid and biogas yield. Holubar et al. [9] used several feed-forward back propagation neural networks to model and subsequently control biogas production in anaerobic digesters. Gas composition, biogas production rate, pH, volatile suspended solids and other parameters were measured and simulated to determine the best feeding profile.