An ambient anaerobic digester system for anaerobic digestion of animal waste with biogas production and recovery is provided. The anaerobic digester system includes a substantially flexible bladder for anaerobically digesting the animal waste with biogas production and transmitting the biogas to at least one biogas storage container, biogas use device or a combination thereof. In a preferred form, the substantially flexible bladder has a waste inlet, a digester effluent outlet, one or more sludge access ports and a biogas outlet in a top surface thereof. The anaerobic digester system may inexpensively, simply, reliably, and effectively be used to treat animal waste without energy expenditure and little capital expense, thus minimizing pollution typically caused by animal waste.