Anaerobic digester system for animal waste stabilization and biogas recovery

A method for anaerobically digesting animal waste with biogas production at an average ambient temperature of 65 degrees Fahrenheit or greater, comprising the steps of:

• Conveying animal waste through one or more waste inlets in a substantially flexible bladder sized to maintain the greater of a minimum HRT or daily volatile solids loading rate per 1000 ft3;
• Maintaining the animal waste in the substantially flexible bladder for a period of time for anaerobic digestion of the animal waste;
• Removing solid animal waste from the substantially flexible bladder;
• Removing digester effluent from the substantially flexible bladder through one or more digester effluent outlets in the substantially flexible bladder;
• Providing a displacement tank in fluid communication with at least one of the one or more digester effluent outlets;
• and
• Storing biogas within the substantially flexible bladder by displacing animal waste therein through the at least one of the one or more digester effluent outlets into the displacement tank.