All the solids collected in the primary treatment system, both floatable and settleable, and the waste activated sludge (WAS) from the final clarifiers are sent to the anaerobic digestion process. The anaerobic digestion process breaks down organic materials in a zero-oxygen environment and produces biogas (64% methane, low grade natural gas). Since anaerobic digestion produces a product that can be used to offset energy costs,the WRF diverts some of the hauled waste that comes to the facility daily to the anaerobic digester. The hauled wastes that are diverted are typically concentrated, have a high biochemical oxygen demand (BOD) content, and are high in volatile organics (organics that can break down). The sludge and hauled wastes are blended together and pumped to the digesters where they will stay for 21+ days. Over that period, biogas is produced, and what is left of the solids are sent to solids processing.