Waste activated sludge (WAS) is generated in large quantities at industrial plants, including pulp and paper, petrochemical, food processing, meat processing and pharmaceutical manufacturing. as a by-product of treating wastewater. Currently, WAS is managed as a waste and is either incinerated, land-filled, or land applied. However, WAS has economic and environmental value: it is a potential source of green renewable energy that can lower greenhouse gas (GHG) emissions and a plants environmental footprint.