High methane production potential of activated sludge accumulating polyhydroxyalkanoates in anaerobic digestion

A technique for using waste activated sludge (WAS) accumulating intracellular storage materials was studied for enhancing methane production through anaerobic digestion. Model WAS samples with various contents of poly-β-hydroxyalkanoates (PHAs) were used for anaerobic digestion tests. Methane production during 32 d from WAS with PHA content of 290 mg g⿿1 of dry mass was higher by 30% than that from WAS with PHA content of 30 mg g⿿1. Kinetic models showed that PHAs have a higher biogas production rate constant and a higher biogas yield than microbial cells of WAS in anaerobic digestion. An increase of 10 mg g⿿1 of the PHA content in WAS increased biogas production of 2.6 mL g⿿1-VSadded and methane production of 2.4 mL g⿿1-VSadded. Results show that PHA-accumulating WAS has high potential for methane production in anaerobic digestion.