Enrichment of biomethane production from paper industry biosolid using ozonation combined with hydrolytic enzymes

•OZNCE method has effectively improved the disintegration of PPMW biosolid.•OZNCE method was achieved 31% of lysis rate at 15 min of pretreatment time.•Higher methane production of 324 L/kg VS was noted for OZNCE method.•Combinative method was achieved a net energy of 168 kWh/ton of biosolid.