Hydrogen-methane production from pulp & paper sludge and food waste by mesophilic-thermophilic anaerobic co-digestion

► H2-CH4 co-production from PPS and MGWL was efficient by a two-stage process. ► Maximum H2 yield and CH4 yield were obtained with 1: 1 VS ratio. ► 71%-87% removal efficiencies of SCOD were attained for hydrogen-methane production. ► No VFA, NH3-N and Na+ inhibition were found in the process.