Alkali pretreatment enhances biogas production in the anaerobic digestion of pulp and paper sludge

Laboratory-scale experiments were carried out in completely mixed bioreactors, 1 L capacity with 700 mL worked. Optimal amount of sodium hydroxide for organics solubilization in the step of pretreatment was 8 g NaOH/100 g TSsludge. Under this condition, the PPS flocs structure was well disrupted resulting in the void rate and fiber size decreased after pretreatment, and SCOD increased up to 83% as well as the peak value of VFA concentration attained 1040 mg acetic acid/L during AD. The AD efficiency of PPS with and without pretreatment was evaluated. The highest methane yield under optimal pretreatment condition was 0.32 m3 CH4/kg VSremoval, 183.5% of the control. The results indicated that alkali/NaOH pretreatment could be an effective method for improving methane yield with PPS.