Alkaline hydrogen peroxide (AHP) pretreatment was applied to improve methane production from sweet sorghum bagasse under mesophilic conditions. After the pretreatment (solid-to-liquid ratio of 1 : 10, 2% NaOH at 121 °C for 60 min and then immersing with 5% (w/v) H₂O₂ for 24 h at room temperature), pretreated bagasse, the pretreatment effluent and the pretreatment mixture, together with the untreated bagasse, were used as substrates for methane production under the same volatile solid (VS) loading and digestion conditions. The AHP pretreatment resulted in lignin removal and different degrees of methane production. The methane production of bagasse was improved from 262.1 ± 7.3 mL CH₄ per g VS to 330.4 ± 1.3 mL CH₄ per g VS. The pretreatment mixture and pretreatment effluent could be successfully digested and both of the methane productions were higher than the untreated bagasse, although there were degrees of inhibition. In view of the bagasse recovery during the pretreatment, total methane production from separate digestion of pretreated bagasse and pretreatment effluent was 18.6% more than untreated bagasse based on the same mass of dry sweet sorghum bagasse. The kinetic analysis implied that the Cone model showed a better fit to the experimental data of untreated bagasse, pretreated bagasse and pretreatment effluent, and the Fitzhugh model was better to predict the methane production of the pretreatment mixture. AHP pretreatment could increase the methane production rate of sweet sorghum bagasse. These results will provide a reference to the methane production from AHP pretreated sweet sorghum bagasse in industry.

Palm oil is one of the most important agroindustries in Malaysia. Huge quantities of palm oil mill effluent (POME) pose a great threat to aqueous environment due to its very high COD. To make full use of discharged wastes, the integrated “zero discharge” pilot-scale industrial plant comprising “pretreatment-anaerobic and aerobic process-membrane separation” was continuously operated for 1 year. After pretreatment in the oil separator tank, 55.6% of waste oil in raw POME could be recovered and sold and anaerobically digested through 2 AnaEG reactors followed by a dissolved air flotation (DAF); average COD reduced to about 3587 mg/L, and biogas production was 27.65 times POME injection which was used to generate electricity. The aerobic effluent was settled for 3 h or/and treated in MBR which could remove BOD₃(30°C) to less than 20 mg/L as required by Department of Environment of Malaysia. After filtration by UF and RO membrane, all organic compounds and most of the salts were removed; RO permeate could be reused as the boiler feed water. RO concentrate combined with anaerobic surplus sludge could be used as biofertilizer.

Large volumes of untreated palm oil mill effluent (POME) pose threat to aquatic environment due to the presence of very high organic content. The present investigation involved two pilot-scale anaerobic expanded granular sludge bed (EGSB) reactors, continuously operated for 1 year to treat POME. Setting HRT at 9.8 d, the anaerobic EGSB reactors reduced COD from 71179 mg/L to 12341 mg/L and recycled half of sludge by a dissolved air flotation (DAF). The average effluent COD was 3587 mg/L with the consistent COD removal efficiency of 94.89%. Adding cationic polymer (PAM) dose of 30 mg/L to DAF unit and recycling its half of sludge caused granulation of anaerobic sludge. Bacilli and small coccid bacteria were the dominant microbial species of the reactor. The reactor produced 27.65 m³of biogas per m³of POME which was utilized for electricity generation.