Evaluation of ultrasonic pretreatment on anaerobic digestion of citrus orange peel waste for methane production

Abstract EN

The study was performed in order to confirm and develop the possible use of orange peel waste in biogas production and to investigate ultrasonic pretreatment effect on enhancing biogas production.

The inhibition by limonene present in the orange peel waste is the major challenge of biogas production from citrus waste, encountering this challenge was achieved by the removal of this substance using a steam distillation process.

A batch anaerobic digestion experiment was performed at two thermal conditions thermophilic and mesophilic using a mixture of sludge and orange peel as a substrate in this study.

In order to improve the solubilization of organic matter in the orange peels a mechanical pretreatment was applied: ultrasonification witch was carried out at a frequency of 37 kHz using an ultrasound cleaner for different exposure times 1 min, 5min, 10 min and 15 min which were investigated for the optimization.

The obtained results of biogas production from the treated samples with the ultrasonic frequency showed a remarkable increase comparing with the untreated samples: 67% and 62% improvement after the ultrasonic pretreatment.

Cumulative methane production of pretreated orange peel waste was the highest for the treatment times 1 and 10 minutes giving 970 mL.gTvs-1 and 671 mL.gTvs-1 for mesophilic and thermophilic phases respectively.