The effect of pome ultrasonication pretreatment on biogas production and reduction of greenhouse gases emissions from wastewater treatment units of palm oil mills

Abstract

© 2020 Desalination Publications. All rights reserved. Palm oil mill effluent (POME) contains a high concentration of organic matter that could be produced useful biogas. Ultrasonication is a promising alternative method of POME pre-treatment with the potential to enhance biogas production from wastewater treatment systems at palm oil mills. Ultrasonication with an input power of 0.27–0.44 W mL–1 for 90 min, in the batch experi-ment, increased oil separation efficiency by 29.0% compared with natural sedimentation. The sol-uble chemical oxygen demand/total chemical oxygen demand (SCOD/TCOD) ratio and reducing sugar concentration were increased under this optimal ultrasonication condition, indicating that the pre-treated POME was improved biodegradability. The pre-treated POME was fermented in a semi-continuous stirred treatment tank to determine biogas production efficiency. The ultrasoni-cation pre-treated POME increased biogas production and also increased the proportion of methane from 40% to 63% and methane yield from 103.47 to 139.59 mL CH4 g–1 CODremoval compared to the control condition. The highest methane yield was obtained at a hydraulic retention time (HRT) of 16 d. However, longer HRT yielded slightly higher COD removal efficiencies. When the biogas produced is used for onsite electricity generation therefore, it is possible to diminish the electricity costs incurred to perform the ultrasonication setup and reduce greenhouse gases (GHGs) emissions to the environment. The overall GHGs emissions reduction from palm oil mill could reach up to 11% or 913.23 ton CO2 eq y–1 when the optimal ultrasonication scenario from this study applied to wastewater treatment system.