Influence of Subcritical Water Pre-Treatment Parameters on Methane Production Enhancement by Co-digestion of Pre-treated Empty Fruit Bunch (EFB) with Palm Oil Mill Effluent (POME): Process Optimization and Comparative Study Adila Fazliyana Aili Hamzah, Muhammad Hazwan Hamzah, Khairudin Nurulhuda, Hasfalina Che Man, Muhammad Heikal Ismail, Pau Loke Show
a) Department of Biological and Agricultural Engineering, Faculty of Engineering, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia
b) Smart Farming Technology Research Centre, Faculty of Engineering, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia
c) Department of Chemical and Environmental Engineering, Faculty of Engineering, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia
d) Department of Chemical Engineering, Khalifa University, P.O. Box 127788, Abu Dhabi, United Arab Emirates
e) Zhejiang Provincial Key Laboratory for Subtropical Water Environment and Marine Biological Resources Protection, Wenzhou University, Wenzhou 325035, China
f) Department of Chemical and Environmental Engineering, Faculty of Science and Engineering, University of Nottingham Malaysia, Jalan Broga, 43500 Semenyih, Selangor, Malaysia
g) Department of Sustainable Engineering, Saveetha School of Engineering, SIMATS, Chennai 602105, India
Abstract
Recalcitrance of lignocellulosic structure in palm oil empty fruit bunch (EFB) is one of the major problems in producing high methane yield in anaerobic digestion even with co-digestion with palm oil mill effluent (POME). In this study, methane yield was improved through subcritical water (SCW) pre-treatment on EFB for co-digestion with POME. SCW pre-treatment of EFB was optimized in order to increase the biogas yield, volatile solid (VS) removal while reducing lignin content of EFB. A maximum biogas yield of 803.358 mL/gVS and VS removal of 37.03% with maximum reduction of lignin content to 12.19% was achieved from the pre-treated EFB under the optimized conditions (120℃-, 10 minutes and 20: 1 solvents to solid ratio). Fourier transform infrared spectroscopy (FTIR) verified the changes in lignocellulosic structure in the pre-treated EFB. X-ray diffraction (XRD) analysis indicated that the crystallinity index (CI) was increased to 65.42% after the disruption of crystalline cellulose during pre-treatment. Scanning electron microscopy (SEM) revealed structural cracking and hole opening in pre-treated EFB. Higher methane yield with 86.78% of methane content was observed in SCW pre-treated EFB correspondingly to 40% improvement in methane yield over the untreated sample. Anaerobic co-digestion of SCW pre-treated EFB with POME resulted in a reduction of lag phase (𝞴-) in SCW pre-treated EFB, during 60-day experimental period. SCW pre-treatment is an effective pre-treatment to improve the co-digestion of EFB and POME for methane production.
