Comparison of Biogas Production from Oil Palm Empty Fruit Bunches of Post-Mushroom Cultivation Media (EFBMM) from Semi Wet and Dry Fermentation

Abstract

The high content of organic substances (25.56%) in solid waste post-mushroom cultivation (EFBMM) has the potential to be processed into biogas. Comparative research of biogas production from EFBMM with semi wet and dry fermentation aims to know the potential of biogas using 20% ​​cow dung solution (inoculum) which is mixed by way of circulation. Semi-wet anaerobic digestion is performed on WC/TS ratio (4.0 - 5.7) and dry digestion is performed on the WC/TS ratio (1.5 - 3.5). Anaerobic fermentation method was developed using a circulation system by observing the physical-chemical characteristics of raw materials and products produced. The results showed that the fermentation of dry and semi-wet fermentation for 65 days decreased the C/N ratio by 5.27% and 19.31%, respectively. Biogas production in semi-wet fermentation produces 18.60 L/kg of EFBMM biogas with CH₄ 131.85 L/kgVSr gas productivity with biogas composition 40.69% CH₄, 49.96% CO₂ and 7.58% nitrogen. In dry fermentation, biogas produced 5.98 L/kg EFBMM with CH₄ 38.71 L/kgVSr gas productivity and biogas composition 35.58% CH₄, 46.12% CO₂ and 17.31% nitrogen. Semi-wet and dry fermentation process produces carbon (released as biogas) respectively 3.90 kgC (26.88%) and 3.40 kgC (23.44%). The result of lignocellulose analysis showed that dry fermentation of EFB using fungus media was able to degrade 6.00% hemicellulose, 10.60% cellulose and 6.74% lignin. Where as semi-wet fermentation was able to degrade 9.26% hemicellulose, 13.02% cellulose and 9.28% lignin. Imaging results with SEM show the fermentation process alters the EFBMM lignocellulosic morphology structure into more open, hollow and fragile textures.

Keywords: biogas, EFBMM, WC/TS ratio