Abstract
This study compared the performance of thermophilic and mesophilic digesters of an anaerobic digestion system from palm oil mill effluent (POME), in which temperature is a key parameter that can greatly affect the performance of anaerobic digestion. The digesters were incubated at two distinct temperatures of 55 and 37 °C, and operated with varying organic loading rates (OLRs) of 2.4, 3.2, and 4.0 g COD/L.d by altering the chemical oxygen demand (COD) of acidified POME during feeding. The results indicated that the performance of anaerobic digestion increased as the OLR increased from 2.4 to 4.0 g COD/L.d. At the OLR of 4.0 g COD/L.d, the thermophilic condition showed the highest methane yield of 0.31 ± 0.01 L/g COD, accompanied by the highest COD removal and volatile solid reduction, which were found to be higher than the mesophilic condition. Microbial community analysis via denaturing gradient gel electrophoresis (DGGE) revealed that Methanothermobacter sp. emerges as the dominant microbe, which is known to utilize the carbon dioxide pathway with hydrogen acting as an electron donor for methane formation
Highlights
Nowadays, researchers have successfully produced biogas from various resources including, but not limited to, food waste, wastewater, lignocellulosic waste, municipal waste, and agricultural by-products such as palm oil mill effluent (POME)
The results indicated that the thermophilic digester registered a higher methane yield than the mesophilic digester at every organic loading rates (OLRs) tested
Removal and volatile solids (VS) reduction in the thermophilic condition, which was higher than the mesophilic condition
Summary
Researchers have successfully produced biogas from various resources including, but not limited to, food waste, wastewater, lignocellulosic waste, municipal waste, and agricultural by-products such as palm oil mill effluent (POME). POME is a wastewater that is produced from palm oil processing and contains a high amount of suspended solids, has a brownish color, and is discharged at 80–90 ◦ C with a mild acidic condition [1]. Major constituents in raw POME include fermentable sugars, volatile fatty acids (VFA), oil and grease, fibers, and organic materials. The discharge of untreated POME can be detrimental to the environment as it is associated with an unpleasant smell with other dissolved organic materials that can contaminate water bodies. As Malaysia and Indonesia produce the highest volume of palm oil in the world, with the correct technologies, both countries can positively benefit from its massive production of POME
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