Enhancement of Thermophilic Biogas Production from Palm Oil Mill Effluent by pH Adjustment and Effluent Recycling

A sudden pH drops always inhibits the anaerobic digestion (AD) reactor for biogas production from palm oil mill effluent (POME). The pH adjustment of POME by oil palm ash addition and the biogas effluent recycling effect on the preventing of pH drop and change of the archaea community was investigated. The pH adjustment of POME to 7.5 increased the methane yield two times more than raw POME (pH 4.3). The optimal dose for pH adjustment by oil palm ash addition was 5% w/v with a methane yield of 440 mL-CH4/gVS. The optimal dose for pH adjustment by biogas effluent recycling was 20% v/v with a methane yield of 351 mL-CH4/gVS. Methane production from POME in a continuous reactor with pH adjustment by 5% w/v oil palm ash and 20% v/v biogas effluent recycling was 19.1 ± 0.25 and 13.8 ± 0.3 m3 CH4/m3-POME, respectively. The pH adjustment by oil palm ash enhanced methane production for the long-term operation with the stability of pH, alkalinity, and archaea community. Oil palm ash increased the number of Methanosarcina mazei and Methanothermobacter defluvii. Oil palm ash is a cost-effective alkali material as a source of buffer and trace metals for preventing the pH drop and the increased methanogen population in the AD process.

Strategies for recovery of imbalanced full-scale biogas reactor feeding with palm oil mill effluent

Background Full-scale biogas production from palm oil mill effluent (POME) was inhibited by low pH and highly volatile fatty acid (VFA) accumulation. Three strategies were investigated for recovering the anaerobic digestion (AD) imbalance on biogas production, namely the dilution method (tap water vs. biogas effluent), pH adjustment method (NaOH, NaHCO3, Ca(OH)2, oil palm ash), and bioaugmentation (active methane-producing sludge) method. The highly economical and feasible method was selected and validated in a full-scale application. Results The inhibited sludge from a full-scale biogas reactor could be recovered within 30–36 days by employing various strategies. Dilution of the inhibited sludge with biogas effluent at a ratio of 8:2, pH adjustment with 0.14% w/v NaOH, and 8.0% w/v oil palm ash were considered to be more economically feasible than other strategies tested (dilution with tap water, or pH adjustment with 0.50% w/v Ca(OH)2, or 1.25% NaHCO3 and bioaugmentation) with a recovery time of 30–36 days. The recovered biogas reactor exhibited a 35–83% higher methane yield than self-recovery, with a significantly increased hydrolysis constant (kH) and specific methanogenic activity (SMA). The population of Clostridium sp., Bacillus sp., and Methanosarcina sp. increased in the recovered sludge. The imbalanced full-scale hybrid cover lagoon reactor was recovered within 15 days by dilution with biogas effluent at a ratio of 8:2 and a better result than the lab-scale test (36 days). Conclusion Dilution of the inhibited sludge with biogas effluent could recover the imbalance of the full-scale POME-biogas reactor with economically feasible and high biogas production performance.

Oil Palm Deseeded Fruit Head Ash: Fractionation and Characterization

The processing of palm oil from the fruits of the African oil palm generates an increasing amounts of solid waste. The production of beneficial products for various applications from the oil palm wastes would reduce the amount of unwanted materials produced and contribute to a healthier environment. In this research, fractions were derived from the filtrate of the oil palm deseeded fruit head ash by fractional crystallization. Their physicochemical properties, cation, and anion compositions were determined by standard methods. Three hygroscopic oil palm ash fractions, namely crystals, anhydrous, and sediment, were obtained from the filtrate of the soaked ash. The crystals fraction showed significantly higher mean values than the anhydrous and sediment in conductivity and total organic matter (p<0.0001 each), salinity (p<0.01 and p<0.0001), and total organic carbon (p<0.01), while anhydrous had higher total dissolved solids than the crystals (p<0.01) and sediments (p<0.05). pH and melting points for the crystals and anhydrous compounds were similar (11.07 and <330) and higher than that of the sediment (10.29 and 284.2). Compared to the crystals, anhydrous fractions reveal significantly lower values in iron, phosphate (p<0.01 individually), zinc, chloride, nitrate, and sulphate (p<0.05 each), while sediments had significantly higher zinc (p<0.05) and nitrate (p<0.0001) and lower iron, chloride (p<0.05 each), sulphate and phosphate (p<0.0001 respectively) mean values. From this study, the isolation of three fractions from the oil palm empty fruit bunch ash with different physicochemical properties and ionic compositions was achieved. These fractions may serve as useful resources for utilization in various fields of research and production processes.

Preparation and Characterization of Ultra-Fine Oil Palm Ash Powder by Ultrasonication and Alkaline Treatment for Its Evaluation as Reinforcing Filler in Natural Rubber

Ultra-fine oil palm ash (OPA) particles were successfully prepared using ultrasonication along with optimal chemical deagglomeration. The influence of chemical treatment by sodium hydroxide (NaOH) solution on the OPA particles was found to be an important factor in enhancing deagglomeration efficiency. The average particle size of the original OPA (41.651 μm) decreased remarkably more than 130 times (0.318 μm) with an obvious increase of Brunauer–Emmet–Teller (BET) surface area after treating the OPA with 3M NaOH, followed by ultrasonication for 30 min. The changes in particle size and surface morphology were investigated using transmission electron microscopy and scanning electron microscopy. Moreover, the chemical functional groups of the untreated and treated OPA showed different patterns of infrared spectra by the presence of sodium carbonate species owing to the effect of NaOH treatment. The incorporation of both untreated and treated OPA in natural rubber by increasing their loading can improve cure characteristics (i.e., reducing optimum cure time and increasing torques) and cure kinetic parameters (i.e., increasing the rate of cure and reducing activation energy). Nevertheless, the strength, degree of reinforcement, and thermal stability of treated OPA as well as wettability between treated OPA particles and NR were greater than that resulting from the untreated OPA.