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The palm oil industry is gearing itself towards sustainability by implementing mandatory biogas capture for all palm oil mills in the effort to reduce greenhouse gases. This action also indicates that the anaerobic digestion of palm oil mill effluent (POME) will be one of the essential sources of biogas for energy generation. However, the availability of POME is limited during the low crop season due to the lower palm oil production. Concurrently, the solid wastes known as empty fruit bunches (EFB) are also produced from the oil mill. EFB has vast potential for power generation, though it is currently not being fully utilized. Therefore, this work aims to enhance the biogas production from anaerobic co-digestion (ACD) of EFB with POME by evaluating the effect of alkaline pretreatment of EFB, EFB-to-POME ratio, and temperature on the methane yield. The optimum EFB:POME ratio is 0.6:1 as the methane production of this ratio at both thermophilic and mesophilic conditions are relatively high (up to 74.02 ml CH4/g VS). Results show that ACD performs 2.36 times better than mono-digestion of POME at mesophilic conditions. The modified Gompertz model could predict the process behavior of the ACD of EFB with POME with high R2 (>0.95). Further investigation on other potential pretreatment methods and synergism analysis of co-digestion, which provides a balance between efficiency and economy could be carried out. The impact of this work will be towards a sustainable environment, which will significantly reduce the environmental impacts of palm oil production.

Palm oil plays a vital role as edible vegetable oil for daily human consumption. However, the process technologies and the quality of palm oil produced have remained stagnant for the past decades. ...

The treatment of palm oil mill effluent (POME) has always been the topic of research in Malaysia due to the high concentration of total suspended solid (TSS) and oil and grease (O&G) ranges from 28 846 to 30 920 mg/L and 5614 to 8812 mg/L, respectively. Additionally, the release of methane gas during the treatment of POME in all of the palm oil mills has been the major contributor to greenhouse gas (GHG) effect. The main aim of this work is to evaluate the performance of the pilot-plant integrated anaerobic–aerobic bioreactor (IAAB) for POME treatment at two different phases: (a) startup and (b) long-term performance evaluation from an organic loading rate (OLR) of 10.5 to 32.5 gCOD/(L·day). Startup of the pilot-plant IAAB was successfully accomplished in 24 days with overall removal efficiencies in terms of biochemical oxygen demand (BOD), chemical oxygen demand (COD), and total suspended solid (TSS) of at least 90% at the OLR of 8.0 gCOD/(L·day). The pilot-plant IAAB achieved high BOD, COD, and TSS removal efficiencies of more than 99% for OLR up to 30.0 gCOD/(L·day) with methane yield ranges from 0.0406 LCH₄/gCODᵣₑₘₒᵥₑd to 0.1312 LCH₄/gCODᵣₑₘₒᵥₑd. The effluent quality remained stable with BOD of 16–107 mg/L with a high percent of compliance with the discharge limit of 100 mg/L. The coupling of the Grau second-order and Stover–Kincannon models (anaerobic system) with the Stover–Kincannon model (aerobic system) will completely define the pilot-plant IAAB system. This pilot-plant research will provide valuable data and experiences required to design and commission a full-scale IAAB.

This chapter identifies the potential of using an efficient biogas prototype known as integrated anaerobic-aerobic bioreactor (IAAB) system for the treatment of palm oil mill effluent (POME). Additionally, design procedures and design considerations of the IAAB will be discussed in detail as well. The IAAB system implicates a small footprint, shorter hydraulic retention time (HRT), and ability to treat liquid effluent at high loading rates as compared to the conventional biogas technologies. The positive results obtained by the laboratory-scale IAAB (COD removal and total suspended solid [TSS] removal more than 99%) results in upscaling the volume of the IAAB from 55 L to 1.8 m3. It will act as a commercialization prototype for the palm oil industry to accept such a new approach to combat the massive volumes of POME produced daily and unstable characteristics of POME obtained during low- and high-crop seasons of fresh fruit bunch (FFB). Positive results were obtained whereby the IAAB was successfully operated at an organic loading rate (OLR) of 30.0 gCOD/L.day with overall removal efficiency of >99%. Additionally, the final treated effluent produced abides the discharge limit with biochemical oxygen demand (BOD) less than 20 mg/L. This integrated system follows the concept of zero liquid discharge, whereby all liquid biomasses in the palm oil mill are converted into valuable products, and thus transforming the palm oil industry into a “green industry.”

Anaerobic digestion has been widely employed in waste treatment for its ability to capture methane gas released as a product during the digestion. Certain wastes, however, cannot be easily digested due to their low nutrient level insufficient for anaerobic digestion, thus co-digestion is a viable option. Numerous studies have shown that using co-substrates in anaerobic digestion systems improve methane yields as positive synergisms are established in the digestion medium, and the supply of missing nutrients are introduced by the co-substrates. Nevertheless, large-scale implementation of co-digestion technology is limited by inherent process limitations and operational concerns. This review summarizes the results from numerous laboratory, pilot, and full-scale anaerobic co-digestion (ACD) studies of wastewater sludge with the co-substrates of organic fraction of municipal solid waste, food waste, crude glycerol, agricultural waste, and fat, oil and grease. The critical factors that influence the ACD operation are also discussed. The ultimate aim of this review is to identify the best potential co-substrate for wastewater sludge anaerobic co-digestion and provide a recommendation for future reference. By adding co-substrates, a gain ranging from 13 to 176% in the methane yield was accomplished compared to the mono-digestions.

The characteristics of Palm Oil Mill effluent (POME) have captivated attention in harnessing its high organic contents to generate biogas via anaerobic digestion. However, biogas production is unstable during low crop season. Therefore, this research focuses on improving the biogas generation by adopting the co-digestion method which treats POME and Decanter cake (DC) simultaneously. Results show that DC:POME ratio of 0.8:1 (in term of volatile solids (VS)) with organic loading of 11 g VS/L and HRT of 28 days generated the highest methane yield of 0.515 L CH4/g VS, which is a 186% improvement as compared to mono-digestion of POME. The co-digestion of substrates has shown good biodegradability of organic contents where up to 99.42% chemical oxygen demand (COD) and VS removal efficiencies were attained. Logistic Function Model (LFM) is the most suitable model to predict the performance of co-digestion with the highest R2 of 0.9810.

Palm oil mill effluent (POME) is the primary source of water pollution in the oil palm industry. Most palm oil mills are employing a series of anaerobic and aerobic ponds for POME treatment, in order to comply with environmental regulation. In recent years, some mills are installed with biogas capture facilities in order to reduce the emission of greenhouse gas, as well as to raise some profits. In this work, a covered lagoon process for POME treatment, coupled with biogas production was modelled using commercial process simulation software SuperPro Designer v9.0. The simulation results revealed that 29 m3 of biogas can be produced per tonne of treated POME, with a removal efficiency of 92 % for its chemical oxygen demand (COD). Cost analysis has proven that the process is economically viable, with a net present values of $ 2,830,000, IRR of 14.3 %, and payback time of 4.66 years. Process optimisation revealed that the optimal recycle ratio of sludge should be set to 30 %, where the minimum net expenditure ($11,812/y) is achieved, with final effluent COD content of 18 ppm. Note that this takes into consideration of the trade-off between capital and operating costs.

Palm oil mill effluent has been extensively researched via three different technologies, namely chemical, physicochemical and biological treatment methods. Biological treatment by anaerobic and aerobic means is currently the most commonly used method for palm oil mill effluent. However, the greatest challenge posed by them is the inconsistent biological oxygen demand of 20 mg/L for the final treated effluent. Large amount of investment for additional polishing plant prior to the final discharge has been utilised intentionally to further reduce the biochemical oxygen demand values, but the problem remains unresolved. The performance of current palm oil mill effluent treatment system deployed by the industry was evaluated by comparing two different types of anaerobic treatments: open ponding and covered lagoon systems (with hydraulic and gas mixing). The covered lagoon with hydraulic mixing achieved the highest chemical oxygen demand, total suspended solids, total volatile solids and lignin removal efficiencies of >80% compared to other systems which showed

Oil and grease, carbohydrate, protein, and lignin are the main constituents of high strength wastewaters such as dairy wastewater, cheese whey wastewater, distillery wastewater, pulp and paper mill wastewater, and slaughterhouse wastewaters. These constituents have contributed to various operational problems faced by the high-rate anaerobic bioreactor (HRAB). During the hydrolysis stage of anaerobic digestion (AD), these constituents can be hydrolyzed. Since hydrolysis is known to be the rate-limiting step of AD, the overall AD can be enhanced by improving the hydrolysis stage. This can be done by introducing pretreatment that targets the degradation of these constituents. This review mainly focuses on the biological pretreatment on various high-strength wastewaters by using different types of enzymes namely lipase, amylase, protease, and ligninolytic enzymes which are responsible for catalyzing the degradation of oil and grease, carbohydrate, protein, and lignin respectively. This review provides a summary of enzymatic systems involved in enhancing the hydrolysis stage and consequently improve biogas production. The results show that the use of enzymes improves the biogas production in the range of 7 to 76%. Though these improvements are highly dependent on the operating conditions of pretreatment and the types of substrates. Therefore, the critical parameters that would affect the effectiveness of pretreatment are also discussed. This review paper will serve as a useful piece of information to those industries that face difficulties in treating their high-strength wastewaters for the appropriate process, equipment selection, and design of an anaerobic enzymatic system. However, more intensive studies on the optimum operating conditions of pretreatment in a larger-scale and synergistic effects between enzymes are necessary to make the enzymatic pretreatment economically feasible.

Palm oil mill effluent (POME) with average chemical oxygen demand (COD) and biochemical oxygen demand (BOD) of 70,000 and 30,000 mg/L, respectively, can cause serious environmental hazards if discharged untreated. There are conventional palm oil mill effluent (POME) treatment systems that require large footprint, long HRT and fail to meet the Malaysian Department of Environment (DOE) discharge limit. Hence, the current research is aimed to design a novel integrated anaerobic–aerobic bioreactor (IAAB) for POME treatment in order to overcome these shortcomings of the conventional system. IAAB is a new bioreactor configuration which integrates anaerobic and aerobic digestion in one reactor. The overall removal efficiencies in steady state condition in terms of chemical oxygen demand (COD), biochemical oxygen demand (BOD) and total suspended solids (TSS) were more than 99% at the organic loading rate (OLR) of 10.5 g COD/L day with methane yield of 0.24 L CH4/g COD removed. The effluent quality remained stable (BOD < 70 mg/L) and complied with the discharge limit (BOD < 100 mg/L). Overall, the IAAB system exhibited good stability and pH adjustment was unnecessary. The results show that the IAAB achieves higher performance in terms of organic removal efficiency and methane yield at higher OLR and shorter HRT as compared to the conventional system. Further evaluations of its long-term performance are proposed for the subsequent study.

This research is aimed at improving the thermophilic aerobic treatment system of anaerobically digested palm oil mill effluent (POME) through optimization of mixed liquor suspended solids (MLSS) at high concentration range for the first time besides other parameters of organic loading rate (OLR), dissolved oxygen (DO) concentrations and settling time. Chemical oxygen demand (COD), biochemical oxygen demand (BOD) and total suspended solids (TSS) removal ratios were measured as indicators of the system performance. Experimental results clearly indicate that MLSS and OLR are the crucial parameters in thermophilic aerobic treatment. Optimal COD, BOD and TSS removals up to 86%, 87% and 89%, respectively, were achieved with MLSS concentration and OLR of 27,000 mg/L and 2.5 g COD/(L day), respectively. More significantly, high MLSS concentration range which is yet to be reported was successfully applied and this has resulted in superior performance as compared to other thermophilic treatment studies. No significant improvement of the treatment efficiency was attained with DO concentration exceeding 5 mg/L and settling time up to 24 h. Hence, operation at DO concentration of 2 mg/L and settling time of 2 h gives a good compromise between effluent quality and system operating costs.

Aerobic treatment of wastewater under thermophilic conditions has received growing interest in recent years. Because of the high discharge temperature (75 to 85 °C) of palm oil mill effluent (POME), it would be more economical if POME were treated thermophilically, as then cooling facilities prior to biological treatment can be eliminated. In the present investigation, the feasibility of thermophilic aerobic biological treatment as a suitable post-treatment system for anaerobically treated POME was examined. Also, the effects of temperature on the treated effluent quality were investigated by using sequencing batch reactors (SBRs) under mesophilic (28 °C) and thermophilic (45, 50, and 55 °C) conditions. The average total COD (TCOD) removal efficiencies varied from 55 to 98% at organic loading rates (OLR) of 2.6 to 4.5 kg COD/m3·day, dissolved oxygen (DO) concentrations of 2.9−4.5 mg/L, and mixed-liquor suspended solids (MLSS) concentrations of 22500−24200 mg/L. The results show that the thermophilic aerob...

Thermophilic treatment of palm oil mill effluent (POME) was studied in a novel integrated anaerobic-aerobic bioreactor (IAAB). The IAAB was subjected to a program of steady-state operation over a range of organic loading rate (OLR)s, up to 30 g COD/L day in order to evaluate its treatment capacity. The thermophilic IAAB achieved high chemical oxygen demand (COD), biochemical oxygen demand (BOD) and total suspended solids (TSS) removal efficiencies of more than 99% for OLR up to 18.5 g COD/L day. High methane yield of 0.32 LCH(4) (STP)/g COD(removed) with compliance of the final treated effluent to the discharge limit were achieved. This is higher than that of the mesophilic system due to the higher maximum specific growth rate (μ(max)) of the thermophilic microorganisms. Besides, coupling the model of Grau second order model (anaerobic system) with the model of Monod (aerobic system) will completely define the IAAB system.