Pretreatment Of Empty Fruit Bunch Research Articles

Chemical-free saturated steam pretreatment of oil palm empty fruit bunch for improved enzymatic saccharification

Oil palm empty fruit bunch (EFB) as the main lignocellulosic residue from the oil palm industry serves as suitable feedstock for enzymatic saccharification, yielding fermentable sugars. Due to complex inter-association between hemicellulose, cellulose and lignin within EFB lignocellulosic matrix, different saturated steam conditions at 140-230 °C, 0.3-2.3 MPa was chosen as a pretreatment strategy, targeted to hydrolyze hemicellulose and reduce crystallinity of cellulose to enhance enzymatic saccharification which need no chemical requirement and potential for energy recovery. As a result, SEM analysis of EFB morphology indicated that the enhanced silica body removal from 190-230 °C of saturated steam pretreatment correspondingly led to substantial 82% removal of hemicellulose. Consequently, enzymatic saccharification yielded between 0.621-0.637 g glucose per g EFB, equivalent to 93-95% of cellulose saccharification by Acremonium cellulase on EFB treated with saturated steam at 210-230 °C. Notably, a short duration pretreatment of EFB at 210 °C for 2 min was proved sufficient for high fermentable sugar production. The potential energy estimated for employing saturated steam pretreatment of EFB in a palm oil mill was sufficient by 2.2 x 1012 kJ/year.

Utilization of Empty Palm Fruit Bunches as a Carbon Source for Cellulase Production to Reduce Solid Waste from Palm Oil

Cellulase enzymes are widely used in textile, food, detergent, pulp and paper industries and biofuel, so the need for enzymes continues to increase every year. One of many biomass wastes found in Indonesia is empty fruit bunches (EFB) that can be used as a carbon source as a substitute for expensive pure cellulose (CMC) and Bacillus subtilis isolates. This study aims to obtain the optimum conditions the production of cellulase enzymes with variations in the pre-treatment of EFB and pH variations of the medium using Bacillus subtilis. Pre-treatment was carried out to hydrolysed lignocellulosic biomass was more easily and increased glucose levels which would enter the next production stage. Variations in pre-treatment were carried out by adding acids, bases and organosolv process, as well as variations in pH at 6.5; 7.0 and 7.5, respectively. Enzyme activity was calculated using the Nelson-Somogyi method. When using acid, the enzyme activity is 0.041, while using organosolv, it is obtained 0.057 each at pH 7. The results showed that the highest enzyme activity was obtained at a pH of 7.0 and a temperature of 40 ºC on EFB substrate pretreated with a base of 0.204 U/ml. These findings emphasize the potential benefits of using EFB waste as a substrate for cellulase enzyme production, by providing an alternative approach to decrease raw material expenses and mitigate environmental pollution.

Pretreatment of Empty Fruit Bunch using Various Choline Chloride-based Acidic Deep Eutectic Solvents

Pretreatment of Empty Fruit Bunch using Various Choline Chloride-based Acidic Deep Eutectic Solvents

Pyrolysis kinetic study of the thermal degradation of pre-treated empty fruit bunches

Empty fruit bunch (EFB) wastes are a significant source of biomass waste in Malaysia and have the potential to be a high-quality source of energy. This study aims to evaluate the kinetic of EFB biochar degradation and its characteristics under three conditions of washing pre-treatments. Prior to biochar production via slow pyrolysis process, stirring and soaking techniques were utilised as part of the pre-treatment for the washing process, with varying solid-to-liquid (S:L) ratios of 1:50, and 1:50 to 1:70, respectively. The study analysed the higher heating value (HHV), pyrolysis yield and kinetic activation energy of the biochar. The morphology and elemental composition of the biochar samples were determined using ultra-high resolution scanning electron microscopy (UHR-SEM) and energy dispersive X-Ray detector (EDX). The Coats-Redfern model was used to estimate the activation energies of the EFB biochar from thermogravimetric (TGA) data in a temperature range of 30 °C to 800 °C and a constant heating rate of 10 °C/min under a nitrogen atmosphere. The results showed that washing pre-treatment significantly changed the morphology and elemental compositions of the EFB biochar samples. The higher S:L ratio of 1:70 has a more significant impact on the breakdown of the lignocellulosic structure of EFB. The soaked samples had slightly lower biochar and bio-oil yields (22.73 mf wt. % to 24.86 mf wt. % and 27.97 mf wt. % to 39.39 mf wt. %, respectively) than the stirred samples (25.22 mf wt. % and 49.59 mf wt. %). The pre-treatment process improved the carbon content while reducing potassium by 60.7 to 81.39%. The HHVs of EFB-4 (28.24 MJ/kg) and EFB-3 (26.57 MJ/kg) were higher than those of EFB-2 (26.2 MJ/kg) and EFB-1 (23.14 MJ/kg), indicating an improvement in their fuel properties. The higher kinetic activation energies of EFB-4 (43.27 to 48.30 MJ/mol) indicate better thermal stability than the others. Therefore, concerning improved fuel properties, the recommended pre-treatment of EFB for the pyrolysis process is soaking at 90 °C with an S:L ratio of 1:70. The kinetic analysis revealed that the pyrolysis of pre-treated EFBs follows a multi-step reaction mechanism, with different activation energies for each stage. The obtained kinetic parameters can be used to optimize the pyrolysis process and design efficient pyrolysis reactors for the valorization of EFBs. Overall, this study provides valuable insights into the thermal behavior of pre-treated EFBs and their potential for bioenergy production.

Influence of Stirring Speed on Glucose and Ethanol Production in Simultaneous Saccharification and Fermentation Process

Lignocellulosic biomass has a potential to be coverted to bioethanol which can be a new alternative for fossil fuel. Empty fruit bunches (EFB) is one of the most abundant lignocellulosic biomass in Malaysia, which has high content of cellulose and posses favorable physiochemical characteristics for bioethanol production via a process called simultaneous saccharification and fermentation (SSF). In SSF process, the reaction is initiated by diffusion and consolidation of the enzyme and its substrate. Thus, optimum stirring speed is crucial, as diffusion rate of substrates is influenced by the agitation of reaction mixture. The influence of stirring speed on the glucose and ethanol concentration in SSF process was investigated in the current study. Initially, 5 % (g/ml) of pretreated EFB in 1.5 liter of 0.05 M buffer citrate pH 4.8 were sterilized in autoclave at 121°C for 20 minutes. Then, enzyme Cellic Ctec-2 solution with concentration (1%) were added together with 1.5% (g/ml) Saccharomyces cerevisiae yeast in the bioreactor. The process was conducted in the bioreactor under temperature of 37°C with stirring speed of 100 rpm for 72 hours. SSF process experiments were repeated with the same setup except by varying the stirring speed (150 and 200 rpm) independently. From the results, the glucose concentration and ethanol yield of 200 rpm indicated less concentration in every 24 hours compared to 150 rpm and 100 rpm. The stirring speed of 150 rpm shows the highest glucose concentration (1.914 mg/ml) and ethanol yield (16%) obtained after 72 hours and determined as the best stirring speed for this experiment.

Simultaneous Saccharification and Fermentation of Empty Fruit Bunches of Palm for Bioethanol Production Using a Microbial Consortium of S. cerevisiae and T. harzianum

A simultaneous saccharification and fermentation (SSF) optimization process was carried out on pretreated empty fruit bunches (EFBs) by employing the Response Surface Methodology (RSM). EFBs were treated using sequential acid-alkali pretreatment and analyzed physically by a scanning electron microscope (SEM). The findings revealed that the pretreatment had changed the morphology and the EFBs’ structure. Then, the optimum combination of enzymes and microbes for bioethanol production was screened. Results showed that the combination of S. cerevisiae and T. harzianum and enzymes (cellulase and β-glucosidase) produced the highest bioethanol concentration with 11.76 g/L and a bioethanol yield of 0.29 g/g EFB using 4% (w/v) treated EFBs at 30 °C for 72 h. Next, the central composite design (CCD) of RSM was employed to optimize the SSF parameters of fermentation time, temperature, pH, and inoculum concentration for higher yield. The analysis of optimization by CCD predicted that 9.72 g/L of bioethanol (0.46 g/g ethanol yield, 90.63% conversion efficiency) could be obtained at 72 h, 30 °C, pH 4.8, and 6.79% (v/v) of inoculum concentration using 2% (w/v) treated EFBs. Results showed that the fermentation process conducted using the optimized conditions produced 9.65 g/L of bioethanol, 0.46 g/g ethanol yield, and 89.56% conversion efficiency, which was in close proximity to the predicted CCD model.

Catalytic Co-Pyrolysis of Palm Oil Empty Fruit Bunch and Coal into Liquid Oil

The decline in fossil fuel sources has prompted research into finding renewable fuels. One of environmentally friendly energy sources with high efficiency is by producing liquid oil from palm oil empty fruit bunch (EFB) and coal. Pre-treatment of empty fruit bunches using NaOH and various concentrations of H2O2, various ratios of EFB/coal, the ratio of CaO catalyst, chemical and physical characteristics were studied to produce the better liquid oil yield. The H2O2 concentrations are 0%, 1%, 2%, and 3%. The ratios of EFB/coal (R) are 0/100, 25/75, 50/50, and 75/25. The ratios of catalyst CaO/raw material are 0%, 3%, 6%, and 9%. It ran at 400 °C with 100 mL/min nitrogen gas flowing during one hour. The results showed that adding sodium hydroxide and hydrogen peroxide in the EFB pre-treatment increased the liquid oil yield. With an increase in the EFB/coal ratio, the liquid oil yield increased. Co-pyrolysis treated EFB and Coal with a ratio of 75:25 produced 32% liquid oil yield, but the liquid oil yield decreased to 19% with the addition of 9% CaO catalyst. However, the addition of CaO catalyst reduces the acidity and increases the calorific value of the liquid oil.

Co-pyrolysis of empty fruit bunches impregnated with Ni and lignite into liquid oil

Oil produced from biomass pyrolysis is a potential fuel and can be used to overcome the energy crisis. However, this oil cannot replace transportation fuel because of its low calorific value. To improve the quality of oil, biomass pre-treatment and co-pyrolysis process were carried out. This study aimed to determine the influence of empty fruit bunches (EFB) pre-treatment using Ni(NO 3 ) 2 solution, the ratio of pretreated EFB and lignite, and the influence of the ratio CaO catalyst/raw material on yield and quality of liquid oil. EFB pre-treatment was performed by impregnation of EFB with Ni(NO 3 ) 2 solution at various concentrations of 0.1, 0.3, and 0.5 M at 25 °C for 24 h. The co-pyrolysis process was carried out at 400 °C and nitrogen gas was flowed with a flow rate of 100 mL/min for 50 min with various pre-treated EFB, the ratio of raw material EFB/lignite (100/0, 25/75, 50/50, 75/25, 0/100), and the ratio of CaO catalyst/raw material (2%, 5%, 8% w/w). The best liquid oil produced is from EFB pre-treatment using Ni(NO 3 ) 2 0.3 M at a raw material ratio of 75/25 EFB/lignite with the addition of 8% CaO catalyst with a yield of 32.3%, which has a density of 1.049 g/mL, the viscosity of 3.47 cSt, the heating value of 36.63 MJ/kg, and the pH of 2.5 with a liquid oil composition of 11.52% acetic acid, 0.47% phenol, 14.7% aldehydes, 46.9% alkane and 16.83% alkene.

Comparative assessment between hydrothermal treatment and anaerobic digestion as fuel pretreatment for industrial conversion of oil palm empty fruit bunch to methane and electricity-A preparation study to full scale

Presence of mineral elements in oil palm empty fruit bunch (EFB) biomass is the major cause of slagging and fouling that lower the efficiency of power plant boilers. Two EFB pretreatment methods, hydrothermal treatment (HTT) and anaerobic digestion (AD), were assessed under industrially feasible conditions, aiming to concurrently improve fuel properties and recover biomethane. For HTT, multivariate regression was employed to establish the model of the key mineral “potassium (K) remaining in EFB” with liquid-to-solid ratio (L/S), reaction time (RT) and temperature. K-removal highly responded to RT while temperature and L/S appeared to play a secondary role. Highest K-removal was 90.7% at 120 °C, RT 120 min, and L/S 20:1. The organics release (100.7 g/kgEFB) in HTT leachate, able to use in various sugar biorefinery pathways, was also assessed for the biomethane generation. For industrial practicality, the treated wastewater (from palm oil mill treatment system) was subsequently tested for HTT under the lowest L/S of 5:1. K-removal at 90.9% and leachate methane yield at 29.1 m3CH4/tonEFBdry were achieved, together with oilrecovery from EFB at 70.6%. For AD of EFB, it was also found efficient in removing K at 92.6% and posed a remarkable methane yield of 117.5 ± 1.4 m3CH4/tonEFBdry. Potassium was, however, reabsorbed to EFB fiber after 14 days of fermentation, and importantly no oil was recovered. While both methods could improve EFB properties and ensure a lower fouling/slagging tendency in boilers, energy and mass balance suggests that the additional oil recovery by HTT provided a clear advantage over AD as well as its ease of integration to existing plant.

Comparative study of the synergistic effect of decanter cake (DC) and empty fruit bunch (EFB) as the co-substrates in the anaerobic co-digestion (ACD) of palm oil mill effluent (POME)

Due to rapid depletion of non-renewable energy such as fossil fuel and increasing concerns for green environment, collection of biogas generated from palm oil mill effluent (POME) would be advantageous as source of energy. In this study, empty fruit bunch (EFB) and decanter cake (DC) were used as co-substrates separately with POME to enhance biogas production. Three parameters were evaluated for this experiment, including DC:POME ratio/EFB:POME ratio (in term of volatile solids (VS)), DC/EFB pre-treatment and mixing speed. It was observed that the anaerobic co-digestion (ACD) of DC and POME showed promising reduction in Chemical Oxygen Demand (COD) (>95%), total solids (>74%), VS (>90%), total suspended solids (>90%), volatile suspended solids (>92%) and volatile acid (>83%). The overall improved methane production results show that synergistic effects are observed for both co-substrates, i.e. DC and EFB. EFB was a better co-substrate than DC due to its higher methane yield improvement percentage as compared to mono-digestion of POME. The best ratio obtained for EFB:POME was 0.6:1 with improvement of 2.36 times more than mono-digestion of POME. It is also found that with increasing mixing speed, the methane production can be further improved. Preliminary cost analysis shows that EFB is a promising feedstock for ACD with POME, when considering in terms of technical (i.e. methane yield) and economic efficiencies (i.e. methane productivity and pre-treatment cost). Future works would be focused on the comprehensive optimization of the DC:EFB:POME co-digestion, particularly the improvement of the EFB pre-treatment method and settling characteristics of the digested sludge.

Insight into the deep eutectic solvent pretreatment of oil palm empty fruit bunches: Effects of temperature, empty fruit bunch to solvent ratio, and time

This work aimed to comprehensively examine the pretreatment efficiency of oil palm empty fruit bunches (EFB) using two different types of deep eutectic solvent (DES) mixtures, i.e., choline chloride/imidazole (DES-I) and choline chloride/glycerol (DES-G) in terms of pretreated EFB structural composition and enzymatic hydrolysis. The influence of the pretreatment temperature (55 °C, 90 °C, 125 °C, 160 °C, and 195 °C), EFB to solvent ratio (1:5, 1:10, 1:15, and 1:20), and pretreatment time (2 h, 4 h, and 6 h) on the performance of pretreated EFB and the generated black liquor was examined. The optimal conditions for EFB pretreatment were 160 °C, 1:5 ratio, and 2 h using DES-I solvent, and 160 °C, 1:10 ratio and 4 h using DES-G solvent. The structural carbohydrates of empty fruit bunch pretreated with DES-I, DES-I EFB1 and DES-G, DES-G EFB2 increased to 66.1%, and 64.6%, respectively. The enzymatic hydrolysis of DES-I EFB1 resulted in higher glucan conversion (92.4%) compared to DES-G EFB2, indicating that DES-I solvent was more efficient than DES-G for EFB pretreatment. X-ray diffraction, Fourier transform infrared spectroscopy, and variable-pressure scanning electron microscopy confirmed the removal of lignin and hemicelluloses from EFB during pretreatment and enzymatic hydrolysis.

Kinetic and dynamic analysis of ozonolysis pre-treatment of empty fruit bunch in a well-mixed reactor for sugar production

Pre-treatment is the key step in biorefinery for enhancing cellulose accessibility from lignocellulosic biomass (LB) such as empty fruit bunch (EFB), which contains highly valuable cellulose. Ozonolysis pre-treatment appears as a promising green alternative for isolation of EFB to cellulose. This study develops the diffusion–reaction model of EFB ozonolysis inside a well-mixed novel OzBiONY® ozonolysis reactor at lab scale production. The mathematical model is numerically solved using COMSOL Multiphysics® software. Kinetic reaction parameters are computationally estimated via gradient-based Sparse Nonlinear Optimizer (SNOPT) method with sequential quadratic programming (SQP) algorithm. The evolution of ozone velocity and concentration profiles inside the reactor are simulated by computational fluid dynamics (CFD) method to study the effect of biomass particle sizes. The larger particle size consumes higher ozone (k1 = 2.23 m3/mol∙s) compared to the smaller particle size (k1= 0.09 m3/mol∙s). This reveals that larger biomass particle confers faster delignification rate and a much higher degradation of insoluble lignin. The simulation results demonstrate ozone velocity at the surface of larger particle is lower, but the surface concentration of ozone is higher. The diffusion–reaction model of EFB ozonolysis elucidates the plausible reaction pathway of lignin degradation via ozonolysis pre-treatment with minimum objective function (Z) of 1.41 × 10−3. From experimental results, the highest lignin degradation is 78 wt.% and the highest glucose yield is 12 wt.%. The outcomes of this research will contribute to the development of smart biorefinery technology and systems for sugar production in a sustainable and circular economy.

Biogas production enhancement by co-digestion of empty fruit bunch (EFB) with palm oil mill effluent (POME): Performance and kinetic evaluation

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.

High-titer bio-succinic acid production from sequential alkalic and metal salt pretreated empty fruit bunch via simultaneous saccharification and fermentation

Bio-succinic acid is produced from inorganic salt pretreated oil palm empty fruit bunch (OPEFB) for the first time through simultaneous saccharification and fermentation (SSF). OPEFB is an agriculture waste that can be converted into succinic acid (SA) which is a high value added product sought after in the chemical industry. In this study OPEFB is pretreated using sequential inorganic salt (sodium phosphate dodecahydrate and zinc chloride) before undergoing SSF using Actinobacillus succinogenes ATCC 55618. Parameters that influenced the SA production such as substrate loading, inoculum size and enzyme loading are investigated using design of experiments. The results revealed that biomass loading and enzyme loading have significant impact in SA yield. Under condition of 100 g/L biomass, 5% inoculum and cellulase enzyme 40 FPU/g OPEFB, maximum concentration of SA (65.2 g/L) and yield (0.65 g/g OPEFB) are obtained. Subsequently the model developed for predicting SA production has been successfully validated.

Development of a novel reactor for simultaneous production of biogas from oil-palm empty fruit bunches (EFB) and palm oil mill effluents (POME)

A novel reactor was developed in this research to simultaneously produce biogas from solid- and liquid-state anaerobic digestions in one container for the first time. Excess heat from the outer liquid-state anaerobic digestion (OL-AD) of POME was transferred to the inner solid-state anaerobic digestion (IS-AD) of EFB for promoting thermophilic digestions (55 °C and 70 °C). Continuous operations at various hydraulic retention times were performed. Bacteria and archaea communities were identified. The results showed that the maximum methane yields were 507.07 and 125.84 mL-CH4/g-VS for OL-AD and IS-AD, respectively. In OL-AD, raising temperature increased the methane yield by 6.4%. In IS-AD, the yield was not significantly affected by elevated temperature. However, the pretreatment of EFB with NaOH increased the methane yield by 14.1%. The main bacteria and archaea communities in OL-AD and IS-AD were found similar. The novel reactor could save energy, reduce costs and digester space, and increase the methane yield.

Consolidated bioprocesses for efficient bioconversion of palm biomass wastes into biodiesel feedstocks by oleaginous fungi and yeasts

Consolidated bioprocesses for bioconversion of lignocellulosic biomass into biodiesel feedstocks were developed. Palm empty fruit bunch (EFB) was biologically pretreated coupling with fungal lipid production (121.4 ± 2.7 mg/g-EFB) by lignocellulolytic oleaginous fungi prior to lipid production by oleaginous yeasts. In subsequent separate hydrolysis and fermentation (SHF) of fungal pretreated EFB (FPEFB), the oleaginous yeast with the maximum lipid yield of 37.0 ± 0.1 mg/g-FPEFB was screened. While a higher lipid yield of 47.9 ± 1.5 mg/g-FPEFB was achieved in simultaneous saccharification and fermentation (SSF) with less enzyme requirement. Fed-batch SSF of non-sterile FPEFB was proven as a practical and efficient strategy to increase lipid yield up to 53.4 ± 0.5 mg/g-FPEFB. Total lipid yield by both fungi and yeast was 165.0 ± 4.4 mg/g-EFB. Interestingly, the consolidated bioprocesses of enzyme and lipid production also achieved comparable total lipid yield of 149.3 ± 6.6 mg/g-EFB. These strategies may contribute greatly to cost-effective and sustainable bioconversion of lignocellulosic biomass into biodiesel feedstocks.

Synergistic ultrasound-assisted organosolv pretreatment of oil palm empty fruit bunches for enhanced enzymatic saccharification: An optimization study using artificial neural networks

The efficiency of ultrasonic-assisted organosolv in pretreating oil palm empty fruit bunches (EFB) was investigated in this study. The effect of temperature, time, sonication power, ethanol concentration and presence of different types of catalysts were examined. The ultrasonic-assisted organosolv pretreatment was found to be significantly affected by temperature, time and sonication power. These parameters were further subjected to process optimization study using Leverburgh Marquee artificial neural networks (ANNs). An empirical model with good predictive accuracies (R-squared value of 0.9084) was generated. From the morphology study, pretreated EFB showed significant structural disruption through the breakage of hemicellulose and lignin bonds, leading to the enhancement of enzymatic saccharification. A maximum reducing sugars of 356 mg/g biomass (7.12 g/L) was obtained at optimized conditions of 48.2 °C, 30 min and 55% (192.5 W) sonication power. The relatively high yield of reducing sugars associated with lower lignin content compared to raw EFB also suggested the effectiveness of ultrasonic-assisted organosolv in pretreating EFB. Therefore, this synergistic approach could pave the way for a more efficient and cost-effective pretreatment process for the production of various bioproducts and biofuels in the future.

Isobutanol production from empty fruit bunches

Although isobutanol has been successfully produced from glucose-based media by various microbes, only a few studies have reported isobutanol production from lignocellulosic biomass. In this study, the feasibility of producing isobutanol from hydrothermally-pretreated empty fruit bunches (EFBs) was analyzed. Firstly, the Escherichia coli JK209 strain was constructed; subsequently, optimal fermentation conditions for isobutanol production using this strain were determined. Next, the raw EFBs were hydrothermally pretreated at 190 °C for 15 min, and the pretreated EFBs were hydrolyzed using 10 FPU of cellulase/g glucan. Finally, the resulting hydrolysate was fermented at 25 °C for 84 h, and isobutanol give rise to the yield of 0.26 g isobutanol/g glucose. These results imply that 80.1 g of isobutanol could be produced from 1 kg dry weight of EFBs. To our knowledge, this is the first feasibility study of isobutanol production from pretreated EFBs.

Evaluation of mechanical-green solvent pretreatment of oil palm wastes for reducing sugars production in North-Colombia

The aim of this work was to define optimum conditions to perform the mechanical and chemical pretreatment of empty fruit bunches (EFBs) and kernel shell (KS). Mechanical pretreatment was based on particle size reduction to 0.5, 1, and 2 mm. For chemical pretreatment, a solution of urea (2, 4, and 6 %w/v) was added to the residues under stirring for 18 h and 80 °C. Then, samples were hydrolyzed with sulfuric acid and the resulting reducing sugars were quantified using the 3,5- dinitrosalicyclic acid method. In addition, Van Soest and FTIR analyzes were performed to characterize the biomass suggesting acceptable cellulose contents (EFBs: 36.47%; KS: 20.06 %) and high lignin values (EFBs: 31.27%; KS: 66.49%). Results showed that the highest amount of TRS for EFBs was 105.3 g/L with urea concentration of 4% w/v and a particle size of 0.5 mm. For the KS, the highest amount of TRS was 98.62 g/L using a urea concentration of 6% w/v and a particle size of 0.5 mm. According to these results, it was concluded that pretreatments of oil palm biomass significantly enhance the performance of lignocellulosic material conversion into reducing sugars.

Experimental and modelling study of the torrefaction of empty fruit bunches as a potential fuel for palm oil mill boilers

Empty fruit bunches (EFBs) in the current bulky form are low in energy density and highly moist making them an unattractive option as a solid fuel for producing steam and electricity in palm oil mill biomass boilers. Pre-treatment of EFBs using torrefaction is required in order to improve its energy density via reduction of moisture and oxygen contents, which eventually will lead to an increased high heating value (HHV). In this study, the experiments were conducted in a fixed bed reactor at different feedstock moisture contents (10–67 wt%), residence times (30 and 60 min), and a torrefaction temperature of 270 °C. The distribution of torrefaction products, structural and fuel properties of the torrefied EFBs were investigated with multiple techniques. The results showed that the decrease in the moisture content of feedstock led to a significant increase in the yield of torrefied EFBs. The decrease in moisture content also resulted in increased energy yield and HHV of torrefied EFBs from 52.2% to 99.3% and 18.2–19.2 MJ/kg, respectively. The obtained results were then fitted to a power model to estimate the mass and energy yields of torrefied EFBs at different moisture contents and residence times by using the least squares method. Empirical equations generated by the developed model were accurate and can obtain a satisfactory fit to the experimental data, with the coefficient of determination values higher than 0.96. The calculated energy and carbon stored from the torrefied EFBs offer additional income, clean power, and less pollution in palm oil milling.