Fatty acid methyl ester synthesis from palm sludge as potential feedstock for biodiesel.
Production of biofuels has drawn much interest by scientist to increasingly search for new economically feasible ways to produce biofuels from renewable sources, being biodegradable, nontoxic and low pollutant emission [1-4]. Among the renewable and sustainable biofuels, biodiesel produced from any oil bearing plant, vegetable oil or animal tallow [4-8] has been identified as a key technology to substitute petroleum based diesel fuels. Presently, biodiesel is produced from soy bean, vegetable oil, sunflower oil, rape seed oil, palm oil, Jatropha oil and waste oil [6-10] and . However, the production of biodiesel from edible food crops has sparked the controversial of food versus fuel issue [5,6]. Thus, it is necessary to explore new materials that are economically competitive, able to generate in large volume to cater the energy demands and does not competes with food production for consumptions. An alternative way is sought out by using inedible oil and/or microalgae oil  as a feedstock for biodiesel production. Lately, biodiesel production derives from biomass such as sewage sludge [1, 3, 11, 13, 14, 15] and palm sludge  has emerged as a potential feedstock for this purpose. Production of biodiesel from sludge is forecasted to become of one of the potential sources of energy in the years to come. This study is geared to investigate the potential of biodiesel production from palm oil mill effluent sludge.
MATERIALS AND METHODS
Sample collection and preparation:
Samples sludge was acquired from palm oil mill located in Bota, Perak. Sampling of the biomass was collected at the effluent retention pond. The samples sludge collected were dried at 105[degrees]C for 24 hour. The dried sludge was crushed into powder and stored in a container prior use.
Ultrasonic Aided In situ transesterification:
The ultrasonic aided in situ transesterification was carried out using 10g of dried sludge suspended into methanol containing acid catalyst in a screw cap vessel. Catalyst loading was kept constant at 12v/v% H2SO4. The experimental were carried out in a series varying mass ratio of methanol to dried sludge, reaction time and temperature. The vessel containing the reaction mixture was conducted in the ultrasonic bath. An aliquot of nhexane was added to each of the reaction vessel to enhance the lipid solubility. After the in situ transesterification, a 50ml of n-hexane was added to the reaction mixture and was centrifuged at 3000 rpm for 10 minutes. The supernatant was transfer to a separation funnel. Further extractions were repeated 3 times for 15 minutes. Later, the extracts were washed with warm distilled water to remove excess traces of acid catalyst and methanol. The bottom layer is discarded and the upper layer was then dried over anhydrous sodium sulphate. The FAME samples collected were stored in a container for further analysis. A series of reactions parameters is repeated varying different reaction temperature, time, and amount of catalysts and mass ratio of alcohol to sample.
Fourier transform infrared spectroscopy (FTIR):
The FAME samples collected were analyzed using a Perkin Elmer FTIR equipped with an attenuated total reflectance (ATR) accessory. All spectra were collected by co-addition of 32 scans at a resolution of 4cm-1 in the range of 4000 to 650cm-1. Prior to data collection of each sample, a background spectrum was collected; the ATR crystal was cleaned with ethanol to remove any residual contribution of the previous sample. The samples were analyzed by putting a few drops of samples completely covering the surface of the ATR crystal.
Gas chromatography- Mass Spectroscopy (GC-MS):
FAME analysis was performed using a GC-MS coupled with flame ionization detector and equipped with BPX70 capillary column (60m x 0.32 mm i.d; 0.25 [micro]m film thickness). The oven temperature was set at 115[degrees]C, raised to 180[degrees]C at rate of 8[degrees]C/min and held for 10min and finally raised to 240[degrees]C at rate of 8[degrees]C/min and held for 10min. An auto sample injection was set at 1[micro]L and flush through with carrier gas at rate of 1.6ml/min. Identification of methyl ester were made by comparison of retention time with the standard FAME mixture and compare to the mass spectra library. The yield of FAME is determined using Eq. 1.
Yield of FAME = [Mass of FAME (mg/L)/Mass of sample (mg/L)] x 100%
RESULTS AND DISCUSSION
Effect of methanol to sample ratio, reaction time and temperature on FAME yield:
In this study, different reaction conditions were conducted and the FAME yield is illustrated in Fig1 (a) & (b). In this process, the methanol to sample ratio, reaction time and temperature were varied from 8:1 to 12:1, 30-60 minutes and 60 [degrees]C to 70 [degrees]C respectively while the catalyst loading was kept constant at 12v/v% H2SO4 (Fig.1 (a) & (b)). The amount of methanol addition had the influence on the FAME yield giving the highest yield from 12:1 methanol to sample ratio (Fig.1 (a) & (b)). The FAME yield increased steadily from 63.47% to 65.29% with the increased of reaction time (Fig.1 (b)). As shown in Fig. 1(b), the FAME yield start reaching to plateau in between 60 minutes to 120 minutes as observed in 8:1 and 12:1 methanol to sample ratio. However, the yield decreases remarkably with further increase of methanol addition giving the lowest yield of 63.11% with reaction time of 120 minutes. Improvement of FAME yield was observed with the increasing reaction temperature from 60 [degrees]C to 70 [degrees]C. Highest FAME yield was attained at 60.33% for 60 [degrees]C and 65.29% for 70 [degrees]C, both from 12:1 methanol to sample ratio and reaction time of 120 minutes (Fig.1 (a) & (b)). Comparing with both temperatures, the highest yield was best achieved at 70 [degrees]C for molar ratio of 12:1.
FAME characterization Using FTIR:
The importance of infrared (IR) spectroscopy in the identification of molecular structures originates from the information content obtained and the possibility to assign certain group frequency wavenumber (cm-1) related to its functional groups [18-19]. In lipid, most of the peaks and shoulder are attributed to the specific functional groups . Fig. 2 showed the spectra derived from palm oil sludge after in situ transesterification with reaction conditions at 70[degrees]C, 12v/v% H2SO4 and 120 minutes. The spectra presented, showed the features of the FAME characteristic where it reveals two strong ester peaks at around 1747 cm-1 (the C=O vibration) [20, 21] and at around 1170 cm-1 corresponded to methyl group near carbonyl group (C-O vibration) [20, 22, 23]. The banding regions at 1236 - 1096 cm-1 correspond to stretching vibrations of C-O ester group [20, 22, 23]. While the out of plane bands were observed at 942 cm-1 and 916 cm-1 indicating the presence of HC=CH-(cis). The bending vibration of CH2 groups was observed at 1378 cm-1  and band at 1460 cm-1 shows the bending vibrations of CH2 and CH3 aliphatic groups [18, 24]. The range observed at 3025 - 2800 cm1 are region for C-H stretching of fatty acid hydrocarbon chains .
Fig. 3 illustrates the FAME profile of different lipid configuration presence in palm oil sludge with the effect of different methanol to sample ratio at fixed reaction conditions: 70 [degrees]C, 12v/v% H2SO4 and 120 minutes. The FAME of C14:0, C16:0, C18:0, C18:1n9c, C20:0 and 18:2 were consistently presence in all samples. The predominant FAME profiles are the saturated 16C chain length for C16:0 which accounts for 39 53% mol/mol followed by the unsaturated 18C chain length for C18:1n9c achieved at 31-37% mol/mol. However, a small fraction of unsaturated C18:1n9t (5-7% mol/mol) was only observed for methanol to sample ratio of 14:1. Other FAME that could not be detected significantly were C21, C22, and C20:2 and C20:3n6. The amount presence for these long chain fatty acid was less than 1% mol/mol. The proportions of saturated FAMEs were higher than those unsaturated FAMEs. The results revealed that the lipid contained in palm sludge has the viability for biodiesel production through the in-situ transesterification of lipids to FAME.
The in-situ transesterification of palm oil sludge was investigated with different reaction conditions to determine the amount of yield obtained. The best yield was 65.29% at 70 [degrees]C, 12:1 and 120 minutes. From this study, different reaction conditions employed will impact on the fraction of FAME profile. The fatty acid fractions obtained were mainly C16:0 followed by C18:1n9c. Lower yield obtained may be due to the insufficient reaction time and temperature. Further investigation need to be carried out to optimize the production yield.
Received 25 September 2014
Received in revised form 26 October 2014
Accepted 25 November 2014
Available online 31 December 2014
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Leong Siew Yoong and Chuah Choon Chieh
Universiti Tunku Abdul Rahman, Jalan Bandar Barat, 31900 Kampar, Perak, Malaysia
Corresponding Author: Leong Siew Yoong, Universiti Tunku Abdul Rahman, Jalan Bandar Barat, 31900 Kampar, Perak, Malaysia
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|Author:||Yoong, Leong Siew; Chieh, Chuah Choon|
|Publication:||Advances in Environmental Biology|
|Date:||Nov 1, 2014|
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