Production of biodiesel from dairy waste scum using eggshell waste

Production of biodiesel from dairy waste scum using eggshell waste

Process Safety and Environmental Protection 125 (2019) 279–287 Contents lists available at ScienceDirect Process Safety and Environmental Protection...

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Process Safety and Environmental Protection 125 (2019) 279–287

Contents lists available at ScienceDirect

Process Safety and Environmental Protection journal homepage: www.elsevier.com/locate/psep

Production of biodiesel from dairy waste scum using eggshell waste V. Kavitha a,∗ , V. Geetha b , P. Jennita Jacqueline b a b

Department of Chemistry, Sathyabama Institute of Science and Technology, Chennai, 119, Tamil Nadu, India Department of Chemical Engineering, Sathyabama Institute of Science and Technology, Chennai, 119, Tamil Nadu, India

a r t i c l e

i n f o

Article history: Received 26 December 2018 Received in revised form 3 March 2019 Accepted 18 March 2019 Available online 21 March 2019 Keywords: Dairy waste scum Eggshell Transesterification Engine performance Exhaust gas

a b s t r a c t An effluent from the dairy industry, waste scum oil containing triglycerides of fatty acids from C4 - C18 was selected as a potential feedstock for biodiesel production in the presence of nano calcium oxide obtained from modified eggshell. The eggshell waste was calcined at 800 ◦ C to facile synthesize nano calcium oxide and was characterized by X-ray diffractometer (XRD), Fourier Transform Infrared spectrometer (FTIR) and Scanning Electron Microscope (SEM). The calcined eggshell contains mainly nano calcium oxide (CaO) in calcite form with the crystallite size ranging from 16 to 22 nm. The transesterification reaction was carried out in a batch reactor and the operating parameters like catalyst loading, the molar ratio of methanol: oil, reaction temperature and time were optimized. Maximum biodiesel yield of 96% was obtained at the molar ratio of methanol: oil of 6:1, catalyst amount of 2.4 wt% and the reaction temperature of 65 ◦ C for 3 h. The quality of biodiesel produced by transesterification of dairy waste scum was tested on variable four-stroke compressible diesel engine and found to be comparable with conventional diesel in brake thermal efficiency and specific fuel consumption. The biodiesel produced possessed high cetane number and low NOx, than conventional diesel. The results proved that nano CaO obtained from eggshell can be effectively reused and recycled as a heterogeneous catalyst for biodiesel production. © 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

1. Introduction Public awareness on environmental pollution and everincreasing demand for energy have led to a constant search for non-toxic, efficient, renewable fuels for over a decade (Hoekman and Robbins, 2012). Among several renewable fuels, biodiesel is regarded as a potential alternative energy source for petroleumderived diesel in many countries (Lee et al., 2014) Biodiesel possesses properties which are comparable to petroleum diesel in its high flash point, improved cetane number, high viscosity and low carbon monoxide emission and sulphur content (Ferella et al., 2010). Biodiesel is mainly produced by transesterification of triglycerides with monohydric alcohols like methanol, ethanol, propanol in the presence of the catalyst. In the past decade, a potential feedstock, edible vegetable oil such as palm oil, sunflower oil, rapeseed oil, cottonseed oil, soyabean is used for the production of biodiesel (Pinto et al., 2005). However, these feedstocks have increased the global oil prices dramatically which leads to nonavailability of feedstock and food crisis (Mansir et al., 2017). Hence, in recent years, a paradigm shift have resulted in the usage of non-

∗ Corresponding author. E-mail address: [email protected] (V. Kavitha).

edible oil such as waste cooking oil, jatropha oil, animal fats, waste grease and microalgae (Leung et al., 2010) as feedstock in biodiesel production. These feedstock contain high water content and high free fatty acids (FFA) content which requires either a pretreatment or an esterification process. Another important aspect in transesterification process, is the proper choice of the catalyst which determines the cost of production in some cases leads to economic impediment. Most of these feedstocks utilizes either NaOH, KOH as their homogeneous base catalyst for transesterification process due to their high catalytic activity under mild conditions. In spite of these advantages, these catalyst suffers severe limitations as they are corrosive to reactors and requires a large amount of water for purification of biodiesel which ultimately escalates the cost of production (Georgogianni et al., 2009). In order to overcome these difficulties, the heterogeneous solid catalyst have gained a lot of importance due to high conversion efficiency and also for the reuse of the catalyst. Numerous heterogeneous solid catalyst are used for transesterification of vegetable oil which includes, alkali earth metal oxides and hydroxides(Granados et al., 2007; Liu et al., 2008), alumina supported salts(MacLeod et al., 2008; Xie and Li, 2006), zeolites (Xie et al., 2006) etc. Among different solid catalyst, calcium oxide (CaO) is best suited for transesterification reaction due to its low production cost and high basicity (Boro et al., 2012). Most of the transesterification reaction have focused on exploiting the

https://doi.org/10.1016/j.psep.2019.03.021 0957-5820/© 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

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potentiality of CaO from commercial calcium source as a catalyst for the biodiesel production. Apart from these commercial sources of CaO, several researchers have used CaO derived from eggshell for transesterification of oil (Shan et al., 2016), palm oil (Khemthong et al., 2012) jatropha curcas oil (Chavan et al., 2015) soyabean oil (Wei et al., 2009), Nahor oil (Boro et al., 2014), karanja oil (Sharma et al., 2010). The eggshell waste is considered as a valuable source of CaO since it is generated in large quantities and considered as a waste from restaurant and hotels, contributing to solid waste disposal issues. Hence, these two parameters namely non- edible feed stock and low cost catalyst plays an important role in the economics of biodiesel production by transesterification process. Therefore, it is highly desirable to select a non-edible feedstock with low FFA like dairy waste scum, an industrial waste for the biodiesel production by transesterification process using eggshell waste. Dairy waste scum is generated by dairy industries which handle raw and chilled milk and milk products like butter, ghee, cheese, yoghurt, ice creams etc., A large dairy, which processes 5 lakh litre of milk per day generates 250–300 kg of effluent scum per day, which makes it difficult to dispose (Holland and Redfern, 1997). Dairy scum is a less dense, floating solid mass formed by the mixture of fats, lipids, proteins etc., which creates difficulties in handling and operations in effluent treatment plants. Since these scum materials contains a large amount of triglycerides and is therefore selected as a feedstock in the present study. The main objective of the present study is to provide an economically feasible and viable technology to produce biodiesel at low cost using waste materials as feedstock and catalyst. The efficacy of the CaO derived from eggshell is studied towards the transesterification of dairy scum. The effect of reaction parameters like catalyst loading, temperature, reaction time and methanol amount on the yield of fatty acids methyl esters (FAME) was assessed. The physicochemical characteristics of the produced biodiesel were determined and the performance of the scum biodiesel along with its emission characteristics were compared with conventional diesel. Thus, utilization of CaO as a heterogeneous catalyst from eggshell waste in the conversion of dairy waste scum to biodiesel, can improve sustainability through the generation of value-added product. 2. Materials and methods

Table 1 Physical and Chemical properties of Scum oil. Properties

Value

Kinematic Viscosity at 40 ◦ C (mm2 /s) Flash and Fire point (◦ C) Cloud and Pour point (◦ C) Palmitic acid* (16:0) in % Stearic acid* (18:0) in % Oleic acid* (18:1) in % Myristic acid* (14:0) in %

13.52 270 and 290 17 and 38 42.13 12.76 18.20 14.35

* The number included in the parentheses represents the number of carbon atoms followed by number of double bonds.

Table 2 Variable compression engine specifications. Engine Specification

Research Diesel engine

Model Stroke Cylinder Maximum speed Power Compression Ratio

Kirloskar TV1 IC engine 4 stroke 1 1500 rpm 3.4kW Variable (17.5)

prepared catalyst contains mainly CaO and was stored in air-tight container for subsequent use and characterization. 2.3. Transesterification The reaction was carried out in a 1 L 3-necked round-bottom flask fitted with a water condenser. The thermometer was inserted into the flask using a rubber cork. The flask was heated by a temperature controlled heater. The reactor was charged with a known volume of scum oil. A known weight of the catalyst along with methanol was fed into the reactor and refluxed at 65 ◦ C for 3 h. The reactor was cooled and the products were allowed to stand for 2 h in a separating funnel which leads to the formation of 3 layers. The lower layer contains the solid catalyst while the middle layer contains glycerol and some unreacted triglycerides. The upper layer contains FAME or biodiesel. The FAME was removed and analyzed. 2.4. Catalyst characterization

The dairy waste scum was heated to 110 ◦ C until it becomes anhydrous. It is then filtered through a stainless steel mesh to remove any suspended impurities. Approximately, 1000 g of dairy waste scum yield 600–650 g scum oil which was characterized in Table 1 and used for further transesterification reaction.

The surface functional groups present in both calcined and uncalcined eggshell were examined by Fourier Transform InfraRed spectroscopy (FTIR; Shimadzu IR affinity-1S Japan) by varying the wave number from 4000 to 500 cm−1 using KBr technique. The crystalline phase and crystallite range in both samples (calcined and uncalcined eggshell) were identified using Bruker D8 advanced Powder X-ray Diffractometer (PXRD) equipment fitted with Goniometer detector by scanning the angle (␪) from 10 to 70◦ . The lattice parameters for the samples were estimated using Unitcell software for powder diffraction data (Sivakumar et al., 2011). The crystallite size in both samples were determined by DebyeScherrer equation using XRD data. Scanning Electron Microscope (SEM) images of the samples were observed in a TESCAN-VEGA 3 SBU (20 KV/30KV) with magnification from 1000 to 25,000×. The samples were ultrasonicated with acetone and coated with an SEM conductive carbon tapes for analysis.

2.2. Catalyst preparation

2.5. Analytical methods for biodiesel

The collected egg shells were cleaned with tap water and washed with lukewarm water to remove the thin membrane. The eggshells were sundried for 2 days, ground and are thermally calcined in a muffle furnace at 800 ◦ C for 3 h. During calcination, the calcium carbonate present in eggshell was converted to CaO. The

The specific gravity of dairy scum oil and FAME sample were determined using specific gravity bottle. The kinematic viscosity of dairy scum and FAME were determined by Reedwood Viscometer while the Flash point and Fire point for both the samples were determined by using Penskey-Martin closed cup apparatus. The

Dairy Scum was chosen as the feedstock for the present study and was collected from butter effluent section in Aavin dairy industry, Chennai. Analytical grade Methanol (99.5% purity) was obtained from Fischer chemicals and was used for the reaction without any further purification. Nano CaO prepared from waste eggshell was used in the present study. The waste eggshells were collected from a local restaurant in Chennai. 2.1. Scum oil preparation

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Fig. 2. FTIR patterns for eggshell waste a) Uncalcined b) Calcined at 800 ◦ C. Fig. 1. XRD pattern for eggshell waste a) Uncalcined b) Calcined at 800 ◦ C.

2.7. Calculation The percentage yield of biodiesel was obtained by using the equation, cloud point and pour point for the samples were determined using standard pour point apparatus. The composition of FAME was carried out in Agilent GC–MS 5973 equipped with FID using capillary column DB-5MS. The analysis was carried out in temperature programming mode from 50 ◦ C to 300 ◦ C at a rate of 10 ◦ C/min in a splitless injection mode. The glycerol content in FAME was analyzed by Agilent 6890 GC with FID using STABILWAX from 40 ◦ C to 250 ◦ C by temperature programming mode.

2.6. Engine performance The performance of biodiesel on the mechanical properties was studied using variable compression engine specified in Table 2. The emission characteristics of biodiesel were analyzed by diverting the exhaust to AVL gas analyzer at 1500 rpm.

FAMEYield(%) = (Amountofbiodiesel/Weightofscumoil)X100.

3. Results and discussion 3.1. Catalyst characterization The XRD pattern of uncalcined and calcined eggshell catalyst is illustrated in Fig. 1. The uncalcined sample showed diffraction peaks at 2␪ of 29.4◦ , 39.8◦ , 43.56◦ and 47.99◦ indicating the characteristic peaks of calcium carbonate (CaCO3 ) corresponding to JCPDS file no. 05-0586, belonging to calcite. In the calcined sample, the reflection peaks were observed at 2␪ of 18.10◦ , 34.17◦ , 47.16◦ , 50.84◦ and 54.40◦ which corresponds to crystalline phase for Ca(OH)2 (JCPDS file no. 72-0156) which is similar to work by Wijaya Suryaputra et al. (Suryaputra et al. (2013)) The crys-

Table 3 Crystal system, Crystallite size and lattice parameters for calcined and uncalcined egg shell. Sample

Crystal system

Crystallite size

Uncalcined

Rhombohedral

55 nm

Calcined

Hexagonal

16-22nm

Lattice parameters a 4.927Å c 16.90Å a 3.590Å c 4.901Å

JCPDS Volume 355.22 Å3 Volume 54.68 Å3

05-0586 72-0156

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Fig. 3. SEM patterns for eggshell waste A & B- Uncalcined at 1.0 and 5 K x with 20 KV ; C& D - Calcined at 2.5 and 5 Kx with 30 KV.

tal system, crystallite size and lattice parameters for calcined and uncalcined sample is presented in Table 3. FTIR spectra of the uncalcined and calcined eggshell are presented in Fig. 2. In uncalcined samples, a well defined infrared bands at 1427, 860 and 750 cm−1 is witnessed, represents the characteristic asymmetric stretching, out-of-plane bending and in-plane bending modes of carbonate groups in CaCO3 which are in accordance with the results obtained for other CaCO3 containing waste shells(Boro et al., 2011). In the calcined sample, a narrow absorption band at 3634 and 500 cm−1 are due to stretching mode of OH groups in Ca(OH)2 samples(Garcia et al., 2005). The absorption bands at 868, 1059 and 1410 cm−1 are assigned to different vibration modes of C O bond in CO3 2- , due to the presence of residual CaCO3 in the calcined sample. Fig. 3 represents the SEM image of the uncalcined and calcined eggshell at 1.0 and 5.0 Kx magnification. The uncalcined eggshell indicates the presence of dispersed particles at 1.0 Kx and 5.0 Kx. The calcined eggshell (prepared by heating eggshell at 800 ◦ C) shows a rock like monolith particles at 2.5 Kx while at 5.0 Kx it exhibits a porous structure. 3.2. Transesterification reaction Scum oil was transesterified by refluxing with methanol using NaOH, calcined and uncalcined eggshell to understand their cat-

alytic behaviour. The uncalcined eggshell has no effect (as a catalyst) on transesterification reaction as it contains only calcium carbonate in calcite phase. The yield of FAME was less in homogeneous catalyst, NaOH compared to calcined eggshell. The nano calcium oxide in calcined eggshell increases the surface area of the catalyst thereby increase the yield of FAME. Reddy et al. (Reddy et al., 2006) also experienced the high catalytic activity of nanocrystalline CaO during the transesterification of soyabean oil fat as compared to KOH. Hence, further investigation on the effect of operating parameters like catalyst loading, reaction temperature, time, the molar ratio of methanol: oil was studied using calcined eggshell containing nano CaO. 3.3. Optimization for transesterification reaction 3.3.1. Catalyst loading The effect of calcined eggshell containing nano calcium oxide catalyst on FAME yield is shown in Fig. 4a by varying the catalyst from 0.8 to 3.2 wt %. As the catalyst concentration was increased from 0.8 to 1.6 wt%, the yield also increased. Increase in catalyst concentration increases the surface area for methanol to adsorb resulting in increased FAME yield. The optimum concentration was achieved at 2.4 wt % which resulted in 90% FAME yield. Further increased in catalyst amount to 3.2% the yield was reduced drastically to 10% due to the formation of calcium soaps which prevents

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Fig. 4. Effect of operating parameters (A-Temperature; B-Time; C-Catalyst; D-Molar ratio) on transesterification of scum oil.[Experimetal Conditions: A- Scum oil -250 mL, methanol: Oil- 4:1, Catalyst - 1% (wt), Time-2h; B- Same as A Temperature 65◦ C; C- Same as A, Temperature- 65◦ C and Time-3h; D- Same as A, catalyst- 2.4% (wt) Temperature65◦ C and Time-3h].

ester layer separation as these findings were in accordance with results obtained by Saqib et al. (Saqib et al. (2012)). 3.3.2. Reaction temperature Increase in temperature also increase the yield of biodiesel. The effect of temperature on the FAME yield is shown in Fig. 4b. As the temperature is increased from 50 ◦ C to 60 ◦ C, the FAME yield also increased. Maximum yield of 78% is obtained at a temperature of 65 ◦ C A further increase to 70 ◦ C leads to the marginal decrease in the yield due to the enhancement of both transesterification and saponification reaction. (Phan and Phan, 2008). Hence, the optimum temperature of 65 ◦ C was maintained during the course of the reaction. 3.3.3. Reaction time The effect of time on the FAME yield is studied by varying the time from 60 min to 240 min and maintaining the temperature at 65 ◦ C at a molar ratio of 4:1 is represented in Fig. 4c. Increase in reaction time increases the yield up to 180 min as the contact time between the reactants increased. Further increase in reaction time decreases the yield as the backward reaction predominate together with saponification reaction since transesterification is a reversible reaction (Eevera et al., 2009). Hence, the optimum time of 180 min was selected for further studies.

3.3.4. Alcohol: oil molar ratio The molar ratio of alcohol to oil determines the efficiency of the transesterification reaction. Theoretically, 3 mol of alcohol is required for each mole of oil. In order to drive the reaction to completion, a molar ratio in excess of the theoretical stoichiometric ratio is added (Demirbas, 2010). The effect of molar ratio on FAME yield is represented in Fig. 4d by maintaining the temperature at 65 ◦ C for 3 h at a catalyst loading of 2.4 (wt %). The maximum yield was achieved at the molar ratio of 6:1. Increase in the molar ratio from 3.5 to 6.0 increased the FAME yield as calcium methoxide species formed on the surface CaO catalyst enhances the reaction between the scum oil and methanol. The calcium methoxide species favors the forward reaction up to 6.0:1 while further increase in the molar ratio to 6.5 did not promote the reaction. The decrement in the FAME yield observed at high methanol content (above the optimum ratio) results in a backward reaction between the methyl ester product and glycerol forming monoglycerides and diglycerides. High methanol concentration also hinders the separation of the ester from the glycerol together with the appearance of foamy phase (Freedman et al., 1984). Hence, an optimum molar ratio of 6:1 is used in transesterification reaction of scum oil and catalyst which is similar to the results obtained during transesterification of sunflower oil using CaO by Veljkovic´ et al. (Veljkovic´ et al. (2009))

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Table 4 Regeneration and Reusability of catalyst. Number of cycle

FAME Yield (%)

Fresh II cycle III cycle IV cycle

96 76 53 24

Fig. 5. Possible mechanism for transesterification of scum oil using calcined eggshell (catalyst).

3.4. Reusability of catalyst The reusability and stability of calcined eggshell were studied by using the catalyst for 4 cycles of transesterification reaction. The reaction cycles were operated at optimum conditions of the molar ratio of methanol: oil -6:1; catalyst amount of 2.4%; reaction time and temperature at 3 h and 65 ◦ C respectively. Maximum FAME yield of 96% was obtained with fresh catalyst. The catalyst is separated from the reaction products and washed repeatedly with distilled water followed by drying at 105 ◦ C for 6 h. As shown in Table 4, the FAME yield decreases in subsequent cycles due to deactivation of basic sites of the catalyst. Wijaya Suryaputra et al. (Suryaputra et al. (2013)) also experienced a decrease in FAME yield during reusability of waste capiz shell for transesterification reaction of palm oil which is consistent with our results reported. The yield of FAME decreased to 24% in the fourth cycle. Even though low FAME yield was achieved in these experiments, it opens the new possibility of effectively separating and recycling of the catalyst.

of the oil to form tetrahedral intermediate. (Boro et al., 2011) The intermediate species is attacked by proton from CaO with simultaneous rearrangement of tetrahedral species to produce biodiesel or fatty acids methyl ester (FAME) and glycerol. 3.6. Characteristics of biodiesel The chemical composition of the biodiesel obtained by transesterification of dairy scum oil using calcined eggshell is presented in Fig. 6. The Gas Chromatogram shows the FAME present in biodiesel were Methyl palmitate, Methyl oleate and Methyl myristate in 35%, 19%, and 12.5% respectively. The other methyl esters identified were stearate, laurate and caprate in low percentage. The FAME produced by this method contains a large amount of saturated esters. The glycerol content in the biodiesel was found to be negligible. The physical characteristics of biodiesel are compared with conventional diesel along with Indian standards (IS) for biodiesel and presented in Tables 5 and 6 . The kinematic viscosity plays an important role in fuel atomization and injector performance (Soetaredjo et al., 2011). When the viscosity of the fuel is too high or too low, it affects the fuel performance by causing poor combustion. The kinematic viscosity of biodiesel is 4.16 ± 0.2 which are within the Indian Standards(IS) for biodiesel. The Flash and Fire point is another significant parameter responsible for ignition of the fuel (Wardle, 2008). The Flash and Fire point of biodiesel was 130◦ and 140 ◦ C respectively which is slightly higher than the IS indicating the safer handling and storage of the fuel. The cetane number plays a crucial role in the combustion of the fuel. The fuel with low cetane number produces noise and smoky exhaust gas together with difficulty in starting the engine. Hence, high cetane number fuel is preferred. The cetane number of biodiesel is 56.06 which higher than the range specified by IS since the major constituents in scum biodiesel are methyl palmitate, methyl oleate and methyl myristate whose cetane number are 59.3, 85.9 and 66.2 respectively (Rashid et al., 2011). The cloud and pour point for the scum biodiesel were 10 ◦ C and 17 ◦ C which is less suitable for cold conditions. High value in the cloud and pour point compared to IS standards for biodiesel may be attributed to a large percentage of saturated fatty acids methyl esters (Holland and Redfern, 1997). Leaching of calcium from catalyst to the reaction medium was estimated by collecting the produced biodiesel samples. The presence of calcium in biodiesel affects the quality, quantity of biodiesel and also the reusability of the catalyst. The concentration of leached calcium is inversely related to the catalyst reusability. The concentration of calcium in biodiesel and in glycerol phase was found to be 15.9 ppm and 43.1 ppm respectively. High concentration of leached calcium species was observed in glycerol phase compared to biodiesel phase is due to the formation of calcium glyceride since calcium is more soluble in glycerol than in biodiesel. Yoosuk et al. (Yoosuk et al. (2010)) also revealed the amount of calcium (neat CaO) in the biodiesel phase was 0.456 mg CaO/ml and in glycerol phase was equivalent to 0.975 mgCaO/ml. Low concentration of calcium in biodiesel was exhibited during the experimental study which is less than the IS for biodiesel (5 mg/kg).

3.5. Mechanism The possible mechanistic aspect of transesterification reaction in the presence of calcined eggshell is depicted in Fig. 5. The calcined eggshell contained mainly calcium oxide (CaO), act as a catalyst in transesterification reaction by abstracting the protons from the reacting media onto the surface of the solid catalyst. The abstraction of proton on to CaO takes place either from methanol or from water to form highly basic and active methoxide anion(I). The methoxide anion being a strong nucleophile attacks the carbonyl carbon atom

3.7. Performance test on compressible engine using biodiesel and diesel The performance test on variable compression diesel engine is performed by studying the brake thermal efficiency, specific fuel consumption along with emission characteristics. Brake thermal efficiency is defined as the ratio of brake power energy to the input fuel energy. The brake thermal efficiency of biodiesel and diesel at varying loads is plotted and presented in Fig. 7. In both diesel

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Fig. 6. Gas chromatographic analysis of biodiesel showing fatty acids methyl ester (FAME) content.

Table 5 Composition of FAME (Fatty Acids Methyl ester) from Scum oil. Structural Name and Molecular Formula

Systematic Name

Linear Formula

Composition (wt%)

Methyl myristate (C15 H30 O2 ) Methyl Palmitate (C17 H34 O2) Methyl Palmitoleate (C17 H32 O2 ) Methyl stearate (C19 H38 O2 ) Methyl Oleate (C19 H36 O2 ) Methyl Linoleate (C19 H34 O2 )

Tetradecanoic acid Hexadecanoic acid Cis-9-hexadecanoic acid Octadecanoic acid Cis-9-octadecanoic acid Cis 912 octadecenoic acid

CH3 (CH2 )12 COOCH3 CH3 (CH2 )14 COOCH3 CH3 (CH2 )5 CH = CH(CH2 )7 COOCH3 CH3 (CH2 )16 COOCH3 CH3 (CH2 )7 CH = CH(CH2 )7 COOCH3 CH3 (CH2 )3 (CH2 CH = CH)2 (CH2 )7 COOCH3

1.29 35.81 2.94 10.89 19.05 1.14

Table 6 Comparison of physical properties of biodiesel, diesel and IS(biodiesel). Physical Properties ◦

2

Kinematic Viscosity at 40 C (mm /s) Specific Gravity Flash and Fire point (◦ C) Cloud and Pour point (◦ C) Cetane number Glycerol content

Biodiesel

Diesel

IS (biodiesel)

4.16 0.83 130 & 140 10 & 17 56.01 negligible

2.54 0.82 54 &60 −15 to 5 & 5 45-55 nil

1.9-6.0 0.87-0.90 100 &130 −3 to 12 & -15 to 10 47-55 nil

and biodiesel, the brake thermal efficiency increases with increase in load. At a lower load of 3.2 kg, both diesel and biodiesel have same efficiency. At full load of 12 kg, the brake thermal efficiency of biodiesel is 9% less that of diesel which may be due to low combustion rate as seen by high kinematic viscosity of biodiesel compared to diesel. Specific fuel consumption (SFC) is defined as the amount

of fuel consumed for each unit of break power developed per hour. Fig. 7 represents the SFC for diesel and biodiesel at varying loads. The fuel consumption decreases with increase in the load for both diesel and biodiesel. At 100% load, the SFC value for diesel and biodiesel are almost same suggesting the biodiesel is combusted as effectively as diesel.

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Conflict of interest The authors report no conflicts of interest. The authors alone are responsible for the content and writing of this article. References

Fig. 7. Performance characteristics of biodiesel and diesel at varying loads.

Fig. 8. Emission Characteristics of NOx, HC and CO for biodiesel and diesel at varying brake power.

The emission studies for nitrogen oxides (NOx), carbon monoxide (CO) and hydrocarbons (HCS) for biodiesel and diesel were compared and are given in Fig. 8. The NOx emissions are low in biodiesel compared to diesel which is highly desirable at low brake power while the HCS and CO emissions are high compared to diesel (Sodhi et al., 2017) which strongly indicating the incomplete combustion of CO and HCS due to lack of oxygen or due to low gas temperature. The exhaust gas temperature of biodiesel is very low which confirms the low temperature existing in the engine were the main cause for incomplete combustion of CO and HCS. 4. Conclusions The proposed study paved a new way to convert the potential waste materials namely dairy scum waste and eggshell waste to biodiesel. The eggshell waste was calcined to 800 ◦ C for 3 h to form catalyst-containing mainly nano calcium oxide. Maximum yield of 96% biodiesel was obtained by transesterification of scum oil with methanol at 65 ◦ C for 3 h at a molar ratio of 6:1 (methanol: oil). The produced biodiesel have high concentration of saturated fatty acid methyl ester (methyl palmitate) and its engine performance are comparable with diesel. The NOx emissions of the produced biodiesel was less than the conventional diesel at low brake power. Further work on blending the biodiesel with conventional diesel can enhances its performance and better used as an alternative fuel to petroleum diesel.

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