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Article

Optimized Biodiesel Production from Pumpkin (Cucurbita pepo L.) Seed Oil: A Response Surface Methodology for Microwave-Assisted Transesterification

by
Mehmet Recai Durgut
Biosystems Engineering Department, Agricultural Faculty, Tekirdag Namik Kemal University, Tekirdag 59030, Türkiye
Processes 2025, 13(2), 572; https://doi.org/10.3390/pr13020572
Submission received: 12 January 2025 / Revised: 13 February 2025 / Accepted: 15 February 2025 / Published: 18 February 2025
(This article belongs to the Special Issue Experimental Investigation and Modeling of Biowaste Conversion into Renewable Energy and Resources)
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Abstract

:
The acceptance of biodiesel, specifically fatty acid methyl esters, as an alternative to petroleum diesel has increased significantly. Traditional feedstocks used to produce biodiesel include various seed oils and used frying oils, but there is growing interest in low-cost alternatives like pumpkin seed oil. As a byproduct of cucurbits processing, a significant number of seeds often remains with a high oil content suitable for biodiesel production. In the search for new low-cost alternative feedstocks for biodiesel production, the evaluation of pumpkin seed oil was emphasized. Using a modified microwave oven for transesterification, this study optimized the key parameters of reaction temperature, catalyst concentration (KOH), and reaction time using a Box–Behnken design. The results showed a maximum biodiesel yield of 91.5%. Microwave irradiation significantly accelerated the process, reducing reaction times from an hour to minutes. The biodiesel produced met international physicochemical standards, demonstrating the potential of pumpkin seed oil as a sustainable biodiesel source.

1. Introduction

Elevated energy consumption and climate change, propelled by greenhouse gas emissions, pose significant challenges to achieving global sustainability goals. The potential of liquid biofuels to lessen the various environmental stressors brought on by the usage of fossil fuels is making them a more attractive alternative to gasoline and diesel as energy sources. Numerous studies show that bioethanol, biogas, and biodiesel are better fossil fuel alternatives. Because biodiesel and diesel share comparable fuel characteristics, they are well-suited as diesel fuel alternatives, either alone or in combination with petroleum diesel [1]. Biodiesel (fatty acid methyl ester) has been a competitive fossil fuel substitute for decades due to its similar qualities to petrol and diesel. The advantages of biodiesel over petrol and diesel are many. Characteristics include a low viscosity, strong lubricity, elevated flash point, non-toxicity, high cetane number, and biodegradability. This fuel produces lower CO2 emissions compared to petrol and diesel, and has a high efficiency of combustion and minimal ignition delay time with extended engine life [2].
Biodiesel comprises mono-alkyl esters of fatty acids derived from vegetable oils, dis-carded animal fats, and cooking oils. The predominant method for commercial biodiesel production involves a transesterification reaction between triglycerides and mono-alkyl alcohols, aided by homogeneous basic or acid catalysts. The selection of fat or oil for biodiesel manufacturing entails both chemical and economic considerations. In terms of process chemistry, the primary distinction among the various fats and oils is the concentration of free fatty acids (FFAs) linked to triglycerides. The iodine value is a significant factor influencing the selection of oil. The difficulties related to utilizing agriculture land for fuel production, together with its competition with food production, have rendered the use of first-generation feedstocks, such as corn, increasingly contentious. Furthermore, in order to achieve the climate objectives set forth by the European Commission, which seeks a significant reduction in net greenhouse gas levels by 2030, it is crucial to diversify and improve renewable energy sources [3]. There is a necessity for novel, low-cost oilseed crops to generate cost-effective oils appropriate for biodiesel manufacturing. Investigation into alternative biofuel raw materials like hemp (Cannabis sativa) and the Cucurbitaceae family shows their potential for sustainable energy production [3]. One potential alternative oil crop for the Mediterranean region is pumpkin seed. In the quest for alternative oils for biodiesel production, pumpkin seed oil has emerged as a promising option [4].
Cucurbits as biofuel raw material possess high biomass content and contain oils appropriate for biodiesel production, offering a renewable and potentially sustainable energy source. Furthermore, they frequently flourish in many climates and necessitate minimum inputs, rendering them an appealing choice for biofuel production [3].
Cucurbits, belonging to the Cucurbitaceae family, include over 960 species with diverse characteristics. Their fruits are used in various culinary applications, while the seeds, often considered waste during processing, have high oil content suitable for food and biofuel production. Seed yields vary by species, with Cucurbita pepo var. 2.63–6.80%, Cucurbita pepo 3.20–8.44%, Cucurbita moschata 2.73–3.19%, and Cucurbita maxima yielding 2.04–10.71%. Overall, seeds make up about 10% of the fruit mass, with yields ranging from 400 to 1686 kg ha−1, highlighting their potential as a valuable resource for promoting an environmentally friendly future [3].
The composition of pumpkin seed oil, which is typically rich in unsaturated fatty acids, makes it a suitable feedstock for biodiesel production [5]. The potential of Cucurbita pepo seed oil for biodiesel production was examined previously. The biofuel properties of the methyl esters of the seed oil were examined in [6], while [4] explored the FAME of the oil as a potential alternative diesel fuel in Greece. Both studies concluded that the oil is an effective feedstock for biodiesel production.
Biodiesel has numerous advantages over petrol fuels. Compared to diesel, it is non-toxic, biodegradable, and exhibits a more advantageous combustion emission profile, including reduced emissions of carbon monoxide, particulate matter, and unburned hydrocarbons. The transesterification reaction in biodiesel manufacturing is conducted by utilizing several heating systems. In all traditional heating methods, heat is conveyed to the walls of the reaction chamber and subsequently to the reaction medium. This process is somewhat sluggish. During microwave heating, materials within the reaction medium absorb microwave radiation under specific conditions, resulting in internal warming that propagates outward across the system. This heating is inversely correlated with transport convection, facilitating the system’s heating from the exterior to the interior [7]. If microwave radiation is uniformly distributed in the reaction media and the reactants are considered to be well mixed, there is no temperature variation in the absence of microwave heating. Consequently, undesirable side reactions are minimized and are preferable to traditional heating systems where the heat source is not in direct contact with the reaction mixture. In microwave heating reactions, the reactor wall is at a lower temperature than the reaction mixture [8].
Rapid heating refers to the process by which a catalyst or any chemical absorbs mi-crowave energy, irrespective of its low thermal conductivity. Microwave heating accelerates the reaction rate due to the absence of low heat transfer characteristic of conventional heating methods. Volumetric heating refers to the process of uniformly heating the whole volume of a sample in a microwave oven, originating from the center, in contrast to traditional heating, which heats from the reaction medium towards the center. Consequently, the sample is subjected to accelerated heating [9]. The reaction time is approximately 1 h with a conventional heating system, but it reduces to 3 to 7 min when a microwave heating system is utilized [10,11,12].
Microwave irradiation substantially facilitates the transesterification of pumpkin seed oil, enhancing reaction kinetics and improving overall conversion efficiency [1]. Microwave heating is an exceptionally effective technique that can selectively heat reactants, hence minimizing energy usage and reaction duration relative to other heating methods [13,14]. The transesterification process for producing the desired biodiesel may utilize a basic catalyst such as sodium hydroxide or potassium hydroxide. Prior research showed that several reaction parameters, including temperature, molar ratio of alcohol to oil, and catalyst concentration, substantially affect the efficiency of the microwave-assisted transesterification process [1].
Production optimization is a significant topic, as it enhances the biodiesel yield and diminishes production expenses. The surface response technique is an empirical modeling methodology utilized for the development, enhancement, and optimization of complex systems. The surface response methodology is a favored technique for optimization across various scientific disciplines. The utilization of specially constructed experimental designs with this strategy decreases the number of experiments necessary for optimization, yielding economic benefit. Response surface methodology is a statistical technique utilized for optimizing transesterification parameters in biodiesel production. Numerous research studies adjusted process parameters for biodiesel production with response surface technique software [15].
In this study, the Box–Behnken design (BBD) is utilized. This design represents a specific type of design available in response surface methodology (RSM) and has been widely used for the optimization of biodiesel production. The BBD demonstrates superior prediction capabilities, shows advanced efficiency in parameter optimization, and requires fewer trials compared to alternative designs. The BBD offers improved efficiency in terms of the ratio of the total number of trials to the model coefficients compared to a central composite design (CCD) [16].
The novelty of this work is the production of biodiesel using microwave heating kinetics. The paper also aims to maximize the results and hence the model efficiency by using response surface methodology to explain the effects of multiple parameters and their interactions in the production of biodiesel from pumpkin seed oil. Furthermore, no paper has been reported on this topic in the last 10 years [2]. Moreover, the paper sheds light on how MW technology can be applied to biodiesel production.

2. Materials and Methods

2.1. Experimental Set-Up and Procedure

To perform the transesterification of pumpkin seed oil, specific processes were meticulously adhered to in order to guarantee optimal process output according to the established specifications.
Pumpkin seed oil was extracted from unrefined pumpkin seeds sourced from the market using the cold pressing method. Traditional cold-pressed extraction squeezes seed oil droplets with mechanical pressure. This process is cheap, fast, solvent-free, environmentally friendly, and produces high-quality oil at a lower temperature [3]. The cold press machine depicted in Figure 1 was utilized in this operation. The process parameters were 15 mm diameter outlet tip, screw rotation speed of 35 rpm, and constant outlet temperature of 50 °C. The extracted oils were allowed to rest for four hours to facilitate sedimentation, after which the oil was filtered and utilized in biodiesel trials.
A modified commercial MD574S Arçelik (Terkirdağ, Türkiye) household microwave oven was used for experiments. The oven has continuous power transfer and 700 W adjustable output. A small aperture was fashioned on the side of the oven for the installation of a type K thermocouple. This was integrated directly into the unprocessed material blend within the oven. A small aperture was fabricated at the base of the oven for the installation of a motorized stirrer. Reaction temperature was monitored and controlled by a REX-C100 digital controller. At the commencement of each experimental, the modified microwave oven was meticulously examined to confirm the absence of any leaks (shown in Figure 2) [17].
Experiments were conducted to ascertain the optimal reaction conditions for biodiesel production via microwave methodology, aiming to minimize the energy input in pumpkin seed oil biodiesel synthesis. The methanol-to-oil molar ratio was maintained at 6:1, while varying the reaction durations (3, 5, 7 min), catalyst concentration (KOH) (0.5%, 1.0%, 1.5%), and reaction temps (50 °C, 55 °C, 60 °C) were employed to evaluate their effects on transesterification yield [18].
The catalyst was first dissolved in alcohol and then added to the oil, enabling the reaction at the designated temperature and duration under reflux in the microwave equipment. Stirring was sustained at 600 rpm throughout the reaction [19]. After the reaction, the product was cooled to room temperature with an ice bath, centrifuged at 4000 rpm for 10 min, and the methyl ester and glycerin phases were then separated. The methyl ester was washed with distilled water to remove impurities from the phase and washing until pH reached 7. The excess water and methanol remaining after washing were removed using a rotary evaporator [10]. The drying process is crucial for controlling the moisture content in biodiesel to comply with ASTM D6751 or EN14214 standards. The ultimate biodiesel yield was measured after the completion of all purification operations. Equation (1) was employed to determine the fuel conversion or FAME yield efficiency (%Y) [20,21].
%Y = (Weight of biodiesel fuel)/(Weight of oil) × 100

2.2. Determination of Fuel Properties

The biodiesel’s flash point was determined to the ISO 3679 standard. The pour point measurements were conducted utilizing the ISO 3016 technique. The kinematic viscosity was measured using a viscometer in accordance with the ISO 3104 standard. The fuel density was ascertained utilizing the ISO 12185 technique. All experiments were conducted in triplicate, and the mean values are presented [17].

2.3. Box–Behnken Experimental Design

The parameters selected for optimizing the microwave irradiation-assisted alkaline-catalyzed transesterification process include temperature, KOH catalyst concentration, and duration of microwave irradiation, as detailed in Table 1. BBD, commonly used in RSM, optimizes processes and analyzes the effects of multiple variables on a response. With three levels of each factor (−1, 0, +1), it explores linear and quadratic effects efficiently. These levels typically represent low, medium, and high values of experimental factors.
Analysis of variance (ANOVA) was conducted to assess the significance of the model and all its terms within a 95% confidence interval.
Investigation and modeling the effect of variable parameters were performed using Design Expert 11 software (Demo version), RSM method, and Box–Behnken experimental design. In this study, factors such as time, catalyst-to-oil weight percentage, and temperature were investigated. The test matrix is presented in Table 2.

3. Results and Discussion

The effects of reaction time, catalyst amount, and reaction temperature on biodiesel production were determined using the Box–Behnken design (BBD). For the optimization of biodiesel production, three production parameters with three levels were used in the Box–Behnken design (BBD). Table 2 gives the production parameters and the levels of production parameters with the responses. The second-order equation of the biodiesel yield, which is the output parameter, according to the input factors is given below (Equation (2)). The maximum yield recorded was 91.5% (experimental) and 92.21% (predicted) under the experimental conditions of a 5 min reaction time, 0.5% KOH catalyst relative to oil weight, and a reaction temperature of 60 °C. The lowest yield was 68% (experimental) and 68.47% (predicted) under the experimental conditions of 3 min, 1% KOH, and 50 °C. Figure 3 illustrates the regression fit between the experimental and predicted yield outcomes from the RSM study for biodiesel production from pumpkin seed oil.
A good correlation and an adequate data fit are shown along the line of unit slope in Figure 3, which displays the expected data of the biodiesel production against the actual experimental data. The experimental values and good approximation of the expected response verify the model’s capacity to create a correlation between the process parameters and the production of biodiesel. The regression analysis resulted in an R-squared value of 0.9945, which indicates 99.45% (Table 3) influence of process variables on the biodiesel yield.
A comprehensive quadratic model was employed in the regression study to estimate the biodiesel yield. The comprehensive regression equation (coded) was formulated as shown in Equation (2).
Yield (%) = 84.32 + 3.75 × A − 4.3325 × B + 2.7825 × C − 0.2475 × AB − 2.8725 × AC + 1.7275 × BC − 2.08125 ×
A2 + 1.63875 × B2 − 4.36625 × C2
where A, B, and C represent the coded values {high (+1), medium (0), and low (−1)} of reaction temperature, catalyst concentration, and reaction time, respectively (given in Table 1). In the equation, the positive sign signifies an incremental effect, while the negative sign denotes a diminishing influence on the dependent variable (response).
Figure 4 illustrates the impact of each independent variable on the reaction yield individually. The figure illustrates that temperature variations (A) and reaction time (C) positively influence reaction efficiency; as these parameters increase, so does the reaction efficiency. Extending the reaction time from 3 to 5 min enhances the reaction yield. Nevertheless, an increase in the reaction time from 5 to 7 min resulted in a decline in reaction efficiency. The catalyst concentration curve (B) adversely affected reaction efficiency, and when these parameters increased, reaction efficiency diminished. This occurred because the reaction approached equilibrium, prompting the initiation of a reverse reaction. Extended duration diminishes production yield, attributable to the heightened likelihood of biodiesel hydrolysis in alkaline environments.
The analysis of variance presented in Table 4 indicates that the proposed regression model for calculating the reaction efficiency of methyl ester synthesis is significant at a 1% level. At the heart of ANOVA lies the F value, a statistic that serves as the cornerstone for determining whether the observed differences in group means are statistically significant or simply due to random variation. The value of F for the model equal to 139.37 indicates that the model is significant, and there is only 0.01% probability that the value of F is due to noise. Therefore, the parameters A, B, C, AC, and C2 were significant in this model. Also, the P-value greater than 0.1 indicates that this has no significant effect on the model. Fitting of experimental and predicted data for reaction efficiency to the regression model shows the determination coefficient of R2 is equal to 0.9945. The regression model accurately characterizes the experimental data, indicating a successful association of the three components of the transesterification/esterification process that influence biodiesel production [22].

3.1. Effect of Reaction Parameters on Biodiesel Yield

The interaction effects of the reaction parameters during the transesterification process were investigated using three-dimensional surface graphs. Figure 5a shows the influence of the catalyst quantity and reaction temperature on the biodiesel yield. Figure 5a illustrates that an increase in catalyst quantity leads to a reduction in biodiesel output, whereas a rise in reaction temperature corresponds to an enhancement in the biodiesel yield. The reaction temperature is a critical parameter in the transesterification process, as it influences the reaction rate and impacts biodiesel yields. The reaction temperature must remain below the boiling point of the alcohol to prevent its evaporation [22]. As the temperature increases, the methyl ester level similarly rises, peaking at 60 °C with a methyl ester percentage of 91.5%. This outcome aligns with the findings of other investigations [23,24].
Figure 5b illustrates the relationship between the reaction temperature and reaction time for the biodiesel yield. Figure 5b indicates that an increase in the reaction temperature and duration correlates with a rise in the biodiesel yield. Extending the reaction time from 3 to 5 min enhances the reaction yield. Nevertheless, an increase in the reaction time from 5 to 7 min resulted in a decline in the reaction efficiency. It is clear that an increase in the reaction time would not yield a further increase in the biodiesel yield obtained from pumpkin seed oil under the prevailing conditions of the reaction. This could be explained from the viewpoint of the reversible nature of the transesterification process as reported by [22]. Increasing the reaction time post-equilibrium of the reaction mixture will not increase the biodiesel yield; consequently, prolonging the reaction time may trigger reverse transesterification, thereby reducing the biodiesel yield [25].
Figure 5c demonstrates the importance of the reaction time and catalyst quantity on the biodiesel yield. Figure 5c demonstrates that, whereas the reaction yield markedly improves with an extended reaction time, a notable decline in the biodiesel output transpires with an increase in the catalyst quantity. The diminished yield of biodiesel results from the excessive inclusion of the alkali catalyst, which prompts a greater reaction of triglycerides with the catalyst, leading to increased soap formation [26,27]. This behavior can be ascribed to the formation of an emulsion at elevated catalyst concentrations, where the dissolved soap increases the solubility of methyl ester in glycerol, resulting in further yield loss [28,29]. Refs. [30,31,32] also found that an increase in the catalyst concentration resulted in a drop in yield.

3.2. Optimization and Model Validation (Esterification)

The esterification process was optimized to obtain the best process conditions that provide the maximum biodiesel yield. Through the numerical optimization functionality of Design-Expert® 11 Software, the optimal values for three variables were identified: reaction temperature (A), catalyst concentration (B), and reaction duration (C). The optimization of reaction variables was successfully achieved with the aid of RSM, which comprises three components and three levels of BBD [33]. The separation of the esterified pumpkin seed oil blend from the byproducts is shown in Figure 6. The optimum values were obtained at a reaction temperature of 58 °C, a time of 4 min, and a KOH dosage of 0.5 wt.% with a predicted maximum yield of 91.52%. The model prediction was validated by conducting the experiment in three repetitions utilizing the expected values. The average experimental yield of 91.7 was obtained. The fuel attributes of the biodiesel sample acquired under these conditions were assessed and compared with the studies (Table 5). Microwave irradiation greatly reduced the reaction time for maximum yield.
Despite its benefits, microwave heating has drawbacks that need further study. This technology must be made more popular by solving large-scale production, catalyst usage, and cost-effectiveness issues. Additionally, life-cycle assessment, techno-economic evaluation, and circular economy studies are needed to increase fuel quality and reduce waste. Future biodiesel production may rely on microwave technology to reduce waste and provide eco-friendly gasoline [3].
Density quantifies the fluidity of biodiesel. Density is anticipated to range from 860 to 900 kg/m3. The density of pumpkin seed oil biodiesel was found to be 884 kg m−3. This value lies between the target values. Viscosity is a critical property of biodiesel. High-viscosity fuel results in inadequate atomization, inefficient combustion, injector obstruction, and carbon accumulation in the segments. The viscosity of biodiesel should range from 3.5 to 6 mm2/s. The viscosity value was found to be 4.17 mm2/s. This value lies between the target values. The flow and cloud points refer to the temperature at which crystal clouds first become visible as the liquid is cooled under specified conditions. The cloud point is a crucial determinant of diesel fuel performance at low temperatures. This poses challenges for the utilization of fuels at extremely low temperatures. The cloud point of biodiesel is contingent upon the characteristics of the oil raw material. For instance, according to ASTM D2500 standards, the cloud point of biodiesel derived from rapeseed oil is −3 °C, while that of food-grade frost oil is 19 °C [17,34]. This study found that biodiesel derived from pumpkin seed oil exhibited a flow point of −1 °C and a cloud point of 3 °C.

4. Conclusions

This study examined the optimization of biodiesel synthesis from pumpkin seed oil using microwave-assisted transesterification and a response surface approach. The research sought to determine the ideal process parameters for enhancing the biodiesel yield while reducing energy usage and reaction duration. A Box–Behnken design was utilized to investigate the impacts of critical variables including reaction temperature, duration, and catalyst concentration on oil. The results indicated that microwave irradiation effectively accelerated the transesterification reaction, resulting in markedly shorter reaction times relative to traditional approaches. The generated response surface models precisely predicted the biodiesel yield under diverse process conditions. The improved settings, established by the desired function analysis, yielded a high biodiesel output with favorable fuel characteristics that comply with international requirements. This study emphasizes the viability of pumpkin seed oil as a sustainable feedstock for biodiesel synthesis and the effectiveness of microwave-assisted transesterification combined with a response surface methodology for process optimization. Subsequent research should investigate the economic viability and ecological impact of pumpkin seed oil biodiesel production using life-cycle evaluation and cost-benefit analysis.

Funding

This research received no external funding.

Data Availability Statement

Data are contained within the article.

Conflicts of Interest

The author declares no conflicts of interest.

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Figure 1. Cold-pressed oil extraction from pumpkin seeds.
Figure 1. Cold-pressed oil extraction from pumpkin seeds.
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Figure 2. Schematic illustration of the microwave unit.
Figure 2. Schematic illustration of the microwave unit.
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Figure 3. Regression fit between the predicted and experimental yield of pumpkin seed oil biodiesel.
Figure 3. Regression fit between the predicted and experimental yield of pumpkin seed oil biodiesel.
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Figure 4. Main effects of independent variables on biodiesel reaction efficiency based on coded levels (A = reaction temperature, B = catalyst concentration, and C = reaction time).
Figure 4. Main effects of independent variables on biodiesel reaction efficiency based on coded levels (A = reaction temperature, B = catalyst concentration, and C = reaction time).
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Figure 5. Response surface plots showing the effect of (a) catalyst concentration and reaction temp, (b) reaction time and reaction temp, (c) reaction time and catalyst concentration on biodiesel yield.
Figure 5. Response surface plots showing the effect of (a) catalyst concentration and reaction temp, (b) reaction time and reaction temp, (c) reaction time and catalyst concentration on biodiesel yield.
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Figure 6. Separation of pumpkin seed oil blend from byproducts after esterification.
Figure 6. Separation of pumpkin seed oil blend from byproducts after esterification.
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Table 1. Parameters (independent variables) chosen for optimization of microwave irradiation-assisted alkaline-catalyzed transesterification of pumpkin seed oil.
Table 1. Parameters (independent variables) chosen for optimization of microwave irradiation-assisted alkaline-catalyzed transesterification of pumpkin seed oil.
Process ParametersUnitsLevels
−101
(A) Reaction Temp°C505560
(B) KOH catalyst concentration(w/w)%0.511.5
(C) Reaction timemin357
Table 2. RSM analysis of the transesterification process of pumpkin seed oil.
Table 2. RSM analysis of the transesterification process of pumpkin seed oil.
NoTemp
(°C)		Loading KOH Catalyst
(% wt)		Time
(min)		Reaction
Yield %		Predicted
Yield %
1551584.2684.32
2601782.0081.53
3550.5787.2286.98
4501.5576.7576.04
5500.5584.2684.21
6601,5583.0083.05
7551584.0684.32
8551.5781.3581.77
9601382.0081.71
10551585.0084.32
11550.5385.2984.87
12551584.1784.32
13600.5591.5092.21
14551.5372.5172.75
15501368.0068.47
16501779.4979.78
17551584.1184.32
Table 3. Performance index/coefficient of determination statistical fit.
Table 3. Performance index/coefficient of determination statistical fit.
R2 (R-Squared)R2-AdjustedR2-Pred.Adeq Prec.Std. Dev.MeanC.V. %
0.99450.98730.929250.06000.618382.060.7535
Adeq Prec.: adequate precision; Std. Dev.: standard deviation; C.V.: coefficient of variation.
Table 4. Analysis of variance and fit statistics.
Table 4. Analysis of variance and fit statistics.
Source *SSdfMSF-Valuep Value
Model479.56953.28139.37<0.0001Significant
A-A112.501112.50294.26<0.0001
B-B150.161150.16392.77<0.0001
C-C61.94161.94162.01<0.0001
AB0.245010.24500.64090.4497
AC33.01133.0186.33<0.0001
BC11.94111.9431.220.0008
A218.24118.2447.700.0002
B211.31111.3129.580.0010
C280.27180.27209.95<0.0001
Residual2.6870.3823
Lack of Fit2.0830.69204.610.0869Not significant
Pure Error0.600240.1501
Cor Total482.2316
* SS: the sum of the square; df: degree of freedom; MS: mean square; A: reaction temp; B: catalyst concentration; C: reaction time.
Table 5. Fuel properties of the obtained biodiesel.
Table 5. Fuel properties of the obtained biodiesel.
PropertiesUnitEuropean Committee
for Standardization		Biodiesel
Experiments
MinMax
Efficiency%90-91.7 ± 0.56
Density, 25 °Ckg/m3860900884 ± 0.02
Viscosity, 40 °Cmm2/s3.55.04.17 ± 0.17
Flash Point°C120-175 ± 0.37
Cloud Point°C--3 ± 0.08
Pour Point°C--−1 ± 0.12
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Durgut, M.R. Optimized Biodiesel Production from Pumpkin (Cucurbita pepo L.) Seed Oil: A Response Surface Methodology for Microwave-Assisted Transesterification. Processes 2025, 13, 572. https://doi.org/10.3390/pr13020572

AMA Style

Durgut MR. Optimized Biodiesel Production from Pumpkin (Cucurbita pepo L.) Seed Oil: A Response Surface Methodology for Microwave-Assisted Transesterification. Processes. 2025; 13(2):572. https://doi.org/10.3390/pr13020572

Chicago/Turabian Style

Durgut, Mehmet Recai. 2025. "Optimized Biodiesel Production from Pumpkin (Cucurbita pepo L.) Seed Oil: A Response Surface Methodology for Microwave-Assisted Transesterification" Processes 13, no. 2: 572. https://doi.org/10.3390/pr13020572

APA Style

Durgut, M. R. (2025). Optimized Biodiesel Production from Pumpkin (Cucurbita pepo L.) Seed Oil: A Response Surface Methodology for Microwave-Assisted Transesterification. Processes, 13(2), 572. https://doi.org/10.3390/pr13020572

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