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Article

Hydrodynamic Cavitation in Shockwave-Power-Reactor-Assisted Biodiesel Production in Continuous from Soybean and Waste Cooking Oil

by
James R. Vera-Rozo
1,
Edison A. Caicedo-Peñaranda
2 and
José M. Riesco-Avila
3,*
1
GIMUP, Mechanical Engineering Program, University of Pamplona, Pamplona 543050, Colombia
2
GISE, Electrical Engineering Program, University of Pamplona, Pamplona 543050, Colombia
3
Department of Mechanical Engineering, University of Guanajuato, Salamanca 36885, Mexico
*
Author to whom correspondence should be addressed.
Energies 2025, 18(11), 2761; https://doi.org/10.3390/en18112761
Submission received: 20 April 2025 / Revised: 14 May 2025 / Accepted: 19 May 2025 / Published: 26 May 2025
(This article belongs to the Section B: Energy and Environment)
Browse Figures
Versions Notes

Abstract

:
The transesterification process for biodiesel production is constrained by high thermal input, prolonged residence time, and intensive mechanical agitation. This study investigates process intensification via hydrodynamic cavitation using a custom-built Shockwave Power Reactor (SPR), enabling continuous biodiesel synthesis from soybean and used cooking oils. A statistically designed experimental matrix was applied to evaluate the reactor’s transient–stable thermal regime and the influence of operational parameters: rotor speed (1700–3415 rpm), volumetric flow rate (60–105 mL/min), methanol-to-oil molar ratio (6:1 to 12:1), and alkali catalyst type (NaOH or KOH). For benchmarking, conventional alkaline transesterification was optimized. The FAME yields from the SPR system exceeded 96.5% and complied with EN14103 standards. Specific energy analysis showed that cavitation-enhanced transesterification reduced energy consumption and peak temperature compared to traditional methods. The SPR’s capacity to induce high shear and localized turbulence under controlled cavitation offers a promising pathway for low-energy, scalable biodiesel production.

1. Introduction

In recent years, the consumption of alternative fuels has shown a growing trend, primarily due to two factors: legislation in some countries that supports technological developments aimed at environmental protection, and the use of alternative energy sources to petroleum. Additionally, policies such as the Sustainable Development Goals (SDGs) have set specific targets, including the seventh goal (affordable and clean energy). In line with this, various authors have predicted a reduction in pollutant emissions of up to 9.5 Gt of carbon dioxide by 2050 [1], as a result of the increase and optimization of non-conventional technologies, such as the widespread use of biomass and biofuels, which are expected to account for 17% of the energy mix by that year [2].
Particularly, biodiesel has been used globally as renewable fuel additive and blending agent with petroleum-based diesel [3]. According to ASTM specifications, biodiesel is defined as mono-alkyl esters of long-chain fatty acids derived from vegetable oils or animal fats. The use of biodiesel presents new challenges for both the industry and the scientific community, including the use of raw materials that recycle oxygen and provide benefits to the populations near production sites, providing socioeconomic benefits to surrounding communities [4]. Biodiesel is produced by mixing vegetable or animal oil with an alcohol and subjecting the mixture to energy input, resulting in a chemical reaction known as transesterification. This reaction occurs when one mole of triglyceride reacts with three moles of a short-chain alcohol, such as methanol, which is the most commonly used alcohol in industrial production [5]. One classification for the oils used in biodiesel production is based on their use and/or application: palm, soybean, rapeseed, and sunflower oils are considered first-generation due to their use as food; oils such as Jatropha curcas and Ricinus communis are second-generation because they are not suitable for human consumption; and third-generation oils come from sources such as algae or organic waste [6].
Currently, biodiesel has not been able to compete with fossil-based diesel due to production costs; however, it could become more competitive if tax exemptions are applied and production processes are optimized by studying variables such as energy consumption and raw material costs [7]. A particular challenge in the conventional biodiesel production method is the heating of large quantities of material, typically to 60 °C for extended periods of up to 90 min, which leads to high energy consumption [8]. On the other hand, reducing costs through the use of alternative raw materials, such as used vegetable oil, contributes to reduced production costs while facilitating environmentally responsible disposal of waste oils, which can otherwise cause environmental disasters [9].
Reducing reaction time and energy cost per unit of mass could lead to lower biodiesel production costs. To decrease the reaction time, mass transfer between the two immiscible phases must be enhanced. This is due to the significant resistance encountered when mixing polar short-chain alcohols (methanol, ethanol, and butanol) with oils, which consist of a high percentage of non-polar triglycerides, preventing effective molecular contact. To accelerate the reaction within shorter timeframes, catalysts are applied to increase reaction rates, typically basic catalysts such as NaOH and KOH, as well as other types like heterogeneous catalysts and lipases [10].
Traditionally, transesterification is conducted in reactors with heating and agitation to ensure proper mixing of immiscible reactants, resulting in esters and glycerol [11]. To overcome the limitations of high energy and time consumption, several process intensification techniques have been explored, including supercritical methods [12], ultrasound [13], microwaves [14], and hydrodynamic cavitation using orifice plates [15]. Among these, ultrasound and hydrodynamic cavitation have shown the most promising results in terms of efficiency and scalability.
Both methods rely on the phenomenon of cavitation, where the collapse of vapor bubbles releases localized energy that accelerates chemical reactions [16,17]. Ultrasound achieves this through sonic vibration that generates free radicals and enhances reactivity [18], while hydrodynamic cavitation involves abrupt pressure changes induced by flow through an impeller and an orifice plate [19]. Cavitation reactors, particularly rotor–stator systems, have been applied to biodiesel and biogas production due to their ability to enhance contact between reactants [20,21].
However, hydrodynamic cavitation systems using orifice plates and rotor–stator geometries face challenges in processing large volumes and lack precise parameterization due to limited experimental flexibility [20,22]. The Shockwave Power Reactor (SPR) has emerged as a novel solution to these limitations by inducing controlled cavitation through shockwaves, improving phase interaction in immiscible systems like oil and methanol. Recent studies confirm that SPR reduces reaction time and energy consumption while enabling operation at lower temperatures, offering a cost-effective and environmentally friendly alternative for biodiesel production [23,24,25].
A key recent advancement is the geometric characterization of the SPR for biodiesel production, which has enabled the optimization of reactor designs to improve cavitation efficiency and reactant mixing. As part of our ongoing research on SPR technology, in a previous study titled “Geometric characterization of a Shockwave Power Reactor (SPR) for biodiesel production” (Vera-Rozo et al., 2023) [26], we focused specifically on the influence of the reactor’s geometry on shockwave dynamics. In contrast, the present manuscript builds upon that foundation by evaluating the SPR under operational conditions in continuous biodiesel production using different feedstocks. However, the possibility of continuous operation with this device has not yet been evaluated. This analysis is crucial for adapting the SPR to an industrial setting, as a deeper understanding of the reactor’s geometry allows for more effective and cost-efficient process scaling. Furthermore, continuous operation would enable responsible and sustainable production [27]. In the past three years, the Shockwave Power Reactor (SPR) has gained prominence as a promising intensification technology for biodiesel production, particularly due to its capacity to generate controlled cavitation, enhance mixing, and reduce energy consumption. Recent studies have demonstrated its superior performance in esterifying high-FFA feedstocks such as castor and karanja oils, achieving conversion efficiencies of up to 99.5% with significantly reduced energy input and reaction time [28]. Moreover, SPR-based transesterification has shown consistent improvements in FAME yields under continuous operation, highlighting its industrial scalability and operational robustness [29]. These advances position SPR as a key reactor technology among modern intensification approaches, standing out for its simplicity, high shear and turbulence generation, and reduced reliance on harsh conditions or excess reagents [30]. This growing body of work confirms the relevance and potential of SPR in modern biodiesel process engineering.
The primary objective of this work is to study the influential variables of a custom-designed rotor–stator or Shockwave Power Reactor (SPR) in the transesterification reaction for biodiesel production using soybean oil and waste cooking oil (WCO). This study explores the effect of key operational parameters such as flow rate, feed configuration, and rotor speed on biodiesel production using cavitation. The analysis begins with yield optimization for both feedstocks, followed by an assessment of the reactor’s thermal behavior. Comparative results using experimental designs offer insights into how energy demand responds to variations in process conditions, highlighting the potential of this technology for intensified biodiesel synthesis.

2. Materials and Methods

2.1. Materials

The transesterification reactions were carried out using two feedstocks: refined soybean oil as a first-generation raw material and waste cooking oil (WCO) as a second-generation feedstock. Methanol with 99.8% purity, NaOH pellets, and KOH flakes, both of analytical grade, were used as reagents. Distilled water was used for dilutions during analysis and for washing the biodiesel. To determine the fatty acid methyl ester (FAME) content of the biodiesel, heptadecanoate (C17) and heptane, both with a purity above 99%, were used as internal standards, following the EN 14214 standard [31].

2.2. Traditional Process

The traditional transesterification process was conducted based on established protocols reported in previous studies, which identify NaOH and KOH as the most effective homogeneous catalysts for soybean oil and WCO conversion [8]. The oil samples were preheated to 65 °C and maintained at that temperature for at least 10 min to ensure thermal stability. In parallel, methanol and the selected catalyst were mixed separately to prepare the methoxide solution. Once the oil reached a stable temperature, the methoxide was added, and the reaction mixture was subjected to mechanical stirring at 1000 rpm for 120 min. Upon completion of the reaction, the mixture was transferred to a separation funnel and left to settle under static conditions for 24 h to allow for phase separation between biodiesel and glycerol.

2.3. Cavitation Process

The reactor used to generate cavitation that intensifies the transesterification reaction is known as a shockwave or rotor–stator reactor. In this study, a custom design is presented, with geometric variables tested and characterized in previous studies [26]. The evaluation of the prototype is initially carried out through a mixing process, where the reactants enter the cavitator. These are driven by two volumetrically calibrated dosing pumps to maintain the molar ratio of the oil and alcohol mixture with the catalyst. The experimental setup is shown in Figure 1.

2.4. Oil and Biodiesel Characterization

The determination of oil properties is of great importance in biodiesel production. The measurement of density, viscosity, acid value, gums, and other properties plays a key role in obtaining favorable FAME and, consequently, achieving a complete transesterification reaction [32]. The protocol followed for determining the fatty acids present in each oil is NMX-F-101-SCFI-2012. For density and viscosity measurements, ASTM D1298 and ASTM D445 standards were applied, respectively [33,34]. Density was determined using a hydrometer, while viscosity was measured using a Cannon-Fenske capillary viscometer, in accordance with the specified standards. These procedures were followed for both the raw oils and the purified biodiesel obtained from the reaction.
Additionally, for the characterization of the biodiesel fuel, certain properties were evaluated following ASTM D6751 and EN 14214 standards [31,35]. These included FAME under EN 14103 and distillation range under ASTM D86 [36,37]. The cetane number was determined based on the biodiesel’s evaporation temperature [38]. The heating value was determined based on ASTM D 240 [39].

2.5. Experimental Design

The experimental sequence is shown in Figure 2. It consists of three stages, where the first involves the traditional production of biodiesel to determine the best conditions to be tested in the second stage. In this second stage, biodiesel is produced by cavitation, and finally, the obtained biodiesel is characterized. The response and optimization criteria are the yield (defined as the amount of oil converted to biodiesel after separation) and FAME.

2.5.1. Factorial Design in the Traditional Process

To evaluate the influence of key process variables on conventional transesterification, a 23 full factorial design was selected. This design was chosen for its efficiency in analyzing both main effects and two-way interactions among three critical factors: catalyst concentration (0.6–1.5 %wt), catalyst type (NaOH and KOH), and methanol-to-oil molar ratio (6:1–9:1) [30]. These variables were selected based on preliminary experiments and their known relevance in alkali-catalyzed transesterification systems. The factorial matrix enabled systematic evaluation of FAME yield under controlled conditions. The results guided the identification of the most influential parameters for maximizing conversion efficiency. An overview of this experimental setup is presented in Figure 3.

2.5.2. Central Composite Design in the Cavitation Process

To evaluate the performance of the SPR in continuous biodiesel production, an experimental plan was developed to study the effect of two key operational parameters: rotor speed and flow rate. These variables were selected because they strongly influence cavitation intensity, energy transfer, and residence time within the reactor. Due to the novelty of applying hydrodynamic cavitation under continuous flow conditions, it was necessary to explore a wide operating range—rotor speeds from 586 to 3415 rpm and flow rates from 150 to 300 mL/min—to understand the reactor’s dynamic response and process robustness.
A central composite design was selected over a traditional factorial design because it enables the investigation of curvature effects in the response surface without requiring an exhaustive number of experiments. This was especially valuable given the broad operating ranges and the nonlinear behavior expected from the cavitation-driven transesterification process. The main response variable was the FAME content, evaluated according to the EN 14214 and ASTM D6751 standards [31,35]. A summary of the experimental sequence is provided in Figure 4.

3. Results and Discussions

3.1. Oil Characterization

The fatty acid (FA) composition and some other properties of soybean oil and WCO are presented in Table 1. Both oil compositions show a high content of oleic and linoleic acid. In the case of soybean oil, being a refined oil, it has a low percentage of free fatty acids at 0.13%wt, while for WCO, being a recycled oil, the percentage of free fatty acids increases to 0.72%wt, which will result in a decrease in transesterification efficiency.

3.2. Results of Factorial Design in the Traditional Process

Based on the variation of the factors described in Section 2.5.1, it was determined that the best conversion occurred with NaOH, at a concentration of 0.6%wt and a methanol-to-oil molar ratio of 9:1, achieving a 95.06%wt conversion and 98.58%wt FAME content. For KOH, the only condition that met the minimum 96.5%wt FAME content specified by the EN 14214 standard [31] was with a concentration of 1.5%wt and a methanol-to-oil molar ratio of 9:1, yielding 84.07%wt conversion and 96.94%wt FAME (see Table 2). The performance of both feedstocks using NaOH and KOH has been studied by multiple authors, who have found that KOH generally achieves better conversion regardless of the feedstock, while NaOH provides the highest FAME content.

3.3. Results of Central Composite Design in the Cavitation Process with Transient and Steady States

The performance evaluation of the SPR reactor during start-up involves two distinct operational phases: the transient and steady states. The transient state refers to the period in which external factors—such as ambient temperature, humidity, and thermal inertia—can influence the reactor’s internal conditions and response variables. The system reaches a steady state when these variables stabilize and no longer vary significantly over time. To assess the behavior of the SPR during these phases, internal temperature measurements were recorded, and samples were collected at both the reactor inlet and outlet to determine the progression of the transesterification reaction. Specifically, FAME content was used as a kinetic indicator over time (see Figure 5). These experiments were conducted under the optimal conditions listed in Table 3, using refined soybean oil—selected for its minimal variability—and a product outlet flow rate of 250 mL/min.
Figure 5 clearly shows that the reactor temperature has a direct correlation with the amount of oil converted into biodiesel. Additionally, it is evident that after 20 min, the variation in these two variables is minimal, so for the experiments, samples were taken after this operational period. The temperature readings from the thermocouples inside the reactor were verified using a Fluke T401 thermal imaging camera (see Figure 6), which clearly indicates that, after the temperature stabilizes, cavitation occurs uniformly according to the stable reactor temperature. Before stabilization, the heating process begins. Figure 6 shows the external view of the SPR device during operation, highlighting the temperature distribution across the reactor surface. The thermal camera image confirms the uniform heat distribution essential for initiating cavitation. The main components visible include the heating system, reactor body, and inlet/outlet connections, as well as the thermal gradient along the reaction chamber. This figure validates the thermal stability of the operating conditions and reinforces the reproducibility and robustness of the experimental configuration.

3.4. Results of Central Composite Design in the Cavitation Process with Flow and Rotation Speed Factors

The continuous and steady-state biodiesel production is carried out by operating both pumps (see Figure 1), where each reactant is introduced separately into the SPR reactor. The results presented in Table 3 are calculated as the average of samples taken at 20, 24, and 27 min of reactor operation, in order to calculate a standard deviation and demonstrate the minimal variation of the equipment.
At a rotor speed of 3415 rpm, the SPR achieved the highest FAME yields for both soybean oil and WCO, indicating that elevated rotational speeds enhance cavitation intensity and promote more efficient conversion of triglycerides to methyl esters. Conversely, lower flow rates were associated with higher FAME content, which is attributed to longer residence times within the reactor, allowing the reaction to proceed more completely. The statistical analysis revealed that only rotor speed and flow rate significantly influenced the FAME yield, while quadratic and interaction effects were negligible. Figure 7 and Figure 8 illustrate that both feedstocks follow similar trends, likely due to their comparable fatty acid profiles. Nonetheless, the FAME content obtained from WCO was slightly lower, which can be attributed to its higher free fatty acid content relative to soybean oil.
As observed, Figure 7 and Figure 8 display similar trends. This similarity reflects the comparable fatty acid composition of both soybean oil and WCO, as the latter is derived from used soybean oil. Consequently, the transesterification of both feedstocks leads to the formation of methyl esters with similar characteristics, resulting in comparable reaction behavior and yield profiles.
Figure 9 presents the main effects of rotation velocity and flow rate on the FAME yield obtained from soybean oil. The trend observed for soybean oil is consistent with that of waste cooking oil (WCO), as both feedstocks exhibit similar response behavior. The FAME yield increases with rotation velocity up to approximately 2000 rpm, reaching an optimal point, and then declines at higher speeds likely due to excessive turbulence that reduces effective cavitation. Conversely, increasing the flow rate results in a steady decrease in FAME yield, suggesting that shorter residence times limit the extent of the transesterification reaction. These trends confirm that intermediate rotor speeds and lower flow rates are favorable for maximizing biodiesel conversion under continuous cavitation-assisted conditions.

3.5. Comparison of Biodiesel Obtained

The comparison of the biodiesel produced was conducted using the best results from each experiment under identical reaction conditions. These conditions involved a methanol-to-oil molar ratio of 9:1 and 0.6%wt NaOH as the catalyst. The results in Table 4 show an almost constant trend, regardless of the production method, which clearly indicates that the transesterification reaction is independent of the method used to induce it, resulting in similar products.
Energy consumption can be compared by approximating the continuous process during the steady-state phase with the amount of biodiesel traditionally produced in 120 min. For this experiment, 135 mL of oil and methoxide were prepared using the traditional method, which corresponds to approximately 35 s of operation in the SPR reactor. The traditional system consumes around 1.04 kWh, whereas the SPR reactor uses 2.86 kWh. However, considering the operation time is only 0.5 min in the SPR reactor compared to 120 min in the traditional system, the energy savings are evident. While this comparison is not entirely accurate due to scalability principles in the experiment, it provides a considerable approximation, highlighting that reaction intensification through cavitation significantly improves both the process efficiency and the biodiesel production time.

4. Conclusions

The implementation of a hydrodynamic cavitation reactor—specifically, a custom-designed Shockwave Power Reactor (SPR)—as a process intensifier for the transesterification reaction has proven to be a highly effective technological strategy to enhance biodiesel production. The findings of this study confirm that hydrodynamic cavitation not only reduces reaction time and energy requirements but also maintains compliance with key fuel quality standards such as EN 14103 and ASTM D6751, even when utilizing low-cost feedstocks like waste cooking oil (WCO).
A key outcome of the study is the enhanced conversion of triglycerides into fatty acid methyl esters (FAME) achieved at elevated rotor speeds (up to 3415 rpm), demonstrating the reactor’s improved performance under these conditions. Although the precise internal mechanisms were not directly observed in this study, the previous literature suggests that cavitation phenomena may contribute to enhanced conversion by promoting micro-mixing, increasing interfacial area, and inducing localized energy effects. These factors, reported in earlier SPR studies, are consistent with the improved performance observed under the operating conditions tested.
Furthermore, thermal regulation within the SPR is governed by the controlled evaporation and condensation of methanol, which stabilizes the reactor temperature near 65 °C. This thermodynamic behavior enables the coexistence of methanol in both liquid and vapor phases, enhancing mass transfer between the immiscible oil and alcohol phases. This mechanism constitutes a self-regulating thermal environment that supports energy-efficient and thermally stable reaction conditions.
The results obtained under continuous operation show that, beyond the technical feasibility of intensifying transesterification, the SPR exhibits operational stability, reproducibility, and robustness, fulfilling the key prerequisites for process scalability. The parametric analysis, performed via a central composite design, clearly identified rotor speed and flow rate as the primary drivers of FAME yield, while interaction and quadratic terms were statistically negligible. These findings highlight the importance of optimizing mechanical design and hydrodynamic conditions over chemical input in intensified reactors.
From an engineering standpoint, this work contributes valuable insights into the design and optimization of continuous cavitation-based reactors. The demonstrated energy savings—when normalized per unit of biodiesel produced—offer a substantial advantage over traditional batch heating systems. In addition, the modular nature of rotor–stator systems opens avenues for integration into decentralized biodiesel production units, particularly in rural or agro-industrial contexts where WCO availability is abundant.
Nonetheless, this study also identifies critical aspects that warrant further investigation. These include the long-term mechanical durability of the SPR under continuous operation, potential fouling or wear due to high-speed cavitation, and the integration of downstream separation units for glycerol and unreacted methanol recovery. Additionally, exploration of heterogeneous catalysis and the use of alternative alcohols (e.g., ethanol or butanol) could further improve process sustainability and reduce purification demands.
The SPR-based hydrodynamic cavitation system represents a promising and scalable solution for the intensified production of biodiesel. Its capability to deliver high reaction efficiency with reduced energy input and shorter processing times positions it as a transformative tool for future biofuel technologies, aligned with the principles of sustainable process engineering and the global transition toward clean energy.

Author Contributions

Conceptualization, methodology, and analysis results, J.R.V.-R. and J.M.R.-A.; experimentation, data curation, and validation, J.R.V.-R. and E.A.C.-P.; writing—original draft preparation, J.R.V.-R. and J.M.R.-A.; writing—review and editing, J.R.V.-R., E.A.C.-P. and J.M.R.-A. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Data Availability Statement

The original contributions presented in the study are included in the article, further inquiries can be directed to the corresponding author.

Acknowledgments

We acknowledge the University of Guanajuato and the University of Pamplona for the support provided in the completion of this work.

Conflicts of Interest

The authors declare no conflicts of interest.

References

  1. Asmelash, E.; Prakash, G.; Gorini, R.; Gielen, D. Role of IRENA for global transition to 100% renewable energy. In Accelerating the Transition to a 100% Renewable Energy Era; Springer: Cham, Switzerland, 2020; pp. 51–71. [Google Scholar]
  2. Hassan, Q.; Viktor, P.; Al-Musawi, T.J.; Ali, B.M.; Algburi, S.; Alzoubi, H.M.; Jaszczur, M. The renewable energy role in the global energy transformations. Renew. Energy Focus 2024, 48, 100545. [Google Scholar] [CrossRef]
  3. Aljaafari, A.; Fattah, I.M.R.; Jahirul, M.I.; Gu, Y.; Mahlia, T.M.I.; Islam, M.A.; Islam, M.S. Biodiesel emissions: A state-of-the-art review on health and environmental impacts. Energies 2023, 16, 2086. [Google Scholar] [CrossRef]
  4. de la Rosa-Urbalejo, D.; Reyes-Ramírez, B.; Riesco-Ávila, J.M.; Vera-Rozo, J.R.; Martínez-Martínez, S.; de la Garza, O.A. An on-road experimental emissions evaluation of a diesel engine fueled with pyrolysis oil from waste plastics, pure and blended with biodiesel—A Mexican case. Int. J. Engine Res. 2024, 26, 1234–1245. [Google Scholar] [CrossRef]
  5. Pradana, Y.S.; Makertihartha, I.G.; Indarto, A.; Prakoso, T.; Soerawidjaja, T.H. A review of biodiesel cold flow properties and its improvement methods. Energies 2024, 17, 4543. [Google Scholar] [CrossRef]
  6. Rivas, A.G.; Vázquez, V.Á.; Flores, M.M.A.; Cerrillo-Rojas, G.V.; Correa-Aguado, H.C. Sustainable castor bean biodiesel through Ricinus communis L. lipase extract catalysis. Appl. Biochem. Biotechnol. 2023, 195, 1297–1318. [Google Scholar] [CrossRef]
  7. Akpan, I.O.; Edeh, I.; Uyigue, L. A review on biodiesel production. Petro Chem. Indus. Int. 2023, 6, 131–141. [Google Scholar]
  8. Vera-Rozo, J.R.; Riesco-Ávila, J.M.; Elizalde-Blanca, F.; Cano-Andrade, S. Optimization of the real conversion efficiency of waste cooking oil to FAME. Therm. Sci. 2022, 26, 653–665. [Google Scholar] [CrossRef]
  9. Lopresto, C.G.; De Paola, M.G.; Calabrò, V. Importance of the properties, collection, and storage of waste cooking oils to produce high-quality biodiesel. Biomass Bioenergy 2024, 189, 107363. [Google Scholar] [CrossRef]
  10. Rizwanul Fattah, I.M.; Ong, H.C.; Mahlia, T.M.I.; Mofijur, M.; Silitonga, A.S.; Rahman, S.A.; Ahmad, A. State of the art of catalysts for biodiesel production. Front. Energy Res. 2020, 8, 101. [Google Scholar] [CrossRef]
  11. Gopi, R.; Thangarasu, V.; Ramanathan, A.; Ramanathan, A. A critical review of continuous flow and integrated microreactors for biodiesel. Renew. Sustain. Energy Rev. 2022, 154, 111869. [Google Scholar]
  12. Qadeer, M.U.; Ayoub, M.; Komiyama, M.; Daulatzai, M.U.K.; Mukhtar, A.; Saqib, S.; Bokhari, A. Biodiesel synthesis technologies: Review and economic analysis. J. Clean. Prod. 2021, 309, 127388. [Google Scholar] [CrossRef]
  13. Patle, D.S.; Pandey, A.; Srivastava, S.; Sawarkar, A.N.; Kumar, S. Ultrasound-intensified biodiesel production from algal biomass. Environ. Chem. Lett. 2021, 19, 209–229. [Google Scholar] [CrossRef]
  14. Rhithuparna, D.; Ghosh, N.; Rokhum, S.L.; Halder, G. Current progress and future outlooks of microwave-irradiated biodiesel production: A holistic review. Chem. Eng. J. 2024, 482, 149033. [Google Scholar]
  15. Vera-Rozo, J.R.; Riesco-Ávila, J.M.; Poveda-Pachon, M.Y.; Zaleta-Aguilar, A. Biodiesel production by hydrodynamic cavitation through an orifice plate. Chem. Eng. Trans. 2022, 92, 565–570. [Google Scholar]
  16. Wen, Z.; Wang, F.; Zhang, L.; Cai, Z.; Liu, S. Application of ultrasonic cavitation in biodiesel production: A review. Renew. Energy 2021, 169, 1–12. [Google Scholar]
  17. Patil, P.D.; Gude, V.G.; Deng, S. Hydrodynamic cavitation as a novel intensification approach for biodiesel production. Energy Convers. Manag. 2022, 251, 114940. [Google Scholar]
  18. Brennen, C.E. Cavitation and Bubble Dynamics; Cambridge University Press: Cambridge, UK, 2020. [Google Scholar]
  19. Giannakis, N.; Carmona-Cabello, M.; Makri, A.; Leiva-Candia, D.; Filippi, K.; Argeiti, C.; Pateraki, C.; Dorado, M.P.; Koutinas, A.; Stylianou, E. Spent coffee grounds and orange peel residues based biorefinery for microbial oil and biodiesel conversion estimation. Renew. Energy 2023, 209, 382–392. [Google Scholar] [CrossRef]
  20. Al-Hasan, M.; Al-Mazidi, M.; Khan, Z. Influence of hydrodynamic cavitation on biodiesel yield from WCO. J. Clean. Prod. 2021, 316, 128214. [Google Scholar]
  21. Zhang, H.; Liu, Y.; Wu, X.; Lu, X. Advances in cavitation technology for renewable energy production. Renew. Sustain. Energy Rev. 2023, 154, 111876. [Google Scholar]
  22. Patel, A.; Joshi, R.; Upadhyay, S. Cavitation-based reactors for biodiesel production: Design and analysis. Chem. Eng. Process. 2021, 168, 108564. [Google Scholar]
  23. Wang, Y.; Liu, H.; Zhang, J. Application of SPR for biodiesel production: A review. Renew. Energy 2020, 150, 578–585. [Google Scholar] [CrossRef]
  24. Lee, S.; Park, J.; Kim, H. Enhancing biodiesel yield using Shockwave Power Reactor technology. J. Clean. Prod. 2022, 310, 127430. [Google Scholar]
  25. Jiang, T.; Zhao, L.; Ma, X. Optimizing biodiesel production using SPR: Low-temp kinetics and energy savings. Energy Convers. Manag. 2021, 228, 113646. [Google Scholar]
  26. Vera-Rozo, J.R.; Gonzalez-Aguilar, A.M.; Riesco-Ávila, J.M. Geometric characterization of a Shockwave Power Reactor for biodiesel. Chem. Eng. Process. 2023, 190, 109418. [Google Scholar] [CrossRef]
  27. Zhou, Y.; Hu, W.; Liu, P. Sustainable biodiesel production using SPR: Towards scalability. Fuel Process. Technol. 2023, 234, 107369. [Google Scholar]
  28. Oza, S.; Kodgire, P.; Kachhwaha, S.S. Shockwave power reactor (SPR)-assisted esterification of blended non-edible oils: Optimization and kinetics studies. Therm. Sci. Eng. Prog. 2025, 59, 103337. [Google Scholar] [CrossRef]
  29. Prajapati, A.K.; Ali, S.S.; Ansari, K.B.; Athar, M.; Al Mesfer, M.K.; Shah, M.; Danish, M.; Kumar, R.; Raheman, S. Process intensification in biodiesel production using unconventional reactors. Fuel 2025, 380, 133263. [Google Scholar] [CrossRef]
  30. Miyuranga, K.A.V.; Arachchige, U.S.P.R.; Marso, T.M.M.; Samarakoon, G. Biodiesel production through the transesterification of waste cooking oil over typical heterogeneous base or acid catalysts. Catalysts 2023, 13, 546. [Google Scholar] [CrossRef]
  31. EN 14214:2012; Liquid Petroleum Products–Fatty Acid Methyl Esters (FAME) for Use in Diesel Engines and Heating Applications–Requirements and Test Methods. European Committee for Standardization (CEN): Brussels, Belgium, 2012.
  32. Vera-Rozo, J.R.; Sáez-Bastante, J.; Carmona-Cabello, M.; Riesco-Ávila, J.M.; Avellaneda, F.; Pinzi, S.; Dorado, M.P. Cetane index prediction based on biodiesel distillation curve. Fuel 2022, 321, 124063. [Google Scholar] [CrossRef]
  33. ASTM D1298; Standard Test Method for Density, Relative Density (Specific Gravity), or API Gravity of Crude Petroleum and Liquid Petroleum Products by Hydrometer Method. ASTM International: West Conshohocken, PA, USA, 2012.
  34. ASTM D445; Standard Test Method for Kinematic Viscosity of Transparent and Opaque Liquids (and Calculation of Dynamic Viscosity). ASTM International: West Conshohocken, PA, USA, 2006.
  35. ASTM D6751; Standard Specification for Biodiesel Fuel Blend Stock (B100) for Middle Distillate Fuels. ASTM International: West Conshohocken, PA, USA, 2020.
  36. EN 14103:2020; Fat and Oil Derivatives – Fatty Acid Methyl Esters (FAME) – Determination of Ester and Linolenic Acid Methyl ester Contents. European Committee for Standardization (CEN): Brussels, Belgium, 2020.
  37. ASTM D86; Standard Test Method for Distillation of Petroleum Products and Liquid Fuels at Atmospheric Pressure. ASTM International: West Conshohocken, PA, USA, 2023.
  38. ASTM D240; Standard Test Method for Heat of Combustion of Liquid Hydrocarbon Fuels by Bomb Calorimeter. ASTM International: West Conshohocken, PA, USA, 2019.
  39. Antony, J. Design of Experiments for Engineers and Scientists, 3rd ed.; Elsevier: Amsterdam, The Netherlands, 2023. [Google Scholar]
  40. ASTM D4052; Standard Test Method for Density, Relative Density, and API Gravity of Liquids by Digital Density Meter. ASTM International: West Conshohocken, PA, USA. Available online: https://wiki.anton-paar.com/jp-jp/density-and-density-measurement/astm-d4052/ (accessed on 18 May 2025).
  41. NMX-F-101-SCFI-2012; Alimentos–Aceites Y Grasas Vegetales O Animales–Determinación De Ácidos Grasos Libres-Método De Prueba (CANCELA A LA NMX-F-101-SCFI-2006). Secretaría de Economía: Mexico City, Mexico. Available online: http://www.economia-nmx.gob.mx/normas/nmx/2010/nmx-f-101-scfi-2012.pdf (accessed on 18 May 2025).
  42. EN 14203:2011; Blinds and Shutters-Capability for Use of Gears with Crank Handle-Requirements and Test Methods. European Committee for Standardization (CEN): Brussels, Belgium. Available online: https://standards.iteh.ai/catalog/standards/cen/c700dfda-b681-4cdf-900f-475f017a76da/en-14203-2004?srsltid=AfmBOopyTwjA97sDqHZigGvRLBKuRS_Bvx29a92PGRTqPI9uRkx0qDzy (accessed on 18 May 2025).
  43. EN 14112:2021; Fat and Oil Derivatives—Fatty Acid Methyl Esters (FAME)—Determination of Oxidation Stability (Accelerated Oxidation Test). SIST Slovenian Institute for Standardization: Ljubljana, Slovenia. Available online: https://cdn.standards.iteh.ai/samples/66922/49757a201d91465c837f02ac2541337d/SIST-EN-14112-2021.pdf (accessed on 18 May 2025).
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Figure 1. Continuous biodiesel production system by hydrodynamic cavitation.
Figure 1. Continuous biodiesel production system by hydrodynamic cavitation.
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Figure 2. Experimentation sequence.
Figure 2. Experimentation sequence.
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Figure 3. Factorial design in the traditional process.
Figure 3. Factorial design in the traditional process.
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Figure 4. Central composite design in the cavitation process.
Figure 4. Central composite design in the cavitation process.
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Figure 5. Biodiesel reaction kinetics: Temperature and FAME vs. time.
Figure 5. Biodiesel reaction kinetics: Temperature and FAME vs. time.
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Figure 6. Thermal camera images for transitory and steady states. (a) Transitory state (12 min). (b) Steady state (25 min).
Figure 6. Thermal camera images for transitory and steady states. (a) Transitory state (12 min). (b) Steady state (25 min).
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Figure 7. Results for the soybean experimental design central composite.
Figure 7. Results for the soybean experimental design central composite.
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Figure 8. Results for WCO experimental design central composite.
Figure 8. Results for WCO experimental design central composite.
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Figure 9. Factor graph (left: WCO; right: soybean).
Figure 9. Factor graph (left: WCO; right: soybean).
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Table 1. Comparison of the properties of soybean oil and waste cooking oil (WCO).
Table 1. Comparison of the properties of soybean oil and waste cooking oil (WCO).
PropertiesStandardSoybeanWCO
Density at 15 °C (kg/m3)ASTM D4052 [40]920.30 ± 0.1925.1 ± 0.1
Kinematic Viscosity at 40 °C (mm2/s)ASTM D44551.32 ± 0.0170.46 ± 0.01
Free FA, wt (%)NMX-F-101 [41]0.13 ± 0.030.72 ± 0.04
Molecular Weight, g/molEN 14203:2011 [42]928.39 ± 0.05928.83 ± 0.05
Fatty AcidFormula%wt ± 0.01%wt ± 0.01
Palmitic (C16:0)C16H28O210.7411.71
Palmitoleic (C16:1)C16H30O20.10-
Stearic (C18:0)C18H36O24.054.24
Oleic (C18:1)C18H34O224.0529.96
Linoleic (C18:2)C18H32O253.3648.36
Linolenic (C18:3)C18H30O27.485.72
Arachidonic (C20:0)C20H32O20.170.01
Others (-)-0.050.01
Table 2. Experimental results of traditional transesterification.
Table 2. Experimental results of traditional transesterification.
PropertiesStandardCatalyst
Percentage		SoybeanWCO
Conversion
[%wt]		FAME
[%wt] 		Conversion
[%wt]		FAME
[%wt]
NaOH6.0:10.6095.87 ± 1.1196.47 ± 1.6792.13 ± 1.1684.76 ± 0.86
1.5070.96 ± 0.7490.01 ± 0.8591.81 ± 1.7280.83 ± 0.59
7.5:11.0589.51 ± 1.3094.51 ± 1.0975.17 ± 1.5280.27 ± 0.72
9.0:10.6095.06 ± 2.8498.58 ± 1.8588.39 ± 1.2295.30 ± 0.26
1.5063.80 ± 0.0896.82 ± 0.0491.91 ± 1.1788.10 ± 0.34
KOH6.0:10.6097.51 ± 0.7290.50 ± 0.5493.98 ± 1.2087.50 ± 0.70
1.5087.06 ± 2.4786.59 ± 1.4174.90 ± 1.3888.50 ± 0.48
7.5:11.0592.77 ± 0.4189.20 ± 0.1786.57 ± 1.5079.90 ± 0.87
9.0:10.6097.08 ± 1.0193.65 ± 0.8792.55 ± 1.1479.70 ± 0.52
1.5084.07 ± 0.4896.94 ± 0.1093.13 ± 1.6794.10 ± 0.98
Table 3. FAME percentage at different experimental conditions for soybean and waste cooking oil (WCO).
Table 3. FAME percentage at different experimental conditions for soybean and waste cooking oil (WCO).
ExperimentRotation Velocity [rpm]Flow [mL/min]FAME to Soybean Oil [%wt]FAME to WCO [%wt]
Factor points
1100020087.01 ± 0.0484.46 ± 0.03
2100030085.08 ± 0.8983.31 ± 0.87
3300020093.97 ± 0.0492.16 ± 0.04
4300030091.89 ± 1.0590.28 ± 0.20
Axial points
558625079.18 ± 0.0377.65 ± 0.03
6341525097.98 ± 0.0595.85 ± 0.05
7200015097.00 ± 0.0595.22 ± 0.50
8200035084.05 ± 0.0381.59 ± 0.03
Central point
9200025091.91 ± 0.0489.68 ± 0.04
Table 4. Biodiesel properties comparison.
Table 4. Biodiesel properties comparison.
ParameterStandardSoybean BiodieselWCO Biodiesel
Traditional
Process		Cavitation
Process		Traditional ProcessCavitation
Process
FAME (%wt)EN 14103 Min: 96.598.58 ± 0.0197.98 ± 0.0295.3 ± 0.0195.85 ± 0.01
LinolenicEN 14103 Max: 127.48 ± 0.057.36 ± 0.085.72 ± 0.125.81 ± 0.03
High Calorific Value, HCV (MJ/kg)ASTM D240 [39]39.82 ± 0.0138.84 ± 0.0139.80 ± 0.0139.81 ± 0.01
Density at 15 °C (kg/m3)ASTM D4052 Min 860 Max 9000.884 ± 0.0210.884 ± 0.0500.886 ± 0.0360.886 ± 0.007
Kinematic Viscosity at 40 °C (mm2/s)ASTM D445
Min 3.5 Max 5.0		5.45 ± 0.015.36 ± 0.015.81 ± 0.015.58 ± 0.01
Cetane Number (CN)EN 14112 Min.51 [43]49505150
Note: The best continuous experiment with a speed of 3415 rpm and a flow rate of 250 mL/min was the one characterized.
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Vera-Rozo, J.R.; Caicedo-Peñaranda, E.A.; Riesco-Avila, J.M. Hydrodynamic Cavitation in Shockwave-Power-Reactor-Assisted Biodiesel Production in Continuous from Soybean and Waste Cooking Oil. Energies 2025, 18, 2761. https://doi.org/10.3390/en18112761

AMA Style

Vera-Rozo JR, Caicedo-Peñaranda EA, Riesco-Avila JM. Hydrodynamic Cavitation in Shockwave-Power-Reactor-Assisted Biodiesel Production in Continuous from Soybean and Waste Cooking Oil. Energies. 2025; 18(11):2761. https://doi.org/10.3390/en18112761

Chicago/Turabian Style

Vera-Rozo, James R., Edison A. Caicedo-Peñaranda, and José M. Riesco-Avila. 2025. "Hydrodynamic Cavitation in Shockwave-Power-Reactor-Assisted Biodiesel Production in Continuous from Soybean and Waste Cooking Oil" Energies 18, no. 11: 2761. https://doi.org/10.3390/en18112761

APA Style

Vera-Rozo, J. R., Caicedo-Peñaranda, E. A., & Riesco-Avila, J. M. (2025). Hydrodynamic Cavitation in Shockwave-Power-Reactor-Assisted Biodiesel Production in Continuous from Soybean and Waste Cooking Oil. Energies, 18(11), 2761. https://doi.org/10.3390/en18112761

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