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Processes
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Circular Economy on Production Processes and Systems Engineering
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Circular Economy on Production Processes and Systems Engineering

A special issue of Processes (ISSN 2227-9717). This special issue belongs to the section "Sustainable Processes".

Deadline for manuscript submissions: 30 September 2025 | Viewed by 4528

Special Issue Editors

Prof. Dr. Lucian-Ionel Cioca

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Guest Editor
Industrial Engineering and Management Department, Faculty of Engineering, Lucian Blaga University of Sibiu, 10 Victoriei Blv., 550024 Sibiu, Romania
Interests: management; human resources management; occupational health and safety management; production systems engineering; ergonomics; circular economy
Special Issues, Collections and Topics in MDPI journals
Dr. Elena Simina Lakatos

E-Mail Website
Guest Editor
Institute for Research in Circular Economy and Environment "Ernest Lupan", 400609 Cluj-Napoca, Romania
Interests: social development and community sustainability; entrepreneurship and circular economy; sustainable development and environmental protection
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The circular economy (CE) significantly impacts production processes, changing the traditional linear model of “take, make, throw away” to a more sustainable and restorative approach. In a circular economy, products and materials are kept in use for as long as possible, and waste and resource consumption are minimized. The following are some key impacts on production processes: 

  • Resource efficiency: Circular economy principles prioritize using fewer raw materials by reusing, remanufacturing, and recycling existing resources. This leads to more efficient production processes that reduce the demand for virgin materials, which can reduce costs and environmental impact.
  • Design for longevity: Manufacturers are encouraged to design products with longer life cycles, easier repairability, and modular components. This results in a shift toward more durable goods that can be reconditioned, upgraded, or reused rather than discarded after a short lifespan. This affects production regarding design, material selection, and assembly methods.
  • Energy reduction: Reusing materials and reducing the need for new raw materials can make production processes less energy-intensive. For example, recycling materials often uses less energy than producing new materials from scratch.
  • Waste reduction: In a circular economy, waste is minimized by recycling, repurposing, and reusing materials. This reduces the overall environmental footprint of production, reducing waste and landfill pollution. Manufacturers focus on creating processes where waste is a resource rather than an end product.

In short, the circular economy reshapes production to be more sustainable, resource-efficient, and waste-friendly, fostering long-term economic, environmental, and social benefits. It stimulates innovation, reduces costs, and promotes a shift towards sustainability in both production and consumption.

In the current Special Issue, titled "Circular Economy on Production Processes and Systems Engineering", we invite researchers to contribute their recent scientific works on this topic.

Prof. Dr. Lucian-Ionel Cioca
Dr. Elena Simina Lakatos
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Processes is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • circular economy
  • resource efficiency
  • design for longevity
  • energy reduction
  • waste reduction

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Published Papers (8 papers)

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Research

15 pages, 2293 KiB  
Article
Preparing and Characterizing Nano Relative Permeability Improver for Low-Permeability Reservoirs
by Bo Li
Processes 2025, 13(7), 2071; https://doi.org/10.3390/pr13072071 - 30 Jun 2025
Viewed by 265
Abstract
Aiming at the problems of insufficient natural productivity and large seepage resistance in low-permeability oil and gas reservoirs, a nano relative permeability improver based on nano SiO2 was developed in this study. The nano relative permeability improver was prepared by the reversed-phase [...] Read more.
Aiming at the problems of insufficient natural productivity and large seepage resistance in low-permeability oil and gas reservoirs, a nano relative permeability improver based on nano SiO2 was developed in this study. The nano relative permeability improver was prepared by the reversed-phase microemulsion method, and the formula was optimized (nano SiO2 5.1%, Span-80 33%, isobutanol 18%, NaCl 2%), so that the minimum median particle size was 4.2 nm, with good injectivity and stability. Performance studies showed that the improvement agent had low surface tension (30–35 mN/m) and interfacial tension (3–8 mN/m) as well as significantly reduced the rock wetting angle (50–84°) and enhanced wettability. In addition, it had good temperature resistance, shear resistance, and acid-alkali resistance, making it suitable for complex environments in low-permeability reservoirs. Full article
(This article belongs to the Special Issue Circular Economy on Production Processes and Systems Engineering)
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13 pages, 530 KiB  
Article
Synthesis of Natural Carboxylic Acids and Alcohols from Cinnamon cassia Oil via Green Chemistry
by Gökhan Özokan, Abdulkerim Bilginer and Mustafa Kemal Gümüş
Processes 2025, 13(7), 2002; https://doi.org/10.3390/pr13072002 - 24 Jun 2025
Viewed by 679
Abstract
Benzoic acid and benzyl alcohol are the most used raw materials in cosmetics and pharmaceutical industries as preservative ingredients. Cinnamon cassia oil is an important natural starting material to synthesize organic compounds because it contains a high amount of cinnamaldehyde and benzaldehyde. Thanks [...] Read more.
Benzoic acid and benzyl alcohol are the most used raw materials in cosmetics and pharmaceutical industries as preservative ingredients. Cinnamon cassia oil is an important natural starting material to synthesize organic compounds because it contains a high amount of cinnamaldehyde and benzaldehyde. Thanks to green chemistry techniques using mild solvents such as water and ethanol, as well as low-cost and safe reagents such as potassium permanganate, and sodium borohydride, this natural starting material was used to synthesize high yields of benzoic acid, benzyl alcohol, cinnamyl alcohol, phenylpropanol, and cinnamic acid; these products are used in cosmetics, pharmaceutical, and food industries. Various reaction conditions were applied to find convenient green chemistry procedures. Equivalents (molar) of catalysts to starting materials were optimized. The highest yields (60–90%) were achieved using water as a solvent, potassium permanganate as an oxidation catalyst, and sodium borohydride as a reduction catalyst. Water was used as a solvent in all reactions except phenylpropanol. The uses of a single natural starting material, water as a solvent, and mild reagents to synthesize five important organic compounds are all in line with green chemistry techniques. Full article
(This article belongs to the Special Issue Circular Economy on Production Processes and Systems Engineering)
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24 pages, 7889 KiB  
Article
Machine Learning-Driven Multi-Objective Optimization of Enzyme Combinations for Plastic Degradation: An Ensemble Framework Integrating Sequence Features and Network Topology
by Ömer Akgüller and Mehmet Ali Balcı
Processes 2025, 13(6), 1936; https://doi.org/10.3390/pr13061936 - 19 Jun 2025
Viewed by 500
Abstract
Plastic waste accumulation presents critical environmental challenges demanding innovative circular economy solutions. This study developed a comprehensive machine learning framework to systematically identify optimal enzyme combinations for polyester depolymerization. We integrated kinetic parameters from the BRENDA database with sequence-derived features and network topology [...] Read more.
Plastic waste accumulation presents critical environmental challenges demanding innovative circular economy solutions. This study developed a comprehensive machine learning framework to systematically identify optimal enzyme combinations for polyester depolymerization. We integrated kinetic parameters from the BRENDA database with sequence-derived features and network topology metrics to train ensemble classifiers predicting enzyme-substrate relationships. A multi-objective optimization algorithm evaluated enzyme combinations across four criteria: prediction confidence, substrate coverage, operational compatibility, and functional diversity. The ensemble classifier achieved 86.3% accuracy across six polymer families, significantly outperforming individual models. Network analysis revealed a modular organization with hub enzymes exhibiting broad substrate specificity. Multi-objective optimization identified 156 Pareto-optimal enzyme combinations, with top-ranked pairs achieving composite scores exceeding 0.89. The Cutinase–PETase combination demonstrated exceptional complementarity (score: 0.875±0.008), combining complete substrate coverage with high catalytic efficiency. Validation against experimental benchmarks confirmed enhanced depolymerization rates for recommended enzyme cocktails. This framework provides a systematic approach for enzyme prioritization in plastic valorization, advancing biological recycling technologies through data-driven biocatalyst selection while identifying key economic barriers requiring technological innovation. Full article
(This article belongs to the Special Issue Circular Economy on Production Processes and Systems Engineering)
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18 pages, 1628 KiB  
Article
A More Environmentally Friendly Method for Pulp Processing Using DES-like Mixtures: Comparison of Physical Properties with Oxygen Bleached Pulp
by Lota Chrvalová, Veronika Jančíková, Ida Skotnicová, Michal Jablonský and Štefan Šutý
Processes 2025, 13(6), 1930; https://doi.org/10.3390/pr13061930 - 18 Jun 2025
Viewed by 410
Abstract
The traditional papermaking process uses petroleum-based additives, which raise environmental concerns. As a result, these concerns have attracted the scientific community to explore green additives by introducing environmentally friendly cellulose modifications as additives to the papermaking process. A promising way to process pulp [...] Read more.
The traditional papermaking process uses petroleum-based additives, which raise environmental concerns. As a result, these concerns have attracted the scientific community to explore green additives by introducing environmentally friendly cellulose modifications as additives to the papermaking process. A promising way to process pulp is the application of deep eutectic solvent-like mixtures, which expand new possibilities for delignification processes. This article aims to characterize the physical properties of pulps modified with deep eutectic solvent-like mixtures and to compare these properties to untreated softwood kraft pulp and pulp obtained after oxygen delignification (commercially available pulp; obtained from Mondi Štětí a.s.). The physical properties (mechanical and optical) of the original pulp and delignified pulps were evaluated based on the degree of beating (Schopper–Riegler degree), zeta potential, water retention value, tensile strength, modulus of elasticity, and whiteness. Technology employing deep eutectic solvent-like mixtures shows great promise for sustainable pulp production; however, its full-scale adoption will require further research focused on process optimization, solvent recovery, and economic cost reduction. Full article
(This article belongs to the Special Issue Circular Economy on Production Processes and Systems Engineering)
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17 pages, 3339 KiB  
Article
Case Study: Component Design for Streamlining the Manufacturing Process Using 3D Printing
by Jozef Trojan, Peter Trebuňa, Jozef Svetlík and Ján Kopec
Processes 2025, 13(5), 1282; https://doi.org/10.3390/pr13051282 - 23 Apr 2025
Viewed by 514
Abstract
The innovative pressure device, developed to address contamination issues on Essity Slovakia’s carton production line, was successfully implemented using 3D printing technology. This approach resulted in a precise prototype that significantly reduces contamination, simplifies packaging procedures, and lessens the need for manual labor. [...] Read more.
The innovative pressure device, developed to address contamination issues on Essity Slovakia’s carton production line, was successfully implemented using 3D printing technology. This approach resulted in a precise prototype that significantly reduces contamination, simplifies packaging procedures, and lessens the need for manual labor. The project entailed a comprehensive review of the current system, 3D scanning, creation of a model using SolidWorks software, and fabrication with a Trilab DeltiQ 2 printer. The outcomes demonstrate a staggering 96% decrease in contamination, elimination of downtime, and a boost in overall line efficiency. This research underscores the transformative capabilities of additive manufacturing in industrial modernization and accentuates the significance of technological advancements in enhancing efficiency, sustainability, and quality within the manufacturing industry. Full article
(This article belongs to the Special Issue Circular Economy on Production Processes and Systems Engineering)
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19 pages, 4419 KiB  
Article
Development and Characterization of Environmentally Responsive Thickening Agents for Fracturing Fluids in Shale Gas Reservoir Stimulation
by Cheng Huang, Liping Mu and Xuefeng Gong
Processes 2025, 13(4), 1253; https://doi.org/10.3390/pr13041253 - 21 Apr 2025
Cited by 1 | Viewed by 543
Abstract
In response to the special requirements for shale gas reservoir stimulation, a novel environmentally responsive fracturing fluid thickener was designed and developed in this paper. N,N-dimethylhexadecylallylammonium chloride (C16DMAAC), N-vinylpyrrolidone (NVP), 2-acrylamido-2-methylpropanesulfonic acid (AMPS), and Acrylamide (AM) were used as functional monomers, and the [...] Read more.
In response to the special requirements for shale gas reservoir stimulation, a novel environmentally responsive fracturing fluid thickener was designed and developed in this paper. N,N-dimethylhexadecylallylammonium chloride (C16DMAAC), N-vinylpyrrolidone (NVP), 2-acrylamido-2-methylpropanesulfonic acid (AMPS), and Acrylamide (AM) were used as functional monomers, and the synthesis of the target product was achieved successfully through free radical polymerization in an aqueous solution. The findings indicated that in the optimized situation, where the total monomer mass fraction was 25%, the ratio of AM:AMPS:C16DMAAC:NVP was 15:10:3:2, the initiator mass fraction was 0.3%, the pH was 6.5, and the temperature was 60 °C, the thickener achieved a number-average molecular weight of 1.13 × 106. Furthermore, its remarkable thermal stability was manifested, as it only experienced a 15% mass loss in the temperature interval spanning from 40 °C to 260 °C. Performance evaluation results indicated that, at 120 °C, the viscosity of the thickener under study increased by over 49% compared to the control group. Simultaneously, in a 0.4 wt% CaCl2 environment, it retained a high viscosity of 54.75 mPa·s. This value was 46.61 mPa·s greater than that of the control group. Furthermore, under the conditions of a temperature of 170 °C, the fracturing fluid viscosity remained above 68 mPa·s. Regarding the flow performance, within the flow rate range from 110 to 150 L/min, it showed a remarkable drag reduction effect, achieving a maximum drag reduction rate of 70%. At 150 °C, the fracturing fluid exhibited superior proppant-carrying efficacy, with a settlement rate that was 26.1% lower than that of the control group. The viscosity and residue content of the gel-broken fracturing fluid exceeded the requirements of industry standards. In particular, the residue content of this fracturing fluid was 21% lower than that of the control group. The research results provide an environmentally responsive fracturing fluid thickener with excellent performance for shale gas reservoir stimulation. Full article
(This article belongs to the Special Issue Circular Economy on Production Processes and Systems Engineering)
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14 pages, 4119 KiB  
Article
The Development of an Alginate Drilling Fluid Treatment Agent for Shale and a Study on the Mechanism of Wellbore Stability Sealing
by Cheng Huang, Liping Mu and Xuefeng Gong
Processes 2025, 13(4), 1250; https://doi.org/10.3390/pr13041250 - 21 Apr 2025
Viewed by 531
Abstract
In order to prevent and control the problem of wellbore instability during the drilling process in shale formations, this study, based on the unique rheological properties, water solubility, and thermal stability of sodium alginate (SA), systematically investigated the rheological properties, filtration properties, and [...] Read more.
In order to prevent and control the problem of wellbore instability during the drilling process in shale formations, this study, based on the unique rheological properties, water solubility, and thermal stability of sodium alginate (SA), systematically investigated the rheological properties, filtration properties, and temperature resistance of sodium alginate-based drilling fluids before and after salt contamination. Additionally, it explored the wellbore stability and plugging mechanism of these drilling fluids in shale formations. The research shows that the BF + 0.4 wt% SA system significantly improves the rheological properties of the drilling fluid, effectively reduces the filtration loss, and exhibits good stability under the conditions of salt contamination and a high temperature of 100 °C. Sodium alginate binds to clay particles through hydrogen bonds and ionic bonds, enhancing the hydration and dispersion ability of the particles. The absolute value of its zeta potential reaches 39 mV and 37 mV before and after salt contamination, respectively, which is better than that of the control group, thus improving the colloidal stability of the drilling fluid. At the same time, through the moderate flocculation of clay particles, low-permeability filter cakes with filtration losses of 14 mL and 25 mL before and after salt contamination are formed, realizing a wellbore stability mechanism that combines physical plugging and chemical inhibition. Full article
(This article belongs to the Special Issue Circular Economy on Production Processes and Systems Engineering)
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18 pages, 1903 KiB  
Article
Thermal Parameters Optimization of the R744/R134a Cascade Refrigeration Cycle Using Taguchi and ANOVA Methods
by Thanhtrung Dang, Hoangtuan Nguyen and Hung-Son Dang
Processes 2025, 13(4), 1210; https://doi.org/10.3390/pr13041210 - 16 Apr 2025
Viewed by 612
Abstract
In recent years, the use of R744 natural refrigerant has become increasingly popular in a wide range of applications from air conditioning to low-temperature refrigeration. This study focuses on optimizing the thermodynamic parameters of the R744/R134a cascade cycle operating under evaporative temperature varying [...] Read more.
In recent years, the use of R744 natural refrigerant has become increasingly popular in a wide range of applications from air conditioning to low-temperature refrigeration. This study focuses on optimizing the thermodynamic parameters of the R744/R134a cascade cycle operating under evaporative temperature varying from −23 °C to −29 °C, operating in tropical climates region. The parameters include the evaporating temperature, the condensing temperature, the subcooling temperature, and the superheating temperature in the low temperature cycle, and the evaporating temperature, the subcooling temperature, and the superheating temperature in the high temperature cycle. The study has given a rating of the influence of thermodynamic parameters on the coefficient of performance (COP) of the system. In addition, the study shows that the optimal dataset for all the above thermodynamic parameters is A3B3C2D1E1F3 with a COP of 2.560 in theory and 2.461 in experiment. Moreover, the ANOVA analysis method for the variances also shows the consistency of the above results with the highest error of 3.54% compared to the experiment. Full article
(This article belongs to the Special Issue Circular Economy on Production Processes and Systems Engineering)
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