Economic Principles Research Articles

B-OK: a visual and tactile tool for improving HIV mental models in a United States urban center.

Lack of adherence to antiretroviral therapy (ART) and poor retention in care are significant barriers to ending HIV epidemics. Treatment adherence support effectiveness may be constrained by limited understanding of the benefits of ART. We evaluated a visual and tactile tool, the B-OK Bottles ("B-OK"), that incorporates human-centered design and behavioral economics principles and is designed to change and strengthen mental models about HIV. We enrolled 118 adults living with HIV who were clients of medical case managers in Philadelphia. All participants completed a pre-intervention survey, a B-OK intervention and a post-intervention survey. A subset (N = 52) completed qualitative interviews. Co-primary outcomes were differences pre- to post-intervention for 11 questions about HIV awareness, knowledge, attitudes, intentions and perception. Qualitative interviews were assessed using an integrated analysis approach. Participants had a median age of 55 years (IQR 47-60), 65% were male sex (N = 77), and 72% identified as non-Hispanic Black (N = 85). B-OK was associated with improved awareness and understanding of HIV terminology, changes in HIV treatment attitudes, and increased intention to rely on HIV treatment for transmission prevention. Qualitative interview results aligned with the quantitative findings. These findings provide a strong rationale to further evaluate the potential for B-OK to improve HIV treatment adherence support.

Cost-Benefit Analysis of Enzymatic Hydrolysis Alternatives for Food Waste Management

In this study, we aimed to evaluate the economic, environmental, and social viability of the enzymatic hydrolysis process for food waste valorization by applying cost-benefit analysi (CBA). Our research was based on the investigation of three scenarios/alternatives for the final product of the enzymatic hydrolysis process and the production of bioethanol, bioactive peptides, and organic acids. Key economic indicators, such as cost/benefit ratios, net present value (NPV), and internal rate of return (IRR), were used to evaluate financial performance. At the end of the CBA, a sensitivity analysis was conducted to highlight the performance of each scenario under varying conditions, including fluctuating costs, benefits, and discount rates. These results indicate that enzymatic hydrolysis offers a significant opportunity for reducing food waste and its environmental impacts and promotes sustainability. Bioactive peptide production was found to be the most environmentally viable option, offering the highest cost-benefit efficiency. In both the optimistic and pessimistic scenarios of the sensitivity analysis, the results revealed that bioactive peptide production is economically viable, while the other alternatives, such as bioethanol and organic acid production, are more sensitive to economic and operational changes. This study revealed that enzymatic hydrolysis, as evaluated through CBA, offers a viable and impactful method for food waste management. It reduces environmental impacts, enhances sustainability, and aligns with the principles of a circular economy. The adoption of such innovative waste management strategies is considered essential for building a more sustainable and resource-efficient food system.

PLC-Controlled Intelligent Conveyor System with AI-Enhanced Vision for Efficient Waste Sorting

Current waste sorting mechanisms, particularly those relying on manual processes, semi-automated systems, or technologies without Artificial Intelligence (AI) integration, are hindered by inefficiencies, inaccuracies, and limited scalability, reducing their effectiveness in meeting growing waste management demands. This study introduces a prototype waste sorting machine that integrates an AI-driven vision system with a Programmable Logic Controller (PLC) for high-accuracy automated waste sorting. The system, powered by the YOLOv8 deep learning model, achieved sorting accuracies of 88% for metal cans, 75% for paper, and 91% for plastic bottles, with an overall precision of 90%, a recall of 80%, and a mean average precision (mAP50) of 86%. The vision system provides real-time classification, while the PLC manages conveyor and actuator operations to ensure seamless sorting. Experimental results in a controlled environment validate the system’s high accuracy, minimal processing delays, and scalability for industrial recycling applications. This innovative integration of AI vision with PLC automation enhances sorting efficiency, reduces ecological impacts, and minimizes labor dependency. Furthermore, the system aligns with sustainable waste management practices, promoting circular economy principles and advancing the Sustainable Development Goals (SDGs).

Use of Membrane Techniques for Removal and Recovery of Nutrients from Liquid Fraction of Anaerobic Digestate

This review focuses on the use of membrane techniques to recover nutrients from the liquid fraction of digestate (LFD) and emphasizes their role in promoting the principles of the circular economy. A range of membrane separation processes are examined, including microfiltration (MF), ultrafiltration (UF), nanofiltration (NF), reverse osmosis (RO), forward osmosis (FO), membrane distillation (MD) and new tools and techniques such as membrane contactors (MCs) with gas-permeable membranes (GPMs) and electrodialysis (ED). Key aspects that are analyzed include the nutrient concentration efficiency, integration with biological processes and strategies to mitigate challenges such as fouling, high energy requirements and scalability. In addition, innovative hybrid systems and pretreatment techniques are examined for their potential to improve the recovery rates and sustainability. The review also addresses the economic and technical barriers to the full-scale application of these technologies and identifies future research directions, such as improving the membrane materials and reducing the energy consumption. The comprehensive assessment of these processes highlights their contribution to sustainable nutrient management and bio-based fertilizer production.

Digital Money: Opportunities, Challenges and the Future Outlook

Purpose: This study explores the opportunities, challenges, and the future outlook of emerging digital currencies in the like of central bank digital currencies (CBDCs), cryptocurrencies, and stablecoins. The aim is to understand how these digital monetary forms are shaping the global digital currency ecosystem. Methodology: A systematic literature review of 281 studies on digital currencies, published between 2010 and 2024, was conducted. The review focused on identifying key themes such as the regulatory landscape for cryptocurrencies, privacy and anonymity concerns, and technological risks associated with digital currencies. Findings: The review unraveled several dominant themes, including increasing efforts by regulatory authorities to develop comprehensive frameworks to provide legal clarity, enhance consumer protection, and foster innovation in the digital finance sector. However, a significant gap was identified in the integration of regulatory frameworks with Behavioral Economic principles. To address this, the study proposes an integrated regulatory-behavioral framework to influence user behaviour and promote the secure and stable adoption of digital currencies. Unique Contribution to Theory, Policy and Practice: The proposed regulatory-behavioral framework offers an innovative approach to digital currency regulation by integrating insights from Behavioral Economics. This contribution highlights the need for collaborative efforts among policymakers to ensure regulations evolve in tandem with advancements in digital financial technologies. The study envisions a future where CBDCs, cryptocurrencies, and stable coins coexist, with CBDCs playing a central role in establishing a stable, accessible, and efficient digital monetary system.

Sustainability and the Circular Economy through the Eyes of Students: A Comparative Analysis among Bulgaria, North Macedonia, Slovenia and Croatia

Higher education institutions are the catalyst for building tomorrow's leaders who will take responsibility for addressing environmental issues and shaping a more sustainable future. Along with learning the principles of the circular economy and sustainability, students build the skills and knowledge needed to take up leadership positions in a variety of fields, including business, politics and non-governmental organizations. This article analyzes the understanding of issues of sustainability, circular and green economy through the eyes of business-oriented students from four European countries: Bulgaria, North Macedonia, Slovenia and Croatia. An international team of scientists researches the attitudes and expectations of students from different bachelor's and master's programs with the aim of both improving their knowledge, skills and competencies related to circular and green economy and sustainability, as well as upgrading and enriching educational programs and processes. The research identified gaps in the educational process along with identified good practices implemented by specific partner organizations. Interrelationships were sought between the final results and the current geopolitical situation of the respective country in the context of its membership or not in the European Union. The study analyzed the content of various disciplines, focusing specifically on research areas such as the circular and green economy and sustainability. The findings aim to enhance curricula in fields like corporate social responsibility, economics, marketing, and related areas. Keywords: sustainability, circular economy, green economy, education

Magnetic biochar generated from oil-mill wastewater by microwave-assisted hydrothermal treatment for sonocatalytic antibiotic degradation

The pollution risks of biomass-containing and antibiotics-containing wastewater mean that it must be treated before discharge into the environment. In a process following circular economy principles, oil-mill wastewater (OMWW) was treated in a microwave-assisted hydrothermal process and with simultaneously fabricated magnetic biochar (MBC), which was used as a catalyst for the sonocatalytic degradation of antibiotics metronidazole (MET) and ciprofloxacin (CIP) in aqueous solutions. FeCl3·6H2O, FeCl2·4H2O, and KOH were added to the OMWW, which was then treated in a SynthWave microwave reactor under either a nitrogen or air atmosphere. The UV254 and COD removal efficiencies of the OMWW reached 42.3% and 60.6%, respectively, after treatment at 250 ℃ for 3h. The MBC obtained from the OMWW treatment with air exhibited the highest adsorption and catalytic activity for antibiotics degradation. The synergistic effects of combining adsorption and sonolytic removal were in the ranges of 0.76-3.07 (MET) and 0.75-3.17 (CIP), resulting in significant degradation rate constants of pseudo-first-order kinetics (k1) that ranged from 0.010 to 0.086min-1 (MET) and from 0.018 to 0.050min-1 (CIP). Hydrophobic MET underwent faster degradation than hydrophilic CIP. The •OH is crucial for removing the model antibiotics. Initial antibiotics concentration, reaction volume, ultrasonic frequency, and power had clearer impacts on antibiotics degradation than bulk temperature. Furthermore, the possible sonocatalytic degradation pathways have also been proposed herein. The absorbents and catalysts were derived during the purification of OMWW and subsequently used for antibiotics removal from water, becoming an innovative case of circular economy and sustainable waste treatment.

Solid-state fermentation of green waste for the production of biostimulants to enhance lettuce (Lactuca sativa L.) cultivation under water stress: Closing the organic waste cycle.

Food production faces important challenges such as water scarcity and the overall need of novel sustainable strategies. This study assesses the effect of the biostimulant produced through solid-state fermentation (SSF) of green waste (wood chips and grass residues) inoculated with Trichoderma harzianum with and without l-tryptophan as a precursor for indole-3-acetic acid (IAA) production, a well-known plant hormone. The fermented solid demonstrated significant positive effects on the growth of lettuce (Lactuca sativa L.) under different irrigation conditions. Substantial enhancements were observed in growth parameters such as fresh weight, plant height, leaf area and leaf quantity, along with chemical parameters including total phenol content, chlorophylls, carotenoids, and antioxidant activity (DPPH). The results also showed a positive impact on the nutritional quality of lettuce, particularly under normal irrigation conditions. In conclusion, this study highlights the biostimulant potential to improve the yield and nutritional quality of lettuce crops by reusing plant residues. Additionally, it poses the relevance of applying circular economy principles in sustainable agriculture and organic waste management.

Aligning Waste-to-Energy (WtE) Projects with Circular Economy Principles: A Comparative Analysis of the European Union and India's Path Forward

The growing global challenge of waste management has reached alarming levels, with approximately 4.5 million tonnes of waste generated every day worldwide—a figure that is expected to exceed 8 million tonnes by 2050, according to the World Bank. Although there have been notable improvements in how waste is managed, it has transitioned from being just a public concern to becoming a booming industry, particularly seen in the rise of the Waste-to-Energy (WtE) sector across the globe. Given this growing problem, many experts agree that addressing waste requires a shift toward a "circular economy," an approach aimed at minimizing waste altogether. This strategy is in line with the United Nations' 2030 Agenda for Sustainable Development, particularly Sustainable Development Goal 12, which focuses on responsible consumption and production. While WtE technologies seem like a sustainable option, the process of turning waste into energy using advanced facilities raises questions about their true compatibility with circular economy principles. The UN has proposed a framework to guide WtE projects, suggesting that these frameworks can help in the transition to a circular economy—especially in terms of energy recovery. However, this requires innovative public-private partnerships (PPPs) that emphasize people-first values and the adoption of best practices by both governments and the private sector simultaneously. The main focus of this paper is to highlight the need to align WtE projects with circular economy principles to ensure sustainable and effective waste management. While this model has made significant progress in EU ( European Union) countries, it is still in the early stages of development in India. This paper explores the framework used in the EU and discusses how India can successfully adopt and implement similar practices.

Development Strategies for the Mediterranean Coastal Landscape: Adaptive Decision-Making Processes for Implementing the Circular Economy in the Redevelopment of the Reggio Calabria Waterfront

This document explores a circular approach to the redevelopment of the city–port system of Reggio Calabria, an area characterized by complex challenges involving economic, social, and environmental needs. By developing a multidimensional decision-making process, three development scenarios were identified to support a sustainable transition. The methodology integrates both quantitative and qualitative assessments, actively involving the local community and stakeholders. The proposed methodology operationalizes the principles of the circular economy by aligning sustainable regeneration scenarios with local needs and environmental constraints. The integrated assessment ensures the applicability of circular models for the resilient redevelopment of the waterfront. The results demonstrate how this model can be applied to other Mediterranean port cities to promote sustainable and resilient regeneration.

Wheat dust and extracted rapeseed scrap biochar: a comprehensive characterization and assessment of potential utilization in the context of the circular economy

Abstract The current utilization of wheat dust (WD) and hexane-extracted rapeseed scrap (RS) in Central Europe is inefficient and non-ecological. Therefore, it is necessary to identify an appropriate waste treatment that supports the principles of the circular economy. For this reason, the aforementioned wastes were pyrolyzed, resulting in the production of biochars, which are commonly used as absorbents or soil amendments. These biochars were then steam activated, characterized, and evaluated for potential further suitable and sustainable utilization. The structure, porosity, specific surface area, and composition of bound functional groups, nutrients, toxic elements, cation exchange capacity (CEC), and pH were analyzed as important parameters for biochar applications. RS biochar contained high concentrations of nutrients (N 75.9, P 21.5, K 15.1, C 603, Ca 14.3, Mg 8.31, S 5.40 g·kg−1 wt. all). The CEC was remarkably high 87.0 cmol·kg−1 for the RS biochar. The SSA value increased in fivefold in both samples upon activation (11.0 m2·g−1 for WD biochar and 0.8 m2·g−1 for RS biochar). The pore depth increased in accordance with activation temperature. Alkanes, aromatics, and oxygenated groups were detected on the biochars surfaces, yet more evident in WD. WD biochar could be used as an adsorbent for organic pollutants because its structure, surface area, and representation of functional group predict high adsorption efficiency, especially after activation. Raw RS biochar is more suited to utilization as a soil amendment, due to its high concentration of nutrients. These utilizations of biochar support the circular economy, eliminate pollution, improve soil properties, and reduce the need for industrially produced fertilizers and sorbents. Graphical abstract

Recovery of antioxidant compounds from wine lees using membrane technologies

Considering the substantial volume available and the high concentration of antioxidant compounds in wine lees composition, the present work investigated the use of this winemaking by-product as a raw material for the recovery of anthocyanins and other phenolic compounds. This study explores a process that includes an aqueous extraction step of the antioxidant substances from wine lees, followed by microfiltration to remove suspended material, and a nanofiltration step, resulting in a concentrate rich in anthocyanins and other phenolic compounds. The final product consists of an extract concentrated in natural antioxidant compounds with high antioxidant activity and presenting potential to be used in formulations of pharmaceutical, cosmetic and food industries. The process presented is grounded on sustainability, using eco-friendly solvents and clean technologies, aligning with the principles of circular economy and adding value to wine industry by-products.

Advanced methanotrophic bioreactor design for efficient bioremediation of hydrogen sulfide (H₂S) And Volatile Organic Compounds (Vocs): Integrating genetic engineering and industrial scalability

The convergence of advanced microbial biotechnology and metabolic engineering has facilitated groundbreaking advancements in bioremediation. This study presents the engineered Methylomicrobium buryatense strain 5GB1C-RO1, optimized for the simultaneous removal of hydrogen sulfide (H₂S) and volatile organic compounds (VOCs) within a two-stage methanotrophic bioreactor system. Through precise CRISPR/Cas9-mediated genome editing, critical metabolic pathways for sulfide oxidation (SQR, FCCAB, SOXABXYZ) and VOC degradation (alkB, adhP, todC1C2BA) were integrated, achieving catalytic efficiencies exceeding 3.2 × 10⁷ M⁻¹s⁻¹ and substrate conversion rates above 450 nmol min⁻¹ mg⁻¹ protein. The strain demonstrates exceptional robustness under industrial conditions, maintaining 95% pollutant removal efficiency at H₂S concentrations up to 1000 ppm and VOC concentrations exceeding 500 ppm. The innovative bioreactor system incorporates enhanced gas-liquid mass transfer mechanisms, achieving mass transfer coefficients (kLa) exceeding 300 h⁻¹ and enabling stable operation for over 1000 continuous hours. Experimental results confirm the system's capacity for pollutant mineralization, generating methane-rich biogas (>95% CH₄) and high-protein microbial biomass (>85%), which are valuable for energy and agricultural applications. This integrated bioremediation approach not only reduces reliance on chemical scrubbing and flaring but also supports circular economy principles by transforming waste gases into renewable resources. The technology provides a scalable, sustainable, and cost-effective solution to mitigate industrial emissions while addressing environmental and regulatory challenges. The findings highlight the potential of combining advanced genetic engineering with innovative bioreactor design to redefine industrial pollutant management and resource recovery.

Supply chain management: Balancing efficiency and environmental responsibility

Supply chain management (SCM) is a cornerstone of global commerce, driving efficiency and cost-effectiveness in production and distribution networks. However, the rising urgency of environmental sustainability has placed traditional SCM practices under scrutiny, as their reliance on linear models often leads to resource depletion, carbon emissions, and waste generation. Balancing efficiency with environmental responsibility requires a paradigm shift toward sustainable supply chain practices that integrate economic, social, and ecological goals. This approach emphasizes optimizing resource utilization, minimizing waste, and reducing the environmental footprint without compromising operational efficiency. This article explores the multifaceted challenges and opportunities of aligning supply chain efficiency with sustainability. It examines key practices such as green procurement, waste reduction, and the adoption of circular economy principles that promote recycling, reuse, and resource regeneration. The role of technology, including artificial intelligence, blockchain, and IoT, in enhancing supply chain transparency and efficiency is also discussed. Additionally, the article highlights the importance of collaboration among stakeholders—suppliers, manufacturers, policymakers, and consumers—in fostering sustainable supply chains. Global examples and case studies from industries such as manufacturing, retail, and agriculture illustrate the feasibility and benefits of sustainable SCM. Metrics for assessing success, barriers to scaling sustainable practices, and future directions for innovation and policy are examined. By integrating efficiency with environmental responsibility, sustainable supply chain management emerges as a vital strategy for achieving long-term economic resilience and environmental stewardship.

Strategies for the Transformation of Waste Cooking Oils into High-Value Products: A Critical Review

Waste cooking oils (WCOs) are generated globally from households, the hospitality industry, and other sectors. Presently, WCOs are mainly employed as feedstock for biodiesel and energy production, strongly depending on the availability of WCOs, which are often imported from other countries. The objective of this review is to give an overall comprehensive panorama of the impacts, regulations, and restrictions affecting WCOs, and their possible uses for producing high-value products, such as bio lubricants, bio surfactants, polymer additives, road and construction additives, and bio solvents. Interestingly, many reviews are reported in the literature that address the use of WCOs, but a comprehensive review of the topic is missing. Published studies, industry reports, and regulatory documents were examined to identify trends, challenges, production statistics, environmental impacts, current regulations, and uses for high-value polymer production. The data collected show that WCOs hold immense potential as renewable resources for sustainable industrial applications that are in line with global carbon neutrality goals and circular economy principles. However, achieving this shift requires addressing regulatory gaps, enhancing collection systems, and optimizing conversion technologies. This comprehensive review underlines the need for collaborative efforts among policymakers, industry stakeholders, and researchers to maximize the potential of WCOs and contribute to sustainable development.

A Circular Design Concept for Implementing Sustainable Building Practices in the KREIS-Haus Living Lab, Switzerland

The KREIS-Haus, an inhabited living lab in Switzerland, serves as a demonstrator of the implementation of sustainable and circular building practices. Addressing the environmental impacts associated with construction, operation, and deconstruction, this study presents an innovative systematic design concept that synthesizes principles of the circular economy, Cradle-to-Cradle design, and ecological engineering. The design process was applied to the KREIS-Haus as a lighthouse project, combining theoretical frameworks with real-word application to derive actionable insights. The novelty of the KREIS-Haus lies in the holistic integration of circular and sustainable concepts within a compact footprint, realized in a real-life, publicly accessible living lab. Its design maximizes resource efficiency by incorporating locally sourced materials, modular construction techniques, and flexible interior features, which allow for easy disassembly and reuse. At the heart of its circular design is the multifunctional conservatory, which provides heat and sound insulation, generates solar power, and expands the living space. Additionally, it supports plant cultivation and enables the reuse of treated wastewater and nutrients, as part of the off-grid water and nutrient management system to reduce reliance on external resources. The principles of solar architecture further minimize the building’s energy demands. Key insights from the design and construction process highlight the challenges of navigating conflicting goals, the importance of partner alignment, and considerations for scaling these concepts to larger developments. While technical challenges may arise, addressing systemic barriers will be essential for advancing sustainable and circular building practices on a broader scale.

Sludge Management: Integrating the Principle of Circular Economy into the Concept of Sustainability

Sludge Management: Integrating the Principle of Circular Economy into the Concept of Sustainability

Assessing Urban Agriculture’s Potential for Biodiversity Conservation, Carbon Sequestration, and Community Development: A Comparative Study of Residents’ Perceptions in Three Western Romanian Cities

Urban agriculture is increasingly recognized as a strategy for enhancing sustainability and well-being in urban areas, mainly through circular economy principles. This study investigates residents’ perspectives from three major cities in western Romania—Arad, Timișoara, and Oradea—on the implementation and benefits of urban agriculture. The main goal was to identify differences in opinions regarding urban agriculture’s potential to improve biodiversity conservation, enhance carbon dioxide retention, and reduce synthetic compound usage. The research also explored community development through circular economy practices and tools local authorities could use to promote urban agriculture. A survey of 573 respondents utilized variance analysis and the Tukey test to reveal significant opinion differences among residents. The findings showed notable variations in views on biodiversity conservation and community development benefits but no significant differences in opinions on carbon dioxide capture or synthetic chemical use. Residents of Timișoara and Oradea expressed more favorable views on urban agriculture than those in Arad. Participants emphasized the importance of free land allocation and sustainable practices for successful urban agriculture implementation. This study offers valuable insights for policymakers and contributes to the understanding of urban sustainability and the role of urban agriculture in supporting circular economy principles.

Pemberdayaan masyarakat melalui kewirausahaan dan Green ECONOMY Desa Manunggal Kecamatan Labuhan Deli Kab. Deli Serdang

The objective of the community service program is to empower the community of Manunggal Village, Labuhan Deli Sub-district, Deli Serdang Regency, through the promotion of a green economy-based entrepreneurship model. The program is designed to enhance community welfare by fostering the concept of environmentally sound entrepreneurship and promoting sustainable local economic development. The program is designed to equip entrepreneurs with the necessary skills and knowledge to incorporate green economy principles into their business practices. These principles encompass a wide range of practices, including waste management, organic crop cultivation, and the use of renewable energy sources.The program is structured to facilitate the development of practical business proposals, the creation of basic financial reports, and the integration of technology into business management.It is anticipated that the implementation of these activities will have a multifaceted impact on the community of Manunggal Village. Specifically, it is expected to enhance the community's capacity to manage sustainable independent businesses, increase income, and reduce unemployment. The program is designed to foster collective awareness regarding the significance of environmental protection through the implementation of responsible business practices.The implementation method of this service activity consists of presentations, lectures with question and answer sessions, and hands-on exercises.The final stage involves an evaluation phase, during which participants receive training on drafting practical business proposals.Following the conclusion of the service activity, a follow-up interview session was conducted to obtain feedback and evaluate the impact of the activity's implementation.

Waste to Energy Conversion and Predictive maintenance in Circular Economics Through AI

This paper explores the transformative role of artificial intelligence (AI) in advancing the circular economy through waste-to-energy (WtE) conversion and predictive maintenance. By leveraging AI, waste management processes can be optimized to enhance the efficiency of resource recovery, minimize environmental impact, and generate renewable energy. Predictive maintenance, driven by AI, ensures the smooth operation of industrial equipment, reducing downtime and extending machinery lifespan. This integration supports sustainable production and aligns with important circular economy principles, including biomimicry, lean manufacturing, and the Butterfly Model. The study underscores the potential of AI-driven technologies in fostering a resilient and sustainable future by addressing critical environmental challenges and promoting efficient resource utilization.