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A Circular Economy Perspective: From Waste to Energy

A special issue of Energies (ISSN 1996-1073). This special issue belongs to the section "B: Energy and Environment".

Deadline for manuscript submissions: 15 June 2026 | Viewed by 10671

Special Issue Editors


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Guest Editor
School of Engineering, Department of Electrical and Electronics Engineering, University of West Attica, 12244 Egaleo, Greece
Interests: structural health monitoring; composite materials; renewable energy sources; energy recovery from wastes; digital manufacturing
Special Issues, Collections and Topics in MDPI journals

E-Mail Website
Guest Editor
High Voltage and Energy Systems Research Lab, Department of Electrical and Electronics Engineering, University of West Attica, 12244 Egaleo, Greece
Interests: eco design and energy efficiency; materials and energy recovery from wastes; high-voltage engineering; electrical measurements and high field effects; electromechanical installations and apparatus
Special Issues, Collections and Topics in MDPI journals

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Guest Editor
Department of Industrial Design and Production Engineering, University of West Attica, Athens, Greece
Interests: environmental technologies; production engineering; biotechnology; metal recovery; waste management; circular economy and renewable energy sources
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The scientific community recognises climate change as one of the most challenging issues of the coming decades. Governments have invested in the transition from fossil fuels to renewable energy sources as a result of this problem. According to the IPCC, one of the most significant problems that has to be addressed in order to lessen the effects of the climate catastrophe is waste. Whilst governments and organisations have varying definitions of the word, sustainable waste management is widely accepted as a solution. Waste-to-Energy (WTE) is an established and mature technology that is employed by many nations as part of the waste reduction solution and as a significant source of renewable energy.

In this regard, waste-to-energy power plants—that is, the generation of renewable energy and sustainable waste management—are a solution to all of these problems. Nonetheless, some people throughout the world continue to oppose the use of waste-to-energy as an alternative to landfilling in order to handle post-recycling garbage.

In addition to identifying future perspectives and issues linked to the global climate catastrophe, this Special Issue aims to discuss, present, and share the most recent advancements related to the current status of waste-to-energy technology. 

We encourage you to submit original research findings and review articles that highlight the benefits and drawbacks of the current technology while also providing an overview of the field's accomplishments to date. Directions for future growth can be identified through critical examination.

Dr. Konstantinos Kalkanis
Prof. Dr. Constantinos S. Psomopoulos
Dr. Kiskira Kyriaki
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 250 words) can be sent to the Editorial Office for assessment.

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. Energies is an international peer-reviewed open access semimonthly 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 2600 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

  • waste
  • recycling
  • circular economy
  • waste management
  • waste to wealth
  • life cycle analysis
  • life cycle cost analysis
  • impact assessment
  • material balances
  • waste-to-energy
  • peer review
  • environmental impact
  • biomass and biowaste
  • agricultural residues
  • biowaste valorization
  • bioenergy potential
  • energy recovery
  • conversion technologies
  • material recovery

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Published Papers (4 papers)

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Research

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20 pages, 3018 KB  
Article
Comparative LCA and Mass–Energy Evaluation of Thermal Sewage Sludge Treatment Pathways: Incineration, Gasification, Pyrolysis, and HTC
by Nikolina Poranek, Tomasz Billig, Agata Wajda, Krzysztof Pikoń, Tomasz Iluk and Ruslan Lagashkin
Energies 2026, 19(3), 815; https://doi.org/10.3390/en19030815 - 4 Feb 2026
Viewed by 785
Abstract
Sewage sludge management is a major challenge in modern wastewater treatment, as sludge contains organic matter, nutrients, pathogens, heavy metals, and emerging contaminants. Increasing wastewater volumes from urbanization and population growth have led to steadily rising global sludge production, emphasizing the need for [...] Read more.
Sewage sludge management is a major challenge in modern wastewater treatment, as sludge contains organic matter, nutrients, pathogens, heavy metals, and emerging contaminants. Increasing wastewater volumes from urbanization and population growth have led to steadily rising global sludge production, emphasizing the need for sustainable and resource-efficient treatment strategies. Conventional methods—such as landfilling, land application, and biological treatment—face limitations due to contaminant risks, regulatory restrictions, and incomplete pollutant removal. Thermal and thermochemical processes offer substantial volume reduction, energy recovery, and resource valorization. Incineration is widely implemented and ensures complete oxidation but requires high energy input and emission control. Gasification and pyrolysis produce syngas, bio-oil, and biochar, supporting circular economy applications, while hydrothermal carbonization (HTC) efficiently converts wet sludge into hydrochar without intensive drying. This study presents a comparative life cycle assessment (LCA) and mass–energy assessment of these four thermal treatment methods, highlighting their environmental impacts, energy efficiencies, and resources’ recovery potential to support more sustainable sludge management. Full article
(This article belongs to the Special Issue A Circular Economy Perspective: From Waste to Energy)
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14 pages, 1779 KB  
Article
Closing the Loop on Solar: A Sustainability Assessment of Photovoltaic Recycling in Greece
by Kyriaki Kiskira, Angeliki Lalopoulou, Konstantinos Kalkanis and George Vokas
Energies 2025, 18(23), 6314; https://doi.org/10.3390/en18236314 - 30 Nov 2025
Cited by 2 | Viewed by 841
Abstract
This paper examines the sustainability of photovoltaic (PV) panel recycling through a case study in Greece. It traces the evolution of PVs and outlines the main construction characteristics, emphasizing that although PV systems reduce greenhouse gas emissions, they also generate substantial end-of-life (EoL) [...] Read more.
This paper examines the sustainability of photovoltaic (PV) panel recycling through a case study in Greece. It traces the evolution of PVs and outlines the main construction characteristics, emphasizing that although PV systems reduce greenhouse gas emissions, they also generate substantial end-of-life (EoL) waste containing both valuable and potentially hazardous materials. The study estimates Greece’s annual PV waste generation and evaluates its environmental, social, and economic impacts. It focuses on advanced disassembly and recycling methods by PV types and calculates material-recovery rates. Using national installation data from 2009–2023, the analysis quantifies the potential mass of recoverable materials and assesses the sustainability of PV recycling in terms of environmental protection, public health, and economic feasibility. Results show high recovery rates: silicon (85%), aluminum (100%), silver (98–100%), glass (95%), copper (97%), and tin (32%). Although current recycling economics remain challenging, the environmental and health benefits are significant. This research contributes to the existing literature by providing the first detailed quantification of recoverable raw materials embedded in Greece’s PV stock and by highlighting the need for technological innovation and supportive policies to enable a circular and sustainable solar economy. Full article
(This article belongs to the Special Issue A Circular Economy Perspective: From Waste to Energy)
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Review

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47 pages, 2952 KB  
Review
Beyond Waste: Future Sustainable Insights for Integrating Complex Feedstocks into the Global Energy Mix
by Malkan Kadieva, Anton Manakhov, Maxim Orlov, Mustafa Babiker and Abdulaziz Al-Qasim
Energies 2026, 19(2), 413; https://doi.org/10.3390/en19020413 - 14 Jan 2026
Cited by 1 | Viewed by 710
Abstract
The utilization of sustainable feedstocks offers significant opportunities for innovation in sustainable and efficient processing technologies, targeting a vacuum residue upgrade industry projected to be valued at around USD 26 billion in 2024. This review examines advances in catalytic strategies for upgrading waste-derived [...] Read more.
The utilization of sustainable feedstocks offers significant opportunities for innovation in sustainable and efficient processing technologies, targeting a vacuum residue upgrade industry projected to be valued at around USD 26 billion in 2024. This review examines advances in catalytic strategies for upgrading waste-derived products (plastics, tires) and biomass, in addition to heavy oil feedstocks. Particular emphasis is placed on hydrogen addition pathways, specifically, residue hydroconversion facilitated by dispersed nanocatalysts and waste co-processing methodologies. Beyond nanoscale catalyst design and reaction performance, this work also addresses refinery-level sustainability impacts. The advanced catalytic conversion of heavy oil residue demonstrates superior conversion efficiency, significant coke suppression, and improved carbon utilization, while life cycle and illustrative techno-economic comparisons indicate greenhouse gas reductions and a net economic gain of approximately USD 2–3 per barrel relative to conventional refining under scenarios assuming decarbonized hydrogen production. Co-processing of plastics, tires, and biomass with heavy oil feedstocks is highlighted as a practical and effective approach. Together, these findings outline a rational catalytic pathway toward optimized refining systems. Within the framework of the circular carbon economy, these catalytic processes enable enhanced feedstock utilization, integration of low-carbon hydrogen, and coupling with carbon-capture technologies. Full article
(This article belongs to the Special Issue A Circular Economy Perspective: From Waste to Energy)
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37 pages, 5333 KB  
Review
The Potential of Microbial Fuel Cells as a Dual Solution for Sustainable Wastewater Treatment and Energy Generation: A Case Study
by Shajjadur Rahman Shajid, Monjur Mourshed, Md. Golam Kibria and Bahman Shabani
Energies 2025, 18(14), 3725; https://doi.org/10.3390/en18143725 - 14 Jul 2025
Cited by 15 | Viewed by 7578
Abstract
Microbial fuel cells (MFCs) are bio-electrochemical systems that harness microorganisms to convert organic pollutants in wastewater directly into electricity, offering a dual solution for sustainable wastewater treatment and renewable energy generation. This paper presents a holistic techno-economic and environmental feasibility assessment of large-scale [...] Read more.
Microbial fuel cells (MFCs) are bio-electrochemical systems that harness microorganisms to convert organic pollutants in wastewater directly into electricity, offering a dual solution for sustainable wastewater treatment and renewable energy generation. This paper presents a holistic techno-economic and environmental feasibility assessment of large-scale MFC deployment in Dhaka’s industrial zone, Bangladesh, as a relevant case study. Here, treating 100,000 cubic meters of wastewater daily would require a capital investment of approximately USD 500 million, with a total project cost ranging between USD 307.38 million and 1.711 billion, depending on system configurations. This setup has an estimated theoretical energy recovery of 478.4 MWh/day and a realistic output of 382 MWh/day, translating to a per-unit energy cost of USD 0.2–1/kWh. MFCs show great potential for treating wastewater and addressing energy challenges. However, this paper explores remaining challenges, including high capital costs, electrode and membrane inefficiencies, and scalability issues. Full article
(This article belongs to the Special Issue A Circular Economy Perspective: From Waste to Energy)
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