Recycling | Issue Cover Collection Published in 2025
The articles listed below have been selected as the cover articles for Issues 1–6 of Volume 10 by the Editorial Office of Recycling (ISSN: 2313-4321). These articles represent the latest research advancements in fields within the journal's scope, and we hope they will serve as a source of new research ideas for scholars and authors in these fields. For full access to Volume 14, please visit https://www.mdpi.com/2313-4321/10.
1. “Polymer Recycling: A Comprehensive Overview and Future Outlook”
by Paul van den Tempel and Francesco Picchioni
Recycling 2025, 10(1), 1; https://doi.org/10.3390/recycling10010001
Available online: https://www.mdpi.com/2313-4321/10/1/1
Cover Story: Polymer recycling is an essential topic to consider in our sustainability-driven society. In this work, we focus on the most common commodities, with the most important (in terms of production volume) being thermoplastics, rubbers, and thermosets. We review the common separation methods and the different recycling strategies. We also discuss the design of novel materials, at the molecular level, which will allow for easier recycling in the future. Generally, we conclude that research in this field is, in its nature, fragmented, with defined expertise often focusing on a specific kind of waste, application field, or technology. In contrast to this, the need for a multidisciplinary and integrative approach, including economic, environmental, and sustainability analyses, is a logical consequence of the overview presented in this work.
2. “Recycling or Sustainability: The Road of Electric Vehicles Toward Sustainable Economy via Blockchain”
by Katarina Dimic-Misic, Shailesh Singh Chouhan, Vesna Spasojević Brkić, Milica Marceta-Kaninski and Michael Gasik
Recycling 2025, 10(2), 48; https://doi.org/10.3390/recycling10020048
Available online: https://www.mdpi.com/2313-4321/10/2/48
Cover Story: Electric vehicles are the transportation of tomorrow, and it is vital that they become a reality in modern society. To ensure sustainable use of this technology, we must prioritize recycling and circularity. Recycling EV components reduces waste, conserves resources, and supports the ongoing development of green innovations. For true sustainability, the entire EV lifecycle must align with eco-friendly practices. Blockchain technology can further enhance this by providing transparent, traceable systems for materials, ensuring accountability and improving circularity in the EV supply chain, making the transition greener and smarter.
3. “Rethinking PE-HD Bottle Recycling—Impacts of Reducing Design Variety”
by Lorenz P. Bichler, Thomas Koch, Nina Krempl and Vasiliki-Maria Archodoulaki
Recycling 2025, 10(3), 93; https://doi.org/10.3390/recycling10030093
Available online: https://www.mdpi.com/2313-4321/10/3/93
Cover Story: Sorting remains one of the most challenging tasks in the current state of mechanical recycling due to the significant variety of packaging types, in addition to design choices that inhibit efficient separation. Such challenges lead to cross-contamination—primarily with polypropylene—in sorted post-consumer PE-HD plastic fractions and limit the material’s scope of application. As PE-HD is frequently used in extrusion blow-moulded bottles, herein, we investigate whether reducing their design versatility could improve the properties of the corresponding regranulates.
4. “Organic Waste and Wastewater Sludge to Volatile Fatty Acids and Biomethane: A Semi-Continuous Biorefinery Approach”
by Paolo S. Calabrò, Domenica Pangallo, Mariastella Ferreri, Altea Pedullà and Demetrio A. Zema
Recycling 2025, 10(4), 125; https://doi.org/10.3390/recycling10040125
Available online: https://www.mdpi.com/2313-4321/10/4/125
Cover Story: This paper presents a biorefinery-based approach to recover volatile fatty acids and biomethane from the co-fermentation of excess sludge and the organic fraction of municipal solid waste. Semi-continuous experiments demonstrated the influence of substrate ratio and hydraulic retention time on the acid yield, while traditional direct anaerobic digestion of the fermentation residues significantly enhanced methane production. The proposed process supports the transition of wastewater treatment plants into circular, energy-positive facilities.
5. “Technical Evaluation and Recycling Potential of Polyolefin and Paper Separation in Mixed Waste Material Recovery Facilities”
by Anna-Maria Lipp, Dominik Blasenbauer, Hana Stipanovic, Gerald Koinig, Alexia Tischberger-Aldrian and Jakob Lederer
Recycling 2025, 10(5), 176; https://doi.org/10.3390/recycling10050176
Available online: https://www.mdpi.com/2313-4321/10/5/176
Cover Story: Mixed waste from urban areas and tourist regions contains lots of recyclable materials, including paper and polyolefins. Using the case study of Tyrol, Austria, this article evaluated the recycling potential of these materials recovered from mixed waste by two sensor-based sorting trials. The trial achieved a purity of the target fractions by up to 70%. Recovery of polyolefins could increase regional recycling rates by up to 16%, while paper recovery only adds a smaller boost. Although separating these materials slightly affected the heating values of the remaining waste, it proved technically feasible. While this improves resource efficiency and circularity, contamination and balancing recycling with energy recovery remain a challenge to be further investigated in future.
6. “Indicators Targeting the Retrieval of Polymers in EEE and Their Re-Integration into New Equipment”
by Nicolas Nève, Stéphane Pompidou, Carole Charbuillet and Nicolas Perry
Recycling 2025, 10(6), 212; https://doi.org/10.3390/recycling10060212
Available online: https://www.mdpi.com/2313-4321/10/6/212
Cover Story: This paper aims to investigate the evaluation of different “design for X” approaches. Indeed, the indicators usually used to evaluate products are based on mass criteria. This omits other very important aspects, such as the dismantlability of products and the environmental quality of materials that compose them. This hinders the retrieval of materials, and, as a result, their re-integration as secondary materials. This original work proposes additional indicators, forming two indices that aim at evaluating the circularity of materials, by taking into account more than just the mass of recovered materials. Indicators targeting the dismantlability, materials quality and supply, and recyclability of the equipment have been selected, constructed, and tested on real-life equipment.