Cigarette butts (CBs) are among the most abundant forms of anthropogenic litter worldwide and constitute a persistent source of environmental contamination due to their slow degradation and the release of toxic substances into terrestrial and aquatic ecosystems. This review critically evaluates recent advances in the valorisation of CB waste into value-added functional materials. Particular attention is given to conversion strategies including chemical activation, electrospinning, hydrothermal processing, and nanocomposite fabrication. These approaches enable the production of activated carbons, cellulose-derived nanomaterials, and metal-doped composites with promising applications in water purification, energy storage, vector control, and pollutant remediation. The underlying mechanisms, performance, scalability, and sustainability of these technologies are discussed. Finally, current challenges, research gaps, and future opportunities of large-scale implementation are highlighted. Collectively, the findings demonstrate that CBs can be re-envisioned not only as a persistent environmental pollutant but also as valuable secondary resources that support circular economy and sustainable material development strategies.

The greatest obstacle to recycling post-consumer high-density polyethylene (PCR-HDPE) is typically the degradation of properties caused by impurities and heterogeneity. However, a critical analysis of the literature reveals that the real bottleneck is not the material composition, but rather rheological stability, which simultaneously determines the degradation history of the waste stream, melt behavior, and processability at the cycle level. This review proposes a new perspective: the decision among mechanical, chemical, and energetic recycling is better made based on a unified rheological stability index (RSI), which integrates carbonyl index, viscosity change after multiple instances of melting, melt flow index (MFI) instability, in-mold pressure fluctuation, and the degree of polymer incompatibility. RSI enables the prediction of the processability of PCR-HDPE and identifies which recycling path a fraction is most suitable for. The study demonstrates how an RSI-based approach can reduce quality risk, improve cycle stability, and support circular decision-making in an industrial environment.

Waste rubber management through developing blends of thermoplastics with ground tire rubber (GTR) has gained significant attention for creating sustainable, high-performance materials with enhanced properties. In this work, we developed customized graphene/polymer nanocomposites applying GTR, ethylene-vinyl acetate copolymer (EVA), and graphene nanoplatelets (GNPs), taking carbon black (CB) as the reference additive. A wide range of electrical conductivity from 10^–12 S/cm (dielectric) to 10^–5 S/cm (semiconductor) was obtained for optimized composites containing GNPs and CB, respectively. Thermal, mechanical, and flame-retardant properties looked promising for additive manufacturing, while electrical conductivity was tailored for soft electronics. In view of processability, mechanical strength, and elasticity, GNPs-incorporated EVA/GTR composites showed an edge over their CB-aided counterparts. For example, tensile strength and elongation at break of EVA/GTR blends reinforced with 20 phr GNPs were 4.8 MPa and 681%, respectively, compared to 4.0 MPa and 651% for the composite comprising an identical amount of CB. Interestingly, combining GNPs and CB enhanced the thermal stability and flame retardancy of EVA/GTR compared to only GNPs or CB. These results were promising from both sustainability and advanced functional materials perspectives.

This is an editorial article. It has no abstract.