Plastic streams dominated by polyethylene (PE) including PE HD/MD (High Density/Medium Density) and PE LD/LLD (Low Density/Linear Low Density), polypropylene (PP), and polyvinyl chloride (PVC) across Europe demand a design framework that links synthesis with end of life reactivity, supporting circular economic goals and European Union waste management targets. This work integrates polymerization derived chain architecture and depolymerization mechanisms to guide selective valorization of commercial plastic wastes in the European context. Catalytic topologies such as Bronsted or Lewis acidity, framework aluminum siting, micro and mesoporosity, initiators, and strategies for process termination are evaluated under relevant variables including temperature, heating rate, vapor residence time, and pressure as encountered in industrial practice throughout Europe. The analysis demonstrates that polymer chain architecture constrains reaction pathways and attainable product profiles, while additives, catalyst residues, and contaminants in real waste streams can shift radical populations and observed selectivity under otherwise similar operating windows. For example, strong Bronsted acidity and shape selective micropores favor the formation of C₂ to C₄ olefins and Benzene, Toluene, and Xylene (BTX) aromatics, while weaker acidity and hierarchical porosity help preserve chain length, resulting in paraffinic oils and waxes. Increasing mesopore content shortens contact times and limits undesired secondary cracking. The use of suitable initiators lowers the energy threshold and broadens processing options, whereas diffusion management and surface passivation help reduce catalyst deactivation. In the case of PVC, continuous hydrogen chloride removal and the use of basic or redox co catalysts or ionic liquids reduce the dehydrochlorination temperature and improve fraction purity. Staged dechlorination followed by subsequent residue cracking is essential to obtain high quality output and prevent the release of harmful by products within European Union approved processes. Framing process design as a sequence that connects chain architecture, degradation chemistry, and operating windows supports mechanistically informed selection of catalysts, severity, and residence time, while recognizing that reported selectivity varies strongly with reactor configuration and feed heterogeneity and that focused comparative studies are required to validate quantitative structure to selectivity links. In European post consumer sorting chains, PS and PC are frequently handled as separate fractions or appear in residues with distinct processing routes, therefore they are not included in the polymer set analyzed here. Polystyrene and polycarbonate are outside the scope of this review because they are commonly handled as separate fractions and are typically optimized toward different product slates than the gas, oil, and wax focused pathways emphasized here.

Plastics streams dominated by polyolefins and PVC demand a design framework that links synthesis to end-of-life reactivity. This work integrates polymerization-derived microstructure with depolymerization mechanisms to guide selective valorization. We synthesize mechanistic and kinetic evidence connecting coordination and radical polymerization (linear HDPE, branched LDPE, stereoregular PP; PVC with backbone C–Cl) to degradation pathways, and evaluate catalytic topologies (Brønsted/Lewis acidity, framework Al siting, micro/mesoporosity), initiators, and termination/quench strategies under relevant process variables (temperature, heating rate, vapor residence time, pressure). The analysis shows that microstructure prescribes reaction manifolds and attainable product slates: strong Brønsted acidity and shape-selective micropores favor C₂–C₄ olefins and BTX, whereas weaker acidity and hierarchical porosity preserve chain length to paraffinic oils/waxes; mesopore enrichment shortens contact times and suppresses secondary cracking; initiators lower onset energies and expand operability; diffusion management and surface passivation mitigate deactivation. For PVC, continuous HCl removal and basic/redox co-catalysts or ionic liquids lower dehydrochlorination temperatures and yield cleaner fractions, making staged dechlorination followed by residue cracking essential. Framing process design as “polymerization → structure → depolymerization” enables predictive yield targeting and energy-lean operation across mixed wastes, providing actionable guidance on catalyst selection, severity and residence-time control, regeneration, and integrated halogen management.

This study explores a sustainable method for converting sewage sludge with 80% water content into reusable biochar through drying and pyrolysis. The drying phase reduces water content to 12-15% using energy from pyrolysis-produced biochar, minimizing external energy requirements. Pyrolysis decomposes organic materials, producing biochar, gases, and oils, which are burned for energy recovery. The biochar can be reused up to eight times, enhancing resource efficiency and sustainability. Heat generated during both drying and pyrolysis is recycled within the system, further improving energy efficiency. The process demonstrates an innovative, closed-loop approach to waste management, minimizing waste and maximizing energy recovery, with significant potential for industrial applications.