Municipal solid waste management in Europe has undergone a profound transformation over the past three decades, driven by regulatory harmonization at the European Union level, technological advances in waste treatment, and evolving societal expectations regarding sustainability and climate responsibility. Central to this transformation is the separate collection of waste fractions, particularly bio-waste and dry recyclables, which is widely regarded as a prerequisite for high-quality recycling and material recovery. This article develops a comprehensive and integrative analysis of the determinants, impacts, and policy implications of separate collection systems in European municipalities, with a particular emphasis on behavioral responses, institutional arrangements, and governance models. Drawing strictly on the provided body of literature, the study synthesizes insights from environmental economics, public administration, and waste management engineering to explore how collection design, pricing instruments, privatization, inter-municipal cooperation, and regulatory frameworks interact to shape recycling outcomes. The article further examines how door-to-door bio-waste collection can generate positive spillovers for the collection of dry recyclables, how unit-based pricing affects household behavior, and how heterogeneous treatment effects challenge conventional evaluation methods in policy analysis. Rather than offering a narrow empirical assessment, the paper adopts a theoretically rich and descriptive approach, unpacking causal mechanisms, contextual contingencies, and long-term system dynamics. The findings highlight that separate collection performance cannot be understood in isolation but emerges from a complex interplay of behavioral incentives, institutional capacity, market structures, and legal constraints. The discussion critically assesses limitations in current approaches and identifies future research directions, particularly regarding equity, administrative feasibility, and the alignment of climate and resource efficiency objectives. The article concludes that achieving high recycling rates in Europe requires not only technical optimization but also coherent policy mixes and adaptive governance frameworks capable of accommodating local diversity while meeting overarching European targets.

The growing demand for sustainable and efficient chemical manufacturing has driven the exploration of advanced process intensification strategies, including ultrasound-assisted reactions, non-thermal plasma technologies, and hybrid catalytic systems. Ultrasound and plasma-based methodologies have demonstrated remarkable potential in reducing reaction times, enhancing selectivity, and lowering energy consumption in diverse chemical transformations. This review investigates the theoretical underpinnings, mechanistic pathways, and industrial implications of ultrasound- and plasma-assisted chemical processes, emphasizing their integration into green and continuous manufacturing paradigms. The study synthesizes experimental findings across multiple reaction types, including Suzuki–Miyaura cross-coupling, enzymatic transesterifications, bromination reactions, and ammonia synthesis. Special attention is devoted to process optimization approaches, including uniform design for ultrasound-assisted syntheses and reactor design for plasma-enhanced reforming technologies. The work further examines the synergistic interactions between ultrasound and catalysts, as well as the non-thermal plasma effects on molecular activation and pollutant abatement. Challenges such as scale-up limitations, energy efficiency, and mechanistic uncertainties are critically analyzed, highlighting future directions for the development of industrially viable, environmentally benign chemical processes. This comprehensive exploration underscores the potential of integrating ultrasound and plasma technologies into the fourth industrial revolution, facilitating sustainable production of pharmaceuticals, platform chemicals, and energy carriers while minimizing environmental impact.