Optimisation of municipal solid waste collection to enhance materials recovery

Municipal Solid Waste (MSW) management plays a critical role in advancing the goals of the circular economy and climate neutrality across the European Union. Within this framework, collection is not merely a logistical task, but a strategic lever for enhancing material recovery, reducing environmental impacts, and improving system-wide efficiency. Despite its central role, MSW collection is still frequently approached as an operational routine, with limited integration into planning and policy frameworks. The present doctoral research aims to address this gap by exploring how the optimisation of MSW collection systems can improve overall waste management performance, focusing on three key dimensions: material capture, operational efficiency, and environmental sustainability. Chapter 1 outlines the conceptual and regulatory background, highlighting the evolving role of MSW management in the EU circular economy agenda and comparing the current systems of Italy and Spain, with a focus on the regional contexts of Tuscany and Catalonia. The chapter concludes by defining the research objectives and introducing the methodological framework, which integrates empirical data collection, statistical analysis, environmental-economic assessment, and a modelling approach based on system-level assessment tools widely used in waste management, namely material flow analysis (MFA) and life cycle assessment (LCA). Chapter 2 analyses MSW composition and the performance of separate collection (SC) systems in Tuscany, based on more than 1,100 samples covering all urban waste fractions, including residual waste. A consistent classification methodology was applied across the region, accounting for region-specific and policy-relevant material categories (e.g., packaging, textiles, sanitary and personal hygiene waste). The study found that biodegradable organics represent the largest fraction of total MSW (27.2%), followed by paper and cardboard (21.3%) and plastics (16.3%). Textiles (8.8%) and sanitary waste (6.2%) also emerged as growing challenges. Importantly, more than 50% of residual waste is still composed of recyclable materials, indicating a substantial margin for improvement in SC effectiveness. While the region reports a high SC rate (67%), results highlight persistent inefficiencies in capture rates for key materials—particularly plastics and metals—and high impurity levels in the light packaging stream. When comparing collection models, door-to-door systems outperformed street-bin systems in terms of SC quality, supporting the need for context-specific strategies and complementary instruments, such as smart containers, Pay-As-You-Throw (PAYT) schemes, and targeted communication campaigns to improve conventional kerbside collection. Chapter 3 focuses on the environmental and economic implications of waste collection logistics, which are often underestimated in policy assessments. A field monitoring campaign was conducted in four sub- areas of central Tuscany, recording 233 empirical observations of fuel consumption across different vehicle types and collection configurations. These data revealed that real-world CO₂ emissions from waste collection vehicles often exceed national inventory factors, with average values ranging from 2.3 to 3.7 kg CO₂/km for heavy-duty vehicles. Building on these observations, a predictive decision-support model was developed to simulate the performance of different door-to-door and street-bin configurations under varying territorial conditions. The simulation results show that street-bin systems tend to be more efficient and generate less CO₂ emissions in high-density areas, while door-to-door systems offer environmental advantages in rural and low-density contexts. These findings support the development of differentiated collection strategies tailored to local conditions, balancing cost-effectiveness with sustainability objectives. When the model accounts for the quality of collected materials (i.e. impurity rates), door-to-door systems exhibit lower CO₂ emissions across all density levels, while street-bin systems remain more cost-effective. The results highlight a misalignment between environmental and economic costs, suggesting the need to rebalance incentives through higher landfill fees, quality-based bonuses, and the adoption of smart technologies to improve the quality of street-bin collection. In Chapter 4 an integrated MFA–LCA framework is applied to assess the environmental performance of MSW management in Catalonia. Two scenarios were modelled: the current system, characterised by a separate collection rate of 45% and limited door-to-door coverage (11% of population), and a prospective i high-performance system with a 65% separate collection rate and 72% door-to-door coverage. The MFA revealed that increasing the separate collection rate improved the overall recycling rate from 37.7% to 53.3%, bringing the system closer to the EU 2025 target. However, the landfilling rate remained high (29.5%), mainly due to increased process residues from recycling operations. These results stress the importance of diverting a larger share of residual waste and treatment residues towards high-efficiency waste-to-energy (WtE) facilities. In parallel, reducing the generation of non-recyclable materials at source is equally crucial to limit the production of residual waste and treatment rejects. Further investigation into the composition of residual and sorted fractions, as conducted in Chapter 2, can support the identification of problematic materials and guide forthcoming policy actions on eco-design for more sustainable products. The LCA results confirmed that the high-performance scenario delivers substantial benefits in global environmental indicators. In particular, net climate change impacts decreased by 23%, primarily due to reduced reliance on landfilling and municipal incineration, and increased environmental credits from material recycling, especially of paper, glass, and plastics. However, the transition also led to increased greenhouse gas emissions from the collection and treatment stages, due to the expansion of door-to-door collection and the higher energy demands of recycling processes. Trade-offs also emerged in local impact categories: particulate matter and photochemical ozone formation increased by 181% and 146%, respectively. These increases reflect the greater contribution of collection and treatment activities to these impacts, highlighting the need to optimise high-performance separate collection systems through improved logistics, fleet design, and treatment infrastructure. Chapter 5 summarises the five priority actions identified in this research for improving the performance of MSW collection systems: • Adopt strategies that incorporate routine, time-structured waste characterisation campaigns covering all MSW fractions and applying harmonised methodologies across municipalities and over time. This would enable a more accurate and up-to-date understanding of waste composition and its evolution, supporting evidence-based planning and policy-making in MSW management; • Enhance separate collection schemes by focusing not only on the quantity but also on the quality of collected waste streams, particularly in terms of material purity; • Use real-world operational data to develop evidence-based assessments of the environmental and economic performance of MSW management systems; • Reframe the role of the collection phase, recognising it not as a purely routine task but as a central element in the transition towards sustainable, circular, and performance-based MSW management systems. Planning and decision-making on collection system design and implementation should be grounded in systematic evaluations of trade-offs between operational costs and environmental performance, rather than driven by political or financial constraints; • Prioritise energy recovery and eco-design regulations—alongside reuse and recycling—as part of integrated MSW management strategies aimed at reducing residual waste to a truly residual fraction. By combining empirical evidence, innovative modelling, and scenario-based evaluation of economic and environmental performance, this thesis reframes MSW collection as a central component of sustainable waste governance and offers actionable insights to support both local optimisation and national-level policy development.