Quantification and characterisation of the illegal dumping of municipal waste

Even in developed countries, municipal waste (MW) left outside communal containers remains a significant challenge, affecting urban hygiene. This study analysed the improper disposal of MW across three monitoring circuits, each 14 km long, representing rural inland, urban inland, and urban coastal settings, with particular attention to the pre-holiday period and the preparation of dwellings for the tourist season. A total of 128 sites were systematically monitored over three periods, recording 407 occurrences. The total estimated volume and mass of abandoned MW varied across circuits, with the urban inland circuit accounting for the highest number of new occurrences, as well as the largest estimated volumes and masses of waste. By volume, paper and cardboard packaging and bulky waste predominated, particularly in the coastal urban area. By mass, construction and demolition waste (CDW) arising from minor construction and demolition activities within private households accounted for the largest fraction. In Portugal, the management of CDW generated by such activities is the responsibility of MW management systems. Furthermore, higher per capita amounts of abandoned MW were recorded in the urban coastal area. These patterns may reflect the preparation of dwellings for the summer tourist season. The recurrence of improper waste disposal highlighted operational challenges for waste collection planning. The findings also suggest a potential role of citizen behaviour in waste abandonment. In addition, the study developed context-adjusted indicators of MW abandonment, which may support further research and inform MW management practices, particularly by helping to identify spatial patterns of waste abandonment and optimise collection strategies.