Sustainable Campus Waste Management: A Practical Separability Framework and Field Studies of Bin Configurations and Bin-Free Classrooms

Source separation is central to Sustainable Development Goal targets 11.6 and 12.5, yet behavioural interventions are often implemented without establishing what proportion of the waste stream users can realistically separate. This study presents a 2026 diagnostic of waste management at the Universidad de Monterrey (UDEM), Mexico. An exploratory, constraint-based classification framework indicated that 8.8% of campus waste was amenable to user-level separation at the point of disposal (Type A), 19.1% could be separated through staff protocols (Type B), and 72.1% was practically non-separable under the conditions assessed (Type C). Two field studies examined factors associated with Type A separation: bin configurations and the temporary reintroduction of classroom bins. In an observational comparison (N = 50), units with restricted apertures (circular, bottle-sized openings) showed median item-based compliance of 60–82%, compared with 18–19% for open-aperture units. However, the configurations also differed in signage, location, and user populations, precluding attribution of the observed differences to aperture geometry alone. Under normal operating conditions, classrooms have no bins. Temporarily reintroducing an unsorted bin in 20 classrooms revealed no statistically detectable difference in visible litter items per classroom-day (p = 0.513). Recyclables deposited in the reintroduced bins entered the residual waste stream, although the fate of comparable items under bin-free conditions was not tracked. Practical implications for campus waste management are discussed.