Sustainability assessment of municipal solid waste separate collection and treatment systems in a large metropolitan area

Among different modes for municipal solid waste separate collection (SC), there is a lack of scientifically based methods for their selection available for decision-makers. This study develops and applies a methodology based on Multi-Criteria Decision Analysis (MCDA) aiming to assess and compare the sustainability of different waste management schemes. Considering the city of Bari (Southern Italy) as a supporting case study, 3 systems/visions of city waste management options are considered: (i) bring points systems with about 35% SC rate (S1, status quo); (ii) door-to-door system with an excellent (>80%) SC rate (S2); (iii) combined bring point and door-to-door system (S3, with about 70% SC rate). Scenarios differed mainly on the management of the residual fraction from SC through mechanical-biological treatment (S1 and S2) or recovery of recyclables at material recovery facility (S3). Sustainability is assessed in environmental, economic, and socio-technical terms by means of MCDA and Life Cycle Assessment (LCA). Results showed that S2 is the best solution in global, environmental, and socio-technical terms, while the weak point is the cost (65.76 € per capita). Even more interesting is the limited deviation between S3 and S2 indicators, amounting to 5.4% and 9.4% in terms of environmental and socio-technical criteria respectively, suggesting a strong competitiveness of the mixed collection mode. Methodologically, the approach proved to be robust and easy to apply by local authority decision-makers.