Combining operational research and Life Cycle Assessment to optimize municipal solid waste collection in a district in Lima (Peru)

Waste management in cities has proved to be a complex task for policy-makers who seek cost reductions when taking decisions. However, on many occasions substantial environmental gain can be attained through waste management optimization. In this particular study, the main objective was to combine operational research techniques with Life Cycle Assessment to locate collection sites for general and recyclable residues and create an effective collection-route system for compactor trucks to attain a reduction in environmental impacts. The case study selected was the district of Comas, one of the most populated districts in the city of Lima, a city that has experienced several episodes of poor waste collection management in recent years. For the location of the collection sites a mathematical optimization model was proposed to decide where to locate them, as well as the number of containers required at each site, considering that general and recyclable residues would not be collected at the same site due to the restricted space available. For the creation of collection routes, a heuristic approach based on the Vehicle Routing Problem was constructed, taking into account the available working time of each collection truck to assign them collection routes and minimize the number of compactor trucks. These results, when combined with LCA, focused mainly on greenhouse gas (GHG) emissions, air pollution impact categories and the depletion of abiotic resources. In addition, a sensitivity analysis was developed by varying three different parameters with respect to the proposed baseline scenario, comparing the several impact categories. Computed results show that implementing a container collection system reduces the number of compactor trucks required by up to 50% as compared to the current door-to-door collection system. Moreover, GHG emissions where reduced by almost 14% with the proposal, mostly due to a 41% reduction in distance traveled. Reductions in terms of particulate matter formation and photochemical oxidant formation were even more significant, especially considering that air pollution is an important health hazard in the district analyzed, whereas most scenarios showed a slight increase in resource depletion due to the inclusion of container infrastructure in the system.