Introduction of an underground waste container system–model and solution approaches

In Germany, household waste is collected via a door-to-door collection system. This form of waste collection is already reaching its limits due to the increasing volume of household waste and lack of space for even more dustbins, especially in densely populated cities. In this paper we investigate an alternative collection system: an underground waste collection system in which waste would be collected at central locations in so-called underground containers with a much larger capacity. If an underground container system is to be introduced to replace the present door-to-door waste collection system, a number of decisions of varying scope have to be made: Where should the underground containers be placed? How much capacity should be provided at which collection site? Which household should dispose of its waste where? How often, when and in what order should the waste collection vehicles empty the containers? In this paper we develop a model to illustrate the combination of the underlying problems by extending a problem known from literature. We present both hierarchical and integrated approaches to solve it. The proposed solution approaches combine in different ways two variable neighborhood search heuristics and a mixed integer programming-based exact method. We show that great benefits can be achieved through the use of integrated solution approaches. But we show too that integrated solution approaches do not necessarily dominate hierarchical ones.