Managing transportation operations of reusable packages in supply chain systems

Containers and packages contribute to about 28% of more than 292 million tons of municipal solid waste generation. Although a shift from single-use to reuse models seems inevitable for more sustainable packaging, there are economic and environmental aspects of reusables' operational management implications that are yet to be investigated. As more than half of the total costs of logistics operations come from transportation and transportation operations have been perceived as the main barrier in successful implementation of reusable packages, the main purpose of this research is to develop analytical frameworks for managing transportation operations of reusable packages.Transportation operations of reusable packages comprise of two tasks: delivery of full reusable packages from a central depot (product/packaging sites) to customers' door and pickup of empty ones from customers' door and transporting them back to the depot (cleaning facilities) where they are cleaned, refilled, and reused. The delivery of full reusables and the pickup of empty ones can be mathematically modeled as the vehicle routing problem with backhauls (VRPBs). The aim of the VRPB is to construct a set of optimal routing plans for a fleet of homogenous vehicles located at the depot such that (i) full packages are loaded at the depot and transported to customers' door, (ii) empty packages are collected from customers' door and returned to the depot, (iii) each vehicle starts (ends) its route from (at) the depot, (iv) each customer (with delivery and/or pickup requests) is visited exactly once and exactly by one vehicle, and (v) the total requests served by a vehicle does not exceed the vehicle's capacity.In this research, we mathematically formulate the delivery and pickup operations of reusable packages as the VRPB in two different networks: static and dynamic. In the static network, all input data (such as customers' request and location) is known before transportation operations start, while in the dynamic one, all or part of input data is revealed during transportation operations. To formulate the problem, we initially propose a new mixed-integer programming (MIP) model for a special class of the VRPB that serves delivery requests prior to pickup requests. In this case, we assume that customers either have delivery or pickup request and not both. We expand our model to a broader version of the VRPB where all or some customers have both delivery and pickup requests, and a pickup request can be served before a delivery request. We further develop an algorithm to manage transportation operations of reusable packages in dynamic networks. We present an analysis of the efficiency of transportation operations under a variety of factors that could provide valuable insights for decision-makers in adopting reuse models.