Solving a rich vehicle routing and inventory problem using column generation

The livestock collection problem (LCP) is a rich vehicle routing problem (VRP) extended with inventory constraints. The LCP is a complex planning problem taken from the meat industry, and the goal is to construct a set of vehicle routes to collect animals from farms for slaughter at a slaughterhouse. Several constraints dealing with animal welfare are added, some of these lead to a loading problem where the vehicle capacity depends on the loading sequence. In addition, global constraints to handle production and inventory at the slaughterhouse are needed. This paper presents an exact solution method for the LCP, based on column generation, that solves much larger instances to optimality than what has been done before. The algorithm presented here also solves a richer model that is closer to the underlying real-world problem than previously published work on exact methods for this problem is based on.