Trash-flow allocation: Planning under uncertainty

The materials in trash, or municipal solid waste (MSW), may be recycled, composted, incinerated, or landfilled. Transporting these materials to waste-management facilities consumes part of the operating budget of a municipality. Many factors, the majority uncertain, may influence the planning of waste-flow allocation. MSW managers want to know (1) whether the existing pattern is close to the optimal, and (2) if not, what is the optimal? We used a gray linear-programming (GLP) model to address these questions for the regional municipality of Hamilton-Wentworth, Ontario. This approach can effectively reflect the interactive relationships between uncertain system components. It can also bring uncertain information into the optimization process and resulting solutions, permitting feasible decision alternatives to be generated. The region's waste managers have used the results to verify or adjust the existing waste-flow allocation pattern. They may also be used to formulate related local policies.