A Multi-Objective Optimization Model for Multi-Facility Decisions of Infectious Waste Transshipment and Disposal

Abstract

Infectious waste disposal is a crucial concern in many areas. Not only is the waste obnoxious, but it can also pose a vital risk to human health. Disposal of infectious waste incurs higher costs than general waste disposal and must abide by stricter regulations. In this paper, the infectious waste disposal is formulated as a multi-objective optimization model. The objectives encompass economic, social, and environmental concerns. To save cost, waste transshipment facilities to function as consolidation points are proposed and integrated in the model. The economic objective includes construction and operational costs of the transshipment and disposal facilities. The social objective considers the communities surrounding the disposal facilities, while carbon dioxide emission is used as the measure in the environmental objective. The model is reformulated based on the lexicographic weighted Tchebycheff method to ensure that the Pareto frontier of the solutions is obtained. Then the model is applied to a health region in Thailand. Daily and every-other-day waste collection intervals are compared to examine additional benefits. Certain sensitivity of the solutions is also analyzed. After comparing several solutions, a compromise among all three objectives is suggested. It is composed of three transshipment and two disposal facilities, each with 1000 kg capacity. Moreover, if the solution is executed with the every-other-day waste collection interval, the overall costs can be saved. A sensitivity analysis of the solution on fuel price found that the solution was not very sensitive against an increase in the fuel price, in that when the fuel price increased by 20% the overall costs only increased by 7%. Lastly, when the daily infectious wastes are doubled, all the objective function values rise, ranging from 56% to 163%. The new solution suggests an increase in the number of the disposal facilities to four, but a decrease of the transshipment ones to only two.