A Direct Route to Sustainability: A Network Optimization Model to Reduce UNICEF Zimbabwe’s Carbon Footprint

Abstract

As part of Agenda-2030, the United Nations developed the Sustainable Development Goals (SDGs) with the objective of achieving a better and more sustainable future. One of the key drivers for reaching this objective is to lower carbon emissions globally. In line with the carbon SDGs goals, the United Nations Children’s Fund (UNICEF), a United Nations agency responsible for providing humanitarian and development aid to children worldwide, sponsors this capstone project to analyse the carbon emissions of its supply chain transportation network in Zimbabwe. Through this capstone project, we study the effects, in terms of carbon and costs, for utilizing direct routes between UNICEF’s suppliers and end beneficiary. In this capstone project, we formulate a multi- objective optimization model that optimizes simultaneously the total costs and carbon emissions. Yet, in contrast with other green network design models that rely on aggregate methods for calculating carbon emissions (such as the Green House Gas protocol), in this study we not only use an equation that considers a more granular fuel consumption estimation of the vehicles (i.e. adapted from the Network for Transport Measures), but we also calculate the theoretical fuel consumption of the vehicle by using the comprehensive modal emissions model that also considers specific characteristics of the road, engine speed, engine displacement, velocity, total weight, road slope, and acceleration. To the best of our knowledge, this study is the first attempt to combine two of the most detailed estimation models of transport emissions. In addition, our proposed network design model includes the flow of multiple products within UNICEF Zimbabwe’s supply chain network, as well as consolidation capabilities, that is, the output of the model provides the optimal combination of products to consolidate within each truck shipment. Our results are visualized using the Pareto Frontier that displays all optimal carbon and cost combinations for UNICEF’s network. This Pareto Frontier serves as a tool that UNICEF’s management can use to choose the desired levels of cost and carbon emission. Ultimately, we find that enabling direct routes in the model produces a win-win situation where both carbon emissions and costs are reduced.