What is measured is managed : statistical analysis of compositional data towards improved materials recovery

Abstract

As materials consumption increases globally, minimizing the end-of-life impact of solid waste has become a critical challenge. Cost-effective methods of quantifying and tracking municipal solid waste contents and disposal processes are necessary to drive and track increases in material recovery and recycling. This work presents an algorithm for estimating the average quantity and composition of municipal waste produced by individual locations. Mass fraction confidence intervals for different types of waste were calculated from data collected by sorting and weighing waste samples from municipal sites. This algorithm recognizes the compositional nature of mass fraction waste data. The algorithm developed in this work also evaluated the value of additional waste samples in refining mass fraction confidence intervals. Additionally, a greenhouse gas emissions model compared carbon dioxide emissions for different disposal methods of waste, in particular landfilling and recycling, based on the waste stream. This allowed for identification of recycling opportunities based on carbon dioxide emission savings from offsetting the need for primary materials extraction. Casework was conduced with this methodology using site-specific waste audit data from industry. The waste streams and carbon dioxide emissions of three categories of municipal waste producers, retail, commercial, and industrial, were compared. Paper and plastic products, whose mass fraction averages ranged from 40% to 52% and 26% to 29%, respectively, dominated the waste streams of these three industries. Average carbon dioxide emissions in each of these three industries ranged from 2.18 kg of CO₂ to 2.5 kg of CO₂ per kilogram of waste thrown away. On average, Americans throw away about 2 kilograms per person per day of solid waste.