A DEMATEL Framework for Modeling Cause-and-Effect Relationships of Inbound Contamination in Single-Stream Recycling Programs

Abstract

Material Recovery Facilities (MRFs) are the foundation of United States recycling programs. MRFs collect recyclable materials from end users for export to be processed abroad or to sell to mills for further refinement and reuse. The most popular type of recycling collection in the United States is Single-Stream Recycling (SSR). Numerous studies have validated the program’s popularity and consumer acceptance. In contrast to other recycling plans, SSR’s favored status rests on its minimal consumer burden, which requires only a cursory identification of potentially recyclable materials for placement in a single container separate from other waste. Researchers have also found that collecting SSR materials requires less staff and cheaper collection vehicles. While SSR generates greater end-user acceptance than other recycling collection programs, SSR differs markedly in terms of higher inbound contamination rates and quality of recovered recycling materials. Single-stream collection increases cross-contamination through mixing recyclable and non-recyclable materials in a single container. High contamination rates lower the quality of incoming recyclables and increase overall MRF operating costs due to additional sorting time and related staffing costs. This paper aims to analyze the causes of high inbound contamination in SSR using Decision-Making Trial and Evaluation Laboratory (DEMATEL) techniques to support deeper analysis of the relative importance of three factors that scholars have identified as being related to SSR inbound contamination of MRFs. Based on the results obtained, the absence of awareness campaigns is one of the crucial factors increasing inbound contamination due to the inefficiency of the SSR system in separating unrecyclable from recyclable materials; therefore, the sorting equipment at MRFs requires further improvement. Focused analysis of causal inbound contamination factors may assist in furthering efforts to reduce SSR contamination.