Abstract
•We investigate the contamination issue in SSR in Florida analyzing the audit data.•High reject rate in inbound streams is the main driver of the contamination issue.•Grit/fines/sweepings, mixed plastics, scrap metals are the main contaminants.•Contamination rates in glass and colored HDPE streams can be up to 45%.•None of the obtained 266 ONP and only 31.4% OCC samples meet the mill standards.
The single stream recycling (SSR) program is a process in which all recyclable materials are deposited into a single collection bin. SSR has gained popularity in the U.S. due to its inherent abilities in waste collection, and specifically, in Florida, more than twenty counties have recently switched their recycling program from dual stream recycling (DSR) to SSR. Despite a more efficient collection process, mixing all recyclable materials into a single bin can lead to cross contamination even before reaching material recovery facilities (MRFs). This study aims to provide a better understanding of the sorting process and equipment in MRFs, and the impact of the SSR program on contamination rates in outbound materials that were processed through Florida’s recycling systems. First, we investigate the audit data obtained from a currently operating MRF in Florida using mass flow analysis to identify the most problematic recyclable streams and the processes with low efficiency and high false separation rates. According to our results, the sorting rates of mixed paper, glass and plastics are under the industry standards. Moreover, we investigate the outbound contamination rates of 35 old corrugated cardboard (OCC) and 266 old newsprints (ONP) samples obtained from four currently operating MRFs in Florida. Based on the results, only 31.4% of OCC samples and none of the ONP samples were within the accepted mills’ standards for contamination rates. This study provides valuable insights for lowering contamination and raising the end-product quality by identifying the problematic contaminants and processes in sorting and separation in MRFs.
