Sorting optimization could prevent material loss to glass residuals
A Plastics Forming Enterprises (PFE) study that sorted and characterized plastics materials found in the glass commodity stream from glass processing in California revealed that more than 37 percent of the material was not even considered small plastic and appeared to meet the criteria for recyclability if the primary sort was optimized to prevent the material from entering the glass residual line.
PFE performed the study on behalf of the Glass Packaging Institute, Arlington, Virginia, in collaboration with the Small Format Coalition (SFC), which was formed last year to bring together stakeholders across the brand packaging, material processing and recycling value chain to improve the recovery of small format materials from the recycling system.
Through its research, SFC seeks to understand the mix of recoverable commodities contained in material recovery facility (MRF) glass. Since its formation in 2025, SFC has alerted policymakers to the presence and recovery possibilities of small nonglass packaging materials in the recycling stream.
The study materials underwent a primary sort and analysis by an optical sorter from Nashville, Tennessee-based MSS. The material was comprised of random samples with multiple pulls from different inbound sources to anonymize the material according to industry review and analytical standards. Half of all the material in the glass commodity stream was not glass, with the MSS optical data showing roughly one-third is fiber, another 15 percent is plastics and varying-sized metals made up nearly 5 percent. Larger recyclables also made up the glass stream, along with a variety of material that was not otherwise recyclable.
The material recovered from the glass stream was sorted by MSS into five plastic categories—polyethylene terephthalate (PET), polypropylene (PP), polyethylene (PE), black plastics and mixed plastics—and then shipped to PFE for further analysis.
PFE then hand-sorted each material category and removed items that would be detrimental to reprocessing, processing each material stream through a series of recycling operations. PET, PE and PP were injection molded into plaques suitable for comprehensive mechanical testing. According to the study, limited amounts of the black plastics and mixed plastics streams were injected given excessive fuming and poor resulting part quality, indicating limited potential for further evaluation.
Sixty-two percent of the material studied met the Association of Plastics Recyclers (APR) definition of small plastics, measuring less than 2 inches in size. Among the total plastic material composition was 51 percent was PP, 16 percent was PE, and 18 percent was mixed-resin black plastics.
Despite meeting APR's size requirements, 37 percent of items bypassed conventional plastic sorting systems and reported to the glass stream, according to the study, indicating that package size alone might not fully explain sortation outcomes. “Factors such as package shape, rigidity, weight, material properties, equipment configuration, operating conditions and facility-specific practices may also influence whether an item is successfully recovered,” according to the study. “Their presence in the glass stream highlights a broader material recovery opportunity that extends beyond small-format packaging and includes any recyclable plastic that bypasses primary MRF recovery."
According to the study, significant quantities of recyclable small-format plastics can be recovered from near-infrared-sorted glass stream material after additional quality control and contaminant removal, with PE and PP offering the best recovery opportunities in light of their combination of high volume and strong sorting yields.
“Studies like this punctuate the need for infrastructure to capture small format materials in California in compliance with EPR,” says Scott DeFife, president of Glass Packaging Institute (GPI). “All materials are all in the bin together, and the Small Format Coalition is working to finalize investments in technology in California that will impact the recovery and circularity of these products.
“Collaborative investments will provide real-world, real-time data on the volume and characteristics of the small and large fibers, metals and plastics that are recoverable from what is incorrectly categorized in the glass commodity stream in California,” he adds.
The SFC and its member producer brands, technology providers, end-market reclaimers and other industry collaborators, including the Center for Circular Economy Smalls Consortium, anticipate this data will help to further inform Circular Action Alliance and CalRecycle of the recyclability of many covered material categories in the Plastic Pollution Prevention and Packaging Producer Responsibility Act.
This article was originally published in Recycling Today.