Plants in black tray / kellis, ShutterstockPackaging producers should choose clear or translucent PET containers because opaque and colored ones inhibit recycling of the material into higher-value applications.

That’s according to a report examining the top 15 materials and packaging types presenting headaches for materials recovery facilities. Most of the materials featured involved plastic packaging.

Released in late March, the study touched on colored PET, black containers and single-use plastic coffee pods, among other packaging types. It was released by Pac Next, part of the industry-funded Pac Packaging Consortium.

The report updates a late-2014 analysis. The following are three of the packaging challenges detailed in the report:

Colored PET

Most current optical sorters will sort colored and opaque PET containers along with clear PET, reducing the bale yield of higher-value clear PET. Unlike clear PET, colored PET is generally limited to gray or black applications, for which there are limited end markets.

The colored material can also contaminate the stream. In particular, titanium dioxide, used to create white plastics, “is very detrimental to PET recycling for bottle-to-bottle and engineered resin uses,” according to the paper.

A year ago, trade group Plastic Recyclers Europe issued a statement expressing concern that an influx of colored, opaque PET was endangering reclaimers’ ability to recycle the resin. It came as some producers were switching from HDPE to PET for their milk, personal-care and home-product packaging.

Black containers

Black food containers, nursery pots, plant trays and other items can’t be seen by most optical sorters, the report states, so they must be manually sorted. Even if sorted correctly, their dark color limits their market applications.

Optical sorting technologies are being explored that would require the use of an additive that can be detected by near-infrared sensors. Ontario, Canada-based company TeTechS developed a terahertz sensor technology to identify black plastics. Terahertz radiation falls between infrared and microwave radiation on the electromagnetic spectrum.

The Pac Next report also noted that black nursery pots and trays are often made of recycled plastics, and while recycled content with multiple resins can complicate subsequent recycling, the writers urged a continued use of recycled content in the items.

It’s a different story with PET and PP food trays, which are often virgin plastic.

“Where possible, alternative colored materials (other than black) should be used to facilitate optical sorters capturing more materials for mixed plastic bales,” the report notes.

Coffee pods

In most places, K-Cups and other single-serve coffee and tea pods aren’t accepted in curbside programs, but some consumers are putting them there anyway.

British Columbia accepts separated pods (those in which the filter, lid and coffee grounds have been removed by the consumer) in its producer-funded curbside program, with optical sorters targeting the PS cups.

Pods that still contain coffee grounds tend to fall through screens and contaminate streams, particularly glass. Empty ones have a better shot at being sorted correctly. Trial runs at MRFs have shown that 70 to 75 percent of empty pods can be properly sorted on both dual-stream and single-stream lines. Those lost often do so because they fall through screens with heavy materials.

Keurig Green Mountain recently announced its plans to improve the recoverability of its K-Cups.

Pac Next discussed the industry effort to improve the recyclability of the products. One step has been making the cups out of PP. “On the recycling side, there are innovations to make the separation process much easier for consumers and to improve the material of the outer cup so that it is more valuable for downstream recyclers,” the Pac Next analysis states.