Some recyclers have been concerned that as more companies use bottles made from polylactic acid, those containers may contaminate the PET recycling stream. But tests at a full-scale recycler suggest near-infrared technology can effectively separate PLA and PET.
The results also showed that PET sheet made from the recycled resin produced by the tests was not contaminated. Bioplastics manufacturer NatureWorks LLC of Minnetonka, Minn., and Winston-Salem, N.C.-based Primo Water Corp., which packages water in PLA bottles, shared the results with Plastics News on June 30.
Recyclers still are not convinced. Some said the tests were not conducted under real operating conditions, the level of PLA bottles sorted out was not high enough and PLA bottles still have the potential to decrease their efficiency and already-shrinking yields.
I'm not sure that this answers all the questions recyclers have about PLA and its potential to contaminate the PET recycling process, said Steve Alexander, executive director of the Association of Postconsumer Plastic Recyclers in Washington.
There are a lot of different types of technologies out there, and they ran all their tests using one technology, near-infrared, and not all recyclers use that technology, he said.
Many PET recyclers use Vinyl Cycle detection systems from National Recovery Technologies Inc. of Nashville, Tenn. NIR systems, which cost upward of $200,000, typically are used by larger materials-recovery facilities and haulers.
The tests were conducted for NatureWorks and Primo and verified by independent consulting firm Plastics Forming Enterprises LLC. The tests used an NIR machine from TiTech VisionSort GmbH, based in Oslo, Norway.
About 75 pounds of Primo Water bottles roughly 1,500 bottles without caps or labels were flattened and added to a 35,000-pound load of PET bottles sourced from a deposit program. That volume was selected to mimic conditions if Primo had the fourth-highest market share in water bottles.
The firms planned to make the results public July 6. They said they would post a white paper containing the results on NatureWorks' Web site and share the data with recyclers and plastic recycling associations.
The tests found that 93 percent of the PLA was separated out. They said there was no appreciable color or haze difference between sheet samples made from a control batch produced from recycled PET resin and two sample sheets that contained PLA that was not separated out during sorting, said Brian Glasbrenner, NatureWorks business director for the Americas for beverages, film and cards.
Most of the tests were conducted earlier this year.
I'm confident in the testing and that this will get a large chunk of folks who have been neutral or against us on our side, supporting us, Glasbrenner said. This was not a lab-scale or staged test, but tests that were done at a full-scale commercial facility that was operating under normal conditions. We think it is a very fair, very realistic, very robust test. We used a reasonable amount of bottles and were able to verify the results through a third party.
But several recyclers disagreed.
For starters, one technical expert at a PET recycler said clarity depends on the thickness of the plaques, and samples were only measured across three different thicknesses.
Another recycler pointed out that adding the PLA bottles without caps or labels and only using bales collected from deposit programs does not simulate real-life conditions, as baled material contains both caps and labels, as well as other plastics such as PVC. Because the machine is getting a clearer look at the bottles, you get half the error rates, he said.
He also called the 93 percent sorting rate unacceptable.
Anything under 95 percent is usually unacceptable, he said. Besides, no reclaimer wants more contaminant in the bale, because yields are already going down, dropping to the low 80s in the past few years. No reclaimer is going to say, 'We can get it out, so throw it in.' The No. 1 thing reclaimers are fighting are reduced yields.
In addition, the tests do not address whether PLA that made it through the sorting equipment ended up being removed in the drying process something that recyclers say is a common problem with contaminants.
I'm not surprised that there is no contamination to the sheet because I'm sure the lion's share of PLA that didn't get sorted out is in the dessicant fan, the recycling executive said. Everyone knows that any contaminants that get through goop up the dryers, and that wasn't addressed in this study.
Tim Ronan, senior vice president of marketing for Primo Water, said he did not have information about contamination levels in the dryers. I am not sure about that, he said. We never talked about it. It wasn't part of the report. The dryer part never came up, so I am assuming it is not an issue.
Similarly, Ronan said NatureWorks and Primo were assured by the consulting firm, PFE, that there was no need to include caps or labels on the PLA bottles.
What we were able to do in a real setting in a commercial facility was prove that PLA can be sorted and recycled under normal recycling conditions in the systems that are used today, Ronan said. That should help recyclers be positive about the recycling of PLA, because if they have the right equipment, the opportunity is there to keep the bale as clean as possible.