Sorting success

Features - Paper Recycling Supplement

Optical sorters help material recovery facility operators improve fiber sorting.

December 3, 2021

Cal-Waste added five optical sorters in its 2020 MRF upgrade: three optical sorters on its fiber line and two on its container line.
Photo courtesy of California Waste Recovery Systems

For material recovery facility (MRF) operators, fiber tends to make up the largest portion of the overall material stream. With e-commerce becoming increasingly more common, MRFs also are receiving more boxes in residential recycling streams than they have in the past.

Recovered paper markets also have been strong, particularly since this summer, which has been helpful for MRF operators trying to sell old corrugated containers (OCC), mixed paper and sorted residential papers and news (SRPN). Although most recovered paper prices dipped slightly in the November buying period, prices remain higher than they were one year ago and significantly higher than they were two years ago.

As a result, MRF operators want to ensure they sort, bale and sell as much OCC and SRPN as possible while reducing their production of mixed paper, which has a lower value relative to these grades.

Increasingly, MRF operators are relying on optical sorters to sort fiber and improve recovery rates. During the 2021 MRF Operations Forum Webinar Series, which originally aired Oct. 18-19, optical sorter suppliers and MRF operators offered their insights into how optical sorters can be used to improve recovered paper sorting.

Seeing success

Suppliers and operators alike have seen optical sorters succeed at cleaning up fiber streams. Felix Hottenstein, sales director for MSS Inc., Nashville, Tennessee, said he has seen more MRFs add optical sorters to their fiber lines since National Sword went into effect in 2018. MSS is a division of CP Group of San Diego.

He tells Recycling Today in a follow-up call after the webinar that he has seen many MRFs invest in technology, such as optical sorters, to clean up their fiber streams since 2018. To date, he says, MSS has 80 of its units at MRFs specifically for sorting fiber.

During the webinar, Hottenstein said the technology has been particularly helpful at replacing some manual sorters at MRFs. “Manual sorters can only do so much, and machines can pick so much faster. With material being more spread out, they are much more efficient in terms of picks per minute.”

This trend of relying on optical sorters to clean up fiber streams is not unique to the United States, either. Jeff Fountain, director of sales at Pellenc ST America Inc., the Charlotte, North Carolina-based U.S. division of French company Pellenc ST, said he has seen MRFs around the world embrace optical sorting technology for this task. Specifically, he tells Recycling Today that his company is working with large MRF operators in London to incorporate Pellenc optical units on their fiber lines to replace manual sorters.

Similarly, Alex Wolf, director of technology at Van Dyk Recycling Solutions, Norwalk, Connecticut, said his company has worked with a handful of MRFs to clean up their paper streams with the help of optical sorting technology. He noted that Van Dyk’s designs in these applications focus on creating a higher quality paper grade.

During the MRF Operations Forum Webinar Series, MRF operators from the East and West coasts shared their successes in integrating optical sorters at their facilities on their fiber lines.

Casey Vaccarezza, director of operations at Galt, California-based California Waste Recovery Systems (Cal-Waste), said his facility upgraded its system Jan. 1, 2020, and incorporated five MSS optical sorters—three on its fiber lines and two on its container lines.

“We’re really happy, especially on the fiber side of things with the MSS units,” he said. “Fiber is the majority of the commodities that we pull out of the stream.”

Vaccarezza said the optical sorters have “come a long way since we put them in,” adding that Cal-Waste had to figure out “how to program them and create the right recipe to hit the specification in the market we’re selling.”

He said the optical units also have helped to decrease the MRF’s reliance on manual labor.

On the East Coast, Jeff Nella, recycling operations manager at Winters Bros. Waste Systems, headquartered in West Babylon, New York, added two optical sorting units from Green Machine, Whitney Point, New York, in May 2020 and a Pellenc dual-eject optical sorting unit in March to the company’s dual-stream MRF in Brookhaven, New York. Nella said the opticals have enabled the MRF to produce a higher quality SRPN grade in addition to mixed paper.

Setups that work

MRF operators have different approaches when using their optical sorters. Nella said his MRF positively sorts materials with its units. “Everything is a positive sort for us,” he said. “You get a cleaner stream.”

Hottenstein of MSS said he has seen more MRFs transition from negative to positive sorting on fiber lines in the last two to three years, as well. He added, “There are too many unsortables in the stream to negatively sort.”

Suppliers of optical sorters expressed differing opinions on whether materials should be processed via a traditional star or disc screen or a ballistic separator prior to being presented to the optical sorter.

Wolf of Van Dyk said MRFs could benefit from placing a ballistic separator (Van Dyk refers to its ballistic separator as an elliptical screen.) before the optical sorter. “What we personally found is that they’re complementary to each other,” Wolf said. “An elliptical separator does really well in separating plastic film from containers. … It’s a perfect device to prepare your 3D container stream and clean out basically everything that is still left in it. Now with the Amazon effect and all of the 3D boxboard and everything coming through, that’s where ballistic separators or ellipticals struggle.”

Wolf said Van Dyk often installs optical sorters to clean out the remaining paper in the line, while the elliptical cleans out the remaining containers.

He added that opticals can help to sort paper that winds up on container lines.

However, Hottenstein of MSS noted that ballistics aren’t the best option to place ahead of opticals in all situations.

“Everybody likes them because they are low maintenance; but, based on what we’ve seen, they are very sensitive to throughput. And as soon as throughput is a little too high, they have issues,” he said of ballistics. “So, we prefer other separation devices. “ Hottenstein said. “We prefer disc screens.”

Contaminant cleanup

Fountain of Pellenc said near-infrared (NIR) cameras on some optical units still can struggle to remove black plastics from fiber lines because the cameras are unable to detect that material.

“Every optical sorter maker uses a light source, and we need that light source to shine down on the conveyor belt where materials go through that light,” he explains in a follow-up conversation with Recycling Today. “Every material will absorb some amount of light, and optical sorter manufacturers take in data on whether light has been absorbed or not from a material. When a black object goes through it, there’s no data, [and] the machine thinks there’s nothing there.”

In the past, this was less of a problem because fewer MRFs were receiving black plastics. But Fountain says it’s a bigger issue today, therefore some new optical sorters offer solutions to this sorting problem.

He says Pellenc offers profile detection technology for its optical sorters to help them to sort by shape rather than solely by color or chemistry. He says this enables the unit to retrieve materials the NIR technology might have missed.

Hottenstein said MSS does not yet offer technology that would enable its optical sorters to see items not detectable by NIR. As a result, he said positive sorting is another method for MRFs to remove black plastics from fiber lines.

Positive return on investment

MRF operators have benefited from using optical sorters on their fiber lines, including Nella’s Brookhaven MRF. “We’ve been rewarded by more people wanting it and pricing it significantly over index price,” Nella said. “On the OCC side, I’m probably seeing $5 to $10 more per ton than most of my competitors in the marketplace.”

Not long after installing optical sorters and upgrading its MRF in 2020, Vaccarezza said Cal-Waste noticed improvements in labor and throughput.

“We went from running a 10-ton-per-hour (tph) system to 30 tph on the new system,” he said. “We had 25 people on the old system running 10 to 12 tons an hour with no optics and a basic system. Converting over to this 30-tph system, we’re at 22 people on the line. Our throughput tripled. We’ve seen a big savings in labor with the increased tonnages as well.”

With this success, he added that his MRF is looking to add three to four more optical units to further decrease its staffing requirements.

He said, “The [return on investment] is there in the labor for adding these units. We’ve seen it firsthand with putting this new system in.”

The author is managing editor of Recycling Today and can be reached at by email.