Capturing the last can

Features - MRF Series

MRFs that have added a second eddy current to their sorting lines have been able to capture more UBCs that otherwise would have been lost to residue.

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February 28, 2019

© Dmitriy Syechin / stock.adobe.com

Material recovery facilities (MRFs) that operate a second eddy current on their sorting lines can divert an additional 30,000 pounds of aluminum per month on average compared with MRFs that operate a single eddy current. Purchasing and installing a second eddy current can cost a MRF $110,000, which puts the typical return on investment (ROI) at less than six months because of the high value of aluminum. (The January average U.S. price for used beverage cans, or UBCs, was $25.64 per pound, according to data from Fastmarkets AMM.)

Getting compressed

During the hauling process, lightweight aluminum cans often are crushed and flattened into two-dimensional “pucks,” making it difficult to separate them effectively with a single eddy current. Many UBCs don’t even make it to the eddy current; they are incorrectly separated out with other materials, such paper and glass, during the screening that separates 2D material from 3D material and are ultimately discarded as residue. MRF operators say UBC losses occur at multiple stages in the sorting process, adding that they are sending as much as 15 tons of aluminum cans per month to landfills.

Republic Services’ St. Louis MRF Manager Brent Batliner realized small pucks of aluminum were being separated with glass at the polishing screen. Those pucks were, of course, too big for the glass screen and so were being discarded as trash. When Batliner checked the MRF’s residue line, he saw that 60 to 80 cans per minute were being trashed. Republic’s St. Louis MRF processes 300 tons per day of single-stream material, 200 tons of which are from residential collections.

Seeing results

With the installation of the MRF’s second eddy current, Republic’s St. Louis MRF has recovered an additional 15 tons per month of aluminum.

Because the second eddy current is ejecting aluminum from the MRF’s glass residue conveyor that is loaded with small pieces of debris, Batliner says he has been able to sell this material for 10 cents less per ton than the truckload per week of bales that are recovered by the MRF’s original eddy current.

But he says the investment was worth being able to recover the additional 30,000 pounds per month. The material recovered from the second eddy current separator is worth less because of its smaller size and the presence of other debris.

“Look at your trash line and count the cans,” Batliner advises MRF operators. “We’re getting crushed cans, pieces of cans and smaller aluminum cans out of residue and into bales.”

In addition to a second eddy current, Republic’s Seattle facility installed optical sorters on its paper quality control lines to further clean its paper. A secondary benefit of those optical sorters is that they are helping to recover additional aluminum that’s embedded in paper and that performs as if it were 2D material rather than 3D material during the sorting process.

“Look at your trash line and count the cans. We’re getting crushed cans, pieces of cans and smaller aluminum cans out of residue and into bales.” – Brent Batliner, manager, Republic Services’ St. Louis MRF

As a result of this additional optical sorting equipment, Republic’s Seattle MRF is diverting nearly an additional truckload of UBCs per month.

As the Republic MRF in St. Louis did, the Waste Management MRF in Elkridge, Maryland, also installed a second eddy current on the glass discharge line of its sorting system. The company had identified that small, crushed UBCs could fit through the gaps in the sizing screen, ending up in the residue.

After the installation of the second eddy current, that facility saw an increased capture rate of about 15 tons per month of aluminum.

Mike Taylor, director of recycling operations at Waste Management, says, “Retrofitting the second eddy current to fit on the glass discharge line wasn’t easy, but it was worth it to capture the material.”

Aiming for high quality

With high-quality material in mind, Eureka Recycling installed several upgrades to the nonprofit’s Minneapolis MRF in 2016 to assist in better separation of paper from containers. Single-stream collection and the compaction of collected material made it increasingly challenging to keep containers out of paper grades and vice versa. Eureka’s single-stream MRF is capable of processing 75,000 tons of recyclables annually.

Kate Davenport, co-president of Eureka Recycling, says, “We saw an increasing number of flattened aluminum cans and plastic bottles in our paper, so we worked with our equipment vendor to install additional screens and ballistics as well as a bigger second eddy current. This helped to reduce the containers in our paper grades by 50 percent.”

She continues, “Because of our philosophy around high material quality, we had already made the investments in equipment to address the increased demand for material quality coming out of National Sword,” she says.

The company’s second eddy current separator, supplied by Machinex of Plessisville, Quebec, further removes aluminum from the paper and increases the recovery of that high-value nonferrous material.

For Eureka’s MRF and those mentioned previously, installing a second eddy current has significantly increased the amount of aluminum they capture. Aluminum’s high value means that each and every can should be correctly sorted, baled and sold.

The author is the former vice president of sustainability for the Can Manufacturers Institute (CMI), Washington. She recently transitioned to the American Beverage Association, where she is senior director of sustainability. For more information on the CMI, visit www.cancentral.com.