Sort & Count

The right sorting equipment is critical if recyclers want considerable profits to count.

In densely populated urban areas, such as Chicago, Cleveland and other major cities, municipalities are pushing waste haulers to maintain recyclable collection services, but to keep it simple and single. That is,simple for the general public that wants to continue to recycle, but does not want to do the sorting at home. Instead, households are commingling their recyclables into a single stream, placing them on their front lawns and having the waste hauler pick them up, often to be placed in a compacting truck.

However, what is simpler for the household, and the hauler, becomes harder for the recycler. This trend toward commingled collection has forced recyclers to build new material recycling facilities (MRFs) or to overhaul existing ones in order to handle the single stream. One company familiar with this trend is Waste Management Inc., Houston, with offices, plants and operations throughout the U.S. Waste Management has a unique perspective because it is a cradle-to-grave recycler that does the collecting, hauling, processing and reselling of municipal recyclables.

“Most single-stream MRFs are operating due to requests made by the local municipalities where the recyclables are collected,” says Jerry Hawk, Southeast regional manager for Waste Management’s material marketing group in Norcross, Ga. “But we, the collector and processor, have to make sure that the volume is there first in order to invest the millions of dollars in mechanical sorting equipment required for the MRF to be profitable.”

Scott Jable, Midwest regional manager of Van Dyk Baler Corp. in Chicago, agrees, but also contends that there is a benefit for the hauler, too. “Half of the push is by the consumers who commingle recyclables at home,” he says. “The other half of the push is from haulers, because it is easier for them. Route times are decreased, labor is decreased, and they can use trucks that are less expensive to operate.”

Once the volume is in place, it is up to the MRF operator to employ an efficient operation in order to process the recyclables. Generally, in single-stream MRFs the process involves some manual sorting/inspection, mechanical screening, the use of magnets and possibly some optical devices. For shipping end products, balers will also be needed.

Get The Paper Out First

Screens, trommels and other mechanical devices normally are found at the front of a single-stream operation in order to separate out the paper and then get it out of the way. From the tipping floor to the conveyor, many single-stream material recycling facilities use employees to ensure bags are broken and discarded and other debris is removed from the mix. Some may employ bag breakers if blue plastic bags are commonly used by households to gather recyclables.

While screens and trommels are still popular for separating material of varied sizes, problems with clogging can limit their effectiveness. Other devices, such as finger and vibrating screens, improve recovery rates, and rotating star or cam screens are used in processing a number of different materials streams in all recycling segments.

Last year, Waste Management installed a new sorting line at its MRF in Oakwood, Ohio. The facility serves several communities in northeast Ohio. The Oakwood plant has been performing some type of recyclables sorting since 1992. According to Jamie Yommer, plant manager at Oakwood, the single-stream system involves approximately five major stages. The first is an initial sort by people to remove any unwanted garbage that made it in the stream, plus the hand sorting removes any cardboard. Normally, cardboard is not a high-volume item collected in municipal recycling programs.

The second stage is a Lubo (mechanical) screen that splits the main stream into two – paper products and non-paper. The paper stream goes through another mechanical sort (stage three) combined with quality control workers who monitor and help where needed. The paperless stream now only has plastic and glass containers and tin and aluminum cans, plus other ferrous and nonferrous recyclables.

The fourth stage involves an overhead magnet that pulls out any ferrous scrap, and the fifth stage is an eddy current separator for the aluminum cans. Yommer says that the system is working well. Waste Management switched to the single-stream concept at the plant simply because the general public is unwilling to sort recyclables at home, according to Yommer. “They will take the time to separate the recyclables from the garbage, but will not take the time to separate those recyclables further into specific categories,” he says.

No matter how many stages a MRF employs, the first stage or stages are geared toward getting the paper out, according to Hawk. “First, if your customers use plastic bags, you have to have employees breaking open bags or bag breakers – then you have to have some sort of screen to get any grit out,” he says. “Next, focus on sorting the paper. At our Birmingham, Ala., plant we have a paper-sorting device called the Banana. I think we are the first company to own one in the U.S. It has rotating fingers that bounce material upward while the whole device is set on an incline.” Hawk likens it to a shaker table used in the mining industry – as the lighter material is bounced up it eventually goes over and forward; however, the heavier (denser) material moves downward and falls through the screen. “Right now we are trying to determine the optimum angle for our sort,” he says. “I guess that is why it is called the Banana, because it has a slope like a banana.”

The French Banana Screen is made by Dutch equipment maker Lubo and marketed in the U.S. by Van Dyk Baler Corp. The name derives both from its shape and from its first installation, which was in France.

Jable of Van Dyk says MRF operators should look closely at what type of paper they are screening for. “I think what the MRF operator has to decide on the onset is whether to screen for #6 or #8 news, because there are different screening technologies for each,” he says. But regardless of what route is taken, Jable says to get the cardboard out of the stream first either manually or by screening. “Star screens are ideal for this,” he says. “Once the OCC is out, get any trash out, such as plastic bags and light items.” Jable recommends a series of screens to get all the fiber out of the stream. 

Moving bottles

Electronic imaging, one of the newest additions to the family of sorters, has been used in the recycling industry for not much more than a decade. These types of sorters are used mainly to separate plastic bottles by resin and/or color, and glass by color. Imaging includes infrared sensors and optics. When a sensor reads or identifies the resin or color characteristics of the bottle, the data is fed to a computer that immediately locates the position of the bottle on the conveyor and triggers a pinpoint blast of air from a pneumatic system that removes the bottle from the stream.

The challenge in this type of sorting is not the way the material is sorted, but the speed at which this sorting can occur. Advances over the years have made optic sorting better suited for high-volume material recycling facilities as these systems have improved to handle higher throughputs. Placing the plastic sorter toward the end after all other recyclables are removed from the stream increases efficiency.

“The optic systems definitely should be after the paper sort, either prior to the magnet sort or after, depending on the setup,” says Felix Hottenstein, sales director of MSS Inc., Nashville, Tenn. “[It can be ideal for] some plastic sorting equipment that is designed to sort only plastics into PET and HDPE streams, or to color-sort plastic bottles.” MSS’s Sapphire system uses eight switches – each one corresponds to a different type of plastic or carton (only one switch can be employed at a time). The company’s new Aladdin plastic sorter is used primarily to sort PET or HDPE and can sort out in three separate batches of color. Hottenstein notes an Aladdin plastic sorter is used at a MRF owned by Todd Heller in Northampton, Pa.

However, adding an optic sorting device may be cost-prohibitive at some MRFs. “Most single-stream MRFs won’t have that much plastic – maybe a ton or two an hour, and two people can manually sort that amount without a problem,” says Jable. “The majority of single-stream MRFs I work with use manual labor to sort the plastics, which then can be baled and shipped.”

Waste Management ships its commingled plastic bottles to PREI, currently located in Youngsville, N.C., (PREI will soon be moving south to Raleigh, N.C. to consolidate with its glass operation and a new MRF.) PREI is a subsidiary of Recycle America and owned by Waste Management. “We found that it was more cost effective to sort out our plastics as a commingled stream, then ship them to PREI, which does the final sorting by resin and color,” says Hawk.

PREI recently installed new proprietary equipment that has only been operational since last December. “It’s equipment that was designed specifically for us, and I can’t tell you much more than that,” says Tom Draney, general manager of PREI. He did say that PREI’s new plastic sorting system has a throughput of about 5.5 million pounds (2,750 tons) of plastic containers a month. The system performs a resin sort (PET and HDPE), then a color sort into four streams of natural HDPE, color HDPE, clear PET and green PET. After the sort and some quality control by employees, the plastic streams are then ground into flake, according to Draney. The flake is sold to end users for carpet fiber, and to SEC, Winchester, Va., which turns the resin back into bottles for Coca-Cola. “It’s the only process I know of that turns commingled plastics into bottle-grade plastic,” says Draney.

PREI gets about half of its recyclables from Waste Management MRFs, and the rest from other companies. “An independent MRF operator that has a single-stream plant has to seriously analyze the profitability of sorting the commingled plastics in-house or shipping them baled to a secondary processor like us,” says Draney. “I would say that if the MRF is getting predominantly one type of plastic, then it probably makes more sense to sort in house, but if the plastic stream is mixed, then they can ship it to us for follow-on processing. (Draney welcomes new customers and says those interested should call PREI in Youngsville, N.C., for a quote.) 

 Hottenstein also says that the MRF operator may have to add equipment after the fact if the incoming stream changes because of a change in public buying/recycling habits. “One MRF had to install our glass sorting system because they found that they were getting a higher volume of glass than expected, and half of that glass was flint. Combined with the high tipping fees that the MRF was getting, it made sense to install a glass sorting system.”

A MRF in the Tidewater region of Virginia had a similar situation. “They installed a special system that breaks the glass into a commingled stream because there is a market for it,” says Jable.

Magnet Configurations

Any single-stream MRF that expects to be cost effective must employ magnets to sort the ferrous and aluminum scrap. Magnetism currently is the only way to do this without manual sorting. In single-stream configurations, the majority of the magnetic separation occurs toward the end of the sorting line. This is because it is easier to pull ferrous material out of the stream after bulky items such as cardboard and paper have been removed. Once all ferrous material is removed by a magnet, the remaining contents of the stream is passed over an eddy current separator that bounces out the aluminum scrap, consisting mainly of cans.

Magnets and eddy current separators are the mainstay of ferrous and nonferrous processing in any MRF. Magnets used for this purpose are either in an overhead configuration or underneath the conveying belt in a head pulley. Either type of magnet can be permanent or electromagnet. The main benefit of the electromagnet is that it can be turned off when it is not needed or to conduct maintenance. The primary benefit of the permanent magnet is that it does not need a power source.

Overhead models have their own mini- conveyor, or belt, with cleats so when ferrous material is pulled out of the stream, the action either drops the ferrous on another conveyor in a cross-belt configuration, or beyond a splitter in an in-line situation. These magnets are usually referred to as self-cleaning. At Waste Management’s Oakwood MRF in northeast Ohio, an overhead magnet is used toward the end of the single-stream line.

Because the magnet is positioned above a moving stream of scrap, the magnetic field has to be strong enough to pull ferrous material up, against the pull of gravity, and be able to reach down into the bottom of the stream trough. This is why positioning the overhead magnet toward the end of the stream is key to a successful operation—because there is less overall material to get in the way.

In addition, once the bulky recyclables are sorted out of the way, the MRF operator can position the overhead magnet closer to the stream, making it more effective. “A MRF that can position its overhead magnet within 12 inches of the line can use a permanent magnet, which is generally less expensive,” says Don Morgan, product manager of Walker Magnetics, Worcester, Mass. Morgan, who is based in Milwaukee, Wisc., and has more than 50 years in the magnet business, says that “if the magnet has to be placed higher than 12 inches, then the MRF should switch to a more powerful electromagnet that can generate a field that will reach down to the stream.”

Overhead magnets can pull out long or large pieces of ferrous scrap, but there could be problems with trapped metal. Pulley magnets can eliminate the trapped metal problem, but long pieces of ferrous could carry through, or ferrous could get trapped on top of a nonferrous or nonmetallic piece. The most effective systems will use a combination of the two, according to Morgan. He adds that it is better to have the eddy current separator after the magnets because any ferrous material mixed in with the nonferrous cans can cause complications. 

The author is a Recycling Today contributing editor who can be contacted via e-mail at mdphillips@core.com.