Increasing throughput and turning out a marketable product are major challenges in sorting commingled recyclables. New equipment makes it more cost-effective, but planning is key.

By Penelope Grenoble O'Malley

Single-stream collection, which has been an on-again/off-again trend in the recycling industry, seems to be making a comeback, and some insiders predict that commingled collection of recyclables will be the standard in the future. Michael Benedetto, vice president and owner of TFC Recycling in Chesapeake, VA, remembers that when he went single stream in 1997, his company was the second in the United States to install a system. Today, he estimates, there are some 90 such operations. Benedetto took the plunge when the City of Virginia Beach, VA, issued a request for proposals for single-stream automated recycling collection, processing, and marketing. TFC Recycling currently collects from half a million households in Virginia Beach and operates four processing facilities that handle 11,000 tons a month.

One aspect that makes single stream so attractive is that properly operated, it reduces collection and personnel costs and can help achieve higher diversion rates. "Municipalities and waste haulers are taking an in-depth look at picking up a commingled fiber and container stream as a way to reduce overall operating costs," says Bob Marshall, general manager of Machinex Recycling Technologies in Pickering, ON. "Benefits include easier participation for the customer, a single tipping floor, and one residue stream to manage. Some of the skepticism about the process relates to reluctance from paper mill buyers, increased residue, additional capital costs, and perhaps an attitude of ‘It didn't work before so it won't work now.'"

From his point of view, John Willis, vice president of sales and marketing for CP Manufacturing in National City, CA, says the decision to go single stream is a no-brainer. "When you can pick up recyclables at the same price you can pick up garbage, when you can process the material at a lower cost than with manpower and you can get better diversion rates, what would you think?" But he warns that in a single-stream system, much of the onus falls on the processor. "The municipalities want the diversion, the haulers want the low-cost pickup, and the processors need to be able to make the municipalities and the haulers and the mills happy." Can they do it? Willis thinks so, with the right planning and equipment and perhaps a little additional cooperation in the markets. "With single stream, you can't do business like you did before, and the big thing to remember regarding equipment is no matter who the manufacturer is, everybody's system has changed from three years ago."

Benedetto describes the liabilities of one early system that he investigated. "Greensboro, North Carolina, was processing single stream by running the material across a conveyor belt and pulling out what they could–a positive rather than a negative sort. They basically had conveyors going around in circles, and the last belt would either divert the material to the compactor for trash or what was left for another go-around. Obviously they had some very high residual rates." The system Bulk Handling Systems installed for Waste Management in Dayton, OH, convinced Benedetto that single stream could work. "We saw the way the disc screens were separating out the material and decided to go with BHS. At that time, Bollegraaf also had experience with disc screens, but they weren't installed in any facilities in the US."

Cautious Enthusiasm

Despite enthusiasm from equipment manufacturers, Nat Egosi, president of RRT Design & Construction in Melville, NY, sees single stream as anything but a panacea. "We advocate single stream only if the customer has the opportunity to reap the benefits of the savings on the collection side. The people who have difficulty realizing the savings are people who don't control the collection, and while it's been proven the amount of material recovered goes up probably 40% with single-stream collection, the quality of the sorted material goes down." To make single stream work, says Egosi, you have to know what you're working with. "First you have to know how the material is being collected because this will help you understand the amount of trash and garbage that's going to be in the recyclables [generally about 15% to 20% with automated as opposed to manual collection, mostly from residents depositing trash in the wrong cart]. Then what are your recyclables going to be? Are you going to be sorting mixed paper–everything from junk mail to phone books, cardboard, magazines all the way up to newspaper–or will it be some variation of all of these? Will glass be included? Once you answer these questions, you can design and lay out your system.

"Fundamentally you're going to have an initial manual sorting to remove things that should not be there in the first place, followed by screens that will separate the paper and containers from each other, then two separate processing areas–one to sort paper and the other to sort containers," Egosi continues. "The priority here is you have to have screening equipment to separate the containers from the paper, which is unbelievably uneconomical to do manually. Which goes back to my initial question: Depending on your mix, you'll either be sorting news negatively, letting it continue and only removing the contaminants, or positively by pulling out what you want. Sorting containers can involve a lot of handpicking with magnets and eddy-current separators or it can involve sorting the light containers from the heavy aluminum, steel, and glass; in any case, this part of the operation is very similar to how any two-stream MRF [material recovery facility] is run."

More Than Meets the Eye

Egosi agrees that increasing throughput and decreasing personnel costs are "huge drivers" in developing materials handling systems for single stream: "If you have an existing plant and you're doing two shifts a day, with single stream you can cut that to one shift, and every single penny of those savings goes into your pocket." He also notes that reducing landfill costs and increasing diversion rates by increasing the amount of recovered material is a motivator in states such as California, where there's a strong diversion law, but not so much so in New York, where landfilling is mainly a function of economics.

But Egosi thinks markets aren't factored in as they used to be. "Most private-sector and municipal people disregard the markets as a basis for their investment decisions. When I was building facilities 10 years ago, the markets were the first things on people's minds. They were always thinking the markets and how they would help pay for the facility. Today most municipal officials and most private-sector firms look at the market as supplemental. If the markets are good, it will be two years before they start getting payback instead of three; if they're bad, maybe it'll take four. Unlike personnel costs, markets are a variable you can't control."

Although markets might not be a consideration investmentwise, product standards are prime decision-making drivers, especially in the paper industry, whose mills have strict requirements covering both product quality and contamination. "The kind of equipment you buy depends on where you expect to sell what you sort. Is your market for mixed paper or is it for something that approaches number-8 news?" asks Willis. "Can you sell news, mixed paper, and OCC [old corrugated cardboard]? Let's face it, if you get your news from the curb, you're going to get a better product than when you mix everything together, so in single stream you're going to need a bigger capital expenditure to get the equipment to produce a quality product. You want to know that the equipment you're planning to install will separate all the glass away from all the fiber; you want to know you can give the mills a product without a lot of cardboard or chipboard or carrier stock."

Is quality a function of better equipment or additional sorts? "Mainly it's the equipment," Willis maintains. "The better job the equipment does at separating the material, the fewer times you have to look at it and the less hand-separating you need to do. Certainly if you run the material through enough and you put enough sorters up there, you can get any quality you want. But there's a number where you'll make money, and you need to be below that number."

Benedetto agrees. "There's no doubt single-stream material can create additional challenges to meet the market specifications. Once you mingle containers and paper together, there's always a chance containers will go through and be mixed with paper. We made modifications in our original system to increase throughput and to get that better quality of product. This involved replacing our original screens with Bollegraaf and eliminating some of the items on the container sorting line, including the air separator and the glass separators." (The people at Van Dyk Baler Corporation, who sell Bollegraaf systems in the US, point out that the screens it supplies with its Bollegraaf systems are actually made by Lubo, a Dutch company for whom Van Dyk is also a US distributor.)

In Portland, OR, glass is not processed with the rest of the stream. "The biggest reason for keeping the glass separate is that the recovery rate is higher with the glass out of the stream," relates Jay McCuistion, plant superintendent for Oregon Recycling. "Our biggest concern is the market. We have been given quite a bit of feedback from some of our local mills as to the adverse effects of glass on their processing. I'd like to see glass go to a drop-off location. It's a costly material to separate, not only from the handling standpoint but also because it's the most abrasive on equipment. It escalates our repair costs considerably." McCuistion's advice is to use as many screens as possible when separating glass. He estimates that if single stream comes on-line, he'll add a fines screen to his existing system.

Willis thinks a lot of people who are pessimistic about glass don't understand it. "If you have a good local market for glass, then put it in your system. If your only market is 250 miles away, then you're probably better off landfilling, despite the cost. It's your choice. Is glass harder to handle? Yes. Do you need more equipment? Yes. Do you need to think about how you're going to handle glass when you buy equipment? Yes."

A Case in Point

At 250 tpd, Trinity Waste Services in Plano outside Dallas, TX, enjoys the largest municipal recycling contract in the country. "We have 11 different products we sort," says Plant Manager Frank Sienkiewicz. "We sort cardboard, newspaper, office waste, mixed paper, phone books, ferrous and aluminum cans, HDPE [high-density polyethylene] natural and HDPE pigmented, PET [polyethylene terephthalate], and glass. I have a unique system in that I not only incorporate single-stream collection, I put commercial in the same line, so I'm doing commercial cardboard along with single stream. This developed because we had a line that was just doing cardboard and a commingled line that was just doing commingled. So I talked to the people at Bulk Handling, and their engineers came down here and figured a way to develop a single-stream system and incorporate both."

The system Sienkiewicz describes is almost two years old and includes five subgrade pit conveyors/incline conveyors, five sorting platforms, five disc screens, three balers (Logemann Brothers), nine bunkers, three perforators, one cross-bolt magnet separator (Industrial Magnetics), one air classifier, one eddy-current separator (Walker), one glass-bottle breaker, three trash compactors, one glass/crushing/sanding machine (Glass Aggregate Manufacturing and Engineering), six sort conveyors, and 14 transfer conveyors (all conveyors, screens, etc. are BHS; other equipment includes rolling stock such as forklifts, loaders, and trucks). The material is processed as follows: From the tipping floor it's pushed into a pit conveyor that rises to a presort platform, where sorters pick trash from the stream and drop it into chutes leading to a conveyor and then to a packer. The presorted material falls onto an OCC disc screen that separates the OCC, which is then conveyed to a baler. The unders from the screen pass onto another manned sort station, where more trash is removed, and then to a 2-in.-minus disc screen. The unders from this screen go to the trash compactor, and the overs material goes to a sort platform where sorters remove OCC missed by the OCC screen, which is dropped into a bunker for future baling on a two-ram baler. The material then drops into a disc screen that removes paper. The clean paper is deposited on a sorting conveyor, and up to six people remove any residual contaminants and high-grade paper and deposit them into chutes that lead to bunkers. The commingled unders, which are likely to have residual broken glass and fiber, are passed over two more screens, one to remove the rest of the fiber and the other to target the _-in.-minus particles; a cross-belt magnet removes all ferrous material and drops it into a bunker. The commingled then passes through an air classifier, which separates the glass from everything else. The glass is stored in a bunker until it's passed to the glass-sanding machine, which turns it into ecosand, and the remaining commingled is sorted for three grades of plastic. The aluminum and trash that remain pass over an eddy-current separator, where the aluminum is removed and the trash is conveyed to another compactor.

Regarding how much the market influenced what he installed, Sienkiewicz insists that the end user drives the system. "If there was a market for coffee grounds, we'd be separating coffee grounds. To be serious, if a market developed for something we're not producing now, we would just put in another piece of equipment or another screen or sort station. The idea would be to determine whether it was most cost-effective to pull off whatever it is by hand and make a positive sort or get a machine to do it and do a negative sort. It depends on how much you're getting for the product, whether it's worth buying a piece of equipment. There may be a market out there that takes any grade or color of plastic and therefore there'll be somebody who's pulling yogurt containers, say, but the people who want my HDPE natural basically want milk jugs. And when they say soda bottles, they mean they just want soda bottles; they don't care what number is on the bottom of the rest of it."

A system such as Sienkiewicz's is costly, but the good news is that many facilities currently operating a dual collection system might be able to convert to handle single stream. Benedetto explains, "Bollegraaf has a front-end system they install onto existing dual-stream systems. This does the initial sort so the material can proceed into the existing sorting operations. Installation requires reducing tipping-floor space, and the sort will not be 100%, so you have to have enough room to manually sort contaminants the front of the system doesn't separate out mechanically."

Willis cautions that whether a system can be converted depends on the equipment already in place and the amount of material to be processed. "Someone running 150 to 200 tons a day probably needs a whole new system. Someone doing 25 tons a day basically needs something to cut the fiber from the containers. For example, if the operation includes one of our big later-model container sorting systems, then all they would need is a front-end line to separate the news and mixed paper and get the containers to the existing container line. If they just have a straight pick line to pick containers and fiber off both sides, they're probably going to need a whole new system."

John Pausma is impatient with talk about markets and equipment and conversion. Director of recycling operations for Homewood Disposal in East Hazel Crest, IL, which collects and processes trash and recyclables for suburbs south of Chicago and processes material from other haulers, Pausma pushed for single stream and installed a new processing system two years ago. "We figured if we did it, all the rest of haulers would follow and we'd be able to tap into more material at our processing facility. Getting more material makes the system work. It's a big investment because, without a doubt, it makes it more complicated bringing in everything mixed all together. There are a lot more steps in the process, lots of different screens and conveyors along the way to get a product you can sell. But the fact is you're dealing with exactly same markets whether your collection is curb sort, dual, or single stream."

Homewood runs two shifts and processes about 300-350 tpd. Pausma converted an existing Machinex dual-stream system by adding the Bollegraaf front end. "After the material passes through the single-stream portion and gets to the dual-stream line, we didn't add anything. The only thing we did was widen the conveyors because, with this system, we can process at a higher rate of speed and the volume increased. We had to widen the conveyors so the burden depth wasn't [so] large that we couldn't sort. In general, the material we bring to the dual-stream lines out of the Bollegraaf front end is as good as or better than when we were doing dual stream. There's been very few quality concerns."

Pausma sells No. 8 news to mills in the US as well as in foreign markets, and he's making a couple of different grades of mixed paper, although he says generally there's enough news in the mixed paper that he sometimes sells it as No. 6 news. "It depends on how the system is set up. You can play with the settings, and this affects how much paper goes where, so you can really make almost all the paper go over the first two screens by flattening it out and changing the spacing or slowing it down. It depends on how you want to market it."

What's next? Maybe optics. "A single stream does not do 100% separation," points out Benedetto. "I haven't seen a system yet that can do the job we're looking for. We tested MSS's bottle sorting system, but it's costly, and we haven't seen it in operation in the kind of system we're looking for yet. What we want is to take our container stream, put in a glass-crushing system, a magnet to get rid of the steel cans, eddy current to remove the aluminum, and a system from MSS to sort out all the plastics and run the whole thing with zero people or perhaps one person for quality control." The MSS Inc. machine Benedetto researched sorts PET and natural and colored HDPE. The company's glass-processing equipment can be used to sort flint from the green and amber glass, and the company has developed an optical sorter that identifies and separates paper grades. Both Benedetto and Willis think that, in the near future, mills are going to develop the technology to handle different paper grades and there will eventually be a better understanding between the mills and materials processing operations about what's acceptable and how to produce it. Willis also believes we're on the cusp of a third generation of processing equipment.

Bob Marshall at Machinex offers some bottom-line advice: Make sure whatever separating equipment you buy is recent technology and proven. Be sure what you buy is versatile and easily adaptable to accommodate changes in material streams. The equipment should be easy to maintain to avoid high operating costs, and whatever system you buy should be designed to minimize labor costs. The design of the system should also be capable of processing all the recyclables you contract to receive, with enough sorting stations and storage bunkers. Whenever possible, adding a few extra of each can help accommodate additional materials that might be added after the initial program is developed.

"There's a difference between sorting and separating," says William Guptail of General Kinematics, a company that makes crushers and destoners. "Sorting refers to what goes on at manual picking stations. Separating is a process you generally do with screens and drum magnets and vibratory finger screens." As Guptail's distinction suggests, when it comes to single-stream processing, efficient use of personnel and equipment is the key to improving both throughput and quality. "Trash was originally collected manually," says Benedetto, "with a rearloader truck and one driver and one or two helpers. In many places this has been converted to automatic collection, which is where recycling has to go. Single-stream collection and processing are what we need to be efficient."

Penelope Grenoble O'Malley is a frequent contributor to environmental publications.

MSW - November/December 2002