With curbside recycling programs firmly entrenched across the country, the next big step involves effectively maximizing the recovery of high-quality materials.

By Lynn Merrill

Challenges Inside the Process
Suitable Selections
Just When You Think It’s Right
Keeping What You’ve Got Running

Across the country, from New York to Los Angeles, residential and commercial customers dutifully separate recyclables - paper, metals, plastics, and glass - from the rest of the wastestream. In some communities, either customers or the driver further separates recyclables into two or more materials streams. In many locales, a collection program may mean that up to three big trucks pound across the pavement in front of their establishment, making countless stops for recyclables, greenwaste, and refuse.

For some communities, those three trucks could be three too many with their noise, air emissions, pavement damage, and inherent danger to inattentive drivers and pedestrians. The longer each truck stops while the driver sorts recycling materials curbside, the longer someone has to tolerate potential negative impacts to his or her quality of life. In the narrow streets and alleys of various urban areas, it’s hard enough to get the trash picked up safely without causing unnecessary frustration to other drivers. Put a slow-moving, manual-separation recycling truck down the same street, and the result might be road rage.

With higher waste-diversion mandates clicking into place across the country, the need to maximize the quantities and qualities of recyclables collected conflicts with many community efforts at traffic mitigation and air-quality management. With these pressures, what are the options?

The solution to this vexing problem might be where the recyclables hit the conveyor belt, not at the curb.

Challenges Inside the Process

Separation technology has advanced significantly from the early days of hand-separation along a conveyor line. While glass and plastics separation continues to be complicated by colors, contamination, and composition, the technology to separate ferrous and nonferrous metals and fibers continues to advance, thus maximizing recovery of marketable commodities.

One of the most significant advancements in separation equipment is the use of star screens to separate containers from paper loads. The Norton Environmental Flagstaff, AZ, material recovery facility (MRF) uses these screens. "This facility has a series of star screens designed to separate the round materials from the flat," describes Steve Viny, president. "A star screen is a disc screen. Unlike the original disc screen, which was designed to be relatively level, this disc screen is inclined. The idea is that the discs are not perfectly round; they’re actually sort of star-shaped. They’re designed so that when the paper, which is relatively soft, falls on the stars, the surface of the stars propel that material forward. When a beverage container, which is more rigid, falls on the star screen, due to the incline it will fall backward on the star screen to a conveyor belt below. One of the negatives of the star screen is that any long object, like a belt, a hose, or a piece of plastic banding or metal banding, will wrap around the shaft of the star screen and damage it."

The facility uses handsorting to remove those items that can cause damage to the star screen. "In that first station, we take off the big cardboard, the bulk newspaper, and any objects such as film plastic or long, stringy objects that would damage the star screen," explains Viny. "We ask residents to take newspaper and place it in kraft bags so we can get a week’s worth of newspaper in one shot. Once we get past the star screen, the round objects go in one direction and the flat objects go in the other. Where the flat objects go, we do a negative sort in which we’re just grading up the paper and trying to get the best marketability for it. For the round objects, we’ll pull off our metals using overband magnets and eddy-current separators. What’s left is plastic, and we have a handsort to just grade our plastic."

Since the beginning, glass has been a commodity challenging the best of processing. Although highly recyclable, the need to separate it by color and the problems created by breakage continue to perplex. Its abrasive quality wears down collection and processing equipment. It also creates complications for maintaining the quality of other recyclables, such as fibers. Glass is such a problem that some states, including Wisconsin, passed laws prohibiting the co-collection of glass and paper. "We’re not allowed to compact glass and paper together in the same compartment," states Brian Jongetjes, president of John’s Disposal in Whitewater, WI. "Pretty much everyone in Wisconsin uses some type of compaction recycling equipment. I think in the beginning that it was probably correct because there definitely is a concern about glass in the paper. A lot of our paper goes to tissue mills where they make hand towels, and if there was glass in there, that could be bad. You break a lot of glass when you’re constantly dumping it on an empty steel hopper."

Many processing facility managers would prefer not to process glass because of the problems. One solution, however, is to eliminate the need to separate glass by color and to minimize handling. Both the Norton Environmental Flagstaff facility and Trinity Waste Services’ Plano, TX, facility now see the light through the glass. "Glass is incredibly hard on anything," notes Don Smith, general manager for the Plano division of Trinity Waste Services. "You’re sandblasting things with it, so it’s tremendously hard. We’re looking to make some changes in the glass processing. We are now moving toward a glass crusher with our new line. We will no longer sort it by color, and we’ll crush it to what’s called ‘eco-sand.’ You can basically reach your hand into it and not cut your hand - it’s that fine. They use it for drainfield media and composting."

Suitable Selections

Selecting the correct separation equipment involves understanding the costs associated with acquiring and maintaining the equipment and how the particular piece of equipment will help increase the efficiency of the separation process. Just because a particular system has certain technological features doesn’t necessarily mean that it is the right piece of equipment for the operation.

Regional Waste Systems is a not-for-profit, nonstock corporation owned and controlled by its member municipalities. The 47,000-ft.² facility, located in Portland, ME, processes 60 tpd of recyclables collected within the 31 towns and cities that the facility services. "We recently bought a bunch of equipment," says Eric Root, director of material recovery. "We first identified the manufacturers of industrial-grade equipment - big, rugged stuff. You want to see what their success record has been in a couple of locations and you want to look to see if it is rugged. Is it repairable? Does it include components that are available only from the manufacturer? Is this normal industrial material? For example, if you’re buying a conveyor, are those rollers off-the-shelf stuff or do you have to go back to the manufacturer? Then you bring the manufacturer into your operation and talk about what you’re really trying to do. One of the surprises to me was how disappointed a number of people were who didn’t do that. You really have to have a lot of interaction with the designer so he knows what you’re trying to do."

Working with the manufacturer turned out to be advantageous. "We changed design in midstream because, as we came to understand what we were trying to do better and how the screen worked, it was obvious that we were looking for the wrong thing," notes Root. "For us, it was a long and iterative process involving the manufacturer. Yet every bit as important was our understanding of what we were trying to do. We had to understand the limitations of their machines. We were probably three-quarters of the way through the procurement process. We spent a day [with the manufacturer], and he said, ‘You know, you’re really on the wrong track.’ He changed the kind of screen he was proposing to deliver to us, and we changed what we were telling him we wanted based on his feedback. We got a screen that does a very good job, but I think if we hadn’t spent the money to fly him out here at our expense, we’d have been very disappointed. You need to spend the time to understand what you’re doing. The longer you work at it, the more you tell them, and the more you pick their brains, the more you’re going to like what you get from the manufacturer."

Just When You Think It’s Right

One of the biggest challenges facing MRFs is that just when it seems as if the markets, materials, or systems are going to settle down, something new pops up to disrupt the best-laid strategy. With market-price fluctuations, it’s advantageous to have flexibility in the type of materials that can be processed through the facility. For example, if the facility currently processes one grade of paper and, for an additional amount of high-grading, can achieve a significant increase in market revenue, then it’s beneficial to have equipment that can accomplish this shift in processing.

Another challenge, especially in the area of containers, is the introduction of new resin types or colors that can affect the value of the material. Recent debate about the introduction of brown plastic bottles for beer has caused processors to pause and reconsider. "I know the PET people are worried about the new brown PET bottles," observes Jongetjes. He speaks of one manufacturer of carpeting that uses recycled PET in the manufacturing process. "They don’t know what’s going to happen when the brown bottles start going through because they’re set for green and white. There’s a little bit of blue and they seem to be able to handle that, but if there’s a huge amount of brown, that potentially could hurt them. Right now, there is a large demand for that PET material, but that might change. You have to be prepared to change what you’re doing. I would like to think that 20 years from now, this will all be settled down and run fairly smoothly."

Changes in collection approaches, especially a shift from multiple separation at the curb to commingled collection, can result in new challenges inside the MRF. "I believe that recycling is going to a larger scale," says Terry Horst, general manager of Minnkota Recycling in Fargo, ND. "It’s going to go more regional, and facilities like mine will need to have a larger regional appeal. To transport materials regionally, you need to transport volume, which means you might have to commingle materials more than you’ve done in the past. Our facility was designed for source separation at the site or at the customer’s location. Do I have to gear up my facility to handle more commingled material? I believe I have to. The City of Fargo is going to be doing a curbside pilot program starting in September, and they’re going to be commingling some materials that I currently don’t sort."

While the addition of new equipment can increase productivity by automating some of the separation functions, the flexibility of adding manual-sort positions is more controllable, states Horst. "Keeping our operation cost low is always a challenge, and getting enough labor has always been a problem, let alone getting enough adequately trained labor. You can make investments in star systems and eddy currents, but the one thing you can say about labor is that it is a controllable factor in business. You can increase your labor or you can decrease your labor, but once you put in the expensive source separation equipment, it’s a constant depreciation item on your P&L (profit and loss)."

Even with automation, it’s not foolproof. "When you automate, you can never get 100%," points out Viny. "Our eddy-current separator is completely automated. We can set the eddy-current separator so that we get 100% aluminum with no contamination whatsoever. When we do that, we’re not going to get 100% of the aluminum. Some of it’s going to get by. We could also adjust the eddy-current separator so we get all the aluminum and none of it gets by. By doing that, we’ll end up with some contamination in the aluminum. Or we could adjust it somewhere in between. That same logic applies to virtually anything you automate. When you automate, you have to make assumptions, and you know we don’t live in a perfect world. There is no better way to do things than to have some human element. There are some things that automate better than others. I think automation is important and I think it’s something we’re going to see in more and more MRFs. I think it’s good, but I think there’s always a place for the human element. You’re never going to be able to have a machine that is a substitute for a human brain, eyes, and hands."

Keeping What You’ve Got Running

No matter how much of an investment is made in equipment, without a regular maintenance program, even the best state-of-the-art system will be reduced to junk. For Viny, maintenance systems are crucial. "One of the things we’ve automated that we’re pretty proud of is our control system," he states. "We took each equipment manufacturer’s scheduled maintenance and programmed that into our controller. It prompts us to perform the maintenance, and it sets an alarm when a scheduled maintenance is to be performed that only the plant manager can override. The idea is that maintenance gets done and the plant manager will not hit the override until he’s visually inspected it to make sure the work’s been completed. Those are the kind of things that increase reliability."

Ensuring that the company selling the equipment has the capability to provide technical support is also part of the equipment selection process. "It’s really essential that a facility has a very competent maintenance person who is quite capable with hydraulics and mechanical equipment," advises Horst. "We do some of our own work, but if I need to get somebody up here, [the vendor is] very capable of providing next-day service to us if need be. Over the years we’ve found the means to get over some of those hurdles. It’s all about having some experience under your belt."

That experience might just be what is needed to carry the separation-systems technology inside the building through the latest challenges caused by new collection strategies, new materials, and increasing costs. "You definitely want to be prepared that this is not going to be it," recommends Jongetjes. "It’s going to change, so you’ve got to be a little careful, be willing to throw some stuff on the scrap heap. It’s still a new frontier. I thought it was settling down, but now they started talking about mixing everything in one single stream, and that’s going to throw a bunch of stuff on the scrap heap again."

Lynn Merrill is director of public services for the City of San Bernardino, CA.

MSW
Nov/Dec 2000