The MRF, designed to handle the wastestream swiftly and efficiently, keeps the piles at the tipping floor–and the cost of handling waste–to a minimum.

By Joseph Lynn Tilton

People generate waste. The more affluent a society, the greater the amount of waste–and the greater the call for somebody to do something. This brings on regulatory pressure, which drives up the cost of handling waste. The market response is to find a solution that reduces the cost of dealing with that waste, while satisfying both customer and bureaucrat. Enter the material recovery facility, traditional or mass-burn, which is designed to handle the wastestream efficiently and speedily, keeping the piles down at the tipping floor, lest the stream turn into a flood.

A Family Operation

In Whitewater, WI (population 12,626), John's Disposal Service processes 50 tpd of recyclable waste from 35,000 homes in a four-county area. The operation runs 11 hours a day, five days a week, with Saturdays added when tipping-floor piles start growing.

Founded in 1969 by John Jongetjes, this operation lives solely on collection fees. The corporate staff includes the founder as secretary, with wife Marge handling the paperwork from home while sons Brian and Ron supervise the plant operation.

"Dad bought a truck in 1969 and started collecting waste for his own burning landfill," explains Ron. "Six months later no more burning was allowed, so he started burying it on a 50-acre site. Brian and I joined when we each finished high school. By then we could see problems ahead with our landfill filling up, so we bought a baler and started pulling cardboard out while the trucks were dumping."

At first they shredded it and sold bales to farmers for animal bedding. "We've not been making animal bedding for several years, but we still find homes for all the paper. We're also recycling Class 1 to 7 plastic containers, glass, tin, aluminum, and scrap iron. We want to save everything we can."

While the goal is to have a plant that's fully automatic, it's mostly a shop-built operation. The only commercial equipment in handling the stream is a magnet and an eddy current, both from Dings. An old furnace blower adjacent the magnet helps separate light containers from heavy glass.

Ron reports that picker vigilance helps keep the belt rip-free. "If a homeowner throws away a pipe, the magnet can catch it by one end and the other can cut the sorting belt. We have four sorters right in front, and they keep an eye on the magnet. Still, about once a year something will get caught. Before that we had five times as many rips, and downtime for patching was as long as two hours."

The people at John's Disposal Service also service the eddy current every day. "It takes just 10 minutes a night to clean, grease, and check for any bottle caps stuck to the pulley. We'll find something about once a week, but downtime has never been a problem," Ron maintains.

Another help for them is their supplier headquartered about an hour to the east in Milwaukee. Harold Bolstad, sales manager for the Dings Company Magnetic Group, points out that today's electromagnets can be designed to fit any size or type of operation and can utilize either electromagnets or permanent magnets, depending on the particular application. "Magnets can pick up pieces of ferrous metal as small as bottle caps or as large as manhole covers. By mounting the magnet just 2 to 3 inches over the top of the wastestream, you can maximize efficiency of metal separation."

Self-cleaning overhead magnets use a cleated rubber belt to move material away from the wastestream after it has been attracted to the magnet surface. The cleats continue to push away the attracted metal, preventing it from rolling and blocking the magnet surface. "Magnet separation comes into play again at the end of the sorting line, where an eddy-current separator helps separate aluminum and copper and other nonferrous metals. The idea is to separate these metals into clean products for further processing."

Bolstad notes that regular maintenance is an important factor in keeping a magnetic separator running. Typical maintenance includes lubricating bearings and keeping the belt tracked and free of trapped material to prevent excessive wear. Also, maintaining a proper oil level is key to extending the life of an electromagnet.

"Problems usually come when the oil has changed to sludge because it's not been changed in many years. In this case, a magnet will have to be taken out of service for repair, which could take anywhere from several days to several weeks. Also, moisture inside the magnet box will tend to break the oil down. Most magnets have a one-way breather valve that allows air to escape from inside the magnet, but it prevents air from entering the box when it cools down. It is important to check that the breather is in place and functioning properly," Bolstad explains.

"Magnets recover 90% to 95% of material going underneath. This helps produce cleaner wastestreams to more efficiently recycle different materials."

Mass-Burn and Ash Success

Don Wolfram, vice president of Resource Recycling LLC, agrees. His company, headquartered in St. Petersburg, FL, has ash-processing and metal-recovery systems in six locations. "Being owner-operators, we're always concerned with the ease of operating a plant. To this end, we went out and found the best machinery available simply to avoid downtime and maintenance costs. In our St. Petersburg plant we process 600 to 800 tons of ash every day from the county's mass-burn waste-to-energy facility. When you're running 24 hours a day, seven days a week, you need equipment that will operate 24/7.

"Our machinery involves conveyors, metering pans, finger screens, in-feed conveyors, shredders, drum magnets, eddy-current separators, and sorting pans." This makes possible separating ferrous and nonferrous metals from other trash. The wastestream is first burned for energy recovery, then the metals are recovered from the residual ash. It is possible that steel from within the trash can head back to a steel mill in just an hour.

"A ton of garbage has the same BTUs as a barrel of oil," Wolfram continues. "The facility uses about 5% to 10% of the power generated from the mass-burn plant internally. The power portion of this facility produces about 72 megawatts of energy daily, which is enough to power about 100,000 households. With mass burn, anything goes. A German engineer was looking at an American ash stream when an engine block went by. He said, ‘Ya, what every American housewife throws away!'"

Wolfram notes that the operation utilizes mostly conveyors and screens. "Over the years we've tried several screen types. For our rough cuts we use an open-ended finger design from General Kinematics out of Barrington, Illinois. The screens cut out material larger than 2 inches, while material less than 3/8 inch goes through our conventional aggregate-type screens, which we get from either Tyler out of Gastonia, North Carolina, or Diester out of Fort Wayne, Indiana."

Resource Recycling LLC processes almost all of the waste-to-energy scrap in Florida. "We also are a central processing facility for ferrous material for eight waste-to-energy facilities in the state."

Operations Manager Jim Riley for Palm Beach Resource Recovery Corporation in Palm Beach, FL, explains there are two sides to his plant, which employs 200. They include a shredding operation that runs two shifts five and a half days a week and a boiler plant operating 24/7.

"We run garbage by a magnet and then trommel it, discarding material less than 2 inches. Material between 2 and 5 inches goes through an eddy current for aluminum recovery. Material larger than 6 inches goes through our 1,000-horsepower horizontal shredder. What's still in the wastestream after that is boiler fuel."

Riley, who has been with the company six years and in the waste industry since 1987, reports that his facility handles 800,000 tpy. "We're removing nonferrous metal as well as aluminum, including coins and brass. Because we're not burning grit, residue of less-than-2-inch material goes directly to the landfill. Nonfuel items make up about 25% of the stream."

Metal accounts for 4% of the total flow and is sent to scrap dealers. Riley adds, "Aluminum is picked up here and ferrous is shredded across the street before going straight to a mill. We're catching aluminum before and after burn. We're so happy with our eddy-current technology that we plan to add a fourth one, which we'll run after combustion, even though metal at that stage has only about 60% the value of the same material caught before combustion."

Regarding troublesome elements in his mass-burn operation, Riley notes that fiberglass is chief. "We watch for it. We work with the county to get it out of the wastestream while still on the tipping floor. We also have a problem with mattresses, cables, ropes, nylon stockings, and all sorts of long, stringy material. We use temporary employees to stand by the wastestream and look for that."

Riley explains that the county owns the facility and his company is the hired operator. "So we are a for-profit operation. It took about 30 days to become comfortable with our automated system, and preventive maintenance on the 24/7 side takes less than two days a week with four workers. We utilize component-replacement strategy to provide a perpetual operation.

"Since the shredding side has just two shifts, we use the third for maintenance, which normally takes seven people. But during a line shutdown or overhaul, we'll triple that number. We repair the shredders and the trommels and rebuild the conveyors. The plant was built with three trommels back in 1989, and by January of 2001 we had replaced the third one. We bid on the trommels, making specific requests for reliability, including oversized bearings, T-1 steel for trommel screens, and very tight tolerances to keep the 70-foot trommel straight within an eighth of an inch. Heil supplied the replacement trommel for the last two, which had broken like eggs. The earlier replacement is three years old, and we've not had the first problem with it."

Riley concludes, "When you're pushing 3,000 tons per day, the stream is tough and inspectors can miss even engine blocks. Besides trommels, we've also replaced the shredder rotors. We replaced those with Riverside shredder rotors because, no matter how hard the load, the shafts don't bend."

The good thing is there's fuel enough to keep the boilers busy. "We no longer have to order any garbage to keep the plant burning. We monitor that on a daily basis. We predict what is needed to support the operation, and the excess goes straight to the landfill."

About Trommels

A number of manufacturers supply trommels to the waste industry, including Central Manufacturing in Groveland, IL. Mike McLemore, president, states that the main issue with trommels is blinding or clogging of the screens. "Trommels need to be designed to suit the application and sized to minimize the frequency of cleaning. A flat, faceted-shape barrel will tumble product better than a round one, unless ‘lifters' are incorporated into the round format. Also, the aftermarket flat-screen panels are typically less expensive and easier to replace."

McLemore continues, "The heart of the machine is the trunnions or support wheels–in most cases a four-point support with a trust roller at one end to hold the barrel in place. These components are subject to wear and possibly misalignment. Inspect and service [them] periodically. Most rotary screens are pitched downward in order to convey the product through the barrel. The steeper the slope, the faster the product conveys. The negative effect is less retention time to screen."

He adds that each project can be unique and requires the best combination of physical size, slope, speed, and so on. Variable rpm and downslope can be incorporated into the design. As with any machinery, a before-startup inspection is highly recommended. "Rotary screens are typically driven through the trunnions. Some applications and/or environments might require a more positive chain-wrap drive train and single power transmission with sprocket-chain engagement. This style guarantees against any friction loss with limited trunnion specification, overload conditions, et cetera."

The third kind of trommel involves a live axle through the barrel center. "Support wheels can be eliminated, and if [the trommel is] precision built, higher rotation speeds are easily attainable. The downside is the necessity for internal supports, which can hinder flow."

McLemore points out that a common concern is the presence of unraveled videotapes and similar items. Although this is not necessarily trommel-threatening, housekeeping is in order. "Unless the machine is built large enough and strong enough, avoid large, menacing objects, such as appliances, compactions, large aggregates, et cetera. Another concern is the potential for rod-shaped materials poking through the holes and coming in contact with the enclosures. Breakables such as wood are not as troublesome as steel rebar or pipe."

Screen-Care Counsel

John Willis, vice president of sales and marketing for CP manufacturing in National City, CA, points out that if screens are not properly maintained, wrapping can lead to excessive downtime. "Most curbside programs run between 5% and 15% residue, and with higher-residue mixes you have to be more diligent on the presort." He adds that when the rotating shafts on disc screens are square instead of round, wrapping is less of a problem. "You also want a drive capacity rated far beyond the screen's processing capacity. This enables it to handle temporary excess loading."

Lower rpm at the initial loading also reduces disc wear. Another help is access doors in the screens. "In our business, what you have to do is keep the pile down and operate efficiently. You need to be able to have that pile on the tipping floor cleaned up every day."

Willis emphasizes that the main issue with recyclable streams is to make good end products and do it properly. "Newspaper, mixed paper, and all hard goods have to be cleaned to maximize marketing value of those products. For example, if you can clean your news so you have less than half of 1% outthrows, then you can market that product anyplace in the world."

He continues, "There are two kinds of maintenance: preventive and repair. Most basic is the lubrication of moving parts, proper tensioning of belts and chain drives, and keeping a watchful eye on anything that could be prematurely wearing. You also need to keep the work area and maintenance area clean, including blowing off motors, keeping intake plumes clean, keeping normal wrapping on discs and rotating shafts clean, and in general establishing a maintenance program that incorporates all of these things on an hourly, daily, weekly, and monthly basis."

Willis also recommends keeping a stock of spare parts that are a normal part of wear and tear on a plant. "For example, if you have a sorting conveyor and something gets in and tears that belt, you can be down almost an entire day fixing one belt. If you have a replacement belt or a splice kit for that belt, you can replace or repair it much more quickly. Identify the problem early and fix it on a timely basis rather than waiting for the machine to fail."

Ray Dooley, manager for Sunset Waste Paper in Fresno, CA, agrees. His is a single-stream operation utilizing the City of Fresno's curbside sorting system of garbage, greenwaste, and recyclables, with only recyclables going to his plant. The operation handles 21 tph in a single shift and operates five days a week with a staff of 42, including drivers, loaders, balers, sorters, and four maintenance crew members.

"We have 20 different elements cleaning the material, and the whole system is from CP Manufacturing," he explains. "We're contracted to remove 92% of everything received on the tipping floor. Fiber represents 46.6% of the stream, but our issues with screening include plastic wrap and heavy items, such as brake drums and pieces of pipe. We have 10 people removing plastic, corrugated, any large items such as tires, buckets, and any residual that may be pure garbage that we don't want to see go across the screen."

Yet there are buried materials, which have brought about some limited downtime during the first 18 months of the plant's operation. "In one instance, we had a small metal rod wedged between a roller and the wall. Thanks to the maintenance crew, the downtime was just 10 minutes."

Nightly vigilance helps ensure that the plant is ready to go the next morning. "We do miss plastic, which gets wrapped in the screen. Every night after shutdown, the maintenance crew takes about 30 minutes cleaning the screen." With 20 years' experience in the industry, Dooley estimates a similar check just once a week would take several hours. "When you're good on routine cleaning, you eliminate downtime."

He says the plant's net daily downtime, other than for lunch and rest breaks, is less than 15 minutes. "One problem we deal with is heavy items that get mixed in the system, including greenwaste, which can mess up the air separation system." That material can end up in the bins of sorted glass, which contaminates the product. "Receivers don't want mixed products," Dooley emphasizes.

"We've been running for six months with no contamination factors at all. We handle everything one time, thanks to the quality of the people, the training they receive, and the system we're using."

He adds, "I also have 11 cameras above the stream, so I can check the whole system without leaving the office. They help me control production and quality issues without having to run out for frequent checks." A line supervisor walks the system to check quality issues, personnel issues, and anything else that might come up.

Dooley comments, "Without human involvement, these machines won't work. Thanks to the people we have, we've never had to shut down the plant."

What About Temporary Help?

While Sunset Waste Paper relies on help it's hired, workers at the City of Albuquerque's Intermediate Processing Facility include temporaries from a homeless shelter as well as probationers doing community service. In fact, more than half the work force of 20 is temporary help, yet throughput is excellent and downtime is minimal. Stan Morris, assistant superintendent of the disposal processing division for the city, points out that the facility handles 800-900 tons of recyclables a month. "We try to get landfill hauling down to 2% to 3%."

Frank Gonzales, one of two shift foremen, reports, "In a month we will handle about 500 tons of newspaper, 170 tons of cardboard, 100 tons of plastic, 40 tons of tin, and 4 to 5 tons of aluminum." Glass is minimal because a city collection program handles the glass.

Genaro Tafoya, the other shift foreman, relates that Albuquerque has a program with St. Martin's Hospitality Center, which operates a shelter for the homeless. St. Martin's acts as a private contractor, sending 10-11 people per day to the plant to work in the sorting line Monday through Friday.

Gonzales adds, "On Saturday and Sunday we have community service and ankle-bracelet people here. We'll have 20 to 30 per Saturday and Sunday." The plant operates 10 hours a day, including 30 minutes for lunch.

In terms of the biggest problem with the wastestream, he points out that it's plastic. "If we don't pull it out at the front of the line, it gets tangled in the machine. We have a couple of St. Martin's employees in the front pulling plastic. At the end of the day we clean the screens. It takes two [workers] just 20 minutes."

Tafoya relates, "When we first started out, we were checking screens at lunchtime and at the end of the day. Two years ago we found that once a day was enough. On weekends, we have so many people that we can put extra people on the sorting line to pull plastic."

Gonzales comments, "We don't have any downtime. We all go to lunch at the same time. The St. Martin's employees leave at 5 p.m., and that gives us 30 minutes to clean up. Daily cleaning of the total plant is part of the operation."

Tafoya says Bulk Handling Systems Inc. (BHS) is their sorting line—equipment supplier. "We have two screens to pull out newspaper, aluminum, tin, and plastic bottles. Now we have a direct feed line for newspaper, which we put in two years ago. Before then we had to hand-pull newspaper and drop it in a bin. Then when the container was full, we had to stop the line while the Bobcat operator moved the container and dumped the paper next to the baler." Thanks to automation, such line halts are history. Now newspaper is baled immediately instead.

Tafoya adds that their magnet picks up the tin. "But we have to watch for bulky stuff. We have people there taking care of that, and the only maintenance I've experienced with the magnet is a normal motor replacement after a long life."

Gonzales states that the magnet was part of the original system. "During our $1.8 million remodel program two years ago, we added a screen, a Keith Walking Floor, five more conveyor units, and a covered concrete tipping floor. Before that the floor was bounded by a chainlink fence, and blowing materials were a problem." He adds that they didn't close operations during the remodel but worked around the construction crew.

Regarding maintenance, Gonzales explains, "We follow the manufacturers' specs. Our monthly maintenance is done the first Wednesday of every month. We are a seven-days-a-week operation, and we overlap with two shifts on Wednesday. It takes five to six hours, and we shut down the line at the time. We have room on the tipping floor to accumulate 10 truckloads–our daily average–so that is no problem."

Tafoya comments, "With the new system, we've doubled our production and increased utilization. Before remodel, we we're sending four to five containers a day to the landfill. Now we send just one every other day."

Another strategy is to stockpile the residue in a corner during the week, then have the probationers reprocess the residue during their weekend service. Tafoya adds, "This reduces the landfill residue another 60%." All of which has reduced Albuquerque's wastestream to a mere trickle.

Thus, whether the operation is a family-owned, owner-operated, contracted, or municipal enterprise, successful operators find answers to the challenges they face in turning the wastestream into a revenue-generating asset.

Joseph Lynn Tilton is a frequent contributor to Forester Communications publications.