DEBAG SYSTEMS

GETTING IT OUT OF THE BAG

An overview of developments taking place in mechanical removal of recyclables and compostaMZs.

Pegi Ballister-Howells

shredder/bag ripper.

50 BIOCYCLE

S INCREASING portions of the waste stream shift from landfills into composting and recycling projects, continued use of plastic bags and even pa- per bags poses a challenge. Whatever is in the bags must

be removed if further processing is needed. As part of a nationwide effort to compile

information on the array of debagging sys- tems and equipment being developed and used, sites were visited during a period from June to November, 1991 in Toronto; Islip and Fresh Kills, New York; Portland, Oregon; Cleveland, Ohio; Rosemont, Pine Bend and St. Cloud, Minnesota. The primary focus was on applications for debagging yard waste since there are significantly more yard waste composting facilities than any others. Since many debagging systems are adaptable to a variety of materials, all systems located have been included in this report.

It is difficult to design an ideal collection and processing system. The design would be a function of economics, population, ease of processing and willingness of the public to participate. Market specifications for the material being collected and processed would also affecbthe collection process. The entire loop - collection, processing and markets - is constantly evolving.

From a more practical perspective, few communities are prepared to develop an ideal system. Limited budgets create the need to work within the constraints of exist- ing equipment and personnel. Rarely, if ever, are there sufficient funds to develop a waste management system from scratch. If debag- ging, and ultimately, recycling or reuse of the film plastic, can keep up with the advances in other collection and processing methods, plastic bags for use in the collection of com- postables and recyclables may remain the method of choice indefinitely.

The evaluation of mechanical debagging has shown that the contents of plastic bags can be removed more efficiently than by hand. While there is no panacea, enough op- tions are available that most problems can be solved if the variables are weighed and the most appropriate technology is chosen.

Care should be given when attempting to

make direct comparisons between ma- chines. Available data is limited since most debaggers are recent introductions for which there is little field experience. Ma- chines evaluated out of the context of an en- tire system may be misleading. Systems evaluated for cost in one part of the country would give different results elsewhere based on variability in wastes, debt, other equip- ment, and costs related to labor, land, and landfilling.

It is recommended that the needs of a par- ticular composting or other waste manage- ment facility be evaluated and the informa- tion given here be used to determine which available equipment will best meet the spe- cific needs of that operation. For the purpose of this report, the debaggers will be broken down into three categories: Slitter/trommel approach; use of augers; all other designs.

SLITTER/TROMMELS Whirl-Air-Flow, located in Minneapolis,

Minnesota designed a freestanding slitterl trommel system to be used on incoming MSW at the Recomp composting facility in St. Cloud, Minnesota. The incoming materi- al is loaded onto a conveyor by a front end loader. Before dropping into the slitter, pre- sort of oversized material is required. The sli t ter consists of two rotating shafts equipped with cutting blades that turn in opposite directions forcing the material be- tween the shafts. Approximately 95 percent of the bags are opened as they pass through the cutting blades. The slitter drops the ma- terial down where it passes into the trom- mel. Roughly 75 percent of the material is removed from the bags as they pass through the trommel. Bags remain whole but are contaminated with the residue.

According to Whirl-Air-Flow engineers, if the system was used exclusively for bagged yard waste, 95 percent of the bags would be opened with 95 percent of the contents re- moved. The bags would be whole, but signif- icantly cleaner than when processing MSW.

The company's engineers rate the slitter at 15 to 20 tons per hour using two 10 HP motors. The trommel screen also has a rat- ed capacity of 15 to 20 tons per hour and uses a 15 HP motor. For yard waste alone,

MARCH 1992

A SUPERMARKET firm in a sub- urban Philadelphia community was able to capture and redirect 70 percent of its waste stream in a two month pilot project that produced 24 tons of compost. As part of ap effort to lower dispos-

al costs and gain high marks from environ- mentally, minded conkumers, Clemens su- permarldet in Springfiouse, Pennsylvania, and the: Browning-Ferris Industries (BFI) office in:Montgomeryville, agreed to initiate the composting experiment in the spring of 1991. The waste manageinent firm has the hauling contract for the CleM’ens chain.

BFI d$veloped training materials for em- ployees and analyzed the store’s waste stream. Special 32-gallon storage containers were supplied, and a 30-yard rolloff com- pactor was modified for storage and trans- portation. Composting was done a t a facili- ty 10 miles away. “This approach is probably going to be the trend with supermarkets na- tionwide,” says Herb Northrop, special pro- jects manager for BFI, who oversaw the pi- lot.

Northrop believes there are four links in the chain of a successful supermarket com- posting effort - the generator, collector, processor and market. “If any of the links are weak, it will disrupt the whole chain,” he says.

The first link, the generator, was easy. “When I saw IJTE opportunity, the first partner I approached was Clemens, be- cause of our relationship with them and also their integrity and concern for the en- vironment displayed in the past,” says Northrop. As for Clemens, company offi- cials had been thinking along the same lines. Paul W. Rorer heads a Clemens Mar- kets committee called CARES, or Con- cerned About Responsible Environmental Solutions. Rorer looked at the supermarket business, and realized the huge potential for composting. Clemens foresees initiating composting programs at its 12 stores in southeastern Pennsylvania.

BFI was given verbal approval from DER for the pilot project, but the agency told the hauler to stop after two months until an of- ficial permit was signed. The hauler is con- sidering sending the store’s waste to a site owned by Americap Soil Inc. in Freehold, N.J. Northrop anticipates that all of the Clemens stores, VJill be composting food waste this spring.

A key task at the beginning of the pilot was to teach Clemens’ employees which wastes were compostable. Organic residuals include fruits, paper, juices, waxed card- board, salad waste, wood and other materi- als. Northrop spent a lot of time at the store with employees answering questions: “I was asked, for example, should they separate a pie from its plastic containers (the cost ef- fectiveness must be weighed), or if a paper cake container with a plastic window should be excluded from the compost (it should).”

The 32-gallon containers for organic

INDUSTRY PILOT

DIVERT THE FLOW ”\,,

waste were colored blue to stand ou t from other trash receptacles. They were pl ced in locations where high amounts o 9 I com- postable materials are generated (e.g., the food preparation room) and plastered with decals offering clear directions of what can be composted. “We used the same experi- ence that we had implementing commercial recycling programs, and applied it to’ com- mercial composting,” says Northrop.

COLLECTION AND TRANSPORT The next step, collecting and transporting

waste, was taken care of by using the self- contained rolloff comp.actor, a piece of equip- ment widely used alrkady by supermarkets and restaurants. The machine, which costs between $8,000 and $10,000, had to be mod- ified to deal with the increased liquid con- tent of purely organic waste. By using spe- cial gaskets, BFI was able to triple the container’s water holding capacity from 500 to 1,500 gallons. According to Rorer, odor problems decreased when the supermarket began composting, since the market had previously placed everything in a dumpster, which was prone to leak more and was less airtight.

The amount of contaminants in the waste when it reached the composting facility was negligible. Northrop attributes this result to tlfe training program, and the cooperation of Clemens employees.

Two composting methods were used. One involved grinding materials to reduce the size of such items as large cardboard boxes and produce crates; the other involved no grinding. All residuals were mixed with yard trimmings in order to balance the car- bodnitrogen ratio for optimum decomposi- tion. The mixed material was placed in out- door windrows which were mechanically turned.

The project proved to BFI the viability of every step in the chain of commercial com- posting. Diversion to composting reduced disposal costs by 15 percent. Tipping fees at a waste incinerator in Montgomery County, where the store is located, are nearly $70 per ton. “Even factoring in all of the costs of new equipment and providing a new ser- vice, the customer should be able to realize a reduction in disposal costs,” Northrop con- cludes.

A 12 store chain in southeastern Pennsylvania works with its hauler to train s t a f , collect and transport organic residuals during a two monfhtrial.

Robert Steuteville

’\ . I’

BIOCYCLE MARCH 1992 49

Whirl-Air-Flow estimates that the blades should last for 3.5 years. With sharpening, two sets of cutting blades will last for 10 years.

The cost of the Whirl-Air-Flow slitter is $58,000; the trommel is $22,500. The con- veyors necessary for feeding the slitter are approximately $300 to $350 per foot.

SSI Shredding Systems, located in Wilsonville, Oregon designed the SSI 5000E Shreddermag Ripper for the Metro Central MRF in Portland, Oregon for the processing of MSW. This is a large, freestanding, non- mobile unit. Loads are dropped onto the floor of a receiving area where oversized ma- terial is removed. Most commonly recycled items already have been removed through a curbside recycling program. Therefore the material processed is primarily paper and other compostables such as yard waste and scrap wood.

The Portland MRF is set up with a hopper below floor level. This can be loaded from the tipping floor using a Bobcat, or trucks can dump directly into the hopper if the incom- ing material is free of oversized objects. A conveyor then feeds the shredder.

The shredder cuts the bags into many pieces, which vary significantly in size. The waste then passes through a magnet for the removal of ferrous and then to an air classi- fier which sends the plastic off with the light fraction. The main component of the light fraction is d i r t y m e r t h a t is marketed as a fuel. The plastic is currently considered a contaminant of the paper and is being eval- uated to determine if it can be burned with the paper.

When processing MSW, the SSI Shred- der/Bag Ripper operates a t a rate of up to 40 tons per hour. Yard waste alone can be pro- cessed a t a rate of up to 90 tons per hour.

The 5000E unit, which includes the hop- per, shredder, support stands, motor control panel and operator panel costs $240,000. Po- tential maintenance costs include replace- ment or renovation of the cutter blades; fre- quency of maintenance depends on the material being shredded. For wood demoli- tion, the blades should last 6,000 hours. For tires, replacement can be expected after 1,000 hours.

For debagging MSW, yard waste, or other compostables, the cutting blades can be spaced to cut the bags only once or twice, leaving them whole or in a small number of pieces. This modification would make re- trieval of the bags easier for recycling pur- poses or to reduce contamination levels.

Scarab Manufacturing and Leasing, Inc. has recently introduced “The Scarab Bag Separation System.” The prototype was ob- served at the factory in White Deer, Texas. This, too, is a conveyor fed slitter/trommel system but designed specifically for yard waste. The slitter is a rotating drum with the teeth on the outside of the drum. It is fed by a conveyor that can be loaded with a grapple or front end loader. The teeth slice the bags open, releasing material as the bags are agitated against the drum. Empty

bags and their contents pass under the drum and are conveyed to the trommel.

A second conveyor takes the contents and the bags from the slitter to a trommel punched with four and five inch holes. Each bag sustains approximately 28 revolutions before dropping out the end into a contain- er. A third conveyor under the trommel, called the discharge conveyor, carries the contents of the bags for deposit into a truck or to form a pile on the ground.

The bags are removed whole and 99 per- cent empty. For additional cleaning, the con- tainer of bags can be run through the system a second time at the end of the day.

The demonstration indicated the system is capable of processing 1,700 bags an hour. The bags contained primarily leaves and were estimated to weigh 30 pounds each. Those figures convert to 25 tons per hour. The system appears more efficient when be- ing loaded to capacity since the weight of the bags pushing on themselves as they are con- veyed into the slitter helps open the bags and releases the contents.

At this time, Scarab recommends that brush be collected separately from leaves and grass clippings. Brush would leave the trommel with the plastic. An additional pro- cessing step is in the works to separate the brush.

The prototype model was designed for use a t large scale facilities and will cost approx- imately $240,000. The company expects to design and build smaller models based on the needs of specific facilities. The addition- al cost for brush separation is anticipated to be roughly $30,000.

The Islip Process is a system that was con- ceived by Dr. Stuart Buckner in the town of Islip, New York. Buckner has put together, with some modification, component parts of different manufacturers to achieve the goals of his original concept. They are currently using an Iggesund shredder, Power Screen covered conveyors, and Triple S trommel screens sized to pass through leaves, grass and shredded brush. The system can process approximately 25 to 30 tons per hour.

The trommel removes approximately 70 percent of the shredded plastic or paper bags. The rest is removed at the time of fi- nal screening. The plastic, at the time of re- moval, is in small pieces that are moderate- ly clean.

The facility processes approximately 60,000 tons per year of yard waste. Islip is a densely populated community on Long Is- land. The proximity of residents requires ef- ficient management. Material arrives in both paper and plastic bags as well as in bulk. Rapid handling is necessary to accom- modate space limitations and to prevent odor formation. Front end shredding or grinding is also useful for volume reduction.

The total cost of the front end system in Is- lip is approximately $650,000. The compo- nents break down to $400,000 for the shred- der, $50,000 for the covered conveyors, and $200,000 for the first trommel. The final screening, which removes the residual plas-

lnfeed conveyor and drum on Scarab bag separation system.

lggesund shredder used in the Islip Process.

Equipment in use at Fresh Kills landfill.

BIOCYCLE MARCH 1992 51

markediiig the Lumnlus DeBagger in re- sponse to the need for handling recyclables collected in plastic bags.

The bagged commingled recyclables can be loaded into the hopper using a loader or grapple. A spiked drag chain then moves the bags through a trough feeding the opening mechanism. Two horizontal wheels are edged in vertical spikes. The wheels rotate in opposite directions. The bags in the trough drop down onto the rotating wheels. Pressure is applied to the bags to encourage the plastic to be hooked by the vertical spikes. As the wheels rotate away from each other, the bags are pulled apart and the con- tents spill out onto a conveyor. The bag, which is in one or two large pieces, clings to the spikes until it is vacuumed off as the wheels continue t o rotate. The current mod- el was introduced in April, 1991 and is com- pletely enclosed.

The observed rate of debagging was ap- proximately 2,000 bags per hour or in the range of 10 tonsihour (using a conversion rate of 10 lbshag). Virtually all bags are re- trieved mechanically. The plastic is clean and ready for baling. According to Lummus, the glass breakage is kept low due to the cushioning provided by the commingling of the recyclables as well as the use of bags.

Based on an evaluation done by MacLaren Engineers, 86.5 percent of the processed glass was totally intact. Only 2.7 percent was not recoveraddcdue to excess breakage. A Lummus DeBagger has been installed at a facility in Danbury, Connecticut for the de- bagging of commingled recyclables. Compa- ny representatives believe the machine is readily adaptable to the debagging of organ- ic waste for composting. The approximate cost of a Lummus DeBagger is $95,000. It is expected that some custom configurations will be necessary.

SCAT manufactures a compost windrow turner which is used for debagging as well. Its elevating face lifts the material on a pad- dle-like system face equipped with trencher teeth that hook the plastic bags. As the bags go over the top of the face, they are flipped and dumped. The bags hang on the teeth or are draped over the back panel if they should drop from the teeth as they flip over the top.

The addition of a bar equipped with cut- ting blades increased the efficiency of bag opening, while a modification of the cupped trencher teeth to spiked “snag” teeth in- creased the rate of bag retrieval. The SCAT 482B is more commonly used for debagging than the larger models. It is a self-powered, tow-type machine that attaches with a sin- gle pin hook-up. The SCAT 482B can be pulled with a front-end loader or some trac- tor models.

SCAT recommends that for optimum effi- ciency, the bagged material should be piled no more than three bags deep in a windrow. The width depends on whether the operator intends to debag in a single or double pass.

The SCAT observed was at the Pine Bend Landfill, Minnesota. The elevating face was

equipped with 115 snag teeth and 127 stan- dard trencher teeth. The 75 foot windrow contained approximately 1,250 bags con- taining mixed yard waste that was primari- ly grass. It took one hour and four minutes and three double passes to remove 90 per- cent of the bags. In the third pass, partially decomposed leaves were added to the pile for composting purposes. The material was blended in while the final batch of plastic was removed.

Four laborers and one machine operator were employed. At the end of each half pass, plastic was removed from the face, taking an average of nine minutes each time. At this rate, 1,172 bags were opened per hour. Us- ing a conversion factor of 70 pounds per bag, this equals 41 tons per hour. The cost of the SCAT 482B is $57,000.

The Debagit bag opener is a compactor truck mounted unit for use in curbside de- bagging of yard waste marketed by Superi- o r Tech, Inc. of Lancaster, Pennsylvania. The machine is appropriate for the smaller community - 10,000 to 25,000 population -where the same haulers who collect MSW also collect yard waste.

The unit fits any rear load compactor truck. The operator puts a bag of yard waste into Debagit, and holds on to it. The teeth on the conveyor open the bottom of the bag. The contents spills out and the conveyor moves the material into the truck. The empty bag is then stored in another bag attached to the side of the unit.

The increase in collection time is compen- sated by reduced labor and material han- dling at the composting site, and no addi- tional debagging or trommeling to remove plastic. Additional advantages include a plastic free compost product, minimum re- tention time in the bags prior to arrival at the facility, and the opportunity to remove trash before it gets into the truck.

It is difficult to evaluate the rate of de- bagging since the rate is dependent on the travel time between stops and the number of bags put out at each house. As an example, at the peak of leaf collection in November, a three worker crew consisting of a driver and two operators picked up 612 bags between 6:30 and 9:30 am in Lancaster. The cost of a Debagit unit is $8,750.

Riedel Waste Systems, Inc. installed high pressure water jets at its MSW composting facility in Portland, Oregon. The pressur- ized water sliced open the bags without damage to the contents. Other advantages included reduced dust, the addition of water which was beneficial to the composting pro- cess, and the bags remained whole for easy removal in the picking process. This system is not currently in use due to operational dif- ficulties.

Wildcat Manufacturing Company, Inc. has produced compost windrow turners for many years. The turner always has removed plastic from the piles, but it has been diffi- cult t o remove the plastic from the drum once it wraps around.

The first improvement was made in 1990

SCAT turner used for debagging.

Truck mounted Debagit bag opener.

Widcat turner used for debagging.

Dover Conveyor bag opener.

MARCH 1992 53 BIOCYCLE

Lande LD- 1 debagger.

t

when the bearings were modified to sepa- rate them from the material in the windrow. This protects the bearings from plastic and reduces wear. Most recently, Wildcat de- signed a system that simplifies removal of plastic and other contaminants from the drum. The unit is mounted on a radial arm that swings into position to cut off the bags or other material that may have wrapped onto the drum. A gas engine powers the cut off wheel.

Four passes with the Wildcat turner will remove 80 percent of the plastic, with the machine needing to be cleaned off approxi- mately every 75 feet. (This will vary de- pending on the size of the windrow and the amount of plastic.) According to the manu- facturer, one person can clean off the drum in less than five minutes.

While this system is most easily incorpo- rated onto a recently purchased model with the necessary modified drum, any model of the Wildcat AME series can be retrofitted. The cost has yet to be determined since the system is still in an introductory phase. It is expected t o fall within the $10,000 to $15,000 range.

The “Bag Opener” is a debagging system developed by Dover Conveyor and Equip- ment located in Midvale, Ohio. The target- ed material is bagged recyclables, but the manufacturer is testing other waste stream as well.

The Bag Opener can be fed with a Bobcat or an in-line conveyor. The machine oper-

announc ing the

1992 BIOCYCLE

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BioCycle 419 State Ave. Emmaus, PA 18049 0 (215) 967-4135

ates through the opening and closing of 11p- per and lower jaws. As the upper jaws’re- tract, bags fall into the processing chamber. Then the upper jaws close. No additional bags are fed into the processing area at this time. The bags are held in a fixed position as the rippers split the bags. The lower jaws open and the recyclables and the bags drop onto the conveyor below. The process id then repeated. Pressure sensors limit glass breakage.

A mechanical method of removing the plastic is under development. The bags re- moved are whole; 90 percent are processed. Those processed are 99 percent empty, ac‘- cording to Dover. Fine tuning of the system is still underway, but at this time bags are opened at a rate of 1,200 to 1,500 bags per hour. The “Bag Opener” should be available in June, 1992 at an anticipated cost of $49,500.

The Lande LD-1 is designed by Lande En- vironmental Equipment, Inc. in Whitmore Lake, Michigan. The debagger targets yard waste but the prototype is currently being tested on other bagged waste materials. The unit can be used as a stationary debagger or can be pulled by a tractor. Power is supplied by a PTO but the system can be adapted to an electric motor.

The system is manually loaded at the con- veyor infeed, which starts at ground level and is raised at a 45” angle. The conveyor is fitted with metal bars every 18 inches. These bars are perpendicular to the length of the conveyor. Each bar has two tines which hook the bags.

A saw-toothed blade is suspended above the conveyor midway from the top. The hooked bags must pass under the blade, which floats up and down to adjust for dif- ferent size bags. At the top, the contents of the bags drop into a bin where a blower, sev- en feet off the ground, blows the material out of the bags. The contents can go into an appropriate container such as a hopper or a truck. If the system is mobile, it can be blown directly into a windrow.

The bags remain attached to the tines as the belt moves to the underside of the con- veyor. They dangle down and are caught by a double roller, similar t o the rollers on an old fashioned wringer washing machine. The bags are pulled off and fed, via a short conveyor, into a hay baler where they are automatically baled. Designers claim the Lande LD-1 opens one bag every three sec- onds or 1,200 bags per hour. The cost is $88,000.

Pegi Ballister-Howells is a consultant based in East Windsor, New Jersey who focuses on com- posting issues. Her information gathering ef- fort on debagging machines and systems was funded by Mobil Chemical. For questions or comments on related deuelopments, the author may be contacted at (609) 426-1690. A list with addresses and phone numbers of companies mentioned in this report will appear in next month’s Directory of Composting Equipment and Systems.

54 BIOCYCLE MARCH 1992