Slow and steady: the slow-speed, high-torque design of primary reduction equipment can help some recyclers process diverse material streams

DeAnne Toto

Slow-speed, high-torque shredders, also known as primary reduction equipment, are gaining popularity in the U.S., according to the manufacturers of these machines. Advocates say they offer quieter production and consume less energy than traditional grinding equipment. They can also require less maintenance and feature fewer wear parts than other size-reduction equipment. Using a primary reducer, recyclers can prepare diverse streams of material, including mixed C&D, for secondary processing in grinding or crushing equipment.

Rather than shred material in the conventional sense, primary reduction equipment breaks the material into smaller pieces using impaction. The result is a larger piece size than grinders or shear shredders typically produce.

Primary reduction technology is popular in Europe, where C&D recycling is done on a larger scale than in the U.S. and in a different manner.

“Shredders are very popular in the European market, but they have a different waste stream than the U.S. does,” Tim Griffing of Continental Biomass Industries Inc. (CBI), Newton, N.H., says. CBI makes the Grindall primary reducer and Annihilator heavy-duty shredder.

European recyclers typically sort incoming streams of material prior to processing. Therefore, their equipment does not need to be as heavy duty as that used in the U.S., Griffing says. “We shred raw C&D here.”

Transfer stations have been processing mixed C&D material for years for volume reduction purposes rather than recovery, Terri Ward of SSI Shredding Systems Inc., Wilsonville, Ore., says. “The growth and evolution of C&D recycling as a distinct industry has changed the requirements for processing equipment,” she says.

“As with any developing industry, C&D recyclers know that their businesses won’t reach their full potential by focusing only on the top line, i.e. tipping fees,” Ward says. “They also must work on optimizing their operations to ultimately improve the bottom line. This is where primary reduction equipment comes in.”


“If there is a trend or development,” Ward says, “it is probably safe to say that C&D recyclers are recognizing that one machine can’t do everything, and they are becoming more receptive to investing in a combination of primary and secondary equipment.”

A tandem set-up that includes a primary reducer and a secondary processor can offer recyclers many advantages. “It makes it much easier to handle and sort the material,” Griffing says, adding that the pre-processed material then flows through the remainder of the system more smoothly.

“We have some end users who are using the slow-speed machine in tandem with high-speed grinders,” says Dan Brandon of Morbark Inc., Winn, Mich. “They are processing first with the slow-speed machine, which removes the contamination, takes the steel out and creates a product of 8-inch to 10-inch minus.” The fairly clean wood is then processed in a horizontal or tub grinder, increasing the productivity of that grinder by as much as 30 percent, he says.

“As a manufacturer of high-speed machines, we don’t see the slow-speed shredder replacing the high-speed grinders,” Brandon says. “It is simply another tool that the recycler can put in his tool kit, so to speak, that increases his productivity, reduces his cost per ton and allows him to tackle a variety of waste streams that he may not have been able to without it,” he adds.


“Mixed C&D is characterized by tougher materials with metal contamination and abrasives,” Ward says. “Asphalt shingles, metal studs, carpet, brick, concrete with rebar, cardboard and drywall are the norm, not the exception.”

C&D recyclers are beginning to realize that slow-speed, primary reduction equipment enables them to accept expanded volumes of mixed C&D material, screen off fines, remove metals, recover valuable commodities and send cleaner material on to their grinding equipment, she says.

Brandon agrees that primary reduction equipment enables recyclers to accept more material than they may have accepted in the past. “The slow-speed, high-torque shredder allows the operator to actually go out after waste that is highly contaminated that he couldn’t tackle previously without a machine like this.”

Although primary reduction machines may not be able to produce a spec product for use in landfill cover, for example, they can help to optimize a recycler’s operation, Ward says, because they increase the capacity and variety of materials that a recycler can accept.

A primary reducer can also serve to make a C&D recycling operation more efficient. “It can make screening more effective by reducing plastic and ‘stringers’ that tend to blind screens. It can help maximize recovery rates by preparing and presenting material better for mechanical and manual sorting–small enough for good material flow; large enough to facilitate hand picking,” she says.

“Then there is the obvious benefit of volume reduction of bulky materials to minimize transportation costs from remote sites to the recycling facility, or for residual material that is ultimately disposed of,” Ward adds.


Marc Labry of Independence, Ohio-based Norton Environmental, the U.S. distributor for Komptech Farwick shredders, says many transfer stations that ship using rail cars find primary reduction equipment beneficial. “They are finding that they can get 30 percent more compaction into a railcar,” he says of the facilities using the Komptech primary reducer.

Gert Semler of Hammel NA, Chesterton, Ind., also notes the primary reducer’s role in volume reduction prior to shipping. “That is the goal we see with our machine–grind the stuff, reduce the size, reduce the volume and get more in the trucks,” he says.

Shane Donnelly of DoppstadtUS, Haslett Mich., also finds that transfer stations are interested in primary shredding equipment because they help to reduce transportation-related expenses. DoppstadtUS distributes the Mammoth and other primary reducers for Doppstadt, which is based in Germany.

Volume reduction also comes in handy at landfills, serving to conserve space and to extend the landfill’s life. Landfill operators, in some instances, may even migrate into recycling. “We see a high incidence of landfill operators looking at primary reduction equipment for volume reduction as well as recovery opportunities,” Ward says. “Maximizing landfill space can be accomplished through volume reduction, but landfill operators also realize that diversion and recovery done cost-effectively will have a greater impact on the bottom line.”

The reduction in waste volumes not only helps a landfill to save space, it also results in a couple of additional benefits. “They usually get better compaction,” Semler says. “You need fewer runs with the compactor over the shredded material. You have fewer leachate problems because it holds water better.”

Brandon also finds that primary reduction equipment presents landfill operators with a viable way to enter the recycling industry. “It is going to depend on what markets exist or what markets they can develop for the end product,” he says. “That is the bottom line in almost any recycling venture.”


The design of primary reducers makes them well suited to handle a variety of materials, from metals to wood to concrete, without harming their vital components, a claim that many traditional high-speed grinders cannot boast.

While large pieces of structural steel often prove “unshreddable” as far as primary reduction equipment is concerned, they do not represent as great of a problem because of the machines’ slow-speed operation and torque-sensing design.

“A truly non-shreddable object would be something like an 8-inch to 12-inch I-beam–although our large machine actually processed a 12-inch I-beam recently,” Ward says of SSI’s Pri-Max line. “While we don’t recommend this, such objects will not damage the machine because of its built-in hydraulic shockload protection.”

SSI’s primary reducers use an open cutting table and large diameter cutters. “Reduction is achieved by a combination of actions–piercing, tearing, breaking and shearing,” Ward says. “This allows high-capacity primary reduction of almost any material, without worrying about jamming the rotor, causing damage to the machine or performing daily or weekly maintenance to the cutters.”

“I suppose if you put a huge block of hard steel in there, it may not be able to digest that,” Brandon says of Morbark’s primary reducer, the Predator. “But, at the same time, it is not going to break anything.”

He continues, “On our shredder, the rotors will attempt to out that material three times. After the third time, it simply shuts back down, and you have to go in and remove whatever it is.”

Komptech’s primary shredder also takes three passes at the material before it automatically shuts off. “Then it is just a matter of hydraulically opening the door, letting the piece fall to the ground, closing the door and you are up and running in 10 or 15 minutes, which is a very short time to take care of a foreign object in a machine,” Labry says. “Most machines require that you dig out the hopper, find the obstruction, hook it an excavator with a chain and pull it out.”

CBI’s Grindall primary reducer also includes a door, which opens by remote control, allowing unshreddable material to fall out of the shredder easily. “No one has to climb in, no one has to get out of the cab,” Griffing says. “We understand what it means to be down trying to pull these things out. Downtime is money.”

Semler says a “huge” block of concrete may also pose a problem for a primary reducer. “They don’t belong in the machine. They need to be sorted out on the floor previous to loading the shredder,” he says.

Donnelly also says that large pieces of steel should be sorted prior to processing to prevent breakage to the teeth.

With their ease of maintenance and relatively low cost of ownership, primary reduction shredders may be a natural choice for C&D recyclers who want to increase the volume of material they can accept. When coupled with secondary processing equipment and screening lines, primary reducers enable recyclers to produce an array of end products. Of course, a little entrepreneurial spirit and strong local markets also help.


Compared to grinders, primary reducers generally have very few wear parts that need to be replaced on a regular basis.

“Clearly, there is less wear than there is with a high-speed machine,” Dan Brandon of Morbark Inc., says. “With a high-speed grinder, wear parts are one of your big operating costs. With these shredders, because they move so slowly, there is not as much friction and wear.”

In fact, most primary reducers feature teeth that can be hard-faced indefinitely, reducing replacement costs.

The Terminator, Komptech’s primary reducer, features triple-sided teeth. “The same tooth can be used on a new cutting edge three different times,” Marc Labry of Komptech distributor Norton Environmental, Independence, Ohio, says. “Basically, they turn the tooth after 10 days or two weeks.”

Most of Komptech’s customers put a hard-face weld on their teeth once a month to keep them built up, Labry adds. Morbark’s customers follow a similar maintenance schedule in regard to hard facing their primary reducers’ teeth, Brandon says.

Some manufacturers have taken additional steps to reduce the wear their equipment encounters. The open-table design of primary reducers from SSI Shredding Systems Inc., Wilsonville, Ore., for instance, allows dirt, rock and abrasive fines to fall through without unnecessary processing, reducing wear on the machine, the company’s Terri Ward says. “Without an open cutting table, screening fines before processing becomes more important.” She also notes the importance of routine maintenance, though she says it’s very minimal. “There’s no daily or weekly tightening, rotating or replacement of blades.”

A little common sense and preventative maintenance can go a long way with primary reduction equipment. Gert Semler of Hammel NA, Chesterton, Ind., recommends cleaning the machine daily. “Catch anything that is starting to wrap and get it off in the morning or on the same day, and you will have a lot fewer problems in the long run,” he says.

Shane Donnelly of DoppstadtUS, Haslett, Mich., suggests that care should be taken when loading primary shredding equipment. “One area that is not often talked about is the importance of feeding material across the full length of the shaft,” he says. This helps to reduce wear on the teeth at the center of the primary reducer.


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The author is associate editor of Construction & Demolition Recycling magazine and can be contacted via e-mail at

COPYRIGHT 2004 G.I.E. Media, Inc.

COPYRIGHT 2004 Gale Group

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