Transforming Waste to Resource

Oct. 1, 2009

As more and more grading and excavation contractors are discovering, the old way of dealing with trashed trees and stumps, chunks of concrete, or land-clearing wastes by hauling the stuff away generates even more waste in the form of wasted time, money, and land for dumping it. That’s where grinding, mulching or crushing equipment can put more green in your pocket. It enables you to process woody material into moneymaking fuel for boilers or mulch for landscaping and erosion control uses. Also, you can convert rocks, brick, concrete, or asphalt rubble into construction-grade aggregate.

These advantages, along with environmentally driven rules and regulations to protect air quality by prohibiting burning of woody debris and to conserve landfill space, have led to an increasing demand for this equipment “Up until the downturn in the economy and the drop in construction activity, the trend in sales of grinders over the last five to 10 years has been nothing but up, and grinding is sure to be a key part of the constantly evolving industry going forward.” says Brian Bergman, operations manager for CW Mill, which manufactures the Hogzilla line of grinders.

When it comes to implementing a green recycling program for material cleared from the land, you have several options. For example, you can transport the debris offsite to a large stationary grinder or crusher, which usually runs on electricity. In fact, some operators who produce hog fuel from these grinders use the end product to help make their own electricity to power the machines. While this approach eliminates dumping fees to dispose of the cleared material, it still entails the costs of transporting unground or possibly rough-ground material to the facility, but this method provides a more controlled and structured work site which can be very beneficial when coupled to the potential fuel savings and reduced maintenance costs associated with electric units. Of course, you can load one of these electrically powered stationary units onto a trailer and haul it from one job site to another if there is an available power source, avoiding some material hauling costs.

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Photo: Bandit Industries
Horizontal grinders from Bandit Industries feature cuttermills that cut the woodwaste apart.

However, an easier alternative for some of those who need to move from job site to job site is a diesel-powered portable unit mounted on a trailer frame. “Moving it is a matter of backing your semi tractor underneath and away you go,” Bergman says. “You can park the machine wherever your semi can travel and then bring the debris to the grinder. Over the years, this has been the most popular way to configure grinders.”

More Mobility
However, within the past five to 10 years, another type of portable grinding or crushing machine, which offers the ultimate in onsite maneuverability, has been winning fans among contractors: remote-controlled, track-equipped units that travel around the job site to where the debris has been stockpiled.

“Before, if you wanted to move a trailer-mounted machine around the job site, you put a dolly wheel assembly under it and dragged it where you wanted with a dozer,” Bergman says. “The popularity of track machines has grown tremendously, because they can travel over rough terrain without the need for bridges or established roads. You can operate them with the remote control as you walk alongside. However, more typically, they are controlled by the operator of the excavator or front-end loader used to feed debris into the machines.”

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Rubble Master introduced its first mobile compact crusher for onsite processing of rock, brick, concrete and asphalt to the European market in 1992, entering the North American market seven years later, today offering a full range of compact equipment.

“We consider ourselves as inventing the first truly mobile crusher, compact enough to haul on a truck in one piece and designed to be set up quickly once onsite,” says Javier Davila, the company’s business development manager. “Mobile crushers have revolutionized the business model for site development and demolition contractors. It’s the most ecologically friendly and most profitable way to recycle demolition debris onsite. This concept has really taken off in the United States in the last four or five years.”

Examples of the type, size, and production rates of impact crushers in the market include those made by Rubble Master. The company’s most compact unit, the 13-ton model RM60, has an hourly material throughput of 60 to 80 tons, depending on the material. It can be transported using a truck with drag-on hook system and hauled on a trailer to be ready for operation in just 10 minutes, notes Davila. The 30-ton RM100 track machine, the largest model, can process as much as 220 tons of material per hour. It is transported on a three-axle lowboy trailer. The company’s most popular model is the RM80, a 25-ton crawler unit with an hourly production capacity of up to about 170 tons per hour. Each features a magnet that removes rebar and other metal from the crushed material.

Whether a stationary, portable, or self-propelled unit, grinders and crushers represent a sizeable investment. Also, by the very nature of their operation, they require a high level of maintenance. Depending on the size and scope of your operations, renting the equipment or hiring a grinding or crushing contractor may be more cost-effective than purchasing it and doing it yourself. However, in addition to the convenience of using the machine on your schedule, owning the equipment can generate additional revenues through your own custom grinding or crushing services. More information is available at

Tub and Horizontal Grinders
Manufacturers offer two basic types of grinders for processing woodwaste. Depending on size, they can handle whole trees as well as logs, stumps, and brush to produce fuel or mulch. A tub grinder features a rotating tub with an open top. Woodwaste placed inside the tub is fed, usually by gravity, into a mill. There, a series of steel hammers attached to shaft, which rotates at high speeds, pounds the wood into much smaller pieces. The processed material is forced through metal screens. Properly size wood pieces pass through and are discharged, while coarser materials remain in the hammermill for further reduction. The size of the screen, the number and placement of hammers, and shaft speed can be adjusted to achieve the desired end product.

A horizontal grinder uses either hammers or cutting tools on a rotating shaft to reduce woodwaste to the desired size. However, as the name implies, woodwaste is placed on a horizontal conveyor that feeds the material through a rectangular opening into the hammer or cutting mill.

Photo: Fecon
Fecon’s FRM70 brush cutter can convert woodwaste for use in erosion control onsite.

“A tub grinder can definitely handle larger, more difficult material and is the most versatile,” says Bergman. “However, because of the way it operates, it can eject wood out through the top of the tub. So, it’s more suitable in areas where you can better control access or good thrown-object restraint systems are available. A horizontal grinder retains the wood inside a somewhat closed chamber during processing. However, the open end of the feed chute presents its own unique ejection hazards that also require a controlled work area. It’s better suited for handling long material and smaller-diameter tree trunks and logs.”

As examples of the size and production capacity of grinders available today, the Beast Recylcer line of horizontal grinders, made by Bandit Industries Inc., includes four towable and two track models. Instead of the hammermill typically found in grinders, they feature a cuttermill that cuts the woodwaste apart. The smallest towable model, the 1680, is designed for small land-clearing operations. It has a 24-by-52-inch mill opening and can be equipped with engine options ranging from 160 to 275 horsepower. The largest towable, the Model 4680, will process large-diameter stumps and whole trees at production rates around 800 cubic yards or more per hour, the company reports. With a mill opening of 45-by-60 inches, it can be equipped with 875- to 1,050-horsepower engines. The self-propelled, radio-remote-controlled models include the 3680 Track (630 or 700 horsepower) and 4680 Track machine (875 or 1,200 horsepower), which will process whole trees in less than a minute

More information is available at

CW Mill’s Hogzilla tub grinder models are available as self-loading or self-propelled units with tub diameters of 13 to 15 feet. Depending on size and model, they range from 525 to 1,650-horsepower diesel-powered units and weigh 48,000 to 110,000 pounds. In many applications they can produce from 120 to 200 tons of processed material per hour, Bergman notes. The company’s horizontal grinders are available in 400 to 1,000-horsepower models, weighing from 95,000 to 116,000 pounds. They can be configured as stationary units, as portable models with pintle or fifth-wheel hitches or as track-equipped grinders. Some units are equipped with grapple loaders.

More information is available at

“Most of our customers buy as much horsepower as they can afford,” he says. “Then, since size affects ease of transport, the ability to transport the machine becomes the limiting factor for those who need to move their machinery. The 1,000-horsepower track or trailer-mounted machines are our most popular models, because they are large enough to provide high production and can be transported reasonably on the road with a permit.”

In considering your choices, Bergman suggests paying special attention to the machine’s frame and mill. “Diesel engines can be rebuilt and so should the rest of the possible wear parts on a grinder,” he explains. This presents an opportunity for a machine like this to have a very long life while keeping costs down. The long-term strength of the machine lies in the frame and mill. A well-made grinder should have the potential to out-live more than one well-cared-for engine. Look for a solid frame built with very thick-walled steel rectangular tubing and for a hammer mill made of thick, heavy plates and massive hammers and hammer rods. Good-quality components should be visible throughout the whole machine, and this will provide the longest service life in the toughest applications.

Mulching Tools
In addition to grinders, manufacturers offer a variety of wood-processing attachments for machines, such as skid-steer and compact track loaders, excavators, and track carriers. They convert trees, stumps and brush to mulch for use onsite to control erosion or to simply biodegrade, eliminating costs of hauling away the woodwaste.

For example, the line of brush-cutting attachments and track carriers made by Fecon Inc., includes the new FRM70 Heavy Duty Rotary Brush Hog Brush Cutter. It is designed for skid-steer loaders with hydraulic flows of 21 to 45 gallons per minute. A bidirectional direct-drive gear motor and four 12-inch dual-sided rotary axe blades cut brush up to 6 inches in diameter.

More information is available at

FAE USA Inc. makes various forestry mulching heads designed to fit a wide range of prime movers from 125 horsepower to 600 horsepower in either rubber-tire or tracked machines. Its 200U model, for instance, offers working widths of 50 to 86 inches, depending on version, and can be used with hydraulic or PTO-driven prime movers equipped with 140 to 250 horsepower engines. FAE also makes two prime movers. The PT-400 with its 385-horsepower diesel engine and motorized traction is suitable for use on all types of terrain and climate, as well as a wide range of different applications, including land clearing and construction. The 180-horsepower PT-200 features a Berco oscillating track undercarriage that adapts to uneven terrain.

More information is available at

ProGrind Systems manufactures chippers mounted on excavators for chipping trees, brush, and stumps. The Progrind Series 50 grinder has a 50-by-26-inch smooth drumhead with fixed carbide patented teeth, patented drive-belt system, and hydraulic motor drive. A 440-horsepower Caterpillar power pack produces a hydraulic flow of 155 gallons per minute and a pressure of 5,000 psi to operate the chipper. The unit can reach over ditch lines, streams, culverts, fence lines, and other obstructions to trim limbs, chip trees, and grind brush and stumps into mulch. Applications include site development projects and clearing utility line rights of way for water and sewer construction.

More information is available at

Mobile Crushers
Machines for crushing rocks, bricks, or chunks of concrete or asphalt are also available in two types. A jaw crusher squeezes the material between two jaws. Usually one of the jaws is fixed, while the other oscillates. By contrast, an impact crusher, like a grinder, uses hammers mounted on a spinning rotor to break up the material. Screens are used to produce the desired end-product size.

Examples of the type, size, and production rates of impact crushers in the market include those made by Rubble Master. The company’s most compact unit, the 13-ton model RM 60, has an hourly material throughput of 60 to 80 tons, depending on the material. It can be transported using a truck with drag-on hook system and hauled on a trailer and be ready for operation in just 10 minutes, notes Davila.

The 30-ton RM100 track machine, the largest model, can process as much as 220 tons of material per hour. It is transported on a three-axle lowboy trailer. The company’s most popular model is the RM80, a 25-ton crawler unit with an hourly production capacity of up to about 168 tons per hour. Each features a magnet that removes rebar and other metal from the crushed material.

More information is available at

The type and size of the machine, however, aren’t the only factors to consider when buying a crusher, Davila notes. When comparing products he suggests also factoring in the cost of producing the end product, which includes expenses for hauling the machine to and from the job site, setting it up and keeping it maintained.

“Ideally, the crusher should not only produce the size and shape of end product you want for use as a construction aggregate but also do so in a single pass,” he says. “Crushers that can be serviced easily from the ground save time and improve safety compared with having to get on the machine to access service points. And, because mobile crushers are often used in urban applications near public buildings, features that minimize noise, dust and engine emissions during operation are important. Don’t forget fuel economy, either. Fuel efficiency among different makes and models can vary widely.”

Screening Tools
A variety of equipment, including attachments, is also available for screening recycled rock, concrete, asphalt, and other demolition debris to produce the desired size of end product. REMU makes the Combi Station, a compact, nonclogging screening plant that can separate difficult-to-handle materials, including demolition waste and moist, sticky materials. It can be equipped with various sizes of conveyors and screening components to process up to 400 cubic yards of materials per hour. The 22,000-pound unit’s nonclogging screening element features steel blades and adjusts hydraulically from a 5 to a 20-degree angle to achieve the desired capacity and quality. The skid-mounted unit comes with available wheels for temporary use onsite. The crawler-track version has an optional wireless remote control.

The company also makes screening buckets for machines ranging in size from compact excavators and skid-steer loaders to large excavators and wheel loaders. With capacities of .15 to 8.4 cubic yards, depending on model, this attachment screens without crushing, the company reports. It uses rotating disk/blades and cleaning scrapers to handle moist and sticky materials, including those with a high clay content.

More information is available at

Here’s how two contractors have taken different approaches to profiting from recycling materials cleared from construction sites.

Making Money by Making Compost
Excavating contractor John Keene has added a retail enterprise to his business by using a grinder to process tree stumps into material for compost.

His company, John Keene Excavation Inc. of West Tisbury, MA, provides a variety of excavating and site-development work for customers on the island of Martha’s Vineyard.

The grinding enterprise enables him to make money from the site of a former sand pit. At one time, he charged contractors and landowners to dump tree stumps, logs, and brush there, which he buried. However, about 10 years ago, environmental regulations forced him to dig up the woodwaste. That’s when he began his composting operation.

Keene started with a tub grinder. However, because of concerns about noise levels with debris ejected from the machines, due to the design of this type of grinder, he switched to quieter-running horizontal grinders, which confine the material inside the machine as it is processed. That was after he compared operation and production of the two types of grinders side by side at his site. “Each was better in some ways than the other,” he says.

The price tag of the horizontal grinder was less. Also, it was easier to move around the work site. “The tub grinder required a tractor and a fifth wheel to move, and that was difficult to do in tight spaces,” Keene says. “With the horizontal grinder, I can use an excavator and chain to maneuver it into position.”

Good Maintenance Pays
Currently, he owns a model 3680 Beast Recycler, made by Bandit Industries Inc. The production rate varies, depending on how green or dry the woodwaste is. “Generally, it processes the material about as fast as we want,” Keene says. “However, a mix of the stumps, logs, and brush works better than either all brush or all stumps.”

He grinds all the material using a 4-inch screen. He lets the material sit for several months, depending on moisture content before running it through the grinder again, usually with a 2-inch screen. However, for his premium compost product, Keene uses a finer screen. After this second processing, he places the processed material in windrows to a height of about 15 feet with a loader, where it composts.

“Grinders are expensive machines to own and operate,” Keene says. “They suck up fuel and they beat themselves up. But all the grinders I’ve owned have been good machines. They have a lot of wear points. However, if you’re careful and you keep the machine within the required tolerances, they can go a pretty long time before they require any major maintenance.” One key to successful operation of a grinder, Keene reports, is strong support from the manufacturer. “That’s essential because downtime will kill your profits.”
About the Author

Greg Northcutt

Greg Northcutt writes frequently on construction and business issues.

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