When the Price is Right

In its textbook Recycling of Demolished Concrete and Masonry, the International Union of Testing and Research Laboratories for Materials and Structures (RILEM), Paris, credits jaw crushers as providing “the best grain-size distribution of recycled aggregate for concrete production.”

Horizontal rotor impactors, on the other hand, “are less sensitive to material that cannot be crushed, such as [steel] reinforcing bar,” according to RILEM. Impactor plants that include belt magnets to draw out the steel re-bar have become common configurations used to recycle stretches of concrete highway, creating a re-usable secondary aggregate and a scrap steel product.

BUYING FOR DIFFERENT REASONS

Compiling a profile of the “typical” concrete crusher purchaser would yield a rather schizophrenic result, since buyers come from several different industries.

Whether the buyer is a paving contractor, a quarry operator, or an entrepreneur who intends to make concrete and asphalt crushing the focus of his or her business makes a difference in what type of machine might be most advantageous.

Trade associations and other interested parties are just now devising methods to track the amount of concrete and asphalt being crushed by the nation’s demolition and construction contractors, road building contractors, quarry operators and stand-alone crusher operators. But participants in all of those segments agree that the volume of concrete and asphalt material being recycled in North America has increased tremendously compared to just ten years ago.

In a series of case studies conducted by Kolberg-Pioneer Inc., Yankton, S.D., contractors gave a variety of reasons why the economic incentives now exist to recycle concrete and asphalt instead of burying it.

The experience of the Fucinaro family, operators of Conreco (Concrete Recycling Co.), Omaha, Neb., is typical. Conreco was started in 1992 as an offshoot of Fucinaro Excavating, the family’s original business.

Conreco was initially formed to process the concrete and asphalt rubble generated by the excavating company on paving and tear-out job sites, because nearby landfills were closing or charging higher fees.

According to Fucinaro brothers Ron, Dave and Mike, the benefits offered by Conreco include “minimized trucking costs, reduced tipping fees compared to the landfill options, and providing a reliable inner-city source of aggregates for area contractors.”

Today, half of the company’s feedstock comes from other contractors. “Everybody is charged a tipping fee of $20 per tandem truck load,” says Ron Fucinaro. “We sell the crushed products to virtually every contractor in the city.”

As with the infeed percentage, Fucinaro Excavating absorbs half of the end product, “because we search out projects that have a need for larger quantities of crushed stone,” says Ron.

On the asphalt side, the experiences of Commercial Asphalt Co., Maple Grove, Minn., would be typical. The company, which produces several million tons annually of hot mix asphalt, has seen the role of recycled asphalt pavement (RAP) grow “from almost nothing in the mid to late 1970s to where it is today: an annual volume of several hundred thousand tons—or nearly 15% of total material produced,” according to a Kolberg-Pioneer case study.

Commercial Asphalt Co. operates 11 hot mix plants in the Twin Cities metropolitan area, and the company’s officers are supportive of RAP’s use in their products. “Because recycling is so well-suited to our industry, both from an environmental and an economic standpoint, we have seen the use of RAP grow steadily over the years and have worked hard to promote that growth,” says company sales manager Joe Winkel.

Once a company makes the determination to buy a crusher, several factors come into play. Among those considerations:

As one example, an impact crusher may make the most sense for a plant that will handle predominantly asphalt. Jim Herles, a sales representative for Nordberg America Corp., Milwaukee, notes that in most cases, “someone who is running 50% or more asphalt should consider an impactor.”

Larry Horwedel of Excel Machinery Ltd., Amarillo, Texas, agrees. “Most of the time for asphalt, an impactor is the best. Using a jaw somewhere like Ohio where there is a lot of bituminous material, you’d tend not to use a jaw or cone because it could stick a lot.”

Regarding volume considerations, Horwedel warns purchasers not to get caught with too little capacity to take on major jobs. “The small plants sometimes just don’t offer enough production. If the customer wants 2,000 tons per day sitting on the ground, you’d better have a plant that can handle it.”

Horwedel notes that in road building applications in particular, “time is money in that business, so the customer is not going to be able to wait all day for you.”

Other factors that can’t be ignored are the rock and soil qualities of the region where the crushing activity is taking place. “There are regions such as Atlanta where there is a lot of granite, and it costs more to crush granite because it is so abrasive.”

The specifications for the end product creates another important consideration, especially since these specifications vary from state to state.

Finally, those same specifications come into play when screening equipment is selected to produce the end product.

THE URBAN FOREST

The massive movement toward the recycling of concrete and asphalt is not the only C&D recycling success story from the last two decades.

Another material stream emanating from demolition projects, construction sites, and lots being cleared for construction is waste wood, most of which can be shredded and recycled if there is an economically viable reason.

Wood grinders are often categorized by the shape of their infeed systems, with tub grinders having circular, tub-shaped hoppers, and horizontal grinders configured in a straight line with material conveyed into a waiting rotor or hammermill.

Tub grinders are configured with a large, circular-shaped infeed tub that narrows down like a funnel leading toward a rotary grinding unit at the bottom of the funnel. Morbark Sales Corp., Winn, Mich., makes several models of tub grinders with varying processing capacities.

The company’s Model 1500 tub grinder can process up to 500 cubic yards per hour of waste wood (depending on the type of wood being fed), including C&D debris wood and old pallets. One drawback sometimes associated with tub grinders is the open-topped tub itself. Although the open top allows for the easy feeding of material, it also permits material that is “kicked back” by the rotor to occasionally shoot up and out of the tub, posing a safety threat to machine operators and others working nearby.

This is one of the reasons both Morbark and several competitors now offer horizontally-fed grinders, featuring conveyors that are covered close to the rotor, or infeed hoppers that are more rectangular in shape and narrow down to a “slit” opening. Ideally, either configuration offers less of a chance for material to be thrown away from the machine.

Wood grinders can come in a variety of sizes, allowing demolition contractors as well as large volume wood recyclers the ability to choose a machine that should closely match their anticipated production volume.

The material produced is most often marketed as landscape mulch or wood chips for landscape or other ground cover purposes. Processors of C&D wood waste now commonly add a coloring system to the back end of the grinding process to produce a more desirable landscaping product.

Peterson Pacific Corp., Eugene, Ore., has its equipment background in chip plants for the pulp and paper industries, but according to marketing manager Dave Benton, the company has met with a good response to its line of heavy-duty grinding machines marketed toward the recycling industry.

The company’s highest volume machine, the HC 5400 Recycler, features a rotor that is more than five feet wide and carries 28 fixed hammers powered by a 575 or 800 horsepower engine. When configured with the more powerful engine, the machine can process 75 tons of C&D debris per hour.

Portable units and other smaller grinders can accommodate processors of smaller amounts of wood. Many manufacturers in the green waste and brush chipping segment have introduced models that have been “toughened up” to accept waste wood, while other manufacturers produce smaller models designed to handle the diverse types of wood emanating from the C&D stream.

The Tryco/Untha Model LR-700 shredder, from Tryco/Untha, Decatur, Ill., is a ram-fed grinder with an auger removal system. Boards (including wallboard, plywood and virtually any type of hard or soft wood), drop-offs, panes and blocks can be reduced to mulch, bedding or fuel with the shredder. Hardened steel cutters, mounted in replaceable holders, operate quietly at 80 decibels and move at a slow 96 rpm pace. The company also offers Untha models in larger sizes, including one that can process 14,000 pounds per hour.

As with concrete and asphalt, a general shift away from landfilling wood waste that can be reduced in size and sold has helped this shredding equipment segment grow steadily in the past 10 years.

The author is editor of Recycling Today.