With the unprecedented growth of the construction and demolition industries, there has been an equally unprecedented increase in the amount of C&D debris that must be disposed of. As a result, more and more companies appear to be specializing in the recycling and/or disposal of C&D debris using specialized new equipment.

By Charles D. Bader

With the world's continued explosive growth and our growing penchant for replacing rather than preserving existing structures, the amount of construction-and-demolition (C&D) debris being generated each year has been increasing significantly. How significantly? No one seems to know exactly. The Construction Materials Recycling Association (CMRA) of Lisle, IL, estimates that 320 million tons of C&D debris are being generated each year but concedes that this is just an estimate based on the eight-year-old EPA study that continues to be the accepted baseline.

The CMRA estimate might be quite low, too. The Florida Department of Environmental Protection is conducting an ongoing study of C&D debris recycling, and the most recent update (February 2, 2004) contained the following paragraph:

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The U.S. EPA sponsored a study to estimate the amount of building-related C&D debris waste in the U.S. in 1996. The study was performed using census bureau statistics and using known information on waste generation from different types of construction projects. This study provided much needed information on the amount of C&D waste produced in the U.S. The study also provided a methodology for estimating building-related C&D waste. Research funded by the Florida Center for Solid and Hazardous Waste is currently underway to perform a similar estimate for Florida. Initial results indicate that the relative contribution of construction is much higher in Florida than the national estimate. If the contribution of C&D waste is added to the remainder of the municipal solid waste stream in the U.S., C&D waste is found to account for 37% of the total municipal waste generated.

Not much of this C&D debris is being recycled either. The 1996 EPA study estimated that only 20­30% of building-related debris was being recycled, and two years later that percentage hadn't improved much. In that year, for example, the Florida study determined that the state had recovered just "3.3 million tons (35%) of the 9.4 million tons of C&D debris that was generated. Concrete (58%), asphalt (33%), and wood (8%) constituted, by far, the largest portion of overall C&D debris recovered in 1998. Figure 1 depicts the C&D debris management method and materials that accounted for the largest portion of C&D debris generated during 1998."

The recovery percentage seems to be increasing now, although there are no reliable statistics to verify this feeling. William Turley, CMRA's executive director, credits a growing trend toward new technology in C&D recycling. "Today," he says, "C&D recycling techniques have really advanced. For those facilities processing mixed C&D, there are still simple dump-and-pick sites working. But all the new operations coming on-line have advanced sorting techniques that allow a more-thorough separation of materials. This allows for creation of more added-value products, which is where the industry should be headed in the future in order to be more profitable."

New Module Design

New equipment is coming on the market to both streamline C&D debris processing and permit lower operator recycling costs and break-even levels. Andrew LaVeine, president of Action Equipment Company Inc. in Newberg, OR, points to the advantages of his company's patented Taper-Slot finger screens over traditional disc screens and trommels in removing fines from a flow of C&D debris and feeding material to the sort line.

"The Taper-Slot screen is designed with lateral wedge deflectors that prevent the material from shifting laterally and thereby catching under or wrapping around fingertips," he explains. "Not only does this allow the screen to remain clean for maximum screening efficiency, but it effectively reduces unwanted stoppages and downtime. These strong, durable wedge deflectors also prevent longer, often oversize materials from shifting under a fingertip and falling into the 'accepts.'

"Overall, the Taper-Slot screen helps even the flow to the sort line so that the pickers can separate recyclable materials more effectively. The screen can easily support a 250-cubic-yard-per-hour line flow, but equally important, it can handle surges of up to 500 yards per hour."

LaVeine's understandable enthusiasm seems to be shared by turnkey systems suppliers and users alike. Firms such as Continental Biomass Industries (CBI) of Newton, NH, routinely design Taper-Slot screens into their C&D debris recycling systems, and Ken Foley, owner of Pond View Recycling in East Providence, RI, describes his Taper-Slot screens simply as "the best in the industry." LaVeine's contention that "the Taper-Slot screen has become a dominant force in the marketplace for processors interested in processing C&D waste efficiently" might be credible.

Another piece of equipment that has been developed for the C&D debris processing market to permit improved performance is the slow-speed, high-torque shredder. A good example is the ShredMaster line of 200-, 450-, and 750-horsepower shredders manufactured by large-assembly manufacturer RBA Inc. and distributed by Rosenthal Industries, both of Manitowoc, WI. The 11-inch-diameter shafts generate up to 214,000 foot-pounds of torque at slow speeds that reduce noise, dust, and vibration. These low-speed, twin-shaft shredders are capable of shredding 50­150 tons per hour of mixed, bulky material to be shredded without presorting. If C&D material that cannot be shredded is fed into one of these shredders, an automatic reverse function is activated to enable it to be removed before any damage is done.

CBI also manufactures a large (with 250,000 foot-pounds of torque) shredder that the company calls the Annihilator. This shredder is a slow-speed, single-rotor shredder with an adjustable anvil so the operator can change the sizing of the product to accommodate downstream equipment capabilities or to customize the shred size for differing feed characteristics created by different markets. According to CBI Regional Sales Manager Aaron Benway, the 8-foot-wide by 10-foot, 4-inch-long shredding container houses a 20,000-pound rotor, which is a drum made of 6-inch-thick forged steel. The rotor has machined grooves for placement of 42 hammers, each weighing 95 pounds and having a forged-steel, bolt-on reversible tip.

"The 8,000-pound anvil, which is attached to the Annihilator shredding chamber, has a cutting gap that instantaneously adjusts to accommodate varying feed stocks and desired end-product sizes," Benway says. "The cutting gap can be adjusted during operation, either by remote radio control or automatically in a jam condition, all to prevent shutdown. We believe the Annihilator provides the highest throughput, best durability, lowest maintenance costs, and lowest cost of ownership of any primary shredder available."

Another interesting equipment module now used in processing C&D debris is the single-knife destoner/classifier manufactured by General Kinematics Corporation of Barrington, IL. This equipment provides a method of separating and classifying a wide range of recycled materials. For C&D debris processing, destoners/classifiers have addressed the need for clean, salable materials.

According to General Kinematics' Vice President of Sales & Marketing Bill Guptail, "Our classifier is a sophisticated yet simple unit for sorting heavy materials normally found in C&D wastestreams. The unit uses air streams to separate materials according to differences in density. The result is fast, efficient removal of heavy materials such as stones, metals, and glass from lightweight materials such as aluminum, paper, plastics, and wood - even shingles which are classified as a light material due to their size and relatively light bulk density." Guptail adds that the company's vibratory classifying equipment is typically used in dry systems but also can be adapted to handle wet materials and works well where mist or water is used to control dust.

Turnkey Systems

Although advances in equipment capabilities such as these have certainly bolstered the ability to cost-effectively process C&D debris, even-greater improvements have resulted from the configuration of systems that combine screens, shredders, classifiers, magnets, grinders, and pickers with conveyors to effectively create disassembly lines to continuously process incoming C&D debris.

There is no single system configuration equally effective for all applications, of course. Because such factors as size, location, type of debris, market demand, capital cost tolerance, and operating budgets can significantly vary from area to area and from jurisdiction to jurisdiction, design of any specific C&D debris processing system involves - or should involve - careful professional engineering. That said, it is equally true that there are patterns in successful operating systems that make them successful and can be useful in providing a general roadmap for municipalities and private developers to observe in the planning and design of new systems.

One design that has earned such scrutiny is that of Sherbrooke OEM Ltd. of Sherbrooke, PQ, in partnership with General Kinematics. The two companies have teamed up to offer C&D material recovery facilities (MRFs) the capability to process 500 cubic yards of material per hour. The highly automated custom-engineered dry processing systems include these:

• Dual finger screens that receive and size material at 6 inches
• Heavy-duty apron conveyors to elevate and transfer material to a trommel and picking platform
• A picking deck with parallel lines to increase productivity and bunker utilization
• A dual-knife destoner/classifier for –8- to +2-inch material separation and clean aggregate production

These are the basic equipment modules of the system design, although additional equipment such as magnets can be integrated where the feedstock justifies such additions. The two firms have recently designed and built two new C&D MRFs using this design for Sun Recycling in West Palm Beach and Dania, FL. According to the firms, the system design and the dry recycling process "address both capacity and product quality. The result: highly automated custom-engineered systems to receive and size material. After the initial cut, the process continues with heavy-duty conveyors that elevate and transfer material to a picking platform. The elevated picking deck, designed and manufactured by Sherbrooke O.E.M., Ltd., includes parallel lines to increase productivity. Working in tandem, these systems addressed Sun's need for high throughput with labor-saving, automated sorting of materials, and more efficient manual picking and sorting."

Each of the new systems includes a vibratory classifier. In addition to increased throughput, the classifiers in the Sun C&D recycling system have resolved the rock and shingle contamination problem and addressed the need for clean aggregate. The General Kinematics units were designed to improve material separation and enhance aggregate production by removing paper, plastics, shingles, and other light materials.

Erin Systems of Riviere-du-Loup, PQ, is perhaps best known for its innovative mobile and fixed screening systems: the Starscreener, the Fingerscreener, the Fingertrommel, and the Trident models. However, the company also offers complete fixed C&D debris recycling systems that are individually engineered and customized to meet the needs of both large and small C&D recyclers, according to Engineering Manager Bruno Lagace. "Based on its Fingerscreener platform, each C&D debris recycling system will integrate sorting lines, magnets, conveyors, screeners, grinders, et cetera. To best bring innovative solutions to the market through research and development initiatives and strategic alliances, our goal is to offer a complete range of equipment to its customers.

"This is why we just introduced our range of track-mounted crushers, including the Powercrusher Jaw and the Powercrusher Impactor. The Powercrusher Jaw features a 'Quattro-movement' that increases the efficiency of the crushing where material enters the crusher and also ensures secondary crushing at the outlet of the crusher. The 'Quattro-movement' guarantees a highly efficient production rate at every setting and produces more cubically shaped materials. The versatility of this crusher is such that it can crush 0/70 millimeters and eliminate the need for secondary crushing. The Powercrusher Impactor was originally designed for and is still being used as a primary crusher in recycling. With the development of more effective wear parts, however, the Powercrusher Impactor is now being used more and more as a secondary crusher in hard-rock applications where up to two crushing stages can be replaced. Depending on the model, the Powercrusher Impactor can achieve a crushing capacity ranging from 222 to 550 tons per hour.

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"We maintain this broad product line because we have learned that our customers have such different needs. Some want to simply separate the fines for sale as ADC [alternative daily cover]; at the other end of the spectrum are customers who want to turn almost all of their feedstock into ADC and in the process remove ferrous metals, cardboard, wood, and aggregate - anything they can recycle. Those are widely varying needs, and we want to be in a position to configure systems that can effectively address those needs."

A good example of this latter type of processor is Jim Stewart, general manager of Environmental Alternative Recycling of Baltimore, MD. "With scrap metal selling for $130 a ton and cardboard at $85 a ton, separation for recycling is paying off well, even though the demolition contractors are pulling out big-ticket recyclables like structural steel before we get it. But we have always recycled when the price is right. Our criterion for what recyclables we will bother to separate is simple: will the revenue from the sale of that recyclable support our labor cost of separation? So we keep constant track of both market conditions and what our current operating costs are running."

Today, that means separating virtually everything, he says. He uses a turnkey Erin system rather than attempting to assemble system modules himself. The system works like this, he says:

1. Manually pull out the big stuff like rolls of carpet and big timbers.
2. Using an excavator with a rotating grapple, transfer the balance to the finger screen.
3. Screen out the 1.5-inch plus.
4. Trommel out the 3/8-inch plus for sale as ADC and store the 3/8-inch minus for future incorporation into recycled aggregate.
5. Convey the 1.5-inch plus to the sorting line.
6. Manually pull out the wood, metal, concrete, block, and gypsum.
7. Package these recyclables for market or incorporate them into a salable product, such as aggregate.
8. Take recovered concrete, soil, brick, and block and crush it with the Powercrusher Jaw to produce a marketable aggregate.
9. Transfer residuals to wide-body trailers and send them to the landfill.

"We can pull out quite a lot of recyclables that way," he says. "If the feedstock is principally demolition debris, we usually pull out 50% by weight. If it's primarily debris from light construction, we'll recycle about 37% under current conditions. We don't break up the residuals that are going to the landfill. It doesn't pay off. With over-the-highway transportation by trailers, the load will weight out before it cubes out, so we let the landfill compact the residuals. We avoid a needless cost, and many landfills prefer noncompacted debris."

CBI designs, engineers, manufactures (or procures), and installs state-of-the-art C&D debris recycling systems that can include its Annihilator slow-speed shredder, grinders, multiple screens, picking stations, float tanks, magnets, and a system of conveyors to link and coordinate these elements. The design process includes accurate throughput estimates based on each user's feedstock makeup and quantity and on the desired degree of recycling.

Among the most comprehensive C&D debris processing systems is CBI's system for ABC Disposal in New Bedford, MA. It's a big plant, currently permitted to accept 500 tons per day but capable of accepting 1,500 tons per day. Currently, New Bedford Waste Services recycles 95% of its C&D debris by pulling out metals, wood, cardboard, aggregate materials, and fines for ADC.

Material for C&D processing is first inspected for hazardous materials and large metal objects by the operator of the excavator feeding the system. These are removed, and the balance goes to a CBI Annihilator shredder for initial breakdown. Two pickers are situated by the line leading to the shredder in order to remove paints, propane bottles, or other contaminants. Equipped with a video monitor, an operator station near the shredder enables an operator to safely oversee the loading operation, and an operator key monitor at the station of the pre-grinder operator oversees the loading operation. If a large piece of metal gets by the pre-inspection, that operator can see it and reverse the machine. The anvil door on the Annihilator can then be opened for problematic items, allowing them to drop out, thereby bypassing the pre-grinder.

The ground material is then passed on to a 6-inch Taper-Slot vibratory screen that separates the 6- to 9-inch products from the rest of the flow. The screened fines and overs are diverted into separate lines that pass under two large magnets positioned to remove any metals. The fines are conveyed to a second shaker screen to separate out the 2-inch minus. The overs are conveyed to eight picking stations where clean wood, trash, aggregates, and metals are pulled.

After being picked, the separated material goes on a reversible transfer belt either into a float tank or, if wood is being run to produce fuel, into a high-speed grinder. Like the picking lines and belts, this grinder is supplied by CBI. The entire operation runs so smoothly and efficiently that the plant can recycle that high percentage of debris and do it profitably.

"That's certainly a far cry from the old days when an operator would presort on the tipping floor and handpick as much as possible, and then push the rest into a pile where a compactor or dozer would track over it to break it down in size for the landfill," Benway recalls. "Maybe they would have a grinder to reduce the volume and/or produce ADC material. But today, there are very effective systems that go well beyond this and can be custom-tailored to each customer's performance and budget requirements.

"The key to such a system is the sequence and timing of Shred-Screen-Pick-Grind. As you can see [Figure 2], if all the basic equipment is sized right and the conveyors are timed right, you can get a continuous flow of material that can be effectively separated for the most cost-effective operation. Where one commodity - wood, for example - is valuable and plentiful in the feedstock, we can add a dedicated conveyor so that pickers can divert this commodity as well as pick their primary pick materials. And, of course, the system can be tweaked for changing market conditions."

Not Everyone Recycles C&D

In some situations, revenue from extensive recycling of C&D debris doesn't justify the cost of separating and marketing those materials. Currently, National Waste Service LLC of Bayshore, NY, is in that position. According to Chief Operating Officer Dick Leone, his small transfer station only pulls out the metals from the largely source-separated feedstock (manually, he hasn't implemented a magnet yet) and sends the balance to a local landfill. However, he does have a ShredMaster there to reduce the size of the debris to 12-inch minus. Why? Because that is the maximum size that will be accepted by this particular landfill, and it offers attractive tipping fees. In the process of the shredding, National recovers 2-inch minus fines, which it provides to the landfill for ADC for an additional discount.

Gene Rosenthal of Rosenthal Industries is finding many customers who send virtually all of their collected C&D debris to landfills. "Mostly, they are transfer station operators near big East Coast cities," he says. Since the land is so expensive in these cities, buildings are continually being pulled down and replaced by bigger and/or more-efficient buildings. That translates to a lot of demolition debris located far from landfills that will economically accept it - or accept it at all.

"Therefore, more and more transfer stations are being built with rail connections. Demolition contractors load big rolloffs to transport the debris to these transfer stations. Usually the only recycling they do there is to pull off the cardboard and ferrous metals that the demo contractor hasn't source picked. The only processing of C&D debris that these transfer stations perform is to shred the debris. That enables the loads to be so much more compact that it takes 65 to 70% of the air out of the loaded railroad car. And that means they can almost double the amount of debris each car can hold. You don't pay by weight in railroad freight transportation; you pay by the number of carloads. Therefore, shredding saves a lot of money when you're shipping debris to Ohio."

Clearly, a lot of C&D debris is still going to landfills despite the inroads being made by recycling with modern technology. Anecdotally, diversion rates of more than 90% have been reported, but apparently conditions have to be just right, markets have to be strong, jurisdictions have to be supportive, and profits have to be secondary considerations. While there is little data to determine how much C&D debris is going into landfills today, it seems likely that with the significant increase in C&D projects today, the percentage recycling increases have not reduced the amount of C&D being landfilled from the 61 million tons estimated by EPA for 1996.       

Charles D. Bader is with Dateline II Communications in Los Angeles, CA.

MSW - July/August 2004