Where The Rubble Meets The Road

While most recycling programs concentrate on the basics -paper, aluminum, glass, plastic and green wastes - you may be missing another important segment of the waste stream, one with rich concentrations of fairly consistent materials that can be processed and sold to a growing market: construction and demolition (C&D) wastes.

Before diving into a C&D debris recycling program, you must thoroughly understand the materials in your waste stream. C&D wastes primarily consist of wood, concrete, asphalt and brick, with smaller amounts of corrugated cardboard, metals and roofing materials. While the specific quantities generated will vary, most of the materials in residential construction are wood while in commercial structures, concrete, brick and metal will predominate.

C&D materials are transported from the site to the disposal facility or processor in either a dump truck/ trailer or roll-off container. Most roll-off containers range from 10 to 50-yard boxes; the smaller is used for inerts such as concrete and asphalt (C&A), and the larger is used for lighter materials such as wood and gypsum board.

It is easier to divert waste at construction rather than a demolition sites. Construction involves ordered activities using a single material type. For example, when homes are being framed, large amounts of clean wood wastes may be generated while gypsum wallboard will be discarded during finishing. However, cardboard may be generated throughout the project.

Separation activities during demolition generally are more difficult, since the activity involves taking a single structure comprised of all the materials mixed together, with the objective of removing the structure as quickly as possible. While some salvaging of higher-value materials such as copper wiring, piping and architectural features may occur prior to demolition, generally a bulldozer is the principal method for reducing the structure for removal.

The result is a mix of materials which may have higher levels of contamination such as treated wood, asbestos and lead paint. This material becomes nearly impossible to separate economically.

Controlled demolition, where materials are kept separate, may be easier to recycle but is more expensive. For example, a contractor could identify a building's hazardous materials, such as asbestos and lead paint. After these items are removed, the roofing tiles, shingles, gypsum wallboard, copper wiring and plumbing, could be collected. At this point, mostly wood, brick or concrete would remain.

A two-stage demolition involves removing wood and brick from the infrastructure, followed by the foundation and base materials, including concrete or asphalt.

The cost of controlled versus mass demolition must be weighed against disposal costs and local waste diversion mandates to determine the most cost-effective approach. If landfill disposal costs $70 per ton or more, controlled demolition may be more cost effective.

To Processor, To Processor Make sure a market exists for the separated materials prior to separation. C&D processing markets vary regionally: In areas with high tipping fees or several waste processors, there may be outlets for handling C&D.

In some areas, the market may be slim, and only a major disaster would create markets. For example, only after the 1993 Northridge earthquake did C&D processing bloom in the Los Angeles area.

Overall, the C&D processing market is growing rapidly, although some material markets are growing faster than others. "That [the market is] rapidly expanding is an understatement," said William Turley, executive director of the Construction Materials Recycling Association, Chicago, and editor of C&D Debris Recycling Magazine. "There is a lot of concrete and asphalt recycling taking place in North America," he continued.

"While it's pretty much an established market in most areas, other materials like wood, gypsum and shingles are not processed, reused or recycled. Many waste management officials are waking up to the opportunity to get rid of this stuff, reuse it, keep it out of landfills and provide more jobs."

C&A recycling involves reducing the material to a size appropriate for use as aggregate, base material or other size-specific uses. Asphalt processing includes reincorporating the material into or other asphalt products.

While the wood markets initially focused on boiler fuels, the current trend is toward value-added products, like high-quality garden mulches and as feed stocks for particle board manufacturing. "There are a lot of higher-end products being developed, but they usually only can use the clean construction wood," said Turley. "Demolition wood is more of a problem. There aren't any good systems for getting all of the contaminants out yet, so that limits your markets. Gypsum has the same problem."

By focusing on the production of higher quality materials, it is possible to drive the demand for finished products faster than the supply of raw materials and thus command higher prices. For example, one former landscape company in Ephrata, Penn. started producing its own mulch after experiencing quality problems with other producers.

"At first, we worked with bark from saw mills," recalled Martin Mulch owner John Martin. "In 1989, we started taking recycled wood, because we were looking for more product base to make mulch. We deal primarily in clean wood recycling, [which is] wood that's not painted or treated. We do not get into a lot of demolition because the demolition people don't understand that 'wood' doesn't mean windows, plaster board or carpet."

Martin said that by understanding the end user's requirements and maintaining tight quality standards, their end product market has grown significantly. "We had the benefit of knowing what we wanted in an end product before we started, so we have never had a problem marketing it," Martin said. "In fact, we have had more of a problem producing enough [mulch]. We have a waiting list, and some people wait from one to two years just to get on our list of customers. Over the last four years, the company has been averaging 10 percent to 15 percent growth per year - all by word of mouth and satisfied customers."

Education is the key to successful processing, and Martin's company works cooperatively with local waste management firms to expand the raw material supply, especially since the state passed a law prohibiting landfilling of clean wood.

So, You Want To Be A Processor In order to establish a C&D processing operation, you should understand the marketable finished product. It's not enough that a processor may make some income off the tipping fee. If there is no end user for the products, the stockpiles of unsalable materials will attract the unfavorable attention of local land use officials and regulators.

Once you've established end markets, you should identify the equipment necessary to process the material to the desired specification. You must determine which equipment can reduce the feed stock to size specifications and can handle the projected volume.

Do you intend to have the material brought to a central location, or will you travel to a job site? "If you are going to be stationary and you want to set up a facility, you need to know how many acres you'll be working on," stressed Larry Horwedel, vice president of Excel Machinery, Amarillo, Texas. "Are you close to the raw materials, and do you have good freeway access to a location where you want to set up?

What about the investment? The minimum to establish a portable recycling business would be around $300,000 if you're going to buy a plant, screens, conveyors and everything else. You might do it for $250,000, but if you invest less than that, you're going to be asking for problems."

Know Your Grinders For processing wood waste, the grinder's type, capacity and operation must be considered. There are principally two types:

* Tub grinders. An open tub turns around, feeding material against a set of rotating teeth in the tub's base. The material is sheared off, falling through to a conveyor which removes the material to a stock pile. The tub grinder usually is fed in batches, with the material being loaded by a wheeled loader through the tub's top.

* Enclosed hammermills. Material is fed into a rotating set of hammers which pulverize it with repeated strikes. Then, it is fed onto a conveyor which delivers it into an enclosed hopper.

Whatever grinder is selected, it's important that it produce the desired size, often using a set of interchangable screens.

Making sure that the type of equipment acquired is appropriate for the type of material to be processed is critical. For example, while most wood type products can be fed into either grinder type, asphalt shingles are not recommended for hammermill processing. "It creates high wear because it's very abrasive," noted Wally Zinck, general manager of Jeffrey Processing, Woodruff, S.C. "Things like that are best separated from the feed stock. It's going to go into a landfill anyway, so you're not facilitating the landfilling because you're not reducing volume by running it through the hammermill."

Understanding the safety aspects of the individual equipment types and the clearance areas necessary for safe operation should also be considered.

The future for C&D processing is growing brighter, according to Turley, who expects diversification within the industry to grow. "What I am seeing is diversification by C&A processors into other materials," he predicted. "They will try shingles, tires and gypsum. I expect that the use of recycled wood will increase as people discover new ways to use it in higher-value products.

"They're already in the construction materials recycling business, so this a natural extension."