A soup-to-nuts guide to construction-and-demolition recycling options

By Chuck McLendon, Timothy G. Townsend, and Kimberly M. Cochran

Although most communities have implemented methods to manage and recycle traditional refuse, many communities are only now beginning to focus on the construction and demolition (C&D) debris stream. C&D debris includes materials such as concrete, asphalt, wood, gypsum drywall, and metals generated from the construction, renovation, or demolition of roads and structures.

Why Focus on C&D?

Why this recent interest in focusing on C&D? The answer is, quite simply, because C&D debris represents such a large percentage of the wastestream. The Construction Materials Recycling Association estimates that C&D debris accounts for 25-45% of the overall North American wastestream–depending on the region under consideration. For areas with heavy development/construction activity, focusing on the C&D debris stream is particularly beneficial.

The composition of C&D debris varies greatly across the country and is impacted by the types of C&D activities and the types of building materials used in each region. For example, houses built in the central and southern regions of Florida are generally built with concrete block frames, while houses in the northern region of the state are generally wood-frame. Consequently, C&D debris in the central and southern regions contains a large amount of concrete, while C&D debris of the northern region contains a large amount of wood. Because of these variances, recycling efforts must be local and tailored specifically to each region's characteristics to be effective.

Innovative Diversion Strategies

Because C&D debris represents such a large portion of the wastestream, communities are now seriously looking for ways to reduce the stream in order to meet diversion goals:

Diversion Deposits. Diversion deposits have been employed in some communities to encourage C&D recycling. Building departments require deposits from contractors seeking building permits. If the waste material from the construction, renovation, or demolition job is recycled, the deposit is refunded to the contractor.

Waste Management Plans. A number of communities require contractors to develop a waste management plan that must first be approved by their clients.

Taxes. Taxes are another incentive to recycle C&D debris. Some communities are implementing a "waste tax" on all waste coming into the landfill. The tax can be avoided by recycling.

New Techniques. Georgia is promoting the development of small cleanup crew businesses, as opposed to traditional hauled container services, that can separate materials more efficiently than a C&D debris disposal or recycling facility.

Reclassification. Some states are considering classifying C&D debris as its own wastestream, requiring C&D debris to have its own diversion goals. Because C&D debris is quite different from MSW in its composition and handling, treating it as its own wastestream is justified.

Breaking Down Deconstruction

One concept gaining popularity in many localities is deconstruction. Rather than simply demolishing structures, there has been increased interest in systematically dismantling structures that might contain valuable building materials. The valuable materials are carefully removed from the structure and reused in new construction or renovation. The materials being targeted might be valuable from one of two perspectives: either because of the inherent quality of the material as compared to a similar product today (such as wood timbers) or because of the material's historical value (such as stained-glass windows). Historical districts in some communities require the use of older materials in new construction and renovation in order to fit in with existing architecture. The number of reuse centers and architectural salvage stores continues to grow.

There are two approaches to deconstruction: removal of valuable materials at the job site or removal of the materials at a mixed C&D debris facility. The advantage to removing materials at a mixed C&D debris facility is that the normal routine at the job site doesn't change. The disadvantage, however, is that more energy and effort are needed for separation, and if not done correctly, the condition of the materials might diminish and the value will be lower. The advantage of separating materials at the job site is that separation will be better and easier. The quality of the material will be higher, having not mixed with other materials that might contaminate them. The disadvantage is that contractors must conduct the deconstruction and are often reluctant to do so for economic reasons. Demolition contractors have historically performed limited deconstruction. Deconstruction makes sense for some buildings, but not all. It depends on the value of the materials and the labor and hauling costs associated with them.

Smells Like Drywall

Gypsum drywall typically represents anywhere from 5% to 15% of the C&D debris disposal stream. Until recently, there have been very limited attempts–largely focused in the Pacific Northwest–to recycle this material. In recent years, however, drywall disposal and decomposition has been identified as the source of odor problems at C&D debris landfills. Drywall is already banned from disposal in some parts of Canada. The odor issue has resulted in increased interest in methods and end-uses to recycle drywall. The Florida Department of Environmental Protection has recently provided a series of grants to Florida counties interested in drywall recycling. While the grants have resulted in some promising opportunities, the low cost of C&D debris disposal combined with a relatively inexpensive raw material (gypsum) continue to be major barriers to more widespread drywall recycling.

Wood Recycling Under Pressure

Pressure-treated wood made with chromated copper arsenate (CCA) has been of great concern due to the amount of arsenic, a known carcinogen, in the wood. CCA-treated wood is frequently used in construction and ends up in C&D debris landfills as construction, renovation, or demolition waste. In C&D debris landfills, CCA leaches from the wood and mixes with the landfill leachate. Many C&D debris landfills in the country are not lined and cannot prevent the leachate from entering the groundwater. Studies performed by the University of Florida have shown that leachate from C&D landfills may exceed the primary drinking-water standards for arsenic. Minnesota has banned CCA-treated wood from its demolition landfills due to the high level of arsenic found in the leachate.

CCA-treated wood can also pose a problem for wood recycling. Two major C&D wood recycling options are mulch and fuel. CCA-treated wood, when weathered, is usually indiscernible from untreated wood, and when it's recycled, often it is mixed in with untreated wood. When recycled as mulch, it has the potential of endangering children who put dirt and their hands in their mouths after making contact with the wood.

When CCA-treated wood is burned as fuel, the resulting ash often has high levels of arsenic. The ash must then be treated as a hazardous waste. Recently the Environmental Protection Agency and the pressure-treated wood industry have decided to phase out CCA-treated wood due to the potential hazards it poses. There is still a large quantity of CCA-treated wood out there that must be managed at the end of its useful life. One study conducted in Sarasota County, FL, involved developing technologies to sort CCA-treated wood from untreated wood. In this study, a laser detector was attached to a conveyor belt to determine whether the wood was treated. More information about studies involving CCA-treated wood can be found at www.ccaresearch.org.

Roofs to Roads

Asphalt shingles are another major component of C&D debris, but very little of this material is recycled. In a recent study performed in Florida, asphalt shingles represented 7% (283,000 tons) of the total building-related C&D debris stream, but only 1% of that amount (3,000 tons) was recycled.

Asphalt shingles can be recycled into new hot-mix asphalt, which is used in road construction. It can represent 5% of the total mass of asphalt concrete, though some studies have shown that as much as 10% is possible. The study performed in Florida showed that the market for asphalt concrete is so high that all of the waste asphalt shingles generated in Florida could be recycled in this manner. The biggest obstacle for asphalt-shingle recycling has been fear that the shingles contain asbestos. While many older asphalt shingle products contain asbestos, United States recyclers rarely encounter asbestos in tear-off tab shingles. For more information on asphalt shingle recycling, go to www.shinglerecycling.org.

Baling for the Long Haul

With the increasing difficulty of siting new solid waste management facilities, the concept of long-hauling waste, including C&D debris, is gaining attention. One new technology considered by many C&D debris transfer station operators is the baling of C&D debris. Unlike traditional balers, this technology shreds/pulverizes the C&D debris material, compacts it with light pressure, and rolls it into a hay bale—like form. The bales are typically 3-5 yd.³ in size and weigh between 1 and 5 tons (depending on the materials being baled). The material is then stretch wrapped for loading with a clamp onto flatbed trucks. With a cost of around $500,000 per baler, transfer station operators have been very cautious about this new technology. Nonetheless, this technology demonstrates the constantly evolving efforts to improve the efficiency of the managing C&D debris.

On-the-Job Grind

One alternative to disposing untreated wood and drywall in a landfill is grinding the material at the job site. After a small, portable grinder processes the material, it is placed in a layer on top of the ground before the sod is laid.

Questions have been raised about the potential dangers of Type-X drywall because it contains fiberglass. Studies currently are being performed in Georgia and Minnesota to test the environmental impacts that this method of disposal might have. A study performed in Indiana found this method to not have detrimental environmental impacts, and current state regulations permit contractors to grind up their untreated wood and gypsum drywall from construction projects and place the finished material on-site. This option will work in some areas but will not work in others. Grinding material on-site where soil, plants, and grasses do not benefit from gypsum is questionable.

The Silver Lining

As a result of concerns about groundwater contamination, there is mounting interest in requiring C&D debris landfills to be lined. Recent studies have found that C&D debris leachate might not pass primary and secondary drinking-water standards. States such as Florida and Minnesota are rapidly beginning to consider liner requirements to protect groundwater sources. To the extent that individual states pass legislation requiring liners for C&D debris landfills, the resulting increased cost of disposal would inevitably provide a boost to C&D recycling efforts. The disadvantage to requiring liners is that illegal dumping will increase.

What's Next?

As communities continue to feel the budget squeeze, more and more attention will be placed on wastestreams that represent the largest percentages of total generation. C&D debris recovery will likely become increasingly attractive to municipal program managers being pressured to reduce costs while maintaining recovery rates. Curbside and drop-off programs targeting traditional recyclables might be shunned in favor of programs targeting C&D debris. As a result of this increased interest in C&D debris, technologies and end uses that result in increased efficiencies and higher diversion will continue to be developed. Environmental concerns and increasing difficulty in siting new facilities and/or expanding existing facilities will drive up the cost of C&D debris disposal over time.

Chuck McLendon is director of operations for R.W. Beck Inc.'s Infrastructure Services Group in Orlando, FL. Timothy G. Townsend is an associate professor at the University of Florida in the Department of Environmental Engineering Sciences in Gainesville, FL. Kimberly M. Cochran is an environmental engineer at R.W. Beck's Infrastructure Services Group in Orlando, FL.

MSW - July/August 2002