C&D/wood debris management trends by Peter Yost P romising C&D debris recovery results are beginning in the residential sector As the field of construction and demolition debris management develops, new information has become available on the amount of C&D debris in the U.S., the diversion potential and cost of various waste management solutions, and markets for recovered C&D materials. The NAHB Research Center (NAHB-RC, Upper Marlboro, Maryland) undertook a three-year project to develop, demonstrate and disseminate innovative residential construction waste management. One phase of NAHB-RC s efforts developed specific pilot projects and used the results to estimate the quantity of waste reduction, reuse and/or recycling at job sites. In addition, NAHB-RC provided data for the U.S. Environmental Protection Agency s recently released Characterization of Building-Related Construction and Demolition Debris in the United States. The document provides an estimate of the amount of C&D debris generated yearly, as well as its sources and destinations. Characterization of waste In 1996, residential construction, renovation and demolition debris made up 43 percent (58.2 million tons) of the 136 million tons of building-related C&D debris generated per year, according to EPA (see Figure I ). Of this residential total, 11 percent, or 6.6 million tons per year, is generated by new construction. Location Building type/production level Diversion rate (%) Cost impact (1) Maryland Detached homes: 1 start/month 21 9% decrease Detached homes: 2 isolated starts 22 2% decrease Condominiums: portions of three 8-unit buildings 2 1 3% decrease Condominiums: one 36-unit building 38 9% decrease Michigan Detached homes: 1-2 starts/month 48 9% increase to 20% decrease Detached home: 1 isolated start 38 8% increase to 2% decrease Detached homes: 4 starts/month 45 21% decrease Detached homes and condominiums: 2 starts/month 7 1% decrease Florida 187 single-family, affordable homes; 60 starts/year 75 50% decrease (1) Increase or decrease in the total cost of disposal as compared to the projected cost of conventional disposal methods. Source: NAHB Research Center, 1996. EPA estimates that 20 to 30 percent of all 1,000 asphalt and concrete crushing facili- C&D debris was recovered in 1996. Unre- ties, 500 scrap wood processing plants and covered debris goes into either one of 1,900 300 mixed-waste C&D facilities. Now, the active C&D landfills (35 to 45 percent of total number of C&D debris recycling facilities C&D debris) or MSW landfills, combustion has nearly doubled, to approximately 3,500. or unpermitted disposal (30 to 40 percent). Alternatives to disposal are growing. In Job-site recycling 1996, an estimated 1,800 C&D recycling fa- In an effort to maximize the amount of concilities were operating, including more than struction waste diverted from disposal and to Peter Yost is the director of resource and environmental analysis for the National Association of Home Builders Research Center (Upper Marlboro, Maryland). He can be reached at (301) 249-4400, ext. 542.
document the resulting economic impact, NAHB-RC developed three residential pilot project sites in Florida, Maryland and Michigan. In Maryland and Michigan, the primary areas of concern for this pilot, the diversion rate averaged 30 percent. below the pilot s 50 percent diversion goal. Overall. the pilot projects resulted in a cost savings of under 10 percent (see Table I). The pilot found that the significant variance in diversion rates and cost savings was influenced by several conditions. Builder interest in recycling is motivated primarily by cost and convenience. and thus, innovative waste management techniques must consider at least one of these issues. As expected. the cost of landfilling and transportation plays a large role in the economic incentive to recover these materials. EPA reports that average C&D debris landfill costs per ton range geographically from $19.70 in the Midwest. where the population density is low, to $46 and $42.60 per ton in the Northeast and West. respectively. Another major factor is markets for the materials (see next section). Also. the availability of hauling and recovery options affect cost. A builder has multiple options when it comes to waste recovery, each varying in price and level of involvement by the builder. Clean-up services are relatively new and not yet widely available. With such services, builders commitment can be low, because they are responsible only for getting unsorted waste to the designated spot (in front of the work site or to the curb). Commingled recovery, job-site separation and self-haul are three other recovery options. In exit questionnaires done by NAHB-RC, several builders cited the small cost savings as an impediment to job-site recycling. Despite this limitation. all but one of the participating builders plan to continue recycling in some form on selected jobs. Builders said the pilot projects gave them useful information for the application of recycling efforts to appropriate sites. The more highly successful recovery efforts implement a recovery plan in the initial planning stages. It is at this early stage that the general contractor s commitment to the waste management plan must be conveyed to subcontractors. The pilots illustrated that smaller builders can implement a successful recovery plan faster than large production builders. Onsite signs are important for
increased diversion and can be a good marketing effort for the builder. Markets for recovered materials The Maryland and Michigan pilot projects lacked markets for selected recovered materials. In Maryland. insufficient markets existed for wood, and in Michigan. markets were needed for drywall. This had a significant effect on the diversion rates of these two projects given that wood, drywall and cardboard make up 60 to 80 percent (by weight or volume, see Table 2) of the waste stream for most home builders. While each of these materials is technically recyclable, only cardboard has well developed markets, widespread channels of distribution and a relatively high market value. Currently, the primary C&D materials recovered are corrugated boxes, wood, concrete, asphalt and metals. Materials such as gypsum wallboard, asphalt shingles, carpet and carpet padding are being recovered more often, but still have their drawbacks. The three major barriers to the recycling of these materials are: the cost of collecting, sorting and processing these materials the low value of recycled-content materi al compared to virgin low-cost landfilling options. Wood waste recycling. Processed (chipped) wood can be used in mulch. as composting bulking agent and in animal bedding. In addition, recovered wood makes good fuel source because of its low moisture content. Since it is generally cleaner, wood from construction is more widely accepted than demolition wood. Asphalt and concrete. The primary use for these materials is as a replacement for road-base gravel. However, they also can be fed back into pavement as reclaimed asphalt pavement or as a base or subbase in asphalt or concrete. Concrete recycling is practiced in nearly all parts of the country. Metals recycling. The recycling rate for metals is the highest of all C&D debris. at 85 percent. However, the small quantities of metals generated at residential construction sites can make effective recovery difficult even with available markets and a relatively high material value. Drywall. By stripping the paper backing and remixing the gypsum, drywall can be recycled into a new product. Gypsum from clean drywall also has been shown to be a beneficial soil amendment. showing effects nearly identical to those of agricultural-grade gypsum. Agricultural use of gypsum increases soil tilth and permeability in soil with high clay content. Gypsum also can be used in compost, animal bedding and cat litter. In compost, it also has been shown to reduce ammonia odors and loss of available nitrogen, Additional information about these and other drywall uses is available (see sidebar). Asphalt shingles. Asphalt shingles have great recycling potential because they are plentiful in the C&D debris stream: they are generated separately, and thus. are easy to isolate; and recycling technology and markets exist. The primary application for shin-
gles is paving. This falls into two categories -paving applications that must meet state department of transportation specifications, and those that need not. In many DOTapproved applications, post-consumer shingles are not allowed since they may be composed of varying asphalt and aggregate materials, be from multiple manufacturers, contain asbestos or have been exposed to ultraviolet sunlight. The UV breakdown of the asphaltic component of shingles makes them less attractive for recycling due to hardening and increased brittleness. However, postconsumer shingles are used in other paving applications such as driveways, parking lots and aggregate base and other sub-base pavement layers. Asbestos-content roofing materials, manufactured from 1963 to 1977. are subject to laboratory testing. These were produced in low concentrations by three of the largest shingle manufacturers at certain plants. Carpet/padding. Carpet is either recycled into new carpet or cleaned, retexturized and reused. Many companies are beginning to offer take-back programs either for charge or as a no-charge customer service policy. In 1997, over five million tons of carpet were collected in recycling projects. As the price of nylon fiber increases, more carpet manufacturers are beginning to use less expensive polyester fibers or blends creating a larg- The NAHB Research Center has a number of resources on residential C&D/wood waste debris management. The Research Center s A Builder's Field Guide provides information on cost effective and voluntary construction waste management. Remodeler s Field Guide will soon be available. The Research Center also has a number of helpful brochures and pamphlets, as well as a hotline at (800) 898-2842. The NAHB Research Center can be reached at 400 Pringle George s Blvd., Upper Marlboro, MD 20774; (30 1) 2494400; www.nahbrc. com (Web). A copy of the U.S. Environmental Protection Agency s Characterization of Building-Related Construction and Demolition Debris in the United States (report no. EPA530-R-98-010), can be ordered from er market for competitive recycled-content carpets. Residential carpet typically is installed over carpet padding, which is generally made of polyurethane. Approximately 125,000 tons of pre- and post-consumer polyurethane foam pad are recycled each year into rebond foam pad. a shredded and reformed product. Oththe RCRA/Superfund Hotline, (800) 424-9346. As research continues on uses for recovered gypsum, here are a few resources for further investigation. Acornprehensive look at gypsum drywall recycling is covered in an annotated bibliography by John Reindl, recycling manager in Dane County, Wisconsin (e-mail: reindl@co.dane.wi.us). For more information on the success of gypsum use as a soil amendment, see A Builder s Field Guide published by the NAHB Research center. Also, the Clean Washington Center (Seattle) found gypsum wallboard scrap and wastepaper to be successful as a bulking agent in compost. This report can be seen on the Center s Web site at www.cwc.org. er types of padding are not recycled because of their smaller volume, lower value, and/or unrecyclability. Reuse markets grow Recycling, while offering a major outlet for recovered residential C&D debris, is not the only option. Reuse organizations are devel-
oping and expanding to address C&D materials. Reuse centers accept and then resell used, salvaged materials and mis-ordered or slightly damaged new materials from building material retailers and manufacturers, remodelers and new home builders. In some cases, the recovered materials are processed to upgrade the items for added value and re-use potential. Wood waste reduction through efficient design When a contractor begins a construction project with an initial commitment to waste management, he/she can efficiently use framing material through value-engineered design, estimation and construction practices. This can lead not only to reduced construction costs, but also to decreased disposal costs by keeping excess cutoffs to a minimum. Because wood is the largest component of new residential construction waste, efficiency in the structural framing of the home the focus of another NAHB Research Center pilot program. Two case studies worked at the design and estimating levels, while the third documented efficient material usage at the job site. At the design and estimating levels, approximately 78 percent of the savings from the in-line framing technique resulted from reduced floor framing costs. In the job-site case study, NAHB-RC research center documented a builder s use of efficient framing techniques and compared the results to conventionally framed houses. In the pilot, the cost of framing material was reduced by about $1.50 per square foot. The wood-waste generation rate was reduced by about 65 percent, representing a savings of approximately $100 in disposal costs. RR