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Recycle Construction and Demolition (C&D) Debris
Construction Waste Handbook
Worksheet Economics
C&D Resources
Education Program
Wood
Wood waste by almost all account constitutes 40-50% of the volume of the residential new construction waste stream. The most common reuse option for C&D wood is as fuel in industrial boilers or co-generation plants. Most wood used for fuel is chipped prior to transport, although wood that has been treated with such preservatives as copper chromated arsenate (CCA), creosote, or chlorophenol should be removed before the wood is chipped (FDEP, 2001:26). In the case of CCA-treated wood, if it is recycled as fuel, the ash is likely to contain large amounts of heavy metals. Those metals probably are arsenic and chromium. Most likely the metals are present in high enough concentration to render the ash as "hazardous" and require its disposal under the hazardous waste guidelines under the Resource Conservation and Recovery Act (RCRA). Therefore, efforts should focus on the reuse of chemically treated wood. Another alternative is to use the wood as a material in cement. In general, disposal-end practices should include improved sorting of preservative-treated wood at C&D recycling facilities and the institution of proper disposal practices (Solo-Gabriele et. al, 1998).
Wood can also be reduced in volume and down-cycled to make wood products of a lower economic value such as plywood, oriented strand board, and wood I-beams. Conversely, the adhesive content of these engineered wood products materials can limit the eligibility for future recycling. The economics of using wood chip waste for engineered wood products depends upon local wood waste markets (Toolbase, 2004:3).
Building materials such as lumber can frequently be reused in their original form. Clean C&D wood can also be laminated with plastic to make a decking material, although this makes the wood almost impossible to recycle later (Turley, 2002). Wood chips can also be used in compost and animal bedding. Natural woody debris can be ground up and used as horticultural mulch (FDEP, 2001:2).
The diversity of the wood marketplace is such that a reasonably mature underground economy exists wherein the amount of wood waste that ends up in the landfill is considerably lower than it might be otherwise expected. In part, this economy is fueled by municipalities who have created a marketplace by going into the mulch business as an attempt to mitigate the rapid loss in landfill capacity by creating a product from the waste. This "waste equals food" business decision allows many of the contractors to contract with builders for one economic rate per cubic yard based upon tipping fees and to then dispose of the material at a mulching operation at a significantly reduced rate and generating a profit margin in between. For some of the larger operators in the H-GAC area this is how they feed their families.
In summary, wood waste can be used in the following applications:
- An industrial fuel source;
- Mulch;
- Composting operations;
- Animal bedding;
- Landfill cover; and
- Some building products.
Cardboard typically represents 11-30% of the C&D waste stream by volume. Corrugated cardboard is the most common building packaging material and is therefore a key component of the C&D waste stream due to the fact that many building materials are shipped to the site in a pre-fabricated, finished state.
Cardboard is one of the most readily recycled materials in the C&D waste stream as long as it is not wet. The cardboard recycling market is well developed, and it can be to the benefit of builders to recycle the cardboard because it otherwise takes up considerable space in waste containers. Cardboard is typically processed and recycled into new cardboard containers (FDEP, 2001:27).
Gypsum drywall
Gypsum drywall comprises by volume between 8% and 15% of jobsite waste (FDEP, 2001:1). 31.5 billion square feet of gypsum drywall was produced by US manufacturers in 2003. Many landfills are prohibiting gypsum drywall from entering their landfill. Clean gypsum board1 can be ground up and used in the following applications (Toolbase, 2004:3):
- Applied as a soil amendment;
- Used as a raw ingredient in the manufacture of Portland cement;
- Used for animal bedding;
- Used as a bulking agent in composting; and
- Recycled into new drywall (FDEP, 2001:28).
Asphalt shingles
Asphalt shingles are nearly 60% of the shingle market in the United States. In the H-GAC area, that percentage would have to be higher due to the ubiquitous nature of our building style and penchant for uniformity in our master planned communities behind our gates. Shingles comprise approximately 6% of the C&D waste stream by volume (FDEP, 2001:1). Asphalt shingles can be recycled into new shingles, crushed and used as an aggregate in the manufacture of hot mix asphalt, or as a primary material for rural roads (FDEP, 2001). Asphalt shingles also can be successfully ground on-site and utilized as base material for concrete flatwork such as driveways and sidewalks.
Bricks
Bricks represent a material in the H-GAC region that is widely deployed and which is highly desirable in the diverted waste stream. The marketplace for bricks is strong because it is composed of two elements. The first is the aggregate business which utilizes bricks as a source of crushed material to create fill and/or base of high quality. The second market in our area is the resale of bricks as an architectural element. The huge number of homes that are built in the H-GAC area each year fuels an underground economy that feeds upon these materials to do small jobs throughout the area. Nationally, this is less of an issue as the residential construction market is not as focused as we are in the H-GAC area on a brick veneer façade.
Concrete
Concrete is one of the most recycled materials in the United States and the world. The primary market for recycled concrete is as a base product for buildings and roads. Crushed concrete and brick can also be used as the primary surface material on rural roads and driveways, in drainage applications, and as borrow pit fill (FDEP, 2001).
Local markets for recycled concrete depend on the presence of local construction and road building markets (Turley, 2002). Markets for recycled concrete also depend on the local availability of such substitutes as lime rock (FDEP, 2001:24).
Metal
Metal is present in small amounts in residential C&D projects. What metal there is comes in the form of wiring, siding, fasteners, and roof flashing. Rarely is high value metal landfilled. There is an effective market based system wherein copper and aluminum are routinely recycled by the tradesperson(s) performing the work or other tradespersons on the jobsite. This is entirely consistent with the underground marketplace for untreated wood products mentioned earlier. When low value metal is present in sufficient amounts, it can be readily recycled in the scrap metal market.
Screened materials
Other recovered materials typically consist of material left over from screening mixed C&D at a processing facility. The screened material typically consists of mostly dirt but can also contain small fragments of wood, rock, paper, drywall, and plastic. One use for this material is for construction fill (instead of soil) for roads, buildings and landfill construction projects. Another use for screened material is as daily cover for landfills. When large amounts of gypsum are present, however, the hydrogen sulfide content of the landfill gas can increase, creating an odor nuisance for neighborhoods located close to the landfill (FDEP, 2001:29).
Miscellaneous
Habitat for Humanity has a number of RE-store locations across the country, including several in the H-GAC area. The RE-store stores serve as both non-profit building materials recycling centers and discount home improvement centers, providing local markets for used C&D materials and salvaged parts. There is also a southern Montgomery County RE-Store in Conroe. A variety of materials can be purchased or donated at the store (RE-Store, 2004).
Additionally there are a number of private sector second hand and/or architectural building supplies stores that can and do frequently take materials from the C&D cycle and provide a method of redeployment. The H-GAC area also has Historic Houston, a not-for-profit who does the ultimate recycling by accepting a limited number annually of whole houses for redeployment.
1 - Clean gypsum board is free of wood, metal, and plastic, is not asphalt impregnated, and is not coated with glass fiber, vinyl, decorative paper, or any other finish (Design Coalition, 2004).
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