Researching Debris Regeneration

In December 1994, the Washington State Department of Community, Trade and Economic Development’s Clean Washington Center contracted with Gershman, Brickner & Bratton Inc., Falls Church, Va., to perform a market assessment of certain construction, demolition and landclearing commodities. The research assessments were performed to enhance expanded market penetration for recycled CDL content products and to stimulate and commercialize new and existing technologies and products using these recycled materials. The primary commodities reviewed included asphalt roofing shingle debris; gypsum wallboard; concrete pavement; asphalt pavement; and wood debris.

The study, titled "Construction, Demolition & Landclearing Debris Research & Assessment," revealed that those five commodities made up about 55 percent of the King County, Wash., CDL material stream. Broken down by the type of debris, and projected statewide – assuming that the figures are representative of statewide generation rates – estimates of the annual quantities of these five commodities being disposed are represented in Table 1 (see page 52). The remainder of this article presents highlights from the study.

Nationally, it is estimated that bituminous-type roofs are the most common in the United States, with bituminous material included in the built-up roofing membranes of more than 90 percent of the commercial/industrial roof systems in North America. With residential roofing, asphalt roofing is estimated to be 80 percent of the western U.S. market, with wood and other miscellaneous material accounting for the other 20 percent.

Data supplied by the Asphalt Roofing Manufacturers Association, Rockville, Md., for 1994 indicates that approximately 130 million asphalt shingle squares, or 13 million tons worth, are produced per year.

At the time of the study, there were no definitive tonnages available from any state landfills on the amount of roofing material actually being disposed. The NRCA Annual Market Survey estimated that the total 1994 roofing sales in the State of Washington were $392 million. This gross sales volume included $249 million of commercial roofing and $143 million of residential roofing. The commercial re-roofing value included an estimated $116 million worth of tear-off and replacement work.

Using all data sources, GBB provided an opinion that 175,000 to 200,000 tons of asphalt shingle roofing debris is currently generated in the state of Washington. Presently, a small amount of asphalt roofing material is being recycled or reused in the state. Therefore, GBB concluded that at least 125,000 to 140,000 tons per year of asphalt roofing material could potentially be recovered.

Typical end markets for asphalt shingle roofing debris include use as an energy source, as additives in cold mix compounds and hot mix asphalt, and in paving mixtures and new roofing materials. The use of asphalt roofing shingles in asphalt pavement provides the greatest potential for a significant market outlet in the state.

Primary market barriers include asbestos concerns, regulatory use approval, project capitalization, and that asphalt roofing shingles as a recyclable commodity are not currently acknowledged in the count toward the state’s recycling goals.

Gypsum wallboard debris is initially created as a defective board at the manufacturing plant or at retail outlets. The sizing of the board to meet new construction needs will lead to end cuts of sheet and often scrap pieces.

The actual quantity of gypsum wallboard material being disposed in the state of Washington on an annual basis is not known with any degree of accuracy. Industry estimates have been made that the total generated debris rates are about 10 percent of total production.

It appears that 250 to 300 million square feet per year of gypsum wallboard may be currently produced in the state. Besides two in-state manufacturers, at least three or four other national suppliers ship into Washington. Using an approximate gypsum wallboard total weight of one ton per 1,000 square feet produced, this would indicate that 250,000 to 300,000 tons of raw product are manufactured in the state. If the scrap factor, plus manufacturing debris, totalled 15 percent, this data would conclude that 37,500 to 45,000 tons of new wallboard debris is potentially available.

However, after considering waste composition studies, manufacturers’ supplied data, and recycler-provided data, it was GBB’s opinion that the quantity of waste gypsum wallboard available in the state may range from 70,000 to 80,000 tons per year, including manufacturers’ residuals and pre-demolition/renovation strip-outs.

Currently, five uses of gypsum wallboard debris are known to be ongoing in Washington, including recovery and processing into new wallboard, use in animal bedding and land application, use in fertilizers, use in agriculture and use in compost.

Based on all data compiled on this subject, which included the actual operation of a major recycler in the area, New West Gypsum, GBB estimates that at least 20,000 to 25,000 tons per year of additional material are potentially available for additional recovery in the state.

Primary market barriers include product quality perceptions, economic issues and product quality control.

In concrete pavement recycling, the existing concrete pavement is broken into smaller, more manageable pieces and transported to a crusher where it is further processed to produce aggregate of specified sizes. These aggregate materials, referred to as recycled concrete aggregate, are then stockpiled for later use.

Old concrete can come from a variety of projects, including highway or runway reconstruction, demolition of structures having concrete in their base, slab replacement, curbs and sidewalks, and so forth.

Phone contact was made with more than 20 companies to solicit information pertaining to their annual concrete processing and recycling amounts. Eight of these companies were willing to provide annual processing figures. These annual figures totaled an estimated 1.4 to 1.5 million tons of concrete debris crushed and sold for reuse.

In 1992, the statewide demand for concrete aggregates, including sand concrete, was more than 10 million tons, and fill material demand was in excess of 7 million tons.

RCA is widely accepted for use as base and fill material. It is estimated that from 75,000 to 100,000 tons per year is discarded in state-permitted disposal facilities. This amount represents less than 0.5 percent of the estimated 29 million tons of various aggregates produced annually in Washington.

According to U.S. Bureau of Mines data, concrete and base aggregates sold or used in Washington in 1992 totaled 21.4 million tons, or almost 60 percent of all aggregate activity. The presence of significant aggregate and cement production illustrates the potential of a significant RCA market.

Pavement and paving material applications probably offer the potential for the largest immediate market for crushed concrete materials because of their tremendous demand for aggregate products.

Asphalt pavement debris is produced primarily as a result of preparing existing paved areas for repaving. The use of reclaimed asphalt pavement is fairly well established within the paving industry. RAP material can be directly recycled back into pavement or through grinding, be stockpiled and reused as asphalt pavement feedstock or as an aggregate material.

A total of 775,777 tons of demolition debris and inert materials were landfilled in the state of Washington in 1993 at inert/demolition landfills. Of this material, 643,258 tons were reported to be inert materials.

Considering the King County waste sort findings at the CDL transfer station in 1994, asphalt pavement contributed an estimated 0.3 percent of the demolition debris disposal activity. However, applying 0.3 percent to the approximate 132,519 tons of CDL-based demolition debris disposed at demolition/inert landfills only resulted in an about 400 tons per year. This low disposal rate is most likely caused by the high King County CDL transfer station disposal fees versus the costs at the local recycling plants available to contractors.

No estimates are known to exist from state-generated data on the percentage of asphalt pavement in the inert debris stream. However, based on a recent GBB CDL-related study completed for a county in North Carolina, it was found that mixed land clearing and inert debris landfills receive approximately 10 percent asphalt pavement debris. It is to be expected that the Washington rates would also be very low in view of the high RAP utilization in the asphalt paving market. Considering a 10 percent basis, about 60,000 to 70,000 tons per year of asphalt may potentially be mixed in with the total inert material going to inert debris/demolition debris landfills in the state.

If the availability of old asphalt pavement coincided with the demand for RAP at a substitution level of 15 percent, 1 million tons could be reused on an annual basis. If RAP were used at a 15 percent substitution rate and Washington State Department of Transportation projects were eliminated, 630,000 tons per year could still be consumed.

WSDOT specifications allow the contractor to use up to 20 percent RAP as long as the material meets the specifications for the class of asphalt concrete specified. Potential may exist for expanded use of RAP in asphalt and concrete pavement construction and rehabilitation, embankment fill material, or other associated uses. Gaining acceptance and thereby creating demand for additional consumption is key.

There was an estimated 7 million tons of asphalt pavement placed in the state in 1994. It is reported that a majority of this material contained RAP. The analysis of asphalt pavement in the CDL stream provides an estimate that 60,000 to 70,000 tons per year of asphalt pavement may be disposed in state-permitted landfills.

The main generators of wood debris are in the manufacturing sector and include softwood lumber mills, hardwood lumber mills and wood product manufacturers, such as furniture makers, box makers and pallet builders and recyclers. Other sources are land clearing for new homes and the demolition or dismantling of old homes and old manufacturing structures. Wood debris also comes from residential and commercial construction.

Landfill operators generally keep sketchy records on wood debris, as it is often mixed with other debris. However, it is clear that less wood debris is landfiilled than in the past. From 20 companies studied, more than 638,000 tons of wood debris from CDL was reported recycled in 1994. The amount is expected to increase dramatically during the next five years, jumping to more than 1 million tons per year by the year 2000.

As the development of this industry matures, the specifications for the wood debris has an opportunity to also mature. If the volumes of wood debris reach a level of such magnitude that allows the pulp and paper processor to tighten their specifications, this would allow a greater amount of wood fiber to become available to the next level of wood debris utilization to develop.

Using 1993 reported MSW data and compiling 1994/1995 interview data on CDL materials, GBB concludes that in the state of Washington, more than 5.8 million tons per year of MSW are estimated to be generated, exclusive of CDL debris. Of this 5.8 million tons per year of MSW, 3.4 million tons per year is estimated to be disposed and 2.4 million tons per year recycled. Additionally, more than 4 million tons per year of CDL debris are estimated to be generated, with approximately 2.7 million tons per year recycled.

Based upon the MSW and CDL streams, it was estimated that the quantity of CDL debris in the state is almost 70 percent of the MSW stream (exclusive of CDL). When considering both streams together, CDL debris was estimated to be more than 40 percent of the total solid waste stream.