C&D on my Mind
A waste-characterization study in Georgia sheds light on the market potential for construction-and-demolition debris.
Monday, February 28, 2011
By Abby Goldsmith, Roy Edwards
At the same time that solid waste professionals focus on nontraditional materials to increase diversion of solid waste, many communities across the country are looking for ways to further reduce the environmental impact of the infrastructure in which we live and work. To evaluate options to accomplish both these goals, Georgia’s Department of Natural Resources Sustainability Division retained R. W. Beck, an SAIC company, with its subconsultants, Cascadia Consulting Group Inc. and Innovative Waste Consulting Services LLC, to conduct a comprehensive study characterizing construction-and-demolition debris (C&D) disposed across the state and the challenges and opportunities to reduce and recover the recyclable materials composing this wastestream.
The project team characterized nearly 800 loads of C&D material at 10 landfills across Georgia in March and September 2009. The results were used to calculate the amount and type of materials statewide, by region, and by activity type (e.g., new construction, renovation, demolition, roofing, and other). In addition, because concerns about the presence of lead-based paint and asbestos-containing material in C&D have been cited as a deterrent to diversion, C&D loads were also sampled to determine the extent of the presence of these materials.
The team conducted further research to identify issues, challenges, and opportunities to diverting C&D in general and each of the key materials observed in the characterization study. This included market research for each key material, case studies of successful diversion policies and programs, and interviews with generators, collectors, processors, and end users.
Estimated Tonnage of C&D
From October 1, 2008, through September 30, 2009, an estimated 3 million tons of C&D was disposed in landfills in Georgia: 2,024,277 tons in C&D landfills and 927,846 tons in municipal solid waste (MSW) landfills. C&D, defined by the Georgia General Assembly as “waste building materials and rubble resulting from construction, remodeling, repair, and demolition operations on pavements, houses, commercial buildings, and other structures,” represented an estimated 21.2% of all solid waste disposed in the state during these 12 months.
It is important to note that this study was conducted during an economic downturn with the lowest housing starts seen in well over a decade. As a result, according to state landfill reports, the tons of C&D disposed was estimated to be 23.6% lower in FY2008 than in FY2007 while the amount of MSW disposed remained nearly constant. Thus, C&D is likely to constitute a higher percentage of the solid waste disposed in the state in years prior to and, potentially, following the economic downturn.
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[1] The R.W. Beck Project Team converted observed cubic yards to tons for each material based on conversion
factors included in the following documents: "Measuring Recycling: A Guide for State and Local Governments,"
document no. EPA530-R-97-011 (September 1997); “Targeted Statewide Waste Characterization Study: Detailed
Characterization of Construction and Demolition Waste” (2006); “Converting C&D Debris from Volume to Weight:
A Fact Sheet for C&D Debris Facility Operators” (2000);
[2] The R.W. Beck Project Team calculated the upper and lower boundary at a 90% confidence interval. |
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FIGURE 2
Top Ten Material Types (by weight) in C&D Disposed in Georgia,October 2008 – September 2009 Characterization by Activity Type |
Material Types in C&D
The project team characterized 786 loads to estimate the composition of C&D disposed in Georgia. Figure 1 illustrates the composition broken into 12 material classes. Within these classes, 10 individual material types comprised over three-quarters of all C&D disposed, as shown in Figure 2. Composition roofing, unpainted concrete, dirt and sand, and unpainted brick and other aggregates were the most commonly identified material categories in the C&D characterized, totaling an estimated 1.5 million tons per year disposed in Georgia landfills.
During the study, the driver delivering each load to the landfill identified the activity type (new construction, renovation, or demolition) from which the load originated and the type of building (residential or nonresidential) through an onsite survey process. Figure 3 shows that when the findings from the field survey were extrapolated to all C&D disposed in the state over the course of a year, more C&D was disposed from nonresidential new construction activities than from any other individual activity type, with roofing activities generating the second highest amount of C&D being disposed.
Identifying the activity type from which the C&D was generated allowed the project team to characterize the type of materials in a load by the activity type from which it came. For example, more clean dimensional lumber was found in residential than in nonresidential loads, with loads from residential demolition sites likely to produce the most clean dimensional lumber. On the other hand, nonresidential construction generated the greatest amount of unpainted aggregate (including unpainted concrete, unpainted asphalt, and unpainted brick and other aggregates). This type of information allows those processors or end users interested in a particular material type to target their efforts to divert feedstock from a particular type of construction activity.
Lead-Based Paint win C&D
As part of this study, the R.W. Beck project team sampled C&D loads to determine the incidence of lead-based paint at five of the 10 sites in March 2009 and the remaining five sites in September 2009. Painted surfaces arriving in loads from all activity types except new construction sites (in which the team assumed that no lead-based paint was used) were sampled using a handheld X-ray fluorescence (XRF) device.
Figure 4 shows that, out of a total 487 painted or treated surfaces sampled, 70 had a lead concentration reading of equal to or greater than 1 milligram per cubic centimeter. These 70 surfaces were on material weighing an estimated total of 18 tons, approximately 1% of the total tons received during the lead-based paint sampling period.
Nearly all of the material that contained painted or treated surfaces that tested positive for lead concentration of equal to or greater than 1 milligram per cubic centimeter came from residential buildings according to the drivers delivering the loads. Twelve tons, or 66.7%, were from residential demolition sites and 22.2% were from residential renovation sites. An estimated 11.1% were from nonresidential renovation sites and 2.8% were from mixed/other activity types. Sixty-one percent of the tonnage with sampled surfaces testing positive for lead concentration that was equal to or greater than 1 milligram per cubic centimeter was painted or stained wood, 20% was painted concrete, 14% was painted remainder/composite C&D, and 7% was painted/demolition gypsum.
Asbestos-Containing Material
The R.W. Beck project team also sampled loads (excluding those from new construction) to determine the incidence of asbestos-containing material (ACM). When a material type that could potentially contain asbestos was observed, a sample was taken, bagged, and sent to a certified laboratory for analysis. This excluded loads of asbestos that came in presorted and separately bagged.
The project team collected 307 samples from 182 loads, as shown in Figure 5. Fifteen of these samples contained a detectable amount of asbestos, four of them with an asbestos content greater than 1% (National Emission Standards for Hazardous Air Pollutants threshold for defining a material as ACM). An estimated 2.6 tons of material sampled (.15% of the total C&D tonnage received at facilities) exhibited an asbestos concentration that was detected by the laboratory, and 739 pounds (.02% of the total) exhibited an asbestos concentration greater than 1%.
Overall, loads from residential demolition contributed the greatest amount by weight of material that tested positive for asbestos, followed by loads from residential renovation. The weight of material from roofing and nonresidential demolition had a relatively small amount of material with positive detections of ACM. The material category with the most frequent detection of asbestos was wallboard and joint compound, however one sample of transite siding exhibited the highest single asbestos concentration (20%) of all materials sampled. By weight, the painted/demolition gypsum material type contributed most to the asbestos detections encountered, in terms of frequency and weight alike.
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Challenges and Opportunities
The R.W. Beck project team interviewed generators, processors, and end users of some of the most prevalent C&D materials disposed in Georgia to assess the challenges and opportunities associated with recovery of these materials. One of the key challenges to diverting recyclable materials in Georgia, including all types of C&D, is that of low tipping fees at landfills. The average tipping fee at C&D landfills in the state is $23.72 per ton according to the Georgia Department of Community Affair’s 2009 Solid Waste Annual Report. Other challenges, especially at demolition and renovation sites where all materials are commonly generated at the same time, include limited space at the work site for source separation, processing, and storage and the difficulty of training workers and allotting the time to source-separate material adequately.
At the top of the list of opportunities to increase recovery of C&D is the growing interest of many owners, builders, and contractors in meeting green building standards, such as the US Green Building Council’s Leadership in Energy and Environmental Design (LEED). Many of these standards give points for recycling C&D generated at construction sites and for using construction materials made from recovered C&D. Another opportunity the project team identified was the ease of diverting relatively source-separated materials that are generated at many new construction sites. New construction activities are often phased and thus generate more homogenous material loads than demolition and renovation activities. A final underutilized opportunity, according to some stakeholders, was the low-cost option of using some materials onsite, thus avoiding transportation and offsite processing costs. Such materials included C&D aggregate and C&D wood, found in large amounts in the Georgia debris.
Markets for Recovery and Recycling
Based on the research performed for this study, there appear to be established markets for painted and unpainted concrete, dirt and sand, painted and unpainted brick and other aggregates, clean dimensional lumber, and other ferrous materials generated in Georgia. However, even for these materials, the feasibility of accessing the markets depends on the source and quantity of material generated, the degree of onsite sorting, the specifications of the local market, the distance to markets, and the distance to disposal facilities. Primarily due to the increasing interest in biomass-to-energy, processors and end users expressed a growing but still limited demand for other types of wood in C&D, most notably clean engineered wood and painted/stained wood. Limited markets were identified for the three remaining material types in the top 10: composition roofing, clean gypsum board, and remainder/composite C&D.
Conclusion
Armed with the information from this C&D characterization study, the Georgia Department of Natural Resources Sustainability Division is considering strategies to further reduce the C&D disposed in the state. Strategies under consideration fall into five key areas: policy, education and technical assistance, infrastructure development, market development, and potential partnerships.
Author's Bio: Abby Goldsmith is a senior director for the solid waste practice of R.W. Beck, an SAIC company. |
Author's Bio: Roy Edwards is a Sustainable Systems Engineer for the Sustainability Division of the Georgia Department of Natural Resources. |
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