CDRA Releases C&D Fines Reports to better understand fines characterization and manage material
The Construction & Demolition Recycling Association (CDRA) has made available to members detailed guidance documents on the small particle sized materials from recycling construction and demolition materials while providing other interested parties Executive Summaries of the papers on the organization's website.
One of the first steps of processing mixed C&D to recycle is to screen out the small particle size material from the incoming stream to the recycling plant, making the remaining materials more suitable for additional processing steps. These fine materials (referred to as recovered screened material in some locations) consist primarily of soil, but also includes small pieces of wood, concrete, drywall, rock, and other miscellaneous materials.
These documents were created by Timothy Townsend, Ph.D. (The University of Florida) and his team to provide insight into the C&D fine characterization and how to better manage this material. The first document addresses strategies that can be used by recyclers to create better products using their C&D fines and market them for appropriate beneficial reuse. It was based on examinations of C&D fines samples from across the country.
The samples were evaluated for particle size distribution, flammability, volatile solids (VS) content, asbestos content, total heavy metal concentrations, total PAH concentrations, PCB concentrations and total extractable petroleum hydrocarbon concentrations. The concern of trace chemicals in C&D fines has led some state regulatory agencies to require routine testing and compliance with risk-based regulatory thresholds. These thresholds account for background concentrations and vary geographically, resulting in states adopting different policies regarding beneficial reuse.
The results of the study support that some problematic trace chemicals are more heavily concentrated in the smaller fraction of C&D fines, suggesting additional processing can aid in reducing the concentrations of these chemicals.
Asphalt's effect on C&D fines
The second of the two C&D fines document provides a strong understanding of the types of asphalt products encountered in C&D, how they are typically managed (including recycling) and identify the environmental issues that affect recyclability and markets.
The objective of this research was to provide CDRA members with information on the PAHs they can expect in their asphalt-containing C&D fines and the bioaccessibility fraction of C&D fines. Typically, risk thresholds are calculated using a 100% bioaccessible fraction, meaning if 50% was used instead then the risk threshold would be higher for PAHs. The materials could be used in a wider range of beneficial use applications without exceeding risk thresholds calculated based on chemical bioavailability. The results of this study can aid recyclers seeking regulatory approval for C&D fines recycling as well as aid the industry in developing solutions to better produce, market, and distribute this commodity in a safe and economical fashion.
Members can log into the CDRA's members-only page to access the two white papers, which will also be updated in the coming months as Dr. Townsend's team completes further research.
The executive summaries are available to the public now on the CDRA website.
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