(63e) Material Properties of Recycled Glass Sand: A Case Study Conducted with Glass Half Full Nola

The US recycles less glass than other countries due mainly to government policies, lower consumer engagement, and cost. Successful glass recycling facilities are often co-located with bottle manufacturers that recycle old glass into new. However, many communities, particularly those in rural areas and along the coast, lack this infrastructure. Furthermore, recycled glass sand has many potential benefits over natural sand for many applications; for example, it can be made coarser, does not compact as much, and is more resistant to erosion, making it an excellent – and underutilized – material for coastal protection and restoration.

Guided by the potential application of recycled glass sand for environmental restoration projects, this research utilized a combination of techniques to characterize the properties of crushed glass produced by the New Orleans start-up company, Glass Half Full. These techniques included x-ray fluorescence (elemental composition), toxicity characteristic leaching procedure (TCLP, detection of leachable elements), thermogravimetric analysis (detection of organic contaminants, e.g., labels and adhesives), and optical microscopy (images analyzed for particle angularity). Key findings were as follows: (1) recycled glass sand is mostly silica, like natural sand in the Mississippi River Delta; (2) Parts-per-million amounts of heavy elements used in glass processing were detected, but levels were either comparable to or less than levels found in native soil (for example, barium and copper) or well below regulatory levels set by the Environmental Protection Agency (lead < 100 ppm for growing root vegetables, <400 ppm for children’s playgrounds). Furthermore, no leaching of these elements from the glass sand was detected during TCLP analysis, a standard procedure used to evaluate soil-to-groundwater transport of contaminants in the environment. (3) Paper labels are mostly sifted out during Glass Half Full’s processing and are retained with the “gravel” size; “invisible” residues and glues were usually undetectable in sand and made up < 1% of the material when detected. (4) While recycled glass sand is not sharp to the touch, individual grains are more sub-rounded than well-rounded than natural sand because it has not been weathered in the environment. These findings were consistent with Glass Half Full’s reported collection of mainly food and beverage containers, which are typically soda-lime glass.

*Funding: NSF 2137730, 2230769