Materials Characterization

Recycled glass sand is mostly silica, like the natural sediment found in the Mississippi River Delta and most beaches along the Gulf Coast. The main difference is that calcium and sodium oxides are added to the silica during glass processing; however, these compounds are found in natural minerals and so they are not a concern for the environment.

Is “recycled glass sand” really “sand”?

To the touch, it feels just like regular sand. However, in our research we took a closer look at individual grains of sand and found that the angularity, or sharpness, depends on how the glass in crushed. In an analysis of thousands of sand particles from Glass Half Full’s current process, we found that less than 1% of sand grains are sub-angular and none are angular or very angular – overall quite similar to natural sediment dredged from the Mississippi River has been used historically for coastal restoration.

Is recycled glass

sand sharp?

We found trace amounts (parts-per-million) of elements used in glass making, but levels were either comparable to or less than levels found in our native soil or well below regulatory levels. For example, lead levels were ~50 ppm, well below the 100 ppm limit for growing root vegetables in soil and the 400 ppm limit for children’s playgrounds. Furthermore, no potentially hazardous elements leached out of the sand during standardized testing that simulates soil-to-groundwater transmission (TCLP: toxicity characteristic leaching procedure, see the report from Waypoint Analytical here). In terms of labels, the glass pulverizing process removes nearly all non-glass contaminants from the glass sand product we use for restoration.

Are there contaminants in the glass, like from colorants or labels?