CULLET SUPPLY ISSUES AND TECHNOLOGIES

This chapter describes the cullet supply issues and technologies. Post-consumer glass, or cullet, is fully recyclable, but inefficiencies in each step of the chain of custody decrease the fraction of glass returned to glass manufacturers. In the recycling process, cullet passes from consumers to waste haulers, then to material recovery facilities (MRFs), next to glass recyclers, and finally back to glass companies. Different economic and social drivers impact the fraction of glass recovered in each link in the chain of custody. In recent years, the fraction of glass recycled in the United States has been stagnant. Higher cullet recycling rates will require decreasing the amount of glass sent to landfills, improving cullet quality, making more marketable cullet available, and supplying cullet at competitive prices. Equipment improvements at MRFs are critical in segregating more of the glass from the waste stream and generating a cleaner cullet stream. Glass recyclers accept cullet from the MRFs and use a variety of sorters, dryers, sensors, and automation systems to distribute cullet into multiple streams that meet glass manufacturer requirements. Magnetism, eddy currents, X-ray fluorescence (XRF), density, particle size, visible light, hyperspectral imagining, and other techniques are employed to meet specifications. Continuous improvement is needed in automation and diagnostics, faster and more accurate sensors, on-line sensors, and advanced quality assurance protocols to supply cullet at ever higher quality standards at market-driven prices. These advancements are needed to increase the fraction of post-consumer cullet recycle and to satisfy the two drivers of cullet recycle, lower costs and higher quality.