Glass fines - Final Report

In Australia, over 1.3 million tons of packaging glass is consumed per annum. Each year only around 40% of the used glass in this pool is recovered nationally via a complex system of collection, sorting and re-processing. The shortfalls in used glass recovery are system wide; beginning at the point of resource degradation through commingled kerbside recycling collection, and extending right through to the various regulatory frameworks and commercial imperatives that impact recovered glass commodity values, and ultimately recycling rates. When this system is combined with an influx of imported packaging glass, often of a lower cost than locally recycled or produced glass, the capacity for increasing the rate of glass recovery becomes a significant challenge. Throughout the recovery process, glass packaging is progressively broken into ever smaller pieces called cullet. Cullet develops as glass packaging moves from the point of consumption to binning, collection and transportation to material reprocessing facilities. At each stage along this path the size of glass cullet is broken down further and mixed with small particles from other waste streams caught in the process, to eventually form what is known as glass fines. Glass fines are a hard waste to sort and the lowest value in the mixed waste stream due to their size, colour mix, and the range of non-glass contaminates that are additionally a part of the recovery system. Despite the high value the public holds for glass recycling, glass fines are in fact a by-product of a recovery process that enables the systemic degradation of an otherwise perfectly recyclable material. As a waste stream glass fines present a paradox, where they contain an extraordinary amount of embodied energy and highly refined silica, but they have a marginal resource value as they are unable to serve as feed stock for conventional glass manufacturing. While glass fines can be largely seen as a by-product of an ineffective mixed waste recovery and sorting process, they are also actively generated by the same system as a solution to other pressures. For instance, when the commodity market for recycled glass is strong the glass fines are largely produced as by-product that the process attempts to limit through complex sorting chains. However, when the commodity value of recycled glass is low (due to silica being cheap, or a glut of recovered glass), otherwise easily sortable and recyclable glass cullet is frequently crushed and mixed with glass fines further reducing its value. Such outcomes are compounded by poor regulatory frameworks, low virgin material prices, and a steady stream of imported material into an already saturated glass manufacturing system.