Nowadays, cullet is one of the main raw materials for the glass industry in Europe. In 2015 Europe hit 73% of glass cullet recycled, with furnaces producing green coloured glasses with more than 90% recycling rate. Because of cullet increase in the furnace, glass producers have experienced an increase of defects in the final glass container. As a matter of fact, cullet comes from waste, either mono-material or multi-material and it can be possibly contaminated by ceramic, stones, glass-ceramic etc. These issues are managed mainly by the application of improved sorting technologies in the cullet treatment plant and with a proper, updated set of technical specifications. Following the high demand for clean flint cullet, the recyclers have installed new colour sorting machines able to produce high quality coloured and non-coloured flow from the mixed colour cullet. The introduction of such machines has had a positive impact on the amount of cullet recycled, however, some unexpected contradictions have been registered. The redox of cullet fed is strongly impacted by the relative amount of the different colours. Small variations can modify the redox of the batch, introducing instability on glass colour, especially in the case of reduced glasses of redox stability, lead content and minimisation of CSP stones in the produced glass container, has lead to an increase of rejects in cullet life cycle. This paper will provide an overview of the main processes applied in Europe to sort cullet, and the strategies applied to improve the total amount and quality of recoverable glass. That he end, the SSV analytical approach for quality monitoring and assessment will be describe.
