There are two issues which have the potential to hinder the closed-loop recycling of container glass in the UK: the colour imbalance of glass packaging consumed versus the containers manufactured and the collection of waste containers mixed or colour seperated.
The target for glass recycling in 2008 is 60%, equivalent to 1,320,000 tonnes per annum (based on current figures). At this level of recycling glass container manufacturers can use 919,000 tonnes of recycled glass with a surplus of some 400,000 tonnes of green glass.
Improvements in cullet specifications can drive this up towards 1,100,000 tonnes.
The reason for the colour imbalance is that the UK manufactures mainly clear glass while half the recycled glass collected is green and it was proposed that the problems of surplus green or collecting mixed glass containers could be resolved if the cullet colour could be rendered immaterial by neutralisaton of the colour of the glass in the furnace.
Jointly carried out between GTS and the University of Sheffield's Engineering Materials Department the project set out to research the feasibility of neutralising glass colour in the furnace through both a worldwide research study and a series of laboratory-scale trials. Also covered were investigations into glass colour mechanisms and the practical investigations of dilution, decolourising and colour balance, wet chemical extraction and alternative colouring systems.
The project received support from WRAP and UK glass container manufacturers.
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