r/Glasgow Tools

The different glass colours are mechanically identical from a processing perspective, I imagine with modern imaging & AI it may be possible but in general waste processing tech it simply isn’t possible.

Current processing of glass bottles to glass cullet (small pellets for use in smelting new glass) uses a rough macerator initially to smash all the bottles into ~2cm chunks, it is then fed through a loop of vibrating conveyers a few times, this loop separates glass from labels, corks, bottle caps, laminating layers & any other contaminants (generally sent to RDF). The glass then passes through a fine macerator which chops it down further.

At this stage it is considered hazardous to handle due to dust, so is passed through an enclosed loop for final vibration before being outputted into cullet piles. This final vibration is important for removing difficult to process lamination & bonding material.

These piles are graded by the glassworks, I can’t recall the exact ratio but high grade clear cullet is valued at almost 10 times the amount of general glass recycling, as it’s considered as good as raw material for fresh glass production, mid grade, which is what our general output was, is about 5x. A estimate I’ve heard thrown around is 1 green/brown bottle in a pile of 5000 clear glass bottles is enough to downgrade the whole pile through contamination, our high grade clear cullet generally came from windscreen & window recycling rather than bottles, although these come with their own challenges in separating laminating materials.

Green/brown separation is also important, but much less so than clear.