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From the bottle bank to the furnace – a complete look at the journey glass takes back into new packaging, and why it matters.
Glass is one of the easiest materials to explain in terms of recycling: it goes in a bin, gets melted down, and becomes a new bottle. In practice, however, the path from a used jar to a new container involves several precise steps, each designed to remove contaminants and prepare the material for the high-temperature furnaces where new glass is made.
Glass recycling is the process of collecting used glass containers, processing them into a material called cullet, and using that cullet to manufacture new glass products. Unlike many materials, glass can be recycled indefinitely without any loss in quality or purity – a single bottle could in theory be melted down and reformed into new glass over and over again, forever.
Glass containers are collected either through dedicated bottle banks, kerbside collection schemes, or commercial collection from bars, restaurants and retailers. At this stage, glass is often already separated from other recyclables, since its weight and the risk of breakage make it impractical to mix with lighter materials like plastics and paper in the same processing line. Once collected, glass is transported to a processing facility where it undergoes initial crushing into cullet, which is easier to handle, transport and sort.
Because cullet melts at a lower temperature than virgin raw materials – sand, soda ash and limestone – higher cullet content reduces the energy required for melting, lowering both costs and emissions at the manufacturing stage. Recycling glass also reduces the demand for raw material extraction and diverts a heavy, durable material away from landfill, where it would otherwise sit indefinitely without breaking down.
The crushed cullet leaving initial processing still contains a range of contaminants: labels and adhesive residues, metal caps and rings, plastic closures, and – critically – ceramics, stones and porcelain (CSP), which are visually similar to glass but have a different melting point and, if not removed, can create defects in new glass products or even damage furnace equipment.
This is where optical sorting technology becomes essential. Glass cullet passes beneath sensors that analyse colour and composition, separating clear, green and amber (brown) glass into distinct streams, while identifying and ejecting ceramics, stones, porcelain and other non-glass materials. Colour separation matters because glass manufacturers typically need cullet of a consistent colour to produce new containers of that same colour – mixing colours limits the cullet to lower-value applications such as construction aggregate or fibreglass insulation, rather than new bottle production.
PICVISA's ECOGLASS optical sorting systems are designed to deliver precise colour separation and CSP removal at high throughput, playing an important role in maximising the recycled content of new glass packaging and keeping more material in the circular loop.
Get in touch with our team to discover how PICVISA's optical sorting and robotics solutions can fit your recycling operation.