Glass is a valuable item which is not really designed to be used in one-off applications. Unlike many thermoplastics and other similar materials, it can be cleaned and reused for all sorts of jobs. For example, food and drinks containers that are made from glass simply need to be returned to the packaging plant to be used once more. They seldom require anything more than a soak in soapy water to make them suitable for reuse in the food processing industry. Nevertheless, truly reprocessed glass takes more time and energy. Even when glass is smashed it can be recycled, but how is this achieved by modern reprocessing plants?
The key to reprocessing glass is obtaining a reasonable economy of scale. For this, collection needs to centralised and easy to reach for the public. Since glass can be sharp when it is broken, storage bins must be safe but also easy for people to place their glass in. In most cases, recyclable bottles are placed into storage bins via a small aperture which minimises risk to the public from shards. In addition, operatives who collect the glass from the bins should be fully protected, often picking up the entire bin and placing it on a truck with an empty replacement unit being made available for further collections.
Treatment and Sorting
Reprocessing is also centralised for greater efficiency and glass should be delivered from multiple collection points to each plant site across the country. Once the glass is dumped, it needs to be washed and for impurities removed. Anything that is not glass - such as paper labels, bottle tops, plastic and grime - needs to be separated from the glass itself so that the reprocessed material is as pure as possible. In addition, glass is often separated according to its colour. Green glass will need to be separated from clear glass, for instance, or the recycled products will be tinted. Likewise, brown glass from bottles needs to be sectioned off or the end product will have an off-colour appearance. Picking by hand and by robotic instruments are both systems that are used to separate glass by its colour.
Crushing and Recycling
Once processed, the glass is broken down further by crushing machines. These grind the shards of glass into smaller particles which makes them easier to reprocess. Once it the material looks more like a fine power, it can be heated up and formed into new glass as a liquid for moulding. All sorts of new product can then be manufactured, such as bottles for sale, drinking glasses, vases and ornaments.