Virgin products or recycled cullet: the two faces of raw materials in the centuries old story of glass production
The history of glass
Only after the blowpipe was invented (around the beginning of our era), it was possible to give bottles and glasses a different shape. Quickly, people learned to give glass different colours by adding certain substances during the melting process. Glass itself was probably invented around 2500 B.C. in Egypt or Mesopotamia. At first, it was exclusively used for the production of decorative objects. The Egyptians were the first to use glass in utensils. They wrapped hot, viscous glass around a clay core to manufacture bottles and jars for the preservation of liquids such as balms and perfumes.
The production of glass
Glass mainly consists of silicon oxide, better known as sand. Merely molten sand is not suitable for the production of bottles. A melting agent is required, i.e. sodium (Na2O) or potassium (K20). In order to obtain processable glass, a solidifying agent is required: calcium (CaO). Since 1830, it is assumed that a ratio of 6 parts of sand, 1 part of soda and 1 part of calcium is a good combination.
Currently, hardly any glass packaging is made on exclusively raw materials. The use of recycled glass cullet instead of raw materials is continuously growing.
A new green bottle can be made from 90% recycled glass cullet without any concessions where shape, colour and quality are concerned. Colourless or flint glass packaging contains approximately 50% recycled glass cullet.
The use of recycled glass (cullet)
Currently, the most important raw material for the production of new glass is “recycled glass”. The recycled glass cullet must comply with the quality standards of the glass manufacturer. Strict norms apply to the presence of ceramics, stones and porcelain, heat-resistant materials, metal, plastics and organic materials. In addition, the cullet must have the right colour, size, composition, etc.
The purer the cullet are, the more cullet can be used for the production of new glass. The use of recycled glass offers the following benefits for glass manufacturers and for the environment:
- A lower emission of CO2: up to 45% less CO2 than when using raw materials in the production of green glass at 90% use of cullet
- Lower energy consumption: Per 3 % use of cullet, 10% of energy is saved.