Glass recycling: a cycle with a future

Glass is a fascinating material: durable, versatile and 100% recyclable without loss of quality. But how exactly does glass recycling work and how does it benefit our environment and society?

The recycling of glass containers used for packaging such as bottles and jars has already been well-established in many countries. But how does this process work?

• Collection and sorting: glass packaging is collected and separated from other waste and transported to recycling centres or plants. In some countries like Germany, for example, the glass is already sorted by colour when collected at bottle or glass collection banks: into clear, brown and green glass. All other colours are assigned to green glass because it has the highest tolerance for colour deviations.
  
• Processing: If not done beforehand, the collected glass is sorted by colour. It is then filtered, crushed and foreign matter is removed.
  
• Melting: The cleaned glass is melted down at high temperatures and processed into new glass.
  
  
• Application: The recycled glass returns to retail in the shape of new glass packaging.

Because glass recycling makes a significant contribution to environmental protection by reducing waste volumes and saving resources.

• Resource savings: By reusing glass such raw materials as quartz sand, soda and lime are saved. Each piece of glass packaging today contains 60% recycling glass on average, green packaging even up to 90%.
  
• Energy savings: Melting recycled glass consumes markedly less energy than manufacturing glass from new raw materials. Each 10% proportion of recycled glass reduces energy consumption for producing new glass by roughly 3%. This translates into a saving of over 300 kg CO2 per ton of recycled glass used in the production of new glass packaging.

In Germany glass recycling looks back on a long tradition and counts among the most efficient recycling processes – to the tune of 2 million tons of recycling glass are collected there annually. The recycling rate for glass packaging therefore stands at 84.1% (correct as of 2021). But glass is also increasingly recycled in other European countries and the world over. In Europe (EU + UK) the recycling rate amounts to 79% (as of 2020). However, individual countries still vary widely from each other. Stepped-up efforts – also in educating citizens – are therefore key to achieving the European target of 90% by 2030.

Flat glass can be recycled, too. Used flat glass is collected, crushed and admixed to new glass. However, the percentage of recycled glass in flat glass is – as a rule – lower than in container glass packaging since higher requirements are made on glass purity and homogeneity in flat glass. In addition, the recycling of flat glass as used in windows, doors and façades is more complex than the recycling of glass packaging.

• Elaborate sorting: flat glass must be separated from other construction components and often coatings must be removed.
• Crushing: the glass is crushed and processed into glass granules.
• Sorting: the glass fragments are sorted by colour, size and purity.
• Cleaning: any remaining impurities are removed in down-stream cleaning steps.

The greatest challenges in flat glass recycling lie in the wide variety of impurities, the different glass compositions and the high demands made on the purity of the recycled glass. If, however, high-quality recycled glass can be reclaimed from used flat glass, it can also be used for the production of new glass products after being melted down again.

Recycled flat glass is mostly used:

• as an admixture: crushed glass is used as an admixture in concrete production to optimise the strength and weight of concrete.
  
• in insulation material production: glass fibre reclaimed from recycled glass can be used for making efficient thermal insulation materials.

• Resource savings: recycling also saves important raw materials and energy in this segment.
• Circularity: flat glass can be returned to the construction material cycle.
• Building ecology: recycled glass contributes to more sustainable building.

Flat glass recycling is still in its early days. Whereas some countries have already scored initial successes, others still need to cover substantial ground. Read more about this in our current features you find under the link below.

One thing is clear: glass recycling is a key component of a sustainable circular economy. The recycling ratio for flat glass can be increased further through the consistent development of recycling processes and greater awareness among architects and building owners.