Closing the glass recycling loop

Recycling has the wind in its sails. While the EU is ratcheting up its recycling targets and the value of secondary raw materials is widely applauded, the Netherlands is working to secure a key role as a ‘raw materials roundabout’. Momentum is building. Each waste stream follows its own pathway to higher quality processing. This series of articles spotlights a single waste stream in turn. Part 5: Glass.

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Closing the glass recycling loop

Glass has eternal life

Recycling has the wind in its sails. While the EU is ratcheting up its recycling targets and the value of secondary raw materials is widely applauded, the Netherlands is working to secure a key role as a ‘raw materials roundabout’. Momentum is building. Each waste stream follows its own pathway to higher quality processing. This series of articles spotlights a single waste stream in turn. Part 5: Glass.

By Han van de Wiel  Translation by Derek Middleton  ©copyright

Glass is an ideal form of packaging for drinks and preserved foods, and other foods too. It does not react with other materials, it is hard, impenetrable to oxygen and easy to clean and sterilise. The Netherlands is one of the leading European countries in glass recycling. Each year about 80% of used packaging glass is returned to the manufacturing process, well above the European target of 60%, but below the Dutch target of 90%.

To give glass recycling a boost, Nedvang (the industry organisation responsible for registering the recycling of packaging materials under the various product agreements) recently launched the Glas in ’t Bakkie (‘Bottle in the Bank’) campaign. The campaign aims to raise public awareness of the importance of glass recycling and encourage more people to return waste glass for collection. Lids and leftovers, it loudly proclaims, are not a problem. Glass recyclers can easily remove these impurities. ‘Lots of people don’t throw any jars and lids with leftovers of jam or mayonnaise in the bottle bank because they think it’s not allowed or they cannot be bothered to clean them,’ says Bianca Lambrechts of Maltha, the Dutch market leader in glass recycling. She is pleased the Netherlands has set itself a higher target than required by EU legislation. ‘It means we still have a lot to do. Glas in ’t Bakkie has to raise the collection rate by 10%.’ She says glass recycling has far less environmental impact than using primary raw materials. ‘Making glass from cullet uses a lot less energy than smelting sand and sodium carbonate because cullet has a lower melting point.’ Every 10% increase in cullet (crushed glass) lowers the energy needed by 2–3%. A green beer bottle that consists of 80% cullet saves about a quarter of the energy input, and a kilo of cullet avoids the emission of 0.25 kg sub Using cullet also reduces the use of sand, sodium carbonate and quicklime.

Quality impulse

The leak in the glass recycling loop is largely down to the consumer, say Gerard Pille and Goos Kers of Owens-Illinois (O-I), the world leader in packaging glass with three sites in the Netherlands. O-I wants to increase the percentage of cullet used in its production facilities worldwide to 60% in 2017 – the current figure is about 40%. The ratio of cullet to primary raw materials depends on the colour of the glass and the wishes of the customer. Green glass may contain more than 85% cullet, but clear glass must contain no more than 60%, because in clear glass even the slightest contamination leads to some deviation in colour.

According to Pille it must be possible to raise the Dutch recycling percentage. ‘In Belgium they achieve percentages of 95% to 98%. Behaviour cannot be changed overnight, but I am convinced that improvement is possible.’ Michel Maas of Van Tuijl Glasrecycling also looks to Belgium. In Belgium the glass items that can and cannot be recycled are clearly displayed on every bottle bank and collection vehicle. ‘This could make a big difference here as well. Glass is the only resource which can be recycled endlessly.’

The Netherlands has an extensive glass collection infrastructure. Almost every municipality has surface or underground containers for clear, green and brown glass, although some municipalities may not be up to quite the same standard as the overall picture. Maas: ‘The bottle bank is a fantastic thing, but unfortunately some people use them as rubbish bins for china, plastic and any old rubbish, you wouldn’t believe it.’

The key thing in glass recycling is removing contaminants. In every 1000 kilos of cullet, the glass factories accept up to 20 grams of ceramics, stone and porcelain (CSP). Glass is a durable product, but every piece of stone or porcelain could cause a breakage. According to Maas, the glass recycling industry has made a huge step forward in quality and glass recycling companies are delivering increasingly clean cullet to glass factories. Maas: ‘Ten years ago glass factories accepted a CSP content of 50 grams per 1000 kilos. Now it is 20 grams, and it is not inconceivable that it will fall to 15 grams. Our machines can do that, but to make a real improvement we have to go back to the source: the bottle bank. Clean glass waste means greater efficiency.’

Eighty per cent of used packaging glass in the Netherlands goes back to the glass factory, much more than the EU target of sixty per cent, but less than the Dutch target of ninety per cent

Plate glass

Besides packaging glass, plate glass – sometimes called window glass – is collected from glass companies, municipal waste recycling centres and temporary collection points on building sites. The quality of plate glass is higher than that of packaging glass. ‘That is why recyclers are so keen on it,’ says Cor Wittekoek of Vlakglas Recycling Nederland (VRN), a foundation that stimulates the recycling of plate glass. ‘Recyclers use it to lower the amount of lead in packaging glass.’ This is crucial for exports to the United States, where the permitted lead content of glass is lower than in Europe. Fifteen per cent of collected plate glass is used in the production of new plate glass, 70% is used in the production of packaging glass and the remainder is turned into glass wool.

The crisis in the construction industry has considerably reduced the supply of waste plate glass. Less renovation of homes means the amounts of waste plate glass are 30% lower than in 2010. VRN is working for maximum recycling of plate glass cullet in the plate glass industry. ‘That is real cradle-to-cradle recycling,’ says Wittekoek. However, much plate glass cullet is still used in the production of glass wool. Because it is not yet possible to recycle used glass wool into new glass products, this represents the end of the line for the glass. Each year an estimated 10 kilotonnes of waste plate glass is thrown away with construction and demolition waste, even though this is not permitted. VRN is looking into ways to ensure this waste plate glass is also separately collected.

The glass recyclers are searching for markets for residual wastes. Maltha and several partners have developed a special tree sand, which has been awarded the Cradle to Cradle certificate. Van Tuijl works with a partner that processes the CSP material into glass foam granulate. Although this material is not yet a success in the Netherlands, in Germany, Austria and Switzerland it is used as an insulation material and even a building material. The glass recycling loop is almost complete. The final pieces are always the hardest.

Separating the mixed glass stream
The contents of bottle banks consist mostly of glass (more than 97.5%). The remaining 2.5% consists mainly of metals (such as screw tops and lids, which can be recycled), combustible waste (such as plastic, cork and paper) and ceramics, stone and porcelain (CSP). Removing the CSP from the glass stream involves a slight loss, because some glass is removed in the process. The newest glass recycling facilities are able to recover 90% to 95% of the waste glass stream in a good recyclable condition.

In the recycling facility the collected glass passes through a grid that sieves out the largest contaminants. The glass is then crushed. Metal caps and lids are extracted with magnets. The pieces of CSP are detected by laser, camera and X-ray techniques and removed with jets of compressed air. Light contaminants such as cork, paper and bottle tops are sucked off the conveyor belt, and an eddy current machine removes the non-ferrous metal fragments. The cullet is then inspected and if the level of impurities is still too high the cullet goes back through the process again. In the final step the cullet is exposed to the outside air for three to ten weeks so that bacteria can decompose the organic matter.

Bianca Lambrechts (Maltha):"A new campaign has been launched to raise the collection rate by 10%."
Gerard Pille (Owens-Illinois (O-I)):"Behaviour cannot be changed overnight, but I am convinced that improvement is possible."
Cor Wittekoek (Vlakglas Recycling Nederland):"Recyclers are keen on plate glass because of its high quality."
Michel Maas (Van Tuijl Glasrecycling):"Clean glass waste means greater efficiency."
Goos Kers (Owens-Illinois (O-I)):"The leak in the glass recycling loop is largely down to the consumer."

Vision DWMA

Glass can be recycled endlessly. The Netherlands is one of the leading glass recycling countries in Europe, returning about 80% of used packaging glass to the manufacturing process each year. Efforts are being made to increase the collection and recycling of plate glass (window glass). Recycling glass has far less environmental impact than using primary raw materials to manufacture glass (less energy and raw materials use, lower CO2 emissions).

Key focus points for maximising packaging glass recycling:

  • Consumer behaviour in the end-of-life stage
  • A clear collection infrastructure and arrangements

Learning from best practices in other countries could provide the necessary pointers to improve these aspects. For example, in Belgium the glass items that can and cannot be recycled are clearly displayed on every bottle bank and collection vehicle.

To optimise plate glass recycling new options for separate collection need to be investigated.