Float glass and recoverable container glass recycling is contributing significantly to a decrease in the amount of waste accumulated in landfills which largely extends their lifespan.

The most effective approach to glass recycling, both float and container glass, is to submit cleansed glass to a second smelting in a glass furnace in order to manufacture a new glass product. Additional benefits of using cullet as a material during glass smelting are:

• Reduction of CO2 production through minimal use of fuel or coal materials such as lime powder, soda, or dolomite, which produce CO2 during decomposition.
• Reduction of SOx emission e.g. green glass can be smelted without the use of fining agents (sodium or calcium sulfate).
• Reduction of chlorine and fluorine emission.
• Reduction of fly ash production through limited use of unprocessed materials which contain, on average, 25% more fly ash with granule size less than 0.10 mm.
• Reduction of NOx emission through reduction of fuel consumption in a glass furnace.

It is assumed that 1kg of cullet replaces 1,2kg of unprocessed materials, lowering the cost of materials and resulting in a significant environmental effect. According to data published by The German Association of Glass Manufacturers the addition of cullet in glass production decreases the need for glass furnace charge by:

• 0,72 tons of quartz sand, main component of which is SiO2 quartz.
• 0,25 tons of sodium carbonate Na2CO3.
• 0,18 tons of lime powder consisting of CaCO3

The use of properly cleansed glass waste allows a significantly lower use of unprocessed minerals which means a crucial reduction of required interference with natural environment. The production of glass containing cullet is less energy intensive than production using raw materials because every 10% of cullet reduces the need for energy by 2.3-2.8%. Up to 25% of energy used to produce glass using unprocessed materials can be saved by using cullet instead. The addition of merely 1% of cullet to the glass batch will decrease the energy consumption by ~8kJ/kg of glass. The energy savings come mostly from the lower temperature level of glass smelting that includes cullet. The smelting point of glass batch including cullet is 1000oC while glass batch consisting of unprocessed materials only reaches 1200oC – 1300oC. Larger addition of a cullet results in a decrease of temperature of smelting as cullet reaches liquid state faster, which simplifies and accelerates reactions occurring during glass smelting.

Lowered temperature influences also the amount of degassed substance created by raw materials. The presence of cullet in the batch decreases chimney corrosion, extending the lifespan of a tank furnace and decreases pulverization of the batch inside the glass furnace. It results in a decreased emission of ashes and ingredients volatilizing with exhaust. Cullet contains less chloride and fluoride than raw materials which results in a decreased emission of chlorine and fluorine.

A very important parameter is a decreased quantity of CO2 emitted during the process of glass smelting in glassworks, resulting not only from a decreased amount of CO2 emitting resources but also through limiting energy consumption (up to 25% depending on the amount of cullet used) used to heat the glass furnace batch. CO2 reduction is very difficult as it is highly dependent on the amount of fuel used and the type of glass furnace batch used. Therefore, it is important to lower energy consumption while maintaining the efficiency of production. Thanks to using cullet in the process of glass smelting, the volume of glass furnace batch per unit produced is reduced and temperature of smelting is lowered. This in turn, results in lowered emission of CO2 in the amount of 220kg per ton of reused glass.

Currently, an emphasis is put on the reduction of CO2 emission. The possibility to reduce the emission CO2 in glass smelting can be achieved through increased usage of cullet in the glass furnace batch. However, implementation of this task needs to be preceded by adequate preparation of cullet in terms of both quantity and quality. This is why the processes of cleansing, separation and crushing of glass are so important in the overall process of glass recycling.

Another very important aspect of DSS Recykling activities is implementation of obligation regarding container glass recycling in accordance to environmental policy of the European Union. The obligation, presented to Poland by the European Union concerns the levels of recovery and recycling of container glass. According to the policy, 600 000 Mg of container glass needs to be recycled on annual basis, which requires further investments in the field of technological lines for glass recycling.

It is worth noting, what level of cullet reuse is achieved by other European countries.

Some German glassworks use recycled glass as 80% of input in their glass furnace batch, whereas in Switzerland this level can reach up to 100%.