Glass recycling process

How does glass get recycled?

Waste glass (called cullet) is collected for recycling either from kerbside schemes or from bottle banks.

Once the local authority has collected the material, it is stored with other, similar glass at transfer stations (such as the ones at Guildford, Sunbury, Epsom and Leatherhead) until ready to be transported to plants where it is made into new products.

Glass that has been separated according to colour usually gets made into new bottles and jars. Mixed colour glass cullet can be used for many different products.

Making new jars and bottles

All the pictures in this section are courtesy of OI which is a company that recycles of lot of glass from Surrey. Their website can be found here.

On arrival at the plant, the cullet is weighed, offloaded and stored until it is needed. Colour by colour, cullet is transferred to the processing plant.

Firstly, the material is picked to remove things that should not be there - bottles of the wrong colour, other packaging materials and anything else that has found its way into the load of glass. This includes window glass and glass cookware, which does not melt properly in the furnace.

The glass is then passed through a series of processes:

• Magnets extract any ferrous metals

• Air suction removes paper and foil

• Crushers and screens reduce the material to the correct size for the batch

In addition, modern recycling plants have infra red systems for the detection and removal of ceramics, such as small stones and crockery, which would otherwise cause serious flaws in the manufacture of new containers.

When cleaned, the cullet is delivered to the batch plant. Here, the recycled material is combined with other, virgin raw materials into the precise mix required for melting into new glass. These materials include sand, limestone and soda-ash.

The batch material is fed into the furnace, which is the size and depth of a small swimming pool. Here it is heated by gas burners to melt and fuse into glass. The complete process takes around 24 hours, as the material flows through the furnace, reaching a temperature of around 1600C. This is where the cullet comes into its own, as it melts at a lower temperature than virgin raw material, providing significant energy savings.

Molten glass flows from the furnace in a stream. As the stream is allowed to fall under its' own weight it is cut into "gobs" that are guided into machines, where they are formed into new bottles. Modern machines can make more than 300 bottles a minute.

Next, the bottles are annealed for up to an hour in a long oven called a lehr. This treatment helps give the glass its strength.

Finally, the new containers are inspected for quality before being packed onto pallets ready for delivery to factories where the containers are filled with new products.

Other uses for glass

Recycled glass can have may other applications. These include:

• Water filtration

• Grit blasting

• Fibreglass Insulation

• Sports turfs

• Aggregate

• Brick, cement and concrete

Please see here for more information.