Glass recycling

Recycling glass is a simple but hugely beneficial process. Below are the 10 steps to recycling glass.

1.       Raw materials

Modern glass containers are manufactured using very precise, complex and highly controlled technology. However, the raw materials used are simple and abundant.

The four main ingredients:

       I.            Recycled glass

     II.            Sand

  III.            Soda ash

  IV.            Limestone

As much recycled glass is used as possible as this enables the other materials to melt at a lower temperature. The colour of the glass is controlled by the iron content and the addition of minor colouring agents.

Even though basic ingredients are used in vast quantities, accurate weighing and mixing to achieve precise proportions is absolutely critical. This procedure is carried out electronically in the batch house which supplies the mix to the furnace.

A typical furnace within the glass container industry will operate 24 hours a day, 365 days of the year producing around 300 tonnes of glass a day. This production of glass is continuous for the furnaces’ lifetime of approximately 10 years.

Up to 90% recycled glass is mixed with raw materials and fed into the furnace where the recycled glass remelt s and becomes pure and pristine again.

2.     Glass container making

The glass is cut into ‘’gobs’’. These are individual pieces which are literally fired down into the forming machine. Within seconds the glass is pressed and blown into shape within a mould and emerges as a glass bottle jar or jar.

Each and every container is subjected to a rigorous series of quality checks which includes:

§  Automatic online, wall thickness inspection

§  Squeeze testing

§  Sealing surface inspection

§  Side wall scanning

§  Base scanning

At intervals a sample of the containers being produced is taken aside for dimensional checks, capacity checks and pressure testing. If any problems are found in production since the last check, it set aside for further inspection. This procedure is followed until the production again passes the tests.

The data from online and offline quality checks is fed continuously back to the ‘hot –end’ forming machine operators who can then make adjustments to remove the problem at the source.

Each container has a series of dots moulded into the in sweep which create a code number when ready by the online inspection machines. This quickly highlights any bottle faults being seen and faults in the mould which is creating it.

3.     Transportation to retailers     

The bottles and jars are filled with food and drinks and taken to retailers such as supermarkets where they are sold to consumers.

Many bottles of beer, spirits and soft drinks are direct to retailers such as pubs, restaurants and night clubs where they are sold to consumers.

4.     Use at home

The rest of the glass is taken home by consumers who eat or drink the products inside the bottles or jars.

They then make a crucial decision, do they throw it in the bin or take it to the recycling bank?.  If they throw it away it will go to landfill where it will stay forever, never breaking down. If they take it to be recycled, the whole cycle will begin again and the glass can go on being recycled again and again – forever.

5.     Dumping glass

Any glass which is put into the rubbish bin will go into landfill with all the other waste.

6.     Glass collection

Glass can be recycled at glass bank all over the country. Glass bank has always been colour separated. A small number are now being switched to mixed glass. It may not be possible for the industry to colour separate glass collected mixed from recycling banks, to get the maximum value and environmental benefit glass bank must remain colour separated.

Kerbside collection schemes make it easier and more convenient for the public to recycle their glass. In areas which introduce kerbside, the glass recycling rate usually doubles. It’s unfortunate that just few houses has kerbside collections of glass, this calls for a rapid  increase in order to meet glass recycling targets.

Glass collected at the kerbside is usually colour separated on the vehicle or is sold as mixed glass for colour separation or for use in alternative markets. Glass which is collected co – mingled is usually separated at a material recycling facility but is generally suitable only for low value markets.

7.     Commercial collection

Glass from pubs and clubs is usually collected colour separated in wheeled bins, but often it is collected in the mixed bins because of lack of space.

Where glass is collected mixed it can be colour separated and used within the container industry. This is happening now and will grow in the future as more collection in the pubs and clubs are established.

8.     Removing contaminants

Recycled glass contains contaminants which must be removed before the recycle glass is used to make new containers. Metal, paper, plastic, organics and pyro-ceramic must all be removed. This is done using manual inspection and high-tech equipment utilising metal detectors, vacuums, crushers, screens, lasers, digital cameras and even x-rays to detect and remove contamination.

Some recycling plants have colour separation facilities which use manual inspection and digital scanning cameras to separate glass which have been collected in mixed colour form. There is limited capacity for this process, which requires high levels of investment and produces relatively high waste levels. However, this technology will grow and is essential in making the most of glass recycling.

9.     Container making

Once the recycled glass has been cleaned and prepared it is mixed with raw materials and the whole process begins again.

This cycle can be repeated an infinite number of times and the quality of the glass will never deteriorate. Each time bottles and jars go round this cycle they generate environmental benefits:

§  345 kwh of energy is saved for every tonne used

§  225kg of CO2 is saved for every tonne used.

§  1.2 tonnes of raw materials quarrying is saved for every tonne used

§  1 tonne  of landfill  is saved for every tonne used

100% of recycled glass can be used to make new glass bottles and jars, without any loss in quality. Glass containers made with high levels of recycled glass are as pure and clear as those made solely from virgin raw materials. Green bottles are made with up to 90% recycled glass content. If more glass was recycled, recycling rates for all glass could be increased.

Alternative uses

Once the container industry has used around 350,000 tonnes each year other alternative markets are made available, such as:

§  Water filtration

§  Fluxing agents in bricks and clay pipes

§  Shot blasting

§  Aggregates

While these uses are much more beneficial than landfill they are less environmentally beneficial than close loop recycling into containers, for example even after all the transport has been taken into account , use in close loop container making is 50 times more beneficial to the environment than use in aggregates.

However, without alternate markets such as aggregates the extra green glass that is collected will undermine the value of all glass collection.