Glass - Applications

There are two main routes for recycled glass:

Primary markets – the glass recyclate is used as a primary feedstock for the glass manufacturing stor.
Secondary markets – alternative uses for the glass

Primary Markets

As glass can be re-melted an infinite number of times without any degradation of it's physical properties it would be feasible to assume that the best way of using the glass would be as a primary feedstock to the glass manufacturing industry - a closed loop. However there are a number of limitations to this as some bottle types and colours can only use certain colours and amounts of cullet, for example:

• Only 17% of glass manufactured in the UK is green glass, at the current recycling rates all the green glass can be utilised. However as recycling rates increase, saturation point will be reached. With current UK manufacture of green glass that will be somewhere around the 1.2 million tonnes point. Ultimately unless demand for green glass increases there will be a surplus of container glass.

• The quality control for the manufacture of flat glass is very high and only 10% of the potential waste arisings are suitable for feedstock. Much of the flat glass in the waste stream is heavily contaminated as it comes from the construction/demolition industry or motor industry.

Secondary Markets

There are a number of alternative uses for glass recyclate which are summarised in Table 1. Many of these uses have been proven in other countries and have been researched or are currently being researched in the UK.

Application Substituted Material Benefits of Recycled Glass

Aggregates – general fill


Natural Aggregates


Lower Cost

Free draining

Aggregates – concrete


Natural Aggregates


Lower Cost

Can increase strength of concrete

Aggregates – bound sub-base


Natural Aggregates


Lower Cost

Aggregates – Decorative


New Application


Water Filtration


Sand/gravels


More efficient filtration

Shot blast abrasives


Metal slags, sand


Non-Toxic

Silica Free

Fluxing Agent in bricks/ceramics


Mineral fluxes


Lower fixing temperatures - energy saving

Resin Composite Flooring




Pavers Blocks




Furniture/Work Tops




Art & Decorative applications




Novelty Items




Aggregates – general fill

Aggregates

Glass can be crushed to various sizes and used as a sand replacement aggregate. There are a number of applications that glass aggregate can be used:

• General fill - Glass can be used as fill specified in the “ Specification for Highway Works” aside from Classes where only specific listed materials are allowed such as Class 5 (Topsoil), providing it meets the required performance specifications.

• Bound and Unbound Road Materials – the “ Specification for Highway Works” permits 25% Glass in GSB Type 1 and Type 2.

• Concrete – Glass can be used to substitute some of the aggregate used in concrete production.
• Decorative Aggregate - the use of glass recyclate as a decorative mulch/landscaping aggregate due to its aesthetic value has good potential. A number of companies produce these materials and they have a high market value.

Filtration Media

There is a large potential for glass to be used as granular media filtration as a replacement for sand and gravel. Glass can in some instances provide a superior performance.

Abrasives

Crushed glass has been tested extensively as a blast abrasive and is currently being manufactured in the UK.

Bricks and Ceramics

Fluxing agent When mixed with clay materials finely ground glass will act as a “flux” and reduces the firing temperature saving energy costs. This will also apply to pottery glazes. The addition of glass also increases frost resistance in bricks and may reduce hydrogen fluoride emissions.

Niche Markets

Glass can be used in a variety of art and craft applications, these tend to be low volume but high value products such as stained glass.