Glass: a hard, brittle, transparent or translucent non-crystalline solid, consisting of metal silicates or similar compounds. They are made from a fused mixture of oxides, such as lime, silicon dioxide and phosphorous pentoxide.


Recycling in New Zealand

Benefits of glass recycling

Environmental benefits

Recycling glass is sustainable, energy-efficient, conserves resources, and it’s simple.

Other benefits include a reduction in CO2 gases, reduced need for quarrying and opportunity for increased NZ employment.

Glass has a lower carbon footprint on average than similar sized aluminium or plastic containers, according to a Carbon Footprint Life Cycle Assessment.

Environmental Effects 

Glass itself is not regarded as a threat to the environment because it is inert. If subjected to weathering forces, glass will break down into small particles of silica, which is one of the most common elements on earth. There are adverse effects on the environment from the original mining for the glass making ingredients.

Find link on the seaglass beach

Action and awareness in New Zealand

The Glass Packaging Forum (GPF) promotes the environmental benefits of glass packaging and manages the accredited Glass Packaging Forum Product Stewardship Scheme.

The Glass Packaging Forum  considers applications to fund research or programmes likely to result in aiding glass recovery.

The Glass Forum financially supports promoting recycling at events and /or programmes designed to raise awareness about glass recovery.

The process of glass recycling

To be recycled into more glass products, glass needs to be separated first into colours: green, brown and clear.

In Taranaki the colour sort is done at collection - as shown in this video.

It is then crushed into small pieces called cullet. Cullet is a very valuable material in the production of new glass as it helps the batch melt quickly and reduces the energy required by the furnaces by 20-25%.

Not all recycled glass is used to make new glass. Crushed glass is used as a feedstock for other industries, though most of these applications are international rather than New Zealand based .

Many large fibreglass plants are using over 30% recycled glass content for new products.

Crushed glass is being used by the world’s leading manufacturer of reflective glass beads designed for highway and airport traffic safety use. Scarce natural minerals can be replaced by using crushed glass in the manufacture of road paints, as in Canada.

There are also an increasing number of specialty end use markets, some of which are used here in New Zealand. Crushed glass is used as an alternative to sand for sandblasting, as a filter in swimming pools, as an abrasive cleaner for fine jewellery and as a small percentage of road construction material.

Way back when...the history of glass

Glass is one of the oldest and most useful materials known to man. Some glass-like substances occur naturally, like obsidian, which is produced by the intense heat of volcanoes. It is thought that seagoing merchants accidentally combined a form of soda, sand and limestone with their beach campfires, and noticed the hard, clear substance left in the ashes. These basic ingredients are still used to make glass today.

Egyptians apparently established the first known glass factory around 1400BC. By 500AD, the Roman Empire had helped to spread glassmaking techniques throughout Europe and Britain.  Flat glass was made for centuries by blowing a large bubble of molten glass at the end of a metal tube. After cutting the ends off and splitting the resulting cylinder in half whilst warm, the two pieces were softened by reheating and beaten flat on a large stone using a broad wooden paddle. The blown cylinder process was improved until the mid-19th century, when cylinders up to 12m were being split. Today it is made using rollers.

Process of making glass

Glass is made from sand (silica) and other materials melted at a very high temperature to form a molten liquid, which is then formed in various ways.

Reading this through spectacles?  Ever wondered how the lenses are made: see this video about spectacle lenses.