MATSE 81
Materials in Today's World

Recycling of Glass

PrintPrint

Glasses are the most common commercial ceramics, however, there is little economic incentive to recycle glass. The raw materials for producing glass are inexpensive and readily available. Glass is relatively dense, which makes it expensive to transport which adds to the costs of recycling. Glass must be sorted before being processed during recycling, usually done manually which adds to costs. Not all glass is recyclable, and the glass comes in many different forms. Please watch the following video (3:29) which summarizes the points about recycling of glass emphasized in your e-book and this website.

To Watch

Click for transcript of Recycling Glass.

In this lesson we will learn about recycling glass. Although the usage of plastics is more common as it is lighter and less prone to breakage, glass is still widely used. Glass is used to make soft drink bottles, food containers such as plates and glasses, and vases. Glass is primarily silicon dioxide with a small percentage of calcium oxide and sodium oxide. The beauty about glass is that it is a hundred percent recyclable and unlike paper it does not break down into smaller components with each recycling process. For the moment, only glass bottles can be recycled not crystal glass, window glass, and windscreen glass on cars. This is because other materials are added to this type of glass and the recycling process at the moment cannot separate those materials from glass.

First, glass bottles and containers need to be collected and separated according to their color. This is important because the different colors are made due to many different substances that are added. Ideally, green glass will be recycled into green glass and brown glass into brown glass. Any the labels present must be removed and the bottles must be thoroughly washed to ensure that any residual contents and adhesives are removed. The bottles are then crushed into smaller pieces before they are melted. Why is the step important? Please pause the lesson to think about this and resume when you are ready.

This is an important step because the smaller pieces mean that melting will occur quicker due to the increased surface area. Following on the same idea if you want it to fully dissolve sugar in water, powdered sugar would dissolve faster than a cube of sugar. The smaller pieces of glass are then melted, poured into a mold, and allowed to cool and harden. The bottles are now fully recycled and ready for reuse. This recycling process uses a lot less heat energy than glassblowing and it's therefore, a more environmentally friendly option. As well as being recycled into bottles, mixed glass can be crushed to form glass aggregate and used as a cheaper substitute for gravel.

In summary, glass is fully recyclable and can be recycled a virtually infinite number of times without being degraded into other products.

In the next section, we will discuss some of the limitations of recycling.