Glass is one of the most common packaging materials found on supermarket shelves and is typically used to manufacture bottles and jars in which food and beverages are sold. It is also used for window glazing, shower doors, light bulbs, scientific equipment, etc. Yet, while glass is so prolific, many consumers are unaware of how glass is produced or what happens to it once it is thrown away or recycled.
How is Glass Made?
Glass is made from sand (silica dioxide), limestone and soda ash, which are heated together to form liquid glass. When this molten mixture is cooled it forms clear glass, which may either be spread out onto flat sheets or it can be moulded to into various shaped products such as bottles and jars typically used to package products that will not degrade when exposed to light. However, because some products are more sensitive to light, and possibly also temperature, glass is often colored amber/brown (light resistant) or emerald green (light and temperature resistant). To produce amber colored glass, such as commonly used for beer bottles, manufacturers add nickel, sulfur and carbon to the molten glass mixture, and to produce green colored glass, such as that used for wine bottles, they add iron, chromium or copper. All these materials occur naturally in the environment and are readily available.
What is the Environmental Impact of Glass?
Because glass is produced from natural occurring materials rather than harmful chemical substances it will not harm the environment or negatively impact human health as it degrades. However, as glass does not decompose, it will take a very long time to disintegrate into the ground. Consequently, bottles take up a lot of space on a landfill, and glass can pose an aesthetic pollution problem when discarded in natural areas. The biggest impact that glass has on the environment is during the production stage when carbon dioxide, a greenhouse gas, is released into the atmosphere when natural gas or fuel oil is burned to melt the raw materials in order to produce glass. These emissions contribute to atmospheric warming and climate change.
Why Recycle Glass?
Producing glass from virgin materials requires a lot of energy to create sufficient heat to melt the raw materials. When glass is recycled, it gets broken up into small pieces, referred to as ‘cullet’. This cullet then gets crushed, cleaned and sorted according to color, so that it can be used together with raw materials to produce another batch of glass of the same color. But because cullet has a much lower melting point than the raw materials needed to produce glass, the more cullet that is added during the manufacturing process, the less energy is required to melt these ingredients together. Using less energy, is not only more economical, it reduces atmospheric emissions, therefore reducing the overall environmental impact of the glass manufacturing process.
Glass bottles and jars are heavy and do not compress in size or decompose on a landfill. But, while this may be a bad point when disposing of glass on a landfill, it is beneficial for recycling. Because there is no loss in quality over time, glass can be recycled over and over and over again with no loss in the quality of the glass produced.
What Glass Can be Recycled?
Not all types of glass can be sent for recycling. When placing glass items in a recycling bin, it is best to stick with bottles and jars. Some glass items are produced using a different process and/or they can contaminate or weaken the batch and should therefore never be recycled. These include:
What happens to the non-recyclable glass?
Non-recyclable glass that could potentially contaminate a batch of recycled glass is typically sent to a landfill. However, it may be possible to keep such items out of the landfill. You just need to get creative. Instead of dumping unwanted glass or ceramic household items that are otherwise in perfectly usable condition, consider donating to a charitable organization or a charity shop that sells second hand stuff to raise funds in support of a worthy cause. Broken ceramics, mirrors and colored glass can be used for decorative mosaic arts and crafts, while contaminated bottles and jars can be cleaned up and used to store non-edible things such as nails, screws, curtain hooks, and other household or workshop items.
Glass bottles and jars are 100% recyclable, and doing so can help reduce greenhouse gas emissions that contribute to climate warming. Just be careful what you toss into the recycling bin as some glass items can contaminate the entire batch, resulting in the lot being sent to a landfill. Check with your nearest recycling center to see if they take in other types of glass, or find creative ways to prevent these items from ending up on a landfill.