Post-consumer-glass containers are made from naturally occurring sand, soda ash and limestone ingredients. It’s the packaging material of choice for a majority of consumers, especially those concerned about their health and the environment. Glass is superior for preserving a product’s taste or flavour and maintaining the integrity or healthiness of foods and beverages. It is the only packaging material guaranteed to leave your food and body untouched unlike others that have been proven to leach harmful chemicals.
The primary ingredients used in the manufacture glass containers for packaging of food, drinks, pharmaceuticals, cosmetics, etc are sand (mainly silica, SiO2), limestone (CaCO3), and sodium carbonate (also known as soda ash, Na2CO3). The primary materials are blended together, heated to temperatures of up to 1600°C and the melt used to create durable, strong, impermeable, easily shaped, and inexpensive glass containers. Crushed recycled glass in varying quantities is added to the blend with the actual quantity being determined by the quality of the recycled material and the type of glass being manufactured.
Crushed, furnace-ready recycled glass is often referred to as cullet and is an extremely valuable material in the glass manufacturing process. Blending cullet into the batch (sand, limestone and sodium carbonate mixture) allows manufacturers to reduce the quantity of virgin raw materials required i.e. for every kilogram of cullet used in the batch 1.2 kg of raw materials is replaced. As re-melting cullet is less energy intensive than re-melting virgin raw materials, both energy and material costs will be proportionally lower as higher rates of cullet are incorporated in glass manufacturing. A more comprehensive list of the benefits derived from recycling glass can be found at the end of this article.
In spite of the benefits, manufacturers are limited by the cullet is available to them at a manageable cost. Post-consumer glass is clean and pure, and highly recyclable. However, getting clean, furnace-ready cullet requires a lot of processing after the waste glass bottles are collected which increases the cost of this material.
The historical steps involved in the process are collection, crushing, cleaning, sorting, transport, and final use.
Processing of Post-Consumer Glass
The collection step involves recovering the waste glass from bottle bins or from businesses generating waste glass containers in the course of their daily operations. The collector will deliver the glass to the glass processor where the bottles are crushed or broken into pieces which are suitable for cleaning and sorting.
Cleaning of the soluble contaminants i.e. residual contents etc is achieved by washing before the glass passes through sieves to remove any insoluble organic content. Magnetic and Eddy current separators are then used in order to remove any metallic contamination whilst air suction removes lighter components such as paper and plastics. The resultant glass is clean but comprises of mixed colours which must be separated into clear, green and brown components which is the next stage in the processing operation.
The separation of the glass into different colours is achieved via optical sorting technology. An optical sorting machine is equipped with a conveyor, cameras and sensors that use white light, laser light and infrared backlight to detect the different colours of glass passing along the conveyor. The grades of glass include clear, green, or brown, often also referred to as flint, emerald, and amber, respectively and depending on the response, glass pieces are ejected from the conveyor depending on how they transmit the different incident light beams. The output from this stage will be three streams of glass cullet separated into individual colors or any combination of the three main flint (clear), amber (brown), and green colors.
After processing, the cullet is ready for use and is shipped to the glass container manufacturing plant where it is used as a raw material in the production of new glass containers.
Glass has many wonderful properties being inert, attractive, formable into complex shapes, and providing excellent gas barrier properties which are important to the shelf-life of carbonated beverages such as soda and beer. However, due to its fragility as a packaging material, glass containers are manufactured with thick walls which adds substantial weight to the overall package. A major advantage of glass from a production standpoint is the relatively low cost of the raw materials that go into it. Unfortunately, this cost advantage becomes a disadvantage from a recycling standpoint. Because the packaging material itself does not have much value post-use, there is a perception that the material is not very recyclable when it is infinitely recyclable without any loss in quality. In a lot of cases, shipping costs dictate the economic viability of the glass recycling process as the value of the cullet once treated is relatively low.
Some Benefits Derived From Recycling Glass
Recycling of Glass Saves Energy
Recycled glass melts at a lower temperature than its raw material components. The amount of energy required to make glass from scratch is 40% more than that needed to recycle it. Research has shown that recycling of a glass bottle can produce enough energy to light up a normal bulb for 4 hours or power a TV for 90 minutes.
Recycling of Glass Reduces Industrial Pollution
Recycled glass reduces the emissions of air and water pollution by around 20% and 40% respectfully. Reducing industrial pollution benefits not only the environment but also the entire ecosystem.
Recycling of Glass Conserves Natural Resources
The main raw material used in glass production is sand, so quarrying operations which scar rural landscapes can be reduced by simply depositing used glass at any recycling point. Sand is the second most traded natural resource after water, and due to extraction it is now becoming scarce in some parts of the world. Recycling glass saves on the need to obtain more raw materials to make new glass so natural resources are saved by recycling glass.
Recycling of Glass Conserves the Landscape
Glass litter in parks and the wider countryside is a long-term problem. Due to the inorganic nature of glass, it will never decay. If a glass bottle goes to a landfill, it will take almost a million years to break down. If a glass bottle is recycled, it will take just a month for it to get to a store shelf as a brand new glass container. Recycling glass is very simple, and you can start the process by dropping the glass you have into recycling bins. Additionally recycling glass reduces demand on landfill space for disposing of used glass containers.
Recycling Glass Saves Consumers Money
Since glass can be recycled with no loss in quality, new glass can be produced from recycled containers without added the cost of acquiring raw materials. Glass products that are produced at a lower cost during the manufacturing process due to the use of recycled materials can then be made available to consumers at a lower price.
Recycling Creates Jobs
Recycling and reuse create at least 9 times more jobs than landfills and incinerators i.e. a report published in the UK calculated that at least 50,000 new jobs could be created by 2025 if the rate of waste recycling increased from 45% to 70%.
Contact PEL Waste Reduction Equipment if you have any questions on glass recycling or managing waste glass containers in your business.
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