Ethan Clarke
Glass and plastic are two of the most popular and useful materials of modern times. Despite this, the recycling rates for both materials vary greatly across the world. Glass, for example, is recycled at a rate of 90% in Switzerland and Germany, while the US only recycles about one-third of its used glass. Plastic, on the other hand, often ends up in landfills or is incinerated, contributing to climate change and air pollution. However, when recycled, both glass and plastic can be transformed into new products, reducing the need to create new materials and minimising waste. So, how exactly are these materials recycled?
Glass and Plastic Recycling Characteristics
| Characteristics | Glass | Plastic |
|---|---|---|
| Recyclability | Glass is 100% recyclable and can be endlessly recycled with no loss in quality | Plastic is also recyclable, but not all types of plastic are accepted by local authorities |
| Collection | Glass is collected from drop-off bins or curbside bins and delivered to recycling facilities | Plastic is collected from homes, businesses, and local recycling centres and sent to Material Recovery Facilities (MRFs) or Plastic Recovery Facilities (PRFs) |
| Sorting | Glass is sorted by colour and size, and contaminants are removed | Plastic is sorted by type using sorting equipment such as optical sorters, and contaminants are removed |
| Reprocessing | Glass is crushed, blended, and melted with sand and other starting materials to make new glass products | Plastic is washed, shredded, ground into flakes, heated, and extruded into new pellets, which are then sold to be moulded into new products |
| Benefits | Glass recycling reduces the need for raw materials, energy costs, and pollution | Plastic recycling optimises the lifespan of plastic, reducing the need to create new plastic |
| Challenges | The US recycles about one-third of its glass, while other countries like Switzerland, Germany, and the UK have higher recycling rates | Most plastic items collected as recycling are not actually recycled due to the complex waste industry and illegal dumping |
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What You'll Learn
- Glass is recycled by crushing, blending, and melting it with sand and other materials
- Glass cullet reduces the need for raw materials and saves on energy costs
- Plastic is collected from homes, businesses, and recycling centres, then sorted and washed
- Plastic is shredded into flakes or pellets and made into new products
- Plastic recycling is rarely done properly, with most ending up in landfills or being burned
Glass is recycled by crushing, blending, and melting it with sand and other materials
Glass is one of the most popular materials in the zero-waste community. It is nonporous and impermeable, which means there are no interactions between the glass packaging and the products inside. This results in no aftertaste and ensures that products inside a glass bottle keep their flavor, strength, and aroma. Glass is also popular because it is endlessly recyclable and can be recycled back to its original use without losing its quality and purity.
However, glass recycling rates are surprisingly low. In the US, only 33% of waste glass is recycled, and the market for recycled glass is shrinking. This is partly because fewer things are packaged in glass these days, with plastic being a more common packaging material. Another reason for low recycling rates is that glass put into the recycling bin is often used as cheap landfill cover, and consumers may contaminate entire recycling bins by tossing non-recyclables into them.
Glass that is recycled is crushed into a granular material called cullet, which is then blended and melted with sand and other raw materials to create new glass products. One kilogram of cullet replaces 1.2 kg of raw materials, and using cullet also helps manufacturers save on energy costs. For every 10% of cullet included in the glassmaking feed mixture, the energy needed to keep the furnace at high enough temperatures falls by nearly 3%. Using cullet also reduces greenhouse gas emissions during manufacturing. For every 6 metric tons of cullet used, glassmakers can cut 1 metric ton of CO2 emissions.
In addition to being recycled into new glass products, crushed glass can also be used in roadbeds, remediation work, and to make concrete. A New Zealand company is turning used beer bottles into environmentally-friendly sand, which can be used in construction and road projects.
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Glass cullet reduces the need for raw materials and saves on energy costs
Glass is a commonly used packaging material, seen in everyday items such as bottles for water, juice, beer, wine, and glass jars for food preservation. The production of glass containers requires a large amount of raw materials, including silica sand, soda, and dolomite, as well as a substantial amount of energy. Sand, the primary raw material used in glass production, is sourced from riverbeds and seabeds, which disrupts the natural ecosystem.
Glass cullet is recycled waste glass that can be used in the production of new glass packaging. Using glass cullet reduces the need for raw materials, as it replaces the amount of silica sand, soda, and dolomite required in the production process. Additionally, cullet reduces energy costs by lowering the amount of energy needed to melt the raw materials during manufacturing. The use of glass cullet also helps to preserve non-renewable energy sources such as natural gas, fuel oil, and electricity, which are commonly used in the production of glass packaging.
Glass is endlessly recyclable and can be recycled back to its original use without losing its quality and purity. However, it is important to note that the rate of glass recycling is relatively low. In America, only 33% of waste glass is recycled, with approximately 10 million metric tons of glass disposed of each year.
To improve the rate of glass recycling, it is essential to ensure proper recycling practices. Glass items that can be recycled include bottles, jars, and most glass items that are rigid and maintain their shape. However, items such as drinking glasses, eyeglasses, mirrors, and light bulbs should not be recycled.
By increasing the rate of glass recycling and utilizing glass cullet in the production process, we can further reduce the need for raw materials and energy costs associated with glass manufacturing.
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Plastic is collected from homes, businesses, and recycling centres, then sorted and washed
Plastic is collected from homes, businesses, schools, and recycling centres. The collection is done by local authorities or independent waste collectors, who transport the plastic to transfer stations. These stations act as central locations for the recycling to be collected before it is moved to a recycling facility.
At the recycling facility, the plastic is sorted by type. Sorting is done by colour, thickness, and usage, either manually or by machines. Sorting is important for ensuring the quality and safety of the new recycled plastic. For example, shampoo bottles should not be mixed with drink cartons.
After sorting, the plastic is washed to remove any impurities such as labels, glue, dirt, and food scraps. A quick rinse is generally preferred to extensive washing, as it helps save water. The washing process ensures that the last impurities are removed before the plastic is processed into new products.
Following the washing stage, the plastic is shredded into smaller-sized pieces, which can then be used as additives or sold as raw material. Shredding also allows for the removal of more impurities, such as metals. The shredded plastic is then melted and extruded into new recycled plastic pellets, which can be sold and used in new products.
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Plastic is shredded into flakes or pellets and made into new products
Plastic waste can be recycled through mechanical or chemical recycling, with the former being the most common and direct method. The process of mechanical recycling involves cleaning, sorting, cutting, shredding, agglomeration, pelletizing, and finally reprocessing the plastic waste through injection moulding, blowing, or extrusion. Shredding the plastic helps to reduce material costs, recover value, and improve product quality.
The shredded plastic flakes are then passed through an extruder, and different types of plastic pellets are obtained. These plastic pellets can be used to make new products. The neat plastic pellets can be used to make the parent product, with or without mixing non-recycled plastic pellets. Mixed plastic pellets, on the other hand, are mainly used for making low-quality products.
The pelletizing process involves putting shredded or agglomerated plastics through an extrusion and pelletizing process to produce pellets of a uniform size. This increases the efficiency of the product manufacturing process due to the higher bulk density of the pellets compared to the shredded or agglomerated forms. During the extrusion phase, the plastic undergoes mixing, homogenization, compression, plasticization, and melt filtration.
The final stage of plastic reprocessing involves manufacturing processes such as extrusion, injection moulding, blow moulding, and film blowing. The extrusion process in this stage is similar to the previous one, except that the die takes the form of the output product. The material is introduced to a rotating horizontal screw with heating elements that plasticize the waste, and the screw compresses it. The injection moulding process involves feeding the mix through a hopper that presses it into shape.
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Plastic recycling is rarely done properly, with most ending up in landfills or being burned
Plastic recycling is notoriously difficult to carry out effectively. While glass is endlessly recyclable and can be recycled back to its original use without losing quality or purity, plastic recycling is rarely done properly, with most plastic ending up in landfills or being burned.
The process of recycling plastic involves grinding it up, melting it down, and reforming it. This type of mechanical recycling requires proper sorting and cleaning of materials, which can be time-intensive and expensive. It is also very difficult or impossible to recycle many types of plastic more than once without causing the material to acquire defects and contaminants. Many recycled plastic materials contain significant levels of unwanted toxins.
The variety of plastic types further complicates the recycling process. There are thousands of different types of plastic, and they cannot be melted down together. Sorting the various types of plastic for recycling is challenging and costly. Additionally, plastic degrades with each turnover, and the cost of recycling plastic is not economically justifiable when compared to the low cost of using oil to make new plastic.
The reality is that most plastic ends up in landfills. Despite public efforts to recycle, such as placing plastic items in designated recycling bins, a significant portion of plastic waste is ultimately disposed of in landfills. For example, in Oregon, landfill workers bury all plastic except for specific items like soda bottles and milk jugs. Similarly, in Southern Oregon, recycling companies used to send plastic trash to China, but when China stopped accepting it, they struggled to find alternative buyers. As a result, most of the plastic ended up in landfills.
The plastic that is not landfilled is often burned, contributing to air pollution and the release of toxic chemicals. The burning of plastic waste, especially in open-air settings or without proper controls, can lead to the emission of harmful substances, including dioxins and furans, which have detrimental effects on both human health and the environment.
While some facilities are attempting to reprocess plastic cups and containers, the numbers are relatively low. According to a Greenpeace report, no plastic, not even soda bottles (one of the most recycled items), meets the threshold to be considered "recyclable" by the Ellen MacArthur Foundation New Plastic Economy Initiative. The report also highlights that plastic production is increasing, while the percentage of recycled plastic is decreasing.
The challenges and costs associated with plastic recycling, along with the profitability and convenience of producing new plastic, have led to the current situation where plastic recycling is rarely done properly, and most plastic ends up in landfills or is burned.
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Frequently asked questions
Glass is 100% recyclable and can be recycled endlessly with no loss in quality. Glass is collected from people's homes and businesses and taken to a facility where it is sorted and inspected for contamination and hazardous materials. The glass is then crushed, blended, melted, and mixed with other starting materials like sand, soda ash, and limestone to make new glass products.
Plastic is collected from people's homes, businesses, and local recycling centres and sent to a Material Recovery Facility (MRF) where it is sorted by type. The plastic is then washed, shredded, and sorted further before being melted and extruded into new recycled plastic pellets, which are sold to be used in new products.
After being collected from people's recycling bins, plastic is sent by rail or truck to waste-sorting facilities, or Material Recovery Facilities (MRFs). Here, the plastic is sorted by type and baled before being transported again to the next facility.
Cullet is recycled glass that has been crushed and melted down and is useful in glass manufacturing because it reduces the need for raw materials and the energy costs associated with glassmaking.
Plastic recycling often involves a complex global waste industry, including waste haulers, governments, and individuals, which can lead to issues such as illegal dumping, open burning, and health and environmental risks for communities near dumping sites. Additionally, a significant amount of plastic collected for recycling is not actually recycled and ends up in landfills or incinerators.
