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The plastic recycling process: From sorting the collected plastic to a 100% recycled granulate

Plastic is currently considered as one of the biggest and most indispensable raw material for the production of products that we use in our daily life. However, from all that plastic just a little fraction is recycled. Happily, there are more and more techniques available that can realize an efficient and effective plastic recycling process so that a bigger share of the plastic can be recycled.
Knowledge base item - Plastic recycling process

The plastic recycling process

A recycled plastic product does not just arise out of nothing. This is a complicated and especially a very accurate process. The end goal is a 100% pure plastic product (preferably 100% recycled). Before this is achieved, the plastic first needs to be collected, sorted, washed, shredded and granulated (in an extruder). Moreover the entrie plastic recycling process should be continuously monitored to ensure the quality and safety of the final end product.

1. Collecting and separating residual waste

Residual waste is collected on a large scale by households and companies which is then transported to local factories with big separation machines. Here a first distinction is made in organic and fine material and the rest of the waste. The organic waste is separately processed into gasses. The remaining residual waste is further sorted with the help of separators, sieves and infrared technology. The result is a distribution in soft plastics, hard plastics and drink cartons. These different streams of plastic waste is then transported to the sorting installations where an even more detailed separation of the waste is taking place.

2. Sorting of incoming plastic waste (plastic bags)

Besides the regular waste also the plastic waste is separated in households, often by using plastic bags. These bags are collected and transported to sorting installations. Here the bags are torn open and is then followed by an extensive sorting process. With infrared technology the different types of plastic are separated from each other. The sorting of types of plastics is important for ensuring the quality and safety of the new recycled plastic. For example it should be prevented that shampoo bottles are mixed with drink cartons. Furthermore the metals should be removed from the plastic. Finally the plastic can also be further sorted on colour, size and thickness.

3. Washing and shredding

However, before the sorted plastic waste can be processed into granulate it is important that all the plastic should go through an extensive washing process. This makes sure that the last impurities are removed from the plastic. The sorted plastic (on type and possibly size, colour and thickness) is often shredded first. This results in shredded plastic flakes that are then washed thoroughly in multiple steps. Impurities such as labels, glue, dirt and food scraps will be removed from the process. The pure plastic will then be even shredded more into fine flakes and is ready to be processed into granulate.

4. Granulating

The plastic flakes are poured into an extruder and is then squeezed through by a screw with very high pressure. Because of the warmth that is released here the material will melt. At the end of the extruder the liquid plastic is cooled down and a recycled plastic bar is created. This bar is then cut into granules. These granules are the 100% pure granulate, also called regranulate that is suited for the processing into new plastic recycled products. Think for example of the processing of granulate into foil using a film blowing machine

Continuous quality assurance

During the entire plastic recycling process it is very important that the quality of the final end product is contiuously watched over. This means that during the process multiple quality inspections are carried out. There are products that can not be removed from the process with the separation technologies. By performing quality checks also these products can be removed from the process. Furthermore, samples of granulate that are produced from the sorted plastic are regularly drawn out of silos to test the homogeneity and quality of these samples. This way for example colour deviations in the granulate are detected and corrected.

With the TagTec technology it is nowadays possible to sort granulate and then monitor it on what the earlier use has been of the original plastic products. The result is that the safety and quality of the final product can be monitored continuously.

Why recycling plastic?

Why should we all start recycling plastic on large scales now? This is because the requirements in the plastic recycling industrie are becoming increasingly strict. In the near future a plastic end product needs to consist for a minimum of 50% out of recycled plastic. Furthermore the demands for the quality will be stricter. End customers are soon mandatory to offer food and beverages in plastic that for 95% consists of recycled material which is never used for non-food articles.

To meet these strict requirements it is necessary to come up with innovative solutions for the plastic recycling process so that in the future a bigger share of the produced plastic will be recycled.

Accuratetly sorted granulate results in a doubling of the market value of the granulate. A stumbling block here is however that many companies hold back on sorting big percentages of the plastic because of the expensive systems that need to be purchased. This way it will be hard to earn back all these investments. Sensor Partners offers finacially interesting sensor solution so that the sorting process of granulate will be more attractive. The result is a 60-70% cheaper sorting process of recycled plastic.

For more information on which sensors offer a solution to optimize the plastic recycling process it is possible to contact one of our experts!

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