The plastic industry is in transition and facing a set of challenges, the most prominent of which is delivering high-quality secondary feedstock in large enough volumes to meet the ever-growing demand. Over the last decades, plastic production rates shot up unprecedentedly. According to Plastics Europe, global plastic production reached 390.7* million metric tons in 2021, of which 352.3 million MT is virgin-based (90.2%) and only 32.5 million MT (8.3%) from post-consumer recycled plastics. A closer look at the distribution of the total plastic production by type reveals that polyolefins make up the majority of it with manufacturing rates amounting to approximately 180.5 million MT. Although there is an affluence of plastic on the market and further increase expected, recycling rates remain low and access to high-quality recyclates is limited. In times when legislation and recycled content targets become increasingly stringent and time-sensitive, it is crucial to unlock the potential of existing solutions. 

A glance at the current state of recycling shows that waste management infrastructures, from collection to sorting and recycling, have become more mature in numerous countries around the world, but the capacities available are still not keeping pace with the ever-increasing demand for recycled resin. More investment is needed to establish solutions at scale, producing the volumes and qualities required. Fortunately, some bottlenecks can be overcome with sensor-based flake sorting solutions. As part of the recycling process, flake sorting narrows both the quality and quantity gap for polyolefins (PO), polyethylene terephthalate (PET) and a growing number of other applications. Recyclers using the latest flake sorting technology can capture more types of material, maximize yield and maintain profitable operations.  
 

Quantum leap in recyclates quality 

High volumes of superior feedstock at hand

A plastic recycler can process more than 100,000 tonnes of polymer flakes per year, depending on market demand and material availability. With recent shortages of available materials, adaptability is key to maintaining profitable business. Waste streams and market demands are, in fact, highly dynamic. If the supply of recyclable polymers on the market is limited, but demand is high, plant operators often have little choice but to turn to more contaminated post-consumer waste to meet market demands.  Exceptional purity requirements persist regardless of the volume to be processed and the type of recoverable feedstock, challenging recyclers to reach even higher qualities from increasingly more contaminated sources.  

Whereas PET bales processed in a recycling facility mostly consist of only one target material (PET), PO bales are a mix of two valuable materials: polyethylene (PE) and polypropylene (PP). The share of each material type in the PO infeed is hard to predict and can change with each bale. One bale could be a 50/50 mix of PE and PP, and the next could be a 70/30 mix. Irrespective of the input composition, both PE and PP flakes must be accurately identified and separated to create high-purity fractions for recycling. 

Until advanced flake sorting and purification methods were introduced, the infrastructure lacked the technology to separate PP from PE cost-effectively. Less sophisticated flake sorters can solely purify one material type and remove only small amounts of contaminants, thereby often limiting their use to PET recycling plants. Furthermore, higher throughputs were hard or impossible to realize. For example, if a recycling plant uses less advanced flake sorters to process a PO bale composed of 60% HDPE and 40% PP (not considering other contaminants), the infeed would have to be sorted by belt-sorters before shredding, when the material size is big enough to allow for accurate separation of PE and PP. 

Flexibility for predictably higher yield

Infeed materials continue to become more complex. Depending on the respective contamination level and purity requirements, supplementary sorting steps are often required to purify the target fraction. Smaller operators with flake sorting installations can reap a lot of benefits from the system's capabilities and efficiencies.  First, flake sorters can be easily integrated into existing plants because they require little space compared to other processing machinery, which makes them ideal for upgrading the sorting and purification capabilities of an existing recycling line. Second, it is possible to run multiple sorting steps within a single unit. This means operators can choose to balance throughput in favor of higher recovery rates and purity levels as needed. At the same time, smaller recycling companies can profit from the flexibility of processing a wider range of materials, thanks to the possibility of working in batches on a single unit. The scenario is different in high-volume plants, where operators can install multiple sorting machines in parallel or cascade setups to maximize throughput and qualities without increasing operation times. Regardless of the installation setup, flake sorters offer unrivaled flexibility, performance and generate reliable flake qualities. Thus, the sorting results are predictable and so is the recycler’s yield.