recycling; plastic; plastic waste; polymers; NIR technology; NIRS

Chapter 36

Wasting no time in reducing plastic waste from food containers

📂 Case overview: The food detectives discuss the problem of accumulating plastic waste, frequently resulting from food containers and plastic bottles. They want to contribute to alleviating the problem, so they take on a case based at a recycling plant. See how they help their client monitor product composition and quality during the recycling process using real-time NIR data.

The detectives are sitting at a favorite café and reminiscing about their summer holidays. Everyone has wonderful stories of soaking in the sun, drinking cocktails and enjoying the freedom of doing nothing, but lazing around. Leave it to Nancy Beef to stir the conversation into a more serious direction.

She recalls visiting a country, where every food item she ordered was placed in plastic containers, then those placed in plastic bags, etc. etc. etc. She was terrified of the amount of single use plastic items she encountered and was afraid to picture the mountains of plastic waste resulting from this gluttony of consumption.

It is not the first time the detectives are reminded of hazardous topics when it comes to food consumption. They recently closed a case on fighting pollutants, such as dioxins, in food products and in their last case, they faced off against microbial contamination in beer.

The team is also no stranger to the topic of food packaging. But while they have explored the safety of food packaging with the food is still in it, they had never considered what happens when the food is gone and the empty packaging turns into waste, particularly to plastic waste.

Nancy Beef is quick to emphasize the dire nature of the topic by pointing out that 90% of the 10,000,000,000 tons of plastic waste produced in the last 70 years is still around. By now, the holiday mood has completely dissipated, and the team is ready for action!

Shallot Holmes, as he so often does, manages to pull out a client case file that might satisfy the team’s desire to do something to help the cause of reducing plastic waste. This specific client works in a recycling plant and is wondering how they can better guarantee the quality of the recycled product they obtain at the end of the process.

The recycling site produces thousands of tons of single variety re-granulates every year. These granulates serve as an alternative to virgin plastic to help conserve fossil resources and reduce plastic waste. Downstream users of the re-granulates rightfully demand high quality of the product, so the recycling plan is looking to establish quality standards and modern testing and process methods.

Nancy Beef’s ears perk up at the mention of modern. She has just the technology in mind to help the client achieve quick, efficient, and reliable quality control: near-infrared technology.

The food detectives carefully read over the file before they contact the client. The recycling plant produces granulates and compounds from polyethylene (PE), polypropylene (PP), polystyrene (PS) and polyolefin (PO) combinations from used packaging left for recycling. The re-granulates are then produced from plastic waste and can replace new plastic in a 1:1 ratio.

Their recycling process includes collecting the plastic waste, intensively washing it, separating it according to type and properties and crushing the material. The resulting plastic flakes are the sample material which needs to undergo quality control.

Nancy Beef suggests again to analyze the plastic flakes with NIR technology. The others agree that it’s a good idea and they head over to the customer to put their plan into action.

The team installs an NIR system directly on the feed hopper to monitor the mixture components after comminution. The NIR unit operates by continuously directing light in the near infrared (NIR) range onto the passing plastic flakes. Depending on the compound properties, the reflected light varies. This reflected light is detected by a diode array spectrometer and evaluated in real-time by relevant process software. The data is displayed on a monitor as a curve.

At this point in the process control, the client would need to know the compound proportions in order to achieve the desired target values during compounding in extrusion lines. Until now, the client regularly collected samples for analysis in the laboratory using established analytical methods, including NIR technology. But the client is unhappy that the procedures could take several hours to complete.

The food detectives are eager to help him obtain his results faster. They install the NIR system directly on one of the feed tanks and let the machine measure the passing flakes. In seconds, they are able to analyze the content of PE with x% contamination of PP and vice versa!

The client is astonished that with NIR-Online, he can receive continuous information on the values of the PE/PP fraction mixtures that are currently present in the plastic flakes. Now he can react quickly in the event of malfunctions to avoid costly preparation of faulty batches.

With the help of NIR technology, he can efficiently achieve desired mixing rations and properties in granule form from the flake feedstocks by mixing, compounding and extrusion. The final granulates are supplied to plastics processing partner companies.

The food detectives leave a happy client behind and feel they have played a small part in reducing plastic waste. They celebrate with an office potluck, where everyone brings their own plates and cutlery. After all, the principle is reduce, reuse, recycle and the team can certainly do all three!