Packaging food with recycled plastic

Illustrations: JeRoen Murré

Just open your fridge and you’ll see that plastic is the main packaging material for the food we bring home. Mixed salads, mushrooms, spreads, chicken, as well as ketchup, dairy produce and soft drinks: they are all usually packaged in plastic. Cola and ketchup are stored in PET bottles (polyethylene terephthalate), yoghurt in a polypropylene (PP) bucket, and the large plastic milk bottle is made of high-density polyethylene (HDPE). Then there are mixed plastics: salami is displayed on a thin composite tray made of PET and polyethylene (PE), and is sealed with a film made up of various plastic layers. And most bottle tops are made of polyethylene.

This diversity makes recycling challenging. In an ideal scenario, you would recycle plastic by type and colour, and then grind it up and wash it to remove food residues. Ultimately, this recycled plastic is processed into pellets with which manufacturers make new bottles, trays and foils.

But using most types of discarded plastic to make food packaging is not permitted at the moment due to risk of contamination with undesirable substances. Only PET bottles that are collected separately via deposit machines provide the raw material for new bottles. Plastic from a bucket of yoghurt, a milk bottle or a tub of ice cream does not return to the kitchen but gets a new life after recycling as a paint bucket, a garden chair, a shampoo bottle or a garbage bag. Some of the collected plastic is incinerated because it is too contaminated to be recycled, or contains too much undesirable plastic – from construction waste or toys, for instance.

Invisible contamination

The main reason we hardly recycle any food packaging into new food packaging is that contaminants are absorbed into the plastic from food and the rubbish bin and we do not accept that potential risk, says Ulphard Thoden van Velzen of Wageningen Food & Biobased Research. ‘You don’t want those substances in the plastic because of their odours and aftertaste, as well as their possible toxicity.’ Examples are limonene (citrus aroma), nonanal (rose aroma) or octocrylene (a UV filter in sunscreen).

Packaging made of polyethylene (PE) and polypropylene (PP) behaves like a sponge, absorbing substances in the fridge or the rubbish bin. And not all these substances can be rinsed out in a water bath. ‘We wanted to get a full picture of which substances enter the plastic at which stage in its use and recycling. Which volatile substances are involved, and in what quantities? Once you know that, you can estimate whether the plastic is suitable material for food packaging.’

In the InRep project that Thoden van Velzen works on, research is being done on one particular form of plastic packaging: the large white milk bottle with a handle. ‘This HDPE milk bottle is designed for recycling: the label is shrink wrapped around the bottle, and it has a blue cap. Those parts are easy to separate. What is more, these bottles are made for the Dutch supermarkets by a single company that uses one grade of plastic from one manufacturer. So every milk bottle is made of the same type of plastic. The big question was: is this quality maintained during recycling?’

Sifting through rubbish

To answer this question, researchers sometimes need to sift through waste. ‘We picked up these milk bottles from the milk factory and the consumers, and we fished out bottles at the collection and sorting point to analyse them.’ In the lab, the plastic milk bottles were ground up and then measurements were taken to see which volatile substances were present. The contamination was generally not too bad, says Thoden van Velzen. ‘We saw relatively few volatile substances in milk bottles out of consumers’ plastic waste containers, even though there were all kinds of packaging in them. There were a few extra aroma substances, but not very many and nothing you couldn’t get rid of. We even saw that the number of volatile substances in the plastic tended to go down at each stage between the factory, the consumer’s home and waste processing. That was a surprise.’

There was one exception to that rule, though: milk bottles that the researchers collected from a sorting facility usually contained more volatile substances. After some detective work, the source of that contamination turned out to be the baler in which the sorted packaging is compressed into a compact bale. ‘The milk bottles are in amongst all sorts of other PE packages. Under pressure, the caps jump off and residues escape from the bottles. If a milk bottle in the baler happens to be next to a tube of sunscreen, that’s reflected in the measurements. If you want to avoid that kind of contamination, you shouldn’t put the milk bottles in the baler with other packaging, but keep them separate.’

Thoden van Velzen and his colleagues simulated the recycling of used milk bottles on a small scale in the lab, to see what happens to the levels of volatile substances. ‘That entails simply grinding up, washing and drying the plastic. Then we found that the level of volatile substances was lower still, even lower than in a new milk bottle. Our jaws dropped when we saw that. We always believed that recycled plastic was dirtier than new plastic, but the opposite turned out to be true.’

The lab test is different to the real world, where used milk bottles are not fished out of the plastic waste and recycled. ‘It’s the principle that counts,’ says Thoden van Velzen. ‘The study shows that recycled plastic can be perfectly clean. But the costs are an obstacle. Sorters ask: who’s going to pay for that?’

Compulsory blending

Recycled plastic cannot currently compete with cheap, virgin plastic made from oil. A proposed European regulation making blending of recycled materials compulsory in 2030 could change that. If 10 per cent of packaging material has to contain recycled materials, a market grows up spontaneously. That’s the idea. According to Thoden van Velzen, that is true, but he nevertheless notices that producers of packaging material are reluctant to invest in recycling. They are doubtful as to whether their material will be positively assessed by the food safety watchdog EFSA. The European Food Safety Authority looks at how plastics are recycled and assesses the presence and the risks of undesirable substances.

‘I talk to numerous people in the packaging branch about separate recycling of milk bottles. The question they ask most often is: What are the chances of the EFSA making a positive recommendation? Even though I know we can produce clean plastic after recycling, I cannot make any promises. You can never completely rule out the possibility that a contaminant enters at some point, and that is a guarantee that the EFSA requires. In that case, companies say, we are not going to invest tens of millions in recycling. On the one hand, I appreciate the EFSA’s scientific rigour, but they don’t take costs and feasibility into account.’

For optimal recycling, the collaboration of the general public is crucial too. That goes for plastic packaging as well as for other waste flows such as paper, glass, food and garden waste, bulky waste, electronics, small-scale chemical waste and construction waste. It’s important that people observe the rules and make the right choices: plastic bottles go into the recycling bin, but a length of drainpipe doesn’t.

Where and how people live also plays a role in the sorting of waste and the extent to which people can help with it, says Eveline van Leeuwen, professor of Urban Economics in Wageningen and the director of the Amsterdam Institute for Advanced Metropolitan Solutions. ‘In a flat you often have less space for separating organic waste than you do in a terraced house with a garden. Personal characteristics and the environment play a role too: how much do you care about the environment, do you have time, what are the norms and values in the neighbourhood? And the possibilities are often laid down by the municipal policy. In Amsterdam, whether sorting takes place at source or after collection even varies per neighbourhood.’

In discussions about waste collection and recycling, two concepts come up a lot: source and post-collection separation of plastic, metal and drinks cartons (PMD). If a municipality opts for source separation, then residents are expected to dispose of plastic, metal and drinks cartons together in one bin. If post-collection separation is chosen, all that packaging goes into the residual waste bin and is extracted at the waste processing plant. PMD is unique in this regard, since post-collection separation is not an option for other waste flows such as paper, food and garden waste, glass and clothing. Consumers have to keep those apart and put them in the right container. Waste processors say that PMD waste that is separated at source is cleaner than packaging extracted from the residual waste, as it has been in contact with less food waste. Less contamination is good for plastic recycling, although new sorting techniques are improving post-collection separation. This system is easier for consumers, especially in neighbourhoods with high-rise blocks of flats.

Improving recycling

Which system works best under which condition is the subject of research Van Leeuwen is doing in the Dutch Research Council project MUNITION. In this project, her group is working with Nijmegen researchers on a computer model of the collection and recycling of plastic waste. ‘It’s a digital model of a town in which we bring together the factors affecting waste separation: people, the municipality, waste processors, the neighbourhood. If we put all that into a model, we can then calculate the consequences of different scenarios – like source and post-collection separation – to get an idea of where there is scope to improve the recycling of plastic. Where can we make adjustments?’

There are chemists, economists and behavioural scientists working on the project. Experiments are carried out with aims such as identifying the circumstances under which people choose to separate their waste. The optimal collection system is not necessarily the one that produces the highest percentage of recycled plastic, says Van Leeuwen. The project looks beyond the yield and the purity of the polymers. ‘How to assess what’s the best system is something that we’re still working on. We compare two main scenarios – separation at source and post-collection – in terms of general welfare, so the impact on the economy as well as the environment. What are the costs for the collectors, the recycling companies, and the municipalities? The social side is addressed as well: how much do we ask of citizens and what’s in it for them? And we look at the quality of the plastic collected.’

The goal is to develop a digital resource with which municipalities and waste processors can calculate the implications of different collection methods per municipality or neighbourhood. ‘If a municipality introduces a new waste collection system, residents have to change their behaviour, so you can’t just reverse the change two years later. What is more, it can help in explaining why there’s a different policy for the city centre than for the suburbs, even though one of the approaches might not have an optimal impact on the environment.’

Van Leeuwen thinks customizing the approach is more helpful than a discussion about source versus postcollection separation. ‘If you look exclusively at the quality of the recycled plastic, source separation might seem better. But if you look at the bigger picture, including the economic and social costs, then I think what the best option is can vary per neighbourhood or region.’

According to Van Leeuwen, optimal recycling is important but the rising use of plastic packaging deserves attention too. The percentage of recycled plastic in use has increased in recent years, but the overall use of plastic packaging is outstripping it. ‘There are certainly good reasons for using plastic, for example to keep food fresh for longer. The environmental impact of food spoiling if it’s not plastic-wrapped is a consideration. But at the same time, we need to find options for using less plastic. We’ve already found we can do without plastic bags in the supermarket and disposable cups at the university. It’s not for nothing that the motto is: reduce, reuse, recycle. First reduce use, then promote reuse, and only then recycle.’