It basically sounds perfectly logical. If packaging consists entirely or almost entirely of a single material, this makes it easier to sort by type and therefore supports recycling. There are plenty of examples of what is known as monomaterial: packaging made of polyethylene, polypropylene, cardboard or paper, for example. In Germany, packaging is considered a mono-material - or single-material solution - if it contains no more than five per cent foreign material.
Recyclability, sustainability, circular economy: the myths about mono-material packaging
The idea that mono-material reduces the amount of residual waste is just as logical, as it makes it intuitively easier for consumers to separate waste and therefore less packaging is sorted out as non-recyclable. So why isn't all packaging made from mono-material? There are a number of good reasons for this. And it's worth taking a closer look at them.
#1: Monomaterial is always the most environmentally friendly solution
The environmental footprint of packaging cannot be determined by the packaging itself. Glass packaging, for example, has enormous strengths in terms of hygiene and recycling, but if the entire production and life cycle is included in the environmental balance, the picture is relativised depending on the application.
Reckitt Benckiser has calculated what would happen if the 4,000 tonnes of PET bottles used worldwide for a particular soap brand were to be replaced by the more than 32,000 tonnes of glass bottles required: This would result in almost 12,000 more tonnes of CO2 emissions in production, 48 percent more trucks would be needed for transport, and they would have to cover 3.3 million more kilometres.
The idea must also be applied to monomaterials. Although high recyclability is an important component of the circular economy and a good environmental balance, it is by no means the only one. For example, how much effort is required to achieve the necessary barrier functions? What are the transport costs and CO2 footprint? Not every packaging made from mono-material is particularly sustainable in this regard. Peter Désilets, Managing Director of Pacoon, describes the factors that need to be taken into account as follows: "When comparing PET bottles with disposable glass bottles, the equation is quite simple. However, the environmental balance of a non-returnable PET drinks bottle compared to a returnable glass bottle is known to be negative as the number of bottles in circulation increases." However, according to Désilets, this is not enough to calculate the environmental balance: "We also have to take into account technological developments along the supply chain, such as lighter glass walls thanks to new tempering methods, e-mobility during transport and the transport routes for the empty PET bottles from the collection point were apparently not taken into account or suppressed in the Benckiser analysis. Empty disposable packaging travels several hundred kilometres from collection, sorting, recycling to new production until it is used again as packaging for bottling."
#2: Monomaterial can be used everywhere without any problems
Composite packaging exists for a reason. On the one hand, its complex structure serves as a barrier: barriers protect the contents from the influence of moisture or oxygen and prevent ingredients from escaping into the environment - for example, to preserve the flavour or to prevent harmful substances from escaping. If mono-packaging does not fulfil these requirements, this can reduce the shelf life of products (and therefore cause more food to end up in the bin). Alternatively, manufacturers may have to use more preservatives and other additives, which is just as questionable from an ecological point of view as it is from a medical one.
Secondly, it is about mechanical stability; composites are also used to resist deformation or damage. Many mono-materials do not come close to composite packaging in this respect - which is why more material has to be used, which in turn results in higher transport costs.
Research into mono-material packaging that fulfils both requirements is being carried out in many places. Reifenhäuser Maschinenfabrik, for example, has developed a process to replace stand-up pouches made from a PE-PET composite with those made from PE monomaterial. However, according to the company, the production of the pouches is "not trivial", there are a number of machine parameters that need to be set correctly and a "certain amount of recipe expertise" is required. Speaking of machines, there is another stumbling block when using packaging solutions made from mono-material. Not every filling machine can fill every material, and mismatches are particularly common with tubular bags.
Fraunhofer is also working on this issue. The Fraunhofer Institute for Process Engineering and Packaging IVV is researching a completely recyclable mono-material film that fulfils both barrier and mechanical requirements. The basic approach here is to modify the film material retrospectively so that its properties differ from those of the original polymer granulate.
Problem solved, you might think. But, like so many things in the packaging sector, it's a little more complicated than that. "Polypropylene is also favoured for films because it offers better recycling opportunities. But there are new challenges here too: narrower temperature windows during processing, more expensive material and different impact and tear strengths are just some of the issues that need to be mastered. But there are already some solutions. Barriers that do not impair the good recyclability too much and only account for a few per cent are also important here. After all, it should remain 'mono'."
#3: Monomaterial is perfect for recycling
In principle, mono-material packaging is actually easier to recycle than many composites. However, there is still the question of infrastructure and sorting facilities. In many countries, the necessary recycling plants do not exist in which all types of monomaterials can be sorted and recycled - which means that they often end up as waste in thermal utilisation.
In order to pass as a 'monomaterial' with a low proportion of foreign substances, additional thin barriers such as PVOH or EVOH may have to be applied. These are usually harmless in recycling, but the right mixture is important here. A barrier that is too thin may reduce the shelf life of the foodstuff, but will withstand the 5 %. However, if product safety is to be guaranteed, 'it can be a little more' and you could slip over the 5 %. This may not necessarily harm the recycling process, but it is no longer 'mono'.
We need to move away from one-fits-all thinking models, says Peter Désilets: "As in many other areas, we should move away from generalised statements such as mono-material and look at the effective success of packaging: How good is the recyclability, how good is the recyclate obtained from it, which can then be sold and used?"
The wrong colour application or printing ink can also make recycling more difficult or result in an inferior recyclate. "I would prefer an 85-15 material from which I can obtain high-quality recyclates than a 95-5 material that ends up being incinerated. The PPWR will also focus on this; the actual recyclability 'at scale' will be emphasised here and a certificate must also confirm this," says Désilets.