Environmental concerns have prompted a tremendous rise in alternative ‘sustainable’ solutions that look and feel like traditional plastic but can be composted at end of life. However, there is a rider.

These solutions sound great in principle but not so straightforward in practice, with many now recognizing that improper use of compostable plastic packaging could do more harm than good, explains Lee Metters, group business development director, Domino Printing Sciences (Domino). 

The challenge of compostable plastics

A primary concern with compostable plastic is disposal. If a consumer incorrectly disposes of a compostable plastic container in a recycling bin, it can contaminate the recyclable waste around it. 

The contamination may adversely affect waste recovery and recycling systems, which have evolved to manage common packaging materials. Introducing new materials can be problematic. 

Materials recovery facilities have been designed to segregate and handle materials that we value and those that municipal councils want to recycle – such as PET, aluminium, steel, glass, and card. 

When new materials are introduced, there is no guarantee that they will flow as they need to, or they may inhibit the ability of the system to capture existing target materials.

A small amount of compostable material can contaminate standard plastic recycling streams, leading to the waste of vast quantities of recyclable material. 

Given these issues, in January 2020, climate action NGO WRAP published new guidance materials to help businesses make informed choices when considering the use of compostable packaging. 

“Businesses need to be clear on when it is viable [to use compostable plastics], given the complexities surrounding current treatment infrastructure,” Helen Bird, resource management specialist at WRAP, said. “It is critical that end markets for recycled plastics are not compromised; people need clear instruction not to place compostable plastics in the recycling bin.” 

What should be compostable?

The key to the successful use of compostables is finding areas where collection and recycling of single-use plastics is problematic and where compostable materials could help to divert food waste from landfills. 

For example, hard-to-recycle, heavily food-contaminated items do not currently have an ideal waste stream for disposal. Such items can cause issues when placed in traditional recycling streams and can contribute to methane emissions caused by the anaerobic breakdown of residual food waste if sent to a landfill. 

This latter point is key to any discussion surrounding compostables – as methane emissions from landfill are a significant contributor to global greenhouse gas emissions, with governments worldwide committing to the introduction of mandatory household food waste collections in a bid to curb this. 

Upcoming regulations include —

European Directive, which mandates the introduction of separate collection of food waste as of 1 January 2024 within the EU.
UK Government Resources and Waste Strategy, which pledges the introduction of separate collections for household food waste in the UK by 2023.

As the scenarios below outline, the upcoming regulations present a considerable opportunity for compostable plastic packaging when used correctly. 

Soiled pots, tubs, and trays

One of the most cited scenarios where compostable packaging could come in useful is with food contact packaging, where the product is heavily contaminated by food waste and difficult for consumers to clean – for example, microwavable ready meal trays. 

Instead, a compostable microwavable tray could be placed into a food waste bin in areas where industrial composting facilities exist or, depending on the material, into a home composter. 

Any leftover food within the tray would then become compost rather than food waste sent to landfill. This would reduce the number of trays being sent to landfill and improve the quality of recyclables by keeping contaminated products out of recycling bins.

Flexible food contact packaging

Flexible plastic wrap is a popular feature in food and beverage applications in everything from single-serve condiment sachets to prepacked, ready-made salads and convenience pouches. However, these materials can be challenging – and costly – from a recycling perspective, as they can stick together and get tangled with other recyclables.

Compostable plastics could have a role to play here – especially where products are contaminated with food, as in the case of single-serve sachets. In such a scenario, compostable packaging and leftovers could be disposed of together in a food waste bin for collection and treatment.

Destined for the compost pile

Certain items regularly end up in home compost, or organic waste collection, despite containing conventional, non-compostable plastic. Such items include tea bags, which many consumers incorrectly assume to be entirely compostable, and fruit and vegetable stickers that are often disposed of alongside fruit and vegetable peelings. 

In these instances, where conventional plastics regularly end up in organic waste, it makes sense to switch to compostable alternatives to improve the quality of the final compost. 

WRAP highlights teabags as one of the only areas where compostable plastic packaging should always be used in place of traditional plastics because they are regularly placed within the organic waste collection. 

Get the labeling right

Ensuring consumer awareness of correct disposal methods is of the utmost importance when considering the use of compostable plastic solutions. Manufacturers using compostable plastics should ensure that all items are clearly labelled to avoid the risk of compostable materials being disposed of inappropriately and contaminating the environment or conventional plastic recycling systems. 

Considerations should bear in mind the differences in regional recycling systems – for example, when using industrially compostable materials, brands should advise how to dispose of an item in the absence of an industrial composting facility. 

WRAP advises that manufacturers consider labelling that informs consumers how items should be disposed of, rather than using statements, such as ‘100% compostable’, without disposal information. 

Where on-pack space is at a premium, information could be included within a 2D code, such as a QR or Data Matrix code, to provide easily accessible information to consumers via a smartphone or tablet. The advantage of using a 2D code for applications such as this is that a brand is not limited in the amount of information it can provide. 

Standards such as GS1 Digital Link could be utilised to identify a consumer’s location and provide personalised information based on their regional recycling capabilities – potentially even linking to the nearest available recycling point. 

In addition, brands can use product coding and marking to assist in the identification of packaging types at recycling centres and allow for the removal of compostable material that has ended up in plastic recycling. Projects supporting such initiatives include Holy Grail 2.0, which utilizes digital watermarking for product identification.

Word of caution

Compostable materials are an exciting new development in the packaging market. However, as with any switch in materials, the use of compostable plastic packaging requires careful consideration. In addition, any brand considering a switch in packaging solutions should enlist responsible and experienced supply chain and manufacturing partners to minimize the risk of change. 

All brands should partner with an experienced coding and marking provider who can support sustainability design with coding solutions for compostable plastics, advise on appropriate labeling choices, and help ensure products will be accepted by retailers, valued by consumers, and trusted by everyone with an environmental concern.