February 2019
What products should be made compostable?
Composters do not need compostable packaging to make quality compost, as it doesn’t add value to the final product. This is because compostable packaging provides little to no nutrient value for compost. However, food waste is a rich source of nutrients for compost. So, products and packaging that assist in the diversion of food waste from landfill should be made compostable, e.g. compostable food waste caddy liners. Furthermore, small hard-to-remove items that cause contamination in both commercial and home composting systems should also be made compostable, e.g. fruit stickers, tea and coffee bags, asparagus ties, banana tape. Also, agricultural items that are currently made from conventional plastic, where there is a risk that they will inadvertently remain in the soil after use, 
should also be made compostable, such as mulch film and net vine clips, for example.
New Zealand composters are gravely concerned that a wide range of compostable materials that could devalue compost are appearing on the market. This includes nappies and sanitary products, and containers which contain residues that impact compost quality and value, e.g. containers for janitorial products, cleaners, shampoos and pens, etc.
The issue of contamination:
- Minimising and eliminating contamination is a crucial area of concern for composters. It is currently challenging for both the public and industry to differentiate between some compostable and non-compostable plastic products, due to their similarity in appearance (such as cups made from PLA and cups made from PET). Removing contamination is both expensive and time-consuming.
- Current household collections of food and garden waste are often contaminated with non-compostable items. For example, in green waste bins, plastic bags, plastic plant pots and gardening implements are regularly found. In food waste bins, fruit stickers, plastic bags and other types of packaging are regularly found.
- Composting facilities are not willing to accept compostable packaging in household food waste or green waste collections due to the proven risk of non-compostable packaging being inadvertently included. This is further complicated by the inability to quickly and easily distinguish between compostable and non-compostable packaging, as noted above.
One of these cups is compostable, and one is recyclable – can you tell which is which?
- New Zealand councils have unanimously agreed that until the technology improves to enable non-compostable plastics to be easily identified and removed, current and future council-provided kerbside food and green waste collections will not accept compostable packaging.
- To reduce contamination the supply chain from product manufacturer to a composting facility needs to be carefully controlled. Composters are more likely to consider accepting compostable materials if they are supplied as a sorted stream with contamination removed.
- Compostable packaging may be suitable in the following instances:
- Commercial food waste collections where cafés and restaurants only use compostable serviceware chosen from an approved list of vendors, do not use any plastic serviceware and where the service provider is providing a sorting service.
- Events where manual separation and thorough decontamination of waste takes place.
- Venues or businesses (such as Vector Arena) where only compostable packaging is used and decontamination is undertaken.
- In order for composters to consider taking compostable packaging there needs to be a financial incentive to offset the inconvenience, extra infrastructure and the extra workload required to accept and process these products.
- Some commercial composters would need to apply for a change to their resource consents to process compostable packaging, while others would need to invest in additional processing equipment.
- Lastly, some composters are unable to accept specific types of compostable packaging due to the input requirements for organic certification of the resulting compost. Currently compostable plastics are not an accepted input for organically certified compost.
Organisations who choose to use compostable packaging need to:
- Ensure that packaging meets an international standard for commercial compostability.
- Identify a composting facility that is willing to accept the packaging and ensure that the packaging meets any criteria laid out by the receiving composting facility.
- Ensure that a collection infrastructure exists to collect this packaging.
- Ensure that the compostable packaging is sorted, and any contaminants are removed before transporting it to the composting facility.
Designers of packaging need to be aware that:
- For packaging and serviceware the following hierarchy should be followed:
- Prevention – eliminate any unnecessary packaging where possible
- Reusability – where possible make packaging reusable / resealable/ refillable
- Recycling – where possible make products recyclable using plastics with strong and economic end markets
- Compostable
- A key criterion for acceptance is that a product is certified as commercially compostable. There is currently no New Zealand standard, although a Packaging Forum initiated working group is undertaking research in this area. In the meantime, there are several international standards from Europe, the USA and Australia that are recognised in New Zealand.
- However, it should be noted that some compostable materials that have met the requirements of international standards still cannot be processed in the windrow facilities that are common in New Zealand (fragments of varying sizes remain in the finished compost, due to temperature variation throughout the windrow). Covered windrows and invessel systems where temperatures are more consistent are more likely to process compostable packaging effectively.
- Fibre and paper-based products such as bagasse are more effectively broken down in agitated composting systems such as windrow facilities where materials are turned more frequently, than are compostable plastics.
- Ideally, compostable packaging should not be bright colours, e.g. pink or blue, as this risks the marketability of compost products, if flecks of those colours show up in compost.
- Any product made from compostable plastic that is advertised as commercially or home compostable needs to have the claim substantiated with the composting standard the finished product has met.
- Find which composting facilities in New Zealand accept compostable packaging here.
- Learn more about WasteMINZ compostable packaging projects here.
