Industrially compostable plastics can play an essential role in putting the envisioned circular economy into practice.
They have the unique potential to promote and increase the separate collection of biowaste. The more biowaste is being collected separately, the more is not only diverted from incineration but also from mechanical plastic recycling streams to organic recycling, hence reducing contamination of waste and recycling streams.
However, there is a widespread misconception about compostable plastics and their allegedly negative impact on mechanical recycling streams.
It’s important to note that currently, only a limited number of plastics are sorted for recycling, which are generally those with the highest market shares, such as PET, PP, PE, and sometimes PS. However, other types of polymers are entering sorting facilities, which due to low volumes, will not be recycled and must be sorted out. This means that potential cross-contamination of recycling streams is an issue that involves all kinds of plastics and materials, not just compostable plastics specifically.
Fortunately, existing sorting technologies, such as density separation and NIR (near-infrared) sorting, can efficiently separate and sort different kinds of polymers, including compostable plastics. Compostable plastics are mainly polyesters that have very different densities and very distinctive NIR-spectra compared to polyolefins, PET and PS. Numerous studies have shown that sorting of compostable plastics is effective, and that, after sorting, the contamination rate in an established recycling stream is usually very low (below 1%).
In fact, Italy, which has the highest number of compostable packaging on the market in the EU, reports misthrow rates of compostable plastic products in conventional packaging waste streams below 4% before sorting and a contamination rate of less than 0.8% after sorting.
It’s also important to note that there is no negative impact of possibly remaining impurities of compostable plastics on existing recycling streams. Even if compostable plastics accidentally end up in other plastic waste streams, current and foreseeable market volumes are so low that after sorting, any remaining contamination will be negligible and the potential impact insignificant.
Compostable plastic applications are designed for organic recycling.
Certified compostable products should be collected with biowaste and then treated in industrial composting and/or anaerobic digestion facilities. All compostable plastic products should display clear labeling to avoid misthrows and ensure separate collection in the dedicated waste stream. Applicable standards and related certification marks are available for industrial and home compostability.