Are compostable plastic cups actually biodegradable?

When selecting disposable tableware for an event, you may think you are making a more sustainable choice by selecting those labelled “bioplastic” or “compostable”. But are these materials really biodegradable?

A new study by Falzarano et al., investigates the biodegradability of two single-use items, specifically a cup and a plate. These items were certified as compostable (UNI EN 13432:2002), widely commercially available and made from a PLA-based bioplastic.

PLA (polylactic acid) is a biopolymer produced from lactic acid and utilised in making bioplastics. Its biodegradation process is well understood, occurring via first hydrolysis, followed by fragmentation and finally microbial degradation. PLA-degrading bacteria are not commonly found in natural environments, and high temperatures are often needed to promote its biodegradation.

The aim of this study was to investigate if PLA-based bioplastics can be reasonably degraded in the anaerobic digestion process and determine if higher temperatures (thermophilic conditions) were necessary. The authors investigated the anaerobic digestibility of the PLA-based single use items using BPC’s automated instrumentation* to determine the biodegradation rate of the bioplastic items under mesophilic (38°C) conditions.

They found that compared with higher temperatures, biodegradation under mesophilic conditions took longer and was incomplete. Even though anaerobic digestion may be viable waste management option for PLA-based bioplastics, higher temperatures or long digestion times are necessary. This presents a serious issue when co-digestion with food waste or biowaste (typically lower temperatures and shorter digestor times) is needed. Although on paper these materials appear biodegradable, there may be no realistic means to dispose of the products sustainably.

The authors conclude that greater standardisation of bioplastics’ biodegradability is needed. Bioplastic producers and certifying processes should also consider plans for disposal of the “biodegradable” materials.

*The study was carried out using a predecessor to BPC Blue anaerobic. If you’re working with bioplastics like PLA and need a reliable way to assess biodegradability, BPC Blue is made for it. Purpose-built for standardised testing in both research and industry.

Discover more on our product page: https://bpcinstruments.com/bpc-blue/

Read the full paper in Materials here: Anaerobic Biodegradation of Polylactic Acid-Based Items: A Specific Focus on Disposable Tableware Products

About BPC Instruments AB

BPC Instruments is a global, Swedish-based, pioneering technology company developing and offering analytical instruments enabling more efficient, reliable, and higher quality research and analysis for industries in renewable bioenergy and environmental biotechnology. The result is not only higher accuracy and precision, but also a significant reduction in time consumption and labour requirement for performing analysis. BPC Instruments’ innovative products offer high-quality hardware and software based on deep knowledge and experience of target applications. The solutions are the first of their kind, making the company a pioneer in its field. Today, BPC Instruments exports to nearly 80 countries around the world. BPC is listed on the Spotlight Stock Market in Sweden. For more information, please visit BPC’s webpage: www.bpcinstruments.com