Are we ready for the biodegradable packaging?

Key information

Project title: Biodegradable nanocomposite packaging materials
Project in the Spotlight: A17020
Market: Packaging

Written by M2i Program Manager: Yulia Fischer

Introduction
Plastics are essential for food packaging due to their excellent mouldability, durability, price, and strength in combination with light weight. However, emissions related to plastic production and plastic pollution that negatively affect health and the environment cannot be ignored. Bioplastics are promising alternatives because of their low footprint and favorable end of life options compared to their fossil-based counterparts.

Problem statement
For fully biobased systems, the current knowledge of nanocomposite systems is mainly of phenological nature rather than understanding the mechanisms behind the induced changes. Nanocomposite design mostly relies on trial-and-error approaches, biobased nanoparticles such as chitin or cellulose nanocrystals, are often less defined and therefore less tested as their inorganic counterparts. In the last decade, great advances have been made in understanding nanocomposite systems, leading to the conclusion that the structure and dynamics of the interphasial layer are crucial for bulk-scale material properties. In this project an interwoven effort between nanocomposite understanding and engineering was applied to improve properties of the biodegradable composites.

Project highlights
In brief, the project addressed the following research topics:

Design of bio-nanocomposites. The addition of (bio-)nanoparticles to biobased polymers leads to preferable properties for food packaging applications like enhanced mechanical, thermal, and barrier properties, while fitting well with the idea of a circular economy. This project has shown how nanocomposites can be effectively designed by nanoparticle/polymer selection and their potential (surface) modification. Within this project the potential of polylactic acid (PLA) with the addition of chitin nanocrystals was studied to create biodegradable nanocomposite materials. PLA was selected because of its biobased nature, recyclability/compostability, as well as its commercial availability at a competitive price level, while chitin was selected because of its abundant prevalence in nature, and availability through the waste streams of the fishing industry.

Figure 1: Overview of the various scales and driving forces affecting the formation of nano-composite plastic materials

The molecular dynamics simulations were used to investigate the effect of nanoparticle – polymer interactions on nanoparticle dispersion. The polymer dynamics close to the surface of the nanoparticles was explored using a relatively unexplored method, laser speckle imaging (LSI). It has been found that nano- and bulk scale dynamics were practically independent of the enthalpic component. These results thus lead to thought-provoking indications that dispersion is more important than nanoparticle – polymer interactions, whereas usually the latter is considered leading in nanocomposite design and manufacture.

Positive effect of biobased fillers. The positive impact of biobased fillers was demonstrated on the example of chitin nanocrystals on the properties of bioplastics like PLA. By addition of fatty acid, the dispersibility of chitin nanocrystals in PLA has been significantly improved. The extent of hydrophobicity change depended on the chain length of the fatty acid, which implies that modification can be easily tailored to the (bio)polymer of choice. Additionally, the chitin nanocrystals provided UV protection and enhanced barrier properties to the nanocomposites, while maintaining their mechanical strength.

Besides enhancing the physical properties of the polymer, low amounts of chitin nanocrystal in the nanocomposite (1–5 wt.%) already provide antioxidant activity, which could be further boosted when the chitin nanoparticles were placed on top of the film instead of inside. This finding is particularly significant in the context of food packaging applications, as this activity can extend the shelf life of food products prone to oxidation.

Figure 2: Chitin nanocrystals modified with fatty acids (top) improve dispersibility of chitin nanocrystals resulting in a more transparent film (right) compared to unmodified chitin nanocrystal addition (left) [4].

The two critical for bio-nanocomposites application aspects, particle migration from these films and biodegradability of chitin materials and polylactic acid, both individually and when combined were examined. The results reveal that the overall migration of the designed bio-nanocomposites in various food simulants remained well below the legal limit of 60 mg/kg. Chitin nanocrystals showed high biodegradability (~ 95% within 28 days), and their incorporation did not affect the biodegradability of polylactic acid. These are important prerequisites that need to be met before considering application in food.

Circular economy potential. The suitability of novel bio-nanocomposites as green materials within a circular economy has been explored. A life cycle assessment was carried out using various environmental impacts, and compared to PLA and PET, a widely used fossil-fuel based plastic. The production of chitin nanocrystals from shrimp shell waste and overall impacts of the production and disposal processes of bio-nanocomposites and the base polymers were taken into account. Polylactic acid outperforms polyethylene terephthalate in terms of many impact indicators, while the environmental impact of bio-nanocomposites as currently produced exceeds that of both base polymers. Chitin nanocrystal production turned out as having a relatively high environmental impact because the supply chain for bio-nanocomposites is not established. This fact makes it almost impossible to have a clear comparison of the environmental impact for the chitin-PLA bio-nanocomposites and the PET.

In this context, a pivotal aspect of future research involves upscaling chitin nanocrystal production, particularly from seafood industry waste. The focus should extend beyond technical advancements, incorporating emerging biological purification techniques and eco-friendly purification processes. At the core of all these activities should lay enhanced sustainability of the entire production, and user chain. Despite the numerous advantages and technological features of bio-nanocomposites highlighted in the study, their potential as sustainable alternatives to conventional plastics hinges on widespread consumer acceptance. Therefore, pre-market testing of bio-nanocomposites with consumers is essential to ensure their successful integration into society and to bridge the gap

Overall, plastics play an important role in the transition from a linear economy toward a circular one, but ideas about this role differ among actors. Academic papers focus mainly on alternative forms of plastics, whereas newspapers mainly report on closing the loop for traditional forms of plastics. A combination of both visions is a missed opportunity to date. The further development of this future vision of recyclable bioplastics and biodegradable plastics by industry, academics, governments, and NGOs, including citizens, may contribute to a more fully circular biobased plastics economy. Before novel materials – such as bio-nanocomposites – can successfully be introduced into society, other factors should be investigated as well including scalability, accessibility, end-of-life possibilities, sustainability, toxicology, and consumer acceptance and handling.

The consortium
Divers group of companies contributed to the project A17020, among others Heineken, Oerlemans Packaging, Jacobs Douwe Egberts, Avery Dennison, Ardagh Group, Koninklijke Peijnenburg and Yparex. The project produced 12 articles and 2 defended PhD theses: Ivanna Colijn (PhD cum laude, now Packaging Sustainability Expert with FrieslandCampina) and Murat Yanat (now Assistant Professor with Akdeniz University). The work presented at national and international conferences four times won the price for the best poster.

Project leader and daily supervisor Karin Molenveld and Karin Schoen (WU) see the project a great success: “We could work in a curiosity driven way within the boundaries of the project. We have been able to (re)define the playing field for nano-composite design for food applications, and feel that the insights generated will be instrumental in pushing application of nanocomposites, also in other fields, far beyond the current state of affairs”.

Erik Bijleveld (Yparex) stated: “we are very happy with the project results, however for the way-forward the industrial circularity vision needs to be established: biodegradability or reusability of packaging materials should be the focus of further development.