Bio-based alternatives to plastic could threaten natural environment, warns UK study

Bio-based fiber packaging could pose an unexpected threat to the natural environment, suggests a new study conducted at the UK’s Bangor University and University of Plymouth. The research team calls for novel bio-based plastic alternatives to be studied more extensively, with the new findings indicating threats to animal and soil health.

“This study aimed to compare the effect of viscose and lyocell, two bio-based fibers, and the conventional fiber polyester on earthworms,” Dr. Winnie Courtene-Jones, lead author of the new study and a lecturer in marine pollution at Bangor University, tells Packaging Insights.

“It showed that at high concentrations of fibers, lyocell and viscose induced a greater maximum mortality of earthworms than polyester.” 

These findings suggested that while bio-based fiber alternatives to plastic are often touted as inherently environmentally friendly, this might be an example of the “green halo” effect. 

The surprising significance of earthworms

Courtene-Jones explains that the test methods used in this study, published in Environmental Science & Technology, followed the Organisation for Economic Cooperation and Development’s standardized test methods for earthworms. 

The research team examined the lethal thresholds and sublethal toxicity of bio-based viscose and lyocell and compared them to petrochemical-based polyester fibers on Esenia fetida earthworms, described as “key ecosystem engineers.”

“A second test, using environmentally relevant concentrations of the fibers, indicated that earthworms in soils containing viscose fibers exhibited reduced reproduction compared to those exposed to polyester fibers. And earthworms in soils containing lyocell fibers showed reduced growth and also higher rates of burrowing compared to exposure to the other types of fibers,” she states. 

Earthworms in soils containing viscose fibers exhibited reduced reproduction compared to those exposed to polyester.“The fibers were chemically characterized, and these techniques did not detect any additives, which could have influenced toxicity. Therefore, it is likely the particles and aspects of their physical and inherent structural properties, which influenced the toxicity observed.”

The research lead explains that her findings could have broad consequences due to the importance of the earth-dwelling animals. “Earthworms are widely used in toxicity assessments such as this. They are also critical to the functioning of soils globally. Therefore, if the population of earthworms is altered due to exposure to fibers, there could be wider implications on soil health more broadly.” 

“It is reasonable to assume that other organisms may also display adverse effects following exposure to bio-based and conventional microfibres, as evidenced by other scientific studies.”

Net environmental impact

The study highlights the importance of detailed testing for any novel material introduced to the packaging industry.

“The safety of materials, but also other factors such as its sustainability throughout the life cycle from the extraction of the feedstock, through the production process, transportation, use and at end of life, must also be considered,” continues Courtene-Jones.

“It is not simply a case of switching one material for another, but evaluating where the use of a plastic (fossil-based or bio-based) is essential, designing for circularity and providing information on the composition, safety and sustainability of that material or product.”

She points out that previously conducted studies have examined the effects of microplastics and microfibres (fossil and bio-based) on soil health and functioning and found “changes to water retention and soil stability,” among other issues.

Experts have also questioned the extent to which novel packaging materials advertised as biodegradable actually break down in an open environment.