Bioplastics are often marketed as environmentally friendly alternatives to traditional petroleum-based plastics, but recent research challenges this assumption.
A study published in Environmental Science and Technology (November 5) has found that certain bioplastic fibres may be more toxic to soil organisms than conventional synthetic plastics.
These findings call for more comprehensive testing before bioplastics are promoted as safe alternatives.
The Research
The study, led by Dr. Winnie Courtene-Jones from Bangor University, focused on the effects of three types of fibres—conventional polyester and two bio-based fibres, viscose and lyocell—on earthworms.
Earthworms were chosen for the study because of their crucial role in soil health, including aerating the soil, decomposing organic matter, and improving nutrient cycling.
Results revealed alarming toxicity levels:
- After three days, 30% of the earthworms exposed to polyester fibres died.
- The mortality rate increased to 60% for viscose and 80% for lyocell.
Moreover, the study found that long-term exposure to the bioplastic fibres impaired earthworm fertility. This raises concerns about the broader ecological impact on other soil-dwelling organisms, which are vital to maintaining healthy ecosystems.
What Makes Bioplastics Toxic?
Bioplastics, derived from plant-based materials such as cellulose, are often assumed to be safer due to their natural origins. However, the study suggests that the structural or chemical properties of these materials may be inherently toxic.
For example:
- Viscose and lyocell, commonly used in textiles and "natural" fabrics, can leach harmful substances into the soil.
- Bioplastics often require specific conditions, such as high heat, to degrade fully. In real-world settings, they may persist in the environment, breaking down into microplastics or releasing toxic additives.
Toxic Leaching: What Are Viscose and Lyocell?
- Viscose and lyocell are bio-based fibres made from cellulose, a natural polymer found in plant materials like wood pulp. While they are marketed as “natural” and eco-friendly alternatives to synthetic fibres, their production processes and environmental impacts tell a more complex story.
What Are They Made Of?
- Viscose: Also known as rayon, viscose is produced by chemically processing wood pulp. The manufacturing process often involves carbon disulfide, a toxic chemical that poses risks to both workers and the environment. While the end-product is primarily cellulose, residual chemicals can leach from the fibres into the soil, especially when exposed to moisture and microbial activity.
- Lyocell: A newer generation of cellulose-based fibre, lyocell is made using a slightly more sustainable process. It employs a closed-loop system where the chemical solvent (typically N-Methyl morpholine N-oxide) is largely recycled. However, traces of this solvent may remain in the fibres and can potentially leach harmful substances into the environment over time.
How Do They Impact the Soil?
When viscose and lyocell fibres degrade in soil, they may release:
- Chemical Residues: Residual processing chemicals, such as carbon disulfide from viscose or N-Methyl morpholine N-oxide from lyocell, can be toxic to soil organisms, including earthworms and beneficial microbes.
- Microplastic-Like Fragments: Although cellulose is biodegradable, the structural modifications made during manufacturing can make these fibres resistant to natural decomposition in typical soil conditions. This leads to the accumulation of microscopic fragments that interfere with soil health.
- These fibres, often found in clothing, wet wipes, and other products, may initially seem like sustainable alternatives to petroleum-based plastics. However, their ability to leach toxins and persist in soil ecosystems raises significant environmental concerns.
These findings align with previous studies indicating that biodegradable plastics are not a one-size-fits-all solution to plastic pollution.
A Widening Environmental Impact
The issue extends beyond bioplastics used in packaging. Bio-based fibres like viscose and lyocell are prevalent in fast fashion, wet wipes, and other consumer products. During washing, these materials shed fibres that can enter wastewater systems. Sewage sludge, often applied to agricultural land as a fertiliser, directly introduces these fibres into soil ecosystems.
With more than 320,000 metric tons of bio-based fibres produced by the textile industry in 2022, their environmental footprint is significant—and expected to grow.
Implications for Global Plastic Policies
These findings come at a critical time. The United Nations is convening in South Korea, December 2024, for the final meeting of its global treaty negotiations to end plastic pollution.
Learn more about the UN treaty process. Experts like Dr. Bethanie Carney Almroth, an ecotoxicologist at the University of Gothenburg, urge caution in replacing petroleum-based plastics with bioplastics without thorough safety evaluations.
What Can Be Done?
- Rethink Bioplastics: Policymakers and manufacturers must demand comprehensive toxicity testing before introducing bio-based alternatives as environmentally friendly solutions.
- Support Research: More studies are needed to understand the long-term impacts of bioplastics on soil ecosystems and human health.
- Promote Soil Health: Products like Earthfood’s living microbes focus on building robust, resilient soil ecosystems without introducing harmful additives. Learn more about natural soil solutions here.
This research underscores the complexity of addressing plastic pollution. Simply switching from petroleum-based to bio-based plastics is not a guaranteed solution. Instead, a more nuanced approach, considering the full life cycle and ecological impacts of materials, is essential.
For updates on sustainable practices and products that enhance soil health naturally better, Earthfood, and socials: @yourearthfood
SOURCES:
https://en.wikipedia.org/wiki/Global_plastic_pollution_treaty
https://www.un.org/en/climatechange/nations-agree-end-plastic-pollution
https://www.mdpi.com/2313-4321/6/4/81
https://www.undp.org/blog/global-treaty-end-plastic-pollution-sight
https://link.springer.com/article/10.1007/s44169-023-00057-7
https://www.thenewlede.org/2024/11/bioplastics-may-be-toxic-to-soil-organisms/