Microplastics are infiltrating Australian farmland every year through compost, according to a recent study by researchers at Griffith University.
Invisible Pollution How Microplastics Are Quietly Contaminating Australia’s Farmland
The study, which analyzed compost samples from 11 facilities in Victoria, found that every kilogram of compost contains between 1,500 and 16,000 microplastic particles, weighing anywhere from 7 to 760 milligrams per kilogram. Since about 26% of compost produced in Australia is used in agriculture, researchers estimate that between 2.7 and 206 tonnes of microplastics are being spread across farmland annually.
The source of these plastics is the organic waste itself. Many Australian municipalities provide households with compostable bags to collect food scraps, but not all of these materials break down completely. Some contain fossil fuel-based components or bioplastics that require very specific conditions to degrade fully. The study found that many so-called compostable bags break down into microplastics instead of decomposing entirely. Beyond these, other sources of plastic contamination include packaging materials, plastic containers, plant ties, and synthetic fibers that end up mixed in with garden waste.
Once in the soil, microplastics accumulate and don’t simply disappear. They can alter the structure of the soil, making it less fertile and disrupting plant growth. Over time, they can degrade into even smaller nanoplastics, which are tiny enough to be absorbed by plant roots. These particles then move into stems, leaves, and fruits, meaning they could ultimately end up in the food we eat. While international studies have already raised concerns about microplastics in compost, this Australian research reveals the problem is likely even more widespread than previously thought.
Despite composting being promoted as an environmentally friendly alternative to landfill, there are currently no national standards in Australia regulating the presence of microplastics in compost. Policies like the National Plastic Plan encourage composting but fail to address the risks posed by plastic contaminants. The researchers behind this study warn that without urgent action, composting could become an environmental hazard rather than a solution.
To tackle this issue, they suggest stricter regulations on microplastic content in compost, improved quality control for compostable bags, better oversight of waste processing facilities, and further research into the long-term effects of microplastics on soil fertility and food safety. Without these measures, compost could become yet another silent pathway for plastic pollution, infiltrating ecosystems and potentially impacting human health in ways we are only beginning to understand.
Invisible Pollution How Microplastics Are Quietly Contaminating Australia’s Farmland