Microplastics threaten the effectiveness of earthworm-produced biofertilisers
A new study reveals that microplastics not only harm earthworms, but also diminish the quality of the fertilisers they produce.
We seek to enhance the ability of earthworms to digest microplastics, turning vermicomposting into a cleaning process, without affecting the quality of the compost and thus the quality of the crops.
A recent study carried out as part of the Recover project, led by the University of Almeria, has revealed that microplastics compromise the effectiveness of biofertilisers produced by earthworms. These pollutants not only endanger the health of these vital species, but also reduce the nutrient content of the fertilisers they generate.
Since ancient times, as documented by Pliny the Elder, earthworms have been recognised for their ability to improve soil quality through the process of vermicomposting. However, the recent incorporation of microplastics into agricultural soils has posed new challenges.
In addition to the direct effects on earthworms, microplastics pose a threat to agricultural ecosystems and the food produced in these soils. Although it is known that certain microorganisms, such as fungi and bacteria, can degrade these contaminants over time, there are still concerns about how microplastics accumulate in animal tissues and their potential harmful effects.
This study reinforces the need to develop sustainable solutions for waste management and to improve agricultural practices to preserve soil health and compost quality. With these findings, the RECOVER project team lays the foundation for future research aimed at enhancing the ability of earthworms to remove microplastics from the environment, contributing to agricultural sustainability.
The research, led by Spanish project partners Miguel Hernández University of Elche (Alicante) and the University of Almeria, has focused on the effects of microplastics, mesoplastics and nanoplastics, which range in size from the tip of a hair to the size of a bacterium. These microplastics damage crucial systems in the worms, such as neurons and gut microbiota. As the worms ingest these contaminants, their ability to produce nutrient-rich biofertilisers, essential for plant health, is compromised.
María José López, a researcher at the University of Almería, says: “This study is an initial step which is being complemented by the identification of the microorganisms in the gut of the earthworms that can biodegrade microplastics and studying how we could strengthen them. In this way, we hope that in the future, earthworms will be able to eliminate these pollutants and continue to produce nutritious compost”.
This finding is therefore a very important step towards identifying which microorganisms are involved in biodegrading microplastics and establishing whether we can enhance them so that, in the future, earthworms will be able to remove them from the substrate and produce nutrient-rich compost at the same time.
Scientists have focused on earthworm humus, an organic fertiliser resulting from the digestion of organic matter by earthworms. This biofertiliser, which is highly valued in agriculture and gardening, not only nourishes but also strengthens plants against diseases and promotes the activity of beneficial microorganisms in the soil.
The study, entitled ‘Effect of agricultural microplastic and mesoplastic in the vermicomposting process: Response of Eisenia fetida and quality of the vermicomposts obtained’, analysed five varieties of plastic and their impact on earthworms. For 45 days, the experts studied the worms in three different scenarios, varying the presence of microplastics and organic matter.
The conclusions of the study are worrying. The worms experienced weight loss and accentuated oxidative damage, resulting in their eventual death. In addition, the biofertiliser they produced was deficient in essential nutrients such as phosphorus, potassium and nitrogen. Hence, the Recover project seeks to enhance the worms’ ability to digest microplastics, turning vermicomposting into a cleaning process, without affecting the quality of the compost and thus of the crops.