Biodegradable microplastics and biochar team up to curb cadmium in crops
image: Biodegradable microplastics coupled with biochar enhance Cd chelation and reduce Cd accumulation in Chinese cabbage
Credit: Meng Zhao, Guoyuan Zou, Yifan Li, Bo Pan, Xuexia Wang, Jiajia Zhang, Li Xu, Congping Li & Yanhua Chen
A new study reveals that combining biodegradable microplastics with biochar may offer an unexpected solution to one of agriculture’s most persistent problems: toxic metal contamination in food crops.
Cadmium, a heavy metal commonly found in polluted soils, can accumulate in vegetables and pose serious risks to human health. Now, researchers report that pairing biochar with polylactic acid microplastics significantly reduces cadmium uptake in Chinese cabbage, a widely consumed leafy vegetable.
“This work shows that materials often seen as pollutants can actually play a beneficial role when carefully managed,” said one of the study’s authors. “By combining biodegradable microplastics with biochar, we can enhance natural soil processes that lock up cadmium and prevent it from entering the food chain.”
Biochar, a carbon-rich material produced by heating biomass in low-oxygen conditions, has long been studied for its ability to trap heavy metals in soil. It works by binding metals such as cadmium through surface functional groups and porous structures. However, its performance can vary depending on soil conditions and biological activity.
Microplastics, on the other hand, are typically viewed as emerging environmental contaminants. In agricultural soils, they originate from plastic mulch and other sources and are known to influence soil chemistry and microbial communities. Their role in heavy metal behavior has remained unclear.
To explore this interaction, the research team conducted greenhouse experiments using cadmium-contaminated soil and Chinese cabbage. They tested three types of biochar derived from agricultural waste and combined them with biodegradable polylactic acid microplastics.
The results were striking. While biochar alone reduced cadmium accumulation in plants, the addition of biodegradable microplastics further enhanced this effect. In some treatments, cadmium levels in plant tissues dropped by up to 42 percent. The most effective combination, based on sugarcane bagasse biochar, reduced cadmium in roots and shoots by 47 percent and 22 percent compared to biochar alone.
Interestingly, the microplastics slightly suppressed plant growth by altering nutrient availability in soil. However, they also increased soil organic matter, dissolved organic carbon, and nitrogen levels, which played a key role in reducing cadmium uptake.
Further analysis revealed why. The combined treatment reshaped the chemical environment around plant roots, known as the rhizosphere. It stimulated the production of organic compounds such as amino acids and carboxylic acids that can bind cadmium and render it less available to plants. At the same time, it promoted beneficial microbial communities involved in carbon and nitrogen cycling, which further enhanced metal immobilization.
Rather than simply reducing the amount of available cadmium in soil, the system worked by strengthening natural chelation processes. These processes trap cadmium in stable forms that plants cannot easily absorb.
The findings highlight a complex but promising interaction between emerging pollutants and engineered soil amendments. They also suggest a new direction for managing contaminated farmland using low-cost, carbon-based materials derived from agricultural waste.
The researchers caution that more work is needed to assess long-term impacts and to test different types and concentrations of microplastics under field conditions. Still, the study provides important insights into how soil chemistry, microbes, and engineered materials can work together to reduce food safety risks.
As concerns about both microplastics and heavy metals continue to grow, this research points to an unexpected opportunity: turning two environmental challenges into a combined solution.
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Journal Reference: Zhao, M., Zou, G., Li, Y. et al. Biodegradable microplastics coupled with biochar enhance Cd chelation and reduce Cd accumulation in Chinese cabbage. Biochar 7, 31 (2025).
https://doi.org/10.1007/s42773-024-00418-y
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About Biochar
Biochar (e-ISSN: 2524-7867) is the first journal dedicated exclusively to biochar research, spanning agronomy, environmental science, and materials science. It publishes original studies on biochar production, processing, and applications—such as bioenergy, environmental remediation, soil enhancement, climate mitigation, water treatment, and sustainability analysis. The journal serves as an innovative and professional platform for global researchers to share advances in this rapidly expanding field.