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Low-dose polylactic acid microplastics mitigate methane emissions in ratoon rice systems
Summary
Polylactic acid (PLA) is often promoted as a greener alternative to conventional plastic, but this study finds that even low doses of PLA microplastics in rice paddies can significantly reduce methane emissions from the soil — cutting them by 36% over a full growing season. Importantly, this climate benefit came without harming crop yield, increasing CO2 emissions, or raising grain metal concentrations, suggesting PLA may affect soil chemistry in unexpectedly useful ways. The findings open a new line of research into how biodegradable agricultural plastics might be managed not just as a pollution concern but as a potential tool in low-carbon farming strategies.
Biodegradable plastics are increasingly introduced into agricultural systems, yet their ecosystem-scale climate impacts on methane (CH₄) emissions remain poorly understood. Here, we evaluated the effects of environmentally realistic, low-dose polylactic acid (PLA) microplastics on CH₄ emissions and food safety across a full ratoon rice growing cycle. PLA amendment reduced cumulative methane (CH₄) emissions by 36.4% (8.42 ± 0.54 vs. 5.35 ± 0.27 g m⁻²) without affecting CO₂ exchange, crop productivity, or grain metal(loid) concentrations. Temporal analyses revealed that CH₄ dynamics were primarily governed by crop phenology. Process-based modeling evidence indicated that PLA induced persistent soil redox regulation, suppressing methanogenesis while avoiding the typical trade-off between CH₄ mitigations and heavy-metal risks. Moreover, PLA reduced the apparent temperature sensitivity of CH₄ emissions, suggesting enhanced system stability under heat extremes. These findings identify a previously overlooked pathway linking biodegradable material inputs with ecosystem CH₄ regulation and highlight their potential contribution to carbon-neutral agricultural management.