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Differential effects of sulfide-induced transformation of biodegradable and conventional microplastics on sedimentary CO2 and CH4 emissions: Underlying microbiome-mediated mechanisms
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Microplastics buried in sediments don't just sit inert — they interact with soil microbes in ways that affect how much methane and CO2 the sediment releases into the atmosphere. This incubation study found that fresh biodegradable plastic (PLA) dramatically increased greenhouse gas emissions, but once the plastic had aged through a chemical process called sulfidation, it actually suppressed them — while conventionally aged polyethylene had the opposite effect, boosting methane by stimulating methane-producing microbes. The findings complicate the assumption that biodegradable plastics are automatically better for the environment, and suggest that how plastics age underground matters as much as what they are made of.
The accumulation of microplastics (MPs) in sediments presents serious ecological risks. Although sulfidation is a key aging process in anoxic environments, its impact on sedimentary CO and CH emissions and underlying microbiome-mediated mechanisms remains unclear, particularly for biodegradable versus conventional MPs. Sediment incubation experiments with pristine and sulfidation-aged polyethylene (PE) and polylactic acid (PLA) revealed distinct carbon-related greenhouse gases patterns driven by material-specific microbial responses. Compared to controls, pristine PLA significantly enhanced cumulative CO and CH emissions by 4.47- and 2.59-fold, respectively, accelerating the CH emission peak due to its rapid carbon release. Conversely, sulfidation-aged PLA (PLA-S) reversed this trend, reducing CO emissions by 61.5%. This suppression was linked to an enriched microbiome (e.g., Acidobacteriota, ester-hydrolyzing Myxococcota) adapted to acidic stress, nitrogen fixation, and pathogenicity, likely diverted carbon flows. In contrast, sulfidation-aged PE (PE-S) exhibited surface oxidation, which led to a 36.7% increase in CH emissions, along with higher dissolved organic carbon (DOC) and microbial metabolic quotient (qCO). This shift correlated with the enrichment of alkane-degrading Methylomirabilota and Bacillota, potentially converting plastic-derived carbon into methane. These findings emphasize the necessity of considering MPs' natural aging (e.g., sulfidation) and material types (degradable vs. conventional) when assessing their ecological risks and roles in CO and CH emissions, revealing key microbiome mechanisms linking MPs to the global carbon cycle.
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Comparison of sulfide-induced transformation of biodegradable and conventional microplastics: Mechanism and environmental fate
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Researchers compared how sulfide chemicals in oxygen-free environments (like deep sediments) transform biodegradable plastics versus conventional plastics. They found that biodegradable PBAT microplastics were more easily changed by sulfides than conventional polyethylene, releasing more dissolved organic carbon and potentially different environmental effects. This suggests that so-called biodegradable plastics may not behave as safely as expected when they break down in certain natural environments.
Biodegradable and conventional microplastics differentially affected greenhouse gas emissions from a flooded paddy soil: Insight into metagenomic analysis
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Not all plastics behave the same way once they end up in the environment: this study found that "biodegradable" plastic (PLA) actually increased methane emissions from flooded rice fields by over 260%, while conventional plastics (PE, PET) suppressed methane but boosted nitrous oxide, another potent greenhouse gas. This matters because biodegradable plastics are often marketed as the eco-friendly choice, but this research shows they may worsen climate-warming gas emissions from farmland, at least in the short term, a tradeoff worth understanding as these plastics become more common in agriculture.
Microplastics trigger sediment organic carbon pools stabilization pathways: Evidence from microbial mediated DOM turnover
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Lab sediment mixed with two types of plastic (polyethylene and polylactic acid) for 100 days released more carbon dioxide and methane and changed the sediment's dissolved organic matter and microbial communities. Aged polylactic acid caused the biggest changes, increasing sediment oxidation and altering bacterial, fungal and archaeal community networks involved in carbon breakdown.
Metagenomic Insights into the Microbial Regulation of Soil Organic Carbon Dynamics Under Microplastic Exposure in Saline-Alkali Soils
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Scientists found that "biodegradable" plastic (PLA) doesn't just disappear harmlessly in salty farmland soils, it actually changes soil microbes' behavior and boosts carbon storage more than regular plastic (PE) does. This matters because these soils are used to grow food worldwide, and understanding how different plastics affect soil health can help us make smarter choices about "eco-friendly" plastic products before they become widespread in agriculture.
Effect of microplastics on sulfate reduction in landfill leachate-saturated zone
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Researchers investigated how different types of microplastics affect sulfate reduction in landfill leachate-saturated zones at varying temperatures. They found that polylactic acid microplastics dramatically increased hydrogen sulfide release compared to polystyrene, polyethylene, and PVC, with cumulative release at 55 degrees Celsius being 33 times higher than at 25 degrees. The study suggests that biodegradable plastics in landfills may paradoxically worsen certain pollution processes by enriching sulfate-reducing microbial communities.
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