Compostable plastics in soil cut a potent greenhouse gas, unlike regular plastic
Zhang H, Li X, Zhu M, Wang R, Zhang J
Soil Health
The plastic mulch or biodegradable pots you use in your garden bed actually change how much nitrous oxide, a greenhouse gas nearly 300 times stronger than CO2, escapes from your soil depending on what they're made of.
Scientists buried two kinds of plastic bits in soil: compostable ones and regular durable ones. The compostable plastic broke down and gave soil microbes a burst of easy food, which helped them fully finish the job of clearing excess nitrogen from the soil as harmless nitrogen gas. Regular plastic didn't feed the microbes the same way, so the process got stuck halfway and released more nitrous oxide, a gas that traps far more heat than carbon dioxide.
Key Findings
Biodegradable microplastic-amended soils had the highest N2 emission rate (3.9 μg N/kg soil/hr), while conventional microplastics produced higher N2O emissions (0.46 μg N/kg soil/hr).
Biodegradable microplastics upregulated key denitrifying genes (nirK, nirS, nosZI, nosZII), enabling more complete denitrification and a lower N2O-to-(N2O+N2) ratio despite higher total gas flux.
A global meta-analysis of 162 pairwise observations confirmed microplastics generally raise soil N2O emissions, with effects diverging by plastic type and soil moisture; biodegradable plastics raised N2O risk specifically in wet, high-moisture soils.
chevron_right Technical Summary
Compostable plastics in soil break down and feed microbes, which helps them fully convert nitrogen pollution into harmless gas, while conventional plastics leave nitrogen stuck as N2O, a greenhouse gas far more potent than CO2.
Abstract Preview
Original paper
Divergent effects of biodegradable and conventional microplastics on denitrification in soils: Mechanisms governing N₂O emission and product stoichiometry.
Microplastics (MPs) are increasingly prevalent in agroecosystems, yet their impacts on soil denitrification rate and nitrous oxide (N2O) emissions remain poorly understood, particularly regarding h...
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