A new soil incubation study from China's Loess Plateau finds that biodegradable PLA microplastics can sharply increase greenhouse gas emissions from orchard soil. Over 60 days, PLA boosted cumulative CO2 emissions by 190.7% and nitrous oxide by 12.3% compared to untreated soil, while conventional polyethylene and PET actually suppressed those emissions. The likely cause is microbes feeding on the degradable polymer and accelerating soil respiration. The finding complicates the case for replacing conventional mulch films with biodegradable alternatives. PLA reduces long-term plastic pollution but may trade it for a near-term climate impact. The authors stress that neither outcome is desirable, and the lab results need field validation before policy shifts. Anyone working on agricultural carbon budgets or bioplastics regulation should watch for follow-up trials.
