Autoclaved lightweight aerated concrete suppressed N2O and CO2 emissions from paddy soil

Autoclaved lightweight aerated concrete (AAC), a construction waste that is utilized as a soil amendment, can influence terrestrial carbon dioxide (CO₂) emissions. Still, no evidence exists regarding its impact on the emission of nitrous oxide (N₂O), which has a higher global warming potential. This study examined effects of AAC on CO₂ and N₂O emissions from paddy soil under compacted and non-compacted conditions, under 60% and 100% water-holding capacity (WHC). Samples were incubated in glass vials (25°C) for 21 days. Emissions of CO₂ and N₂O were measured on days 0, 1, 3, 7, 14, and 21 using gas chromatography. The results revealed that AAC significantly (p < 0.05) lowered N₂O emission rate during the whole period of incubation, while it suppressed CO₂ emission rate only at the early stages (∼7 days) of incubation. In compacted soil, the emissions of CO₂ were significantly lower, while N₂O was significantly higher than that in non-compacted soil, showing the influence of soil physical conditions. The emissions of CO₂ and N₂O were significantly lower at 100% WHC than those at 60% WHC. AAC suppressed both CO₂ and N₂O emissions under both compaction and WHC levels. The results confirm that AAC supports suppressing terrestrial emission of both CO₂ and N₂O, indicating that AAC has a potential as a sustainable soil amendment that enhances the climate change resilience.