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.