Beneficial effect of compost utilization on reducing greenhouse gas emissions in a rice cultivation system through the overall management chain

Highlight• Manure composting and its land application reduced net GWP by 25%. • Impact of greenhouse gas emission from composting process was negligible. • Compost application suppressed CH₄ flux by 58% during rice cultivation. Livestock manure application can stimulate greenhouse gas (GHG) emissions, especially methane (CH₄) in rice paddy. The stabilized organic matter (OM) is recommended to suppress CH₄ emission without counting the additional GHG emission during the composting process. To evaluate the effect of compost utilization on the net global warming potential (GWP) of a rice cropping system, the fluxes of GHGs from composting to land application were calculated by a life cycle assessment (LCA) method. The model framework was composed of GHG fluxes from industrial activities and biogenic GHG fluxes from the composting and rice cultivation processes. Fresh manure emitted 30 Mg CO₂-eq. ha^{− 1}, 90% and 10% of which were contributed by CH₄ and nitrous oxide (N₂O) fluxes, respectively, during rice cultivation. Compost utilization decreased net GWP by 25% over that of the fresh manure during the whole process. The composting process increased the GWP of the industrial processes by 35%, but the 60% reduction in CH₄ emissions from the rice paddy mainly influenced the reduction of GWP during the overall process. Therefore, compost application could be a good management strategy to reduce GHG emissions from rice paddy systems.