Rice chaff, sawdust, and rape straw are commonly used as padding materials in the ectopic fermentation system. However, the characteristics of greenhouse gas emissions the ectopic fermentation system using rice chaff, sawdust, as well as the effects of rape straw on these emissions, remain unclear. This study investigated the effects of different proportions of rape straw (0, 10 %, 25 %, and 50 %) on greenhouse gas emission characteristics in this system. The experimental results indicated that the treatment group containing rice chaff, sawdust, and more than 25 % rape straw significantly increased fermentation temperature, prolonged the thermophilic phase, enhanced the maturity of fermentation products, and altered microbial community structures compared to the control group with only rice chaff and sawdust. Redundancy analysis revealed that replacing rice chaff and sawdust with 50 % rape straw significantly decreased the relative abundance of methanogens (e.g., Methanospirillum and Methanobacterium) and denitrifying species (e.g., Denitrificimonas caeni and Aliarcobacter butzleri), resulting in reductions in cumulative emissions of CH4 and N2O by up to 44.6 % and 84.9 %, respectively, compared to the treatment group with rice chaff and sawdust alone. The absolute abundance of the nosZ gene was positively correlated with N2O emissions. Therefore, rape straw has been demonstrated to be an effective padding material that reduces CH4 and N2O emissions while enhancing the maturity of fermentation products in the ectopic fermentation system.
