Abstract: Livestock manure management represents a critical source of ammonia (NH₃) and hydrogen sulfide (H₂S) posing significant challenges to air quality and agricultural sustainability. Covering materials serves as an effective approach for mitigating gas emissions during manure storage, yet conventional materials face challenges including inadequate buoyancy, sedimentation susceptibility, and limited adsorption capacity. To address these limitations, this study developed a novel hydrophobic silica-modified expanded vermiculite (MV) for application in swine liquid manure storage system. A systematic evaluation from the benefit of odor reduction and eco-environment was conducted comprising four experimental groups: traditional woodchip cover, unmodified expanded vermiculite (V) cover and MV material at 2 cm and 5 cm thicknesses, alongside an uncovered control. The results of material characterization indicated that the MV surface was coated with fine particles, suggesting that nanoscale hydrophobic silica successfully adhered to the surface of expanded vermiculite. Moreover, MV achieved superior hydrophobicity (water contact angle >102°) and an increased specific surface area (12.34 m²∙g⁻¹, compared to 5.64 m²∙g⁻¹ for unmodified expanded vermiculite), demonstrating that the expanded vermiculite was successfully modified into a composite material with floating properties and higher adsorption capacity. The MV treatment demonstrated remarkable NH₃ emission reduction of 87%~95% (P<0.05) compared to control, and compared with V, the NH₃ reduction efficiency of MV was increased by 57%~93% (P<0.05), though it showed no significant impact on H₂S emissions. Notably, MV preserved ammonium nitrogen content with 23~28% greater efficacy compared to uncovered systems, attributable to its dual-phase gas adsorption and physical barrier mechanisms. From the perspective of the Mantel test, preventing the sinking of covering materials is crucial for controlling NH₃ and H₂S emissions. Due to a good buoyancy, MV can effectively reduce the volatilization of NH₃ and adsorb H₂S through its adsorption effect, avoiding the phenomenon of increased H₂S emissions caused by traditional covering materials. In contrast, V and traditional woodchip cover are prone to sinking, failing to form a stable covering layer. Instead, they may increase the emission of NH₃ and H₂S by adding nutrients or sulfur sources to the manure. Life-cycle assessment highlighted MV’s environmental superiority, with the total environmental cost of MV treatment being 98.0% lower than that of the control (CK), due to the significant ammonia reduction potential of MV. The abatement cost stood at CNY 1 054 per year, representing a 82.7% cost reduction relative to standard expanded vermiculite (CNY 6 113 per year). This performance enhancement originates from the buoyancy and chemical stability of MV, which work together to suppress gas diffusion while ensuring structural durability during extended storage periods. In summary, this study developed a new type of covering material, namely hydrophobic silica-modified expanded vermiculite (MV), which can achieve ammonia emission reduction during manure storage, has no impact on hydrogen sulfide emissions, and simultaneously reduces ammonium nitrogen loss. It can lower environmental costs and has good economic benefits. Therefore, the new covering material is expected to become an economical, safe, and feasible cover in the process of manure storage. This research provides a new approach and theoretical basis for gas emission reduction in the manure storage process.