Effects of cornstalk and sawdust coverings on greenhouse gas emissions during sheep manure storage

Abstract

Manure covered by organic materials during the storage has shown that it can effectively reduce emissions of greenhouse gases, but few studies have focused on the bacterial communities in manure or the coverage and mechanism responsible for reducing gas emissions. Therefore, this study investigated the impacts and mechanisms of cornstalk and sawdust coverings on greenhouse gas emissions during sheep manure storage. Sheep manure covered by organic material reduced nitrous oxide (N2O) emissions (42.27%–42.55%) relative to uncovered control through physical adsorption and biological transformation of Acinetobacter, Corynebacterium, Brachybacterium, Dietzia and Brevibacterium. Sheep manure covered by organic materials also increased methane (CH4) emissions (16.31%–43.07%) by increasing anaerobic zones of coverage. Overall, coverings reduced carbon dioxide equivalent (CO2eq) by 29.87%–33.60%. Coverings had less effect on the bacterial diversity and community of sheep manure, and the number of bacteria shared by sheep manure and the covering material increased with storage progress, indicating that these bacteria were transferred to the covering materials with gas emissions and moisture volatilization. Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) images showed that functional group intensities of the covering materials increased and the fibrous structures became more disordered during the storage period. In general, it was safe to use organic materials as coverages during sheep manure storage, which was conducive to reducing greenhouse gas emissions.