Unveiling the intrinsic relationship between ammonia and hydrogen sulfide generation during composting

Microbial nitrogen and sulfur metabolism release foul gases (NH 3 and H 2 S) during manure composting, which causes environmental pollution and element loss. The synergistic reduction of NH 3 and H 2 S emissions is of great significance. However, it is yet unclear whether NH 3 and H 2 S generation are relevant and co-regulable during composting. Therefore, this study supplemented available nitrate (N) and nitrate + cysteine lyase inhibitor (NI) to explore their effects on foul gases emission. Compared to CK composting, H 2 S cumulative release reduced by 55.05% and 62.27% during N and NI composting, respectively, and NH 3 cumulative release reduced by 61.86% and 59.55%. Additionally, the fitted curves results suggested that nitrate supplementation enhanced the correlations between microbial nitrate reduction, sulfate reduction and oxidation. Therefore, this study revealed that there was an intrinsic relationship between NH 3 and H 2 S generation during composting, and the regulation of microbial structure and metabolism contributed to the co-reduction of foul gases. • The intrinsic relationship between NH 3 and H 2 S generation was established. • The supplementation of nitrate achieved the co-reduction of foul gases. • The sulfate reduction was inhibited and sulfur oxidation was promoted. • The inorganic nitrogen conversion and organic nitrogen mineralization was weakened.