Ammonia and methane mitigation from dairy manure using sulfur‐based manure storage additives

Abstract Dairy manure storage is a major source of greenhouse gas emissions and other air pollutants, including methane (CH 4 ) and ammonia (NH 3 ). Easily deployable mitigation strategies, such as manure storage additives, can help reduce the environmental impact of dairy production. Sulfur‐based manure storage additives, specifically gypsum (CaSO 4 ), have been proposed as low‐cost manure amendments that may influence CH 4 emissions; however, their potential to mitigate NH 3 emissions and their effectiveness across sulfur dosages remain unclear. This study evaluated two gypsum additives at low and high levels (G1L: 4.23 mg L −1 ; G1H: 21.15 mg L −1 ; G2L: 5000 mg L −1 ; G2H: 25,000 mg L −1 ) to quantify their effects on NH 3 and CH 4 emissions from dairy manure over a 12‐week period. Cumulative NH 3 and CH 4 emissions were measured using the closed‐chamber manure emission system, which consisted of a closed chamber integrated with a multi‐gas Fourier Transform Infrared analyzer, used to measure emissions from bucket‐sized manure storages. Ammonia losses decreased by 27% and 33% in treatments G2L and G2H, respectively, while treatments G1L and G1H showed no significant effect. The effect on CH 4 emissions mitigation followed the same pattern, with reductions of 82% and 90% in treatments G2L and G2H, respectively. These results demonstrated a dose–response relationship, in which higher gypsum dosages yielded substantial reductions in NH 3 and CH 4 emissions. Overall, manure additive treatment using gypsum at sufficient rates offers a practical strategy to mitigate gaseous nitrogen and carbon losses from dairy manure, supporting more sustainable manure management and contributing to climate and air‑quality goals.