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.