Use of bedding materials in beef bedded manure packs in hot and cool ambient temperatures: Effects on ammonia, hydrogen sulfide, and greenhouse gas emissions

Throughout the Upper Midwest, producers have observed increased land and fertilizer prices, resulting in increased popularity of confinement feeding facilities such as mono-slope and hoop barns with bedded packs. Environmental and public pressure has been placed on the agriculture community to reduce ammonia (NH₃), hydrogen sulfide (H₂S), and greenhouse gas (GHG) emissions from concentrated animal feeding operations (CAFOs). This study was conducted to determine the effects of bedding material (corn stover (CS), bean stover (BS), wheat straw (WS), or pine wood chips (PC)) and ambient temperature (15°C (COOL) or 30°C (HOT)) on NH₃, CH₄, CO₂, N₂O, and H₂S flux in air samples collected in the headspace above lab-scale bedded packs. All bedded packs were housed at 18°C for an initial three weeks before being placed in their respective environmental chambers at 15°C or 30°C for the remainder of the 6-week study period. Significant two-way interactions of bedding material by temperature for NH3 flux were observed (p = 0.0094). Ammonia flux was greater at higher temperature, while CS bedding had the lowest NH₃emissions compared to the other bedding materials. A significant two-way interaction of bedding material by temperature for H₂S flux was observed (p < 0.0001), with significantly greater H₂S produced in the headspace of COOL-BS packs compared to all other treatments. Additionally, a significant (p = 0.0357) two-way interaction of temperature by age of the bedded pack was observed for H₂S flux. Hydrogen sulfide flux appeared to be influenced by low bedded pack pH to a greater extent than by increase in temperature. Greenhouse gas emissions tended to be higher from bedded packs in HOT treatments. A significant (p = 0.0422) interaction among bedding material, temperature, and age of the bedded pack was observed for CH₄. Significantly greater CH₄flux was observed in the headspace above HOT-BS and HOT-CS at week 6 compared to all other treatments. A significant two-way interaction of bedding material by temperature was observed for CO₂flux (p = 0.0189). The largest CO₂levels were observed above WS bedding material regardless of temperature. Nitrous oxide flux decreased over the 6-week study for all bedded packs, while WS and PC bedded packs produced the greatest N₂O flux. The results indicate that feedlot operators maintaining bedded pack facilities will have the greatest reduction in NH₃emissions when using CS bedding, regardless of ambient temperature. To reduce CH₄emissions, producers should avoid allowing BS and CS bedded packs that are maintained for longer than six weeks in HOT (30°C) temperatures; frequent cleaning during summer months is recommended. Based on the CO₂equivalents of CH₄and N₂O, producers should consider PC as an option to reduce GHG emissions.