Ammonia and hydrogen sulfide concentration and emission patterns for mono-slope beef cattle facilities in the Northern Great Plains

Mono-slope buildings are one type of roofed and confined cattle feeding facility that is becoming increasingly popular in the Northern Great Plains. In response to questions and concerns about the barn environment and air quality regulations, the objectives of this study were to determine gas concentrations in and emissions from these beef cattle facilities and relate these air quality parameters to environmental and manure management factors. Four producer-owned and operated mono-slope beef cattle facilities were monitored continuously for one month each quarter for two years to capture both daily and seasonal variations in gas concentrations, airflow and related environmental data. Two barns maintained deep-bedded manure packs (Pack) and two bams scraped manure and bedding from the pens weekly (Scrape). The north wall curtain openings were adjusted by the producers seasonally or daily, and classified as Open (> 1.5 m, mean = 2.1 m) or Closed (< 1.5 m, mean = 0.5 m). The hourly mean airflow and gas concentrations were modeled as functions of perpendicular (to the barn opening) ambient air speed and curtain opening. Net and gross ammonia and hydrogen sulfide emission rates were calculated based on the average product of hourly mean airflow and concentration models for southerly and perpendicular ambient wind speeds greater than 1.5 m s^-1. Gas concentrations at the south side of the barns were, on average, higher than at the north side for comparable wind speeds when compared as either inlets or outlets. The range between the net and gross average daily mean ammonia emission rates for the Scrape barns was 13 to 60 g head^-1 day^-1 with Open conditions, and less than 10 g head¹ day^-1 for Closed conditions. The corresponding emission rates for the Pack barns were 30 to 100 and less than 30 g head¹ day^-1 for Open and Closed conditions, respectively. The hydrogen sulfide emission rates ranged from 2 to 9 (Open) and less than 1 g head¹ d^-1 (Closed) for the Pack barns. The Scrape barns' hydrogen sulfide emission rates range were less than 2 (Open) and less than 0.1 g head¹ d¹ (Closed). This database improves our understanding of air quality conditions in and around these facilities and will support process-based emission modeling efforts.