Quantification of ammonia emissions from dairy and beef feedlots in the Jing-Jin-Ji district, China

It is necessary to obtain accurate ammonia (NH3) emission estimates from concentrated cattle operations to evaluate the contribution of emissions from dairy and beef feedlots in the Beijing-Tianjin-Hebei (or the “Jing-Jin-Ji”) district of China to local dust-haze pollution such as fine particulate matter (PM2.5) and the national animal NH3 inventory. This study examines NH3 emission rates from two dairy and two beef feedlots in four different seasons, which were measured using an inverse dispersion technique in combination with an open-path tunable diode laser. Ammonia emissions from both dairy and beef feedlots are characterized by a distinctive diel pattern with high emission rates during the middle of the day and low rates during the night, which is in good agreement with the diel variation in air temperature and wind speed. In addition, apparent seasonal difference in NH3 emissions from dairy and beef feedlots were also observed, where the greatest emission occurred in summer followed by spring/fall and winter. Annual emission factors (EFs) for beef and dairy feedlots in the Jing-Jin-Ji district were estimated to be approximately 19.8 kg NH3 head−1 yr−1 and 47.8 kg NH3 head−1 yr−1, respectively, accounting for 25% and 30% of the feed N inputs. The NH3 emissions from beef and dairy cattle in this district were estimated to be 45.73 and 105.52 kt, respectively. In future, more field measurements on animal feedlots with various feed/manure management practices, stocking densities and weather conditions are highly requested to reduce NH3 emission uncertainty and characterize the N cycling within animal feedlots.