Effects of Robot Cleaning and Shallow Pit Manure Storage on the Concentrations and Emission Factors of Ammonia and Greenhouse Gases in Swine Houses

Highlights Daily manure cleaning by robots can simultaneously reduce the concentrations of NH3 and CH4 in the house compared with the shallow pit manure storage. The date that daily manure cleaning by robots can reduce the NH3 and CH4 emission estimates per finishing pig compared with the shallow pit manure storage. It is pointed out that “manure retention time” is a key regulatory factor for gas emission reduction in pig houses. Abstract. A comparative experiment was conducted in a large-scale pig farm in Jiangsu Province, China. Emission characteristics of ammonia (NH 3 ), methane (CH 4 ), and nitrous oxide (N 2 O) were compared between a pig house with robotic daily manure cleaning (RC) and shallow manure pit storage (MS). The experiment was initiated in the spring of 2024 (April 15th) and concluded on June 14th, with a total duration of 61 days. The results showed no difference in ventilation or indoor temperature during the monitoring period, while pig weights ranged from 30 to 81 kg. Under the RC mode, the average daily concentrations of NH 3 and CH 4 in-barn concentration were 27% and 46% lower than under the MS mode. The corresponding average daily emission factors were 3.4 and 29.9 g d -1 pig -1 for NH 3 and CH 4 , representing reductions of 22% and 46% compared to the MS mode. There was no difference in the emission of N 2 O (p > 0.05). The RC system significantly reduced in-barn concentrations and emission rates of NH3 and CH4, likely by shortening the manure retention time inside the barn. The study showed that robotic manure removal technology shortens manure storage time by increasing the frequency of manure cleaning, enabling the simultaneous reduction of ammonia and methane emissions. It offers a promising technical approach for mitigating gaseous pollution in large-scale pig production.