Ammonia and greenhouse gas emissions from fattening pig house with two types of partial pit ventilation systems

• Partial pit ventilation (PPV) substantially improves indoor air quality.
• Inlet configuration and season have effects on PPV performance.
• Half of gas emissions are extracted via pit exhaust.
• PPV + air purification system can efficiently reduce gaseous pollution.

To reduce the cost of the air purification system in cleaning the exhaust air from pig buildings, a concept of partial pit ventilation (PPV), which applies an extra pit exhaust extracting a part of air directly from emission source zone, was introduced. The objectives of this study are to quantify gaseous emissions from a fattening pig building with PPV, and to assess the performance of the PPV with two types of air inlets (ceiling air inlet, system-C; wall-jet air inlet, system-W). Two trials were carried out under summer and winter conditions. For each trial and in each type of PPV system, 32 fattening pigs were raised. Gas concentrations and climate data were continuously measured. Results showed that the average indoor concentrations were 2.1–3.4 ppm for NH3, 0.4–0.6 ppm for CH4, and 800–966 ppm for CO2 in summer; and 4.2–4.3 ppm for NH3, 5.0–5.6 ppm for CH4, and 1491–1542 ppm for CO2 in winter. N2O releases were rarely observed in the current set-up. The PPV system substantially improved the indoor air quality. Approximately half of the whole NH3 emission (47–63%) was driven through the pit exhausts. A combination of PPV and air purification system is considered to be a practical and efficient mitigation method for gaseous pollution from pig production. The two types of PPV systems resulted in two different kinds of airflow characteristics, which further affected the gaseous release processes. During summer, lower gas concentrations and emissions were found in system-C than in system-W. During winter, system-C gas concentrations were higher in room air and slightly lower in pit air than system-W. Both systems had similar values of emissions during winter. Higher gas concentrations were found in winter than in summer. On average, the winter trial had lower daily NH3 emissions but higher CH4 and CO2 emissions than the summer trial.