Bioscrubber treatment of exhaust air from intensive pig production: Case study in northern Germany at mild climate condition

Abstract

Treatment by field-scale bioscrubber of exhaust air, including ammonia (NH₃) and the greenhouse gases methane (CH₄), nitrous oxide (N₂O), and carbon dioxide (CO₂), from 13 intensive pig production houses located in northern Germany were investigated in 2013 and 2015. NH₃ removal efficiencies varied between 35 and 100% with an overall average value of 79% under the NH₃ inlet fluctuations from 34 to 755 g d^-1 m^-3 in both 2013 and 2015. Results of the electron microscopic analyses demonstrated that the bacteria <i>Nitrosomonas</i> sp. and methanotrophs <i>type I</i> were the dominant NH₃ and CH₄ oxidizers, respectively. However, overall average removal efficiencies of CH₄ was approximately zero, which means CH₄ is hard to remove in bioscrubbers under normal operation. The pH of recirculation water in the bioscrubber varied from 6.1 to 8.1, and the bioscrubbers with low pH values (<7.0) had high NH₃ removal efficiencies (>79%). Electrical conductivity was commonly used to diagnose the bioscrubbers' performance; in the present study, electrical conductivity presented a significant linear relationship with dissolved inorganic nitrogen, which indicates the performance stability of the 13 selected bioscrubbers.