A laboratory study on mitigation of particulate matter, ammonia and airborne bacteria from litter of cage-free layer housing

Concerns over animal welfare have led to pledges of sourcing cage-free only eggs by many U.S. food retailers and restaurants. Compared with the conventional cage, cage-free hen housing offers hens more space and opportunities to exercise their natural behaviors. However, cage-free housing poses many environmental challenges, including high particulate matter (PM), ammonia (NH₃), and airborne bacteria (AB) levels. Spraying electrolyzed water (EW) on litter floor can mitigate PM and bacteria in cage-free hen houses; however, it may cause higher NH₃ due to increase in litter moisture content. In this study, lab-scale experiments were conducted to assess the effect of EW spray dosage, pH, and free chlorine (FC) concentration on PM, NH₃, and AB emissions of litter from cage-free hen houses. The results showed that higher spray dosages led to greater PM reduction (e.g., PM reduction of 71%, 81% and 89% immediately after EW spray at 25, 50 and 75 mL [kg dry litter]^-1 d^-1, respectively) but higher NH₃ emissions. Spraying EW at the higher FC level led to lower AB. While application of lower pH liquid can reduce NH₃, there are concerns about potential corrosive effect of the application on layer housing equipment. To address this issue, solid litter additive (PLT®) at three application rates (i.e., 0.01, 0.02, and 0.03 kg [kg dry litter]^-1 at litter depth of around 4–5 cm) along with spray of neutral-pH EW was tested for NH₃ mitigation. Results to date show that the three application rates of the litter additive reduced NH₃ generation/emission by 28–79%.