Emissions of ammonia, carbon dioxide and particulate matter from cage-free layer houses in California.

Cage-free housing systems have attracted considerable attention in the United States recently as they provide more space and other resources (such as litter area, perches, and nest boxes) for hens and are considered to be more favorable from the standpoint of hen welfare. This study was carried out to quantify emissions of aerial ammonia (NH 3 ), carbon dioxide (CO 2 ) and particulate matter (PM 10 and PM 2.5 ) from cage-free layer houses in California and compare the values with those for other types of layer houses. Two commercial cage-free houses with 38,000 hens each were monitored from March 1, 2012 to April 1, 2013. Results show that NH 3 and CO 2 concentrations in the houses were affected by ventilation rate, which was largely influenced by ambient air temperature. The PM 10 and PM 2.5 concentrations in the houses depended on the activity of birds, ventilation rate and relative humidity of the ambient air. The average emission rates of NH 3 , CO 2 , PM 10 and PM 2.5 were 0.29, 89.9, 0.163 and 0.020 g d −1 hen −1 , respectively. The NH 3 emission rate determined in this study was higher than those of aviary houses. The PM 10 and PM 2.5 emission rates were higher than those reported for high-rise layer houses. [ABSTRACT FROM AUTHOR]