Gaseous emissions during composting of poplar bark-poultry dung mixtures: First results.

Whereas composting agricultural wastes could solve problems related to wate r and soil quality, it can present a risk of pollution to the atmosphere. T he various gases emitted have to be quantified, and the mechanisms leading to their production, identified. For this purpose, about 25 m(3) of a poplar bark-poultry dung mixture was c omposted in a covered place with natural ventilation, air coming in the low er part and going out through four shafts in the upper part. The gaseous em issions were measured and analysed. At the same time, a control pile was sa mpled in order to determine microbial population and activity. The first he aps (initial C/N of 21) were monitored for one month, then turned and more dung added. The second heaps (initial C/N of 8) were monitored for seven mo nths with two intermediate turnings. Carbon dioxide, methane, ammonia, and nitric and nitrous oxides contents we re measured. Methane, present in depth at high concentration, was emitted a t low concentration. The nitrogen loss (about 50% for the second heap) was half as ammonia. Nitrous oxide constituted less than 1% of the nitrogenous gases, was produced principally at the end of composting, and related to th e presence of nitrification-denitrification and bacteria potentially active in those activities.