Degradation of plant material by animals is an important transformation pathway in the nitrogen (N) cycle. During the involved processes, volatile reduced alkaline nitro-gen compounds, mainly ammonia (NH₃) and aliphatic amines such as trimethylamine (TMA), are formed. Today, animal husbandry is estimated to constitute a main source of aliphatic amines into the atmosphere with TMA being the main emitted compound. Here, we show how the interaction between faeces and urine in animal production sys-tems provides the primary source for agricultural TMA emissions. Excreted urine con-tains large quantities of urea and TMA-N-oxide, which are transformed into NH₃ and TMA, respectively, via enzymatic processes provided by microbes present in faeces. TMA emissions from areas polluted with urine-faeces mixture are on average in the order of 10 to 50nmolm⁻² s⁻¹. Released amines promote secondary aerosol particle formation in the agricultural emission plume. The atmospheric lifetime of TMA, which was estimated to be in the order of 30 to 1000s, is determined by the condensation on aerosol particles.