Assembly of a living surface for a farm mammal, in particular cattle, and a processing device for processing urine from the farm mammal, wherein the living surface is configured to catch the excretory products comprising feces and urine from the farm mammal, wherein the assembly comprises urine removal means for removing urine essentially separately from feces and draining the urine from the living surface in a urine-rich stream and is configured to feed the urine-rich stream to the processing device, and wherein the processing device comprises a nitrogen removal device for removing nitrogenous substances from the urine-rich stream.
