NOVELTY - Waste matter from animals is treated by collecting waste matter from the animals, inhibiting urease activity in the collected waste matter, and separating the urease-activity inhibited waste matter into a urea-rich fraction and urea-lean fraction.    USE - The method is for treating waste matter (feces and liquid manure) from farm animals, or for producing urea or urea formaldehyde, or biogas fuel (claimed). It produces urease-inhibited animal waste matter urea product that is useful as raw material for producing urea products, e.g. urea formaldehyde plastic, barbiturates, and melamine, and applied as animal fodder, moisture lotion agent, binder agent, snow- and de-icing agent, agent from separation fatty acids, cleaning of smoke gasses, paper coating, or chipboard binder component.    ADVANTAGE - The inventive disposes animal waste matter without depending on disposal through agricultural system. It retains nitrogen in waste matter from animals. It reduces or avoids loss of ammonia from waste matter from animals. Only a minimum of ammonia is produced in stable systems due to hydrolysis of urea, thus improving indoor climate in the stables. This improved indoor climate results in an increased lung capacity of the stocked animals e.g. improved health condition of the animals and consequently a more effective breeding of livestock can be obtained. Since there are minimum emissions of ammonia from he stable systems, pollution of the atmosphere with ammonia and its associated environmental problems can be reduced or eliminated.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for:    (a) a system for treating waste matter from animals, comprising waste-matter collector, separator (14) for separating the collected waste matter into a urea-rich fraction and urea-lean fraction, and urease-inhibitor storage tank (11, 16);    (b) a urea-lean biogas fuel product, comprising urea-lean fraction of waste matter that has been treated by the inventive method;    (c) a method of controlling the content of nitrogen in manure from animals, comprising treating the manure with the inventive method, and in waste-matter treatment system;    (d) a stable (12) for animals, comprising the waste-matter treatment system of the invention;    (e) a biogas reactor system for producing biogas from waste matter from animals, comprising a waste-matter treatment system.    DESCRIPTION OF DRAWING(S) - The drawing shows a sketch of the system used in the invention.    Urease-inhibitor storage tank (11, 16)    Upper stable (12)    Separator (14)    Storage container (15)