NOVELTY - Treating biological waste e.g. feces, with a view to their transformation into compost or other nitrogen-containing compound, comprises: preparing a substrate, preferably a first substrate in the form of a mixture comprising straw and softwood chips; seeding the first substrate with a bacterial complex; contacting the resultant first substrate with the biological wastes to be treated to form a seeded substrate, preferably second substrate; and force-feeding in a gaseous fluid stream containing oxygen from the second substrate at least until a temperature of 55 degrees C.    USE - The method is useful for: treating biological waste e.g. feces, with a view to their transformation into compost or other nitrogen-containing compound, where the other biological waste includes droppings, litter, manure, liquid manure or mixtures of plant wastes; and forming an organic nitrogen compound (all claimed).    ADVANTAGE - The method allows more efficient capture of gases e.g. ammonia, nitrogen trioxide, methane and hydrogen sulfide involved in air pollution and in attacking the ozone layer, and thus reducing environmental pollution and protecting the ozone layer.    DETAILED DESCRIPTION - Treating biological waste e.g. feces, with a view to their transformation into compost or other nitrogen-containing compound, comprises: preparing a substrate, preferably a first substrate in the form of a mixture comprising straw and softwood chips; seeding the first substrate with a bacterial complex comprising at least a non-pathogenic Bacillus and a non-pathogenic Lactobacillus; contacting the resultant first substrate with the biological wastes to be treated to form a seeded substrate, preferably second substrate; and force-feeding in a gaseous fluid stream containing oxygen from the second substrate at least until a temperature of 55 degrees C. An INDEPENDENT CLAIM is also included for an organic nitrogen compound, obtained by the above method, and comprising a moisture content of 30-60%, a weight ratio of carbon to nitrogen of less than or equal to 10, a total nitrogen content of 40-60 kg/metric ton of dry matter of the compound, and an organic nitrogen fraction of greater than or equal to 70%.