Abstract: Bacterial complexes are provided which may be used in the digestion and decomposition of residues of biological origin in the form of biomass, and the transformation of these residues into non-polluting organic compounds. Also provided are the applications of these bacterial complexes to the treatment of waste of biological origin such as excrement (pig, ruminent, equid, or poultry litter), liquid manures, corpses, and stagnant waters. In these applications, this waste is converted into compost or other stable, biodegradable, and non-polluting nitrogenous compounds. The bacterial complexes essentially contain at least one non-pathogenic Bacillus and at least one non-pathogenic Lactobacillus.