Process of recycling a bituminous product such as for example a waste bituminous membrane product optionally containing reinforcement layers comprising the steps of: - Collecting waste bituminous products, preferably waste bituminous membrane products containing bituminous layers and optionally reinforcement layers characterized by sorting the waste bituminous products in a series of n waste bituminous product batch(es), - A first grinding of each batch of said series of n waste bituminous product batch(es) in a knife shredder for reducing the size of said each batch in a first shredded batch having a mean particle size distribution comprised between 20 and 50 cm, preferably between 20 and 40 cm, - A second grinding of each first shredded batch in a rotor granulator where each first shredded batch is reduced in size to a first crushed batch having a mean particle size distribution between 5 and 25 cm, preferably between 8 and 20 cm, - A third grinding of each first crushed batch in a rotor granulator (8, 9) where each first crushed batch is reduced in size to a first ground batch having a mean particle size distribution between 20 and 50 mm, preferably between 25 and 40 mm, more preferably between 27 and 35 mm, - Conveying the each first ground batch on a vibrating sieve (12, 13) to collect each second ground batch, being each first ground batch substantially depleted from dust and particles having a particle size d 100 lower than 8 mm, preferably lower than 7 mm, more preferably less than 6 mm, - Separating metal pieces from non-metal pieces by application of Foucault current to each second ground batch and collecting each third ground batch, being each second ground batch substantially depleted from metal pieces, - Introducing at least one third ground batch into a recycling unit having at least a rotor and a stator and an micronization chamber, said third ground batch being heated and melted by shear strength upon the operation of the stator, rotor and micronization chamber and collecting a melted product. - Collecting waste bituminous products, preferably waste bituminous membrane products containing bituminous layers and optionally reinforcement layers characterized by sorting the waste bituminous products in a series of n waste bituminous product batch(es), - A first grinding of each batch of said series of n waste bituminous product batch(es) in a knife shredder for reducing the size of said each batch in a first shredded batch having a mean particle size distribution comprised between 20 and 50 cm, preferably between 20 and 40 cm, - A second grinding of each first shredded batch in a rotor granulator where each first shredded batch is reduced in size to a first crushed batch having a mean particle size distribution between 5 and 25 cm, preferably between 8 and 20 cm, - A third grinding of each first crushed batch in a rotor granulator (8, 9) where each first crushed batch is reduced in size to a first ground batch having a mean particle size distribution between 20 and 50 mm, preferably between 25 and 40 mm, more preferably between 27 and 35 mm, - Conveying the each first ground batch on a vibrating sieve (12, 13) to collect each second ground batch, being each first ground batch substantially depleted from dust and particles having a particle size d 100 lower than 8 mm, preferably lower than 7 mm, more preferably less than 6 mm, - Separating metal pieces from non-metal pieces by application of Foucault current to each second ground batch and collecting each third ground batch, being each second ground batch substantially depleted from metal pieces, - Introducing at least one third ground batch into a recycling unit having at least a rotor and a stator and an micronization chamber, said third ground batch being heated and melted by shear strength upon the operation of the stator, rotor and micronization chamber and collecting a melted product.