Method for producing non-putrescible sludge and energy and corresponding plant

The invention relates to a method for producing non-putrescible sludge and energy, wherein said method includes the following steps: (i) producing digested sludge by means of primary sludge digestion; (ii) producing a first aqueous effluent and digested sludge, which are at least partially dehydrated by a first liquid-solid separation of the digested sludge produced in step (i); (iii) producing digested sludge at least partially dehydrated and hydrolysed by thermal hydrolysis of the at least partially dehydrated digested sludge produced in step (ii); (iv) digesting the at least partially dehydrated and hydrolysed digested sludge produced in step (iii); wherein said method further includes a step of recovering the biogases formed during said digestion and said primary digestion, and a step of producing energy from said biogas, including a first sub-step of producing the energy required for implementing said thermal hydrolysis and a sub-step of producing excess energy, the entirety of the biogas being used for producing electricity.