The method involves filling a substrate (10) in three reactors (14-16) in an alternative manner. The substrate is heated in the reactors via steam (19) in an alternative manner such that the substrate is free from germs. The substrate is discharged from the reactors in a continuous and alternating manner. The substrate is cooled in a continuous manner, where filling, heating, discharging and cooling steps are implemented one after another without mixing of the individual substrate load in the reactors in a temporal displaced manner. An independent claim is also included for a device for killing germs in the waste material.
