A machine to carry out the method for the reduction or removal of pathogenic agents and microorganisms contained in solids, comprising a front chamber for the entrance of the material; a contiguous rear chamber associated with the entrance chamber, by means of which the processed material is expelled; said contiguous rear chamber containing a grinding means that rotates when it is actuated by an engine; and a piston that enters into the front chamber running along said chamber into the rear chamber until it reaches a grinding means, where the grinding means consists of a solid, hard and heavy cylinder associated with a transverse axis, said cylinder being provided with a set of longitudinal slots from base to base that form edges with the cylinder surface and where the space between the cylinder surface and the rear chamber inner wall is smaller than 5 mm.