Apparatus and process for compressing moisture containing material including a pair of opposed rolls for receiving and advancing the material therebetween to apply rolling load thereto to compress the material and remove at least a portion of said moisture therefrom, and differential means for causing one of said rolls to rotate at a lower speed than the rolling speed of the other of the rolls, the differential rolling speeds developing friction between the rolls causing the rolls to be heated and apply heat to said material to further remove moisture therefrom, to cause the compressed material to adhere to the one roll and to cause the removed moisture to adhere to the other roll, also alone and in combination, apparatus and process of decomposing organic material such as an animal biomass by the action of aerobic microorganisms in the presence of oxygen, including introducing the organic material into a container having an end adapted to receive the organic material and an output end adapted to discharge the organic material, introducing a medium containing oxygen into the container to facilitate decomposition of the organic material by action of said microorganisms, and advancing the organic material through the container and upon decomposition of the organic material discharging the decomposed organic material out the output end of the container.