A garbage disposal for decomposing garbage with microorganisms. The garbage disposal has a tank containing a mixture of garbage, a medium having microorganisms, stirring means for stirring the mixture in the tank in order to supply air into the mixture, and control means for controlling water content percentage of the mixture. The control means controls a stirring of the mixture and/or a temperature of the mixture and/or an air volume blown on the mixture in order to keep water content percentage in a proper value at which the microorganisms are active and a lifetime of the medium is extended.
