Abstract: Heat liberated during an exothermic biochemical reaction is utilized in carrying out an operation requiring energy such as drying the product obtained from the reaction or sterilizing the substrate used for the reaction. The liberated heat is absorbed by a vaporizable cooling medium for transfer to the operation requiring energy. Alternatively the temperature of the cooling medium subsequent to the absorption of heat thereby is raised by compressing the vaporized cooling medium. The heating cooling medium is used to carry out the operation requiring energy. An arrangement which includes a bioreactor is also disclosed and includes heat pump means for permitting utilization of heat liberated during an exothermic biochemical reaction in the performance of an operation requiring energy.