A tempering device for tempering of biomass contained in a container, including at least one tempering mechanism, and at least one conveying device for conveying a mass flow of biomass in a main flow direction. The at least one conveying device includes at least one agitator, and wherein the at least one tempering mechanism is arranged in the main flow direction generated by the at least one conveying device. The at least one tempering mechanism is tubular with an inner tube and with an outer tube arranged coaxially to the inner tube. The inner tube and the outer tube form an intermediate space through which a tempering medium may flow. The tempering mechanism is oriented relative to the conveying device such that, in operation of the heating device, at least 40% of the delivery volume of the mass flow generated by the conveying device flows through the inner tube.