NOVELTY - Producing biogas comprises charging a fermentation tank with a space velocity of at least 8 kilograms per cubic meter and per day (kg/(m3d)) and operating in a thermophilic region. A heat exchange device is automatically controlled in such a way that an actual temperature is determined in the fermentation tank, and a conditioning fluid is introduced as an initial flow into a heat exchange body (2) such that a content of the fermentation tank is thermally affected by an air conditioning fluid through a heat exchange surface of the heat exchange body.    USE - The method is useful for producing biogas (claimed).    ADVANTAGE - The biogas production method and biogas production apparatus can be safely and efficiently operated in thermophilic range.    DETAILED DESCRIPTION - Producing biogas comprises charging a fermentation tank with a space velocity of at least 8 kilograms per cubic meter and per day (kg/(m3d)) and operating in a thermophilic region. A heat exchange device is automatically controlled in such a way that an actual temperature is determined in the fermentation tank, and a conditioning fluid is introduced as an initial flow into a heat exchange body (2) such that a content of the fermentation tank is thermally affected by an air conditioning fluid through a heat exchange surface of the heat exchange body. The flow has a flow temperature which is temporarily more and temporarily less, than the actual temperature. An INDEPENDENT CLAIM is also included for a biogas production apparatus comprising a fermentation tank and a heat exchange device including a heat exchange body having a content of the fermentation vessel thermally influencing heat exchange surface and a controller. The controller is configured to determine an actual temperature in the fermentation tank and to introduce a conditioning liquid as the initial flow into the heat exchange body such that the flow has a flow temperature which is temporarily more and temporarily less, than the actual temperature.    DESCRIPTION OF DRAWING(S) - The drawing shows a biogas production device comprising a fermentation vessel with multiple Heat exchange bodies arranged along container walls.    Dry fermentation tank (1)    Heat exchange body (2)