The judgment of the ECJ gave answer to a request for preliminary ruling, submitted in the course of proceedings between Gävle Kraftvärme AB and the Regional Authority of Gävleborg, concerning the authorisation to operate a combined heat and power plant. In the dispute the question arose whether a waste incinerator under EU law should be regarded as an incineration or a coincineration plant, which is an important difference from administrative and economic aspects. While the ECJ did not give a classification for the plant in question, it declared that the criteria to differentiate have to be based on the main purpose of the plant and on the relation between the volume of energy or products produced by the plant and the waste it generates.