Waste and industrial by-products are increasingly used in the production of cement clinker and cement, as they are used both as secondary fuels and as secondary raw material sources. The latter include secondary raw materials that enter the clinker burning process as part of the raw meal and supplementary cementitious materials that are added to the clinker for cement production. As these waste-derived materials are partially or fully incorporated in the product, they are recycled from a technical point of view and a certain proportion of the cement consists of recycled material. In this paper, a method is developed which allows the determination of the recycled content in one ton of cement. Not only the individual mass flows but also the material flows of the compounds required for the cement are balanced. In addition, a heavy metal balance is part of this method, whereby the influence of the secondary raw materials on the pollutant input into the cement is described. In the present work, this method is applied to two Austrian cement plants. It is shown that one ton of cement consists of 365.5 kg and 387.4 kg of secondary materials, respectively. The balancing of heavy metals indicates that the use of alternative fuels causes a relevant input of antimony into the cement. Furthermore, the use of supplementary cementitious materials results in elevated contents of arsenic, cobalt and lead.