Solid recovered fuel (SRF according to EN 15359) is frequently used to substitute primary fuels required for the clinker burning process in the cement industry. Since the ash that is formed during the combustion of the SRF is directly incorporated into the product portland cement clinker, this process is also referred to as “co-processing”. While the use of SRF in cement plants is legally considered as energy recovery, the fact that mineral constituents are incorporated into the clinker implies that technically a certain share of SRF is recycled on a material level. The paper at hand aims at determining this share by analyzing 80 SRF samples representing SRF qualities that are currently available on the market in Austria, Croatia, Slovakia, and Slovenia. Results show that the SRF ashes on average consist of 76.8 % SiO2, CaO, Al2O3 and Fe2O3, the main raw materials that are required for clinker production. Another 14.1 % consist of chemical compounds that are common clinker phases or frequently present in the primary raw materials used for clinker production. Different ways of calculating the recycling index, i.e. the share of SRF (referring to dry mass) that is used on a material level, are discussed, and recycling indices are found to range between 13.5 and 17.6 %. It is concluded that SRF ash represents a suitable secondary raw material for cement clinker manufacturing and that for the cement industry SRF-co-processing offers the possibility to contribute towards reaching the higher recycling rates specified by the European Union.