Despite a difficult economic and political environment, the figures for 2025 on the production and use of ferrous slags demonstrate that this by-product of steelmaking once again contributes to the circular economy, resource conservation and climate protection. Of the 10.9 million tonnes of ferrous slags produced in Germany, 10.2 million tonnes, or 94 percent, were used in building materials, fertilisers and internally within the plants. This avoided the extraction of 11 million tonnes of natural rock as well as the emission of 4 million tonnes of CO₂.
The 10.9 million tonnes of ferrous slags produced in 2025 comprise 6.3 million tonnes of blast furnace slag and 4.6 million tonnes of steelworks slag. Of this total, 6.3 million tonnes were used in cement, 3.0 million tonnes in road construction, 0.4 million tonnes in fertilisers and 0.5 million tonnes internally within the plants.
Long-Term Balance Since 1949
Between 1949 and 2025, by-products of steel production have replaced a total of 1.15 billion tonnes of natural rock. Of this, 429 million tonnes are attributable to the use of granulated blast furnace slag in cement, 633 million tonnes to the use of aggregates as a building material, and 87 million tonnes to converter lime as a fertiliser. In addition, the substitution of Portland cement clinker with granulated blast furnace slag in cement resulted in 201 million tonnes less CO₂ emissions over this period.
Call for Adapted Regulatory Frameworks
Thomas Reiche, Managing Director of FEhS – Institute for Building Materials Research, which compiles the figures annually, comments on the results: "The balance sheet for the production and use of ferrous slags for the year 2025 shows once again: industrial by-products are an important component of circular economic activity. They reduce the necessary use of natural raw materials and protect the climate. In order to be able to maintain and increase this contribution in the future, we need reliable, practice-oriented adjustments to the regulatory framework in Germany and Europe as quickly as possible. This also applies not least to the new slags resulting from the transformation of the steel industry, on which we have been conducting research with numerous partners for several years. We therefore appeal to the rule-setting institutions to promptly set the course for a circular economy that delivers sustainable results in practice."
