It’s been a busy week for slag and cement with the Global Slag Conference taking place in Istanbul and the announcement that SSAB and Heidelberg Materials are working to develop electric arc furnace slag (EAF slag) into an alternative binder in cement.
The Global Slag Conference had many highlights and one can read all about it in the review. Ikram Ahmed Khan’s presentation about doing business in the Middle East with an ongoing war was a standout. There was also plenty of discussion on the valorisation of steel and newer slags. The announcement from SSAB and Heidelberg Materials ties into this. Traditional sources of ground granulated blast furnace slag are expected to decrease as the iron and steel industries decarbonise. The hunt for alternatives is on.
One key question that the conference posed was who exactly should pay the carbon tax related to using slag as a byproduct. During a panel discussion a cement and concrete producer on a panel noted that there is an ongoing debate on the issue. At present in the European Union (EU), iron and steel producers do not pass on any of the emission costs on to slag users. Users of slag, including cement producers, are able to use the byproduct without having to use their own allowances or buy carbon credits. Hence, the EU emissions trading scheme is intended to incentivise the use of low carbon products such as cement or concrete made with less clinker.
Iron and steel producers are primarily interested in making their primary products. Slag can be a lucrative byproduct but is not their main concern. Yet, since the carbon footprint of iron and steel is higher than cement, it is in their interests to attempt to lobby governments to pass on as many of the CO2 emissions (or ‘allocate’ them to the slag byproduct) as they can. They are, of course, free to put up the price of their slag if they are paying more for carbon credits to make their primary products. How practical this may be in a competitive marketplace remains to be seen though.
One example of an attempt to pass on the emissions allocation by steel producers has been the Germany-based Low Emission Steel Standard (LESS). This is a methodology to define low-carbon steel. It permits that a credit of 0.1t CO2e/t be given for granulated slag or comparable by-products, when sold as clinker substitutes for cement production. This figure was derived following consultation with the BMWK Scientific Advisory Board as part of the BMWK stakeholder process ‘Lead markets for climate-friendly basic materials.’
This potential battle between iron/steel and cement/concrete is partly down to how these different commodity markets work and how they pass on their carbon costs. Broadly speaking: steel is at higher risk of carbon leakage but it finds it harder to pass on carbon costs; cement is at lower risk of leakage but finds it easier to pass on costs. The phasing out of the free allocation of carbon credits and the commencement of the Carbon Border Adjustment Mechanism (CBAM) in the EU adds to the pressure on both sectors and is potentially driving debates such as whether allocations should be passed on to byproducts. It is worth noting that political pressure against the EU ETS is mounting, making it uncertain to tell how far it will go.
Cement producers are used to similar issues from the alternative fuels sector. Here, for example, biogenic feedstocks are prioritised in the EU and the emission allocations are not passed on but other ‘fossil’ feedstocks are liable. This, in turn, affects which feedstocks are prioritised and where the investment goes. For slag, the phase out of free allocations, the introduction of the CBAM and the threat of mounting ETS carbon cost is increasing the pressure to find ways to decarbonise heavy industry through any means available. This presents a situation of competing narratives between the iron/steel and cement sectors. If slag is a ‘waste’ then the steel producers might be deemed responsible for the emissions. Yet, if it is a valuable by-product, then they might argue that the emissions should be passed on down the chain. If so, then this starts to alter the economics of using slag as a secondary cementitious materials (SCM) either for cement or concrete.
The 19th Global Slag Conference will take place in April 2027 in Aachen, Germany
