High-quality applications of slag from municipal solid waste incineration (HMV) in the product sector

On May 16, 2023, a joint meeting of ITAD (association of operators and owners of thermal waste incineration plants), IGAM (represents the interests of companies processing slag from municipal solid waste incineration) and vgbe was held in Düsseldorf on the topic of “Current developments in the processing and use of municipal solid waste incineration slags”. ITAD, IGAM and vgbe energy e.V. invited participants to a joint conference entitled “Current developments in the processing and use of municipal waste incineration slags” in Düsseldorf on May 16, 2023.

Around 90 participants from industry, research and public authorities responded to this call to discuss the challenges, opportunities and potential solutions for even better use of municipal solid waste slags.

Municipal solid waste slags as a resource

In times of increasing raw material scarcity in the construction sector, the focus on municipal solid waste slags is intensifying as an alternative resource for minerals and metals. Over the years, municipal solid waste slag has established itself as a substitute building material with numerous areas of application. Both from a construction point of view and with regard to environmental requirements, its use in road construction, commercial construction and landfill construction is an obvious choice. The use of municipal solid waste slag thus contributes to the substitution of valuable mineral primary raw materials.

In addition, valuable metals are recovered during the processing of municipal solid waste slag. These recycled metals have a significantly improved climate balance compared to metals from extraction through mining and production with primary materials.

With the enforcement of the Substitute Building Materials Ordinance on August 1, 2023, for the first time nationally uniform and legally binding requirements for the production and installation of municipal solid waste slag for use in technical structures has to be applied. A boost for the use of municipal solid waste slag in the areas of application of this ordinance is to be expected, especially in connection with a more far-reaching regulation on the end of waste.

Innovative processes for the use of municipal solid waste slag

However, municipal solid waste slag can do more. With this in mind, the organisers focused on the question of how the mineral fraction of municipal solid waste slag can be processed and used as secondary aggregate for the concrete and cement industry in the future by using innovative processes. In Germany, several research projects have been successfully launched in recent years, which are investigating precisely this question at different points.

For example, the EMSARZEM research project (use of municipal solid waste slag as a raw material for cement production), funded by the Federal Ministry of Education and Research, is concerned with the separation of metals from finished slags for the purpose of producing a clean mineral product that can be used as a raw material for clinker production in the cement industry.

The research project “Municipal solid waste eco concrete” of Kassel University is dealing with the development of suitable processing paths to achieve an optimal quality of the mineral fraction for use as substitute for aggregates and binders in concrete products.

Finally, a consortium of Heidemann Recycling GmbH and EEW Energy from Waste GmbH presented the product “S-CEM” consisting of processed municipal solid waste slag, which could be used as an additive for the production of selected and configured binders and concretes. According to the companies, this product can contribute to a significant reduction of emissions in CO₂-intensive cement production and to the conservation of natural resources in the future.

Lack of necessary legislation for the concrete and cement industry sector

In Germany, however, there is a lack of legal foundations and corresponding adaptations of standards for such applications. . Therefore, it is urgently needed that legislation and the standardisation institutions address the possible uses of municipal solid waste slags in mixed products. This is the only way to establish further pillars in the sense of the recycling economy in addition to the already proven use of municipal solid waste slag.