# Leveraging Blockchain Usage to Enhance Slag Exchange
## 1 Introduction  
Steelmaking, a pivotal industrial process, transforms iron ore and scrap into versatile steel. This production occurs in two stages: primary steelmaking which involves obtaining a semi-product from a converter, electric arc furnace or induction furnace; and secondary steelmaking, or the refining process, which refines the steel using processes like ladle refining furnaces or vacuum degassing furnaces. Both primary and secondary steelmaking processes occur in the presence of slag. These by-products result from the interaction of flux and impurities during the smelting and refining of steels. These slags refine, protect and interact with steel and inclusions, ensuring high-quality steel production. The composition of steelmaking slags varies due to different facilities and the variability of produced steel grades. During the refining process in the ladle furnace, various materials are added to the molten steel for desulfurization, degassing, and adjustment of its chemical composition. Ladle furnace slag is formed as a result of the reactions and interactions between these additives and impurities in the liquid steel. Once the refining process is complete, the slag is separated from the steel. The manufacture of each ton of steel via this method involves the generation of roughly 20 to 30 kg of ladle slag. Globally, in 2023, projections indicate that the production of ladle slag exceeds 20 million tons [1]. Ladle furnace is a solid, glassy material with a range of particle sizes. It typically contains oxides of elements like calcium, magnesium, aluminum and silicon. Disposal methods may include landfilling or other methods that comply with local environmental standards. It can also be used as a raw material for the cement industry [2]. However, steelmaking companies may prefer to send slag batches to landfill either because there are no cement companies interested in it or because the offered price does not compensate the shipment costs. On the other hand, regulations and political actions like the European Union's green deal [3] promote circularity to reduce carbon emissions of such by-products, making their disposal more expensive. Current long-term bilateral deals do not optimize the interest of both cement and steelmaking companies. While the cement company is interested in certain elementscontained in the slag like the calcium, aluminum, or silicon, the steelmaking company is interested in simplifying the process while minimizing costs for getting rid of the slag. This paper explores an auction system which can help to set a fair price for both types of companies more accurately. A blockchain network lies at the core of our proposal to enforce trustworthy data sharing and agreed procedures. Our solution promotes a more dynamic market where any cement company can check the composition of a certain slag aggrupation and offer a price for it. The composition of each slag and its aggrupation in bigger batches is tracked by blockchain. This provides guarantees of the slag quality (i.e., a certainty of its minimum composition) to the cement companies. Promoting a trustworthy market, we expect to increase the slag sold and recycled by the steelmaking companies. This alone can constitute a benefit for the latter and promotes circularity better than any existing regulation. The goal of the solution proposed in this paper is therefore threefold: (1) to track the composition of the slag while it is grouped in the steelmaking process, (2) to help in the price definition through an auction where any interested cement company can participate and (3) to ease circularity metrics extraction for public administrations and regulators. The rest of the paper is organized as follows. Section 2 sets the theoretical background which helps to understand both the technology and the application domain. Section 3 presents the methodology used in this research. Section 4 describes the implementation details of the tool developed.