Eco-efficiency assessment of calcium sulfoaluminate clinker production

Calcium sulfoaluminate-based cements (CSA) are proposed as a cement alternative with a low carbon footprint. The nature of CSA makes the manufacturing process to require lower temperature, less fuel, and less calcite. However, it requires aluminum oxide, Al₂O₃, which would be originated from bauxite and bauxite-derived wastes, and sulfur, coming from calcium sulfate or elemental sulfur. An eco-efficiency assessment of CSA cements, benchmarked against the conventional Portland cement, has been performed following the principles of ISO 14045 on eco-efficiency for a total of 240 CSA clinker production scenarios. The eco-efficiency indicator relates an environmental indicator with a product system value indicator, and it is calculated for each of the studied parameters: bauxite geographical origin, the fuel used for clinkering, the source of sulfur, and the composition of the clinker. Eco-efficiency results show a strong dependence on the origin of bauxite, while other parameters, as the fuel used, its content in sulfur, or the supply of other raw materials, are of less importance. The most eco-efficient solutions are those with certain closeness to bauxite sources. To achieve global solutions, that is, cement-making based on CSA independently of the origin of the raw materials, the amount of bauxite needs to be minimized and CSA composition restricted.