Calcium-containing slag material is produced in iron- and steelmaking worldwide, including Finland. One process route utilizing this calcium, being developed towards large-scale application, is the so-called slag2pcc concept. Using ammonium salts, up to 50% of the calcium content is selectively extracted from steel converter (BOF) slags in a two-stage aqueous process operating at ambient temperatures and pressures. Precipitated calcium carbonate (PCC) is produced by reacting the dissolved calcium with CO2, thereby also regenerating the ammonium salt for recovery and re-use. Process optimisation involves the efficient production of PCC material with a certain quality, requiring effective separation of the solids from the solutions as well as maximal extraction of slag calcium against minimal solvent salt losses. In this paper the performance of the process, the possibility of continuous operation and the progress towards larger scale operation are reported. In addition, the consumption of process commodities such as energy and water is addressed by life-cycle assessment (LCA) approach, in comparison with traditional PCC production technologies. The slag2pcc concept combines the advantages of converting an industrial by-product into a valuable material, reducing use of natural material and streams to landfills while binding some of the CO2 produced by the process generating the slag.