<p>Calcium oxide (CaO), which is mostly derived from (CaCO₃) limestone and silicon dioxide (SiO₂) are the main components in cement manufacture. Yet magnesite-rich limestone (MgCO₃) is often used due to its low cost. As a quality problem was encountered during the first cement production run at the Saoura cement factory (SSC, GICA Algerian cement industrial group), this study was carried out to overcome this issue. The first part involves hundreds of experiments conducted over two years of clinker production, aiming to analyse the effect of magnesium oxide on the clinker’s firing process and mineral composition. The second part describes the use of sulphur trioxide to enhance cement quality, considering the high levels of MgO, CaOl, and Alkali (Na₂O, K₂O). The main findings reveal that high MgO rates negatively affect the mineral composition, chemical and microscopic properties of the clinker produced. However, increasing SO₃ levels improves the cement’s physico-mechanical characteristics, and reduces clinker consumption and CO₂ emissions.</p> Graphical abstract <p></p>