Achieving net-zero greenhouse gas emissions by 2050 under the European Green Deal requires the full mobilisation of industry, especially energy-intensive sectors such as cement. This study provides an accurate quantification of the environmental performance of Ordinary Portland cement produced in mainland Portugal using industrial data and a cradle-to-gate life-cycle model compliant with EN 15804:2012+A2:2019. The results show that clinker is the main contributor and that the principal hotspots are associated with thermal and electrical energy supply and the calcination reaction. External factors such as the electricity generation mix materially influence results, so these processes should be accurately described and representative of the geographical boundaries associated with plant operation. Climate change is the most relevant impact category, and the carbon footprint is 733 kg CO₂ per tonne of cement, with 97% attributable to the identified hotspots. The choice of impact assessment methodology is crucial in life-cycle assessment, and EN 15804:2012+A2:2019 is not compatible with the earlier A1 revision, which affects comparability of Environmental Product Declarations. Overall, the study enhances the measurement and monitoring of sustainability within the cement sector by providing an explicit industry-wide environmental profile with clear system boundaries and hotspot resolution, enabling targeted mitigation. It also clarifies the methodological implications of Environmental Product Declarations, helping to avoid biased comparisons and supporting procurement, disclosure and policy tracking towards sectoral carbon neutrality.