Comparative life cycle assessment of reactive MgO and Portland cement production

Reactive magnesia (MgO) cements are proposed as a potentially sustainable binder due to their lower production temperatures (∼800 vs. 1450 °C) than Portland cement (PC) and ability to fully carbonate and gain strength during setting. Reactive MgO is mainly produced via the calcination of magnesite. Environmental implications of reactive MgO production must be analyzed before any final conclusions can be made regarding their contribution to the sustainability of the cement industry. This study evaluates the environmental impacts of reactive MgO production and provides a comparison with PC production using a life-cycle assessment (LCA) approach. The advantages of MgO production with respect to radiation, ozone layer, eco-toxicity, acidification/eutrophication, minerals and fossil fuels outweigh the disadvantages when compared to PC production. MgO has a lower impact on the overall ecosystem quality and resources than PC, but poses a larger damage to human health due to the high coal usage by most plants. The decomposition of magnesite releases a higher amount of CO2 than limestone (∼1.1 vs. 0.78–0.83 t/t), creating a higher climate change score for MgO despite its lower production temperatures. However, when the carbonation capability of MgO cements is considered, their net CO2 emissions are ∼73% lower than PC. The introduction of a strength ratio modification to MgO production results in ∼13% and ∼32% lower CO2 intensity and damage impact on human health when compared to PC production, respectively. The influence of energy type and amount on different impact and damage categories associated with MgO production was revealed by scenario modelling. The quantity of raw materials had a negligible effect on the overall environmental impact of reactive MgO production, whereas increasing the emissions led to an increase in climate change. Energy was identified as the key parameter with the highest influence on the environmental burdens of reactive MgO production. Results indicate that the use of alternative fuels could further improve the overall sustainability of reactive MgO cement production.