Quantification of CO2 emission from the preparation and utilization of solid waste-based sulphoaluminate cementitious materials

Abstract

The cement industry as a high-emission and an energy-intensive sector, has always been a key concern for the sustainable development. In 2020, China produced over half of the world's cement and the relevant carbon emission is enormous. It's an urgent need to development low-carbon cementitious materials, such as the sulphoaluminate cement (SAC), to achieve a low-carbon society. The prerequisite of low-carbon development is to properly quantify the amount of CO2 emissions during the preparation and utilization of cement. However, there are currently only studies on the calculation of the carbon emission factor of Portland cement (PC), and the carbon emission factor of SAC, especially the calculation of SAC produced using solid wastes is lacking. This study focuses on the quantification of CO2 emissions of solid waste-based sulphoaluminate cement (SW-SAC) from the preparation (raw material transportation, fuel combustion and transportation, electricity consumption, calcination and product transportation) to the utilization processes (carbonation process), and the influence of supplementary cementitious materials (SCMs) on carbon emissions of cementitious materials is also considered. The results show that the carbon emission factor of SW-SAC clinker produced using steel slag, red mud, aluminum ash, FGD gypsum and limestone tailing is 361.021–401.641 kgCO2/tcl, which is 28.14%–35.40% lower than that of PC. And the net carbon emission of SW-SAC is 448.221–488.841 kgCO2/tcl, which is significantly lower than that of PC (693.780 kgCO2/tcl). The carbon emission factor of SW-SAC incorporating SCMs is only 111.395–135.767 kgCO2/tcl, which accounts for 30.9–33.8% of SW-SAC's, and 36.95–45.0% of that of PC incorporating SCMs. By comparing different sectors, it is found that the calcination process is the main carbon reduction sector of SW-SAC. This study quantitatively affirms that the SW-SAC can benefit the low-carbon development of cement industry, but multiple efforts, such as utilization of renewable energy and reduction of clinker proportion, are also required to achieve carbon neutrality.