A life-cycle assessment of Portland cement manufacturing: comparing the traditional process with alternative technologies

Concern over the impact of anthropogenic carbon emissions on the global climate has increased in recent years due to growth in global warming awareness. Approximately 5% of global CO₂ emissions originate from the manufacturing of cement, the third largest source of carbon emission in the United States. In addition to the generation of CO₂ the cement manufacturing process produces millions of tons of the waste product cement kiln dust (CKD) each year contributing to respiratory and pollution health risks. In this paper LCA is used to evaluate the environmental impact of four cement manufacturing processes: (1) the production of traditional Portland cement, (2) blended cement (natural pozzolans), (3) cement where 100% of waste cement kiln dust is recycled into the kiln process, and (4) Portland cement produced when cement kiln dust (CKD) is used to sequester a portion of the process related CO₂ emissions. To reduce uncertainty this manuscript presents a cradle-to-gate life-cycle assessment of several cement products. Analysis using SimaPro 6.0 software shows that blended cements provide the greatest environmental savings followed by utilization of CKD for sequestration. The recycling of CKD was found to have little environmental savings over the traditional process.