Journal of Cleaner Production xxx (2008) 1–8
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Journal of Cleaner Production
journal homepage: www.elsevier.com/locate/jclepro
A life-cycle assessment of portland cement manufacturing: comparing the traditional process with alternative technologies
Deborah N. Huntzinger a, *, Thomas D. Eatmon b
Department of Civil andEnvironmental Engineering, University of Michigan, 1351 Beal Avenue, Ann Arbor, MI 48109, United States Nelson Mandela School of Public Policy, Southern University, Baton Rouge, LA 70813, United States
a r t i c l e i n f o
Article history: Received 26 October 2006 Accepted 13 April 2008 Available online xxx Keywords: Cement manufacturing Life-cycle analysis Carbon emissions
a b s t r a c tConcern 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 tonsof 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. Therecycling of CKD was found to have little environmental savings over the traditional process. Ó 2008 Elsevier Ltd. All rights reserved.
1. Introduction Increased public awareness of the threats posed by global warming has led to greater concern over the impact of anthropogenic carbon emissions on the global climate. The current level of carbon dioxide (CO2) in the atmosphere is approaching 380 ppm[8,29]. Without drastic market, technological, and societal changes CO2 concentrations are projected to increase to over 800 ppm by the end of the century . Approximately 5% of global carbon emissions originate from the manufacturing of cement. The calcination process (driving off CO2 from CaCO3 to form CaO) accounts for roughly half of the CO2 emitted, while the remaining carbon results fromenergy usage during the production process [13,34]. According to the International Energy Agency’s (IEA) Greenhouse Gas R&D Programme , cement production generates an average world carbon emission of 0.81 kg CO2 per kg cement produced. On average, approximately 1 t of concrete is produced each year for every human being in the world . Therefore, concrete (i.e. cement) is one of the World’smost signiﬁcant manufactured materials. Because of its abundance in the world market, understanding the environmental implications of concrete and
cement manufacturing is becoming increasingly important [19,20,35,36,38]. For globally signiﬁcant products such as cement, environmental life-cycle assessment (LCA) is a valuable tool for improving our understanding of the environmental hazards posed bya product’s life stages. In addition, it allows cement producers to optimize the manufacturing process by reducing adverse environmental impacts. 2. Background 2.1. Cement manufacturing and examined processes Traditional portland cement is composed primarily of calcium silicate minerals (Table 1). The raw materials are quarried or mined and transferred to the manufacturing facility to be...