Improving the CO2 performance of cement, part III: the relevance of industrial symbiosis and how to measure its impact

Abstract

Cement production contributes to extensive CO2 emissions. However, the climate impact can vary significantly between different production systems and different types of cement products. The market is dominated by ordinary Portland cement, which is based on primary raw materials and commonly associated with combustion of vast amounts of fossil fuels. Therefore, the production of Portland cement can be described as a rather linear process. But there are alternative options, for example, involving large amounts of industrial byproducts and renewable energy which are more cyclic and thus can be characterized as relatively “synergistic”.The main purpose of this article is to study how relevant the leading ideas of industrial symbiosis are for the cement industry based on a quantitative comparison of the CO2 emissions from different cement production systems and products, both existing and hypothetical. This has been done by studying a group of three cement plants in Germany, denoted as Cluster West, and the production of cement clinker and three selected cement products. Based on this analysis and literature, it is discussed to what extent industrial symbiosis options can lead to reduced CO2 emissions, for Cluster West and the cement industry in general.Utilizing a simplified LCA model (“cradle to gate”), it was shown that the CO2 emissions from Cluster West declined by 45% over the period 1997–2009, per tonne of average cement. This was mainly due to a large share of blended cement, i.e., incorporation of byproducts from local industries as supplementary cementitious materials. For producers of Portland cement to radically reduce the climate impact it is necessary to engage with new actors and find fruitful cooperation regarding byproducts, renewable energy and waste heat. Such a development is very much in line with the key ideas of industrial ecology and industrial symbiosis, meaning that it appears highly relevant for the cement industry to move further in this direction. From a climate perspective, it is essential that actors influencing the cement market acknowledge the big difference between different types of cement, where an enlarged share of blended cement products (substituting clinker with byproducts such as slag and fly ash) offers a great scope for future reduction of CO2 emissions.