Industrial symbiosis for improving the CO2-performance of cement

Justification of the paper Cement production is one of the largest contributors to global CO2-emissions. However, the context and characteristics of the production and the cement products vary a lot. A significant part of the production must be characterized as rather linear, for example, to a large extent based on fossil fuels and involving material flows that are not closed. But there are also much more synergistic examples, involving industrial by-products, renewable energy, etc. Clearly, there are opportunities for improvement within the cement industry and it is interesting to analyze to what extent increased industrial symbiosis can lead to improved climate performance. This has been done by studying the production of cement clinker and three selected cement products produced within the Cluster West in Germany, consisting of three cement plants that are owned by the multinational company CEMEX. The methodology is mostly based on Life Cycle Assessment (LCA), from cradle-to-gate.PurposeThe overall purpose is to contribute to a better understanding of the climate performance of different ways of producing cement, and different cement products. The climate impact is assessed for “traditional”, rather linear, ways of making cement, but also two more synergistic alternatives, where the by-product granulated blast furnace slag (GBFS) is utilized to a large extent, substituting cement clinker. It is also shown how the climate performance of the West Cluster has changed from 1997 until 2009 (the main year of study), and investigated how further industrial symbiosis measures could improve the performance.Theoretical frameworkTo a large extent this project has been based on mapping and analysis of relevant flows of material and energy, where LCA methodology has played an important part. Theoretical and methodological aspects related to the fields of Industrial Ecology and Industrial Symbiosis have played an important role. The findings are discussed in relation to some of the key ideas within these fields. The paper generates insight into the methodological challenge of quantifying environmental performance of different production approaches and basically what CO2 improvement potential cement industry has by taking industrial symbiosis measures.ResultsThe results showed that the cement clinker produced at Cluster West is competitive from a climate perspective, causing CO2-eq missions that are a couple of percent lower than the world average. During the twelve year period from 1997 to 2009 these emissions became about 12 percent lower, which was mainly achieved by production efficiency measures but also via changing fuels. However, the most interesting results concern the blended cement products. It was manifested that it is very advantageous from a climate perspective to substitute clinker with granulated blast furnace slag. For example, the CO2-eq emissions were estimated to be 65 percent lower for the best product compared to “ordinary cement”.ConclusionsInformation and measures at the plant level are not sufficient to compare products or to significantly reduce the climate impact related to cement. To achieve important reductions of the emissions, measures and knowledge at a higher industrial symbiosis level are needed.