This report contains information about a research project lead by researchers from Environmental Technology and Management at Linköping University in Sweden. It has been conducted in cooperation with staff from the global cement company CEMEX. The study has been focused on three cement plants in the western parts of Germany, referred to as CEMEX Cluster West. They form a kind of work alliance, together producing several intermediate products and final products. One of the plants is a cement plant with a kiln, while the other two can be described as grinding and mixing stations.
The overall aim has been to contribute to a better understanding of the climate performance of different ways of producing cement, and different cement products. An important objective was to systematically assess different cement sites, and production approaches, from a climate perspective, thereby making it easier for the company to analyze different options for improvements. Theoretical and methodological aspects related to the fields of Industrial Ecology (IE) and Industrial Symbiosis (IS) have played an important role.
A common way of making cement is to burn limestone in a cement kiln. This leads to the formation of cement clinker, which is then grinded and composes the main component of Ordinary Portland Cement. One very important phase of the production of clinker is the process of calcination, which takes place in the kiln. In this chemical reaction calcium carbonate decomposes at high temperature and calcium oxide and carbon dioxide are produced. The calcination is of high importance since it implies that carbon bound in minerals is transformed to CO2. A large portion of the CO2 emissions related to clinker production is coming from the calcination process.
Both clinker and Ordinary Portland Cement (CEM I 42.5) were studied. However, there are other ways of making cement, where the clinker can be substituted by other materials. Within Cluster West, granulated blast furnace slag from the iron and steel industry is used to a large extent as such a clinker substitute. This slag needs to be grinded, but an important difference compared to clinker is that it has already been treated thermally (during iron production) and therefore does not have to be burned in a kiln. With the purpose to include products with clearly different share of clinker substitutes, the project also comprised CEM III/A 42.5 (blended cement, about 50% clinker) and CEM III/B 42.5 N-. (blended cement, about 27% clinker). To sum up, this means that the study involved “traditional”, rather linear, ways of making cement, but also two more synergistic alternatives, where a byproduct is utilized to a large extent instead of clinker.
The methodology is mostly based on Life Lycle Assessment (LCA), from cradle-to-gate, using the SimaPro software. This means that the cement products have been studied from the extraction of raw materials until they were ready for delivery at the “gate” of Cluster West. The functional unit was 1 tonne of product. A lot of data was collected regarding flows of material and energy for the year of 2009. In addition, some information concerning 1997 was also acquired. Most of the used data has been provided by CEMEX, but to be able to cover upstream parts of the life cycle data from the Ecoinvent database has also been utilized.
The extensive data concerning 2009 formed the base for the project and made it possible to study the selected products thoroughly for this year. However, the intention was also to assess other versions of the product system – Cluster West in 1997 and also a possible, improved future case. For this purpose, a conceptual LCA method was developed that made it possible to consider different products as well as different conditions for the product system. Having conducted the baseline LCA, important results could be generated based on knowledge about six key performance indicators (KPIs) regarding overall information about materials, the fuel mix and the electricity mix. The conceptual LCA method could be used for other products and versions of Cluster West, without collecting large amounts of additional specific Life Cycle Inventory (LCI) data. The developed conceptual LCA method really simplified the rather complex Cluster West production system. Instead of having to consider hundreds of parameters, the information about the six KPIs was sufficient to estimate the emissions from different products produced in different versions of the production system (Cluster West).
The results showed that the 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, mainly since it reduces the emissions accounted related to calcination. For example, the CO2-eq emissions related to CEM III/B product were estimated to be 65 percent lower than those for CEM I.
A framework for identifying and evaluating options for improvement has been developed and applied. Based on that framework the present production system was analyzed and illustrated, and different measures for reducing the climate impact were shown and evaluated. Two possible scenarios were defined and the conceptual LCA model used to estimate their climate performance.
The authors’ recommendation is for CEMEX to continue to increase the share of CEM III (the share of good clinker substitutes), and to make efforts to shift the focus on the market from clinker and cement plants to different types of cement (or concrete) or even better to focus on the lifecycle of the final products such as buildings and constructions.
Information 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.
Linköping: Linköping University Electronic Press , 2011. , 191 p.
alternative materials, alternative fuels, secondary fuels, byproduct synergy, cement, CEMEX, climate impact, carbon dioxide, CO2, granulated blast furnace slag, GBFS, industrial ecology, industrial symbiosis, life cycle assessment, LCA