Cement is a vital and commonly used construction material that requires large amounts of resources and the manufacture of which causes significant environmental impact. However, there are many different types of cement products, roughly ranging from traditional products with rather linear resource flows to more synergistic alternatives where industrial byproducts are utilized to a large extent. Life Cycle Assessment (LCA) studies indicate the synergistic products are favorable from an environmental perspective.

In co-operation with the global cement producing company CEMEX a research project has been carried out to contribute to a better understanding of the CO₂ performance of different ways of producing cement, and different cement products. The focus has been on Cluster West, which is a cement production cluster consisting of three plants in Germany.

This paper is the first in a series of three, all of which are included in this special issue. It has two main aims. The first is to carry out an attributional LCA and compare three different cement products produced in both linear and synergistic production setups. This has been done for cradle to gate, focusing on CO₂-eq emissions for Cluster West. The second aim of this part is to develop and test a simplified LCA model for this production cluster, with the intention to be able to compare different versions of the production system based on the information of a few parameters.

The attributional LCA showed that cement products that contain a large proportion of byproducts, in this case, ground granulated blast furnace slag from the iron and steel industry, had the lowest unit emissions of CO₂-eq. The difference between the lowest emission product (CEM III/B) and the highest (CEM I) was about 66% per tonne. A simplified LCA model based on six key performance indicators, instead of approximately 50 parameters for the attributional LCA, was established. It showed that Cluster West currently emits about 45% less CO₂-eq per tonne of average product compared to 1997. The simplified LCA model can be used effectively to model future changes of both plants and products (which is further discussed in part II and part III).

Cement production is among the largest anthropogenic sources of carbon dioxide (CO2) and there is considerable pressure on the cement industry to reduce these emissions. In the effort to reduce CO2 emissions, there is a need for methods to systematically identify, classify and assess different improvement measures, to increase the knowledge about different options and prioritize between them. For this purpose a framework for assessment has been developed, inspired by common approaches within the fields of environmental systems analysis and industrial symbiosis. The aim is to apply a broad systems perspective and through the use of multiple criteria related to technologies and organization strategies facilitate informed decision-making regarding different CO2 performance measures in the cement industry.

The integrated assessment framework consists of two parts: a generic and a case-specific part. It is applied to a cement production cluster in Germany called Cluster West, consisting of three cement plants owned by CEMEX. The framework can be used in different ways. It can be used as a tool to perform literature reviews and categorize the state-of-the-art knowledge about options to improve the CO2 performance. It can also be used to assess options for the cement industry in general as well as for individual plants.

This paper describes the assessment framework, the ideas behind it, its components and the process of carrying out the assessment. The first part provides a structured overview of the options for improvement for the cement industry in general, while the second part is a case-specific application for Cluster West, providing information about the feasibility for different categories of measures that can reduce the CO2 emissions. The overall impression from the project is that the framework was successfully established and, when applied, facilitated strategic discussions and decision-making. Such frameworks can be utilized to systematically assess hundreds of different measures and identify the ones most feasible and applicable for implementation, within the cement industry but also possibly in other sectors. The results demonstrated that even in a relatively synergistic and efficient production system, like Cluster West, there are opportunities for improvement, especially if options beyond “production efficiency” are considered.

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 ClusterWest, 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 1997e2009, 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.

Justification of the paper

Industrial activities such as cement production are among the largest sources of human-induced greenhouse gas emissions and there are ongoing efforts to reduce the CO₂ emissions attributed to them. In order to effectively improve climate performance of cement production, it is essential to systematically identify, classify, and evaluate various improvement measures and implement the most effective and feasible measures.

This has been done in this article by developing an assessment framework based on concepts of Industrial Ecology and Industrial Symbiosis which creates an structure for seeking and evaluating the performance and feasibility of various CO₂ improvement measures. The developed framework has a wide system perspective, takes a wide range of CO₂ improvement measures, and treats all material, and energy flows within the industry as potentially useful resources. This framework is applied in practice for assessing the most feasible measures to apply within the Cluster West in Germany, consisting of three cement plants that are owned by the multinational company CEMEX.

Purpose

Use the concepts of industrial ecology and industrial symbiosis and develop an assessment framework for aggregating, categorizing, and evaluating various CO₂ improvement measures for a given production system. In addition, apply this framework on an actual cement production system and summarize the results both in qualitative and quantitative terms.

Theoretical framework

The assessment framework developed in this article is based on the concepts of Industrial Ecology and Industrial Symbiosis: (1) study of the flows of material and energy in production systems is important, (2) emphasizing on the importance of studying industrial systems in integration with their surrounding systems, not as isolated entities, and (3) in an industrial ecosystem no material and energy stream should be treated as waste and all material and energy streams are potentially useful inputs for other industrial processes.

Results

The result is an assessment framework which can be used to systematically gather, classify and evaluate different CO₂ improvement measures for cement production. This framework consists of two parts: (1) generic assessment and (2) site-specific assessment of CO₂ improvement measures. The first part considers general aspects of the measures such as level of Industrial Symbiosis (i.e. degree of connectedness which is required for their implementation), the potential of each measure for reducing CO2 emissions, and their technological maturity. The second part assesses the feasibility of the measures regarding the conditions of a specific cement producing system. Aspects such as organizational applicability, technical and infrastructural applicability, and the existing level of implementation of each measure are considered.

The framework is also applied on three cement plants in Germany (owned by CEMEX) referred to as the Cluster West and the results of the assessment are summarized.

Conclusions

As demonstrated in the case of Cluster West, the assessment framework developed in this article can be used by a cement producing companies such as CEMEX in order to systematically assess hundreds of measures and identify the most feasible and applicable ones for implementing on each of their cement production plants.

Lessons learned during development of this assessment framework, may be used when approaching industrial systems other than cement production.

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.

Purpose

The 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 framework

To 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.

Results

The 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”.

Conclusions

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.

Cement is a vital and commonly used construction material that requires large amounts of resources and causes significant environmental impact. However, there are many different types of cement products, roughly ranging from traditional products with a rather linear production to more synergistic alternatives where byproducts are utilized to a large extent. Life Cycle Assessment (LCA) studies indicate the synergistic products are favorable from an environmental perspective.

This article has two main aims, where the first is to carry out a LCA and compare three different cement products, involving both linear and synergistic ones to further explore this issue. This has been done from cradle to gate, focusing on climate impact, where the case is a cement production cluster consisting of three plants in Germany. The second aim is to develop and test a simplified LCA model for this production cluster, with the intention to be able to assess additional production alternatives based on the information of a few parameters.

The more comprehensive LCA showed that cement products with a high share of byproducts, in this case granulated blast furnace slag from the steel industry, had the best climate performance. The difference between the best (CEM III/B) and worst (CEM I) cement product, regarding global warming potential, was about 66%. A simplified LCA model was developed and the research team could apply it to compare the present production with the situation in 1997 and also with possible future production systems. This simplified LCA model was based on 6 key performance indicators, instead of more than 50 parameters, which was the case for the comprehensive LCA model. For example, the simplified model showed that the CO₂ emission related to a virtual average product of the production cluster was reduced about 49 % in the period from 1997 to 2009.

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.

Svensk industri är känd för att använda stora mängder energi i sina processer. En stor del av energin kyls bort som restvärme. Exakt hur stor potential det finns när det gäller att ta tillvara restvärme är dock inte helt känt. Den här rapporten är en del av ett projekt, initierat av Länsstyrelserna i Östergötland och Örebro län, med syfte att kartlägga hur stor potential för tillvaratagande av restvärme det finns i de två länen. Syftet med den här rapporten är att beskriva miljöpåverkan från tillvaratagande av restvärme i fjärrvärmenät, dels generellt i förhållande till ett antal typfall och dels i förhållande till den potential som identifierats inom projektet. Rapporten är uppdelad i två delar, där den första delen bygger upp ett ramverk för hur miljöpåverkan per levererad MJ fjärrvärme varierar beroende på inblandning av restvärme i fjärrvärmeleveransen. I den andra delen används detta ramverk för att analysera potentiella förändringar i miljöpåverkan vid ökat utnyttjande av industriell restvärme enligt underlagsdata som tagits fram i ett annat delprojekt.