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.

In this paper, we present an overview of interdisciplinary research from Ph.D. students working at the Division of Environmental Technology and Management at Linköping University, Sweden. Each of the Ph.D. students addresses the overall challenge of sustainability transitions in their research, although the themes and content of research varies considerably between individuals, encompassing research on actors, networks, products, materials, services and systems from the public and private sector, operating locally, regionally, nationally and internationally. The scientific literature and methods used to frame and conduct studies varies considerably within the group, as does the individual focus on immediate issues of sustainability.

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 research is an attempt to create a comprehensive assessment framework for identifying and assessing potential improvement options of cement production systems.

From an environmental systems analysis perspective, this study provides both an empirical account and a methodological approach for quantifying the CO₂ footprint of a cement production system. An attributional Life Cycle Assessment (LCA) is performed to analyze the CO₂ footprint of several products of a cement production system in Germany which consists of three dierent plants. Based on the results of the LCA study, six key performance indicators are dened as the basis for a simplied LCA model. This model is used to quantify the CO₂ footprint of dierent versions of the cement production system.

In order to identify potential improvement options, a framework for Multi-Criteria Assessment (MCA) is developed. The search and classication guideline of this framework is based on the concepts of Cleaner Production, Industrial Ecology, and Industrial Symbiosis. It allows systematic identication and classication of potential improvement options. In addition, it can be used for feasibility and applicability evaluation of dierent options. This MCA is applied both on a generic level, reecting the future landscape of the industry, and on a production organization level re ecting the most applicable possibilities for change. Based on this assessment a few appropriate futureoriented scenarios for the studied cement production system are constructed. The simplied LCA model is used to quantify the CO₂ footprint of the production system for each scenario.

By integrating Life Cycle Assessment and Multi-Criteria Assessment approaches, this study provides a comprehensive assessment method for identifying suitable industrial developments and quantifying the CO₂ footprint improvements that might be achieved by their implementation.

The results of this study emphasis, although by utilizing alternative fuels and more ecient production facility, it is possible to improve the CO₂ footprint of clinker, radical improvements can be achieved on the portfolio level. Compared to Portland cement, very high reduction of CO₂ footprint can be achieved if clinker is replaced with low carbon alternatives, such as Granulated Blast Furnace Slag (GBFS) which are the by-products of other  industrial production. Benchmarking a cement production system by its portfolio product is therefore a more reasonable approach, compared to focusing on the performance of its clinker production.

This study showed that Industrial Symbiosis, that is, over the fence initiatives for material and energy exchanges and collaboration with nontraditional partners, are relevant to cement industry. However, the contingent nature of these strategies should always be noted, because the mere exercise of such activities may not lead to a more resource ecient production system. Therefore, in search for potential improvements, it is important to keep the search horizon as wide as possible, however, assess the potential improvements in each particular case. The comprehensive framework developed and applied in this research is an attempt in this direction.