Life cycle assessment of the climate change impact of magnesium phosphate cements formulated with tundish deskulling waste compared to conventional cement

Sustainable Chemistry and Pharmacy 42 (2024) 101802 Available online 16 October 2024 2352-5541/© 2024 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Life cycle assessment of the climate change impact of magnesium phosphate cements formulated with tundish deskulling waste compared to conventional cement Anna Alfocea-Roig a , Amelie Müller b , c , Bernhard Steubing b , Sergio Huete-Hern´ andez a , Jessica Giro-Paloma a , Joan Formosa a , * a Departament de Ci` encia de Materials i Química Física, Universitat de Barcelona, Martí i Franqu` es 1-11, 08028, Barcelona, Spain b Institute of Environmental Sciences (CML), Leiden University, RA Leiden, 2300, the Netherlands c Flemish Institute for Technological Research (VITO), Boeretang 200, Mol, 2400, Belgium ARTICLE INFO Handling Editor: Borhane Mahjoub Keywords: Life cycle assessment Circular economy Refractory waste Tundish deskulling waste ABSTRACT Ordinary Portland cement (OPC) production significantly contributes to greenhouse gas emissions due to high resource consumption and CO 2 output. It is therefore imperative to investigate alternative cements, such as magnesium phosphate cement (MPC), as a potential solution. This study is based on Life Cycle Assessment (LCA) methodology, comparing OPC with alternative magnesium phosphate cements (MPC) developed at the laboratory scale. The novelty of this study considers two types of alternative cements that use two different sources of MgO: MPC-MgO, developed with pure MgO, and MPC-TUN, formulated using tundish deskulling waste from steelmaking industry. The evaluated functional units are 1 tonne of cement, 1 m 3 of cement paste, and 1 m 3 of mortar, all of them are designed for the same function, which is as non-structural precast elements. The study assesses climate change impacts under two future scenarios: 1) electricity decarbonisation in the background economy using projections from Integrated Assessment Models and 2) electricity decarbonisation and a fuel switch in the cement kilns. The results indicate that MPC-TUN exhibits a lower impact of climate change in terms of CO 2 emissions across all functional units and scenarios compared to the other materials. In the most ambitious climate scenario, MPC-TUN mortar exhibits 42% and 56% lower climate change impacts than OPC-CEM I and MPC-MgO mortars, respectively, demonstrating its potential as a more sustainable construction material. Although further research is needed on the applicability of MPC-TUN in construction, regulatory frameworks are advised to simplify barriers to expedite the adoption of sustainable alternative cements. 1. Introduction The construction sector, which provides the infrastructure needed for our society’s daily activities, is accountable for approximately 40% of the total natural resources utilized, and 40% of the total energy consumed by humans (Eberhardt et al., 2020; Gong et al., 2012). Additionally, the construction sector is responsible for generating approximately 40% of the total waste produced by * Corresponding author. E-mail address: [email protected] (J. Formosa). Contents lists available at ScienceDirect Sustainable Chemistry and Pharmacy journal homepage: www.elsevier.com/locate/scp https://doi.org/10.1016/j.scp.2024.101802 Received 29 July 2024; Received in revised form 1 October 2024; Accepted 10 October 2024 Sustainable Chemistry and Pharmacy 42 (2024) 101802 2 human activities (Gong et al., 2012). Given the high resource and waste intensity of this sector, it is essential to alter the trajectory of the construction sector to minimize the associated environmental impacts (Hossain and Poon, 2018). Cement, a fundamental and essential component in concrete, is a crucial material for the construction sector. Ordinary Portland cement (OPC) possesses various advantages, such as its affordability, mechanical properties, durability, and more (Valipour et al., 2014). Currently, conventional cement is a major contributor to climate change (Folliet and Milagros Rivas Saiz, 2017). Specifically, the cement industry is accountable for 8% of anthropogenic carbon dioxide (CO 2 ) emissions, primarily originating from two main contributions: the calcination process to obtain clinker and the energy consumption during manufacturing (Sousa et al., 2023). In response to the demand for OPC and its associated impact, the industrial community has established a roadmap to achieve Net Zero CO 2 emissions by 2050 (International Energy Agency, 2023; de Brito and Kurda, 2021; El-Dieb and Kanaan, 2018). This roadmap is based on the “Focus of the 5Cs”, which encourages collaboration throughout the entire value chain of “Clinker-Cement-Concrete-- Construction-(re)Carbonation” to realize climate neutrality in the industrial sector (Agrupaci´ on de fabricantes de cemento de Espa˜ na, 2021; CEMBUREAU, 2021). CEMBUREAU, the European Cement Association, has developed a roadmap for 2050 that outlines the opportunities and actions depicted in Fig. 1 (CEMBUREAU, 2021). The aim of this roadmap is to reduce the emissions along the value chain by 2030 by 30–40% compared to 1990 and to achieve carbon neutrality by 2050. Particularly, Fig. 1 outlines CO 2 emissions reductions for each 5C by 2030 and 2050, aiming to achieve zero CO 2 emissions per tonne of cement produced in 2050. These targets align with various policies of the European Union (EU), in line with the Paris Agreement’s objective of limiting the global temperature increase to well below 2 ◦C and striving to achieve 1.5 ◦C, as well as other agreements (Amanatidis, 2019; Anna Nilsson et al., 2020; Brugger et al., 2021). The successful achievement of these goals relies on the implementation of different regulations and policy frameworks, along with investments in technologies that are currently being undertaken at local, national, and international levels. When it comes to cement, there are conventional options available that utilize alternative materials such as blast furnace slag (BFS) from the steel industry and fly ash (FA) from coal-fired power plants, resulting in a lower clinker content. However, the replacement potential of these conventional substitution materials is limited in the future as the processes, of which they are by-products, are expected to decline in a future decarbonized economy (Font et al., 2020; Kermeli et al., 2019). Additionally, there are supplementary cementitious materials (SCM) options available, as well as other alternative binders (Kermeli et al., 2019). One such alternative binders is magnesium phosphate cement (MPC) (Formosa et al., 2012; Huete-Hern´ andez et al., 2021; Maldonado-Alameda et al., 2017). MPCs is produced by combining magnesium oxide (MgO), monopotassium phosphate (MKP, KH 2 PO 4 ), and water. In the last decades, circular economy has emerged as another mean to reach environmental sustainability, by minimizing material waste and maximizing material reuse at all stages of production and consumption(Ma et al., 2023). Utilizing waste as a raw material instead of extracting natural resources is an important strategy to reduce landfill waste and decrease the extraction of new natural resources. As a result, there is a growing body of research focused on developing alternative cements that utilize waste as a raw material, aligning with new environmental policies (Giro-Paloma et al., 2019; Huete-Hern´ andez et al., 2021; Maldonado-Alameda et al., 2018). This study compares magnesium phosphate cement (MPC) formulated with pure magnesium oxide (MPC-MgO) to MPC-TUN which uses refractory waste from the steel industry, specifically tundish deskulling waste (TUN), as a source of magnesium oxide. TUN is a refractory material used in the last metallurgical vessel through which liquid steel flows before being shaped (Formosa et al., 2012). Life cycle thinking is a valuable tool for addressing social, economic, and environmental challenges. To comprehensively examine the various impacts of conventional and alternative cements, a life cycle assessment (LCA) approach is necessary. LCA has been widely used to assess the environmental impacts throughout the life cycle of a product or system. Different approaches to LCAs exists, contingent upon the study’s objectives. Conventional LCA is structured around current environmental impacts derived from historical Fig. 1. CEMBUREAU 2050 roadmap related to the CO 2 savings for each 5C (adapted from (CEMBUREAU, 2021)). A. Alfocea-Roig et al. Sustainable Chemistry and Pharmacy 42 (2024) 101802 3 or present data, while prospective LCA (pLCA) is oriented towards future scenarios, considering potential alterations that may happen (Arvidsson et al., 2018). Hence, pLCA offers the opportunity to assess whether an alternative cement can be classified as sustainable or not considering future developments (Langkau et al., 2023; Mendoza Beltran et al., 2020; Sacchi et al., 2022). PLCA is particularly beneficial for evaluating the environmental performance of emerging materials that have not yet been widely implemented. The objective of this study is to compare the differences in current and potential future climate change impact and energy consumption by employing both conventional LCA and scenario-based pLCA for three cement types (OPC, MPC-MgO, and MPC-TUN) in the three essential formats (cement, cement paste, and mortar). Future changes are modelled by incorporating anticipated alterations in future electricity and heat usage within the processes of the evaluated materials. This research helps to understand and compare the emission reduction potential offered by innovative cements compared to conventional cements (Fig. 2), allowing environmental hotspots to be identified. It also provides valuable insights to guide the future development of sustainable materials in the cement industry. 2. Raw materials The environmental impact of conventional cement is compared to other types of cements for the application as cement, cement paste, and mortar, all of which have been prepared following the UNE EN 196-1 standard (Normalizaci´ on Espa˜ nola, 2018). The different products evaluated are. •OPC CEM I 52,5 R. •MPC formulated with pure MgO: MPC-MgO. •MPC formulated with TUN as MgO source: MPC-TUN. Clinker is the major component of OPC, simultaneously contributing the most to its emissions. The quantity of clinker used, and the types of materials employed are regulated by international standards, ensuring that cement is a standardized product that meets rigorous specifications for constructing durable structures with long lifetimes. Substituting clinker with alternative materials requires that the final product possesses similar mechanical and durability properties, as well as high availability. Rules and regulations play an important role in approving the introduction of new cements into this sector (Griffiths et al., 2023; Guo et al., 2024; Wang et al., 2021). MPC-TUN is at Technology Readiness Level 3 (TRL3), indicating that it is a laboratory-scale development and not yet a fully mature technology (Alfocea-Roig et al., 2023). On the other hand, OPC CEM I, and MPC-MgO are at TRL9 because they are currently commercially available cements. Previously, a preliminary study was conducted to evaluate the properties of MPC-TUN, and the results showed that it possesses the necessary qualities for construction applications (Alfocea-Roig et al., 2023). Therefore, this study assumes that MPC-TUN can be used commercially, enabling a comprehensive comparison and full-scale environmental assessment (Batuecas et al., 2021). 3. Methodology LCA is a tool utilized for analysing and assessing the environmental impacts of a product or service. By highlighting emission hotspots and comparing impacts between alternatives, the LCA methodology allows consumers and producers make more sustainable product choices. This study was conducted following four primary stages (Pryshlakivsky and Searcy, 2013). A. Goal and scope: This stage involves defining the main goal and determining the system boundary. B. Life cycle inventory (LCI): In the LCI stage, data collection and calculations are performed to quantify the input and output of materials and energy. Fig. 2. Advantages and disadvantages of OPC and alternative cements under investigation. A. Alfocea-Roig et al. Sustainable Chemistry and Pharmacy 42 (2024) 101802 4 C. Life cycle impact assessment (LCIA): During the LCIA stage, the potential environmental impact obtained from the LCI is evaluated. D. Interpretation: The interpretation stage involves drawing conclusions based on the environmental impacts while considering the previously established objectives. 3.1. Goal and scope The main goal of this study is to perform an LCA to compare the carbon footprint of different cements for construction applications. Consequently, the study aims to assess and compare the environmental impacts of OPC-CEM I, MPC-MgO, and MPC-TUN to identify the environmental hotspots. The functional unit serves to quantify the specific product characteristics and defines the functions to be analysed (Batuecas et al., 2021; Panesar et al., 2017). In this study, three functional units are examined: 1 tonne of cement (dry powder), 1 m 3 of cement paste, and 1 m 3 of mortar. Three basic components are evaluated to cover the many commercialization strategies of cement: it is marketed as dry cement, which functions as a binder (cement paste), or as mortar for non-structural precast element. Although all three functional units are considered for impact assessment, particular attention will be given to the results obtained for 1 m 3 of mortar, which is a mix of cement, sand, and water, since mortar is a versatile material widely used in the construction industry. However, the functional unit of 1 m 3 of mortar allows to standardize the comparison between different materials and to enhance understanding of their carbon footprint impact per volume unit for the same applicability, which is an approach used within the research field. The geographical context of the study is the European Union (EU), and the time horizon is 2020–2050. This attributional LCA study uses the Ecoinvent 3.9 cut-off database. The study adopts the Cradle-to-Gate system boundary. This system boundary considers the flow of materials, energy, and emissions from raw material extraction until manufacturing, excluding use and end of life. In addition, in this study, transport has not been considered, since it has been estimated that all materials are manufactured in the same location. It is important to note that the mixture design is tailored to the functional unit, resulting in different proportions of raw materials. However, despite the variations in proportions, all materials exhibit the essential properties to be applied by the same application. A fundamental prerequisite for materials intended for use in the construction industry is that they possess identical workability characteristics, among other requirements. Hence, the water/cement (W/C) ratio of these materials has been carefully adjusted to obtain a similar consistency during casting, i.e. moderate slump. 3.1.1. Future scenarios The conducted LCA takes a prospective approach, for which it focuses on the anticipated evolution of the heat supply in cement industry and worldwide transformations in the global electricity sector related to sustainable development (Georgiades et al., 2023; Maes et al., 2023; Müller et al., 2024). The scenario development and analysis in this study are explorative, as it seeks to answer the question of how the situation in this sector could change if this alternative were to be introduced. Currently, this possibility is considered as a future simulation, although it has not yet been established as mandatory compliance regulations for the coming years. The LCI is studied under policy scenarios for 2020, 2030 and 2050. Therefore, it is necessary to update and modify the Life Cycle Inventory database with respect to energy, efficiency, and other relevant factors based on these future pathways. Specifically, this study focuses on the changes in emissions from conventional and alternative cements resulting from the use of alternative fuels and alternative electricity supply. The scenarios selected for each type of cement are based on the energy vision 2050 studies (Brugger et al., 2021). Two types of scenarios were evaluated. 1. Electricity scenario Scenarios that consider only the evolution of electricity production in cement production and the wider economic background system (Mendoza Beltran et al., 2020). 2. Fuel and electricity scenario Combined modelling of the background electricity scenario with foreground scenarios concerning fuel switch, developed by the decision-maker conducting the LCA (International Energy Agency, 2021). Regarding the electricity scenario, this study considers multiple scenarios based on the Shared Socioeconomic Pathways (SSPs), which describe different potential future development pathways based on different assumptions about population, socio-economic conditions, energy use, and technology advancements (Riahi et al., 2017). Out of the five SSPs available, only SSP2 is considered in this study, as it represents a medium-level challenge for mitigation and adaptation, following the current development pathways (How ‘Shared Socioeconomic Pathways, 2018; Meinshausen et al., 2020). The Representative Concentration Pathways (RCPs) are used to describe various levels of GHG (greenhouse gas) emissions that could occur in the next century. In this study, the Integrated Assessment Model (IAM) REMIND (REgional Model of Investments and Development) is employed for the electricity scenario (Potsdam Institute for Climate Impact Research, 2023; REMIND, 2023). The different IAM pathways evaluated are as follows. •SSP2-Base (resulting in an increase of 3.5 ◦C by 2100): in this scenario, society and economic trends are projected based on historical developments, without considering any specific additional climate policy using the most recent projections of the European Commission and PRIMES (Price-induced market equilibrium system) projections, as the reference for energy consumption (Castillo et al., 2022). •SSP2-RCP1.9 (resulting in an increase of 1.5 ◦C by 2100): this scenario extrapolates society and economic trends from historical developments while aligning with the climate policy objectives outlined in the Paris Agreement. A. Alfocea-Roig et al. Sustainable Chemistry and Pharmacy 42 (2024) 101802 5 In addition to assessing the isolated influence of a decarbonized electricity system in the electricity scenarios, a second set of scenarios combines these with changes is future thermal fuels. In these joint scenarios, the same assumptions from REMIND for electricity are taken as in electricity scenario, and the fuel assumptions are presented in Table 1. It is important to highlight that in 2020 no alteration in the fuel mix has been accounted for, and the data solely encompasses the information from the preceding scenario (electricity scenario). Future fuel scenarios are considered by adapting fuel types from cement roadmaps and altering the fuel sources for the main sub-processes integrated into the database (Brugger et al., 2021; CEMBUREAU, 2021). In practice, it is assumed that the heat market is shared between cement manufacturing and the production of chemical reagents. Table 2 summarizes the combination of scenarios of this study. 3.2. Life cycle inventory analysis (LCI) 3.2.1. OPC-CEM I OPC CEM I is frequently used for structures, products, and pavements in areas with low concentrations of sulphate ions in groundwater or soil. Among all the OPC families, CEM has been selected, as it is suitable material to be used as a non-structural precast element. Its composition consists of 95 wt% of clinker and 5 wt% of gypsum (Real et al., 2021). Fig. 3 illustrates the raw materials used of OPC-CEM I and the MPC-cements for the different functional units evaluated in this study, which was conducted based on data from both the literature and laboratory studies (Niewiadomski et al., 2021). Furthermore, it is possible to observe the raw materials utilized, the material density, and the water/cement (W/C) ratio. Fig. 4 shows the flowchart to produce 1 m 3 of OPC mortar, with all steps passing through the stages of cement and cement paste and their respective functional units. It visually represents the different materials used in the cement mix and displays the various processes involved in obtaining clinker (95% of the total of OPC-CEM I). The main stages are. •The acquisition of raw materials, which primarily involves sourcing limestone and clay. •Quartering, grinding, and milling processes are employed to homogenize the raw materials and reduce their particle size. •Preheating and calcination are carried out to induce a series of reactions that result in the formation of clinker. 3.2.2. MPC-MgO MPC-MgO is conventionally produced using 22.85 wt% of pure MgO, and 77.15 wt% of MKP. Fig. 3 presents the raw materials of MPC-MgO for the different functional units examined. To achieve workability and consistency comparable to MPC-TUN, and considering the specific requirements and characteristics of the pure MgO used, a higher W/C ratio was selected than typically recommended in the literature (Ma et al., 2014; Meng et al., 2023). Additionally, the use of boric acid as a retarder was not required due to the different material requirements for the same application. Currently, magnesium oxide is obtained from the calcination of magnesite (MgCO 3 ), resulting in the generation of 1.55 tonnes of CO 2 per ton of MgO produced (Ellis Gartner A, 2018). The specific type of magnesium oxide used in the development of MPC is referred to as Dead-Burned Magnesia (DBM) or sintered magnesia. DBM is obtained through another high-temperature calcination of magnesium oxide at approximately 1500 ◦C, which consumes 6546 MJ per one tonne of DBM (Mathias, 2009). This calcination process ensures the desired chemical reactivity characterized by low reactivity MgO and reduces the specific surface area (An et al., 2018; Luong et al., 2018; Ruan and Unluer, 2016; Sinka et al., 2018). Fig. 5 shows the flowchart of the production of 1 m 3 of MPC-MgO mortar, including the MPC-MgO cement and cement paste stage. The flowchart includes the two-step calcination to obtain DBM and the other required materials (monopotassium phosphate, sand, and water). 3.2.3. MPC-TUN In this case, the magnesium oxide source is obtained from tundish deskulling waste (TUN), which is a waste derived from steel manufacturing. This study incorporates the conditioning process required to transform TUN into useable raw materials with the desired quality and particle size for its use as a cement component. Magnesitas Navarras, S.A., a company located in Navarra (Spain), has provided information on the TUN conditioning process, starting from when it is considered waste until it is revalued as a primary component of MPC-TUN. The conditioning process involves screening, grinding, magnetic separation, and mixing, which are observed in Fig. 6. Based on the data supplied by the companies, the conditioning process is approximated to consume 64 kWh per tonne of TUN. These companies focus their activity on the recovery of refractory material from all types of industrial furnaces, for this reason, it is estimated that the values provided are reliable. The other raw materials used in MPC, being commercial materials, do not require a conditioning process. MPC-TUN is produced by combining 60 wt% of TUN with 40 wt% of MKP (Alfocea-Roig et al., 2023). Additionally, 1 wt% of boric acid (HB) is added to the total solid weight to enhance workability and delay the setting time. Fig. 3 shows the MPC-TUN raw materials, revealing the ratios derived from previous laboratory-scale studies. The DIOPMA research group has Table 1 Heat fuel generation mix (Brugger et al., 2021; CEMBUREAU, 2021). Type 2030 (%) 2050 (%) Coal 30 0 Fuel oil 10 10 Biomass 30 50 Bio propane (GPL) 30 40 A. Alfocea-Roig et al. Sustainable Chemistry and Pharmacy 42 (2024) 101802 6 considerable expertise in this field, having devoted extensive years to the advancement of MPCs. It is essential to highlight that the collection of this data was difficult due to the low TLR of MPC-TUN. Particularly, data on the electricity consumption for an industrial-level conditioning of TUN was lacking and these gaps were filled with contains various assumptions. These data gaps have the potential to underestimate the ultimate results concerning the future production of this product. However, it is anticipated that the deviation from reality will be minimal, given that the assumptions have been carefully aligned with real-world conditions. Allocation involves assigning the input and/or output streams of a multifunctional process to the product system under evaluation (H. A. Aguirre-Villegas et al., 2012; Heijungs and Guin´ ee, 2007). In this case, allocation by cut-off is applied to divide the impacts of TUN between steel production and its later use in MPC-TUN. This means that the upstream impacts of TUN are counted towards steel, while the conditioning process to turn the TUN waste into a raw material is counted towards the cement life cycle (Turk et al., 2015). In other words, as depicted in Fig. 6, the TUN comes as a burden-free waste from the steel industry and is considered as a good after it undergoes conditioning, making it suitable for use as a magnesium source. 3.3. Life cycle impact assessment (LCIA) methods The outcomes of the LCA are dependent on the choices and assumptions made regarding the data and methods employed. The specific impact category considered is the same across in both scenarios, which is. •Climate change: Table 2 Overview of scenario combinations. Electricity sector projections Fuel mix projections Electricity BAU SSP2-Base (REMIND) – Electricity 1.5 ◦C SSP2-RCP1.9 (REMIND) – Electricity and fuel BAU SSP2-Base (REMIND) Heat fuel mix, see Table 1 Electricity and fuel 1.5 ◦C SSP2-RCP1.9 (REMIND) Heat fuel mix, see Table 1 BAU (Business as usual); SSP2-Base1.5 ◦C; SSP2-RCP1.9. Fig. 3. Raw materials used in the functional units of the evaluated materials (see Appendix A, Table A.1). Fig. 4. OPC-CEM I flowcharts of the functional units assessed (see Appendix A, Table A.1). A. Alfocea-Roig et al. Sustainable Chemistry and Pharmacy 42 (2024) 101802 7 o Global warming potential (GWP 100): this indicator quantifies the potential for global warming over a 100-year timeframe. The unit used is kg CO 2-eq . The used methods are part of the Environmental Footprint (EF) method family, which is the recommended impact assessment method family of the European Union (Fazio et al., 2018). Future research shall explore how the investigated materials contribute to non-climate-change related environmental impacts, such as abiotic resource depletion and acidification potential, PM2.5, among other impact indicators. However, the focus and scope of this study has focused solely on the impact of climate change, this approach is justified by the assumption that if a material does not exhibit favourable characteristics in terms of GHG emissions, its market viability is compromised from the outset. Therefore, this study is the first investigation to assess its environmental footprint and subsequently study its feasibility. 3.4. Results 3.4.1. Current impact Table 3 shows the results for cements, cement pastes and mortar for the year 2020, the starting year of the study. The slightly different values between SSP2-Base and SSP2-RCP1.9 can be explained by small modifications to the background electricity mix that have already been modelled in 2020 based on REMIND. The impact of mortars is lower compared to cement or cement pastes due to the different proportions and material dosages employed. Table 4 shows the impacts on climate change for all scenarios considered for each material and functional unit evaluated. 3.4.2. Electricity scenario Fig. 7 shows the climate change results for the electricity scenario for the different cements. In these scenarios, the electricity supply throughout the production processes of the cements has been replaced with the future projected electricity mix from the IAM REMIND. The electricity consumed in the mixing process of the three evaluated materials has been assumed to be uniform. It is shown that the environmental impact is lower when using MPC-TUN compared to the other materials for all cement applications studied: cement, Fig. 5. Flow diagrams of the MPC-MgO functional units evaluated (see Appendix A, Table A.1). Fig. 6. Flow diagrams of the MPC-TUN functional units evaluated (see Appendix A, Table A.1). A. Alfocea-Roig et al. Sustainable Chemistry and Pharmacy 42 (2024) 101802 8 cement paste and mortar. Conversely, MPC-MgO stands out as the material with the greatest environmental impact, higher than OPC. For OPC, the climate change impact stays almost constant over time despite a continuously cleaner electricity mix. This shows that electricity is only a minor driver for climate change for OPC, for which most impact stems from calcination and fuel combustion. Concerning the development over time in the electricity scenario, more impact reduction is achieved, as expected, in the 1.5Ccompliant scenario (SSP2-RCP1.9) than in the business as usual (SSP2-Base), which, however, also shows modest reductions. Focusing on the mortars in the SSP2-Base pathways in 2050, the following observations can be made for their climate change impact (Fig. 8). i) Clinker production is responsible for 82.8% of the impact of OPC-CEM I mortar. ii) For the MPC-MgO mortar, MKP production causes 60.2% of the impact, while 20.5% comes from MgO production. Additionally, 8.7% of the impact comes from the calcination process of magnesite, which is crucial for achieving the desired reactivity required for its use as a raw material. Table 3 Current impact in the year 2020. Table 4 Impacts of the different scenarios evaluated in the pLCA. A. Alfocea-Roig et al. Sustainable Chemistry and Pharmacy 42 (2024) 101802 9 iii) For MPC-TUN mortar, MKP causes 73.5% of the impact. More precisely, 35.7% is attributed to phosphoric acid, and 37.8% to potassium hydroxide. Additionally, 1.2% of the impact is attributed to HB, while 0.4% is associated with the TUN conditioning process. Moving forward to the SSP2-RCP1.9 pathway for the same year 2050, the following slight changes in impacts for the mortars can be observed. i) For the OPC-CEM I mortar, 83% of the impact still comes from the production of clinker. Fig. 7. Results for climate change category for electricity scenario. Fig. 8. Contributions of mortars to climate change impacts for the electricity scenario in the year 2050 (OPC, Ordinary Portland Cement; MgO, magnesium oxide; MKP, monopotassium phosphate; Cond. Process, conditioning process; HB, boric acid). A. Alfocea-Roig et al.