Why is this research needed?

Reducing carbon emissions in the steel and cement sector plays a crucial role in the UK Government’s aim to achieve Net-Zero target by 2050. Steel production is a notable source of greenhouse gas emissions, accounting for 14.2% of emissions in the manufacturing sector and 2.4% of the overall CO2 emissions in the UK. In addition, in 2021, the UK’s cement sector contributed to the release of 7.3 million tons of CO2 which is approximately 5% of the total CO2 emissions nationally. While it is feasible to achieve additional small-scale decreases in CO2 emissions by enhancing efficiency and switching fuels, the remarkable potential of Carbon Capture and Storage (CCS) technology lies in its ability to significantly reduce CO2 emissions across these two sectors. The common methods for capturing CO2 in cement and steel plants involved utilizing amine scrubbing at $84.1/t CO2 and oxy-combustion at $44.1/t CO2, which is approximately half the cost of MEA scrubbing. The implementation of calcium looping in the backend and integrated setups came to around $54.6/t CO2 and $59.7/t CO2, respectively [1]. However, in comparison to the stated methods, mineral carbonation emerges as a highly promising technology for reducing CO2 emissions, offering the dual advantage of emission reduction and the utilization of solid waste in the carbonation process to generate value-added products. Two pathways exist for the carbonation of alkali enriched wastes, comprising direct and IMC processes. IMC, among the two, showcases quicker reactions and enhanced effectiveness.

To the best of our knowledge, no published research is available on the IMC of industrial wastes in the UK’s steel and cement industries. This includes the recycling of consumable materials (acid and alkalis). The current investigation incorporated various innovative approaches to enhance the feasibility of the carbonation process and is in good accordance with the UK CCS landscape. The following benefits can be obtained by applying this project: (a) an economical alkaline raw material obtained from the cement and steel industries will be harnessed as a valuable source of Ca to promote successful carbonation, (b) the production of precious substances with economic feasibility throughout the pH fluctuation process will secure the financial efficiency of this carbon capture technique and (c) situating the carbonation procedure in a location where CO2 and alkaline by-products are easily accessible at the same time, from the discharges of cement and steel factories, offers another advantage of the suggested approach. Finally, the alleviation of soil and water pollution caused by waste release stands as an additional noteworthy advantage of this study.

The successful accomplishment of this project holds the potential to generate substantial opportunities for collaborative partnerships with the industry stakeholders, while also decreasing greenhouse gas emissions, specifically carbon dioxide, in both steel and cement sectors. The outcomes of the proposed project are exceedingly advantageous for forecasting the viability and upscaling of the IMC process for commercial utilization in the wastes of the cement and steel industries in the UK and globally. The results of this project serve as a foundation for significant funding applications from UKRI or other sources. Moreover, to support future endeavours, we are well-engaged with the steel and cement industries as the end beneficiaries. If this project scales up successfully, it could lead to increased job creation the waste-to-carbon mineralization supply chain for the next 5-10 years in the UK and abroad as well.

1. Strunge, T., P. Renforth, and M. Van der Spek, Towards a business case for CO2 mineralisation in the cement industry. Communications Earth & Environment, 2022. 3(1): p. 59.

What is this research investigating?

This project aims to utilize simultaneously produced alkaline waste and CO2 in steel and cement industries to generate sustainable, highly value-added materials and reduce GHG emissions and waste discharge. To achieve the aim of the project, the study includes four main objectives in order of priority as follows:

Objective 1. To study experimentally process of IMC (Indirect Mineral Carbonation) using cement and steel wastes
Objective 2. To analyse leachates and precipitations produced in the IMC process
Objective 3. To use the Design of Experiments (DoE) approach for acid leaching optimisation
Objective 4. To assess the techno-economic and environmental aspects of an integrated system from waste to carbonation

The following work packages (WP) have been considered to achieve this project’s aim and objectives:

WP 1. Experimental work on carbonation
This part should be read in conjunction with Fig.1 where the schematic diagram of the IMC process is given. The waste is first fed and reacted with the appropriate acid in one step, by which all the cations enter the liquid phase from the solid phase. After transferring the filtrate 1 to the pH-swing reactor, the cations extracted from the waste by the pH-swing process become solid and are separated from the solution phase by increasing the pH of the solution. On the other hand, the production of CO2 carriers is done by direct scrubbing of CO2 gas with an alkaline solution. At the final stage, the CO2 carrier solution produced is added to purified filtrate 2, which is free of iron and other mineral metals, so that the carbonation reaction occurs. In WP1, the IMC set-up at the laboratory scale will be delivered.

WP 2. Analysis of the produced materials
The chemical composition of the wastes and their derivatives produced during the carbonation process will be distinguished by X-ray Fluorescence (XRF). The mineral composition of the wastes and other produced materials will be determined using an X-ray Diffractometer (XRD). The inductively coupled plasma (ICP) mass spectrometry apparatus will analyse the elements’ concentration in leachate. Scanning Electron Microscopy (SEM) will be used to analyse the surface characteristics and morphology of the carbonated products. For measurement of CO2 concentration, a CO2 gas analyser will be used. The deliverables of WP2 is the full chemical and physical characterisation of the leachates and precipitations of the IMC process.

WP 3. Experimental design for IMC process optimisation
The IMC reactions happen very quickly because the carbonation and pH-swing steps are performed in the liquid phase. However, as in the extraction test, the reactions take place in the liquid-solid phase, DoE will be applied for the extraction stage which is considered the rate-determining step of the process. Therefore, the optimised parameters in terms of acid type, reaction time, acid concentration and temperature will be identified in this WP.

WP 4. Feasibility study of the whole proposed IMC process
In the current study, and for the first time, the environmental impacts of IMC of cement and steel industry wastes will be assessed by the Life Cycle Assessment (LCA) methodology. Furthermore, an economic investigation will be carried out to estimate the products’ pecuniary value and the initial investment’s cost compensation. The deliverable output of WP4 includes economic and LCA analysis of the IMC process.

What does the research hope to achieve?

This project aligns with the mission of UKCCSRC to facilitate the role of CCS in achieving the UK’s Net Zero goal by 2050. Furthermore, the project’s impact extends to both CCS and CCU processes, as it operates upstream of both.

The project addresses the simultaneous use of CO2 from industrial flue gases with current and future waste streams to unlock a vast stock of resources for low-carbon valuable materials. Moreover, this study also offers a significant benefit in preventing soil and water pollution caused by waste discharge in both steel and cement sectors and will have potentially significant environmental benefits.

The project involves collaboration between the University of Bradford, ArcelorMittal, CEMEX, and UCL. It strengthens ties between the PI at the University of Bradford, the industrial collaborators, the C4U project led by Professor Mahgerefteh in UCL, and the UKCCSRC. The PI, a member of the external advisory board of C4U since its inception, is well- versed in the steel industry challenges. The C4U project, sponsored by EU Horizon 2020, focuses on CO2 capture in the steel industry.

Stakeholders who can directly or indirectly benefit from conducting this project:

1. Policy Makers and UK government: The research findings offer valuable insights for optimising IMC in steel and cement industries, contributing to the UK government’s goal to reach Net-Zero by 2050. According to the Industrial Decarbonisation and Energy Efficiency Roadmap Action Plan, CCS is the key technology for reducing carbon emissions in the cement and steel industry. At present, there are no alternative technologies that match the decarbonisation potential of CCS in these two sectors.
2. Academia and Research Institutions: The project advances knowledge in carbon mineralization, facilitating further research and exploration in CCUS technologies. It strengthens the University of Bradford and the Chemical Engineering Program Research and Knowledge Transfer portfolio and supports the Continuing Professional Development of involved researchers. The outcomes will also be integrated into teaching materials, benefiting both undergraduate and postgraduate students.
3. ArcelorMittal and CEMEX: This research is particularly relevant to steel companies like ArcelorMittal, and cement company such as CEMEX emitting their CO2 into the atmosphere.
4. Business and Industry: The research enhances knowledge about feedstock selection and IMC methods to optimise the production of valuable carbonated materials and other oxides derived from waste components, reducing CO2 emissions in steel companies (e.g., Tata Steel, Liberty Steel Group, West Yorkshire Steel) similar to ArcelorMittal. It also supports cement companies (e.g., Heidelberg Materials, CRH PLC and Cemcor Ltd) similar to CEMEX. Overall, this supports global steel and cement sectors are involved in designing and operating Mineral Carbonation processes.
5. The UKCCSRC community: The project will enhance the knowledge of all partners and establish a strong scientific link between industrial sponsors and the UKCCSRC research community through dissemination of the work in regular UKCCSRC and Early Career Research conferences.
6. Society and the General Public: Last but not least, the research supports CCUS efficiently producing low-carbon valuable materials, preventing soil and water pollution from the release of waste materials and reducing greenhouse gas emissions for the UK population. Note that steel and cement industries contribute about £2.4bn and £18bn to the UK’s GDP, respectively. They are supporting almost 3.5m jobs. This project can further support job creation in the supply chain for waste-to-carbon mineralisation.