Bauxite Residue: Contributing to cement’s quest for circularity

Cement and aluminium are two of the most utilised materials in the global economy. Operating at this scale incurs significant challenges that can be alleviated through industrial symbiosis. The emphasis on implementing alternative options is more imperative than ever. Consumer scrutiny and increasingly constrained margins is bringing environmental, social and governance (ESG) considerations to the forefront of decision-making throughout materials value chains. Bauxite residue can help deliver on the cement industry’s circularity ambition.

In addition to contributing to the cement industry’s circularity ambitions, the integration of alternative raw materials has the potential to deliver on other environmental goals. The pathway to net zero emissions for a hard-to-abate sector such as cement, will require a multitude of changes to current operations. New kiln technologies, alternative fuel sources, chemical process advancement and the use of alternative raw materials are likely to be needed across the sector over the coming years.

Bauxite residue as an alternative raw material: Volumes, costs and propertie

Bauxite residue, the iron and aluminium by-product of alumina processing, can meet the needs as an alternative raw material in cement production due to its composition, volume, availability, cost effectiveness, and properties.

In 2021, approximately 165 million tonnes of bauxite residue were produced from the production of alumina, and this is set to grow (in line with growing aluminium demand). This means that bauxite residue supply will be abundant, whilst other alternative raw materials, typically used in cement formulations, such as slag and fly ash will conversely become scarcer.

Additionally, the cost of bauxite residue can be competitive, compared to other alternative raw material products utilised in cement formulations. Recent technological advancements and circularity values are also expediting this transition. The most immediate application of bauxite residue in cement is within Portland Cement Clinker (PCC) due to its reduced processing burden in comparison to Supplementary Cementitious Materials (SCM), although aluminium industry and EU backed research is making strides on the latter. When focusing on PCC, the main cost barriers are those incurred when switching, which requires minimal operational process changes but will vary depending on site specificities.

In certain situations, the properties of bauxite residue can positively impact the raw mix of PCC due to the rich iron and aluminium oxides that negate the need for conventional iron and alumina sources. This enables ratio adjustment of aluminium and iron oxides providing numerous benefits e.g., sulfate resistance in the clinker. There are traditional chemical and physical property challenges related to the addition of bauxite residue, notably alkalinity and moisture levels. Nevertheless, the more widespread use of press filters or mud farming when processing bauxite residue produces a material with a lower alkali content and lower moisture. Meanwhile additional processing such as dealkalising bauxite residue is expected to result in improved products for use in PCC, whilst calcination with other additives is expected to provide an effective SCM.

Case studies and examples
It is estimated that 3 million tonnes of bauxite residue are annually used in the production of PCC. Bauxite residue in clinker production is already occurring internationally in Belarus, China, Cyprus, Georgia, Greece, India, Moldova, Russia, and Ukraine.

Some specific examples are reviewed in Table 1 below and proximity of bauxite residue producers in relation to cement manufacturers in India is depicted within Figure 1.

Some specific examples are reviewed in Table 1 below and proximity of bauxite residue producers in relation to cement manufacturers in India is depicted within Figure 1.

Table 1. Country overview for utilisation of Bauxite Residue in Cement, IAI

	Mykolayiv	Mytilineos	Hindalco
Country	Ukraine	Greece	India
Maximum Usage (ktpa)	250	85	2000
Max Distance to Cement Plant (km)	~1200	1200	1100
Processing and Other Considerations	Residue is blended by producer for consistency and solar drying to reduce moisture content	Residue is press filtered and solar dried by producer to reduce moisture content. It is used as a clinker raw meal substitute in levels between 1.5-3.0 % wt.	Residue is press filtered by producer to reduce moisture content. Bauxite Residue used in PCC as a replacement for laterite, Lithomarge, and sub-grade bauxite
Typical Chemical Properties	15 % Al2O3, 47 % Fe2O3, 3.3 % Na2O	15 % Al2O3, 42 % Fe2O3, 7 % SiO2, 12.5 % CaO, 6 % TiO2, and 3 % Na2O	8% SiO2, 17% Al2O3, 39% Fe2O3

In a bid to promote the circular economy, the Aditya Birla Group has had two flagship companies: Hindalco and UltraTech enter into a Memorandum of Understanding and in 2020 1.2 million metric tonnes of bauxite residue was used across UltraTech’s 14 plants located across seven Indian states.

Figure 1. Depicting the proximity of Alumina plants (red) to Cement Manufacturers (yellow)

Next Steps: Want to find a local bauxite residue producer?
Bauxite residue, like cement, is produced globally. The main bauxite residue producing areas/countries include China, Brazil, India, Europe, Australia, Canada, Jamaica, and the Middle East. If you want to be involved, or explore how bauxite residue can be used at your cement plant, please visit the International Aluminium Website https://international-aluminium.org/ to find:

• The International Aluminium Institute’s (IAI) Roadmap for bauxite residue use in cement
• Factsheets on bauxite residue and spent pot lining, two industry by products that can be used in cement
• Information on where bauxite residue is currently generated and may be available
• Tools to evaluate how bauxite residue measures up against current mix parameters
• Guidance on what questions to ask producers and how to switch at your plant
• More details about bauxite residue, in-depth case studies and information on projects occurring to advance the implementation of bauxite residue in cement such as:
  
  • EU funded projects investigating bauxite residue to be used as Supplementary Cementitious Material (SCM)
  • Bauxite residue in cement and leaching
  • Transportation of bauxite residue by sea and land
  • Relevant published literature demonstrating bauxite residue application
• Our social media links to stay up to date with the latest bauxite residue news and experiences

Acknowledgements: Research leading to these results has received funding from the European Community’s Horizon 2020 Programme (H2020/2014–2019) under Grant Agreement No. 776469 (REMOVAL). This publication reflects only the author’s view, exempting the Community from any liability. Project website: https://www.removal-project.com/