Sustainability challenges across the value chain
The three-stage production chain of aluminium from ore to casting is complex and consumes huge amounts of energy and input materials. The process requires 13,000 to 18,000 kWh/t of electric energy under the best- and worst-case scenarios, and an average of 12 kgs of CO2eq is emitted per kg of aluminium smelting worldwide. This process also results in undesirable by-products, including bauxite tailings, bauxite residue, dross, spent pot lining, etc. Here is an illustration of the range of sustainability challenges aluminium faces across the value chain:
(Published in Light Metal Age, The Quest for Low Carbon Aluminum: Developing a Sustainability Index, 2021)
(Note: PFC: perfluorinated carbon compounds, POC: products of combustion)
Since electricity generation, consumption, and GHG emission remain the key interrelated challenges in this energy-intensive industry, the concept of sustainable aluminium has so far been zoomed into CO2eq emissions and the fuel that is used to generate electricity. This article throws light on a neglected area of sustainability – bauxite residue management – which can pose serious environmental and health hazards and have a detrimental impact on aluminium’s sustainability roadmap.
Bauxite residue needs immediate attention
Bauxite residue is a waste product produced during the extraction of alumina from bauxite through the Bayer process. Rich in iron and aluminium components, the composition of bauxite residue depends on the source and the extraction process.
Bauxite residue generation can vary from 0.3 to 2.5 tons per ton of alumina produced, depending on the quality of bauxite and extraction conditions, though typically, it lies between 1 and 1.5 tons. Before disposal, bauxite residue is washed to extract as much caustic soda and dissolved alumina as possible. After washing, the residue is disposed of in special facilities known as Bauxite Residue Disposal Areas (“BRDA”) or Residue Storage Areas (“RSA”). The usual practice allows storing bauxite residue in slurry form, but some alumina producers also practice dry disposal.
The stockpile and the risk
As per an estimate from the International Aluminium Institute (“IAI”), globally, the aluminium industry generated 159 million tons of bauxite residue in 2017, and there exists a global inventory of more than 3 billion tons. Metallurgical alumina production is forecasted to increase from 140 million tons in 2022 to 178 million tons by 2040. With the growing production of alumina, bauxite residue generation is likely to increase significantly. According to the IAI’s dynamic material flow model, bauxite residue production is likely to touch about 220 million tons per year and reach an inventory of seven to eight billion tons by 2050.
High alkalinity and high caustic content in bauxite residue cause environmental risk for fertile soil and groundwater contamination. The caustic soda or sodium hydroxide (“NaOH”) content in bauxite residue leads to human health risks. Moreover, disposal of bauxite residue requires a large area, which means loss of huge land and soil, which could otherwise be used for green cover or other vegetation. There have been instances in the past when the bauxite residue slurry was released into the surrounding environment and residential areas due to leakage in the red mud ponds causing loss and injury of life along with damaging soil and water bodies.
Bauxite residue management: industry practice
From this stockpile of bauxite residue that is generated every year, only about 2.5 to 5 million tonnes get recycled every year. About 3 million tonnes are utilised every year in the production of Portland Clinker Cement, according to IAI data. This is by far the most widely known use of bauxite residue globally.
Other than that, bauxite residues are also used for:
- brick production
- soil improvement
- landfill covering
- iron production
These are just experimental uses so far and the valorised volume is much lesser than the generated stockpile. The industry has not yet been able to find an environmentally and commercially viable solution for bauxite residue valorisation.
Case studies of bauxite residue valorisation
India’s Hindalco, part of the Aditya Birla Group, was the world’s first company to undertake a 100% red mud utilisation strategy in 2020. The company signed an agreement with UltraTech Cement, India’s largest cement manufacturer, to deliver 1.2 million tons of bauxite residue per year to be used as input materials.
UAE’s Emirates Global Aluminium (“EGA”) has begun constructing a pilot plant to convert bauxite residue into soil products that can be used to expand green cover and other purposes in the UAE.
Further, Hydro Alunorte recently signed a contract with Wave Aluminium to build a plant in Brazil to process bauxite residue, aiming to recover commercially valuable materials. The planned processing plant aims to process 50,000 tonnes of bauxite residue per year. The technology has been tried and tested on a laboratory scale.
Barriers to managing bauxite residue
One of the biggest bottlenecks in valorising bauxite residue within a market economy is economic viability. There is no dearth of technological options to manage bauxite residue. However, there is a much higher likelihood of any given utilisation pathway being pursued if it is economically viable along with being environmentally beneficial. Hence, the initiatives need policymakers’ support or monetary incentive.
Within aluminium, producers are already exploring a premium pricing structure for low-carbon aluminium, primarily based on electricity sourced from hydropower. Very few aluminium producers get access to hydropower and no new hydro dams are under construction for environmental reasons. The hydro-based premium does not apply to most global aluminium production. Hence, producers enjoying the benefits of a low-carbon aluminium premium already have the advantage of cheaper hydropower. Further, this is creating a barrier between traditionally known “green” and “black” aluminium, driving coal-powered aluminium producers toward the sustainability roadmap.
This raises the question of whether there should be premiums for other aspects considered sustainable within the aluminium market. Having a premium could incentivise the effective utilisation of newly produced and existing bauxite residue. A producer could claim a higher premium for the removal of problematic existing bauxite residue compared to a newly produced lot. The bauxite residue mitigation premiums could apply equitably to all primary aluminium producers using any fuel source. A premium based on higher bauxite residue utilisation would encourage producers to churn out primary aluminium adhering to low-bauxite residue requirements. It could act as a workable solution to deal with the necessary problem in the aluminium industry, needing an urgent and disruptive approach.
*The content covered within this article articulates the observations of Dr Subodh Das and is not reflective of the LME viewpoint*
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Dr Subodh Das
Dr Subodh Das is a globally recognised serial entrepreneur in manufacturing/industrial/ academic/technology-based organisations, founder and manager of several aluminium research consortia involving multi-disciplinary collaborations. He has spent 45+ years in the global aluminium supply chain from “mine to market” with diversified experiences, and in the manufacturing sector for 25 years with industry majors such as Alcoa and Logan Aluminium, a JV owned by Novelis and Tri-Arrows. He has academic expertise spanning eight years at the University of Kentucky, Lexington, Kentucky, USA. He is the founder of Secat, Inc.
Dr Das is currently managing Phinix, LLC, a high-impact entrepreneurial company serving global primary, fabrication, and scrap-based secondary aluminium and light metals industries, founded by him in 2008.