“JNARDDC has formulated guidelines for Dry Stacking of red mud to reduce the disposal problem. Dry stacking is the most popular and the best practice till now, followed by alumina refineries worldwide," Dr Anupam Agnihotri, Director of JNARDDC
Dr Anupam Agnihotri, Director of Jawaharlal Nehru Aluminium Research Development and Design Centre (JNARDDC), Nagpur, India, has willingly participated in our e-Magazine: 'Recycling - Reshaping the future of the Aluminium Value Chain' to share his knowledge on red mud recycling. He has spoken about the best recycling practices for red mud and the industry-trend applications of the by-product. He has also suggested the red mud disposal processes that would have lesser impacts on the environment. Dr Agnihotri is a Metallurgical Engineer from IIT Kanpur with PG Degree in Metallurgical Engineering from the Visvesvaraya National Institute of Technology, Nagpur.
Jawaharlal Nehru Aluminium Research Development and Design Centre (JNARDDC) is a "Centre of Excellence" set up in 1989 to make contributions to the technological growth of the Indian Aluminium Industry. The centre has well-established R&D facilities for bauxite, alumina and aluminium. Currently, the institute is highly focused on promoting aluminium recycling to usher in environmental sustainability.
AL Circle: What processes are commonly followed for red mud recycling worldwide?
Anupam Agnihotri: The processes commonly followed for red mud utilization/recycling are:
| Product from red mud | Current utilization rate, million tonne/annum | Potential utilization tonne/annum |
| Additive/raw cement plants material to | 1.0 - 1.5 | 100% red mud can be consumed. Today's annual global cement production has reached 2.8 billion tonnes, i.e. 140 Mt of BR a year is merely 5% of current annual cement production. |
| Additive/raw material to iron and steel plants | 0.2 -1.2 | Today's annual global pig iron production has reached 1.1 billion tonnes, needing about 1.8 BT of iron ore with Fe 65%. Thus 100% red mud will be consumed to make 3% of total pig iron production. |
| Direct iron technologies reduction | - | Potentially attractive technologies after mastering |
| Sc and REE extraction | - | Promising Pilot plant trials are in progress |
| Building materials (bricks) | 0.5-1.0 | Use the sand separated from red mud (China) |
| Sorbent, coagulant, fertilizer, pigment, catalyst, ceramics, environm. appl. | 0.3 | Relatively small utilization volume, depending on local conditions |
| Total | 2.0 - 4.0 |
AL Circle: What are the major environmental challenges associated with red mud disposal? Are there any potential uses or applications of red mud that could help mitigate the environmental impacts?
Anupam Agnihotri: The generation of red mud mainly depends on two factors, the bauxite quality and the process parameters. The generation of red mud will be lower from good-quality bauxite in terms of higher alumina content and suitable digestion technology, whereas the same will be higher with low-quality bauxite and inferior digestion technology. Depending on the same, 1.0 – 1.5 tonnes of red mud is yielded per tonne of alumina. Presently, approximately 9 million tonnes per annum of red mud is generated by various alumina plants in India, and that across the world is above 150 million tonnes per annum. These figures are likely to be increased further with the setting up of new alumina refineries and decreasing bauxite quality in India as well as the world. The most important environmental impact arising from red mud disposal is mainly the pollution of soil and water caused by the residue suspension fluid. The major challenges are:
- Problem of large land requirement and its cost
- Seepage of alkali water into neighbouring soil, underground water, and water supply streams or canals
- Overflow of mud slurry, especially during rainy seasons
- Chances of dyke/dam burst due to excessive load in the mud lake or due to local seismic activity
- Airborne dust carrying fine-sized brown particles which contain caustic and cause air pollution/aesthetic damage
- Dyke maintenance cost
- Damage to the flora and fauna in the neighbourhood
The potential uses or applications of red mud that could help mitigate the environmental impact s:
- The red mud can be used in manufacturing value-added products in an environmentally sound manner.
- Red mud is used to make cement in factories in China, Ukraine, India, Russia, Georgia, Moldova and Greece. It is increasingly being used to produce cement when used for the manufacturing of construction and building products. Nearly all of the red mud produced each year can currently be used.
- Apart from manufacturing value-added products, the red mud can be used for bauxite residue farming techniques. Soda and moisture level reduction of bauxite residue slurry can also be achieved using bauxite residue farming. The objectives of this technology are to achieve both a low moisture level and pH of less than 11.5, which makes the farmed bauxite residue (farmed BR) non-hazardous.
AL Circle: What role is JNARDDC playing in promoting red mud recycling in India, and what message is it delivering to the world?
Anupam Agnihotri: JNARDDC has formulated guidelines for Dry Stacking of red mud to reduce the disposal problem. Dry stacking is the most popular and the best practice till now, followed by alumina refineries worldwide. It reduces the potential leakage of caustic liquor into the surrounding environment as most of it will be recovered. In addition, dry stacking is beneficial in terms of moisture reduction, leading to ease and reduced cost of transportation. The filtration reduces the moisture content to around 22- 25%, thus recovering the valuable caustic soda from the red mud. By using this method, a much larger volume of red mud can be stored in the same area, requiring less land area, levees, dykes or dams. When sufficiently thickened, red mud will not readily re-slurry, so rainfall will run off the surface, permitting atmospheric drying and aiding consolidation. The higher solid concentration allows more processed liquor to return to the refinery, and red mud can be transported easily for recycling/ reuse.
Draft Guidelines for the utilisation of red mud (bauxite residue) in the Cement Industry have also been formulated by JNARDDC. For promoting the circular economy in the Primary Aluminium sector, NITI AAYOG has advised “Mandating use of red mud in the cement industry” under regulatory and monitorable Circular Economy Actions. The aluminium industry shall practice this guideline to facilitate the utilization of red mud in the cement industry.
Besides, projects related to the following areas have been carried out by JNARDDC to promote red mud reuse/recycling in India:
- Asia Pacific (AP7) project on clean technologies: Utilisation of Red Mud for bricks, Tiles, foam Bricks, gravels
- Guidelines for safe disposal of Red Mud
- Glass ceramic tiles with red mud as base material
- Lightweight Foamed bricks (LWFBs) utilizing red mud
- International/National Status of Red Mud production & Utilisation
- Red mud blocks to prevent east coastal erosion
- Extraction of REE from Red Mud
- Geopolymer bricks from Red Mud
- Nano red mud for enhancing pozzolanic activity
- Zero waste concept for Red Mud Utilization
- Red mud remediation by vegetation
- Technology Development for Holistic Utilization of Red Mud for Extraction of Metallic Value & Residue Utilization
AL Circle: What measures are you taking to reduce carbon emissions from red mud recycling?
Anupam Agnihotri: There is nothing like carbon emissions in red mud recycling but some studies related to carbon dioxide sequestration in red mud have been carried out. By mixing carbon dioxide into the bauxite residue, the compound’s pH level can be reduced to levels normally found in alkaline soil.
AL Circle: How much red mud is generated from China, the world's largest alumina producer? What percentage does the country recycle?
Anupam Agnihotri: More than 70 million tonnes of red mud is produced annually in China. As per literature, there are still no cost-effective integrated technologies for the comprehensive recycling of red mud applied on a large industrial scale.
AL Circle: If the utilisation rate of red mud in the world is 15%, how are you trying to optimise it?
Anupam Agnihotri: Inherent moisture, alkaline & hygroscopic characteristics make red mud moist, sticky, and difficult to handle. To overcome these associated problems, the industry must go for a dry disposal system that can reduce these problems to a certain extent. Technical and economic suitability are the most important things to investigate for the utilization of any waste. Red mud properties should be altered and made marketable to utilize. The aluminum industry must start looking at how the requirement of the concerned industry can be met. The cost of transportation of red mud to the utilizing industry should be mutually decided as the transportation cost may be more than that of red mud disposal cost. The concerns of both sides (the alumina and utilizing industry) must be properly addressed, and the best solution should be implemented.
AL Circle: Can you share any success stories or best practices from industries that have effectively integrated sustainable red mud management practices?
Anupam Agnihotri:
- Dry stacking is the most popular and currently the best practice, which is being followed by alumina refineries worldwide. It reduces the potential leakage of caustic liquor into the surrounding environment as most of it will be recovered.
- Dry stacking is beneficial in terms of moisture reduction and can reduce the cost of transportation.
- Utilization of red mud in cement industries is one of the ways for sustainable red mud management practice
- Bauxite residue farming practiced at the Aughinish refinery in Ireland can achieve a final
‘Farmed BR’ with a moisture content of 25-28% and pH of less than 11.5.
A variant of bauxite residue farming using sea water neutralization is implemented in Eastern Australia.
