How CO2 is being used to treat bauxite
Gladstone Port - Photo credit, JooJoo41 & Free Images - Pixabay
Welcome to the twenty-sixth edition of my weekly blog where I take a closer look at the policies adopted by individual countries in their efforts to meet the requirements of the Paris Agreement. Particular attention is paid to the role that Carbon Capture, Utilisation, and Storage (CCUS) research and technologies are playing in the drive to meet these requirements.
This week I take a look at how advances in carbon capture and utilization technologies are being used in the treatment of bauxite, a by-product of the production of aluminium.
Aluminum Production Process
Before we look at how CO2 is used to treat bauxite, a good starting pointing is to explain the steps taken to produce aluminum as simply as possible. Bauxite ore is a red mud that is found in abundance in certain parts of the World such as Western Australia, Ghana, and the Caribbean. The starting point is to extract this red mud out of the ground and load a truck with 4 tonnes worth of bauxite ore. The bauxite ore is transported to an Aluminium refinery where it is refined. For every 4 tonnes of bauxite, 2 tonnes of aluminium oxide (alumina) is yielded. Alumina is a white powder substance (sand-like). The 2 tonnes of alumina is then smelted in large pots and 1 ton of aluminium is produced.
Bauxite Residue Carbonation
Bauxite residue is a byproduct of the refining process, it is also known as ‘red mud’ due to the high concentration of iron. The bauxite residue is stored in an area called Bauxite Residue Disposal Area (BRDA) where it must meet with environmental regulations. Bauxite residue carbonation is a process where CO2 is added to the bauxite residue which helps reduce the alkalinity of the slurry and help with regulatory compliance. An additional benefit of this is it can reduce closure and reclamation costs at aluminium mines.
Alcoa is the largest producer of aluminium in the world, satisfying 80% of the global market through its refineries in Brazil, USA, Spain and Australia. Alcoa also holds a 25% stake in a joint venture at a Saudi Arabian refinery. Alcoa developed a bauxite residue carbonation technology at its centre of excellence located at the Kwinana refinery in Western Australia. The technology created treats the high alkaline by-product in the slurry and reduces the PH levels from 13 to a less hazardous level. Research conducted by Alcoa has highlighted the potential of this technology to reduce the costs of managing tailing ponds. Waste by-product is stored in such ponds.
As demonstrated over the previous weeks and months of this blog, CO2 can be put to multiple positive uses across a variety of heavy industries. Bauxite treatment during the production of aluminium is another use for CO2 and is already operating on a commercial scale at industry leaders such as Alcoa. The challenge now is to find more innovative ways of using CO2 as we look to mitigate the impact of CO2 emissions overall.
Next week’s blog will profile Portugal and their efforts to meet their CO2 emissions reduction targets.