Finding a new use for a by-product of aluminium production.
In Canada’s Quebec region, a by-product of aluminium production is helping local farmers correct soil acidity and provide the nutrients their crops need.
The product, CHAC, offers local farmers a lower-cost local soil treatment, while also finding use for a waste material.
Making the most of waste
It’s one example of the work our scientists and engineers are doing to create new products from the waste created when producing minerals and metals.
CHAC is a by-product of making anodes, carbon rods that carry an electric current and create the chemical reaction needed to turn alumina into liquid aluminium.
Anodes are essential to making aluminium, but their production creates a waste gas, sulphur dioxide, that can be harmful to people’s health and the environment.
To prevent the sulphur dioxide being released into the air, special filters called scrubbers capture and “clean” potentially harmful emissions, like gas and dust.
Normally the scrubbing process involves adding a mix of different materials to the gas to create a solid, which is then carefully treated and stored as landfill. Instead, our scientists developed a patented process to combine lime with the sulphur dioxide, causing a chemical reaction that creates CHAC – a safe and effective soil treatment.
Around 17,000 tonnes of CHAC is recycled every year for use in construction and industrial applications. While we have more work to do to remove all waste from our operations, products like CHAC are helping us reduce our impact.
“Giving a second or third life to a material is the way we need to work for the future,” says François, Manager, By-Product Valorisation.
“If we don't move forward in this way, and if we don't change our way of doing things, we will exhaust our resources.”
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