by Kathie McGregor
The pressure on companies to be more sustainable and environmentally sensitive grows stronger every year.
Now that governments are starting to legislate on industrial waste handling and disposal, it’s time for operations to look at ways to better manage waste and improve their environmental performance.
And as the move towards sustainability, circular economies and environmentally-friendly outcomes increases, there are also great opportunities that are technically, socially and financially feasible.
It won’t be news that stockpiling waste materials or storing them in landfill can create long-term environmental problems.
Often financial pressures and short-term outlooks create a scenario where stockpiling waste and residue materials is more cost-effective than treatment and further processing.
This has resulted in a culture where long-term environmental problems are often passed over for bottom line pressures.
A triple-bottom line approach has never been more critical, as more state and federal governments worldwide start to legislate on waste disposal in landfill. Rather than fall back on landfill or stockpiling, operations should seize opportunities for innovative processes to recycle and reduce waste.
Thanks to increasing societal and shareholder pressures, there needs to be a new approach to waste material handling and disposal.
In many instances, waste materials contain valuable components that can be recovered through additional processing.
Take the example of red mud.
Red mud is a residue material produced in the leaching of bauxite ore. It is typically disposed of as waste in large landfill dams. But red mud contains leftover valuable components, including soda and alumina.
In the past, extracting these leftover components would not have been feasible, because of the high costs involved to adapt your existing operation. But a new holistic process is now possible where you can recover and recycle valuable components back into the process.
This new process also results in a fused slag product of silica and calcium, which can be used in civil engineering applications.
New ways to capture value from processes — such as this holistic approach to extracting value from red mud — are a key way for operations to increase their sustainability efforts. The value extracted from waste can cover the cost of the extra processing required, as well as create new jobs in operations. Ultimately improving both financial and environmental outcomes.
As with red mud, the value contained in most e-waste materials can be recovered through high temperature processing.
The standard method is to use a high temperature to separate and recover the elements of interest in the waste material. This can be done by exploiting the physical properties of the elements of interest.
Examples of how high temperature processing can be used to recover valuable components include:
A copper-based metal phase is produced when the e-waste is heated and fused with a slag forming flux. This metal phase is a collector for these valuable components. These metals can then be recovered using conventional metallurgical operations including electro-refining and leaching of anode residue.
It’s possible to process intermediate metallurgical products — such as lead blast furnace slag — to recover the valuable products contained within. Through thermodynamic modelling and multi-scale experimentation, you can determine the process conditions required to recover zinc as a zinc fume using a conventional smelting and fuming operation.
The smelting of aluminium using the Hal Heroult process produces a residue material called spent pot lining. This is a graphite-based product infused with fluoride salts and cyanide.
CSIRO developed a smelting process to treat this material: the graphite is used as a fuel, the cyanide is destroyed at high temperatures and the fluoride salts are recovered and recycled. A slag chemistry was also designed and tested — this was environmentally inert and suitable for civil disposal.
In taking a comprehensive approach to testing, your organisation is able to develop:
At CSIRO, we provide assistance with lab testing and modelling, and we can go up to pilot-scale testing for a well-informed, risk-mitigated deployment.
We can test the feasibility of these and other processes in your organisation using high-temperature, multi-scale expertise and capability. We can also assist with initial conceptual studies using flowsheet and thermodynamic modelling.
Not only will high temperature processing improve your company’s approach to environmental consciousness (and the improvements to brand reputation that go with it), but extracting the value contained in residue materials results in increased employment, revenue and social standing.
By partnering with CSIRO to increase the sustainability of your processes, you’ll see:
The CSIRO Pyrometallurgical team are world leaders in developing new approaches to the smelting process. Contact the Minerals Process Optimisation team on +61 3 9545 8912 or email me, Kathie.Mcgregor@csiro.au to talk about how you can increase the sustainability of your operations and recover valuable components from waste through high-temperature processes.
Rwanda Green Fund, 2017 September 28. African Waste Management Experts Visit Rwanda E-Waste Recycling Facility – Rwanda Green Fund Investment. Retrieved from https://www.flickr.com/photos/127716409@N05/37330716506.