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Maximising value from waste materials

Posted by: Keirissa Lawson

June 6, 2018

by Kathie McGregor

How to perform value recovery from waste materials

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.

The current state of waste and stockpiling

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.

The opportunities for value recovery from waste materials

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.

Flow chart showing how soad and alumina are extracted from red mud using the Bayer process, smeltering and water leaching
Figure 1: The process of extracting valuable components from red mud

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.

Cost-effective approaches to value extraction

As with red mud, the value contained in most e-waste materials can be recovered through high temperature processing.

How is it done?

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:

  1. Recovering copper, gold, silver, platinum and palladium.

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. 

  1. Recovering zinc and geranium from slag.

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.

  1. Recovering valuable components from graphite residues.

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.

Pile of e-waste i.e. compter motherbiards and electronics components
Figure 2: Extracting value from e-waste reduces the amount that has to be stockpiled.

In taking a comprehensive approach to testing, your organisation is able to develop:

  • a combination of thermodynamic and flowsheet modelling to test ideas and concepts prior to experimental work
  • a techno-economic modelling capability to confirm the economics of a process or concept
  • the experimental capability at multi scale to test high temperature solutions
  • a multi-disciplinary capability — you gain expertise, facilities and collaboration with other leading research organisations and industry bodies.

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.

Partner with CSIRO to reap the benefits of high-temperature processes

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:

  • improved revenue by extracting value from undervalued waste and residue materials
  • improved environmental credentials through the treating and processing of stockpiled waste materials
  • improved outlook through the triple bottom line concept.

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.

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Sources

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.