VITO is developing a unique, smart characterisation method for SUEZ, a well-known waste and raw materials company, which is able to fully analyse a seemingly homogeneous waste flow ‘on the fly’. The technology, which is currently being scaled up to an industrial level, allows for the valorisation of the last remaining residues from bottom ashes.

‘The problem with waste streams is that we often don’t know what’s in them,’ says Karen De Boeck, Business Development Director at waste and resources company SUEZ Recycling & Recovery Belgium. ‘And what we don’t know about, we can’t extract.’ This is certainly the case with what are known as bottom ashes, visually homogeneous residues left behind after the incineration of all kinds of waste streams, including household, industrial and construction waste.

Nonetheless, bottom ashes have been processed into aggregates for quite some time, in a process in which metals are recovered as much as possible. Originally, this was only done for the very coarse fraction of the metals, but today, valuable non-ferrous metals such as copper and aluminium are also being extracted from these bottom ashes with a grain size smaller than 20 millimetres.

There are other useful materials in fine bottom ashes too, such as precious minerals and metals. In recent years, SUEZ has developed a technology for the recovery of particles as small as one-tenth of a millimetre. But without knowledge of the exact content of these waste streams, waste processing essentially depends upon craftsmanship and experience. De Boeck: ‘We now process ultra-fine metal streams from bottom ashes without knowing their exact composition in advance. That means it takes a great deal of knowledge and expertise to make a usable raw material for an end user. In recent years, it has become clear that digital technologies can help us in this respect.’ 

The idea for a technology that could characterise a seemingly homogeneous (but in reality very heterogeneous) waste stream in its entirety and in real-time was born in 2014. Whilst the waste particles are passing on a conveyor belt in a processing plant, the characterisation would happen without any disturbance - ‘on the fly’ - in jargon. This is very different from the current approach, in which sample-taking and analysis takes a lot of time and money, and is also only a limited representation of the waste stream. The idea evolved into a project supported by Flemish funds (coming from the Environment and Energy Technology Innovation Platform MIP within VLAIO) and called Characterise-to-Sort (CtS). In the years that followed, it was further developed as a Proof of Concept (PoC) in collaboration with VITO, which has a wealth of relevant knowledge and expertise in the field of sustainable materials management.

Digital twin of the waste stream

Kris Broos was involved in the project from day one. He and Roeland Geurts, along with other VITO researchers, devised the core of the characterisation technology, which can predict exactly what a waste flow contains. ‘We wanted a technology that looks directly at the entire flow without disrupting it and identifying each individual particle,’ Broos says. ‘This allows to generate knowledge that’s immediately available and therefore doesn’t come too late, as with traditional sample collection.’

This core consists of three different imaging techniques: a colour camera, a 3D camera and an X-ray sensor – to determine the colour, the shape and the internal chemical structure of each waste particle respectively. The particles are characterised by hundreds of different measured parameters, of which size, shape, chemical structure and mass are among the most important. The measurement results are immediately uploaded to a computer model that uses them to create a so-called digital twin of the waste stream. ‘This virtual representation allows for virtual experimentation with the waste stream. In addition, we use AI techniques such as machine learning to make even better predictions,’ says Roeland Geurts. The digital twin enables well-founded decisions. ‘Hence, the processing procedure can be continuously and automatically adjusted and streamlined. Later on, based on the digital twin, the sorting will also be able to take place autonomously.’

With this kind of ‘smart’ waste processing, the outflow properties (the composition of the recovered materials, their quality, etc.) of the process can be continuously predicted. This can significantly improve the recycling of bottom ashes and their derived streams, as well as the quality of any end products.  ‘This is actually about much more than a characterisation technology,’ says Karen De Boeck. ‘We’re leading the recycling of bottom ashes ‘out of the dark’ as it were. Soon, we won’t have to process blindly anymore and we’ll be able to inform our customers thoroughly about the quality of the recovered materials.’

Recovering valuable materials and using less energy

‘Six years ago, we could never have imagined that we’d end up doing this at the level of individual particles,’ says Peter Segers, business development & innovation manager at SUEZ Belgium. ‘Sensors for characterising waste have been used for a long time. But characterisation based on not one, not two, but three different scanning techniques is the future, especially if you can see straight through materials and even determine their chemistry.’

Segers sees the development of this characterisation technology as the result of two parties daring to look beyond their own company walls. ‘By sitting around the table with us, VITO has gained new insights into the importance of knowing certain parameters in waste processing, for example. In turn, it’s made us think about how we can adapt our operational processes and possibly even our commercial activities based on this new characterisation technology.’

The project is providing both sides of the collaboration a deepening of expertise and business opportunities. The initiative grew in recent years from a PoC into a labscale research project called INSTAnT, which just like CtS is being supported by the Flemish government (via VLAIO within the ERA-MIN2 framework). Segers: ‘At ValoMET, our centre of excellence in Ghent, we’ll also be able to start applying the characterisation technology to other material flows.’

For VITO, the further development of this technology could then potentially lead to market valorisation in the form of a spin-off. But first and foremost, it is the environment that gains. ‘By adding value to end-of-life waste streams, not only are valuable materials recovered and value created, but we’re also reducing Europe’s dependence on primary raw materials,’ says Broos. ‘If you’re also aware that recovering aluminium, for example, requires 95 % less energy than primary production from bauxite, then every kilo is worthwhile,’ adds Karen De Boeck. ‘And on top of that, you can reduce the amount of landfilled materials. The environmental gain is therefore fourfold,’ says Broos.

Scaling up the technology in the CHARAMBA project

In recent years, SUEZ and VITO have proven that the characterisation technology for bottom ashes works. Now, the challenge is to scale it up to an industrial level. Or to stay in the world of waste management: from the level of the waste bin to that of the waste truck. ‘The characterisation needs to take place on a conveyor belt that moves at a realistic, industrial speed,’ says Liesbet Van den Abeele of VITO. ‘So the sensors need to be able to measure fast enough and the software and algorithms need to be able to process all the measurements within a few seconds. Furthermore, the technology must be able to fi t into an industrial process that runs non-stop and practically around the clock.’

The scale-up is part of a two-year project called CHARAMBA. It is supported by European funds from the EIT Raw Materials. This is part of the European innovation policy that helps technology bridge the dreaded valley of death. Van den Abeele: ‘With this support mechanism, EIT Raw Materials aims to support good ideas and innovations and bring them to market. In order to support only the most promising technologies, companies have to contribute a large part of the project funding themselves.’ In addition to SUEZ and VITO, Ghent University and materials and recycling company Umicore are also involved as partners in CHARAMBA.

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