Modelling e-recycling systems

Materials World magazine
2 Nov 2010

A first-principles approach to modelling the efficiency of e-waste recycling systems may be available soon. The technique also links product design to materials liberation during recycling, enabling it to be used with CAD tools and allowing design engineers to perform design for recycling (DfR).

This ‘one size fits all’ method has been made possible, say engineers in The Netherlands and Australia, by taking a fundamental approach that investigates recycling technology from the perspective of its underlying physics, chemistry and thermodynamics. Unlike earlier work, they explain, the composition of liberated materials is not pre-defined, instead, it is predicted as a function of design choices and can vary accordingly.

Co-author of the research Dr Antoinette van Schaik at MARAS – Material Recycling and Sustainability, in Den Haag, The Netherlands, says, ‘The issue is how to harmonise product complexity, recycling system infrastructure, legislation and economics to maximise recovery. There is no patent answer here, but our approach provides the essential metrics to measure, control and improve recycling, as well as enhance designs in favour of recycling, on a first-principles basis.’

The modelling has been used in various industrial applications in the EU – the SuperLightCar (SLC) project managed by Volkswagen under the EU Sixth Framework; the shredding and separating of 1,153 vehicles, in an industrial trial managed by Auto Recycling Netherlands; and for waste electrical and electronic goods, such as CRT TV and refrigerator recycling in The Netherlands (see image below).

In the SLC project, the models have been applied to predict recycling/recovery rates and provide advice on preferred recycling concepts for the car’s multi-material design. In the TV and fridge application, the results include recycling/recovery rates of all the individual materials, prediction of the grades of the recycled products, and prediction and control of toxic or harmful elements in the recycling streams of those goods.

The research’s co-author, Professor Markus Reuter of the University of Melbourne, Australia, and Technical Director at minerals and metals processing specialists, Outotec, explains, ‘In the SLC setting, the models were linked to CAD software for DfR and to commercial lifecycle assessment software to provide detailed recycling knowledge for environmental assessment of designs.’


Material combinations

In a broader context, he says, ‘The modelling provides information on desired and undesired material use, material combinations, as well as preferred ways of connecting materials in view of recycling performance. It can support designers in making choices between different design alternatives, preferred material choices and/or combinations, including coatings.’

The research has been welcomed by Chris Howsam, Design Director at UK consultancy Hillside Design in Teignmouth. He says, ‘I think the research is worthwhile. But the research supposes that product designers have more control than is often the case – the accountants often have the last say.

‘I also think it could have gone on to explore the potential for an e-waste universal scoring system that would be a fundamental part of the consumers’ decision/buying process.’

Mark Wolle, Director of Triple ‘e’ Recycling in South Wales, UK, adds, ‘It shows the inefficiencies of dismantling, something we always manage empirically, so I think the model might be of use to a manufacturer.’

The engineers plan to make further refinements to the method. ‘Material liberation from complex products is still a difficult area and needs more fundamental research work,’ says van Schaik.

While it is often still the case to manage things empirically in recycling, Reuter comments, ‘These engineering and industry-based models are an attempt to place recycling on a more rigorous basis and link it to the rigour of the thermodynamics of high-temperature processing. We are trying to increase insight into system performance (including design, consumer behaviour, economics and dismantling) and attempting to show what has to be changed and how to maximise metal and material recycling. The objective is to inform policy in a structured manner to arrive at the best environmental, and also economic, outcomes.’