Recycling system flexibility: the fundamental solution to achieve high energy and material recovery quotas

Abstract

In order to investigate the feasibility of achieving the high material and energy recovery targets imposed by EU legislation for post-consumer goods, a fundamental material and energy recovery optimisation model has been developed. This model is used to analyze the total recycling system with the end-of-life treatment system for the car used as example to illustrate the developed principles. The model allows construction, evaluation and optimisation of different end-of-life vehicle (ELV) recovery and treatment scenarios based on a fundamental quality description of each of the flows in the system. This description makes it possible to include the physics of separation, post-shredder treatment (PST), feedstock recycling, metallurgical and thermal processings on a first principles manner in order to evaluate the system on a technical and recyclate quality basis. This fundamental description of recycling systems questions the results of life cycle assessment and similar approaches that cannot capture the physical quality of recyclates. Evaluation of various end-of-life-vehicle (ELV) processings, recovery and treatment scenarios, including (i) restricted optimisation according to the legislation and (ii) unrestricted by legislation but more market and technology driven, have shown the large negative impact on the overall recycling performance if restriction of the flexibility of processing options is too large. Flexibility of the ELV recovery and processing system permits achieving high material and energy recovery quotas (rates) (over 95%) with the use of feedstock recycling and energy recovery for organic containing fractions if they cannot be suitably physically separated. The imposed legislative restriction on the amount of material that can be directed to thermal processing for energy recovery forces the system to include additional post-shredder treatment, with the result that material and energy recovery quotas are significantly lower at 88–91%, hence creating complex waste fractions. It is interesting to note that these fundamental results support recent studies that propagate a more market driven and less quota driven system for ELV treatment. In view of complex innovative car designs it is essential that a balance is struck between feedstock recycling, physical separation, material and thermal recovery, due to the complex recyclates of possibly poor quality and economic value restricting processing. Therefore these results suggest that post-shredder treatment (PST) should be considered carefully before installing too much sophisticated separation technology in favour of energy recovery technology. PST should be attuned to future car designs and not to the present, since product complexity could make too much physical separation uneconomical. In essence, this paper argues that achieving high material and energy recovery quotas of de-polluted cars is possible if the limiting stipulation of 5 and 10% energy recovery (for 2006 and 2015, respectively) is dropped from legislation. This implies that legislation can impose high material and energy recovery quotas, but that the relevant amount of energy and material recovery should be left free to follow the dynamics of innovative product design and process operation (i.e. operational costs and market value of recyclates). Therefore the law should simply state: “ Material and energy recovery from an automobile should together reach a technological defendable maximum which implies that good business practice and the market should determine how much material and energy are recovered from the various material fractions respectively.” This should not be fixed by legislation. In addition, poor sampling statistics on data makes measurement of quotas difficult due to often lacking standard deviations, supporting such a conclusion further.