A methodical approach for the assessment of waste sorting plants

Abstract

A techno-economical evaluation of the processing result of waste sorting plants should at least provide a realistic assessment of the recovery yields of valuable materials and of the qualities of the obtained products. This practical data is generated by weighing all the output products and sampling these products. Due to the technological complexity of sorting plants, for example, lightweight packaging waste treatments plants and the high expenditures concerning time and costs of sampling with subsequent manual sorting for quality determination, usually only final products undergo such an investigation. Thereby, the transferability of the results depends decisively on the boundary conditions (extent, throughput of the plant, process parameterization). Given that the process is too complex, not all relevant information of the process steps can be determined by sampling. By model calculations and/or adjustment of reasonable assumptions, information concerning weak points in the process can be identified, which can be used for further plant optimization. For the example of the recovery of beverage cartons from co-collected and mechanically recovered mixtures of lightweight packaging waste, a methodical approach for the assessment of processing results will be presented.

Improvement of the recycling of plastics in lightweight packaging treatment plants by a process control concept

“…The aforementioned factors and their influence on the poor sorting results in lightweight packaging treatment plants cannot be specifically quantified, owing to the lack of available data. Significant mass flow fluctuations coupled with suboptimal yields of valuables accounting for the recoverability of beverage cartons – even in plants with multi-level sorting – (Feil et al, 2016, 2017) suggest that, in addition to the aforementioned factors, suboptimal material flows contribute to suboptimal operating results.…”

Can the New Waste Morphology Method Predict Sorting Plants Operational and Financial Challenges? A Case Study in Sharjah

“…The proposed MA methodology was able to predict the rejection of SRM by recycling facilities due to moisture content and contamination levels highlighted by Damgacioglu et al (2019) and Ciprian et al (2015). This research made it possible to estimate, in advance, the losses caused by the false discharge of 3D material in the 2D stream that was indicated by Feil et al (2017) as well. The main advantage of the proposed MA method, however, is the possibility to raise red flags to indicate all the SRM quantitative and qualitative risks and to alert equipment designers about the efficiency risks on the early stages of MSW recovery business plan formation while other MA methods fail to do so.…”

“…The key is choosing the right technology at the right stage in the sorting process to cause a single material stream to behave differently than the others (WRAP, 2006), and in this regard, all existing MAs seem to come short to predict this behaviour by focusing on quantitative evaluation. In one of the case studies, it was found that more than a third of the rigid packaging material feed was falsely discharged into the wrong stream as they easily pass through the screen lining of 65 mm × 65 mm due to the fact that they are not uniform, either in shape or in surface (Feil et al, 2017). The lost quantity can be even higher, knowing that screens opening sizes may sometimes be between 65-80 mm (Jansen et al, 2015).…”

What is the right level of recycling of plastic waste?

“…Although technical solutions are often the core of recycling systems, it must be kept in mind that any technical process involves losses, i.e. the quantity of usable output is typically reduced for the sake of minimising impurities and improving the quality of the resulting product, as discussed by Feil et al (2017). Higher quality output streams allow for higher valued use of the recyclates and, therefore, oftentimes also go along with higher prices for these output products.…”

“…In order to assess the environmental benefits of recycling activities we must evaluate the overall environmental performance of providing a certain quantity of recyclate via the recycling route versus providing the same quantity of a primary product including an environmentally sound management of the plastic waste. Here we must be aware that the environmental performance of recycling decreases when the technical effort during processing increases and the quantity of recyclates decreases owing to losses along the recycling chain (Feil et al, 2017). So even from the environmental point of view, the optimum in plastics recycling is not only defined as maximising plastic waste recycling, but it is likely that there is an optimum recycling quota and when exceeding this environmental burden of collection and processing of plastic waste in order to produce recyclables, exceeds the environmental benefit.…”