Sampling and analysis of coarsely shredded mixed commercial waste. Part I: procedure, particle size and sorting analysis

K. Khodier,A. Aldrian,P. O’Leary,M. Lehner,A. Curtis,S. A. Viczek,R. Sarc

doi:10.1007/s13762-019-02526-w

Abstract

Performing experiments with mixed commercial waste, sampling is unavoidable for material analysis. Thus, the procedure of sampling needs to be defined in a way that guarantees sufficient accuracy regarding the estimation of the examined analytes. In this work, a sampling procedure for coarsely shredded mixed commercial waste, based on the Austrian Standard ÖNORM S 2127, the horizontal sampling standard DS 3077 and the theory of sampling, was established, described and examined through a replication experiment determining the relative sampling variability. The analytes are described through a matrix of nine (9) material classes and nine (9) particle size classes. It turns out that the typical threshold value of 20% can be reached for some fractions of the particle size–material matrix (for example, wood 20–40 mm and cardboard 60–80 mm) but gets as bad as 231% (wood 200–400 mm) for others. Furthermore, a decrease in the relative sampling variability with the mass share of a fraction is observed. Part of the observed variability is explainable through the fundamental sampling error, while contributions of other types of sampling errors are also evident. The results can be used for estimating confidence intervals for experimental outcomes as well as assessing required sample sizes for reaching a target precision when working with mixed commercial waste.

Highlights

Coarse shredding followed by one or more screening stages is often the first step when processing mixed commercial waste (MCW)
The general estimation error (GEE) consists of this total sampling error (TSE) in addition to the, often well-deter‐ mined, total analytical error (TAE) (Esbensen and Wagner 2014)
The mean throughput—determined at the end of the experi‐ ment—was 25.2 t/h or 71.8 m3/h, resulting in a total mass of 45.0 t, a total bulk volume of 128.1 m3 on the product conveyor belt and a bulk density of 351.4 kg/m3. This means that the bulk density of the shredded material of the replication experiment (REx) is much higher than the expected density of 161.8 kg/ m3

Summary

Introduction

Coarse shredding followed by one or more screening stages is often the first step when processing mixed commercial waste (MCW). Besides size reduction and definition, this combination contributes to the concentration of different materials as well as their contained chemical elements in different fractions. Because of the high inherent inhomogeneity of MCW, performing such experiments demands processing of large amounts of material to homogenize the variability of the input stream regarding composition and particle size between the single runs. These high amounts of material cause the infeasibility of analysing the complete shredding product so that samples need to be taken

Methods

Results

Conclusion