Waste Management & Research 30(7) 645–655 © The Author(s) 2012 Reprints and permission: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/0734242X12442740 wmr.sagepub.com Introduction Metals in municipal solid waste Municipal solid waste (MSW) and products from mechanical treatment (MT) or mechanical biological treatment (MBT) of MSW are commonly known to be very heterogeneous materials and difficult to analyse. Heterogeneity results from the enormous variability of disposed products comprised in MSW. In particular, heavy metal contents vary extremely since individual products (often such, which irregularly occur in MSW) are highly concen- trated in these elements. Cables, brass made shower hoses, stain- less kitchenware, electric or electronic devices, etc. which scarcely occur in MSW contain high amounts of heavy metals in metallic species, either pure (e.g. Cu as electric conductor material) or as major components in alloys (brass, stainless steel, etc.). Also many other consumer goods which are regularly collected via MSW con- tain tiny pieces of metallic components. Examples are: clothes or bags with zippers (brass or zinc casting alloys), toys with metallic drive mechanisms (brass made cogwheels), disposable razors (stainless razor blade), curtains with lead-weighted hems etc. (common applications of the chemical elements in consumer goods are listed in Vassilev and Braekman-Danheux (1999)). Products of linear shape (cables, shower hoses, etc.) or textiles and plastics containing small metallic components may be transferred into high calorific value fractions, since they can hardly be removed by magnetic or eddy current separation techniques. (Note, that common practice of M(B)T is addressed here, which comprises rough shredding, screening or ballistic separation, magnetic sepa- ration and in some cases eddy current separation). Specification of heterogeneity, terminology In terms of sampling theory, heterogeneity arising from different analyte contents among ‘constituents’ (individual pieces) is defined as constitutional heterogeneity CH L (Gy, 1992). CH L Metals in RDF and other high calorific value fractions from mechanical treatment of MSW: analysis and sampling errors Stefan Skutan and Paul H Brunner Abstract RDF and other high calorific value fractions derived from MSW by mechanical treatment processes contain goods such as cans, cables, zippers or batteries which are highly concentrated in metals. The objective of this study was to investigate the importance of these metal carriers (i) for total metal loads and (ii) for sampling errors. Six different products derived from MSW were analysed for carrier bound and total loads of Al, Cd, Cr, Cu, Fe, Ni, Pb and Zn. Sophisticated sample preparation procedures were applied in order to quantify the separate analyte loads from metallic carriers. Typical values for total metal contents and shares of carrier bound loads were found as follows: Al, 20 g kg −1 (30%); Cr, 0.4 g kg −1 (50%); Cu, 5 g kg −1 (80%); Fe, 40 g kg −1 (80%); Ni, 0.15 g kg −1 (70%); Pb, 0.4 g kg −1 (40%); and Zn, 2 g kg −1 (30%). NiCd-batteries were found in three materials representing 30–70 % of total Cd contents (total 6–20 mg kg −1 ). Sampling errors related to the distribution of analyte carriers were in most cases found in the range of 50–150 % relative standard deviation in spite of the large sample masses of 200–800 kg. The results demonstrate: (1) metal carriers are responsible for significant analyte loads; if they are not adequately considered, total metal contents may be severely underestimated; (2) sampling errors are dominated by the distribution of carriers; (3) correct analysis of total metal contents including loads from metallic components requires expensive sample preparation. Keywords High calorific value fraction, refuse derived fuel, heavy metals, sampling errors, sample preparation, mechanical treatment, waste characterization, analysis Institute for Water Quality, Resource and Waste Management, Vienna University of Technology, Vienna, Austria Corresponding author: Stefan Skutan, Fritz-Weigl-Gasse 1a, 3423 St. Andrae-Woerdern, Austria Email: stefanskutan@aon.at 442740WMR 30 7 10.1177/0734242X12442740Skutan and BrunnerWaste Management & Research 2012 Original Article