Construction and demolition waste in Macedonia, a study financed by the know-how exchange program SAMCODE promoted by the Central European Initiative

Construction and Demolition (C&D) waste is the solid debris resulting from construction and demolition activities. Recycling of this solid waste may result in substantial economic and environmental benefits. Unfortunately, is some Balkan countries such as Macedonia C&D recycling awareness is not developed yet. In this country, C&D are often dumped without control. According to the Macedonian landfill operator "Drisla" the estimated amounts of C&D waste generated per year in the Skopje surroundings approach 150.000 tons, but nothing is known on their composition. On this basis, a know-how exchange programme (KEP) called SAMCODE was financed by the Central European Initiative (CEI) and specifically dedicated to the characterization of C&D waste in Macedonia. GAYA operators sampled C&D landfills in the surroundings of Skopje, verified the absence of radioactivity, and then crushed the C&D down to the grain size of two millimetres. Crushed C&D chips were sent to the Department of Physics and Earth Sciences of the University of Ferrara, where the materials were powdered and analysed by X-ray fluorescence (XRF). Moreover, to characterize elemental mobility leaching tests on the C&D powders were carried out according to the following protocol: 1g of C&D powder has been soaked with 10 ml of deionized water, for 24 h. Subsequently the solutions have been centrifuged, filtered (at 45 mm) and analyzed by inductively coupled plasma mass spectrometry (ICP-MS). XRF analyses showed that – although variable - silica, calcium and aluminium are always the dominant components (SiO₂ between 32 and 60 wt%, CaO between 7 and 30 wt%, Al₂O₃ between 7 and 16%) suggesting possible recycling in the ceramic/cement industrial processes. However, the real re-use of these materials in industrial processes is hampered by the lack of homogeneity, a feature required by the industries. The analysis of trace elements emphasized another critical aspect: Macedonian C&Ds often contain anomalously high concentrations of elements potentially hazardous, especially chromium (Cr), nickel (Ni), lead (Pb) and zinc (Zn). Note that the high concentrations of Cr, Ni, Zn and Pb do not necessarily recall the presence of contaminants, as these elements can be present in natural raw materials used in the country. Noteworthy, in Macedonia there are rocks included in the ophiolite sequences such as peridotites, serpentinites, pyroxenites and chromitites that can contain thousand(s) ppm of chromium and nickel, and also mining areas where there are sulphides of lead (galena) and zinc (sphalerite). If similar rocks are used as raw materials in the building activity, it is not strange to have C&D anomalously enriched in Cr, Ni, Pb, Zn. This hypothesis is confirmed by soil studies retrieved in the literature that highlighted that Macedonian soils can contain anomalous content of these elements. ICP-MS analyses of leachates show negligible concentrations of Ni, Pb and Zn, but significant concentrations of Cr. The results indicate that to foresee effective recycling Macedonian C&D have to be preliminarily screened to eliminate Cr-bearing components, crushed and sorted to obtain a better homogenization.