Potential evaluation of the use of construction and demolition waste (CDW) in the recovery of degraded soils by mining in Brazil

Abstract

The management of construction and demolition waste (CDW) and its correct final destination has become a global problem due to the growth of urbanization. At the same time, there is a need to recover soils degraded by mining, a source of raw material for the production of inputs and materials necessary for urbanization itself. The objective of this work was to evaluate the process of recovery of degraded areas by open-pit mining using CDW and composted eucalyptus bark (CEB) as a component for the recovery of these degraded soils. Three 20 kg samples of recycled CDW were collected by NBR 10.007 at a recycling plant in Criciúma, State of Santa Catarina, Brazil, from October 2018 to October 2019, in the particle size fraction of up to 2 mm. The CDW samples were fragmented in an orbital mill, being further characterized by X-ray fluorescence (XRF) and X-ray diffraction (XRD). Calcite and quartz were found in the CDW samples, in addition to Fe, Mg, Mn, Cu, Zn, Ni, K and P. Chromium (Cr) and barium (Ba) were found above the limits of Resolution 420/2009 of the National Council for the Environment (Brazil), while according to Orden AAA / 661/2013 (Spain), all elements found were above the permitted limits. The composted eucalyptus bark was obtained from a production company, using residues from the cellulose industry. The potential of CDW as a soil recovery element was determined from the generation of a substrate composed of natural soil, CDW, and CEB, in the proportion of 10%, 20%, and 40% by mass of CDW, associated with 6 t ha−1 and 8 t ha−1 of CEB. The residues were homogenized, placed in growing pots and then Avena strigosa was cultivated in a greenhouse as a bioindicator. The atomic absorption spectrometry technique was used to determine the content of toxic metals in the leaf and root systems and the leachate generated by irrigation. Only chromium was detected in the root system, with all elements analyzed below the limits of detection in the leaf and leachate system, resulting in non-translocation conditions for these metals. There was an increase in soil fertility, biomass production, and growth of Avena strigosa plants with increased CDW dosage. A significant increase in potassium in the soil produced was observed: 322 kg ha−1 of potassium, which represents 388 kg ha−1 of K2O, in addition to an increase in soil pH, with an input of 1.06 t ha−1 of calcium, which is equivalent to 1.483 t ha−1 of CaO. Phosphorus contents were below recommended for soil recovery. The use of CDW in consortium with CEB as an element in the recovery of degraded soils proved to be viable and safe in environmental terms.