Life cycle assessment and residue leaching: The importance of parameter, scenario and leaching data selection

Life cycle assessment of construction and demolition waste management

“…Based on an annual precipitation rate of approximately 780 mm year À1 in Denmark (Cappelen, 2012); rainwater infiltration under the asphalt pavement of 10 per cent and density and thickness of the C&DW in the road sub-base layer of 1850 kg m À3 and 30 cm respectively, the resulting L/S ratio after 100 years was 14.1 L kg À1 TS. This data is based on typical road construction practices and previous studies (Allegrini et al, 2015;Wahlström et al, 2014).…”

“…As, Sb and V), their redox-dependent properties are not as straightforward and unambiguous as for Cr, resulting in limitations of the LCA methodology in terms of available characterisation factors (CF) for the different oxidation states. For all other elements, the approach proposed by Allegrini et al (2015) for utilisation of MSWI BA in road construction was adopted (with respect to overall mineralogy, leaching behaviour and applications, C&DW and MSWI BA can be considered comparable). Allegrini et al (2015) modelled the reactive transport of contaminants through a 0.95-m layer of soil (underneath a road structure) based on multi-surface models implemented in ORCHESTRA (Meeussen, 2003).…”

“…The leaching emissions may be accounted for in different ways: the leachate may be assumed to be released directly into a soil compartment (Chowdhury et al, 2010) or directly into a water compartment (Olsson et al, 2006;Toller et al, 2009). Due to the way in which leaching has been modelled thus far in LCA, the potential immobilisation processes in the subsoil immediately below the mineral residue layer -for example, a road construction scenario -have not been taken into account, apart from two recent studies for MSWI BA and different granular secondary materials (Allegrini et al, 2015;Schwab et al, 2014). In the context of C&DW, this might be particularly critical for Cr, which has been identified as one of the elements of main concern in leachates from C&DW in relation to utilisation in construction works (Butera et al, , 2015avan der Sloot, 2000;Wahlström et al, 2000), and which has been shown to be retained by subsoils (Butera et al, 2015b).…”

Soil retention of hexavalent chromium released from construction and demolition waste in a road-base-application scenario

“…The cover controls how much water infiltrates into the C&DW, generating the leachate. We assumed that 10% of the rainfall (10% of 2 mm· day −1 in Denmark) infiltrates through the road, based on previous studies [32,33] The Cr(VI) concentration in the leachate decreases with time from an initial high value (40-450 g· L −1 in the best-and worst-case scenario respectively, corresponding to approximately 2-26 eq· L −1 ) to final levels of approximately 10 g· L −1 , or 0.7 eq ·L −1 in both cases.…”

“…The Cr(VI) contaminant profile showing Cr(VI) greater than 0.05 eq· L −1 stretched as deep as 190 cm right after leaching started. However, 30% infiltration is an extreme worst-case scenario [33], likely encountered only for unmaintained or dismissed roads.…”