Decision-based territorial life cycle assessment for the management of cement concrete demolition waste

摘要

Existing territorial life cycle assessments (LCAs) consider all activities in a given geographical area, defined as the foreground system, but cannot lead to operational decisions. In product scale LCA, the foreground system is defined as the part of the system directly controlled by an actor and is thus more adapted to compare possible scenarios within a decision perimeter. The present paper uses that concept applied to a geographical area. The developed method consists of five steps: (a) definition of the foreground material flow analysis (MFA) or LCA system corresponding to the decision perimeter; (b) territorial MFA; (c) geo-location of activities and downscaling of territorial flows to individual activities; (d) calculation of local transport distances; and (e) calculation of LCA impact indicators. The case study concerns the management of primary and secondary resources of basic quality aggregates (BQAs) in the Loire-Atlantique department (France) in 2012. Our results show that the amount of recycled cement concrete is only 7% of total consumed BQAs, although 90% of cement concrete demolition waste (CCDW) is recycled. The environmental impacts are importantly related to off-site activities. Local impacts are mainly driven by the transport of aggregates. For land planning, a concentration of fewer recycling facilities with high authorised production capacities in main cities, close to where CCDW is mainly produced, would divide transport needs in half and thus considerably reduce environmental impacts.