VALORIZATION OF CONSTRUCTION AND DEMOLITION WASTE, A ROUTE TO CIRCULAR ECONOMY: THE VALDEM PROJECT | VALORISATION DES DÉCHETS DE CONSTRUCTION ET DE DÉMOLITION, UNE VOIE VERS L'ÉCONOMIE CIRCULAIRE : LE PROJET VALDEM

English. INTRODUCTION From resource prospective, building and construction sector is responsible for more than third of global resource consumption, and its generation of solid waste is estimated to be 40% of the total waste volume. At European level, construction and demolition waste is the largest waste stream representing one third of waste produced in EU. Therefore, the resource efficiency and management is crucial in building construction. A very significant part of the construction and demolition waste (CDW) is not recycled today. In addition, a very limited part is used as a recycled content in the construction and building products and materials. This lack is mainly due to heterogeneity and dispersion of waste flows, decreasing efficiency and economic viability of recycling. To address this issue, VALDEM project (funded by Interreg FWVL European Fund) aims to overcome barriers to increase up-cycling applications. The project focuses its activities in North of France, Flanders and Walloon regions (Belgium), and stands out from usual approaches by its cross-border view of circular economy. VALDEM aims, on the one hand, to optimize buildings end of life management by developing new deconstruction, sorting and recycling processes to produce uniform and accessible material flows. On the other hand, the project aims at increasing recycling and generating high quality secondary materials (concrete and other flows) to be used in future buildings within an up-cycling prospective. Finally, it aims at validating the solutions from technical, scientific, economic and environmental point of view. One of the VALDEM partners, Néo-Eco, was implied in a project of Leroy-Merlin Company. The concrete aggregates from the demolition of the former Leroy Merlin store in Douai were reused in the construction of the new store in Tourcoing/Neuville-en-Ferrain, for the new concrete slab. This recovery made it possible to give a second life to waste, instead of paying for its disposal. LCA team of Valdem took the opportunity to evaluate the environmental benefits of this approach. LCA OF THE VALORIZATION OF DEMOLITION WASTE FROM LEROY MERLIN STORE Leroy Merlin has adopted a circular economy approach by recycling a part of the demolition waste of the Douai store in the form of recycled aggregates (RA) integrated into the concrete slab of their new Tourcoing store (4-20 mm fraction). The remaining 4-20 mm aggregates are recovered and valorised in concrete for other sites by Eqiom, and in resin slabs for the fines (0-4 mm) by Recynov. The LCA compares the production and transport of natural and recycled aggregates, and their respective use in the production of concrete. If we consider the production of 1 m³ of concrete, with only natural aggregates (NA) or substituting 20% for recycled aggregates, the difference is not significant, however, since most of the impacts come from cement. The aggregates themselves represent only a small contribution to the overall impact, regardless of the impact category considered. Cement alone accounts for at least 60% of the effect, and up to 92.5% for Climate Change. On the other hand, if we focus on the aggregates, this recovery of the "waste" from the Douai demolition site as a substitute for natural aggregates allows an environmental gain compared to the use of natural aggregates alone. This benefit is all the more important as the location of their use is close to the demolition site, and is less than the supply distance for natural aggregates. For the Climate Change category (GWP100a), the gains range from 1 kg CO2 eq to 5.7 kg CO2 eq depending of the distance between the demolition and the valorization sites (from 4 km to 50 km). The use of the aggregates from the Douai demolition site as a substitute for natural aggregates can save 10400 kg eq CO2 if we consider the exploitation of all the aggregates (4-20 mm and 0-4 mm). The 4-20 mm fraction (1700 tonnes) can produce 8500 m³ of concrete, if we consider the integration of 20% RA (0.2 t/m³ in the present formulation). In conclusion, the recovery of demolition waste from the Leroy Merlin site in Douai provides a significant environmental gain compared to the use of natural aggregates. ACKNOWLEDGEMENTS The authors would like to thank the Valdem project (Convention n° 1.1.57 of Interreg France – Wallonie - Vlaanderen 2014-2020) partly financed by the European Regional Development Funds, and the Walloon Region. Our gratefulness also goes to Mr Maxime Lahaye (Leroy Merlin), Mr Guillaume Crémoux (Eqiom), and Mrs Maurane Vermander (Neo-Eco) for their help and collaboration in the data collection.

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