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

From resource prospective, building and construction sector is responsible for more than third of global resource consumption, including 12% of the fresh water use 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 all 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 recy-cled today. Also 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 bar-riers 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 one hand, to optimize buildings end of life management by devel-oping new deconstruction, sorting and recycling processes to produce uniform and ac-cessible 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 fu-ture buildings within an up cycling prospective. And finally it aims at validating the solu-tions from technical, scientific, economic and environmental point of view.
The Environmental assessment, based on LCA, consists of identifying hotspots and key aspects to prioritize the efforts of different economic actors. As a first step, an LCA meta-analysis is conducted to provide an environmental picture for different potential activities within the scope of the project. As a next step, a comparative LCA is conducted to assess the environmental benefits and impacts of different solutions proposed in the framework of the project in a decision making context, and to limit the impact transfer and to generate the maximum value for all the stakeholders. Finally, results will be trans-ferred to main actors (recycling operators, buildings contractors, product manufactur-ers …) in the three regions in order to consolidate future key aspects to eco-design a building in light of circular economy. In correlation with this projects, we have used the results of another research project, CONREPAD (BEWARE fellowships), in which some VALDEM operators were involved (ULiège – GeMME, Prof. Luc Courard). The theme is the recycling of waste concrete blocks manufactured by the PREFER company (Belgium), and in particular the substitution of natural aggregates (NA) by crushed waste blocks as recycled concrete aggregates (RCA). The CONREPAD study determined that the integration of 30% of RCA did not alter the mechanical properties of the blocks and was therefore conceivable (B_RCA30 blocks). A comparative LCA is to made to evaluate the impact of the recycling process of the block waste, and to assess the influence of their integration in the making of the blocks in substitution of the NA, in comparison with to the "business as usual" process (NA only). The results do not show significant gain in any impact category because of the very low available amount of waste (1%), as the internal production of RCA added in B_RCA30 blocks can only substitute 3% of the global production of Prefer. An alternative scenario, based on the import of external RCA from a nearby CDW sorting site, shows however a potential gain in all categories, especially in the Land use category (up to 11.5%) if the total production of blocks consists of B_RCA30.
In conclusion, globally and in a circular economy perspective, the substitution of NA with RCA from internal production waste blocks and external source of CDW, is an interesting development route to improve the environmental impact of the concrete blocks made by Prefer.