Synergy between dark fermentation effluent valorization and circular leaching strategies: Experimental optimization and sustainability assessment

This study explores an innovative approach for the management of acidic dark fermentation effluents, via their use in leaching processes, to dissolve the components of construction and demolition waste. Firstly, the composition of the effluent (focusing on acetic, propionic, butyric, and lactic acids), as well as the main operating conditions (contact time, acid concentration, and solid to liquid ratio), were optimized. Successively, the use of a real effluent from cheese-whey was tested at laboratory scale, and the economic feasibility of the process was evaluated. Finally, the sustainability of the process was studied adopting a life cycle perspective. Results showed that the optimized leaching process (0.25 M), when applied using the real fermentation effluent, resulted in the dissolution of approximately 93% of the calcium content in the treated waste. Moreover, under specific market and operational assumptions, the proposed approach would yield a profit of more than 2 $ per kg of treated construction and demolition waste, due to the revenue generated by energy and materials recovery via biological processes. Also, the proposed technology would be environmentally advantageous, significantly mainly contributing to the mitigation of terrestrial ecotoxicity and global warming potential, representing a promising, though scale-dependent, solution for circular waste management.