From waste to land rehabilitation: exploitation of mineral waste fine fraction to produce cultivable substrates

Wastes coming from extractive industry (EW) and construction and demolition activities (C&DW), including rock and soil from excavation works (RSE), represent the 2nd and the 1st source of waste production at EU level (25% and 36% respectively, Eurostat 2019). They can cause serious environmental and economic problems related to their management and disposal, in particular for the finest fraction. They are characterized by low physical and chemical fertility, which require the mixing with organic materials to improve their general properties. The aim of the present study is to test the agronomic characteristics of the produced mixes in order to evaluate their potentiality to be used for land rehabilitation, and to evaluate the environmental criticalities when the new substrate is used for land rehabilitation. The investigated mineral wastes are: residual sludge from ornamental stones working activity, EW fine fraction, and the fine fraction arising from C&DW and RSE recycling activities. Waste materials were collected and mixed with compost, shredded green compounds, wastewater sludge and soil material. The original materials and the mixtures were analyzed for metals and total hydrocarbons (where present) and for their phytotoxicity (seed germination and plants growth). The results show that the mixing with organic compounds can improve the overall quality and fertility of the mineral waste fine fraction and that the mixtures are generally not phytotoxic. This indicates that the mineral waste fine fraction could be employed, when properly managed and treated, for land rehabilitation after improvement of its fertility and environmental quality.