Restoration of Mediterranean quarry soils with compost from marine organic waste: first insights from the PRIN 2022 PNRR EMBRACE project

Organic amendments, rich in stable organic matter, can foster the recovery of degraded soils by enhancing their chemical and physical properties, sustaining microbial communities, and promoting natural revegetation. This is especially relevant in Mediterranean climates, where soil organic matter depletion is a widespread and serious issue. In a circular economy framework, the EMBRACE project (PRIN 2022 PNRR) aims to valorise marine waste in terms of energy and matter recovery, using the resulting by-products to restore degraded soils in Mediterranean ecosystems. To this end, two composts were produced from the sequential anaerobic and aerobic digestion of Posidonia oceanica litter and fish market waste, with and without the addition of natural zeolites from quarry waste, and tested for their ability to promote the recovery of quarry soils. Seasonally, natural revegetation is assessed through phytosociological relevés, evaluating species richness, evenness and composition. In parallel, the amended soils are characterized from a chemical, physical, biological and toxicological perspective, the latter carried out using Lepidium sativum L. and Sorghum saccharatum L. seed germination and shoot elongation as endpoints. Results obtained so far showed that the addition of organic matter significantly enhances revegetation in the amended soils as compared to the untreated controls, with structural and functional differences in plant community diversity induced by different treatments. Furthermore, no phytotoxic responses were observed in both endpoints, indicating instead mild phytostimulatory effects. The soil microbial community function also changes in reaction to various treatments, with the soils enriched with compost overall exhibiting improvement. These early findings highlight the potential for scaling up ecological restoration efforts with reclaimed materials, while simultaneously addressing the socio-economic issue of marine litter accumulation on tourist coastal areas.