###### Abstract
Sediment (S), dredged from water bodies, has been successfully co-composted with GW such as municipal [14,15] ([PERSON] et al., 2016; [PERSON] and [PERSON] 2022), agricultural [16,17] ([PERSON] et al., 2022 and 2023) and marine [18] ([PERSON] et al., 2020) plant residues. In particular, the S addition to GW can improve the water-holding capacity, electrical conductivity and nutrient availability of the final product [15] ([PERSON] and [PERSON] 2022). In addition, the S-GW co-composting is effective in the reduction in organic pollutants, of which S are rich [14,17] ([PERSON] et al., 2016; [PERSON] et al., 2023). However, previous studies demonstrate some limitations in S-GW co-composting, that can reduce the field of application of the final products. The restricted thermophilic phase has been observed in 0.200 m\({}^{3}\) piles with 1S:1 GW and 3S:1 GW (\(v\)-\(v\)) ratios, affecting the sterilization of the co-composts [14] ([PERSON] et al., 2016). In addition, the high pH of the co-composts limits their application as growing media, especially in agriculture [14] ([PERSON] et al., 2016). [PERSON] et al. [18] (2020) noticed an organic carbon content in S-GW-based co-composts that did not comply with the local normative limits for agricultural applications. Changes in S and GW ratios can affect the co-composting process as well as the maturity of co-composts [19] ([PERSON] et al., 2023). In particular, GW can enhance the microbial diversity during the co-composting thanks to its role as an energy source [20] ([PERSON] et al., 2017). [PERSON] et al. [17] (2023) demonstrate that the addition of a high proportion of GW in the co-compost pile improves the S-GW co-composting and the quality of the final products, while the co-compost with a high proportion of S (3S:1 GW) shows some limitation for its agricultural applicability, according to national law [17] ([PERSON] et al., 2023). S-GW co-composting allows the production of sustainable growing media that can replace peat for agricultural production [17; 21] ([PERSON] et al., 2023; [PERSON] et al., 2024). In fact, peat is the main non-renewable growing media used for plant cultivation and the research of alternative growing media is of pressing interest. The use of peat implies high costs for its extraction and transport as well as the negative environmental impact for peatland exploitation [22; 23] ([PERSON] et al., 2018; [PERSON] et al., 2023). The application of S-GW co-compost as growing media for peat replacement has been previously investigated for ornamental plants, with positive effects on plant performance [20; 21; 24] ([PERSON] et al., 2017; [PERSON] et al., 2022; [PERSON] et al., 2024). Although the species-specific effects of S-GW co-compost on the plant growth has been observed, the use of S-GW co-compost as growing media leads to a reduction in GHG emissions around 11.66-23.1% [21] ([PERSON] et al., 2024). In addition, the use of co-compost, derived from the S-GW co-composting, can improve the plant tolerance to abiotic stress and the nutritional status, as seen in ornamental plants growing on co-compost, composed of S and _Posidonia oceanica_ residues [24] ([PERSON] et al., 2022)  
The biological assessment of the S-GW co-compost stability can allow one to better assess their recycling and their application, especially for co-compost with high percentage of S. The co-compost stability is related to microbial activities that reduce during the co-composting, along with the organic matter degradation degree. However, the microbial nutrient limitation can occur after the application of the co-compost as a growing media. The instability of the growing media leads to a further decomposition of organic material and the uptake of nutrients by a microorganism causes a plant nutrient deficiency [25] ([PERSON] et al., 2016). The eco-enzyme stoichiometry theory (EST) can allow one to better assess the biological stability of the co-composts as it links the enzyme activities and microbial nutrient availability.