###### Abstract  
Co-composing efficiently reclaims dredged sediments (S) and green waste (GW), creating stable products for agricultural applications. However, the use of S-GW co-composts can be limited by legislative thresholds, especially for co-composts with a high S percentage. The evaluation of S-GW co-compost stability by biological assessment can allow for a better understanding of S and GW recycling, as well as the S-GW co-compost application. For this purpose, the microbial biomass, composition, respiration, and eco-enzyme stoichiometry (EST) were assessed, coupled with chemical analysis, in the co-composing of S and GW in different ratios. The _Phottitia x fraseri_ and _Viburum  
indicators ([PERSON] et al., 2018) [1]. The main microorganism groups involved in composting are mesophilic and thermophilic ones, including bacteria and fungi. The activities of microorganisms during composting affect the temperature, as a great amount of energy is produced but only a fraction (about 45%) is used for ATP production and the rest is lost as heat [4] ([PERSON] et al., 2021). At the beginning of composting, mesophilic bacteria colonize and degrade labile organic matter, increasing the temperature inside the pile. At temperatures above 45 \({}^{\circ}\)C (thermophilic phase), thermophilic fungi and bacteria enhance their activities and the further increase in the temperature allows the compost sterilization. In the thermophilic phase, the highest microbial diversity and variability in microbial community can occur, as seen in olive mill waste composting ([PERSON] et al., 2011) [5]. Afterwards, the temperature drops allow mesophilic microorganisms to colonize the pile and the co-compost stability is reached when the microbial activities reduce [6,7] ([PERSON] et al., 2020; [PERSON] et al., 2022). In addition, pH values around neutrality are optimal for microbial development during the co-composting and fungi in particular are more tolerant to pH variations ([PERSON] et al., 2018) [1]. The properties of raw materials can also affect the microbial activities during co-composting, including the carbon-to-nitrogen ratio (C/N). Optimal values of 25 for C/N are commonly recommended in raw materials. In material with higher initial C/N ratio, such as lignocellulosic ones, the organic matter degradation is limited due to carbon chain complexity ([PERSON] et al., 2018) [1]. The selection of raw materials and operation conditions can influence the bacteria and fungi abundance during the co-composting, affecting the co-compost quality. [PERSON] et al. (2022) [8] claimed that the combination of different waste materials (e.g., vineyard pruning, tomato waste) can favor the development of microorganisms with suppressive activities against pathogens, improving the co-compost quality. The efficiency of aerobic composting in organic waste recovery and recycling has been widely demonstrated, producing stable fertilizers [9] ([PERSON] et al., 2023). However, the performance of composting depends on the initial material properties. In green waste (GW), the lignocellulosic biomass affects the composting process, due to the recalcitrance of lignin that wraps cellulose and hemicellulose in the plant structure. In the early stage, the cellulose is the main carbon source for bacteria, but their ability to degrade lignin is limited. In fact, the lignin degradation is mainly driven by fungi. The low biodegradability of lignocellulosic biomass restrains the GW recovery through composting. To overcome this problem, chemical and biological pre-treatments are applied to enhance the composting feasibility [6,10,11], but they are often expensive, such as nitrogen-rich additives or woody fraction removal [12,13] ([PERSON] et al., 2016; [PERSON] et al., 2018; [PERSON] et al., 2020; [PERSON] et al., 2023; [PERSON] et al., 2023). The co-composing of GW with other matrices can enhance GW recycling and management, simultaneously allowing different wastes to be recovered.