## 1 Introduction  
The abundance of wastes rich in biodegradable organic matter presents significant opportunities for resource recovery. A promising approach to valorize such wastes is through the biorefinery concept, where biomass is converted into a wide array of valuable products, including fuels, energy and chemicals. Among these processes, anaerobic digestion (AD) breaks down organic materials and produces biogas and nutrient-rich digestate useful in agriculture [1]. While mesophilic single-stage AD is the most widely implemented process [2], alternative configurations, such as Temperature-Phased Anaerobic Digestion (TPAD), have emerged to enhance the reduction of volatile solids (VS) and increase gas production compared to mesophilic single-stage anaerobic digestion [3]. TPAD involves a two-stage process: an initial thermophilic acidogenic stage (55 \({}^{\circ}\)C) where hydrogen is generated, followed by a mesophilic methanogenic stage (35 \({}^{\circ}\)C) where methane is generated. This configuration facilitates the recovery of hydrogen and volatile fatty acids (VFAs) during the thermophilic acidogenic stage. Usually, the efficiency of conventional AD is often constrained by the nature of the substrate, particularly in the case of complex and recalcitrant wastes, such as sewage sludge [4]. To address these inconveniences, co-digestion strategies can be employed to enhance the overall digestion process. An effective approach is the co-digestion of sludge with wine vinasse. Similarly, the co-digestion of two-phase olive mill waste with cattle manure has shown promising results. By combining different wastes, the C/N ratio (20 to 30) is optimized for the development of anaerobic processes [5; 6]. In addition, pre-treatment methods can be used to improve substrate solubilization and also to increase the content of biodegradable organic matter. Various physical, chemical and biological pre-treatment methods have been explored in the literature, including those using acid, alkali, Fenton reagents, calcium peroxide, H\({}_{2}\)O\({}_{2}\) and ozone [7]. Acidic conditions promote the dissolution of proteins and polysaccharides into extracellular polymers and microbial cells, with effectiveness increasing as the pH decreases. In contrast, alkaline conditions facilitate optimal sludge solubilization, typically occurring in the pH range of 11 to 12.5, resulting in significant increases in soluble protein, polysaccharide and soluble chemical oxygen demand (SCOD). Pre-treatments based on H\({}_{2}\)O\({}_{2}\)-driven advanced oxidation processes have been shown to significantly improve methane yield and VS removal in AD. Notably, the Fenton agent, consisting of H\({}_{2}\)O\({}_{2}\) and an Fe\({}^{2+}\) catalyst, generates abundant hydroxyl radicals (-OH) under acidic conditions, resulting in a higher redox potential compared to H\({}_{2}\)O\({}_{2}\) or ozone treatments alone [7]. During recent years, ozone pre-treatment has gained significant attention due to its high oxidative potential, which effectively degrades organic matter [8], also making it a valuable disinfect in various fields [9]. Ozone enhances the hydrolysis of solids due to the increased surface area relative to particle volume, reducing the molecular weight of organic compounds [10]. This hydrolytic process improves the efficiency of the subsequent biogas production. For example, a 1.31-fold increase in methane production from municipal waste sludge and a 2.25-fold increase from pharmaceutical waste sludge with ozone pre-treatment were observed in Biochemical Methane Potential (BMP) tests [11]. Similarly, an increase of up to 52% in methane production from anaerobically digested sludge has been observed in BMP tests [12]. In parallel, the use of additives, including micro- and macro-nutrients, nanomaterials and biological additives, has shown promising results in enhancing microbial activity and electron transfer in AD processes, leading to improved methane production [13; 14].