The durability of the foam is therefore a function of the stability of the protective film constituted by surfactant molecules and water and is influenced by the viscosity of the liquid phase, by the mechanical resistance of the film and by other factors [5]. Regarding additives, such compounds can be organic and inorganic (mainly salts to modify the viscosity, the colligative properties, the density of the mixture or to maintain the pH in a specific range), which mainly have different properties such as antifreeze, antimicrobial and stabilizers [6; 7]. The most common anionic surfactant used in commercial conditioning mixtures is the anionic surfactant sodium lauryl ether sulphate (SLES), whose persistence in the environment and biodegradability has been widely discussed as of a single compound [8; 9; 10; 11; 12]. However, in commercial formulations, additional chemicals (stabilizing agents, preservatives, anti-freezing and anti-redeposition agents) are included to increase the quality of the commercial product. The impact of such chemicals is studied by considering the in silico approach and ecotoxicology assays [13]. Therefore, a study of the biodegradation of the whole conditioning mixtures is necessary. The closed bottle method, according to the Organisation for Economic Co-operation and Development (OECD) guideline 301 D [14; 15], is recommended as a simple test for the evaluation of the biodegradation of organic compounds [16]. Such tests involve the determination of the Biochemical Oxygen Demand (BOD) at selected time intervals up to 28 days. When biodegradation occurs, microorganisms consume oxygen until the complete removal of organic substances is achieved. First, surfactant biodegradation is involved, while the ultimate biodegradation (BOD\({}_{\text{u}}\)) occurs when all surfactant molecules are mineralized [17]. In the presence of only biodegradable substrates, Chemical Oxygen Demand (COD) represents a measure of the total oxygen required for the stabilization of the organic compounds and can provide an estimation of the BOD\({}_{\text{u}}\)[18]. For organic compounds, biodegradation is also measured as Total Organic Carbon (TOC) removal, though oxygen consumption can be attributed also to the biological oxidation of non-carbonaceous compounds, such as ammonia nitrification [19]. It is well known that biodegradation rate is dependent on the type of bacterial strain/consortium adopted and different organic removal rates can be obtained: for instance, the degradation of SLES was 11% with _Serratia odorifera_ and a complete biodegradation can be reached if _Serratia_ is coupled with _Acinetobacter_[20]. The use of a specific inoculum has proved to be crucial in defining a reproducible procedure and to compare results obtained by similar tests on different chemical mixtures [21]. The _Bacillus Clausii_ is an inoculum source commercially available and its use does not require particular precautions. It was demonstrated that this kind of probiotic, used to prevent and treat human and animal diseases, is resistant to pharmaceutical compounds especially antibiotics [22]. Basing on such assumptions, it is a good candidate to be used for the study of biodegradability even on complex matrices such as excavation conditioning mixtures. In a previous work [23], the biodegradability of three commercial polymeric foams, adopted during TBM-EPB excavation technology, has been studied by considering the procedure of closed bottle tests up to 28 days and with two different bacterial sources: _Bacillus Clausii_ and soil humus. The methodology is based on the determination of the BOD, COD and TOC of the conditioning mixture over the time.