Pollution by plastics is an environmental problem with profound implications for all forms of life on earth. Each year, humans generate millions of tons of plastic waste, most of which ends up in landfills and marine ecosystems. Single-use plastics, such as plastic bags, among others, are mostly made of low-density polyethylene (LDPE), which are produced in large quantities and are discarded almost immediately after their acquisition. Consequently, manufacturers added pro-oxidant additives in the production process, plastics that are now marketed as Oxo-Degradable plastics (LDPE Oxo) sold under the premise of being a biodegradable product. However, recent research has indicated that pro-oxidant additives only catalyse plastic fragmentation under specific reaction conditions. The environmental problems are not only caused by the mass production of this material, but also by the irresponsible management of plastic waste, especially LDPE-oxo. Waste management includes the treatment and proper disposal of waste. For this, the biological treatment of LDPE Oxo is used, which consists of using the ability of microorganisms to produce oxidative enzymes that cleave the complex structure of the plastic. Pleurotus ostreatus is a white rot fungus (WRF) that stands out from other WRFs because it can produce a vast enzymatic complex that oxidizes complex compounds that have C-C bonds and aromatic rings in their structure, among others. Although P. ostreatus is a promising alternative for the degradation of LDPE Oxo, it cannot assimilate it by itself because LDPE Oxo is hydrophobic, a characteristic that makes it difficult for any microorganism to colonize its surface. Therefore, in this work, a pretreatment to the LDPE Oxo with O2 plasma was carried out because the plasma is able to modify the surface of the LDPE Oxo turning it hydrophilic and with it facilitates the adhesion and colonization of P. ostreatus. On the other hand, solid fermentations favour the growth and enzymatic activity of P. ostreatus. Due to this, microcosm systems were used, which also allow controlling factors that influence the effectiveness of the fermentation. In a recent investigation associated with the biodegradation of LDPE Oxo with P. ostreatus, the possibility of using a vertical microcosm system (VMS) as a technology to treat LDPE Oxo was reported. However, the treatment presented humidity problems that made difficult the biotransformation of the LDPE Oxo, therefore, in this work a horizontal microcosm system (HMS) was implemented in order to control this variable and improve the biotransformation of the LDPE Oxo. In addition to modifying the geometry of the system, lignocellulosic biomass (LCB) composed of pine bark, hydrolyzed brewer's yeast, and paper as a matrix to support the growth of P. ostreatus was added to stimulate fungal cometbolism. In order to determine which of the systems (HMS and VMS) favoured the biodegradation of both the LDPE Oxo after being subjected to the O2 plasma and the BLC after being subjected to the biological treatment for 135 days, hydrophobicity was evaluated by the technique of static contact angle (SCA) and roughness by atomic force microscopy (AFM) of the LDPE Oxo. At the end of the treatment (day 135) a decrease in hydrophobicity of 63.63% was observed for the LDPE Oxo sheets contained in the HMS. In contrast, the LDPE Oxo contained in the VMS showed a percentage decrease of 74%. The results in these two variables of responses associated to the LDPE Oxo indicate that the biodegradation of the LDPE Oxo in both systems ( HMS and VMS) is similar. On the other hand, the enzymatic activity of Lacase (Lac) (14599 ± 3520 U Kg-1), Manganese peroxidase (MnP) (1962.4 ± 220.3 U Kg-1) and lignin peroxidase (LiP) (10008 ± 2406 U Kg-1), was significantly higher in HMS than in VMS, Lac (10314 ± 1190 U Kg-1), LiP (2868 ± 941 U Kg-1) and MnP (576 ± 30 U Kg-1). These results suggest that the HMS enhances the activity of ligninolytic enzymes associated with the biodegradation of recalcitrant compounds such as LDPE Oxo and lignin. In relation to the biodegradation of LCB, the degree of polymerization and condensation of the lignocellulosic mixture was determined semi-quantitatively by means of the carbon fractionation method and the analysis of the E4/E6 ratio. The results indicate that direct humification processes are carried out in both systems and that indirect humification processes are beginning to occur in HMS, but this doesn't imply complete maturation and condensation of LCB. Finally, from the residual LCB (LCB/R) a class III biochar was responsibly manufactured. This work was carried out within the framework of solid waste use, management of recalcitrant solid waste, through co-treatment of waste in microcosm systems, as well as, the responsible generation of a product with commercial value.