Solid waste management in most MENA countries is characterized by lack of planning, improper disposal, inadequate collection services, inappropriate technologies that suit the local conditions and technical requirements, and insufficient funding. Therefore, waste management is mainly limited to collection, transportation, and disposal. As the circular economy has recently been given high priority on the MENA region’s political agenda, all MENA member states are seeking to move away from old-fashioned waste disposal, “waste management”, towards a more intelligent waste treatment, “resource efficiency”. This paper presents a comprehensive overview of national systems for municipal solid waste (MSW) management, and material and energy recovery as an important aspect thereof, in the context of the circular economy in selected countries in the MENA region. Since policy, regulation, and treatment technologies are traditionally connected to MSW management, the focus of this article is twofold. Firstly, it aims to identify the different practices of solid waste management employed in selected MENA region countries and their approaches to embracing the circular economy and, secondly, it examines the extent to which policies and technologies applied play any role in this context. The study revealed that most waste management issues in the countries analyzed appear to be due to political factors and the decentralized nature of waste management with multi-level management and responsibilities. In fact, material and energy recovery in the context of municipal solid waste management does not differ significantly in the countries in the MENA region considered. In most cases, “waste” is still seen as “trouble” rather than a resource. Therefore, a fresh vision on how the solid waste management system can be transformed into a circular economy is required; there is a need for paradigm shift from a linear economy model to a circular-economy model.

Olive mill wastewater sludge (OMWS) is the main by-product of the olive industry. OMWS is usually dumped in landfills without prior treatment and may cause several eco-environmental hazards due to its high toxicity, which is mainly attributed to polyphenols and lipids. OMWS is rich in valuable biocompounds, which makes it highly desirable for valorization by composting. However, there is a need to understand how microbial communities evolve during OMWS composting with respect to physicochemical changes and the dynamics of pollutant degradation. In this study, we addressed the relationship between microbial community, physicochemical variations and pollutants degradation during the co-composting of OMWS and green wastes using metagenomic- and culture-dependent approaches. The results showed that in raw OMWS, Pichia was the most represented genus with almost 53% of the total identified fungal population. Moreover, the bacteria that dominated were Zymobacter palmae (20%) and Pseudomonas sp. (19%). The addition of green waste to OMWS improved the actinobacterial diversity of the mixture and enhanced the degradation of lipids (81.3%) and polyphenols (84.54%). Correlation analysis revealed that Actinobacteria and fungi (Candida sp., Galactomyces sp., and Pichia manshurica) were the microorganisms that had the greatest influence on the composting process. Overall, these findings provide for the first time some novel insights into the microbial dynamics during OMWS composting and may contribute to the development of tailored inoculum for process optimization.