Biogas production by an anaerobic digestion process from orange peel waste and its improvement by limonene leaching: Investigation of H2O2 pre-treatment effect

Orange peel waste is considered as an important feedstock for anaerobic digestion to generate bio-energy such as bio-hydrogen and bio-methane; however, its use as an energy source is still not important worldwide. Therefore, in the current study, the biochemical methane potential test was carried out to estimate the biogas production from orange peel waste by using an anaerobic digestion process in the thermophilic phase (T = 55°C). In order to investigate the antimicrobial and the inhibiting effect of limonene contained in orange peels on biogas production two experimental setups were operated simultaneously using de-oiled and crude orange peel wastes, respectively. For further enhancement of the biogas production, a pre-treatment was applied using hydrogen peroxide (H2O2) at different concentrations up to the optimum value to increase soluble chemical oxygen demand (COD). The obtained results showed an important increase in biogas production: From 170 mL.gTVS−1 for the untreated sample to 750 mL.gTVS−1 after pre-treatment, and the composition analysis of the biogas indicated that average methane yields represent up to 50% of the total production. This increase was observed after steam distillation and was attributed to the removal of the antimicrobial compound

Solid Waste Management in the Context of a Circular Economy in the MENA Region

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