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.

The increasing consumption of plastics and plastic products results in correspondingly substantial volumes of waste, which poses considerable environmental burdens. With the ongoing environmental actions, the application of circular economy on this waste stream is becoming inevitable. In this paper, the topics of plastics recycling, circular economy on plastics, and challenges to plastic waste recycling are critically reviewed. In the first part of this paper, the development of research on plastic recycling was viewed from 1950 until 2020 using the scientific database Web of Science, and 682 related studies were found and used to assess the changing research priorities along that timeline. The following sections discuss the potentials and requirements to enhance the quality of the produced recycled plastic, in connection with the factors that currently limit it. In conclusion, the quality of recycled plastic is generally determined by the homogeneity of the recovered plastic feed. There are various strategies which could be implemented to overcome the hindrances identified in the paper and to improve the quality of the recycled plastic, such as working on enhanced product designs for minimised waste heterogeneity and controlling the materials’ degree of contamination by applying advanced sorting.

Open disposal is the most common technique used for municipal solid waste (MSW) management due to the absence of sanitary landfills in Pakistan. The major cities and small towns in Pakistan have become a showcase of negligence and mismanagement of MSW, which results in deterioration of the environmental and social-life quality. Moreover, research has proved that inefficient handling (disposal) of MSW results in uncontrolled emissions of greenhouse gases (GHGs), mainly methane, and adds a significant share in global climate change. This study aims to estimate methane emissions from MSW disposed of at dumpsites and compare the GHG mitigation potential of different landfill strategies in specific climate and waste compositions in Karachi. The GHG estimations are based on lab-scale investigations conducted by simulating landfill conditions through the landfill simulation reactor (LSR) experiment. The synthetic MSW sample representing the composition of MSW generated in Karachi was used in the LSR experiment. Environmental sustainability and GHG mitigation potential of different landfilling strategies was evaluated by analyzing gas formation potential (GP₂₁) and respiration activity (RI₄) at the end of the experiment. This study revealed that the quantity of solid waste annually disposed of at dumpsites in Karachi possesses the potential to release about 3.9 Mt CO₂-eq. methane (with specific methane potential of 1.8 tCO₂-eq./tonne DM disposed) due to the biological decomposition of the organic fraction. Results show that the fresh waste disposed of at landfill sites in Karachi possesses about 92% and 94% higher GP₂₁ and RI₄, respectively, than the German allocated criteria for mechanically and biologically treated (MBT) waste for landfills Furthermore, sanitary landfills with post-aeration conditions showed higher GHG mitigation potential and low biological activity in the waste. The second highest GHG mitigation potential and lowest biological activity of the waste was noticed from bioreactor landfills with post-aeration conditions. The third number in GHG mitigation and reduced waste activity was noticed in the waste sampled from bioreactors without aftercare approach. The least GHG mitigation potential was noticed from the uncontrolled waste dumping (existing) approach with high residual gas potential and respiration index level. This lab-scale landfill simulation study can provide baseline data for further research and planning the development of new sustainable landfills in Karachi, Pakistan and in the region.

This review covers the decomposition mechanisms of various printing ink binder resins, with a particular focus on their behavior under extrusion conditions in the mechanical recycling process of polyolefin (PO) based plastic packaging. Thermal degradation and hydrolysis of the nitrocellulose (NC) — the most used binder for flexographic surface printing on single-layer flexible plastic packaging, occur concurrently during the mechanical recycling process under 160–210 °C. For other printing ink binders, polyurethane (PU) noticeable degradation takes place between 200 and 300 °C, mostly above 250 °C. However, with the involvement of humidity, degradation by hydrolysis can start from 150 °C. A similar effect is also discovered with the cellulose acetate (CA) derivatives, which are thermally stable until 300 °C and can be hydrolyzed at 100 °C. The thermal stability of polyvinyl butyral (PVB) is not influenced by humidity, with thermal stability ranging from 170 to 260 °C, depending on different types. Ultraviolet (UV)-cured acrylics are thermally stable until 400 °C. The hydrolysis degradation can take place at room temperature. Moreover, this review covers the thermal stability of different colorants used for printing ink application and elaborates on several thermal-stable alternatives of some common colors. This study further reviews how the binder resin affects the quality of recyclates, revealing it to be not only induced by the degradation of the binder resin but also by the immiscibility between the plastic and binder resin. In advanced recycling processes, mainly selective dissolution-precipitation and pyrolysis, the presence of binder resin and its degradation products could still affect the quality of the product. This review accentuates the imperative need for in-depth research to unravel the impact of printing ink constituents on the quality of recycled products.

One of the major applications (40% in Europe) of plastic is packaging, which is often printed to display required information and to deliver an attractive aesthetic for marketing purposes. However, printing ink can cause contamination in the mechanical recycling process. To mitigate this issue, the use of surfactants in an alkaline washing process, known as de-inking, has been employed to remove printing ink and improve the quality of recyclates. Despite the existence of this technology, there are currently no data linking the de-inking efficiency with typical printing ink compositions. Additionally, it is necessary to investigate the de-inking process under the process parameters of existing recycling plants, including temperature, NaOH concentration, and retention time. This study aims to evaluate the performance of commonly used printing inks with different compositions under various washing scenarios for plastic recycling in conjunction with different de-inking detergents containing surfactants or mixtures of surfactants. The results indicate that the pigments applied to the ink have no significant effect on the de-inking process, except for carbon black (PBk 7). Nitrocellulose (NC) binder systems exhibit high de-inkability (over 95%) under the condition of 55 °C and 1 wt.% NaOH. However, crosslinked binder systems can impede the de-inking effect, whether used as a binder system or as an overprint varnish (OPV). The de-inking process requires heating to 55 °C with 1 wt.% NaOH to achieve a substantial effect. Based on the findings in this work, breaking the Van der Waals forces, hydrogen bonds, and covalent bonds between the printing ink and plastic film is an essential step to achieve the de-inking effect. Further research is needed to understand the interaction between surfactants and printing inks, enabling the development of de-inkable printing inks and high-performance surfactants that allow for de-inking with less energy consumption. The surfactant and NaOH have a synergistic effect in cleaning the printing ink. NaOH provides a negative surface charge for the adsorption of the cationic head of the surfactant and can hydrolyze the covalent bonds at higher concentrations (>2 wt.%).

Low-density polyethylene is the most applied packaging plastic. The recycling rate of LDPE is low, especially for the material from the post-consumer source. The quality of the LDPE post-consumer recyclates is influenced by different contaminations, either intentionally or non-intentionally. Printing ink is one of the substances that is regarded as having a negative influence on the quality of LDPE recyclates. This study used a new type of nonionic surfactant oxirane, methyl-, polymer for de-inking as a pretreatment. Afterward, the LDPE film flakes were mechanically recycled in the laboratory. A melt flow index (MFI), differential scanning calorimetry (DSC), and tensile strength analysis were carried out. This work reported the de-inking effect of a new type of nonionic surfactant. However, no evidential correlation between the rate of color removal and the improvement in the rheological, thermal, and mechanical properties can be identified from the result of this study.