Editorial: Sustainable Municipal Solid Waste Management: A Local Issue with Global Impacts

On a global level, communities are generating and disposing of increasing quantities of solid waste. This waste includes different categories like municipal solid waste [1], industrial solid waste [2] and agricultural waste [3]. Unless managed in a sustainable manner, such wastes will lead to public health risks, adverse environmental impacts and other socio-economic problems [4]. Therefore, regulations should be enforced to encourage sustainable practices like reduction, reuse and recycling of solid waste.

This special issue of Sustainability provides an overview of sustainable solid waste management by publishing articles on recent research concepts, models and case studies, in order to stimulate the scientific potential of this field and for a better understanding of the circular economy principles. To achieve that, specialists from a range of disciplines, practices and sectors were invited to contribute their research findings. The number and diversity of submissions that we received to the call from different regions of the world indicate the growing importance of sustainable solid waste management. The special issue consists of eight articles. Each of them contributes to the knowledge in the field by presenting the features of cutting-edge treatment technologies and the latest modeling techniques. From these eight articles, several unique lessons have emerged.

The first article [5] tackled the issue of sustainable management and the use of biosolids in Columbia. By adopting the Prospective Analysis (MicMac and Mactor) and Social Networks approach, the researchers managed to analyze those factors that influence the management and use of biosolids. The application of such methodology that was focused on biosolids allowed for the prioritization of determinants, the evaluation of the level of involvement and communication between actors and other aspects that have not been considered previously in the management of wastewater treatment plants in Colombia. The study concluded that there is a weak linkage between the stakeholders which requires work to improve the communication skills between them.

The challenge of marine plastic littering in Manila, Philippines was addressed in the second article [6]. The researchers used structural equation modeling to examine the practical challenges and opportunities to influence the reduction of marine plastic littering. By using an online survey, the investigators constructed the model which had later been subjected to validation through interviews and focused group discussions, where the developed model had been validated to a good internal consistency. The findings revealed that environmental governance, in terms of waste management policies and guidelines, COVID-19 regulations for waste management, community participation and socio-economic activities had a positive impact on decreasing the amount of marine plastic littering.

A case study to characterize and plan household waste in Algeria was covered in the third article [7]. To assess the spatial distribution of the waste and potential drivers of waste production, the study adopted a geospatial analysis by integrating the principal component analysis with GIS. The results showed that household waste management is influenced by factors related to the size of the settlement and the characteristics of waste management companies. The study indicated that the urban waste generation rate is estimated to be at 0.8 kg·inhab·day⁻¹, while the recycling rate is around 7%, composting 1% and the rest of municipal waste flow is disposed of in sanitary landfills or dumpsites. The investigators concluded that a combination of multiple regression analysis and principal component analysis is efficient to describe and understand waste production.

The fourth article [8] dealt with the composting process by converting the organic fraction of municipal solid waste to mature compost using the composting bin method. Several materials, including animal waste, agricultural waste and humic substances, were added to the municipal waste and subjected to composting. Temperature, pH, EC, organic matter (OM percent), the C/N ratio and micronutrients (N, P, K) were monitored on a weekly basis. The study concluded that bin composting may be used as a quick check to ensure that the output of the long-term public projects will meet the sustainability requirement, enhance the ecosystem services and will mitigate the climate change impact that may be caused by the disposal of the solid waste in the hot climate regions.

Waste to Hydrogen energy was the topic which was covered by the fifth article [9]. The researchers examined the production of hydrogen energy by processing an aluminum scrap. Ball-milled hydro-reactive powders of Mg-Al scrap with 20 wt.%, with and without additives were prepared. Their hydrogen yields and reaction rates in a 3.5 wt.% NaCl aqueous solution at 15–35 °C were estimated and compared. The results showed that samples with 20 wt.% Wood’s alloy and with no additives demonstrated the highest hydrogen yields of (73.5 ± 10.0)% and (70.6 ± 2.5)%, respectively. However, their maximum reaction rates were the lowest. On the other hand, the results indicated that the variation in reaction kinetics was attributed to the difference in the scrap powder particle size, where the samples with a salt additive had the finest particle size and the fastest reaction kinetics at the beginning of the reaction.

An interesting topic is addressed in the sixth article [10]. A case study has been presented to demonstrate the role of Eco-Industrial parks in promoting the circular economy in Russia. Given the fact that the circular economy is one of the priorities of the country’s economy, the researchers adopted the life cycle assessment as a tool to compare two scenarios of solid waste management. The first scenario is the disposal of the solid waste at the landfill, while the second one is to divert the generated solid waste from landfills to an eco-industrial park, where it is subjected to processing for materials and energy recovery. The life cycle analysis showed that diverting 1.813 million tons of mixed municipal solid waste that is generated in Moscow to EIP would lead to a reduction in environmental impacts. The total global warming potential of the EIP scenario is less, by 59%, than the direct landfilling scenario, while the eutrophication, acidification, smog and ozone depletion are less, and fossil fuel depletion impacts under the second scenario are less, by 81%, 26%, 18% and 81%, respectively. The study indicated that the adoption of a circular economy in Russia is still in its early stages. To create an enabling environment for the promotion of a circular economy, the study recommended overcoming several institutional, technical and social barriers, where the Russian higher educational institutions can play a major role in overcoming such obstacles.

Article seven [11] was devoted to solid waste management in the MENA region in the context of a circular economy. The paper presents a comprehensive overview of the national municipal solid waste systems of 10 countries in the MENA region with a detailed evaluation of four countries (Jordan, Egypt, Algeria and Morocco). Current practices of the solid waste management adopted and the approaches followed by each country to integrate the circular economy principles in their solid waste management were identified. The researchers indicated that the solid waste management in the studied countries is still disposal driven, where it ranges from 73% in the UAE up to 97% in Libya. Furthermore, the organic fraction constitutes the highest percentage of the solid waste stream that ranges from 504% in Algeria to 70% in Morocco. Full cost recovery of the solid waste services does not exist in any of the studied countries. Furthermore, the existing legal and administrative frameworks do not enable the adoption of a circular economy. Therefore, the study recommends that the governments should promote an integrated solid waste management hierarchy and set up a national policy regarding the diversion of waste from landfill by making a shift from waste disposal toward waste management and the circular economy.

Finally, the last article [12] conducted a techno-economic analysis of the Al-Karak solid waste sorting plant in Jordan. The article investigated the possible technical and economic performance of the sorting plant in order to achieve financial sustainability and increase profits to cover its operating costs. Possible different equipment and material flow through the plant were proposed. To assess the feasibility of the proposed options, an economic model was used based on three economic factors, which are net present worth (NPW), return on investment (ROI) and payback period values. The results showed that the input materials contain a high fraction of recyclable materials like paper, cardboard, plastic and metals, which account for 63% of the solid waste stream. The analysis shows that to be economically feasible, the plant operation should be on a two or three shifts basis, where the rate of return will be 3.5 and 4.4 with a payback period of 3 and 2 years, respectively.