Potential of Sustainable Concept for Handling Organic Waste in Tunisia

Decision-making in biogas production projects: Paradigms and prospection

The decision to implement a biogas production project involves the evaluation of multiple variables, such as the problem to be solved, the biodigester, business model, investment, and final products. An integrative literature review was conducted, in which 58 papers were obtained and relevant criteria for decision-making in biogas production projects from organic waste were identified. Three stages were considered in the analysis of the biogas production cycle: initial, plant, and final, as well as the economic, environmental, and social aspects that influence the decision. In general, the publications are dispersed over 30 different journals. The methodology used in most studies is empirical, quantitative, and descriptive, with data collected mainly from secondary sources. From the studies, 499 original criteria were identified, which were classified into one of four categories: economic, environmental, social, and technical, which cover a total of 39 sub-criteria. Economic and technical criteria were the most frequent in publications, while environmental and social criteria were less common and less prioritized. This suggests that there is a tendency to prioritize economic and technical dimensions over environmental and social dimensions in the analysis of the papers found. Finally, a preliminary decision-making model based on the findings is proposed.Implications: The integrative review of the literature on biogas and decision-making presented in this study holds significant implications for policy and practice in the field of sustainable energy production, organic waste management and decision making for public managers. By analyzing 159 papers and developing a comprehensive classification system, we have identified key sub-criteria for decision-making in various stages of the biogas production cycle. The predominance of technical and economic sub-criteria demonstrates the priorities of the current state of biogas projects and, at the same time, the need to promote balance between the technical, economic, social and environmental spheres in decision-making in order to achieve truly sustainable biogas projects. Policymakers can utilize these findings to promote the adoption of more holistic decision-making approaches that consider diverse factors, fostering the development of environmentally-friendly and socially equitable biogas ventures. This research provides valuable insights into aligning biogas production with broader sustainability goals and guides policymakers in formulating evidence-based strategies for the advancement of renewable energy technologies.

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.

Monitoring of Food Waste Anaerobic Digestion Performance: Conventional Co-Substrates vs. Unmarketable Biochar Additions

This study proposed the selection of cost-effective additives generated from different activity sectors to enhance and stabilize the start-up, as well as the transitional phases, of semi-continuous food waste (FW) anaerobic digestion. The results showed that combining agricultural waste mixtures including wheat straw (WS) and cattle manure (CM) boosted the process performance and generated up to 95% higher methane yield compared to the control reactors (mono-digested FW) under an organic loading rate (OLR) range of 2 to 3 kg VS/m³·d. Whereas R3 amended with unmarketable biochar (UBc), to around 10% of the initial fresh mass inserted, showed a significant process enhancement during the transitional phase, and more particularly at an OLR of 4 kg VS/m³·d, it was revealed that under these experimental conditions, FW reactors including UBc showed an increase of 144% in terms of specific biogas yield (SBY) compared to FW reactors fed with agricultural residue. Hence, both agricultural and industrial waste were efficacious when it came to boosting either FW anaerobic performance or AD effluent quality. Although each co-substrate performed under specific experimental conditions, this feature provides decision makers with diverse alternatives to implement a sustainable organic waste management system, conveying sufficient technical details to draw up appropriate designs for the recovery of various types of organic residue.

Drivers of Residents’ Home Composting Intention: Integrating the Theory of Planned Behavior, the Norm Activation Model, and the Moderating Role of Composting Knowledge

Home composting is judged as an effective municipal waste management option in which household contribution is essential, but it has a low adoption. The objectives of the study were to determine the factors that influence home composting intention and identify the moderating role of composting knowledge in the model, using the combined model of the theory of planned behavior (TPB) and norm activation model (NAM). A structured questionnaire was applied to a sample of 367 residents of Isfahan city, Iran, randomly selected. Data were analyzed using cluster analysis, discriminant analysis, PLS-SEM, and PLS-MGA. Cluster analysis grouped the three clusters based on the constructs of the integrated model, and this result was confirmed by discriminant analysis. Findings show that attitude, subjective norm, and perceived behavior control can predict the intention to compost. Study results confirmed the positive effect of awareness of the consequences of composting on ascribed responsibility to compost at home, of responsibility to the personal norm, and of the personal norm on intention to compost at home. Furthermore, it was observed that composting knowledge moderates the relationship between subjective norm and behavioral intention, and the one between perceived behavioral control and behavioral intention. The integrated model had more predictive power than the TPB model. The fit statistic of the integrated model was good and 71% of the variance for intention behavior toward home composting. The insights on factors affecting residents’ intention to compost obtained from this study can be used in measures and programs that reinforce and stimulate home composting.