Waste Management & Research: The Journal for a Sustainable Circular Economy

Although the ban on plastic bags is gaining in prominence as a policy option to manage plastic bag litter, there are mixed views on its rationale and effectiveness. This study employs a systematic literature review to understand considerations, benefits and unintended consequences of banning plastic bags. The review’s results pointed to the limited success of a plastic bag ban owing to lack of suitable alternatives, limited state capacity to monitor and enforce the ban, thriving black market, structural and instrumental power of the plastic industry. The power of the industry was manifested by the covert practice of deflecting accountability to consumers by focusing on business-oriented solutions, including an inclination towards self-regulation. The findings of this study underscored the need for a global treaty to address the transient nature of plastic bag litter and moving away from the symbolic gesture of targeting only plastic shopping bags but considering the environmental impact of all forms of plastic such as straws, foamed plastics, plastic bottles and caps. There is a general consensus in literature that the end of plastic shopping bags is not nigh due to their utilitarian benefits. This study therefore recommends the promotion of a circular economy focusing on ecological modernisation, sustainable plastic bag manufacturing and recovery strategies such as recycling as a long-term strategy. A significant strand of literature reviewed also recommends the adoption of community-driven approaches such as voluntary initiatives as opposed to a plastic bag ban as they proved to be effective in promoting environmental citizenship behaviours in countries such as Finland.

Soil has been used as building material for thousands of years with a decrease in popularity after the industrial revolution. Nowadays, there is a growing interest in the implementation of unfired soil-based building solutions for their low environmental impact, performances and availability. Traditional soil construction techniques have recurrently included vegetal fibres to enhance soil performance and recent studies highlight a predominant use of agro- and non-agro-waste for unfired soil construction. The article reviews the state-of-the-art of the use of excavated soil and biowaste in the construction industry including a novel focus on urban-only waste and on building technologies using the integration of these two secondary construction material flows. Our literature review highlights a lack of references about the joint use of these secondary resources. Finally, future research orientations are suggested to promote their implementation in the building sector, which could improve urban waste management.

Construction industry has adopted reverse logistics (RL) concept to manage high volumes of demolition waste (DW). However, DW RL supply chains (RLSCs) were found to be suffering from uncertainties, information deficiencies, and uncoordinated material flows. Improving supply chain integration (SCI), specifically external integration, across DW RLSCs was identified as a possible solution to overcome such problems. Despite this, studies that focus on external integration in DW RLSCs are limited. Using a systematic literature review (SLR), this study explores external integration in DW RLSCs. Sixty-six articles from three databases published between 2006 and 2020 were subjected to descriptive and content analysis. Arrangement of material, information, and financial flows across DW RLSCs, inhibitors of external integration, and potential measures for improving external integration were analyzed. Accordingly, material, information, and financial flows across DW RLSCs were mapped, and inhibitors of external integration, along with potential measures for improving external integration were identified. As the key outcome of this SLR, these findings were developed into a conceptual framework, which shows the main factors that inhibit and improve external integration in DW RLSCs. The framework will be useful in guiding further empirical research and informing industry practice. Several future research directions are also proposed to expand knowledge around the research domain.

Acid tar sludge (ATS) is a hazardous waste generated in steel plants as a process by-product. ATS disposal is a major challenge for the steel industry around the world and specifically for developing nations. Hazardous wastes are usually disposed of in a dedicated expensive thermal treatment plant as per existing rules. Due to inadequate capacity of treating the total amount of hazardous waste, study of other economical options are required. India generates over 7.2 million metric tonnes of hazardous waste annually as per Central Pollution Control Board (CPCB), Government of India. Thus, co-processing of ATS in cement plant as an alternative means of disposal was studied based on a number of trials. During the five trials of 5 day each, feed rate of ATS was maintained at 0.4 tonne per hour (TPH) with an average coal feed rate of 10 TPH. No incremental variations in emissions were observed during the trials. The analysis further revealed insignificant impact on clinker quality, leach behaviour and cement property. The study also showed negligible impact on ambient air quality based on NOx, SO₂, RSPM, SPM measurement at varying location around the cement plant. Thus, co-processing of hazardous waste such as ATS in cement plant can be an effective way to address the hazardous waste disposal problem in developing countries such as India.

As urbanisation intensifies in Brazilian cities, life quality in urban centres becomes a challenge for policymakers, and transitioning urban systems to sustainability is required. Circular economy concepts may contribute to face them, especially those owing to municipal solid waste (MSW) management. Curitiba, a Brazilian municipality known for its innovative initiatives towards sustainability. Despite a long tradition in recycling inert waste, MSW system struggles to promote composting even considering a decade in force national law. Decentralised composting through the Urban Agriculture Program (UAP) is the city’s strategy to tackle this struggle. This strategy faces difficulties as, even if urban agriculture facilities seem to be a promising context, closing the agricultural loop within the city bounds was not possible in the 24 urban farmers communities trained in composting techniques. The literature has shown difficulties in government experiments to promote practices in the long run and several experiences in Brazil are already described. This study reveals cultural barriers that influence adoption of domestic composting, by following a secondary data review on past experiences with interviewing and observing participatively urban farms communities. From the fieldwork, cultural perspectives from four different relevant actor roles in the UAP were elaborated and conflicts between them revealed cultural barriers hindering composting practices adoption. Recommendations based on these barriers argue for bottom-up approaches for transition experiments and recognising the sense material and technical support makes to practitioners.

In this study, characteristics of the long-term landfill settlement are analysed and the starting date of residual settlement is deduced using the data of the landfill 1 of the Gimpo Metropolitan Landfill (GML) measured for 27 years. The landfill 1 is a multi-staged municipal solid waste landfill where dykes are constructed after landfilling for subsequent waste fills. The landfilling began in 1992 and finished in 2000, and the waste settlement measurement continued throughout this period. The older waste of the lower lift shows higher biodegradation and larger settlement than the waste of the upper lift, which acts as vertical load. Large settlement occurred in the lower lifts due to the collapse of waste voids caused by the overburden load of the upper lifts after biodegradation of waste in the lower lifts during long-term landfilling. In the conventional landfills, that is, mono-layer landfills, the time-dependent settlement generally occurs after the stress-dependent settlement. But, most of the time, this landfill showed mainly the time-dependent settlement. The duration, at which the biodegradation of organic matters is reduced and the residual settlement begins, was 8.8 years in average and the date range was from 7.6 to 11.7 years considering each disposed block in landfill 1. This date is obtained by calculating from the mid-point time of the landfilling duration.

Slope failure in municipal solid waste (MSW) landfills is a common environmental disaster that poses serious ecological and health risks. Landfill slope stability (SS) is sensitive to leachate levels and gas pressure (GP) caused by the degradation of organic material, but the extent of these combined effects remains poorly understood. In this study, a simplified landfill GP calculation method is presented and a circular slide method that considers the combined effects of leachate and GP is established. The results show that the landfill GP is mainly affected by the gas production rate, gas conductivity of the solid waste (SW), and landfill depth. The safety factor of landfill SS is also significantly lower when GP is considered. The distribution of GP is affected by the depth of the failure circle and SW. Landfill slope instability can be explained by localized damage caused by GP breakthrough of the filled SW. This study probably provides important guidance for the design, operation, and management of MSW landfills.

Sludge-based activated carbons (SACs) prepared from sewage sludge and corn straw, were modified by ferric nitrate, and the unmodified SAC and modified SAC were used as the adsorbing agent to treat the landfill leachate, the elimination capacity for chemical oxygen demand (COD) and organic matter in leachate were studied. Based on this, the physicochemical properties of SACs and the components changes in leachate were analyzed and characterized by X-ray photoelectron spectroscopy and three-dimensional fluorescence spectroscopy. The results showed that under optimal experimental conditions, the elimination capacities of SAC372 for COD, biological oxygen demand over 5 days, and NH₄⁺–N in the leachate were 81.58%, 54.73%, and 69.08%, respectively; while the adsorption capacities of modified SAC for these three substances were 86.25%, 63.51%, and 79.15%, respectively. The ferric nitrate modification improved the ability of SAC to eliminate COD and organic matter from leachate slightly, and made the adsorption occurred easily. The adsorption process of unmodified SAC was dominated by multi-layer adsorption, while the adsorption process of modified SAC was dominated by monolayer adsorption. The mass fraction of Fe (2p) in modified SAC remarkably increased, from 0.70% to 26.01%, organic functional groups certain phase of Fe oxides with different valence states were generated in SAC, which provided a substrate for iron–carbon micro electrolysis. After adsorbed by unmodified SAC and modified SAC adsorption, the total fluorescence intensity of in the leachate increased by 17.01% and 116.84%, respectively. Both two SACs could decompose the humic acid-like substances into aromatic protein organic compounds, and modified SAC could further decompose the soluble microbial byproduct-like substances.

To reduce waste volumes and recover valuable products, char was synthesized via co-pyrolysis of rice straw (RS) with spent tires, sulfur wastes, and CO₂. The inclusion of wastes and CO₂ in pyrolysis of RS was hypothesized to enhance the sorption ability of char for various contaminants, including 2,4-dinitrotoluene (DNT), 2,4-dichlorophenol (DCP), lead, barium, chromate (CrO₄²⁻), and selenate (SeO₄²⁻). Using a lab-scale electrical furnace, the co-pyrolysis was conducted, and the soprtion capacity of char was evaluated via a series of batch sorption experiments. The maximum sorption capacity of spent tire–RS char for DNT was 16.8 ± 0.2 mg g⁻¹, much higher than that of RS biochar (10.1 ± 0.3 mg g⁻¹) due to increasing carbon content from the spent tires. The sorption of DCP to the spent tire–RS char was also enhanced via hydrophobic sorption to carbon residues, although not to the same degree of DNT due to deprotonation of the DCP. Compared with RS biochar, co-pyrolysis with raw sulfur wastes and CO₂ enhanced sorption of lead, barium, and chromate, which can be attributed to increased cation and anion exchange capacities resulting from developments of oxygen or sulfur-containing functional groups. Sorption of selenate was strongly affected by pH. The results suggest that co-pyrolysis of agricultural and industrial wastes and CO₂ is a promising option for the final waste disposal and the production of valuable char, which can be selectively customized for various types of contaminants as sorbents.

The fast population growth in the metropolitan areas of the province of Tehran has led to the scarcity of land and inevitable expansion of urban construction to non-engineered fills and construction/demolition waste disposal sites. An abandoned aggregate quarry, infilled with construction wastes over 16 years, has been recently selected for a new development project consisting of several multi-storey commercial and residential complexes (up to 7 storeys). This study was aimed at delineation of the waste materials, geophysical and field and laboratory geotechnical characterisations prior to foundation design, and the design of the excavation programme. Geo-electric resistivity test was used to delineate the waste materials from natural ground materials. Surface and downhole P- and S-wave velocity measurements were used for the estimation of dynamic elastic properties of the wastes. In total, 12 boreholes (15–30 m deep) along with 10 test pits (4–8.5 m deep) provided the opportunity for visual observations of the waste materials, necessary sampling for compositional analyses, laboratory shear strength tests and determination of waste deposit thickness in different regions of the site. Manual standard penetration test (SPT) was also used to evaluate in situ stiffness of the fine materials of the waste. Six field plate load tests were performed on the waste materials at their natural water content conditions and at saturated (flooded) ground conditions to determine their compressibility and the ground reaction modulus. Based on the results from extensive characterisation programme, it was concluded that the waste materials are in a metastable state and exhibit heterogeneity across the site. The findings of current case study can provide new insight into construction/demolition waste behaviour, using available geophysical and geotechnical tools and testing procedures for characterisation, and eventually helping in reliable design of foundations for new development projects.

Source separation plays a pivotal role in sustainable and integrated Municipal Solid Waste Management (MSWM) and in achieving a circular economy in Asia. However, it is still not an official practice, and many cities continue to utilise open dumping, involving receiving mixed waste without pre-treatment. This paper, therefore, examines the advantages of source separation of MSW and explores the main factors for success in the planning and implementation of official source separation programmes in cities in Asia. Analysis of the results for two case studies in India and Japan could be used to strengthen capacities of policymakers in designing and implementing official source separation systems to facilitate material recovery and achieve sustainable development in Asia.