Microplastics (MPs) have been identified as an emerging soil pollutant and a global environmental concern. Scientists have recently paid attention to the contamination of soil by MPs as their detrimental impacts on soil systems are largely unknown. MPs are considered to be vectors for other soil contaminants, such as potentially toxic elements (PTEs) and organic contaminants. PTEs are persistent contaminants and are often released into soils in large quantities. MPs adsorb PTEs, mainly via electrostatic attraction and surface complexation, and increase their mobility in soils. These complexes can be easily absorbed by plants; hence, the accumulation of PTEs in plants can be enhanced in both microplastic and PTE contaminated soils. Furthermore, there is a high risk of food chains contamination by PTEs due to crops grown in both microplastic and PTE-contaminated soils. Consequently, countermeasures including policy- and governance-based approaches that target circular economy as well as reduce, reuse, recycle (3R) applications are being discussed around the world to minimize the environmental contamination of MPs.

There is a widespread interest in converting organic waste into compost fertilizer to extend the life of landfills, create economic and environmental benefits, and ultimately reduce the pressure on local governments in managing the ever-increasing complexity of municipal solid waste. However, composting is still seldom considered as a strategic element. There is also very little evidence available of its economic feasibility. This study, therefore, aims to analyze key factors that influence the economic feasibility of municipal composting plant and identify a range of plant capacity or scale where a composting project could have higher opportunity to be financially sustainable. A cost–benefit analysis (CBA) was carried out using the data gathered from five composting plants in Asia, including Surabaya, Bali and Bekasi in Indonesia, Beijing in China, and Matale in Sri Lanka. The results identified that the medium-scale and lower large-scale composting plants have an optimal opportunity for being financially feasible as compared with the smaller and larger capacity plants. The study also identified that the economic viability of the composting plants depends on the number of factors, such as selection of suitable processing methods, technologies, scale, quality of product and marketing strategies. The advantages of the medium and lower large-scale composting plants are (1) waste input and product quality are easier to control than larger scale compost plants, and (2) there are extra income opportunities such as tipping fees and carbon credits that are limited in the case of small-scale composting plants. The scale of composting plant is one of the key factors to be considered at the initial stage of planning composting plants.

Due to its ability to recover both material and energy from organic waste, biogas technology is considered one of the best technology for treating organic waste. While in many emerging Asian countries more than 50% of municipal waste is organic waste, the amount of organic waste treated with biogas technology remains very limited. This study identified key challenges faced by practitioners in sustaining biogas plants from literature and interviewed a number of sustainably operating biogas plant managers and, based on the findings, developed an implementation framework to help decision makers and practitioners in planning a sustainable municipal organic waste biogas plant facility.

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.

The global demand for plastic is expected to double in the next 20 years. The increasing demand for Single-Use Plastic Products (SUPPs) has become one of the main environmental problems in many developing countries, including Sri Lanka, through direct and indirect means, in the way of excessive consumption and the pollution of the environment through waste generation. In this way, there is a pressing need to accelerate the sustainability evaluation, comparison, impact mitigation and policy recommendation of SUPPs to address the environmental impacts and sustainable development. Therefore, this study aims to quantify and compare the environmental impacts of SUPPs for policy decision making in Sri Lanka using life cycle assessment (LCA) techniques. Accordingly, the most popular and widely used single-use plastic products, which are under consideration for regulation in Sri Lanka, and their possible alternatives, are considered for this LCA study. The results reveal that SUPPs produced using polystyrene (PS), polypropylene (PP), low-density polyethylene (LDPE), high-density polyethylene (HDPE), and polyethylene terephthalate (PET) have a significant contribution in all life cycle stages, in terms of global warming potential (GWP) and endpoint impact categories. However, the outcomes of the study reveal that the net GWP impact of SUPPs that have recycling practice at the end of life shows better performance compared to incineration and landfill. In addition, the polylactic acid- (PLA)-based products also show a significant impact on mid- and end-point GWP impact categories. Remarkably, the midpoint analysis of PLA-based products and their alternatives emphasized that PLA production was the most impactful for most of the midpoint impact categories due to PLA resin production, which contributes significantly to all impact categories. In particular, for the pesticide bottles with the preferred end-of-life option of incineration, the HDPE indicates a 7.6% lower GWP compared to PET. For reusable steel cutlery, the largest GWP-associated life cycle stage is the user phase (97.5%), which includes cleaning the cutlery. However, the overall reduction in GWP in the use of steel, considering the best (PS with recycling) and worst (PS with incineration) case scenarios, with single-use items are 0.01 and 0.05 kg CO₂ (eq), respectively. In the case of pesticide bottles, with the preferred end-of-life option being incineration, the HDPE indicates a 7.6% lower GWP compared to PET. the study reveals that conducting LCA will facilitate scientific decision making for policy interventions related to SUPPs and their processes. Notably, the study shows that, at present, the capability of conducting LCA studies to evaluate the sustainability performance of SUPPs in Sri Lanka is limited due to the lack of life cycle inventory (LCI) data availability on SUPPs and relevant waste management practices in Sri Lanka.