With nearly 40% of the total plastics produced being used for packaging, up to five trillion plastic bags are consumed in the world annually. The inadequate disposal of plastic waste and its persistence has become a serious challenge/risk to the environment, health, and well-being of living creatures, including humans. The natural degradation of plastics is extremely slow; large pieces of plastic may break down into microplastics (MPs) (1 μm–5 mm) or nanoplastics (NPs) (<1000 nm) after protracted physical, chemical, and/or biological degradations. A brief overview of the transport of micro- and nanoplastics in the aquatic, terrestrial, and atmospheric environments is presented. Details are provided on the exposure routes for these waste materials and their entry into humans and other biota through ingestion, inhalation, and dermal contact. The greatest concern is the cumulative impact of the heterogeneous secondary MPs and NPs on planetary and human health. Inhaled MPs and NPs have been shown to affect the upper respiratory tract, lower respiratory tract, and alveoli; prolonged exposure can lead to chronic inflammatory changes and systemic disease. These can also lead to autoimmune diseases and other chronic health conditions, including atherosclerosis and malignancy. Sustainable mitigation strategies to reduce the impact of MPs/NPs include source reduction, material substitution, filtration and purification, transformation of plastic waste into value-added materials, technological innovations, etc. Multidisciplinary collaborations across the fields of medicine, public health, environmental science, economics, and policy are required to help limit the detrimental effects of widespread MPs and NPs in the environment.

Managing red mud (RM), a solid waste byproduct of the alumina recovery process, is a serious ecological and environmental issue. With ~150 million tons/year of RM being generated globally, nearly 4.6 billion tons of RM are presently stored in vast waste reserves. RM can be a valuable resource of metals, minor elements, and rare earth elements. The suitability of RM as a low-grade iron resource was assessed in this study. The utilization of RM as a material resource in several commercial, industrial operations was briefly reviewed. Key features of iron recovery techniques, such as magnetic separation, carbothermal reduction, smelting reduction, acid leaching, and hydrothermal techniques were presented. RMs from different parts of the globe including India, China, Greece, Italy, France, and Russia were examined for their iron recovery potential. Data on RM composition, iron recovery, techniques, and yields was presented. The composition range of RMs examined were: Fe₂O₃: 28.3–63.2 wt.%; Al₂O₃: 6.9–26.53 wt.%; SiO₂: 2.3–22.0 wt.%; Na₂O: 0.27–13.44 wt.%; CaO: 0.26–23.8 wt.%; Al₂O₃/SiO₂: 0.3–4.6. Even with a high alumina content and high Al₂O₃/SiO₂ ratios, it was possible to recover iron in all cases, showing the significant potential of RM as a secondary resource of low-grade iron.

Thermo-electrochemical cells (also known as thermocells, TECs) represent a promising technology for harvesting and exploiting low-grade waste heat (<100–150 °C) ubiquitous in the modern environment. Based on temperature-dependent redox reactions and ion diffusion, emerging liquid-state thermocells convert waste heat energy into electrical energy, generating power at low costs, with minimal material consumption and negligible carbon footprint. Recent developments in thermocell performances are reviewed in this article with specific focus on new redox couples, electrolyte optimisation towards enhancing power output and operating temperature regime and the use of carbon and other nanomaterials for producing electrodes with high surface area for increasing current density and device performance. The highest values of output power and cell potentials have been achieved for the redox ferri/ferrocyanide system and Co^2+/3+, with great opportunities for further development in both aqueous and non-aqueous solvents. New thermoelectric applications in the field include wearable and portable electronic devices in the health and performance-monitoring sectors; using body heat as a continuous energy source, thermoelectrics are being employed for long-term, continuous powering of these devices. Energy storage in the form of micro supercapacitors and in lithium ion batteries is another emerging application. Current thermocells still face challenges of low power density, conversion efficiency and stability issues. For waste-heat conversion (WHC) to partially replace fossil fuels as an alternative energy source, power generation needs to be commercially viable and cost-effective. Achieving greater power density and operations at higher temperatures will require extensive research and significant developments in the field.

The widespread generation of, ever increasing volumes of and the sustainable management of solid wastes are global issues of great concern. Due to wide variations in composition and associated complexities, significant efforts are required for their collection, processing and environmentally safe disposal in a cost effective manner. An overview of solid wastes is presented in this article with a specific focus on municipal solid wastes and industrial waste from the iron/steelmaking and aluminium industries. Key waste issues such as its sources, compositions, volumes, the factors affecting waste generation and waste processing are first discussed, followed by a further discussion regarding recycling, resource recovery, disposal and the associated environmental impacts. In a special case study, waste generation and management in Chile is presented in greater detail. Detailed information is provided on government initiatives and legislation for integrated solid waste management and its movement towards a circular economy. Measures include regulations on waste management framework which concerns the transboundary movements of hazardous wastes, persistent organic pollutants, the closure of mining activities and installations and restrictions on plastics disposal. With Chile being world’s largest producer of copper, significant efforts for mining waste management, its infrastructure and procedures are being put in place to reduce the environmental impact of the mining sector and its associated waste generation.