Estimation of spontaneous waste ignition time for prevention and control of landfill fire

Global perspective of municipal solid waste and landfill leachate: generation, composition, eco-toxicity, and sustainable management strategies

Globally, more than 2 billion tonnes of municipal solid waste (MSW) are generated each year, with that amount anticipated to reach around 3.5 billion tonnes by 2050. On a worldwide scale, food and green waste contribute the major proportion of MSW, which accounts for 44% of global waste, followed by recycling waste (38%), which includes plastic, glass, cardboard, and paper, and 18% of other materials. Population growth, urbanization, and industrial expansion are the principal drivers of the ever-increasing production of MSW across the world. Among the different practices employed for the management of waste, landfill disposal has been the most popular and easiest method across the world. Waste management practices differ significantly depending on the income level. In high-income nations, only 2% of waste is dumped, whereas in low-income nations, approximately 93% of waste is burned or dumped. However, the unscientific disposal of waste in landfills causes the generation of gases, heat, and leachate and results in a variety of ecotoxicological problems, including global warming, water pollution, fire hazards, and health effects that are hazardous to both the environment and public health. Therefore, sustainable management of MSW and landfill leachate is critical, necessitating the use of more advanced techniques to lessen waste production and maximize recycling to assure environmental sustainability. The present review provides an updated overview of the global perspective of municipal waste generation, composition, landfill heat and leachate formation, and ecotoxicological effects, and also discusses integrated-waste management approaches for the sustainable management of municipal waste and landfill leachate.

Smart technological options in collection and transportation of municipal solid waste in urban areas: A mini review

The rapid increase in quantities and the mismanagement of municipal solid waste (MSW) in developing countries are increasing the environmental impacts such as air, water and soil contamination. The present scenario of MSW management deals with numerous issues such as lack of technological resources, strategical management, social awareness, public participation, etc. Globally, numerous efforts in the form of new policies, schemes and regulatory acts have been made to develop a systematic collection and transportation (C&T) method using advanced, integrated technologies. However, very few studies have addressed this issue for low- and middle-income countries due to the lack of availability of reliable resources and data sets. This paper addresses the present challenges in C&T methods and highlights the application of information communication technology in monitoring, capturing, data management, planning, live tracking and communication. This systematic mini-review is based on the availability of technical resources, consumer acceptance and cost-effectiveness of different technologies in managing the processes. The study revealed that the C&T methods in most developed countries are designed based on their geographical stretch, climatic factors, waste characteristics and compatible technology, resulting in sustainable MSW management. However, developing countries have followed the same monotonous approach in managing their MSW, which fails in C&T process. The case study provides a valuable resource for researchers and policymakers to frame a better C&T process based on the recent technological interventions, infrastructure development, and social and economic status.

Detection and extinguishment approaches for municipal solid waste landfill fires: A mini review

Municipal solid waste (MSW) management is getting more attention in the present scenario. Even though various technologies like incineration, gasification, pyrolysis and waste-to-energy plants have been developed, landfills are still the major disposal option for MSW management. MSW at landfill creates issues that are highlighted at a global level like the fire at Deonar dumping site in Mumbai, India was visible and captured by the space satellites, leading to environmental pollution. Detection and extinguishment of landfill fires at surface and sub-surface in their early stages are the major concern. Thermal imaging camera can be used to know solar radiation effect by identifying the hotspots during the day and the night time for understanding aerobic degradation effect on the surface fire. Sub-surface gas concentrations and its combinations affecting the temperature gradient can be studied for a better understanding of sub-surface fires in their early stages. The use of class 'A' foams with water, which reduces the surface tension of water, can be carried out for landfill fire extinguishment. The application of water in the form of water fog will extract a large amount of heat and block the availability of oxygen for the fire. This mini review presents the sources of fuel, heat, oxidant for landfill fire and its development process, associated pollution on air, water, land and human health due to landfill fire and methods for its extinguishment possibilities.

Impact of municipal solid waste landfill leachate on biogas production rate

Landfills/open dump sites are the final disposal facilities for municipal solid waste (MSW). These sites undergo continuous process of biochemical reactions and anaerobic degradation, which make them prone to generation of landfill gas (LFG) and leachate. Worldwide, the quantitative and qualitative assessment for leachate treatment and management has been a growing concern. The present study investigated the physico-chemical characteristics and heavy metal parameters for fresh, 3-month, 6-month and 3-year old landfill leachate samples. The total dissolved solids (13280 mg/l), alkalinity (13000 mg/l), chemical oxygen demand (42000 mg/l) and total organic carbon (16500 mg/l) was found to be maximum in 3-year old leachate sample. While, the 3 and 6-month old leachate samples had maximum heavy metal concentration. The attempt was also made to identify the key parameters responsible to enhance biogas production yield from different ages of MSW. The substrate combinations of MSW and 3-year old leachate samples was prepared at varying proportion. The study was performed in three cycles and the volume of leachate diffused in each cycle was kept constant. The control samples with no leachate diffusion was also prepared to compare the percentage increase in biogas production rate. It was found that the cumulative methane (CH₄) production from fresh (358 ml/g) and 3-month old MSW (273 ml/g) was maximum, and the overall percentage increase was 43% and 32%. It was also conclusive that the excess leachate diffusion of >15 ml results in low calcination behaviour and CH₄ production rate. The response surface methodology was used to correlate and validate independent input variables (volatile solids, C/N ratio and leachate concentration) responsible for maximum CH₄ yield.

An investigation on mobility of heavy metals for assessing the reusability of soil-like material reclaimed from mining of municipal solid waste dumpsites

Landfill mining, often referred to as "bio-mining", enables the recovery of resources, including combustible, compostable, and recyclable fractions from landfills. However, most of the materials mined from old landfills mainly consist of soil-like materials (SLM). The reuse of SLM depends on the concentration of contaminants, such as heavy metals, soluble salts, etc. A sound risk assessment requires sequential extraction to determine the bioavailability of heavy metals. This study focuses on the mobility and chemical speciation of heavy metals in SLM from four old municipal solid waste dumpsites in India by performing selective sequential extraction. Additionally, the study compares the results with those of four previous investigations to identify international similarities. It has been observed that Zn was mainly available in the reducible phase (average 41%), whereas Ni and Cr proved to have the highest distribution in the residual phase (64% and 71%, respectively). Pb analysis showed a large portion in the oxidizable phase (39%), while Cu was mainly present in the oxidizable (37%) and residual (39%) phases. Similarities with previous investigations were observed for Zn (primarily reducible 48%), Ni (residual 52%), and Cu (oxidizable 56%). Correlation analysis showed that Ni correlated with all heavy metals (ρ = 0.71-0.78), except with Cu. The present study suggested that Zn and Pb are associated with a high risk of pollution due to their maximum distribution in the bioavailable phase. The findings of the study can be used to assess the heavy metal contamination potential of SLM prior to its reuse in offsite applications.

Open defaecation by proxy: Tackling the increase of disposable diapers in waste piles in informal settlements

Disposable diapers are becoming increasingly popular and present an emerging challenge for global waste management, particularly within LMICs. They offer a cheap and convenient way for caregivers to manage child excreta; however, insufficient understanding of safe disposal methods, combined with limited access to waste management services results in hazardous disposal. Used diapers are being increasingly found dumped in the open environment, including in water bodies and in open fields, leading to faecal contamination of the environment and an enhanced risk of transmission of faecal-oral diseases such as cholera and typhoid. United Nations SDG 6 aims to end open defaecation globally by 2030; however, improper disposal of used diapers will hamper progress towards reaching this goal. In this review, we identify current trends in use and subsequent disposal of single use disposable diapers in LMICs, and critically discuss the environmental and public health impacts of current practices, and potential solutions to address these challenges. Contemporary methods for managing the disposal of single use diapers for communities in LMICs tend to be cost prohibitive with few alternative options other than dumping in the environment. Modern cloth diapers offer a low waste alternative to disposable diapers but often carry an unaffordable high upfront cost. Here, in addition to advocating improved efforts by governments to upgrade access and quality of waste management services, we recommend the design and implementation of intervention schemes aimed to increase awareness of safe and hygienic disposal practices for disposable diapers.