Determination of ignition temperature of municipal solid waste for understanding surface and sub-surface 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.

Effect of geomembrane liner on landfill stability under long-term loading: interfacial shear test and numerical simulation

Clay liners have been widely used in landfill engineering. However, large-scale clay excavation causes secondary environmental damage. This study investigates the feasibility of replacing clay liners with high-density polyethylene (HDPE) geomembranes with different specifications and parameters. Laboratory interface shear tests between municipal solid waste (MSW) samples of different ages and geomembranes were conducted to study the influence of landfill age on interface shear strength. Finite element method was adopted to compare the long-term stability of landfills with HDPE geomembrane versus clay as intermediate liner. The interfacial shear test results show that the cohesion of MSW increases in a short term and then decreases with landfill age. The internal friction angle exhibits an increasing trend with advancing age, however, the rate of its increment declines with age. The rough accuracy of the film surface can increase the interfacial shear strength between MSW. The simulation results show that, unlike clay-lined landfills, the sliding surface of geomembrane-lined landfills is discontinuous at the lining interface, which can delay the penetration of slip surfaces and block the formation of slip zone in the landfill. In addition, the maximum displacement of landfills with geomembrane is 10% lower than that with clay, and the absolute displacement of slope toe decreases with the increase of roughness at the interface of geomembrane. Compared with clay-lined landfills, the overall stability safety factor increased by 18.5-30%. This study provides references for landfill design and on-site stability evaluation, contributing to enhanced long-term stability.

Air quality impacts of landfill fires: A case study from the Brahmapuram Municipal Solid Waste Treatment Plant in Kochi, India

The occurrence of waste fires in unscientifically managed landfill sites has become a pressing environmental issue in the urban centers of developing economies. In the present work, an investigation was carried out to evaluate the air quality implications of three major fire events that occurred at the Brahmapuram Municipal Solid Waste Treatment Plant (BMSWTP) in Kochi, India. Initially, Landsat-based surface temperature monitoring was conducted to identify the thermal hotspots within the landfill. The emissions of different pollutants during waste fires were quantified and compared between satellite-based ex-situ and field-based in-situ methods. The dispersion patterns of PM2.5 particles released during the fires were visualised using the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) particle dispersion model. The Landfill Gas Emissions Model (LandGEM) was employed to quantify the greenhouse gases (GHGs) released during waste storage, which was then compared with the GHGs emissions during waste fires. In-situ emission estimates showed that the combustion of waste at BMSWTP led to the release of 909.3 MT of PM10, 938.8 MT of PM2.5, 5832.9 MT of CO, 43.6 MT of SOx, 284.2 MT of NOx, 138,941.9 MT of CO2, 426.8 MT of CH4, and 2665.1 MT of VOC. However, a noticeable disparity was observed between the in-situ and ex-situ emission estimates, wherein the latter underestimated the actual emissions. Most of the emitted PM2.5 particles propagated oceanward under the influence of prevailing winds, covering the densely populated areas of Kochi municipal corporation. The amount of CH4 and CO2 emitted during the waste fires was on par with the emissions from 159 days of waste storage for CH4 and 51.8 years of waste storage for CO2, with a cumulative global warming potential of 147.9 Gg CO2-e.

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.

Sustainable landfill sites selection using geospatial information and AHP-GDM approach: A case study of Abha-Khamis in Saudi Arabia

Social, environmental, and technical factors must be combined to solve the complex problem of ever-growing municipal solid waste (MSW) and minimize its negative impact on the environment. Saudi Arabia has launched a US$13 billion tourism strategy to transform the Asir region into a year-round tourist destination and has pledged to welcome 10 million local and foreign visitors by 2030. The estimated share of Abha-Khamis will increase to 7.18 million tons of household waste per year. With a gross domestic product (GDP) of USD 820.00 billion by the end of 2022, Saudi Arabia can no longer afford to neglect the issue of waste production and its safe disposal. In this study, to account for all factors and evaluation criteria, a combination of remote sensing, geographic information systems and an analytical hierarchy process (AHP) was used to determine the best locations for municipal solid waste (MSW) disposal in Abha-Khamis. The analysis revealed that 60% of the study area consists of faults (14.28%), drainage networks (12.80%), urban (11.43%), land use (11.41%) and roads (8.35%), while 40% of the suitable area for landfill. Of these, a total of 20 sites ranging in size from 100 to 595 ha are distributed at reasonable distances from the cities of Abha-Khamis, which meet all the critical criteria for suitable landfill sites mentioned in the literature. Current research shows that the use of integrated remote sensing, GIS and the AHP-GDM approach significantly improves the identification of land suitability for MSW management.

Occupational Risk Assessment in Landfills: Research Outcomes from Italy

Industrial production has brought increased wellbeing in the last years, but the amount of solid waste has undoubtedly increased. Thus, open dumpsites and landfills have been created throughout the world, with serious impacts on the environment and public health. In such a context, occupational health and safety (OHS) issues related to workers that have to deal with landfill characterization or management have not been considered sufficiently. To reduce such a research gap, in 2019 a research project started in Italy on OHS risk assessment in landfills. In fact, in such facilities, workers can be subjected to direct contact with the polluted environment and might not be completely aware of the entity and type of pollution (e.g., in open dumpsites). Starting with the analysis of INAIL data on accidents at work which occurred in Italy during the period 2008–2019, a specific risk analysis was carried out with the goal of defining risk determinants and profiles by means of K-means cluster analysis. Such an analysis allowed us to recognize the use of work equipment and the work environment as the main determinants of the accidents on the one hand, and the “driver of the excavator” as the most risky activity on the other. The achieved results take a step forward towards the characterization of occupational health and safety issues in landfills. Accordingly, the research outcomes represent a basis on which to address further research work in this field.

Determination of risk of spontaneous waste ignition and leachate quality for open municipal solid waste dumpsite

The waste receiving capacity of most municipal solid waste (MSW) landfill sites in India is exhausted, resulting in the formation of larger waste heaps. In the majority of Indian cities, these old waste heaps are prone to frequent smoldering and ignition resulting into fires. In this study, the potential risk of spontaneous ignition of landfilled waste at landfill surface was analyzed based on the physico-chemical characteristics of waste, carbon monoxide (CO) levels, landfill surface temperature (LST). The leachate pollution index was also determined to analyze the leachate quality for three different seasons (monsoon, pre-monsoon and post-monsoon). The regression analysis was carried out to understand the thermal properties (smoldering temperature, smoldering time, ignition temperature etc.) of MSW. The results showed that old waste has a higher tendency to undergo ignition compared to fresh waste. It has also been observed that the lower MC of old waste samples in the range of 3.4% and 18.2% is the most likely cause of early smoldering (106.6-109.5 °C) and ignition (198.6-208.4 °C) of old waste. In pre-monsoon season, CO concentrations for sub-surface (10-30 cm depth) smoldering events (SSE) were observed to be between ∼ 150 to 200 ppm. This CO level substantially dropped to 10 ± 1 ppm in the post-monsoon season. The estimation of the leachate pollution index (LPI) showed an index score of 27.35, 30.47 and 10.71 for pre-monsoon, monsoon and post-monsoon seasons, respectively. The determination of CO levels, increased LST and physico-chemical properties of landfilled waste will greatly assist in the abatement of environmental pollution arising from landfill fires.

Safety at waste and recycling industry: Detection and mitigation of waste fire accidents

In this study, NASA's VIIRS (Visible Infrared Imaging Radiometer Suite) fire hotspots and data of the Swedish Civil Contingencies Agency (MSB), collected between 2012 and 2018, was integrated to characterize waste fire incidents that were detected by VIIRS and reported to MSB (DaR), detected by VIIRS but not reported to MSB (DbNR) and that are reported to MSB but not detected by VIIRS (RbND). Results show that the average number of open waste fire incidents per million capita per year (AFIPMC) in Sweden, for the period 2012-2018, ranges from 2.4 to 4.7. Although a weak correlation exists (r = 0.44, P = 0.1563, one tailed) between years and number of fire incidents (MSB + VIIRS fires), a continuous increase in number of fire incidents was recorded between 2014 and 2018. It is concluded that the use of satellite data of fire anomalies, in-combination with the use of incident reports, will help in formalizing more reliable and comprehensive waste fire statistics. Another focus area of the article is to consolidate the recommendations and routines for safe storage of waste and biofuels and to present the lessons that can be learnt from past fire incidents. The article also discusses the technical, political, economic, social, and practical aspects of waste fires and provide a baseline for future research and experimentation.

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

Openmunicipal solid waste(MSW) dumpsites in India are significant hotspots of spontaneous fire and associated air and ground water pollution. Unscientific dumping of MSW poses a major threat to the surrounding environment and human health. One-year-old biodegradable waste components comprised of paper, cardboard, newspaper, textile, wood, grass leaves and coconut shell were analyzed for the determination of the moisture content (MC), smoldering temperature, ignition temperature, and ignition time. Principal component analysis of the old waste components revealed that cardboard, paper, newspaper and leaves are most susceptible waste components for spontaneous ignition. In contrast, MC was the most influential parameter for resulting changes in ignition temperature (⁰C) on ignition time (min). A numerical equation was developed to estimate the time required for the spontaneous waste ignition at MSW dumpsite. The results of the study showed that the aged waste (age ≥ 3 year) having MC below 6 % and initial surface temperature of 78 ⁰C might smolder and ignite during the hottest time of the day in ∼ 6 and ∼ 26 days, respectively. Estimates showed that the time required for spontaneous waste ignition of aged waste is moderately dependent on waste MC (∼5-55 %), surface temperature (∼40-100 ⁰C), monthly pattern of average high temperature (∼36.6-42.6 ⁰C), biodegradable waste components having smoldering temperature ≤ 150 ⁰C and ignition temperature ≤ 270 ⁰C. The present study also showed that the occurrence of landfill fire events at MSW dumpsites is more prominent during the pre-monsoon season i.e. during the elevated temperature level.

Determination of landfill gas generation potential from lignocellulose biomass contents of municipal solid waste

The presence of heat, methane (CH₄) and oxygen in landfill sub-surface causes initiation of spontaneous waste ignition posing severe environmental impacts. A municipal solid waste (MSW) reactor (trough) was designed to monitor landfill gases (LFGs) i.e., CH₄ and CO₂ and its potential from different waste categories (synthetic waste, fresh waste, 3-month, 6-month, 3-year and 5-year-old waste) collected from open MSW dumpsite. The quantity of cellulose (C), hemicellulose (H) and lignin (L) contents (C + H: L) present in organic waste fraction of each waste category was determined. Results showed that fresh waste which has higher ratio of C + H: L is responsible for maximum CH₄ and CO₂ generation i.e., 31,660 and 46,078 ml/g of volatile solid, respectively. The ratio of C + H: L observed in fresh waste, 3-month, 6-month, 3-year and 5-year-old waste was 2.62, 1.70, 1.32, 1.21 and 1, respectively. The study also showed that LFG generation is directly proportional to lignocellulose biomass contents present in MSW. Artificial neural network (ANN) modelling was used for the cross validation of CH₄ yield (valuable product) which showed ±4% error between experimental and predicted data.

Landfill Impacts on the Environment— Review

Waste management (WM) is a demanding undertaking in all countries, with important implications for human health, environmental preservation, sustainability and circular economy. The method of sanitary landfilling for final disposal of waste remains a generally accepted and used method but the available scientific evidence on the waste-related environmental and health effects is not conclusive. Comparative studies of various WM methods (landfilling, incineration, composting etc.) show that among the municipal solid waste (MSW) treatment and disposal technological options, sanitary landfilling or open dumping is popular in most countries because of the relative low cost and low-technical requirement. The European Union (EU) Directive on waste landfills has introduced specific goals for reducing the volume of disposed waste and very strict requirements for landfilling and landfill sites. Evaluation of the impact of landfills on the environment is a crucial topic in the literature and has received increased attention recently, given growing environmental concerns. The main goal of this survey was to conduct a comprehensive assessment of possible impacts of MSW landfills on the environment. The main conclusion of the overall assessment of the literature is that the disposal of MSW in landfills entails a number of environmental risks but with respect to the current situation and rich style of living adopted in industrially developed countries, the idea of WM systems functioning without landfilling—at least in the foreseeable future within one generation—seems to be somewhat unreal. The results also provided important information of landfills as a source of environmental risk. Results of this research may have an important impact on landfill management and the disposal of waste. From the literature review, it is evident that even if high levels of waste avoidance, reuse and recycling are achieved, some waste materials will always need to be forwarded for disposal.