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.

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 âˆ¼ 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.

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 âˆ¼ 6 and âˆ¼ 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.

Specific heat and thermal conductivity of municipal solid waste and its effect on landfill fires.

Municipal Solid Waste (MSW) landfills are sources of physical, chemical and microbiological processes and as a result, gases and heat are generated as by-products. The generated heat flows from the higher to lower temperature regions within the landfill. Specific heat and thermal conductivities are two important properties that determine heat flow in MSW landfills. The goal of this study was to determine the thermal conductivity and specific heat capacity of MSW samples of Indian origin and to study its effect on landfill fires. Thermal conductivity and specific heat capacity of waste samples collected from dumpsite at Bhandewadi landfill, Nagpur & Bellahalli landfill, Bangalore (India) and the synthetic MSW (prepared in the lab) were determined using newly designed and fabricated experimental set-up. Results showed that moisture and organic content of MSW are directly proportional to specific heat capacity and indirectly proportional to thermal conductivity. Thermal conductivity of MSW is directly proportional to its density and specific heat is indirectly proportional to the density of MSW. MSW with specific heat and thermal conductivity in the range 0.003 J/g. K - 0.47 J/g. K and 0.35-3.6 J/s. m. K, respectively were found between 30 and 75 °C with 5% to 25% moisture content. As the temperature increases above 75 °C, decrease in thermal conductivity & increase in specific heat was observed and thermal conductivity of 0.07 J/s. m. K was observed at 130-140 °C. As a result of this, heat does not flow and gets concentrated in that region leading to landfill fire.

Estimation of heat generation and consequent temperature rise from nutrients like carbohydrates, proteins and fats in municipal solid waste landfills in India.

The heat generation and temperature rise due to the anaerobic degradation of municipal solid waste (MSW) for selected landfills across India have been estimated in this paper. MSW was quantitatively characterized into carbohydrates, proteins, fats using landfill degradation and transport (LDAT) model equations' and the physical composition of MSW. The heat released due to the breakdown of per kg of carbohydrates, proteins, fats were calculated using chemical equations involved in the anaerobic degradation process. The heat released per tonne of MSW degradation and temperature rise for selected cases was calculated. Moisture content and carbohydrates percentage were crucial parameters in estimating the heat generation as Mavallipura landfilled MSW having 43% carbohydrates and moisture content of 17% released maximum heat of 1116.81 × 103 kJ/t of MSW and Pirana landfill MSW having 12.98% carbohydrates and moisture content of 29.03% released minimum heat of 391.82 × 103 kJ/t of MSW. This generated heat may cause several issues, such as landfill fires, temperature rise in the surrounding areas of landfill, air pollution leading to global warming and other environmental issues. The heat generated from the biodegradation process is a renewable energy resource that can be systematically extracted from the waste mass and used for direct heating purpose in nearby facilities or for augmenting industrial processes having suitable technologies like combined heat and power gas engines, geothermal heat extraction system, etc. This study concludes that the total quantity of heat released depends on the quantity of carbohydrates present in waste and not on total organic content.