The USA, China and India are the top three producers of municipal solid waste. The composition of solid wastes varies with income: low-to-middle-income population generates mainly organic wastes, ...whereas high-income population produces more waste paper, metals and glasses. Management of municipal solid waste includes recycling, incineration, waste-to-energy conversion, composting or landfilling. Landfilling for solid waste disposal is preferred in many municipalities globally. Landfill sites act as ecological reactors where wastes undergo physical, chemical and biological transformations. Hence, critical factors for sustainable landfilling are landfill liners, the thickness of the soil cover, leachate collection, landfill gas recovery and flaring facilities. Here, we review the impact of landfill conditions such as construction, geometry, weather, temperature, moisture, pH, biodegradable matter and hydrogeological parameters on the generation of landfill gases and leachate. Bioreactor landfills appear as the next-generation sanitary landfills, because they augment solid waste stabilization in a time-efficient manner, as a result of controlled recirculation of leachate and gases. We discuss volume reduction, resource recovery, valorization of dumped wastes, environmental protection and site reclamation toward urban development. We present the classifications and engineered iterations of landfills, operations, mechanisms and mining.
Landfill mining, LFM, is considered to be one of the alternatives to overcome adverse effects of unscientifically created landfills/dumpsites, UCLDs, and engineered landfills, ELFs. However, the ...feasibility of various pathways for the valorization of its yield, designated as the landfill mined residues, LMRs, for sustainable development is still being debated mainly due to not in-place schemes for comprehensive characterization of the landfill-mined-soil-like-fractions, LFMSF, which is a major component of LMRs. Due to this lacuna, proper guidelines, and strategies for utilization of the LFMSF as a manmade resource could also not be developed so far. Another constraint in this context is that the physicochemical characteristics of LFMSF have been attributed to its age, which is difficult to obtain (if not impossible), due to lack of know-how about the method of disposal, turning, and leveling of MSW, and variation in the decomposition pattern between UCLDs and ELFs. With an intention to address these issues, a comprehensive characterization of LFMSF obtained from some of the UCLDs/ELFs in India was conducted by considering their physical, chemical, mineralogical, and thermal characteristics. Based on the experimentally generated data and its statistical analysis, it has been demonstrated that the characteristics of the LFMSF are primarily influenced by its OM. Subsequently, easy to employ relationships between the OM and the characteristics of LFMSF have been developed. It is believed that these relationships will be very much useful for a quick estimation of the LFMSF characteristics that would be very handy for defining its appropriate applications to fulfill sustainable development goals.
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Gasification of excavated landfill waste is one of the promising options to improve the added-value chain during remediation of problematic old landfill sites. Steam gasification is considered as a ...favorable route to convert landfill waste into H2-rich syngas. Co-gasification of such a poor quality landfill waste with biochar or biomass would be beneficial to enhance the H2 concentration in the syngas, as well as to improve the gasification performance. In this work, steam co-gasification of landfill waste with biochar or biomass was carried out in a lab-scale reactor. The effect of the fuel blending ratio was investigated by varying the auxiliary fuel content in the range of 15–35 wt%. Moreover, co-gasification tests were carried out at temperatures between 800 and 1000 °C. The results indicate that adding either biomass or biochar enhances the H2 yield, where the latter accounts for the syngas with the highest H2 concentration. At 800 °C, the addition of 35 wt% biochar can enhance the H2 concentration from 38 to 54 vol%, and lowering the tar yield from 0.050 to 0.014 g/g-fuel-daf. No apparent synergetic effect was observed in the case of biomass co-gasification, which might cause by the high Si content of landfill waste. In contrast, the H2 production increases non-linearly with the biochar share in the fuel, which indicates that a significant synergetic effect occurs during co-gasification due to the reforming of tar over biochar. Increasing the temperature of biochar co-gasification from 800 to 1000 °C elevates the H2 concentration, but decreases the H2/CO ratio and increases the tar yield. Furthermore, the addition of biochar also enhances the gasification efficiency, as indicated by increased values of the energy yield ratio.
•Steam co-gasification of landfill waste with biochar or biomass was carried out.•No clear synergetic effect was observed in the case of biomass co-gasification.•The addition of biochar promotes synergetic effects on the H2 yield production.•Addition of biochar produces higher H2 yield than that of biomass.
The disposal of municipal solid waste (MSW) directly at landfills or open dump areas, without segregation and treatment, is a significant concern due to its hazardous contents of antibiotic-resistant ...bacteria (ARB), antibiotic resistance genes (ARGs), and metal resistance genes (MGEs). The released leachate from landfills greatly effects the soil physicochemical, biological, and groundwater properties associated with agricultural activity and human health. The abundance of ARB, ARGs, and MGEs have been reported worldwide, including MSW landfill sites, animal husbandry, wastewater, groundwater, soil, and aerosol. This review elucidates the occurrence and abundance of ARB, ARGs, and MRGs, which are regarded as emerging contaminants (ECs). Recently, ECs have received global attention because of their prevalence in leachate as a substantial threat to environmental and public health, including an economic burden for developing nations. The present review exclusively discusses the demands to develop a novel eco-friendly management strategy to combat these global issues. This review also gives an intrinsic discussion about the insights of different aspects of environmental and public health concerns caused due to massive leachate generation, the abundance of antibiotics resistance (AR), and the effects of released leachate on the various environmental reservoirs and human health. Furthermore, the current review throws light on the source and fate of different ECs of landfill leachate and their possible impact on the nearby environments (groundwater, surface water, and soil) affecting human health. The present review strongly suggests the demand for future research focuses on the advancement of the removal efficiency of contaminants with the improvement of relevant landfill management to reduce the potential effects of disposable waste. We propose the necessity of the identification and monitoring of potential environmental and human health risks associated with landfill leachate contaminants.
The effect of texturing (co-extrusion using blowing agent) on the longevity of a geomembrane (GMB) when immersed in synthetic municipal solid waste leachate is investigated over a ∼3 year period. ...Based on data at four temperatures (40, 55, 75, and 85 °C), the time to antioxidant depletion of the textured portion of a 1.5 mm core thickness high-density polyethylene (HDPE) GMB is 40% (standard oxidative induction time) and 9% (high-pressure oxidative induction time) faster compared to the 1.5 mm smooth edge of the GMB. However, despite this, stress crack resistance results show that texturing may have no significant effect on the time to nominal failure for this GMB. It is also shown that HDPE GMBs made from nominally the same resin but from different production lots have different rates of stress crack resistance degradation and hence time to nominal failure; this should be considered both in landfill design and landfill construction quality assurance.
California's methane super-emitters Duren, Riley M; Thorpe, Andrew K; Foster, Kelsey T ...
Nature,
11/2019, Letnik:
575, Številka:
7781
Journal Article
Recenzirano
Odprti dostop
Methane is a powerful greenhouse gas and is targeted for emissions mitigation by the US state of California and other jurisdictions worldwide
. Unique opportunities for mitigation are presented by ...point-source emitters-surface features or infrastructure components that are typically less than 10 metres in diameter and emit plumes of highly concentrated methane
. However, data on point-source emissions are sparse and typically lack sufficient spatial and temporal resolution to guide their mitigation and to accurately assess their magnitude
. Here we survey more than 272,000 infrastructure elements in California using an airborne imaging spectrometer that can rapidly map methane plumes
. We conduct five campaigns over several months from 2016 to 2018, spanning the oil and gas, manure-management and waste-management sectors, resulting in the detection, geolocation and quantification of emissions from 564 strong methane point sources. Our remote sensing approach enables the rapid and repeated assessment of large areas at high spatial resolution for a poorly characterized population of methane emitters that often appear intermittently and stochastically. We estimate net methane point-source emissions in California to be 0.618 teragrams per year (95 per cent confidence interval 0.523-0.725), equivalent to 34-46 per cent of the state's methane inventory
for 2016. Methane 'super-emitter' activity occurs in every sector surveyed, with 10 per cent of point sources contributing roughly 60 per cent of point-source emissions-consistent with a study of the US Four Corners region that had a different sectoral mix
. The largest methane emitters in California are a subset of landfills, which exhibit persistent anomalous activity. Methane point-source emissions in California are dominated by landfills (41 per cent), followed by dairies (26 per cent) and the oil and gas sector (26 per cent). Our data have enabled the identification of the 0.2 per cent of California's infrastructure that is responsible for these emissions. Sharing these data with collaborating infrastructure operators has led to the mitigation of anomalous methane-emission activity
.
Landfilling is one of the most common waste management methods employed in all countries alike, irrespective of their developmental status. The most commonly used types of landfills are (a) municipal ...solid waste landfill, (b) industrial waste landfill, and (c) hazardous waste landfill. There is, also, an emerging landfill type called “green waste landfill” that is, occasionally, being used. Most landfills, including those discussed in this review article, are controlled and engineered establishments, wherein the waste ought to abide with certain regulations regarding their quality and quantity. However, illegal and uncontrolled “landfills” (mostly known as open dumpsites) are, unfortunately, prevalent in many developing countries. Due to the widespread use of landfilling, even as of today, it is imperative to examine any environmental- and/or health-related issues that have emerged. The present study seeks to determine the environmental pollution and health effects associated with waste landfilling by adopting a desk review design. It is revealed that landfilling is associated with various environmental pollution problems, namely, (a) underground water pollution due to the leaching of organic, inorganic, and various other substances of concern (SoC) contained in the waste, (b) air pollution due to suspension of particles, (c) odor pollution from the deposition of municipal solid waste (MSW), and (d) even marine pollution from any potential run-offs. Furthermore, health impacts may occur through the pollution of the underground water and the emissions of gases, leading to carcinogenic and non-carcinogenic effects of the exposed population living in their vicinity.
Graphical abstract
•Time, temperature primary factors impacting HTC as-received organic fraction MSW.•As carbonization severity increases, carbon, fixed carbon and HHV increase.•Thermal stability hydrochars decreased ...by presence of amorphous secondary char.•Secondary char HHV higher than primary char HHV.•Organic acids and furfurals in secondary char extracts peak at 220–240 °C.
Hydrothermal carbonization of the organic fraction of municipal solid waste (OFMSW) could mitigate landfill issues while providing a sustainable solid fuel source. This paper demonstrates the impact of processing conditions on the formation and composition of hydrochars and secondary char of OFMSW. Harsher conditions (higher temperatures, longer residence times) decrease generally the solid yield while increasing the higher heating value (HHV), fixed carbon, and elemental carbon. Energy yields upwards of 80% can be obtained at both intermediate and high temperatures (220 and 260–280 °C), but the thermal stability and reactivity of the intermediate hydrochars suggest the formation of a reactive secondary char that condenses on the surface of the primary hydrochar. This secondary char is extractable with organic solvents and is comprised predominantly of organic acids, furfurals and phenols, which peak at 220 and 240 °C and decrease at higher carbonization conditions. The HHVs of secondary char are significantly higher than those of primary char.
A coupled bio-thermal (BT) model is proposed and validated for the prediction of long-term biochemical and thermal behavior of municipal solid waste (MSW) in landfills. The biochemical and thermal ...behavior of the waste was modeled using a two-stage anaerobic degradation model and diffusive heat transport model, respectively. A temperature function that accounts for the inhibitory effect of non-optimum temperatures on the microbial growth was proposed to simulate the coupled effects of biochemical and thermal behavior of waste in landfills. Six numerical simulation cases representing conventional and bioreactor landfill conditions were performed on a typical full-scale landfill cell model to determine the spatial and temporal variation in the long-term biochemical and thermal characteristics of waste in landfills. The results from the numerical analyses show that incorporating the effect of temperature of waste in the modeling of biodegradation of waste in landfills plays a significant role in realistically predicting the long-term biochemical and thermal regime in MSW landfills. The proposed BT model captures the key trends in the landfill gas (LFG) production and waste temperatures typically observed in actual full-scale landfills. Elevated waste temperatures were predicted especially in the bioreactor landfill cases suggesting that rapid decomposition of waste induces high heat generation rates; however, the elevated temperatures were short-lived.
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