Landfill Surface Research Articles

Vertical distribution of antibiotics and antibiotic resistance genes in a representative municipal solid waste landfill, China

The vertical distribution of sulfonamides (SAs), tetracyclines (TCs), macrolides (MLs), and their related antibiotic resistance genes (ARGs) were comprehensively investigated and characterized in a representative municipal solid waste (MSW) landfill in China. The total concentrations of target antibiotics in the MSW landfill were SAs > TCs > MLs. The abundances of mexF (10.78 ± 0.65 log10copies/g) and sul genes (9.15 ± 0.54 log10copies/g) were relatively high, while the tet genes (7.19 ± 0.77 log10copies/g) were the lowest. Both the abundance of antibiotics and genes fluctuated with landfill depth, and the ARGs of the same antibiotics were consistent with depth change. Intl1 and sul genes (sul1, sul2) were tightly connected, and a close relationship also existed between tet genes (tetM, tetQ) and MLs resistance genes (ermB, mefA). High-throughput sequencing showed the dominant genera were Sporosarcina (38%) and Thiobacillus (17%) at sampling points A and C, while the microbial community varied with depth increase at point B were Brevundimonas (20%), Sporosarcina (20%), Pseudomonas (24%), Lysobacter (28%), and Thioalkalimicrobium (14%), respectively. Network analysis further visualized the relationship among antibiotics, genes, and microbial communities and the results indicated the non-random connection among them and the possible host of the target gene. Even at 12.0 m below the landfill surface, the pollution of antibiotics resistance was still serious, which posed difficulties for subsequent landfill remediation and pollution control.

Assessment of the Landfill Barrier System through Numerical Analysis: Rehabilitation and Expansion of Belgrade Landfill Case Study

There are still many unmanaged landfills around the world that pose significant potential environmental problems. One of the largest unmanaged landfills in Europe, which has been used for more than 40 years to deposit waste from Serbia’s capital, Belgrade, is the Vinča landfill. A revitalization and extension of this landfill was proposed that would allow its sustainable operation in the future. The revitalization project considered building a capping layer on the surface of the current landfill, which will close it and which will serve as a liner on the bottom of the new landfill. The use of a composite system including a HDPE geomembrane is considered in the project. New landfill settlements were predicted using the FEM method utilizing a Hardening-soil constitutive model for subgrade. Both immediate settlements of subgrade caused by waste deposition and primary consolidation settlement were calculated. The results show that a substantial increase in the settlement of the geomembrane subgrade can be expected during the primary consolidation period, due to the high rate of filling compared to the permeability of the subgrade. The total settlement of the new landfill in its crown is expected to be between 2.73 and 4.52 m. The axial force in the geomembrane will not exceed the tensile strength of the membrane at any time during or after the new landfill operation.

Biochemical-thermal-hydro-mechanical coupling model for aerobic degradation of landfilled municipal solid waste

Ventilating solid waste landfills with an oxygen supply can effectively accelerate the degradation of waste, achieve rapid stabilization, and realize the sustainable utilization of landfills. Aiming to understand and verify the aerobic degradation process in landfills, this paper proposed a biochemical-thermal-hydro-mechanical coupling model. The model considers aerobic biochemical reactions, dissolved solute migration, heat transport, two-phase flow, and skeleton deformation. The model was verified by comparison with an in-situ experiment at Jinkou landfill. The results showed the model could accurately represent the observed degradation phenomena during the experiment. The modelling results indicated that the rate of temperature increase and peak temperature of the upper layer, which were lower than those of the middle layer, were affected by heat exchange at the landfill surface. The lowest temperatures occurred near the bottom because of high water content and low oxygen concentrations. The high temperature zone migrated out from the injection well during degradation, reflecting the degradation of degradable organic matter associated with oxygen diffusion rates and aerobic degradation reactions. The initial accumulated settlement value was fast, but slowed and finally stabilized. The surface subsidence also developed from the center around the injection well to the surrounding area, and 70% of the total subsidence occurred within 150 days. This newly developed model provides a theoretical framework for analyzing the multi-field coupling of aerobic degradation of landfilled municipal solid waste (MSW).

Mapping of Environmental Pollution Risk Induced by Open Dumping Practice of Municipal Solid Waste in Karadiyana of Sri Lanka Using Geographic Information System

Quantification of environmental pollution risk (EPR) induced by open dumping practice of municipal solid waste (MSW) is important to improve MSW management practices and to provide effective countermeasures for mitigating EPR at the MSW open dumping site. This study targeted an open dumping site at Karadiyana, Western province of Sri Lanka and aimed to assess EPR by using geographical and hydrological information, water (landfill leachate and surface water) and soil quality monitoring for samples collected at the pollutant source (i.e., MSW dumping site) and its surrounding with monthly interval from June to December 2019 to cover both wet and dry periods. The maps of EPR induced by the pollutant source were visualized by analysing measured physicochemical parameters including heavy metals incorporating with interpolation and weighted overlay techniques of geographic information system (GIS). Results showed that the EPR mapharacterized well spatial distribution and seasonal variation of pollutants from the source. Especially, it was found that the pollutants flowed towards the Northwest and North from the pollutant source at the investigated site. It was also found that higher concentrations of phosphorous and heavy metals were observed from landfill leachate samples in dry season than those in wet season. The findings in this study raise the mapping of EPR would contribute to take actions for establishing environmental sound waste disposal and to promote sustainable MSW management practice in Sri Lanka.

ASSESSING LANDFILLS SURFACE TEMPERATURE DISTRIBUTION USING LANDSAT 8 SATELLITE IMAGE AT BIG CITIES IN VIETNAM

In recent years, rapid urbanization and population growth have led to an overload of waste in big cities. High landfill surface temperature is an important factor causing serious environmental pollution due to speeding up the generation of biogas. This paper presents the results of assessment of land surface temperature distribution in some large landfills in Vietnam, including Nam Son landfill (Hanoi) and Da Phuoc landfill (Ho Chi Minh city). Landsat 8 satellite image data is used to calculate land surface temperatures based on the split-window method. The results showed that the landfill surface temperature was much higher than the surrounding area, even compared to the areas characterized by impervious surfaces. The difference between the highest surface temperature in Nam Son, Da Phuoc landfills and the lowest surface temperature in the surrounding area is about 20ºC. The results obtained in this study provide input information to develop monitoring models of pollution at landfills.

Genetic algorithm (GA) - Artificial neural network (ANN) modeling for the emission rates of toxic volatile organic compounds (VOCs) emitted from landfill working surface

Volatile organic compounds (VOCs) emitted from the working surface of landfills have received increasing attention due to the potential risks to human health. Quantifying the emission rates of risky VOCs is important to their health risk assessment but is also challenging because of their high variation and complicated relationship between the emission rates and various influencing factors. In this study, a continuous nine-month sampling of VOCs was conducted on a landfill working surface to identify dominant VOCs that are risky to human health and to construct artificial neural network (ANN) models for their emission rates by involving 105 datasets. Among the 63 detected VOCs, ethanol presented the highest emission rate (885.28 ± 1398.10 μg·m−2·s−1), and the dominant compounds with high emission rates and detection frequencies were characterized in each category. According to the human toxicity impact scores calculated with USEtox method, carbon tetrachloride, ethanol, tetrachloroethylene, 1, 2-dichloroethane, benzene, ethylbenzene, and chloroform were identified as the dominant carcinogenic VOCs, and acrolein, carbon tetrachloride, and 1, 2-dichloropropane were the dominant noncarcinogenic VOCs. ANN models were established for the emission rates of six typical risky VOCs, with meteorological conditions and waste compositions as input parameters and emission rates as output parameters. With the structure optimization and genetic algorithm, all the ANN models achieved good performance and excellent prediction capability with high R2 and low root mean square error (RMSE) values. The emission rates under a 95% probability were predicted for each risky VOCs via the established ANN models, by randomly sampling the input parameters under their data distribution. The approach proposed and results obtained can provide scientific methodology and important information for the monitoring, prediction, and health risk assessment of the VOCs emitted from MSW landfills.

Estimation of dump and landfill waste volumes using unmanned aerial systems

The paper discusses how the choice of software and hardware components used in unmanned aerial systems (UAS) affects the accuracy of estimating volume on landfills and dumpsites, and the amount of ground work needed to create a high-altitude justification of reference geodetic network. A non-specialized low-cost unmanned aerial vehicle (UAV) and a specialized UAV of a geodetic class were compared in scenarios with different numbers of ground control points. In addition, the use of desktop and cloud software for photogrammetric data-processing was assessed.Both specialized geodetic and non-specialized low-cost UAVs made it possible to obtain fairly accurate estimates of waste volume. The differences in the UAV results compared to data obtained by ground surveys were about 1.0%, even with a minimum number of ground control points (GCP). With complete abandonment of GCP and processing aerial data in cloud services, these differences increased to 5.0%.Low-cost UAV and cloud services can be used for operational monitoring of waste volume changes at landfills and dumpsites. A geodesic-class UAV allows researchers to build a more accurate digital terrain model of the landfill surface, but it does not give any advantages in waste volume estimation.

Preliminary Study on Dose Distribution in Depth Direction of Soil in Fukushima Prefecture

Part of the radioactive material released by the Fukushima Daiichi nuclear power plant accident was deposited on the soil in Fukushima Prefecture. Accumulation of radioactive cesium (Cs) into the soil has been confirmed until now. The distribution of radioactive Cs concentration in the depth direction of the soil was preliminarily investigated in order to clarify the present state of radioactive Cs accumulated in the landfill waste as a part of ensuring the safety of the lives of Fukushima Prefecture residents. A hole with a diameter of 10 cm and a depth up to 1 m was dug in the landfill waste of a final disposal site, and the small amount of landfill waste collected at any depth was quantitatively measured with a germanium semiconductor detector. From the present result, the tendency of the distribution of Cs concentration in the depth direction was clarified for the first time. In addition, it was confirmed that since the depth distribution of the radioactive Cs concentration from the landfill surface was complicated, the tendency of that cannot be expressed using the conventional exponential function model.

Leachate from municipal solid waste landfills in a global perspective: Characteristics, influential factors and environmental risks

Landfilling is one of the most common measures for disposing municipal solid waste, while the environmental leakage of landfill leachate, a kind of wastewater with complex compositions and high-level pollutants, has become a crucial eco-environmental issue all over the world. Understanding the profiles of landfill leachate can be useful for promoting sustainable municipal solid waste management, however, there are very few studies at a global level because of data insufficiency. In this work, we established a global database on the physicochemical characteristics of landfill leachate from academic literature, including 1251 pieces of data from 236 provinces or cities in 51 countries. Concentrations of typical pollutants in landfill leachate were aggregated by different categories of countries, climate zones, and landfill ages. Correlations between typical leachate pollutants (chemical oxygen demand, biochemical oxygen demand after five days, ammonia nitrogen, sulfate, chloridion, potassium, cadmium, chromium, ferrum, nickel, and lead) and their influential factors (mean annual temperature, mean annual precipitation, landfill age, and the fraction of food waste) were analysed; and the environmental risks led by landfill leachate were assessed. Results showed that: (1) landfill leachate in developing countries at the dry temperature zone, as well as the moist and wet tropical zone, contained higher concentrations of chemical oxygen demand and biochemical oxygen demand after five days; (2) the percentage of food waste, as an influential factor, has a positive correlation with typical landfill leachate pollutants, with R2 varying from 0.07 to 0.18, indicating its high potential on transforming organic fraction in solid waste into leachate; (3) In regard to the environmental risk resulted from landfill leachate, the groundwater and surface water had greater risks than soil environment nearby the landfill. Besides, chemical oxygen demand, ammonia nitrogen, ferrum, chloridion and heavy metals, especially arsenic, cadmium, nickel, and manganese were dominating pollutants in groundwater and surface water. This work provides valuable data and parameters of global landfill leachate, which could be helpful to mitigate pollution from landfills and achieve the goals of sustainable municipal solid waste management.

Assessment of GHG Interactions in the Vicinity of the Municipal Waste Landfill Site—Case Study

Landfills have been identified as one of the major sources of greenhouse gas (GHG) emissions and as a contributor to climate change. Landfill facilities exhibit considerable spatial and temporal variability of both methane (CH4) and carbon dioxide (CO2) rates. The present work aimed to evaluate the spatial distribution of CH4 and CO2 and their δ13C isotopic composition originating from a municipal landfill site, to identify its contribution to the local GHG budget and the potential impact on the air quality of the immediate surroundings in a short-term response to environmental conditions. The objective was met by performing direct measurements of atmospheric CO2 and CH4 at the selected monitoring points on the surface and applying a binary mixing model for the determination of carbon isotopic ratios in the vicinity of the municipal waste landfill site. Air samples were collected and analysed for isotopic composition using flask sampling with a Picarro G2201-I Cavity Ring-Down Spectroscopy (CRDS) technique. Kriging and Inverse distance weighting (IDW) methods were used to evaluate the values at unsampled locations and to map the excess of GHGs emitted from the landfill surface. The large off-site dispersion of methane from the landfill site at a 500 m distance was identified during field measurements using isotopic data. The mean δ13C of the landfill biogas emitted to the surrounded atmosphere was −53.9 ± 2.2‰, which corresponded well to the microbial degradation processes during acetate fermentation in the waste deposits. The calculated isotopic compositions of CO2 (δ13C = −18.64 ± 1.75‰) indicate the domination of biogenic carbon reduction by vegetation surrounding the landfill. Finally, amounts of methane escaping into the air can be limited by the appropriate landfill management practices (faster covers active quarter through separation layer), and CH4 reduction can be achieved by sealing the cover on the leachate tank.

Vegetation changes as indicators of landfill leachate seepage locations: Case study

Landfills remain widely used for waste disposal, despite their negative impact on human health and environment. Adverse impact is mainly due to gas and leachate emissions. Leachates are liquids that are characterized by high variability in composition, high ammonia and chloride content, and presence of toxic and non-biodegradable compounds. In recent years there has been growing interest in issues related with the reactions of living organisms to pollution - biomonitoring. However, bioindicative methods are not fully used in landfill studies and are still rarely applied. The aim of this work is finding the relationship between the composition and leachate seepage points and determining the possibilities of their practical utilization for the assessment of the applied mineral sealing of landfill surfaces. Additionally, detailed analysis of leachate composition was made. The hypothesis is that some species indicating natural salinity will also indicate landfill sites with the occurrence of leachate seepage, which increase salinity. Physico-chemical analysis of the leachate were carried out. Moreover, vegetation assessment was conducted by phytocoenological relevés. The landfill has different habitats in places where leachate seepage is observed. The results indicate that the presence of leachates alters the plant species composition. The composition shows increasing representation of species tolerant to salinization and a decreasing share of glycophytes in leachate seepage points. Based on the relation of glycophytes to plant species tolerant to salinization, a work procedure and index of leachate vegetation were created, which provide a fast identification of leachate seepage points. The presented results confirm the diagnostic potential of plants for the assessment and location of leachate seepage points. The results may be applied in the reclamation works on landfills.

Monitoring of the State of the Environment in the Zone of Influence of the Landfill of Industrial and Domestic Waste by Bioindication Methods

The results of assessing the state of surface water bodies located in the zone of influence of the closed landfill of industrial and household waste "Shcherbinka" (Domodedovsky district of the Moscow region) are presented. The toxicity of river and waste waters of the landfill was determined by the biological effect on two species of higher plants – oats sowing (Avena sativa) and watercress (Lepidium sativum). As test reactions, the length of the roots of oat seedlings, the germination and length of seedlings of watercress seeds were used. It was found that wastewater from the surface and body of the landfill has a pronounced phytotoxic effect (52–98 %), which manifests itself in the suppression of all the assessed indicators. The high toxicity of river water in the place of discharge of leachate from the waste disposal facility was shown (the phytoeffect value reaches 37 %). As you move away from the source of pollution (when moving downstream of the river), mixing the leachate with river water reduces the concentration of chemicals in the waters to levels that are safe for plants. The values of the estimated indicators obtained during biotesting of river waters at a distance from the landfill are comparable with the control ones. The experiment revealed a similar sensitivity to toxicants of two plants selected as test objects.

Comparison between prediction models and monitored data on leachate generation from a sanitary landfill in the metropolitan region of rio de janeiro, Brazil

Estimating leachate generation during a landfill lifespan is a key issue in reducing its potential risk. Hence, a useful tool is represented by empirical and computational models. In order to ratify the applicability of the Swiss Method, most applied tool in Brazil, and the Hydrologic Evaluation of Landfill Performance (HELP), most utilized in USA, the present article carried out a case study in the São Gonçalo Waste Treatment Center (CTR-SG), located in a humid subtropical climate. Firstly, climate data were collected with Brazil’s National Institute of Meteorology, and landfill structural and operational data were assembled with the company responsible for CTR-SG’ management, Foxx-Haztec, from 2014 to 2018. Subsequently, simulations were conducted on both tools, which indicated that: Swiss Method and HELP do not consider relevant variables for leachate prediction, such as: waste composition and moisture content, organic matter decomposition and dumping methods; thus, these techniques results vary mainly according to annual precipitation, landfill surface area and, for HELP, covering layer thickness. In addition, it was verified that the models forecasted approximately half of the actual volume of generated leachate. In this bias, despite the requirement of few and generally known parameters, these are not reliable tools for assertive prediction. Furthermore, it was found that the Swiss Method employs an imprecise variable, the compaction coefficient, which made pertinent the proposal of a new coefficient, suitable to tropical regions, which should be validated in other landfill scenarios.

Influence of Waste Temperatures on Long-Term Landfill Performance: Coupled Numerical Modeling

A coupled thermo-hydro-bio-mechanical (CTHBM) numerical model to simulate the long-term behavior of municipal solid waste in landfills is presented. Three numerical simulations—a conventional landfill simulation with no leachate injection (CONV) and two bioreactor landfill simulations involving leachate injection—were carried out by applying the CTHBM model to a typical two-dimensional (2D) landfill cell configuration to analyze the effect of temperature on the long-term performance characteristics of a landfill system. Of the two bioreactor landfill simulations, one (BIOR-T) incorporated temperature effects on the waste decomposition, while the other simulation (BIOR-NT) did not. For the waste conditions simulated, the CONV and BIOR-T had a maximum waste temperature of 54°C and 62°C, respectively. The temperatures at the bottom liner were determined to be in the range of 1°C–32°C and 1°C–39°C over the entire simulation time of the CONV case and BIOR-T case, respectively. The effect of waste temperatures on moisture distribution, methane gas production, and landfill surface settlement was also assessed. The surface settlement response for BIOR-T and BIOR-NT simulations suggests that incorporating the effect of waste temperatures on the waste decomposition is important for a realistic prediction of the waste settlement in landfills. The BIOR-T and BIOR-NT simulations had a similar interface shear response, suggesting that the changes in the stiffness and shear strength of waste, due to incorporating temperature effects on the biodegradation rate, have no noticeable impact on the interface shear response in the bottom liner system. Overall, the proposed CTHBM model can be used to predict long-term performance characteristics (e.g., moisture distribution, landfill gas production, settlement of waste, temperatures) relevant for effective design of bioreactor landfills.

Emission and Neutralization of Methane from a Municipal Landfill-Parametric Analysis

An attempt was made to estimate the annual production of CH4 at a municipal waste landfill site in Poland. As a matter of fact, the extent of the unorganized emission of CH4 from the landfill surface was approached based on the adopted mathematical model. The Ward agglomeration method for cluster analysis and the Pearson coefficient were employed to evaluate the distance-based similarity measure and to optimize methods for estimating methane emissions from a landfill as well as to verify the input parameters for the model. In order to calculate the content of biodegradable organic parts in the waste, morphological tests of the landfilled waste were performed. Physical quantities, measurements and the actual amount of the landfilled waste as well as the volume of CH4 neutralized in a collective flare were implemented in the model, respectively. The model-based findings and experimental outcome demonstrated stable gas production in the landfill with a high CH4 content. On the other hand, a rather low efficiency of the landfill passive degassing installation indicated the necessity to design and develop its active counterpart with the prospective application of the generated biogas for energy production in a cogeneration system.

Analytical Modelling of MSW Landfill Surface Displacement Based on GNSS Monitoring.

Displacements of landfills play an important role in the reclamation process and geotechnical safety improvement of such sites. Landfill settlements are defined as a vertical displacement of waste body due to compression, degradable nature of the waste, and creep phenomenon of the waste particles. Waste composition is more diverse than natural soil. Thus, it has to be properly placed and compacted since the landfill body will continuously settle down. Several models of the landfill displacement estimation have already been developed. The aim of the present study was: (i) to review the methods of landfill settlements computation and (ii) to propose the model allowing landfill body displacements simulation based on monitoring datasets applying a Global Navigation Satellite Systems (GNSS) measurement. The new model employs Gauss-Newton iteration and Runge-Kutta methods to estimate landfill surface displacements. The objectives were to analyse and mathematically describe the landfill body displacements. The GNSS geodetic survey and computations allowed concluding that the landfill body has been transformed over the years. The results revealed that the curves of waste displacement are in agreement with the measured total displacement of the landfill, and all curves corresponding to waste displacement are perpendicular to the active edge of the landfill. In the period of a maximum of 4.5 years after the waste deposition with a layer of up to 16.2 m thickness, the phenomenon of expansion was observed, which then disappears, and more settlement occurs due to the gravity of upper layers. The analysed landfill as a whole does not experience significant displacements. Neither of the slope failures are observed, even for large inclination.

Application of Satellite Remote Sensing in Monitoring Elevated Internal Temperatures of Landfills

Subsurface fires and smoldering events at landfills can present serious health hazards and threats to the environment. These fires are much more costly and difficult to extinguish than open fires at the landfill surface. The initiation of a subsurface fire may go unnoticed for a long period of time and undetected fires may spread over a large area. Unfortunately, not all landfill operators keep or publish heat elevation data and many landfills are not equipped with a landfill gas extraction system to control subsurface temperatures generated from the chemical reactions within. The timely and cost-effective identification of subsurface fires is an important and pressing issue. In this work, we describe a method for using satellite thermal infrared imagery at a moderate spatial resolution to identify the locations of subsurface fires and monitor their migration within landfills. The focus of this study was the Bridgeton Sanitary Landfill in Bridgeton, MO, USA where a subsurface fire was first identified in 2010 and continues to burn today. Observations from Landsat satellites over the last seventeen years were examined for surface temperature anomalies (or hot spots) that may be associated with subsurface fires. The results showed that the locations of hot spots identified in satellite imagery match the known locations of the subsurface fires. Changes in the hot-spot locations with time, as determined by in situ measurements, correspond to the spreading routes of the subsurface fires. These results indicate that the proposed approach based on satellite observations can be used as a tool for the identification of landfill subsurface fires by landfill owners/operators to monitor landfills and minimize the expenses associated with extinguishing landfill fires.

INFLUENCE OF MODELLING CHOICES ON THE RESULTS OF LANDFILL ODOUR DISPERSION

Landfills are an important source of odour pollution, potentially causing nuisance to adjacent populations. The most commonly used odour impact assessment for this type of plants usually involves a combination of dynamic olfactometry with dispersion modelling. Despite the advantages associated with the use of dispersion models, there are still some important issues related to their uncertainty. The dispersion model requires the Odour Emission Rate (OER) as input, expressed as units of odour emitted per unit time. Source term characterization and the estimation of the OER are typically the most important steps in the model’s implementation, accounting for the highest contribution to the overall uncertainty. Another important element of uncertainty when modelling emissions from landfill surfaces is the geometrical implementation of the emission source in the dispersion model. This entails the definition of the initial dimensions of the emission, which is critical in the case of large area sources. This paper discusses issues related to uncertainty in the use of dispersion models for the evaluation of landfill odour impacts, particularly focusing on the estimation of the OER and the emission’s initial vertical dimension. This study shows that modelling choices may lead to a variance in the resulting modelled odour concentrations at receptors differing by up to a factor 3. This variability should not cause distrust in the method, but rather indicates the importance of having odour dispersion modelling studies carried out by experts with deep knowledge of the physical-chemical mechanisms underlying atmospheric emissions.

REHABILITATION OF LANDFILLS. NEW FUNCTIONS AND NEW SHAPES FOR THE LANDFILL OF GUIYANG, CHINA

The enlargement of a modern landfill may provide an opportunity to intervene with large-scale projects and thus restore spaces for community use and potentially providing an added value. Based on these premises, the intervention on the Guiyang landfill in China has been developed focussing on the possibility of future reclamation of the site under construction during the design stage by applying an approach that takes into account future use from a technical and, more importantly, economical perspective from the outset. The design proposal has been developed following analysis of these elements: landscape and territory (predominant features of the area, naturalistic features to be preserved, optimization of the interrelationship between the adjacent areas and functionality of the territory); analysis of the residential, infrastructural and productive systems (fundamental in ascertaining the size of the catchment area of potential users). The landfill mining intervention planned in the area allows a more efficient operation of the landfill and has been studied to redesign the site in terms of morphological shapes. Indeed, the project suggests the use of the mass of waste as a plastic element for the reconstruction of a redeveloped landscape according to the shape required by the new configuration of the area. In view of this consideration, in this case study, the typical shape of a landfill is abandoned and the site has been reshaped according to the design of the Chinese landmarks in the surroundings. The area has been conceived as a new green space and defines the role of the landfill site as an Environmental Education Centre and a recreational urban park for public uses, located close to a highly urbanized area. This project design was developed in the context of the ROLES initiative funded by the Italian Ministry of Foreign Affairs in the framework of the Scientific and Technological Cooperation Agreement between the Government of the Republic of Italy and the Government of the People’s Republic of China. ROLES was coordinated by Raffaello Cossu (University of Padova, Italy) with the collaboration of Roberto Raga (University of Padova, Italy) and Dongbei Yue (Tsinghua University, China). ROLES (Remediation of Old Landfills for Environmental sustainability and final Sink) proposes an innovative approach to landfill reclamation, analysing in depth the issue of functional requalification, i.e. the possibility of enhancing the valorisation of landfill surfaces for specific uses aimed at ensuring environmental and landscape sustainability.

Influence of biochar from animal and plant origin on the compressive strength characteristics of degraded landfill surface soils

Growing awareness of sustainability in the landfill cover system has increased the use of biochar amendment for degraded landfill surface soils. Hydraulic and vegetative benefits of biochar on cover soil have been studied in the past, while ignoring mechanical characteristics, which is important to understand progressive failure of landfill infrastructure. In this study, the mechanical characteristics of four soil–biochar composites were investigated by conducting 81 unconfined compressive strength test. The results based on four in-house produced biochar were used to study the effect of compaction state (density, moisture content) and biochar percentage (5% and 10%) on unconfined compressive strength of soil–biochar. The ductility of soil–biochar was investigated for all the four biochars. Results from this study indicate a contrasting observation of strength gain depending on the type of biochar. The unconfined compressive strength of soil–biochar is potentially influenced by the different surface functional groups of biochar (hydrophilicity/hydrophobicity) and soil-biochar interlocking. It was noted that the peanut shell biochar gave comparable unconfined compressive strength of soil–biochar with that of bare soil for different compaction state. However, a diminution in the unconfined compressive strength was observed for all the other three soil–biochar sourced from water hyacinth, saw dust, and poultry litter. The study indicates that the use of biochar in soils does not ensure an improvement in the strength of soil–biochar. Enhancement in ductility was found for all the four soil–biochar irrespective of compaction state. Improvement in ductility was maximum when the soil–biochar is compacted at the dry state of optimum. Plant-based biochar has higher potency to increase the ductility of soil as compared to the animal-based biochar. Our study identifies peanut shell biochar ideal for landfill cover amendment material, considering its mechanical characteristics and design criterion. Soil biochar composite from water hyacinth, saw dust, and poultry litter can be used for potential application in green-infrastructure.