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Bioreactor Landfills: Sustainable Solution to Waste Management
Abstract
With the rapid urbanization in the last few decades, more than two billion tons of solid waste is generated annually. Recently, there has been a paradigm shift in the perception of managing landfills, i.e., from waste disposal to waste treatment for reuse and recovery of resources. Bioreactor landfills are capable of degrading the waste at a much faster rate in comparison to conventional dry tomb type landfills, and therefore, reduces the decomposition process to less than 10 years. This study emphasizes on the utility of end-products generated from bioreactor landfills and their conversion into potential valuable resources. The influence of addition of various moisture supplementation liquids and biosolids on the performance of bioreactor landfills have been reviewed. The landfill gas, which is composed of about 40–60% of methane, can be utilized for the generation of electricity, upgradation of landfill to renewable natural gas and for medium-Btu gas. This paper discusses the governing factors that will improve the landfill gas production. The waste management technologies have been continuously evolving and landfill mining has been realized as an optimum solution for the reduction of landfill footprint and reclamation of valuable materials for revenue generation from waste. The utilization of mined residues has also been reviewed and their applications in the geotechnical field have also been discussed. The goal of the paper is to encourage the environmentalists to develop sustainable solutions and adopt policies based on Waste-to Product concept so that the impact of waste on the environment can be minimized.
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The study focuses on the potential use of municipal solid waste (MSW) fine fractions, that is, fraction below 4.75 mm size for geotechnical applications (backfill/embankment material). In addition, the utilization of these MSW fine fractions in seismic-prone regions demand the dynamic characterization of the material under dynamic loading conditions before its application in the field. Hence, to check the influence of different parameters, that is, relative compaction, effective confining pressure, loading frequency, and strain amplitude on dynamic shear modulus (G) and damping ratio (D) of MSW fines, a set of 44 consolidated undrained cyclic triaxial tests (CTT) were performed. The investigation verifies that some parameters, such as relative compaction, effective confinement, and strain amplitude, have a more significant influence on the dynamic properties of the considered MSW fine fractions than do others, such as loading frequency. The results of this dynamic study can be successfully implemented using the considered MSW fine fractions as soil replacement.
In order to increase the reuse of wastes and residues, as required by the Waste Framework Directive, the potential use of waste, residue and natural minerals as low-cost permeable reactive barrier (PRB) materials was investigated. The performance of a kitchen waste compost, sepiolite and steel slag was compared with that of volcanic slag, pumice and activated carbon in removing specific contaminants from landfill leachate. The experiments represented that the activated carbon removed 27% of the ammonium (NH4+), 75% of the chemical oxygen demand (COD) and 100% of the phosphate (PO43–), zinc (Zn2+) and nickel (Ni2+) from the landfill leachate. Volcanic slag exhibited removal efficiencies of 50% COD and 100% PO43– and pumice exhibited removal efficiencies of 20% NH4+, 27% Zn2+, 65% COD and 100% PO43–. The reactive materials were also checked for their potential in releasing unwanted constituents and represented different levels of the solute (e.g., PO43–, SO42–, NH4+) release. Among the reactives, sepiolite was found to be the reactive material reflecting a minor release (e.g., Zn2+, Cd2+ and Ni2+), but also delivering removal efficiencies of 40, 50, 65, 95, 97, 98, 98 and 100% for Ni2+, COD, Zn2+, SO42–, Cl–, F–, NH4+ and PO43–, respectively. The results show that the studied materials have the potential as reactives for PRB systems treating high strength contaminant plumes.
Landfilling is the most common method for disposing the municipal solid waste, MSW, especially in developing countries. However, the issues pertaining to land acquisition, unhygienic conditions at the landfills and environmental pollution due to intentional/accidental fires are becoming a big nuisance to the town planners and populace. In order to overcome these issues, the bio-reactor landfill, BLF, wherein degradation of the MSW and generation of landfill gases, LFG, can be accelerated, has been found to be a better MSW management strategy. However, in the recent past, BLFs have been criticized for their inefficiency and questions have been raised on their suitability as the 'right approach' to dispose the MSW. This calls for a critical evaluation of the issues pertaining to the effective functioning of BLFs such as (i) MSW decomposition characteristics, (ii) leachate recirculation system (iii) energy generation potential, of the LFG, (iv) estimation of the mining time and sustainable applications of the mined residues and (v) rigorous performance monitoring. A review of existing literature has been conducted and it is believed that such a 'fact finding exercise' would be helpful in creating guidelines related to the design, construction, operation and monitoring of a BLF, particularly in developing countries. Furthermore, based on this exercise the efficacy of BLF could be ameliorated by implementing techniques and/or methods to: (i) amend leachate characteristics for achieving decomposition of the recalcitrant fractions in the MSW, (ii) facilitate non-invasive and economical monitoring of the decomposition of the MSW, (iii) estimate accurately the time required for stabilization of the MSW and (iv) recover the resource from the mined residues. © 2019 Widener University School of Civil Engineering. All rights reserved.
This study is an attempt to assess biogas production improvement from organic fraction of municipal solid waste in simulated bioreactor landfills through recirculation of blended landfill leachate. In this study, various old and new leachate blends (66.6%New/33.3%Old, 33.3%New/66.6%Old, 100%New and 100%Old) were recirculated through 6 laboratory-scale bioreactors using open-loop and closed-loops modes. Compared with the control bioreactor where 100% new leachate was recirculated and operated as a closed-loop, cumulative biogas production was improved by as much as 77.2 to 193.2% when a leachate blend of 33.3%New/66.6%Old was recirculated. Furthermore, comparison of the results from open-loop and closed-loop operated bioreactors indicated that there was approximately 28.3 to 65.4% more biogas in open-loop bioreactors. The Gompertz model produced a better fit (R2 > 0.99) than first-order and logistic function models. Leachate blending reduced the lag phase by almost half and thus helps in alleviating the ensiling during the start-up phase.
Unscientifically Created Landfills and Dumps, UCLDs, pose a severe threat to geoenvironment due to uncontrolled release of greenhouse gases and toxic leachate, accidental fire(s) and occasional slope failure(s). Further, UCLDs also become a socio-economic burden on the municipalities through the consumption of enormous land of the modern-day cities and creation of unhealthy living conditions for the surrounding populace. However, an increase in demand for the land to settle the ever-growing population of such cities and to meet the infrastructural requirements, the habitable boundaries of these cities are expanding, and hence mining of the UCLDs, termed as landfill mining, LFM, is being advocated. Apart from this, LFM facilitates the recovery of resources such as metals, plastics, glass and paper from the landfill mined residues, LMRs. Despite these advantages, LFM faces a significant challenge due to the creation of huge volumes of fine-fractions, separated from the LMRs, also known as ‘Landfill-Mined-Soil-like-Fractions’, LFMSF, which primarily is a conglomeration of organics, soils, debris and smaller chips of metals, plastics, and glass. Unfortunately, utilization of the LFMSF, as a manmade resource, has still not become a well-accepted practice. This is mainly due to the lack of understanding of the characteristics of the LFMSF that are mostly site-specific. With this in view, synthesis of the literature dealing with the issues related to the characterization and utilization of the LFMSF was conducted. It has been realized that by developing and following adequate characterization protocols and guidelines, the LFMSF can be utilized as a manmade resource for sustainable development, without impacting the geoenvironment adversely.
Graphic Abstract
Issues on solid waste management in the most Asian developing countries is not recent. Unfortunately, Malaysia is still practicing landfilling method to dispose the solid wastes. The apparent consequence of this method is the production of highly polluted wastewater called leachate, which can cause several inconveniences and issues. The characterization of landfill leachate is merely important because it can guide towards the possible appropriate treatment. The main focus of this study was to analyse the leachate characteristics at Simpang Renggam Landfill Site, Johor, Malaysia for five consecutive months from January to May of 2018. There were 16 analyzed parameters; namely temperature, pH, total dissolved solids (TDS), conductivity, suspended solids (SS), colour, turbidity, ammonia (NH3-N), dissolved oxygen (DO), chemical oxygen demand (COD), biochemical oxygen demand (BOD5), BOD5/COD ratio, as well as heavy metals (iron (Fe), chromium (Cr), arsenic (As), lead (Pb)). All parameters were analyzed according to the Standard Methods for the Examination of Water and Wastewater, and have followed the procedures of respective instruments. Leachate in SRLS could be classified as stabilized ones, by considering the characteristics and the age of landfill. SRLS is recommended to upgrade its management system for better waste disposal and leachate treatment.
In many developing countries, there has been growing interest in bioreactor landfills for municipal solid waste (MSW) management. This research study has been conducted for comparing leachate characterization and waste stabilization in simulated pilot-scale anaerobic bioreactor landfills. Four pilot-scale reactors were constructed and operated for 540 d. This study aimed to show whether a pilot-scale bioreactor containing sewage sludge mixed with MSW, with a geotextile filter in its drainage layer, and with recirculating leachate, could improve leachate quality and waste stabilization in a landfill. Bioreactor R1 comprised MSW and sewage sludge, while bioreactor R2 was the same as R1 but with a geotextile-1 (GT-1) filter fitted. R3 contained no sludge but only MSW and GT-1 fitted, while R4 contained no sludge but only MSW and two layers of geotextile filter (GT-2 and GT-3). All reactors were operated with leachate recirculation, simulating bioreactor landfills. The results showed that the chemical oxygen demand (COD) half-lives of leachate from the reactors were approximately 8, 7, 9, and 10 months for R1, R2, R3, and R4, respectively. By the end of the study, the waste in R2 and R4 was more stable, with 66% and 65% reductions in volatile solids, respectively. Reactor R2, which contained MSW, sewage sludge, and one-layer geotextile (GT-1), provided higher stabilization of MSW and shorter COD half life than the other reactors.
Soil-like material (SLM) constitutes the largest component of reclaimed material from old municipal solid waste (MSW) dumps, often exceeding 50% of the excavated material. One attractive option for use of this material is bulk applications in earthfills instead of natural soil. This paper presents the leaching characteristics of soil-like fraction (finer than 4.75 mm) of aged municipal solid waste excavated from three old dumps of India. The leaching behavior of this soil-like fraction was assessed to examine its use as an earthfill. The total dissolved solids (TDS), chemical oxygen demand (COD), release of color, and ammoniacal nitrogen in the leachate from soil-like material were found significantly higher in comparison with the water extract of local soil. Relatively elevated concentration of some metals (arsenic, chromium, copper, cobalt, and nickel) were observed in the leachate from soil-like material in comparison to the water extract of local soils. The study indicates that the soil-like fractions obtained from landfill mining have to be screened for physicochemical characteristics and pollution potential before using them as an earthfill.
India has drawn the world's attention due to the high-paced growth of industrialization, urbanization, and population. However, another aspect of higher economic development has resulted in increased waste generation and consumption of natural resources, and hence ecological degradation and pollution. As awareness increases of the detrimental effects of currently used waste disposal methods on the environment, accountability is needed for an effective waste management system. This paper presents the existing situation of municipal solid waste (MSW) generation, composition, management, and problems associated with it in Indian cities. Statistically, urban India produced around 62 Mt of solid waste (450 g/capita/day) in 2015. Approximately 82% of MSW was collected and the remaining 18% was litter. The waste treated was only 28% of the collected waste, and the remaining 72% was openly dumped. Waste collection efficiency ranges between 70% and 95% in major metropolitan cities, whereas in several smaller cities it is below 50%. Most urban local bodies (ULBs) are unable to manage such a large amount of solid waste due to financial debilities and inadequate infrastructure. Source segregation of waste, doorstep collection, options for recycling and reuse, technologies for treatment, land availability, and disposal competence are a few of the prime challenges. Addressing these challenges, this paper discusses the current government's policies, financial supports, and incentives for solid waste management (SWM), as well as gaps and suggestions of current SWM rules. This paper also addresses a comparative view of MSW management in different countries and adoption of waste processing technologies for a particular place in India. This study can assist decision makers, planners, municipal authorities and researchers to create a more efficient plan for the current status of, challenges of, and barriers to SWM in India.
The following case study belongs to the New-Mine project and the objective of the project is to develop a new “Enhanced Landfill Mining” (ELFM) scenario for a combined resource-recovery and remediation strategy. This strategy could reduce future remediation costs and reclaim valuable land while simultaneously unlocking valuable resources. In the past, insufficiently reliable data about the composition of landfills, overestimation of the quality of excavated material and poor product marketing of the possible recyclables have resulted in a bad reputation for landfill-mining projects. The ongoing research in the NEW-MINE project shall show that there are possibilities to create valuable outputs from landfills with enhanced treatment processes, such as a better distribution of the different mechanical processes. To create mechanical routes to recover valuable materials from old landfills, it is important to characterize the material, creating a basis for the research. The objective of this case study, executed from November 2016 until June 2017 at the landfill site in Halbenrain (Austria), is to study the efficiency of different sorting technologies with old landfill material. The excavated material was transported and used as feedstock in a configured state-of-the-art mechanical-biological treatment (MBT) plant located next to the landfill. During the mechanical processing, metals and high-calorific fractions were sorted out from the input flow. As a result of the mechanical processing, approx. 3% of the ferrous metals were recovered, approx. 20% of potential RDF (pRDF) was separated and could have been energetically recovered, and approx. 74% belonged to the finer fraction (< 40 mm). Each sample from the sampling campaign was sieved to obtain the particle size distribution. Via manual sorting, the material was classified into plastics, wood, paper, textile, inerts, Fe metal, NF metals, glass/ceramic and residuals. In addition, the moisture (wt%), the ash content (wt%), the calorific value (MJ/kg) and the concentration of heavy metals (%) of the finer fraction (<40 mm) were analysed. The aim of this study is to assess the possibilities of different mechanical processes with landfill mining (LFM) material and to gain information about the characterization of five material flows derived from the mechanical treatment, together with the mass balance of the MBT. Although every landfill has its own characteristics, the results obtained from this case study can help to understand the general potential, contribute to develop methodologies for characterization of old landfill material and identify problematic fields that require further research.
Reclamation of the dumps/landfills having huge quantities of decades-old garbage (aged waste or legacy waste) in an environmentally sound manner is one of the major challenges faced by the developing nations in general and in particular by urban local bodies in India. The article presents the feasibility of landfill mining operation specifically to recover soil-like material at old dumpsites of India for re-use in geotechnical applications. Aged municipal solid waste was collected from three dumpsites of India and initial tests were conducted on the soil-like material of the municipal solid waste. Initial tests results of grain size distribution, compositional analysis, organic content, total dissolved solids, elemental analysis, heavy metal analysis and colour of the leached water from finer fraction of aged municipal solid waste are presented. From the preliminary investigation, it was found that organic content in 15–20-year-old dumpsites varies between 5%–12%. The total dissolved solids ranges between 1.2%–1.5%. The dark coloured water leaching out from aged waste, with reference to local soil, is one of the objectionable parameters and depends on the organic content. The concentration of heavy metals of the finer fraction were compared with the standards. It was found that copper, chromium and cadmium are present at elevated levels in all the three dumpsites. The study concluded that the bulk of the soil-like material from aged municipal solid waste landfills can be used as cover material for landfills at the same site. However, some treatment in terms of washing, thermal treatment, blending with local soil, biological treatment, etc., is required before it can be re-used in other geotechnical applications.
The European Union, with 60% of the total global production of biogas, is the world leader. In 2012, the percentage of electrical energy produced by biogas was 6% of the EU-28 electricity generated through renewable sources while, in 2013, the almost 830 biogas units produced 7448 GWh which corresponds to 14% of EU-28 gross electricity production. Germany, U.K. and Italy are the main EU biogas producers with over 78% of the 2013 primary energy production. Electricity production is the main biogas energy recovery form because the engine cooling water is used to maintain the digester required temperature while energy crops and manure are the most used organic matters. Spark-ignition engines with a rated power of 1MWel in which the filtered biogas is burned to produce work is the widely-adopted technology. With the aim of analyzing the emissions of a real biogas engine, in the present work, the authors firstly present an overview of the Italian biogas sector and the most used conversion technologies. Then, the standards which regulate the biogas plant emissions and the emissions data acquired during a one-year monitoring activity on 10 biogas plants are presented and discussed with the aim of assessing the biogas units’ real emissions.
A review of available literature of landfill mining and potential challenges, opportunities and work scope.
Landfill mining is an alternative technology that merges the ideas of material recycling and sustainable waste management. This paper reports a case study to estimate the value of landfilled materials and their respective market opportunities, based on a full-scale landfill mining project in Estonia. During the project, a dump site (Kudjape, Estonia) was excavated with the main objectives of extracting soil-like final cover material with the function of methane degradation. In total, about 57,777 m³ of waste was processed, particularly the uppermost 10-year layer of waste. Manual sorting was performed in four test pits to determine the detailed composition of wastes. 11,610 kg of waste was screened on site, resulting in fine (<40 mm) and coarse (>40 mm) fractions with the share of 54% and 46%, respectively. Some portion of the fine fraction was sieved further to obtain a very fine grained fraction of <10 mm and analyzed for its potential for metals recovery. The average chemical composition of the <10 mm soil-like fraction suggests that it offers opportunities for metal (Cr, Cu, Ni, Pb, and Zn) extraction and recovery. The findings from this study highlight the importance of implementing best available site-specific technologies for on-site separation up to 10 mm grain size, and the importance of developing and implementing innovative extraction methods for materials recovery from soil-like fractions.
The global warming is directly related to the increased greenhouse gas emissions from both natural and anthropogenic origins. There has been a drastic rise in the concentration of CO2 and other greenhouse gases since the industrial revolution primarily due to the intensifying consumption of fossil fuels. With the need to reduce carbon emissions and mitigate global warming certain strategies relating to carbon capturing and sequestration are indispensable. This paper comprehensively describes several physicochemical, biological and geological routes for carbon capture and sequestration. The trend of the increase in greenhouse gases over the years is illustrated along with the global statistics for fossil fuels usage and biofuels production. The physicochemical carbon capturing technologies discussed include absorption, adsorption, membrane separation and cryogenic distillation. The algal and bacterial systems, dedicated energy crops and coalbed methanogenesis have been vividly explained as the biological routes for carbon sequestration. The geological carbon sequestering route centers on biochar application and oceanic carbon storage. A systematic survey has been made on the origin and impact of greenhouse gases along with the potential for sequestration based on some fast-track and long-term sequestration technologies.
Sixty-year-old municipal solid waste (MSW) at a partially closed landfill in southern California, USA, was excavated, processed, blended with soil, and placed as engineered fill to accommodate post-closure development. Processing involved waste screening followed by removal of objectionable materials (e.g., tires, large wooden planks) and shredding of large particles retained on the screen. Processed material was delivered to the fill site and blended with on-site soils. Prior to these field activities, an assessment of the material properties of the waste and its long-term settlement potential were conducted. This paper presents the results of detailed characterization of representative bulk samples of waste recovered from the area to be excavated and laboratory testing of these samples. The laboratory testing program included organic content measurement, grain size analysis, Atterberg limits testing, modified Proctor compaction testing, one-dimensional compression testing and analysis of the cellulose, hemicellulose, and lignin content. The results of the laboratory testing program were used to estimate the long-term settlement potential of the blended waste placed as engineered fill. 1. BACKGROUND To accommodate a proposed freeway access ramp for post-closure development at an old landfill, it was deemed necessary to completely excavate and remove waste from beneath the ramp due to waste settlement concerns. For various reasons, transporting the excavated waste to an active landfill was not possible. It was, therefore, necessary to consolidate the excavated waste on-site, beneath the engineered cap in the post-closure development area. The preferred area for waste reconsolidation was determined to be the parking lot portion of the redevelopment area. This area was considered to be more settlement tolerant than the balance of the site. Furthermore, sufficient air space was available in this area to accommodate the waste excavated from the highway area. Therefore, it
The present study was aimed at finding out the anaerobic digestion potential of organic fraction of municipal solid waste of Varanasi, India. Anaerobic digestion was preferred as the organic fraction has a high moisture content of about 85% on an average basis and a high C/N ratio in the range of 25-30. Sodium hydroxide was added to the substrate in the hydrolysis phase and cow dung slurry was used as inoculums in the methanogenesis step. The pH, COD and VFA were the vital parameters monitored in the hydrolysis stage, while biogas production rate was the parameter observed during methanogenesis step. The pH value decreased due to the formation of VFA during hydrolysis. Due to alkaline hydrolysis pre-treatment of waste, methane production was rapid in the methanogenesis step. The total biogas yield was found to be in the range of 0.35-0.40 N m3/kg volatile solids with a methane content of 60-65%.
Noticeable changes in the availability of mineral raw materials (e.g. ores, coal) were observed during the last years due to the enormous raw material demand of developing countries (e.g. China). These led to an evident scarcity of raw materials, highly competitive markets and to a significantly aggravated accessibility to mineral resources. Landfill Mining represents one possibility for exploitation of secondary raw materials, as landfill sites can contain significant amounts of potentially recyclable and recoverable energy materials (REM). In this regard, to evaluate the secondary raw material potential (resource potential) of Austrian landfills, two sanitary landfill sites were chosen for closer investigation. The scope of this investigation constituted waste characterization by realization of sorting analyses of excavated waste and a large scale mechanical treatment experiment. The results obtained by the hand sorting show that approximately 32 - 52 w% of the total deposited amount consists of REM theoretically. However, due to a high water content of the materials (~ 42 %) and a high proportion of fines (68 w%), a proper mechanical separation of these materials is hindered as shown by the large-scale experiment. Consequently, no plastic fraction and about 1 w% metals were recovered compared to 18 w% plastics and 5 w% metals found during hand sorting. To increase the output of REM from mechanical treatment processes, further investigation has to be established in the future.
Landfill mining is an environmentally-friendly technology that combines the concepts of material recycling and sustainable waste management, and it has received a great deal of worldwide attention because of its significant environmental and economic potential in material recycling, energy recovery, land reclamation and pollution prevention. This work applied a cost-benefit analysis model for assessing the economic feasibility, which is important for promoting landfill mining. The model includes eight indicators of costs and nine indicators of benefits. Four landfill mining scenarios were designed and analyzed based on field data. The economic feasibility of landfill mining was then evaluated by the indicator of net present value (NPV). According to our case study of a typical old landfill mining project in China (Yingchun landfill), rental of excavation and hauling equipment, waste processing and material transportation were the top three costs of landfill mining, accounting for 88.2% of the total cost, and the average cost per unit of stored waste was 12.7USDton(-1). The top three benefits of landfill mining were electricity generation by incineration, land reclamation and recycling soil-like materials. The NPV analysis of the four different scenarios indicated that the Yingchun landfill mining project could obtain a net positive benefit varying from 1.92 million USD to 16.63 million USD. However, the NPV was sensitive to the mode of land reuse, the availability of energy recovery facilities and the possibility of obtaining financial support by avoiding post-closure care.
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A bioreactor landfill was constructed by the city of Calgary, Canada to sustainably manage solid waste. It includes initial operation of bioreactor landfill under anaerobic conditions to recover biogas, then under aerobic condition to convert waste into compost and finally mining compost for reuse. The bioreactor landfill is equipped with leachate recirculation systems to accelerate the decomposition of organic waste. Rapid decomposition leads to large quantities of landfill gas, which in turn results in rapid settlement. The landfill gas produced is collected and used for energy recovery. The methane present in landfill gas is a potent greenhouse gas and the use of landfill gas in energy recovery reduces the environmental impact of this gas. The gas extraction and leachate recirculation systems are quite expensive. Hence the bioreactor landfill requires efficient operation to maximize gas generation while having excessive settlement. This manuscript presents details of a full scale landfill bioreactor performance during the anaerobic phase of the sustainable landfill, including leachate generation and recirculation, and gas generation and monitoring of performance date including temperature and settlement.
Although bioreactor landfills have many advantages associated with them, challenges remain, including the persistence of ammonia-nitrogen in the leachate. It has been suggested that ammonia-nitrogen is one of the most significant long-term pollution problem in landfills and is likely a parameter that will determine when landfill postclosure monitoring may end. The fate of nitrogen in bioreactor landfills is not well understood. As more landfills transition operation to bioreactors, more attention must be paid to how operating the landfill as a bioreactor may affect the fate of nitrogen. Processes such as sorption, volatilization, nitrification, denitrification, anaerobic ammonium oxidation, and dissimilatory nitrate reduction may all occur.
Settlement evaluation in sanitary landfills is a complex process, due to the waste heterogeneity, time-varying properties and influencing factors and mechanisms, such as mechanical compression due to load application and creep, and physical-chemical and biological processes caused by the wastes decomposition. Many empirical models for the analysis of long-term settlement in landfills are reported in the literature. This paper presents the results of a settlement monitoring program carried out during 6years in Belo Horizonte experimental landfill. Different sets of field data were used to calibrate three long-term settlement prediction models (rheological, hyperbolic and composite). The parameters obtained in the calibration were used to predict the settlements and to compare with actual field data. During the monitoring period of 6years, significant vertical strains were observed (of up to 31%) in relation to the initial height of the experimental landfill. The results for the long-term settlement prediction obtained by the hyperbolic and rheological models significantly underestimate the settlements, regardless the period of data used in the calibration. The best fits were obtained with the composite model, except when 1year field data were used in the calibration. The results of the composite model indicate settlements stabilization at larger times and with larger final settlements when compared to the hyperbolic and rheological models.
1] Significant interannual variations in the growth rate of atmospheric CH 4 justify the development of an improved methodology for landfill emissions, the largest anthropogenic source in many developed countries. A major problem is that reliable solid waste data often do not exist, especially for developing countries where emissions are increasing. Here we develop and apply a new proxy method to reconstruct historical estimates for annual CH 4 emissions for the period 1980–1996. Using composited solid waste data from 1975–1995, we developed linear regressions for waste generation per capita based on energy consumption per capita, a surrogate which reflects population and affluence, the major determinants of solid waste generation rates. Using total population (developed countries) or urban population (developing countries), annual landfill CH 4 emissions were estimated using a modified Intergovernmental Panel on Climate Change (IPCC) methodology. Methane recovery was modeled by fitting historic data to time-dependent linear relationships. Two scenarios for global emissions using the surrogate were compared to two scenarios using an IPCC standard methodology. Results from all four scenarios range from 16 to 57 Tg CH 4 yr À1 , a similar range as previous estimates. We support the use of the lower energy surrogate scenario (A) with annual emissions of 16–20 Tg CH 4 yr À1 , both positive and negative annual variations, and commercial recovery >15% by 1996. The surrogate provides a reasonable methodology for a large number of countries where data do not exist, a consistent methodology for both developed and developing countries, and a procedure which facilitates annual updates using readily available data.
Among different conversion processes for biomass, biological anaerobic digestion is one of the most economic ways to produce
biogas from various biomass substrates. In addition to hydrolysis of polymeric substances, the activity and performance of
the methanogenic bacteria is of paramount importance during methanogenesis. The aim of this paper is primarily to review the
recent literature about the occurrence of both acetotrophic and hydrogenotrophic methanogens during anaerobic conversion of
particulate biomass to methane (not wastewater treatment), while this review does not cover the activity of the acetate oxidizing
bacteria. Both acetotrophic and hydrogenotrophic methanogens are essential for the last step of methanogenesis, but the reports
about their roles during this phase of the process are very limited. Despite, some conclusions can still be drawn. At low
concentrations of acetate, normally filamentous Methanosaeta species dominate, e.g., often observed in sewage sludge. Apparently,
high concentrations of toxic ionic agents, like ammonia, hydrogen sulfide (H2S) and volatile fatty acids (VFA), inhibit preferably Methanosaetaceae and especially allow the growth of Methanosarcina species
consisting of irregular cell clumps, e.g., in cattle manure. Thermophilic conditions can favour rod like or coccoid hydrogenotrophic
methanogens. Thermophilic Methanosarcina species were also observed, but not thermophilic Methanosaetae. Other environmental
factors could favour hydrogentrophic bacteria, e.g., short or low retention times in a biomass reactor. However, no general
rules regarding process parameters could be derivated at the moment, which favours hydrogenotrophic methanogens. Presumably,
it depends only on the hydrogen concentration, which is generally not mentioned in the literature.
The geotechnical properties of solid waste soils for use as sub-base materials in road construction were investigated. A series of field tests and laboratory tests were performed to assess the physical and mechanical properties of the solid waste soils sampled from a landfill site, near to a riverside, which had been reclaimed over the last two decades. The tests showed that geotechnical properties are clearly affected by the magnitude of organic matter content. As the organic matter content increases, the maximum dry unit weight, the shear strength and bearing capacity of ground decrease, while the void ratio and compressibility increase. If the organic matter content is more than about 8% in solid waste soils, it is not suitable for use as a sub-base material in road construction due to the significant decrease of shear strength and bearing capacity.
Refuse-derived fuel (RDF) is generated by selected Municipal Solid Waste (MSW) fractions. Due to MSW composition changes by location, it is challenging to sell RDF as a product in the market. This article compiles the significant standards and rules governing RDF manufacture and usage. Additionally, it emphasizes the key actors that have already made a business of its commercialization and energy production through thermochemical processes. Combustion is the most often utilized thermochemical process, and this paper gathers information from several works on the combustion of RDF and RDF blends. Pyrolysis and gasification are also discussed, along with the primary benefits and drawbacks of RDF usage. Finally, the market's potential and significant constraints are examined. The primary constraint is the RDF price due to commercialization fees. However, RDF is aligned with the circular economy, sustainable development goals, and CO2 reductions by avoiding the extraction of new fossil fuels.
Over the last few decades, landfill design and operational practices have evolved. Current landfill waste cells include innovative features that eliminate most of the negative environmental impacts associated with waste disposal on land. This review focuses on some of the historical and recent advances in waste cell design and operational practices that minimize greenhouse gas (GHG) emissions associated with landfills that accept biodegradable organic waste and maximize energy and resource recovery from waste cells. Here, we emphasize innovative practices such as the operation of a waste cell as a landfill bioreactor with leachate recirculation to maximize landfill gas production and increase the rate of waste stabilization, controlling GHG emissions during filling of the waste cell, and mining of waste cells to recover recyclables and reuse waste residue for energy recovery and other beneficial uses.
The rapid world population growth and economic development have been increasing the pressure on natural resources, especially nutrients. Efforts are being made to recycle the key elements of resources that are normally wasted. In this context, ammonia recovery is of special economic interest, since it is one of the main nutrients in the fertilizer market. Landfill leachate (LFL) stands out as an ammonia-rich effluent widely produced worldwide. Thus, the aim of this study was to assess the performance of a solar-driven modified direct contact membrane distillation (M-DCMD) in the recovery of ammonia from LFL. Operational conditions (LFL pH and temperature (T), and concentration of the absorbing H2SO4 solution) were optimized and the maximum critical point (pH 10.8, T = 43°C, and H2SO4 concentration 0.18 mol L⁻¹) allowed for 98% removal and 59% recovery of ammonia. 1.5 kg of ammonia could be recovery from each 1 m³ of treated effluent, a monthly production of 21 tons of ammonia or 93.5 tons of ammonia sulphate. The obtained ammonium sulphate solution can be used as fertilizer. The membrane distillation system using solar heating demonstrated better economic performance since there is an economy with energy due to solar thermal energy being converted into electrical energy. This fact reduces the unit OPEX value and, consequently decrease the leachate total treatment cost, which was estimated at US$7.52/m³ of leachate treated.
For achieving sustainability in management of municipal solid waste (MSW), it is important to ensure that residues, remaining after processing of waste in various plants (composting, waste to energy (WTE), landfilling), are reutilised in a safe and useful manner. Such residues constitute more than 25–35% of the total MSW generated in urban areas. This paper examines the feasibility of using soil-sized residues from landfill mining operations as well as from WTE plants in large quantities (bulk) in geotechnical applications relating to earthworks and structural fills. The geotechnical properties of the residues as well as the contaminants of concern in these residues from two waste dumps and three waste-to-energy plants of Delhi have been evaluated and the critical parameters inhibiting their un-restricted bulk reuse have been identified. The role of high soluble solids, high organic content, elevated heavy metals, release of colour and variable pH has been brought out. The design measures and treatment methods that need to be adopted when using these residues in surface fills, shallow fills, deep fills and structural fills have been highlighted.
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.
Recycling of minerals from waste deposits could potentially double the recycling flows while offering an opportunity to address the many problematic landfills. However, this type of activity, i.e., landfill mining, brings many advantages, risks and uncertainties and lacks economic feasibility. Therefore, we investigate the capacity of the Swedish authorities to navigate the environmental, resource, and economic conditions of landfill mining and their attitude to support such radical recycling alternatives towards a resource transition.
By analyzing three governmental commissions on landfill mining, we show how the authorities seem unable to embrace the complexity of the concept. When landfill mining is framed as a remediation activity the authorities are positive in support, but when it is framed as a mining activity the authorities are negative. Landfill mining is evaluated based on how conventional practices work, with one and only one purpose: to extract resources or remediation. That traditional mining was a starting point in the evaluation becomes particularly obvious when the resource potential shall be evaluated. The resource potential of landfills is assessed based on metals with a high occurrence in the bedrock. If the potential instead had been based on metals with low incidence in the Swedish bedrock, the potential would have been found in the human built environment.
Secondary resources in landfills seem to lack an institutional affiliation, since the institutional arrangements that are responsible for landfills primarily perceive them as pollution, while the institutions responsible for resources, on the other hand, assume them to be found in the bedrock. Finally, we suggest how the institutional capacity for a resource transition can increase by the introduction of a broader approach when evaluating emerging alternatives and a new institutional order.
This study assesses the recycling potential of municipal solid waste from a closed irregular landfill in Beijing. The assessment comprises an analysis protocol, including waste composition, chemical characteristics, and environmental bioassays. The waste samples were screened at 10 mm and 5 mm, which proved to be effective in reducing the heavy metal content. Chemical analyses of the waste soil showed that the concentrations of nutrients were much higher than the relevant standard. The possible phytotoxicity of the waste soil was explored by conducting germination tests on rice seeds (Oryza sativa L.). The results indicated that the waste soil could have adverse effects on the growth of the plants. The newly developed pot experiment with Poa pratensis Linn. showed that a significant improvement in the compatibility of waste soil with plants was induced by the application of coal cinders. Assessment by the toxicity characteristic leaching procedure showed that heavy metal concentrations in the mixed substrates were all below the allowable US standard. In conclusion, the experimental activities conducted demonstrate that recycling waste soil (size < 5 mm) is potentially safe and suitable for remediation activities.
Leachate production from shredded municipal soil wastes and its stabilization and associated gas production monitored over a 699-day test period have indicated that once leachate is generated and recycled, rapid conversion of readily available organic constituents occurs. The landfill thereby serves as an anaerobic biochemical stabilization process which promotes sequential conversion of complex materials through intermediates to final end products. The overall results indicate that leachate recycle will enhance predictability and accelerate stabilization of readily available organic constituents with increased rates of gas production. Decreasing the time required for stabilization to a matter of months rather than years provides attractive alternatives for better operational control, energy recovery and rapid realization of potentials for land reclamation and ultimate use without some of the uncertainties associated with conventional landfill management practices.
Landfills stock massive amounts of minerals and materials, where soil-like material is the primary component of stored waste in old landfills. A typical old landfill (Yingchun landfill) in China was taken as a study case. The stored wastes were sampled from different depths of the landfill, and then the soil-like materials were screened for further analysis. Physicochemical characteristics and the fertilizer quality of the soil-like materials were analyzed and the fertilizer effects were studied by cultivating Impatiens balsamina L. with different mixed ratios of soil-like materials and natural soils. According to the results, soil-like materials accounted for 75.02% of the total stored wastes and were in an advanced state of decomposition. Soil-like materials displayed a cation exchange capacity of 84.53 cmol(+) kg−1, pH 8.14, and an electrical conductivity of 1190.55 μS cm−1, and were also characterized by high levels of organic carbon and nutrient contents compared to natural soils. The total organic carbon, total nitrogen, total phosphorus, and total potassium of soil-like materials were 9.06, 0.16, 0.21, and 1.48%, respectively. Most of the heavy metal content was relatively lower than the law limits in China. However, As and Zn may have an environmental contamination risk. It could be shown that soil-like materials could significantly promote growing and flowering of I. balsamina L., and were proved to be a valuable bio-resource with utility as soil amendment, cultivating substrate, and raw materials for producing organic-inorganic compound fertilizers.
The present study addresses the theme of recycling potential of old open dumpsites by using landfill mining. Attention is focused on the possible reuse of the residual finer fraction (<4 mm), which constitutes more than 60% of the total mined material, sampled in the old open dumpsite of Lavello (Southern Italy). We propose a protocol of analysis of the landfill material that links chemical analyses and environmental bioassays. This protocol is used to evaluate the compatibility of the residual matrix for the disposal in temporary storages and the formation of “bio-soils” to be used in geo-environmental applications, such as the construction of barrier layers of landfills, or in environmental remediation activities. Attention is mainly focused on the presence of heavy metals and on the possible interaction with test organisms. Chemical analyses of the residual matrix and leaching tests showed that the concentration of heavy metals is always below the legislation limits. Biological acute tests (with Lepidum sativum, Vicia faba and Lactuca sativa) do not emphasize adverse effects to the growth of the plant species, except the bioassay with V. faba, which showed a dose–response effect. The new developed chronic bioassay test with Spartium junceum showed a good adaptation to stress conditions induced by the presence of the mined landfill material. In conclusion, the conducted experimental activities demonstrated the suitability of the material to be used for different purposes.
To increase the moisture content of waste disposed in a bioreactor landfill, it is critical to secure the moisture source. In this study, industrial wastewater was evaluated as a potential moisture source for a bioreactor landfill with respect to the impact on methane generation. Industrial wastewater samples were collected from fishery, brewery and dairy industries. These samples were tested for basic water chemistry parameters, heavy metals, and methane generation using the regular and modified biochemical methane potential (BMP) assays. Despite high sodium and total phosphate concentrations in the fishery wastewater, a significant methane yield was observed (0.313 m3 CH4/kg COD). However, a relatively large amount of fishery wastewater added at the phase of methane generation acceleration adversely affected microbial activity. Samples from the brewery and dairy wastewater did not indicate significant inhibitory effects on methane generation in either the regular or the modified BMP assay. This study demonstrates the utility of wastewater as an alternative to traditional moisture sources when used to enhance methane production in a bioreactor landfill.
Methane is recovered from about 100 municipal solid waste landfills in the U.S. in saleable volumes, although yields are 1 to 50% of the methane potential of refuse based on biodegradability data. Studies on the microbiology of refuse decomposition and efforts to enhance refuse methanogenesis are reviewed here. Results of studies on the effects of leachate recycle and neutralization, a reduction in refuse particle size, the addition of anaerobic sewage sludge or old refuse as a seed, nutrient addition, calcium carbonate addition, and moisture on methane production are examined in consideration of new findings on landfill microbiology. A four‐phase description of refuse decomposition with leachate recycle, including an aerobic phase, an anaerobic acid phase, an accelerated methane production phase, and a decelerated methane production phase, is proposed. Mass balances and pumping tests may be used to estimate the methane potential of a sanitary landfill. The use of empirical, zero, and first‐order models to project methane production is reviewed.
The most common disposal method in the United States for municipal solid waste (MSW) is burial in landfills. Until recently, air emissions from these landfills were not regulated. Under the New Source Performance Standards and Emission Guidelines for MSW landfills, MSW operators are required to determine the nonmethane organic gas generation rate of their landfill through modeling and/or measurements. This paper summarizes speciated nonmethane organic compound (NMOC) measurement data collected during an intensive, short-term field program. Over 250 separate landfill gas samples were collected from emission sources at the Fresh Kills landfill in New York City and analyzed for approximately 150 different analytes. The average total NMOC value for the landfill was 438 ppmv (as hexane) versus the regulatory default value of 4000 ppmv (as hexane). Over 70 individual volatile organic compounds (VOCs) were detected and quantified in the landfill gas samples. The typical gas composition for this landfill was determined as well as estimates of the spatial, temporal, and measurement variability in the gas composition. The data for NMOC show that the gas composition within the landfill is equivalent to the composition of the gas exiting the landfill through passive vents and through the soil cover.
The major contributions to the thermal regime of an anaerobic domestic refuse landfill are identified and quantified. These are heat of reaction, specific heat of water/refuse mixtures, heats of neutralisation, heat losses to air and soil, solar radiation and aerobic metabolism. It is shown that even in temperate climates, landfill temperatures can rise to 45°C and above under anaerobic conditions with the concomitant reduction in fatty acid concentrations in leachate. This has been confirmed with field observations. Management requirements for establishing and maintaining temperatures of about 45°C in an anaerobic landfill are identified. Principally these involve allowing water into the site from the bottom and maintaining an insulating layer of refuse of about 4 m above the water-table in the landfill. The advantages of a bioreactive landfill are briefly discussed.
The composition of material excavated from the Burlington County landfill in New Jersey was determined, and the major reclaimed fractions characterized. Based on a waste age map, 98 samples 80 kg each collected from 13 gas extraction well borings were handsorted into 14 fractions and fines 2.54 cm that fell through the screen were collected. At least 50%, by weight, of the material was fines. The most abundant oversize materials overs fractions, by weight, were miscellaneous items, wood, other plastics not polyethylene terephthalate or high density polyethylene containers, and paper. Less paper was found in the oldest 7.5– 11.5 years section of the landfill P 0.10, most likely due to microbial degradation. Several of the characteristics of the materials excavated from the landfill, such as temperature, particle size, bulk density, volatile solids, and contamination were correlated with the age of the deposits made. High levels of adherent soil will likely prove to be an insurmountable obstacle to recycling most excavated waste fractions other than fines unless further processing is pursued.
In this study, waste management concept, waste management system, biomass and bio-waste resources, waste classification, and waste management methods have been reviewed. Waste management is the collection, transport, processing, recycling or disposal, and monitoring of waste materials. A typical waste management system comprises collection, transportation, pre-treatment, processing, and final abatement of residues. The waste management system consists of the whole set of activities related to handling, treating, disposing or recycling the waste materials. General classification of wastes is difficult. Some of the most common sources of wastes are as follows: domestic wastes, commercial wastes, ashes, animal wastes, biomedical wastes, construction wastes, industrial solid wastes, sewer, biodegradable wastes, non-biodegradable wastes, and hazardous wastes.
This paper presents the results of leachate quantity and quality measurement at 20 landfills in the northern part of West Germany over an average period of 3 years. The leachate flow rate could only be estimated as a percentage of annual pre-cipitation (measured precipitation 501–1057 mm year−1). The values for compaction with crawler tractors are 25–50% and with steel wheel compactors, 15–25%. The organic contents of leachate are dependent upon the kind of decomposition conditions (aerobic, anaerobic acetic production or anaerobic methane production). With anaerobic acetic production the volatile fatty acids produced in leachate have a high COD and BOD5. In the following methane production phase these acids are converted to CO2 and CH4 with low organic leachate contents. The concentrations of some inorganic components, such as Fe and Ca, are parallel as a result of changes in pH. Ammonia shows a slow increase with landfill age. In most cases the contents of heavy metals are lower than 1 mg 1−1.
The paper presents the results of investigation of methane fermentation of sewage sludge and organic fraction of municipal solid wastes (OFMSW) as well as the cofermentation of both substrates under thermophilic and mesophilic conditions. In the first experiment the primary sludge and thickened excess activated sludge were fed into a 40 dm3 bioreactor operated thermophilically. The second co-fermentation experiment was conducted with the mixture of sewage sludge (75%) and OFMSW (25%) in the same bioreactor arrangement. The other three experiments (III and IV, V) were carried out in quasi-continuous mode in two separated stages: acidogenic digestion in the continuous stirred tank bioreactor under thermophilic conditions (56 °C) and mesopholic methane fermentation (36 °C). The third experiment was conducted with the substrate-OFMSW only, in the fourth run sewage sludge from a municipal water treatment plant was used. In the fifth experiment a mixture of sewage sludge and OFMSW was used. In all experiments the following data were determined: biogas content and productivity, pH, total suspended and volatile solids, elemental content (C, H, N, S) of sludge, OFMSW and inoculum, total organic carbon, total alkalinity and volatile fatty acid content. Comparing the elemental analysis of sewage sludge and OFMSW it is evident that N content is higher in the sludge than in the OFMSW, however, the carbon content relation is the opposite, which may be beneficial to methane yield of co-digestion. Methane concentration in the biogas was above 60% in all cases. Biogas productivity varied between 0.4 and 0.6 dm3/g VSSadd depending on substrate added to the digester. The obtained results are generally consistent with literature data.