Seasonal methane emission from municipal solid waste disposal sites in Lagos, Nigeria

The Municipal Solid Waste (MSW) Sector is a major source of Methane ( CH4) emission, a Greenhouse Gas (GHG) that contributes to Climate Change. However, governments of developing countries have not been able to address the challenges posed by this sector due to inadequate funding and technical requirement. The objective of this study was to determine how seasonal variation influences the CH4 gas emission. The First Order Decay (FOD) Tier 1 Model was used to estimate CH4 emission from four Solid Waste Disposal Sites (SWDS) in Lagos namely: Ewu-Elepe (Ewu), Abule-Egba (A/E), Soluos (Sol), and Olushosun (Olu) covering the dry and wet seasons, respectively for the inventory year 2020. A known weight of the wet waste deposited was characterized. The study revealed that the Degradable Organic Carbon (DOC) for the dry season was 12.897 GgC/kgWaste while that of the wet season was 12.547 GgC/kgWaste. But, the methane gas generated during the wet season was 0.331 Gg higher than that of the dry season which was 0.134 Gg for the study period. This is an appreciable quantity of methane that can contribute to the global Climate Change impact if not addressed. Therefore, these waste types should be segregated from other recyclables and processed into compost or energy resource

Leachate management in the aftercare period of municipal waste landfills

The selection of a landfill leachate management strategy in order to shorten the aftercare period and reduce the leachate management cost is challenging. For decision making, it is important to understand 1) the main indicators of long-term leachate performance, 2) the target levels of these indicators must reach to indicate the end of the aftercare period and 3) the strategy to meet the target level of the indicators within the shortest time. The aim of this thesis is to establish a leachate emission prognosis tool for the determination of the length of the aftercare period and to use models to test the effects of different leachate management strategies on the length and overall leachate management costs of landfill aftercare. The first part of the research is a study of municipal landfill stabilization and emissions, made by systematically describing the long-term landfill leachate and gas (LFG) emission performance achieved by landfill simulators (landfill simulation reactors, LSRs). The results give a comprehensive picture of the waste biodegradation progress during the landfill aftercare period. The second part of the research is an evaluation of the feasibility of a biological on-site process to pretreat the leachate (mainly total nitrogen [TN] removal) for leachate recirculation, direct discharge and indirect discharge purposes from both technical and economic points of view. It is integrated with a case study of a cost estimation based on a real landfill condition as an important part of the study, conducted to define the applicability of the crucial leachate management alternatives. Based on the results of the LSR and biological leachate nitrogen removal studies, the possibility and feasibility of optimizing landfill leachate management and treatment were clarified by developing models for the estimation of long-term emissions from landfills of different sizes and evaluating the best options for leachate and nitrogen management during the aftercare period. The models developed can be used to express the importance of different target parameters and estimate the length of the aftercare period for a landfill that is effective at optimizing a cost-effective aftercare strategy. The modelling findings show that in conventional scenarios, without leachate recirculation, the aftercare period can last up to several centuries. With the highest leachate recirculation rate, the aftercare period can be shortened substantially, to 25 years and 75 years, in medium-sized and big landfills respectively; though this is technically more challenging to do for big landfills. These scenarios also showed that the lowest total and average (per m3) leachate management costs can be achieved at about 60% of the costs of conventional scenarios during the aftercare period

Development of a methanotrophic alternative daily cover to reduce early landfill methane emissions

Final covers, especially when supplemented with gas collection, are highly engineered systems to prevent landfill methane release into the atmosphere. However, some methane production begins even before open cells are covered and often well before final capping, representing an unaddressed source of methane release. A number of biotic cover designs, such as biofilters, biocovers, and bio-“windows”, have been proposed as supplements to gas collection or as top covers on older landfills lacking gas collection systems. These systems employ media that promote the growth of bacteria which are able to oxidize methane to carbon dioxide and water. The purpose of this investigation is to explore the potential use of the methane oxidation capacity of methanotrophs embedded in a “biotarp” to mitigate methane release from open, active landfill cells. If successful, the biotarp could serve as an alternative daily cover during routine landfill operation. A mixed methanotroph cell population was enriched and isolated from landfill cover soil. Three cell immobilization techniques were evaluated, including cell entrapment in alginate beads and in liquid-core gel capsules. Adsorption to a synthetic geotextile was found to be most feasible and yield the best methane oxidation rates (2.0 g CH4/day). Evaluation of nine geotextiles produced two that would likely be suitable biotarp components. Pilot tarp prototypes were tested in continuous flow systems simulating landfill gas conditions. Multilayered biotarp prototypes consisting of alternating layers of the two geotextiles were found to remove 16% of the methaneflowing through the biotarp. The addition of landfill cover soil, compost, or shale as amendments to the biotarp increased the methane removal to over 30%. With successful methane removal in a laboratory bioreactor system, prototypes were evaluated at a local landfill using flux chambers installed atop a landfill section with an intermediate cover layer. The 4-layered biotarp and amended biotarp configurations were all found to decrease landfill methane flux; however negative controls were also observed to reduce methane flux equally well. Spatial and chronological variations in methane flux were also noted

Use Of Vegetative Mulch As Daily And Intermediate Landfill Cover

Management of yard waste is a significant challenge in the US, where in 2008 13.2% of the 250 million tons of municipal solid waste (MSW) was reported to be yard waste. This study describes research conducted in the laboratory and field to examine the application of vegetative mulch as daily and intermediate landfill cover. Mulch was found to exhibit stronger physical properties than soil, leading to a more stable landfill slope. Compaction of mulch was found to be significantly greater than soil, potentially resulting in airspace recovery. Degradation of mulch produced a soil-like material; degradation resulted in lower physical strength and hydraulic conductivity and higher bulk density when compared with fresh mulch. Mulch covers in the field permitted higher infiltration rates at high rain intensities than soil covers, and also generated less runoff due to greater porosity and hydraulic conductivity as compared to soil. Mulch covers appear to promote methane oxidation more than soil covers, although it should be noted that methane input to mulch covers was more than an order of magnitude greater than to soil plots. Life cycle assessment (LCA) showed that, considering carbon sequestration, use of green waste as landfill cover saves GHG emissions and is a better environmental management option compared to composting and use of green waste as biofuel

Removal Of Colour, Cod And Nh3-N From Semi-Aerobic Sanitary Landfill Leachate Using Sulfonic Acid And Quaternary Amine Functional Group Resins

The application of ion exchange process in landfill leachate treatment was not well established in literature. Optimized operational conditions and the interaction among process variables for this treatment process were unidentified, leaving a substantial gap in landfill leachate treatment knowledge. In the present study, the treatment of stabilized landfill leachate using resin- cationic, anionic, cationic followed by anionic (cationic-anionic), and anionic followed by cationic (anionic-cationic) were established and documented for the first time

Enhanced biodegradation of model lignocellulosic wastes in laboratory-scale bioreactors and landfills

In municipal solid waste (MSW) landfills, lignocellulosic wastes degrade slowly and cause the slow and prolonged release of biogas into the atmosphere. This release is adding to anthropogenic climate change, which is arguably the biggest challenge humankind faces today and requires immediate attention. As a solution to this problem, the overall aim of this study was to enhance biodelignification in landfills. This aim was supported by two research questions - To what extent can enzymatic & bacterial biodelignification systems breakdown lignocellulose in realistic lignin wastes, with the prospect of enhanced biogas recovery? What is the impact of flow & heterogeneity on bacterial biodelignification systems in model lignocellulose-containing bioreactor landfills? Two representative lignocellulosic wastes found largely undegraded in old landfills, i.e. newspaper and softwood, were used. Lignin peroxidase enzyme and a recently isolated lignin-degrading bacterial strain (Agrobacterium sp.) were used in tests conducted in stirred bioreactors with methanogens from sewage sludge. Lignin peroxidase resulted in ~20% enhancement in cumulative methane produced in newspaper reactors. It had a negative effect on wood (~10% decrease in total methane generated compared to controls, possibly due to simultaneous depolymerisation and repolymerisation of lignin on the surface of the wood preventing further depolymerisation). Agrobacterium sp. strain enhanced biodegradation of both wood (~20% higher release of soluble organic carbon and enhanced breakdown) and newspaper (~2-fold biogas yield). Furthermore, homogeneous and heterogeneous pore-structure configurations containing newspaper and sand were prepared to mimic old landfills. In the homogeneous case, 2-fold enhancement of biogas yield occurs, which is consistent with soluble organic carbon (sOC)/pH profiles. In the heterogeneous case, there is no significant enhancement. This is likely due to the much lower hydraulic conductivity of the newspaper/sand mixture compared to the outer sand zone, resulting in preferential flow paths through the sand. This paired with very low pH and very high sOC in the column impacts the microbial communities and their activity adversely. Overall, this thesis has surveyed the literature and identified the problem of slowly degrading newspaper and woody wastes in landfills. It has formulated research questions addressing this problem by studying accelerated degradation of these wastes, and the application of this technology to conditions close to reallife field-scale conditions (flow, heterogeneity). Enzymatic and bacterial biodelignification systems show promise under stirred-bioreactor conditions, as well as homogeneous lab-scale landfills. However, under heterogeneous conditions, the biodegradation process is more complicated

Innovative landfill bioreactor systems for municipal solid waste treatment in East Africa aimed at optimal energy recovery and minimal greenhouse gas emissions

Landfilling is currently the dominant disposal method for municipal solid waste (MSW) in developing countries. Approximately 50% of the MSW generated in East Africa is disposed in landfills. Low costs and availability of land have made landfilling the most common waste management option in East Africa. Two main aspects associated with landfills are the landfill gas potential (LFG) and the greenhouse gas emission. A desk study into the development and application of landfill systems for treating MSW have indicated that the operation of landfills as bioreactors is an interesting and viable option for MSW management. The main objective of the thesis was to develop and describe landfill bioreactor (LFB) basedtreatment systems suitable for MSW in East African cities. MSW collected in these cities is characterized dominantly by a high content of organic material and a high moisture content. It is expected that a more sophisticated and modern form of landfill such as a LFB will become important as a treatment system for MSW in East Africa on the short and middle term. For this purpose, four innovative landfill bioreactor system options which are technically feasible and resource-recovery oriented that match the conditions of East African cities have been developed. These innovative system options of landfills operated as bioreactors were identified, elaborated and evaluated based on literature information regarding the construction and performance of landfill bioreactors in highly industrialized western countries and characteristics of MSW in East Africa, experimental research on pilot plant scale and desk studies regarding biological conversion of the waste, and modeling of the biodegradation rates and biogas production of MSW. The four system options were also evaluated by means of a semi-mathematical calculation model regarding their investment and operation costs, land space requirement, leachate treatment costs and savings, LFG generation and LFG collection and utilization costs and benefits, airspace recovery, greenhouse gas accounting and global warming avoidance.The results with respect to the evaluation were compared with a controlled dumpsite for MSW as currently applied in East Africa. All four modifications of the LFB show great advantages with respect to landfill size, amount of biogas collected and reduction of the emission of greenhouse gases.The innovative system options proposed in this thesis are useful and helpful for decision makers in making the choice of MSW disposal suitable for the East-African cities</p

Experimental Assessment of Coupled Physical-Biochemical-Mechanical-Hydraulic Processes of Municipal Solid Waste Undergoing Biodegradation.

Proper management and disposal of municipal solid waste (MSW) remains an unresolved global problem. One solution to handle existing and future MSW is to move away from modern landfills that focus on containment and move towards bioreactor landfills that promote MSW biodegradation and enhance methane (CH4) generation and its collection as an alternative energy source. Solid, liquid and gas phases of MSW coexist in different proportions within a landfill, and evolve with time due to concurring and coupled physical-biochemical-mechanical-hydraulic processes during MSW biodegradation. A fundamental understanding of the concurring processes is needed to design, monitor, and operate bioreactor landfills effectively and efficiently. Seven large-size (d=300 mm; h=600 mm) laboratory landfill simulators were developed to degrade unprocessed MSW of variable waste composition that is representative of the MSW in a mega-scale landfill. The simulators were operated and monitored for up to four years to assess the evolution of the physical, mechanical, and hydraulic properties of MSW, the evolution of the biochemical characteristics of generated leachate and biogas, and population dynamics of MSW-degrading microorganisms. The coupled processes were found to be systematic, correlated to each other, and dependent on initial waste composition. Testing of MSW in fresh and fully-degraded (retrieved from laboratory simulators) states was performed to assess the physical and mechanical properties of MSW using a unique 300-mm diameter simple shear apparatus. The shear strength and compressibility of MSW changed due to biodegradation and was a function of the initial waste composition and the biodegradation state. A relationship between the shear strength and shear-wave velocity of MSW was established for fresh and degraded MSW. Laboratory results on CH4 generation and settlement of MSW during biodegradation generated as part of this study were supplemented by an extensive database synthesized from the literature that includes laboratory results and field measurements from numerous landfills. The database was analyzed to quantify the influence of moisture content of waste, overburden pressure, landfill monitoring and control, and temperature on MSW degradation. Based on the findings of this study, recommendations to promote MSW biodegradation include enhancing biodegradation conditions, optimizing initial waste composition, and increasing biogas collection efficiency.PHDEnvironmental EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/120798/1/xcfei_1.pd