Municipal Solid Waste Ratio Research Articles

Optimizing Biogas Production and Digestive Stability through Waste Co-Digestion

This study aimed to enhance the nutrient balance of municipal solid waste (MSW), characterized by a high carbon-to-nitrogen (C/N) ratio, which is a critical factor in the anaerobic digestion process. The investigation involved the addition of MSW, which is rich in carbon content, to food waste (FW) with high nitrogen content. The goal was to determine an optimal co-substrate mixing ratio of MSW and FW for anaerobic co-digestion at mesophilic temperatures, aiming to improve process stability and performance to achieve higher biogas yield. The co-digestion experiments encompassed five mixing ratios of MSW and FW with C/N ratios of 20, 25, 30, 35, and 40 under mesophilic conditions in a laboratory. The results indicated that the highest specific biogas yield, reaching 827 L/kg VS, was attained when the co-substrate feedstock had a balanced C/N ratio of 20, surpassing the 520 L/kg vs. obtained from MSW digestion alone. As the proportion of MSW increased in the co-substrate mixing feedstock, the biogas production rate decreased. Additionally, the study explored the optimal substrate-to-inoculum (S/I) ratio, focusing on the co-substrate feedstock with a C/N ratio of 20. Four S/I ratios (0.5, 1.0, 1.5, and 2.0) were examined, revealing that the highest specific biogas yield, at 642 L/kg VS, occurred at an S/I ratio of 0.5. An accumulation in volatile fatty acids (VFAs) was observed at higher S/I ratios, attributed to the lower abundance of inoculum microorganisms in the anaerobic digestion process. Overall, the findings suggested that the optimum C/N ratio for co-digestion of MSW and FW falls within the range of 20–25/1, while the preferred S/I ratio is 0.5.

Environmental sustainability by an integrated system based on municipal solid waste fluidized bed gasification using energy, exergy, and environmental analyses

As an eco-friendly method of waste disposal, municipal solid waste (MSW)-to-multi-generation energy systems based on gasification reduces the amount of waste sent to landfills, generates clean energy that can be used to power homes and businesses, reduces our reliance on fossil fuels, and helps to reduce greenhouse gas emissions. In this study, a novel system is developed based on MSW gasification by combining a fluidized bed gasifier, a solid oxide fuel cell (SOFC), and a heat recovery to produce heat and power. In-depth research is done on the power output, heating capacity, energy and exergy efficiencies, and emissions of this innovative combined heating and power system. Electrical and exergy efficiencies of the system are improved with the steam to MSW ratio from 40.6 % to 41.4 % and from 36.4 % to 37.0 %, respectively, and the emission is reduced. Increasing utilization factor enhances electrical (from 37.2 % to 44.4 %) and exergy (from 33.4 % to 39.6 %) efficiencies and declines the emission (from 955.2 to 800.7 kg/MW.s). Decreasing current density and increasing SOFC temperature boost the system performance from energy, exergy, and environmental viewpoints. The future of multi-generation energy systems based on MSW gasification looks bright, as they offer a sustainable way to manage waste while meeting the growing demand for clean energy.

Influence of oil and gas exploration and production waste on municipal solid waste hydraulic conductivity

This study evaluated the effects of addition of oil and gas exploration and production wastes (E&PW) on hydraulic behavior of municipal solid waste (MSW). A series of laboratory experiments were conducted to assess the impacts of vertical stress, waste composition, mixture ratio of MSW to E&PW based on total mass (e.g., 20% MSW + 80% E&PW), and mixing methods on hydraulic conductivity. Hydraulic conductivity (k) for MSW-E&PW mixtures with 20% and 40% E&PW contents reduced from 3 × 10-5 m/s to 10-7 m/s as vertical stress increased from 0 to 400 kPa. An increase in the mixture ratio above 60% resulted in an additional order-of-magnitude decrease in k to 10-8 m/s as vertical stress increased above 200 kPa. The addition of E&PW did not impact the available flow path, even though adding E&PW to MSW reduced the void spaces. This indicated that the waste matrix is capable of accepting E&PW while keeping the flow structure within the waste matrix. However, for vertical stress greater than 50 kPa, mixtures of MSW + 80% E&PW were observed to yield hydraulic conductivity < 10-9 m/s.

A study on the co-combustion of excavated waste and municipal solid waste: Thermogravimetric characteristics and gaseous pollutants emission

To investigate the co-combustion behavior, a thermogravimetric analyzer combined with Fourier transform infrared (TG-FTIR) analysis was conducted on the blending samples of excavated waste (EW) and municipal solid waste (MSW) at different ratios. In addition, the co-combustion experiment at 700, 800, and 900 °C was carried out on a fixed bed reactor to determine the typical gaseous pollutants emission. The degree of interaction is evaluated by the weight loss deviation rate of co-combustion and individual combustion. The greater the deviation rate indicates the more significant interaction effect. The results showed that there were significant interactions between MSW and EW during the co-combustion process. Co-combustion with MSW improved the ignition, burnout and comprehensive combustion performance of EW samples, and the improvement of the co-combustion performance of EW which was landfilled in 2005 (05-EW) was more obvious than that landfilled in 2015 (15-EW). The blending ratio of MSW below 40% can avoid the obvious incremental effect on the generation of HCl, SO2 and NOx, and the above gaseous pollutants were significantly suppressed at 700–800 ℃. Furthermore, co-combustion of 15-EW with MSW was more likely to exhibit inhibitory effects on gaseous pollutant emission. Based on the results of thermogravimetric analysis and pollutant emission experiment, the low MSW blending ratio (below 40%) and low combustion temperature (between 700 and 800 °C) could improve the combustion conditions of EW and suppress the emission of gaseous pollutants.

Investigation on the co-pyrolysis of municipal solid waste and sawdust: pyrolysis behaviors, kinetics, and thermodynamic analysis

ABSTRACT This paper aimed to disclose the interaction during the co-pyrolysis of sawdust (Wood) and municipal solid waste (MSW) using a thermogravimetric analyzer at the heating rates of 10, 30, and 50 °C/min. The results of thermogravimetric analysis (TGA) indicated that Wood enhanced the depolymerization reaction of plastics in MSW, while MSW could reduce the thermal decomposition temperature of lignocellulosic substances in Wood. In addition, the devolatilization indexes (Di) for the blended samples were approximately 3 times that of Wood, and the maximum of which was −2.5729 × 10−6 %·min−1·K−3 (in WM11), implying that co-pyrolysis was conducive to the release of volatile matter. Moreover, the apparent activation energy (Eα) was calculated by the Kissinger–Akahira–Sunose (KAS) and Flynn-–Wall–Ozawa (FWO) methods. When the mass ratio of MSW to Wood was 1:1, the value of the average activation energy (Eave) was optimal, which was 191.37 kJ/mol. Additionally, the experimental Eave of WM11 was 15.15 kJ/mol lower than the theoretical. Furthermore, thermodynamic parameters (ΔH, ΔG, and ΔS) were calculated, and the results verified that co-pyrolysis was a feasible and advantageous way to convert waste into energy.

Mesophilic batch co‐digestion of municipal solid waste and food waste: improved digester performance and stability at optimum organic loading rates

AbstractBACKGROUNDThe accumulative municipal solid waste (MSW) production calls for emerging efficient technology for its handling. Anaerobic digestion (AD) of MSW provides effective waste volatilization. The high C/N ratio of MSW and increasing organic loading rates (OLRs) are central AD restrictions that affect the AD process performance, inhibition due to aggregation of volatile fatty acids (VFAs), and rapid fall in pH.RESULTSThis study examines the consequence of OLRs on AD of MSW with a high C/N ratio of 406 in food waste (FW) to have a balanced C/N ratio of 30. Three batch scale digesters investigate under mesophilic conditions (35 °C) with OLRs of 10, 15, and 20 gVS L−1 to assess the digester performance and stability in biogas yield, methane yield, and volatile solids (VS) reduction. The cumulative biogas and methane yield are observed to be 1336 and 776 mL gVS−1, respectively, with a VS reduction rate of 78%, at 10 gVS L−1. VFA/alkalinity ratio ranges from 0.02 to 0.01 at OLR of 10 and 15 gVS L−1, which designates a higher buffering capability of the digester. While VFA/alkalinity ratio of 0.48 observes at OLR of 20 gVS L−1. A rapid deprivation in digester performance and stability finds at ORL of 15 and 20 gVS L−1. The cumulative biogas yield and methane yield decrease with the increase in OLR from 10 to 20 gVS L−1.CONCLUSIONThis study provided sufficient information for better AD processes and operational circumstances that are an optimum and effective method to convert organic matter to biogas fuel. © 2021 Society of Chemical Industry (SCI).

Investigation and Improvement of Content of Methane in Biogas Generated from Municipal Solid Waste.

The methane yield and overall biogas generation reduce drastically in the winter and summer season. The Biogas plant operators reported better results with the co-digestion of the municipal solid waste (MSW) with cow dung in changing weather conditions. In this research work the quality and content of methane in biogas generated from biogas plant is improved by co-digestion of MSW, cow dung along with the urine with better carbon to nitrogen (C/N) Ration. We took number of experiment using different ratio of MSW and additives to improve biogas. Rigorous experimentations concluded that the co-digestion of the MSW, cowdung and urine in the proportion of (55:35:10) with equal amount water in a portable bio digester for anaerobic digestion results into better methane production with maintaining C/N ratio and reducing time duration for flammable biogas production.

Co-combustion behaviors of municipal solid waste and low-rank coal semi-coke in air or oxygen/carbon dioxide atmospheres

Co-combustion characteristics and interactions of municipal solid waste (MSW) and low-rank coal semi-coke (LCSC) in O2/CO2 or air atmosphere are investigated by the thermogravimetric method, including analyses of thermodynamic, kinetic parameters and reaction mechanism function. Results indicated that addition of MSW and higher oxygen concentration improve the co-combustion performance of blends. There are three distinct peaks for co-combustion of blends in air atmosphere, while only two peaks in 30O2/70CO2 atmosphere. It indicates that the presence of CO2 in oxy-fuel atmosphere is conducive to semi-char burnout. Interactions of MSW and LCSC mainly occur between 260 °C and 650 °C, and the synergetic interaction is very obvious around the second peak region of combustion process. The average activation energies Ea show an upward trend with the increase in oxygen concentration, and the minimum value of Ea is obtained when the blend ratio of MSW is 50% which might be an optimal option for co-combustion of blends. Activation energy, enthalpy changes, Gibbs function and entropy changes for 50MSW50LCSC in 30O2/70CO2 atmosphere are 140.86 kJ mol−1, 138.33 kJ mol−1, 161.94 kJ mol−1 and − 41.44 J mol−1 K−1, respectively. In O2/CO2 atmospheres, F6 and F1 functions are more suitable to describe the starting and subsequent process of entail reaction. The results can provide a theoretical and practical guidance for the harmless disposal and resource utilization of MSW and LCSC.

Quantification of greenhouse gas emissions from different municipal solid waste treatment methods - case study in Ha Noi, Vietnam

This study focuses on defining the greenhouse gas (GHG) emissions from treatment of municipal solid waste (MSW) in Ha Noi city. Firstly, the MSW samplings at Nam Son and Xuan Son landfills were collected to identify the components. Based on the statistical data on the amount and ratio of MSW collected, the volume of MSW treated by different technologies was estimated. Then, the GHG emissions were quantified by applying the Intergovernmental Panel on Climate Change (IPCC) 2006 model. The annual GHG released from MSW in Ha Noi in 2017 was 1.1 million tons of CO2e from landfilling, 16.3 thousand tons of CO2e from incineration, and 76,100 tons of CO2e from composting. The GHG emission level from landfills is the highest (327 kg of CO2e per ton of treated waste), followed by composting (189 kg of CO2e per ton), and incineration (115 kg of CO2e per ton). The GHG emissions from landfills comprised nearly 90% of GHG emissions from MSW disposal in Ha Noi. The results also revealed that if there are no measures to recover landfill gas for energy generation, the GHG generated from MSW treatment facilities will also contribute significantly to the greenhouse effect and climate change impact. These research results also supply the basis information for decision-makers to select the appropriate MSW treatment technologies for Ha Noi in the context of increasing population pressure and environmental pollution.

A coupled hydro-mechanical-biodegradation model for municipal solid waste in leachate recirculation

The weight of Municipal solid waste (MSW) leads to a decrease of void ratio in landfill with depth and the biodegradation of MSW also results in decrease of void ratio with time. The spatial and temporal changes of void ratio of MSW have significant effects on its hydraulic properties and consequently influence the leachate recirculation process. In this paper, an advanced coupled hydro-mechanical-biodegradation (H-M-B) model is proposed to analyze the full coupling process for leachate recirculation taking into account the effect of initial density profile and its change due to biodegradation. A new solver is presented using the finite volume method based on the OpenFOAM platform to implement the coupled H-M-B model. The volume change caused by effective stress, degree of saturation and degradation, and the effect of void ratio change on hydraulic properties, can be taken into account in the coupled H-M-B model. The results calculated by the coupled H-M-B model illustrate the effect of void ratio on hydraulic properties, and the effect of compressibility, initial density and biodegradation on leachate recirculation. This study will contribute to the understanding of the leachate recirculation process and enhance the design of MSW landfills.

Electricity power generation from co-gasification of municipal solid wastes and biomass: Generation and emission performance

Global generation of municipal solid waste (MSW) is predicted to reach over 2.2 billion tons/year in 2025. Landfilling and incineration, the two most common conventional techniques for MSW processing, negatively impact public health. This study developed and demonstrated electricity generation by co-gasification of two underutilized resources: MSW and agricultural biomass. A patented design of 60-kW downdraft gasifier and an internal combustion engine with 10 kW generator were used to generate electricity from co-gasification of various ratios of MSW and biomass. The maximum heating values (LHV) of syngas obtained at MSW ratio of 0, 20, and 40 wt.% were 6.91, 7.74, and 6.78 MJ/Nm3, respectively. At all MSW to biomass ratios, the maximum electric load generated was 5 kW, with electrical efficiencies of 22, 20, and 19.5% at MSW ratios of 0, 20, and 40 wt.%, respectively. The engine CO, NOx, SO2, and CO2 emission decreased with increasing load, while HC emission increased with increasing load. CO, NOx, and CO2 emissions decreased, while HC and SO2 emissions increased with increase in MSW ratio. Thus, the co-gasification system provides a basis for future development of small-scale power generation to utilize local wastes.

Laboratory test investigations on soil water characteristic curve and air permeability of municipal solid waste.

The air permeability coefficient has a high correlation with the water content of municipal solid waste. In this study, continuous drying methodology using a tension meter was employed to construct the soil water characteristic curve of municipal solid waste (M-SWCC). The municipal solid waste air permeability test was conducted by a newly designed apparatus. The measured M-SWCC was well reproduced by the van Genuchten (V-G) model and was used to predict the parameters of typical points in M-SWCC, including saturated water content, field capacity, residual water content and water content at the inflection point. It was found that the M-SWCC was significantly influenced by void ratio. The final evaporation and test period of M-SWCC increase with the increase in void ratio of municipal solid waste. The evolution of air permeability coefficient with water content of municipal solid waste depicted three distinct characteristic stages. It was observed that the water contents that corresponded to the two cut-off points of the three stages were residual water content and water content at the inflection point, respectively. The air permeability coefficient of municipal solid waste decreased with the increase of the water content from zero to the residual water content. The air permeability coefficient was almost invariable when the water content increased from residual water content to the water content at the inflection point. When the water content of municipal solid waste exceeded the water content at the inflection point, the air permeability coefficient sharply decreased with the increase of water content.

Suppression of PCDD/Fs by Raw Meal in Cement Kilns

Raw meal of the cement production process could probably suppress the formation of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). In this study, these suppression effects were studied and compared during the co-processing of municipal solid waste (MSW) with conventional feed materials such as pure CaCO3, and pure CaO. A top suppression efficiency of 96% was achieved for a ratio of MSW to raw meal of 1:15. Moreover, NaCl and CuCl2 were added to the mix of feed material and MSW, to reveal the impact of additional chlorine and cations on PCDD/F formation. Similarly, the raw meal was mixed with the kiln dust to investigate possible suppression effects of those PCDD/Fs formed through the precursor or the de novo synthesis at a temperature of 350°C. The raw meal suppressed the formation of PCDD/Fs from kiln dust. Furthermore, the raw meal could not suppress the formation of PCDD/Fs on mixtures of kiln dust and NaCl or CuCl2, which could be associated with a potential increase in the formation effects of PCDD/Fs on the raw meal. The results can help in potential decision-making on the applicability of certain cement kilns on the co-processing of MSW containing high levels of Cl and Cu.

Co-cracking of real MSW into bio-oil over natural kaolin

Municipal solid waste (MSW) is a potential material that can be converted into bio-oil through thermal degradation process or pyrolysis. The efficiency and productivity of pyrolysis can be increased with the use of natural catalyst like kaolin. The addition of catalyst also reduces the overall cost of conversion process. In this study conversion of MSW into Bio Fuel using Pyrolysis in the presence of of natural kaolin as catalyst has been investigated for 60 min at 400°C temperature. During the process 0.5 w/w catalyst to MSW ratio was maintained. Gas chromatography-mass spectrometry (GC-MS) was used to analyse the chemical composition of bio fuel. It is found that bio-oil production increases substantially with the use of catalyst. It is observed that the production of bio-oil is 23.6 % with the use of catalyst in process, which was only 15.2 % without the use of catalyst. The hydrocarbon range distribution of oil produced through pyrolysis reveals that gasoline and diesel fuel (C5-C20) are its main constituents. The functional group detected in bio-oil by GC-MS analysis is similar to that of diesel-48 in which paraffin and olefin are major mass species.

Analytical Modeling to Simulate Gas Production for Various Tested Landfill Cells

AbstractThe gas extraction wells installed in landfills are used to control gas emission. The degradation of municipal solid waste (MSW) is the main influencing factor for gas production and migration. The symmetric equation of gas migration was established considering the gas extraction wells and peak behavior of the degradation rate. An analytical solution is presented. The peak behavior of degradation rate can be modeled by an equation. The steady degradation ratio of MSW is related to methane generation potential Lo in the LandGEM model. The extraction and injection tests can be well simulated by the symmetric change theory of gas pressure in landfills. From back analysis of the Brogborough test, both the MSW landfill degradation rate and the peak value of gas pressure increased with sludge addition. The degradation time at peak is less than about 700 days. The peak gas pressure in landfill with added sludge increases by 20%.

Shear strength characteristics of mechanically biologically treated municipal solid waste (MBT-MSW) from Bangalore

Strength and stiffness properties of municipal solid waste (MSW) are important in landfill design. This paper presents the results of comprehensive testing of shear strength properties of mechanically biologically treated municipal solid waste (MBT-MSW) in laboratory. Changes in shear strength of MSW as a function of unit weight and particle size were investigated by performing laboratory studies on the MSW collected from Mavallipura landfill site in Bangalore. Direct shear tests, small scale and large scale consolidated undrained and drained triaxial tests were conducted on reconstituted compost reject MSW samples. The triaxial test results showed that the MSW samples exhibited a strain-hardening behaviour and the strength of MSW increased with increase in unit weight. Consolidated drained tests showed that the mobilized shear strength of the MSW increased by 40% for a unit weight increase from 7.3kN/m3 to 10.3kN/m3 at 20% strain levels. The mobilized cohesion and friction angle ranged from 5 to 9kPa and 8° to 33° corresponding to a strain level of 20%. The consolidated undrained tests exhibited reduced friction angle values compared to the consolidated drained tests. The friction angle increased with increase in the unit weight from 8° to 55° in the consolidated undrained tests. Minor variations were found in the cohesion values. Relationships for strength and stiffness of MSW in terms of strength and stiffness ratios are developed and discussed. The stiffness ratio and the strength ratio of MSW were found to be 10 and 0.43.

Modeling of leachate recirculation using vertical wells in bioreactor landfills.

Leachate recirculation (LR) in municipal solid waste (MSW) landfills operated as bioreactors offers significant economic and environmental benefits. The subsurface application method of vertical wells is one of the most common LR techniques. The objective of this study was to develop a novel two-dimensional model of leachate recirculation using vertical wells. This novel method can describe leachate flow considering the effects of MSW settlement while also accounting separately for leachate flow in saturated and unsaturated zones. In this paper, a settlement model for MSW when considering the effects of compression and biodegradation on the MSW porosity was adopted. A numerical model was proposed using new governing equations for the saturated and unsaturated zones of a landfill. The following design parameters were evaluated by simulating the recirculated leachate volume and the influence zones of waste under steady-state flow conditions: (1) the effect of MSW settlement, (2) the effect of the initial void ratio, (3) the effect of the injected head, (4) the effect of the unit weight, (5) the effect of the biodegradation rate, and (6) the effect of the compression coefficient. The influence zones of LR when considering the effect of MSW settlement are smaller than those when neglecting the effect. The influence zones and LR volume increased with an increase in the injection pressure head and initial void ratio of MSW. The proposed method and the calculation results can provide important insight into the hydrological behavior of bioreactor landfills.

Sustainability Assessment of Solid Waste Management in China: A Decoupling and Decomposition Analysis

As the largest solid waste (SW) generator in the world, China is facing serious pollution issues induced by increasing quantities of SW. The sustainability assessment of SW management is very important for designing relevant policy for further improving the overall efficiency of solid waste management (SWM). By focusing on industrial solid waste (ISW) and municipal solid waste (MSW), the paper investigated the sustainability performance of SWM by applying decoupling analysis, and further identified the main drivers of SW change in China by adopting Logarithmic Mean Divisia Index (LMDI) model. The results indicate that China has made a great achievement in SWM which was specifically expressed as the increase of ISW utilized amount and harmless disposal ratio of MSW, decrease of industrial solid waste discharged (ISWD), and absolute decoupling of ISWD from economic growth as well. However, China has a long way to go to achieve the goal of sustainable management of SW. The weak decoupling, even expansive negative decoupling of ISW generation and MSW disposal suggests that China needs timely technology innovation and rational institutional arrangement to reduce SW intensity from the source and promote classification and recycling. The factors of investment efficiency and technology are the main determinants of the decrease in SW, inversely, economic growth has increased SW discharge. The effects of investment intensity showed a volatile trend over time but eventually decreased SW discharged. Moreover, the factors of population and industrial structure slightly increased SW.

Leachate recirculation in bioreactor landfills considering the effect of MSW settlement on hydraulic properties

During leachate recirculation, a bioreactor landfill will experience more rapid and complete settlement, which is mainly attributed to the weight of municipal solid waste (MSW) and its biodegradation. The settlement of MSW may cause the decrease of void ratio of MSW, which will influence the permeability of MSW and the leachate quantity that can be held in bioreactor landfills. In this study, a new one-dimensional model of leachate recirculation using infiltration pond is developed. The new method is not only capable of describing leachate flow considering the effect of MSW settlement, but also accounting separately leachate flow in saturated and unsaturated zones. Moreover, the effects of operating parameters are evaluated with a parametric study. The analyzing results show that the influence depth of leachate recirculation considering the effect of MSW settlement is smaller than the value without considering the effect. The influence depth and leachate recirculation volume increase with the increase of infiltration pond pressure head and MSW void ratio. This indicates that the field compaction of MSW has a great influence on the leachate recirculation.

Prediction of the compression ratio for municipal solid waste using decision tree

The compression ratio of municipal solid waste (MSW) is an essential parameter for evaluation of waste settlement and landfill design. However, no appropriate model has been proposed to estimate the waste compression ratio so far. In this study, a decision tree method was utilized to predict the waste compression ratio (C'c). The tree was constructed using Quinlan's M5 algorithm. A reliable database retrieved from the literature was used to develop a practical model that relates C'c to waste composition and properties, including dry density, dry weight water content, and percentage of biodegradable organic waste using the decision tree method. The performance of the developed model was examined in terms of different statistical criteria, including correlation coefficient, root mean squared error, mean absolute error and mean bias error, recommended by researchers. The obtained results demonstrate that the suggested model is able to evaluate the compression ratio of MSW effectively.