Degradation Of Municipal Solid Waste Research Articles

Biodrying of municipal solid waste-correlations between moisture content, organic content, and end of the biodrying process time.

Biodrying refers to the decomposition of organic municipal solid waste (MSW) under aerobic conditions. This process usually lasts 14days and requires large amounts of air to be injected into the waste matrix. The efficiency of the biodrying process depends on several geotechnical parameters, including initial moisture content, initial organic content, bulk density, dry density, solid particle density, and porosity. To examine the potential influence of these parameters on the biodrying process, we analyzed 13 biodried MSW samples. The results revealed a strong positive linear relationship between the initial moisture content and the mass loss percentage. In the first three days of the biodrying process, the waste mass rapidly decreased; afterwards, the daily mass loss occurred at a less rapid, more constant rate. The established average mass removal ratio between the volatile solids and water was 1:6.38 with a standard deviation of 1.06. Dry and solid particle densities were preserved in all 13 experiments; thus, the corresponding void ratio remained unchanged. This finding suggests that the settlement and degradation of MSW that occur during the biodrying process did not significantly influence the airflow rate.

Biochemical, hydrological and mechanical behaviors of high food waste content MSW landfill: Numerical simulation analysis of a large-scale experiment

The complex process of thermal-hydro-mechanical-biochemical (THMBC) coupled degradation in high food waste content (HFWC) municipal solid waste (MSW) is the main cause of intense heat, gas, and leachate generation in the landfills, which could lead to environmental disasters. A large-scale indoor experiment on HFWC MSW has been done with operations of loading, heated mature leachate recharging to study the rules of degradation. A THMBC coupled degradation model is used to analyze the results in the first 400 days drawn from the experiments, to explain how recharge of heated mature leachate accelerated degradation process and how was the portion of settlement led by intraparticle water release. The numerical simulation also calculated the landfill gas that was not collected in the experiment due to operational defects. The results show that recharging the heated mature leachate allows the stabilization process to occur at least six months earlier and settlement due to intraparticle water release accounts for half of the settlement in the first 60 days. The research indicates highly coupled THMBC model can be used to analyze the complex process in MSW degradation, make up for the shortcomings of physical experiments, and provide theoretical support for the design, construction, and management of landfills.

Effects of initial temperature and moisture content on heat generation during degradation of municipal solid waste

Heat generation from degradation of organic matter in municipal solid waste (MSW) often leads to increased landfill temperature. However, it is difficult to measure environmental heat loss in laboratory and field tests; therefore, little research has been conducted to evaluate heat generation during waste degradation under different initial temperatures and moisture contents. In this study, tests were conducted to investigate the effects of initial temperature and moisture content on heat generation during waste degradation. A simple formula for calculating heat generation was proposed. Within 200 h, the waste temperature decreased by about 70%, and lower initial moisture contents were associated with greater temperature decreases. The smallest temperature decrease of 47% and the greatest heat generation occurred when the initial temperature was 40 °C. The initial moisture content increased from 30% to 60% and the heat generation increased from 5% to 36%. The heat generation per unit mass of organic matter during the aerobic and anaerobic stages were 19.44–23.77 and 0.27–0.50 MJ·kg−1, respectively, indicating that the proposed formula for calculation of heat generated from waste degradation was reasonable. The results presented herein provide theoretical support for the prediction of heat generation and the recycling of heat resources in MSW landfill sites.

Enhancing biogas production in anaerobic digestion of MSW with addition of bio-solids and various moisture sources

This study aimed to investigate the influence of moisture content on the anaerobic digestion of municipal solid waste (MSW) with the addition of leachate, tap water, wastewater, and sewage sludge. To accomplish this, ten sets of batch experiments were conducted to examine the impact of these various moisture sources on the rate of degradation, indicated by cumulative biogas yield, volatile solids (VS) and total solids (TS) removal. The addition of sludge with leachate and wastewater to MSW resulted in biogas yields that were approximately 30 % higher than the biogas yield from MSW and wastewater alone. Based on the observations of VS removal, it was observed that the addition of sludge degraded about half of the substrate. Therefore, it was observed that the addition of 10 % sludge with leachate and wastewater to MSW provides the best outcomes. The lowest biogas yield was observed with the mixing of tap water with MSW. Further, it was determined that the optimal moisture content for MSW degradation should be greater than 75 % of field capacity (FC). The cumulative biogas yield decreased by more than 50 % when the moisture contents decreased from 100 % to 50 % of FC. The reduction in biogas production at low moisture contents is attributed to limited mass transfer, and the hydrolysis rate also slightly decreases with an increase in total solids. The kinetic study was also carried out using the first order, modified Gompertz, Transference, and Logistic models, and the predicted cumulative biogas yield was compared with the experimental data. The modified Gompertz and Logistic models showed the best fit (R2 ≥ 0.994) with the experimental data for all the sets. The sludge, leachate, and wastewater are produced in large quantities in developing countries, and this study may provide a possible utilization strategy of these wastes for accelerated degradation of MSW.

Isolation and Identification of Bacteria of Genus Bacillus from Composting Urban Solid Waste and Palm Forest in Northern Peru.

A technical challenge for composting in Peruvian cities with annual temperatures below 20 °C is that the degradation of municipal solid waste (MSW) is slow, so the identification of cold-adapted bacteria would be interesting for use as inoculants in places with these climatic conditions. This study isolated, identified, and evaluated bacterial strains with cellulolytic and amylolytic activities at low temperatures. Bacterial strains were isolated from the Chachapoyas Municipal Composting Plant and soil from the Ocol Palm Forest in northern Peru. The screening was carried out to evaluate the extracellular enzyme activity of the strains at low temperatures, grouping those with cellulolytic and cellulolytic/amylolytic activities. The DNA-barcoding using 16S rRNA and enzyme activity allowed the identification and selection of five species with enzymatic activity at 15 and 20 °C of the genus Bacillus, three with cellulolytic/amylolytic activity (B. wiedmanii, B. subtilis, and B. velezensis), and two with cellulolytic activity (B. safensis subsp. safensis, and B. subtilis). These strains showed tolerance to temperatures below optimum and could be used in further studies as inoculants for composting organic wastes at temperatures below 20 °C.

Study on the effect of landfill gas on aerobic municipal solid waste degradation: Lab-scale model and tests

Aeration is of great importance in landfill remediation. However, most existing studies on aerobic waste degradation ignore the presence of landfill gases. In this study, gas characteristics during aerobic waste degradation in the presence of landfill gas in lab-scale lysimeters were investigated. Oxygen (O2) was intermittently injected into municipal solid waste. Changes in the gas concentration and reaction rate of methane (CH4), carbon dioxide (CO2), and O2 during the reaction process were monitored and calculated. The results showed that all reactions, including aerobic degradation, CH4 oxidation, and anaerobic waste degradation, occurred simultaneously during landfill aeration. The maximum O2 consumption rate was 0.013 mol day−1 kg−1 dry waste. CH4 production was stimulated after the O2 content was insufficient to sustain the aerobic environment. Higher CH4 production was likely attributed to the remaining substrate and biomass from dead aerobic microorganisms decomposed by growing anaerobic microorganisms.Based on the biochemical reaction and principle of mass conservation, a gas balance model during waste aeration was established to analyze the proportions of aerobic waste degradation, CH4 oxidation, and anaerobic waste degradation. The CH4 oxidation reaction was more advantageous than the aerobic waste degradation reaction during aeration. With an increase in gas injection times, the anaerobic reaction gradually weakened. The maximum proportion of CH4 oxidation reaction could achieve at 21.4 % during aeration, which is of great significance for the waste degradation reaction. The maximum proportion of aerobic waste degradation and the minimum proportion of anaerobic waste degradation were approximately 16.0 % and 74.2 %, respectively. The results show that landfill gas should be considered in the progress of landfill aeration. This study provides a novel approach for calculating the proportion of reactions during landfill aeration, which deepens the understanding of the reaction process and contributes to the design of aerobic landfill projects.

Temperature effects on the hydraulic properties of unsaturated rooted soils

Soil temperature of vegetated landfill earthen covers varies with time during their service, due to heat released by the degradation of municipal solid waste. In this study, an experimental campaign to capture soil water-retention curve (SWRC) and hydraulic conductivity function (HCF) of unsaturated rooted soils was conducted at different temperatures (25, 45, and 60 °C). Simplified evaporation tests were conducted by subjecting soil specimens to a prolonged drying period at maintained temperature. Based on the responses of matric suction and water content, SWRC and HCF were determined by the instantaneous profile method. It was found that increasing temperature reduced water-retention capacity, due to root shrinkage, thermal expansion of liquid phase, and reduction in forces of capillarity and adsorption. Soil hydraulic conductivity was enhanced by the increase in soil temperature due to reduction of water viscosity and potential preferential flow at root channels induced by root shrinkage. Temperature effects on SWRC and HCF of rooted soils are suction-dependent. A new nonisothermal SWRC model was developed to capture the dual effects of roots and temperature. By using the same set of calibrated parameters, the model demonstrates its ability to predict SWRCs reasonably well within the range of temperature investigated.

Studies on Degradation of Organic Food Waste, Municipal Solid Waste, and Agriculture Waste from Kolhapur, Maharashtra, India

Present study deals with different types of organic waste samples collected from different areas of Kolhapur city such as food waste, agricultural waste and municipal waste. Different organic waste samples were degraded with increase in retention time from 1 to 50 days. The parameters like pH, EC, Nitrogen, Phosphorous and Potassium were studied after every 10 days of interval. The results were interesting showing increased degradation activity by using microorganisms. It is also evident in the study that if less energy is available for growth of microorganism less microbial biomass is produced. The result suggests that food waste degradation shows decrease in nitrogen, potassium, and phosphorous whereas organic carbon, organic matter was also decreased. Agriculture waste degradation shows organic carbon, organic matter, nitrogen decrease and increase in phosphorus, potassium. Municipal solid waste degradation shows decrease in nitrogen, phosphorus and slight increase in potassium and decrease in organic carbon and organic matter

A first-order kinetic model for simulating the aerobic degradation of municipal solid waste

Aerobic degradation models are important tools for investigating the aerobic degradation behavior of municipal solid waste (MSW). In this paper, a first-order kinetic model for aerobic degradation of MSW was developed. The model comprehensively considers the aerobic degradation of five substrates, i.e., holocellulose, non-cellulosic sugars, proteins, lipids and lignin. The proportion ranges of the five substrates are summarized with the recommended values given. The effects of temperature, moisture content, oxygen concentration and free air space (FAS) on the reaction rates are considered, and the effect of settlement is accounted for in the FAS correction function. The reliability of the model was verified by comparing simulations of the aerobic degradation of low food waste content (LFWC-) and high food waste content (HFWC-) MSWs to the literature. Afterwards, a sensitivity analysis was carried out to establish the relative importance of aeration rate (AR), volumetric moisture content (VMC), and temperature. VMC had the greatest influence on the aerobic degradation of LFWC-MSW, followed by temperature and then AR; for HFWC-MSW, temperature was the most important factor, then VMC and last was AR. The degradation ratio of LFWC-MSW can reach 98.0% after 100 days degradation under its optimal conditions (i.e., temperature: 55 °C, VMC: 40%, AR: 0.16 L min−1 kg−1 DM), while it is slightly higher as 99.5% for HFWC-MSW under its optimal conditions (i.e., temperature: 55 °C, VMC: 40%, AR: 0.20 L min−1 kg−1 DM).

Introduction of acid-neutralizing layer to facilitate the stabilization of municipal solid waste landfill

Rapid stabilization is important for landfill operation and beneficial for treatment capacity recovery, biogas production, and pollution control. Acidification of municipal solid waste (MSW) landfill hinders the degradation of MSW. In this study, a leachate-recirculated landfill bioreactor with acid-neutralizing layer (reactor BL) and a control landfill bioreactor without the acid-neutralizing layer (CL) were operated for 509 days. The pH of the landfill was increased by the acid-neutralizing layer. The landfill gas production volume increased by 18.3 % in reactor BL compared with CL during the study period, and the CH4 concentration was also increased. A greater MSW mass reduction was observed in reactor BL than in CL. Microbial community analysis demonstrated that the presence of the acid-neutralizing layer promoted the abundance of methanogens. Based on these observations, it is believed that application of the acid-neutralizing layer accelerated the stabilization by mitigating the acidification of landfill, which promote the abundance of methanogens and enhance the MSW degradation. These results help to understand the influencing mechanism of acid-neutralizing layer on the landfill stabilization, and provide a new approach for the practical landfill to achieve fast stabilization.

Applying the 15N labelling technique to material derived from a landfill simulation experiment to understand nitrogen cycle processes under aerobic and anaerobic conditions

Reactive nitrogen (N) species, such as ammonium (NH4+), nitrate (NO3) and gaseous nitrous oxide (N2O), are released into the environment during the degradation of municipal solid waste (MSW), causing persistent environmental problems. Landfill remediation measures, such as in-situ aeration, may accelerate the degradation of organic compounds and reduce the discharge of ammonium via leachate. Nonetheless, the actual amount of N in the waste material remains relatively constant and a coherent explanation for the decline in leachate ammonium concentrations is still lacking. Hence, the present study aimed to elucidate the dynamics of N and its transformation processes during waste degradation. To this end, the gross rates of organic N mineralization and nitrification were measured using 15N pool dilution in waste material derived from a landfill simulation reactor (LSR) experiment. The results revealed a high potential for N mineralization and nitrification, the latter of which declined with the diminishing amount of extractable ammonium (after aeration). The analysis of the concentration and isotopic composition of N2O formed confirmed incomplete denitrification as the main source for N2O. Moreover, the natural abundance of 15N was investigated in various waste N pools to verify the conclusions drawn from the 15N tracing experiment. δ15N values of total waste N increased during aeration, indicating that nitrification is the major driver for N losses from aerated waste. The application of stable isotopes thereby allowed unprecedented insights into the complex N dynamics in decomposing landfill waste, of their response to aeration and their effect on hydrological versus gaseous loss pathways.

Yard wastes generation, management and utilization in nigeria

Yard waste is a major constituent of municipal solid waste (MSW) that contain elements that can be used by microorganisms during biological degradation of MSW but whose economic values are less than the cost of collection, transportation, and processing for beneficial use. It is generated from the gardens, plant nurseries, road sweepings, and so on. Yard waste generation is inevitable in any society, and it is clear that rapid urbanization has resulted in significantly more yard waste generation than previously. Gardening is common in communities, whether rural and urban, resulting in garden wastes such as leaves, wood trimmings and grass clipping. At present, most of the yard wastes in Nigeria are illegally dumped into abandoned waste lands or burn up which is very harmful and had raised concerns for the environmental and human health. However, due to a lack of corresponding policy support and management requirements for yard waste usage in Nigeria, this study proposes remedies and proposals for yard waste utilization that are appropriate for Nigeria, based on successful technologies and regulations. So based on the real situation in Nigeria, it is imperative to replace the traditional methods of yard waste management with innovative ones to promote their proper utilization..

Out-of-sync heat and gas generation in landfill and its effect on slope stability

Heat and gas generation from the degradation of municipal solid waste affects landfill slope stability. Currently, the differences between heat and gas generation are understood, and landfill slope stability analyses considering these differences are required. In this study, the conducted laboratory and field monitoring tests indicated that heat generation peaked earlier than gas generation. The relationship between the heat and gas generation was then considered in a landfill slope stability analysis. The earlier the temperature and gas generation peaked, the lower the safety factor and the earlier the minimum safety factor appeared. The minimum safety factor generally occurred when gas generation peaked. The minimum safety factors obtained with consideration of the out-of-sync heat and gas generation were up to 1.25% greater than those obtained when the temperature or gas generation rate was maintained at a peak value. The later the temperature peaked, and the earlier the gas generation rate peaked, a higher leachate level resulted in a larger difference between the minimum safety factors obtained with and without consideration of the out-of-sync heat and gas generation. Landfill slope instability is more likely to occur in the initial stage of landfilling.

Technical and economic evaluation of using biomethane from sanitary landfills for supplying vehicles in the Southeastern region of Brazil

Population growth has increased the production of municipal solid waste (MSW). The processes of degradation of MSW generate products poluants such as biogas. However, reforming biogas into biomethane for energy use can reduce impacts and increase energy supply. This study aimed to assess the technical and economic feasibility of using biomethane generated from landfills in the Southeastern region of Brazil to supply vehicles. The economic feasibility of this endeavor was verified using Net Present Value (NPV), and the Internal Rate of Return (IRR). We estimated Greenhouse Gas (GHG) emission reductions by replacing diesel with biomethane, using a methodology proposed by the Intergovernmental Panel on Climate Change. We analyzed 50 different landfill consortia. Consortia with installed capacity less than 5500 m³/day were economically unviable. The NPV ranged from around US$-20.00 million to US$120.00 million, while project IRR, with CAPEX from US$ 4 million, remains approximately constant, around 35%. Replacing diesel oil with biomethane produced can offset 29.14 trillion tons of CO2eq emissions. Biomethane is one option for replacing fossil fuels. This study is innovative because it presents an analysis of biomethane's energy and economic potential in southeastern Brazil, the country's most developed region, helping develop the national biomethane market.

Effect of Degradation of Municipal Solid Waste On the Shear Strength Behavior from a Dump Site In Una Town, Himachal Pradesh

The behavior of shear strength property of municipal solid waste (MSW) during decomposition/degradation was presented in this study. The large-scale direct shear laboratory tests were performed for analyzing the variation in shear properties of fresh to decomposed waste. The physical characteristics, organic content, moisture content at different stages of degradation and increasing age were evaluated for better understanding of the mechanical response. The reduction in the organic fraction from 56% to 16.5% was observed with increase in depth. However, the unit weight increased with the degradation from 6.97 kN/m3 for fresh to 7.05-10.3 kN/m3 for degraded waste. The results obtained from the direct shear test indicated an increase in the angle of internal friction (φ) whereas cohesion (c) did not follow any pattern with degradation of waste. It was further observed that the fresh samples of MSW exhibited lower strength than degraded waste. The shear strength of waste was observed to increase with rise in finer fraction thereby also increasing the unit weight and density of the waste. The mobilized cohesion of waste was observed to vary from 31.9 kPa to 33.4 kPa with an increase in depth till 1.5 m. The results obtained from the tests were compared with the literature and the best fit shear strength parameters for the current study depending upon the degradation of waste was characterized by cohesion value 32.6 kPa and angle of internal friction of 21°.

Municipal Solid Waste as an Alternate Source of Energy: A Review

Municipal solid waste (MSW) is a big environmental challenge. However; it is a potential source of recycling materials, heat and energy. In developed countries this waste is used as resource to produce energy and compost; whereas in developing countries like India, collection, transportation and disposal of MSW are a big task. Wastes to energy technologies (WTE-T) play important role in sustainable management of MSW throughout the world. These technologies reduce the amount of waste as well as produce energy, which can be used to generate electricity. These include thermochemical treatment technologies, biochemical treatment technologies and utilization of landfill gas. Thermochemical techniques include Incineration, Gasification, Pyrolysis, Plasma arc gasification and Hydrothermal carbonization. Incineration is the most common technique used for treatment of MSW. It reduces 70% mass and 90% volume of MSW and sterile ash remains as byproduct. Gasification is advantageous over incineration, as gases are not released into atmosphere. Pyrolysis is the anaerobic thermal degradation of MSW, carried out in an oxygen free environment, producing gases (syngas), liquid and solid residuals. Syngas is composed of methane, hydrogen, carbon mono oxide and carbon dioxide. It can be used in engines, boilers, turbines, fuel cells and heat pumps. Plasma arc gasification also involves partial oxidation of MSW. Syngas and high quality producer gas is obtained that can be used as transport fuel, heat and to generate electricity. Hydrothermal Carbonization (HTC) is a complex process through which hydro-char is produced, which is similar to coal and can be used as a solid fuel for heat and power generation. Organic fraction of MSW is biodegradable and has high energy content. Biochemical treatment technologies are designed to utilize this fraction of MSW. Anaerobic digestion of organic waste is performed by microbes in absence of oxygen in a closed container (biogas digester), resulting in the reduction of waste and production of a combustible gas, biogas, a mixture of methane and carbon dioxide. Landfill gas is rich in methane and must be used to produce heat and energy. It usually consists of 50% methane and 50% CO2. Gas is collected by pipes and reaches the wells installed inside the landfills.

Coupled process modeling for energy generation from municipal solid waste degradation: Laboratory-scale and field-scale simulations

Coupled process modeling for energy generation from municipal solid waste degradation: Laboratory-scale and field-scale simulations

Production of high strength bioliquid from municipal solid waste (MSW) using mixed culture

Landfilling is one of the most commonly used methods of municipal solid waste (MSW) disposal. It is necessary because there are residues in all waste management processes that cannot be reused or recovered further and are essentially landfilled. For the degradation of MSW, thermal, mechanical and biological pretreatment techniques are used. MSW could be treated and converted into liquid biomass (bioliquid) by using enzymes. This research focused on the production of high strength bioliquid in MSW. The experiments were conducted in three stages namely: acclimatization process, preliminary study and factorial analysis to determine the production of high strength bioliquid in MSW. The selected factors were ratio of AMC and substrates (1:2 and 1:5), temperature (room temperature and 37 °C), pH (adjusted pH and no pH adjustment), PET plastics size (1cm2 and 4cm2) and Hydraulic Retention Time (3 hours and 9 hours). Design Expert software (Version 7) was used to construct an experimental table where all the factors were randomized. Two-level factorial analysis (TLFA) was used to analyze the most contributing factor and interaction between the factors. The results showed that the most significant factor was temperature, while the interaction factors were between temperature and HRT. The best conditions of COD increment were determined at AMC/S ratio 1:5, adjusted pH, PET plastics size of 1cm x 1cm, at room temperature and HRT of 3 hours. The experimental and targeted final increments of COD were 2.19 and 1.99 respectively. Since the error was less than 10%, it is acceptable, and the objectives of this research were successfully achieved.

Investigation of Characteristics landfill leachate using Large Scale Lysimeter under Anaerobic Conditions

Landfill behavior is dependent on the composition and characteristics of the region’s municipal solid waste (MSW) and environment conditions. In landfills that are difficult to understand, MSW undergoes several complex mechanisms such as physical, chemical, thermal and biological processes throughout its lifespan. In the present research, by setting up an anaerobic reactor, an attempt was made to understand such complex processes. The reactor was monitored for a total of 270 days under laboratory conditions, and the results obtained from the experimental program are presented and discussed in this paper. The program involves the monitoring by laboratory experiments of moisture content, pH, temperature, as well as physic-chemical characteristics of the leachate samples. The pH values observed were in the 5.8-7.9 range and indicate the achievement of the optimal condition for MSW degradation. MSW’s average volumetric moisture content and temperature were 53.03% percent and 30.7 Crespectively, indicating favorable conditions for microorganism growth. The results described in this paper could potentially be used in landfills to predict MSW behavior. The research also allows planners and engineers to consider the complex mechanisms for planning and running landfills efficiently for sustainable waste management.

Greenhouse gas emissions from semi-aerobic bioreactor landfills with different vent-pipe diameters.

The emission patterns of three greenhouse gasses (GHGs), viz. CH4, CO2, and N2O from landfills, were examined on a lab scale. Three simulated semi-aerobic bioreactor landfills (SABL1, SABL2, SABL3), with respective vent-pipe inner diameters (φ) of 25, 50, and 75mm, were used to investigate their effect on the greenhouse effect (GHE) during the municipal solid waste (MSW) stabilization process. We found that the vent-pipe φ influenced both MSW degradation and GHG emissions, increasing the vent-pipe φ which improved the removal of carbon and nitrogen-based pollutants. The GHG emissions were 364, 356, and 309kg CO2 equivalents per ton of MSW from the SABL2, SABL1, and SABL3, respectively, during the operation of 465days. Of the three GHGs, CH4 influenced the GHE the most, contributing 72.53%, 79.17%, and 71.42% in SABL1, SABL2, and SABL3, respectively. In the same sequence, CO2 (14.87%, 14.06%, and 21.9%) and N2O (12.6%, 6.77%, and 6.69%) were the second and third contributors to the GHE, respectively. Considering the rapidly MSW stabilization and the mitigation of GHG emissions, a vent pipe with φ of 75mm in the SABL column (φ of 800mm) was suggested. Moreover, the GHG mitigation in the SABL should be implemented by prioritizing CH4 collection and oxidation. The results provided a technical guidance for GHG mitigation in MSW management.