Gas Collection System Research Articles

Device for preventing the formation of liquid plugs in a gas collection system or in a non-straight gas well

Relevance. Almost all gas fields, both in Russia and in the world, are developed under water-pressure conditions, which means that sooner or later the field operator is faced with the problem of well watering and liquid accumulation at their bottom. The control methods proposed at this stage of development of science and technology and the useful models and inventions applied for this, although they show their effectiveness in removing droplet liquid from the production wellbore, do not contribute to the further advancement of the removed fluid through the system for collecting and preparing products. Because of this fact, a number of problems arise, for example, the formation of local resistance in the form of ice or hydrate plugs, the cause of which is the fluid removed from the wellbore. Aim. Development of a universal device that can be used both in the production collection and preparation system and inside production wells, capable of injecting produced water into the gas flow in order to prevent the formation of “stagnant zones” of liquid. Objects. Flooded gas wells, the gas pressure in which is not enough to remove droplet liquid from the wellbore or transport this liquid to the place of product preparation. Methods. Assessment and analysis of existing devices to prevent the formation of liquid plugs in a gas collection system, identifying their main shortcomings, as well as mathematical modeling of the proposed model, in which these shortcomings are eliminated. Results and conclusions. The paper introduces a brief description of the problem under study and studies and discusses the main methods of preventing the formation of liquid plugs, used in gas fields both in Russia and in other countries. The authors have proposed the design of a universal device, which is devoid of the main identified disadvantages of analogue devices, and carried out its simplified mathematical calculation.

Enhancing the performance of biofilters with sorption ability for simultaneous purification of landfill gases using laterite soil-based substrate

Various harmful gas emissions are a major controversial issue globally, and open dumpsites have become a leading contributor to atmospheric pollution. The study aims to introduce a high-performance landfill gas purification substrate using laterite soil, an iron, and aluminum-rich, highly available soil type in tropical countries; the final suggested substrate contained uniformly mixed laterite soil and compost with a 4:1 fraction by volume. A self-design setup that can maintain moisture content and aerobic conditions was used with an active landfill gas collection system through the gas wells established on the Karadiyana landfill in Sri Lanka under a tropical climate. The elimination capacity of CH4, NH3, VOCs, and H2S were 202860 ± 51595, 91 ± 30, 75 ± 27, and 6 ± 3 mg m−3 h−1 with 91 ± 3, 96 ± 1, 93 ± 3 and 83 ± 4% of removal efficiencies respectively at a 9.4 min empty bed residence time (EBRT). Selected laterite soil acts as an adsorption material and provides a better bio-filtering substrate with compost due to its specific characteristics. The hybrid gas purification process, absorption, and biofiltration within the proposed material were the reasons for higher performance, and the setup may be successful under the industrial waste gas streams. Further investigation should be carried out to study the medium's effectiveness as the covering layer on the dump with the successful lowest thickness, regarding secondary pollutants, and industrial applicability under unique specific conditions.

TECHNOLOGICAL SOLUTION FOR COMBATING HYDROGEN SULFIDE AT THE FIELD

One of the urgent problems in the production of hydrogen sulfide-containing oils is the problem of increasing the efficiency of hydrogen sulfide removal. Optimization of costs associated with the production, transportation and preparation of oil is very important at the present time. In order to reduce the costs of oil preparation, the use of a differentiated approach to solving the problem of its purification from hydrogen sulfide at the Kashagan field depends on the volumes of oil preparation, the mass fraction of hydrogen sulfide in the oil, the presence of gas near the high-sulfur oil preparation unit (UPVSN) that does not contain hydrogen sulfide, the presence of a gas collection system and the possibility of transporting increased volumes of hydrogen sulfide-containing gas to the sulfur purification unit. Taking these factors into account, it is necessary to identify the maximum values ​​​​of the volume fractions of methane, ethane, nitrogen and carbon dioxide in the composition of the stripping gas, at which the mass of oil will be preserved, as well as the conditions under which it will be purified from hydrogen sulfide in the conditions of the Kashagan field. Studies have shown that with an increase in the oil heating temperature and a decrease in the pressure in the desorption column, the maximum total volume fraction of methane and nitrogen in the mixture in the composition of the stripping gas decreases. A decrease in the mass fraction of hydrogen sulfide in oil below 100 ppm and maintaining the mass yield of oil depending on the proportion of these components in the composition of the stripping gas is possible if the oil temperature and pressure in the column are optimized. An increase in the total volume fraction of methane and nitrogen in the composition of the stripping gas leads to a decrease in its required consumption to achieve a certain efficiency of oil purification from hydrogen sulfide at specified operating parameters of the column.

Assessing Greenhouse Gas Emissions and Methane Production During Post-Landfill Maintenance in Kish Island: A LandGEM Simulation Approach

Background: Municipal solid waste (MSW) landfills are significant contributors to the emission of greenhouse gases, particularly methane, during the breakdown of waste materials. Researchers have undertaken extensive investigations into quantifying methane emissions from landfills, utilizing various methodologies beyond reliance on the LandGEM model. Numerous studies have underscored the efficacy of this model in predicting methane generation and exploring its utility in activities such as energy generation and emission mitigation strategies. Objectives: Municipal solid waste landfills are vital contributors to greenhouse gas emissions, notably methane, during waste decomposition. Significant research has focused on estimating methane output from landfills, utilizing various approaches beyond the LandGEM model. Studies highlight the model's potential in assessing methane generation and its relevance to activities like energy generation and emission management. Methods: The LandGEM simulation model is employed to forecast future waste generation and provide valuable insights into the environmental consequences of landfill management on the island. By analyzing population data and waste generation statistics from 2023 to 2042, the study utilizes the LandGEM software to estimate methane emissions, incorporating site-specific data and waste composition analysis. Results: The findings reveal that 36% of the total waste on Kish Island consists of putrescible material, with food waste being a significant component. Over the study period, approximately 1,282,637 tons of waste are projected to be disposed of in the Kish landfill. The LandGEM model predicts the highest landfill gas emission in 2043, primarily methane, along with carbon dioxide and non-metallic organic compounds. The estimated quantities for these gases in 2043 are 5.415E+03, 1.486E+04, and 2.327E+02 metric tons, respectively. Conclusions: This research highlights the importance of tailored waste management strategies to mitigate environmental impacts and emphasizes the need for efficient gas collection systems. A proposed gas collection system combining vertical wells, horizontal trenches, and under-membrane pipes is discussed to enhance efficiency and reduce environmental risks. The study provides valuable insights into waste management and landfill gas emissions on Kish Island, underscoring the significance of accurate emission prediction and effective management to minimize environmental consequences and optimize the utilization of renewable energy resources.

Optimizing Short Sprint Interval Training for Young Soccer Players: Unveiling Optimal Rest Distributions to Maximize Physiological Adaptations.

Present study aimed to compare the effects of SSIT intervention with varying rest distributions on hormonal, physiological, and performance adaptations in soccer players. Thirty-six players were randomly divided into three SSIT groups, each performing 4 sets of 6-10 repetitions of 6-second all-out running with rest intervals at ratios of 1:3, 1:6, and 1:9. Prior to and following the 7-week training period, aerobic fitness indices and anaerobic power were evaluated using a graded exercise test with a gas collection system and a lower-body Wingate test, respectively. Also, sport-specific bio-motor abilities were determined by measuring vertical jump, 20-m sprint, and T-test change of direction speed, Yo-Yo IR1 and maximal kicking distance. Hormonal status was also monitored by evaluating testosterone and cortisol levels. Following the 7-week training period, all SSIT interventions resulted in significant enhancements (p < 0.05) in soccer-related performance, physiological parameters, and hormonal adaptations, exhibiting effect sizes that ranged from small to large. Comparative analysis indicated that the 1:9 SSIT results in greater adaptive responses (p < 0.05) in the vertical jump, peak power, testosterone, and cortisol compared to the 1:3 SSIT group. By contrast, the 1:3 SSIT group induced more adaptive responses (p < 0.05) in the mean power output, maximum oxygen consumption (V̇O2max), and Yo-Yo IR1 compared to the 1:9 SSIT group. Hence, for enhancing physical performance, especially vertical jump height, anaerobic peak power, and hormonal adaptations, the 1:9 SSIT ratio is preferable. Conversely, shorter rest intervals (specifically, the 1:3 SSIT ratio) are better suited for eliciting heightened adaptive responses in mean power output, V̇O2max, and Yo-Yo IR1 over the 7-week training period among young male soccer players.

Optimal homeostatic stress to maximize the homogeneity of adaptations to interval interventions in soccer players.

This study examined the uniformity of adaptations in cardiorespiratory fitness and bio-motor abilities by analyzing individual responses to measures representing the mentioned qualities. Twenty-four male well-trained soccer players (Age = 26 ± 4years; stature = 181 ± 3.8; Weight = 84 ± 6.1) were randomized to two groups performing short sprint interval training [sSIT (3 sets of 10 × 4s all-out sprints with 20s of recovery between efforts and 3min of rest intervals between sets)] or a time-matched small-sided game [SSG (3 sets of 3 v 3 efforts in a 20 × 15m area with 3min of relief in-between)]. Before and after the 6-week training period, aerobic fitness indices, cardiac hemodynamics, and anaerobic power were assessed through a graded exercise test utilizing a gas collection system, noninvasive impedance cardiography, and a lower-body Wingate test, respectively. Also, sport-specific bio-motor abilities were determined by measuring linear speed, change of direction, and jumping ability. Comparing inter-individual variability in the adaptive changes by analyzing residuals in individual adaptations indicated that sSIT induces more uniform changes in the first and second ventilatory threshold (VT1 & VT2), stroke volume, and peak power output across team members than SSG. SSG also yielded lower proportions of responders in , VT1, VT2, peak, and average power output compared to sSIT. Additionally, the coefficient of variation in mean group changes in measures of aerobic fitness and bio-motor abilities in response to sSIT were lower than in SSG. Short sprint interval training induces more homogenized adaptations in measures of cardiorespiratory fitness and anaerobic power than small-sided games across team members.

Assessment of landfill gas storage and application regarding energy management: A case study in the province of Quebec, Canada

Landfills are extensively applied to dispose of municipal solid wastes in developed and developing countries. Landfill gas generation from biodegradable organic wastes can be collected and converted to energy. When the gas collection system is shutdown, some of this gas can accumulate and be stored inside the landfill. Using the gas storage capacity of the landfill gets a better management of the landfill site because the collected stored gas could transform the landfill into a cheap gas storage system to provide short-term energy and use the energy when needed. This novel study analyzes the stored methane using the gas collection data of a landfill in Quebec province, Canada, for modulating energy production from landfill gas. Twenty episodes of the gas collection system’s shutdown and restart as well as different gas flow durations were studied. The results showed that the collected stored methane is accumulated in an average of 2.5 h. Additionally, the collected stored methane represents 10.5% of landfill gas flow. Although the results are site-specific, the methodology of this paper can be used on other landfill sites with similar size and collection conditions. Designing new landfills could take into consideration some elements to enhance gas storage capacity. For instance, designing landfill daily covers with more granular materials and higher porosities can be the next step to enhance the landfill as a gas storage system during shutdowns.

Isothermal Dual-Phase Flow Modeling to Assess the Impact of Gas Collection on Geotechnical and Hydraulic Performance of Landfills.

Liquid addition to landfilled municipal solid waste (MSW) is a practice employed to accelerate the biodegradation of the organic fraction of MSW and ensuing gas generation. Pore landfill gas (LFG) and leachate pressure from the added moisture and enhanced gas generation are expected to impact the geotechnical stability of landfill slopes. The impact of moisture addition and gas collection on the stability of landfills was numerically modeled using transient isothermal dual-phase flow and slope stability modeling. The temporal variation in the factor of safety (FS) for slope stability analysis was estimated for the simultaneous flow of LFG and leachate with and without gas collection and leachate recirculation for varying LFG generation rates and waste moisture contents. A significant decline in the FS for landfill slope stability was observed when recirculating leachate without active gas collection. Even without pressurized leachate recirculation, a significant decline in the FS value was observed for landfills with relatively high in situ moisture content without active gas collection. In some modeled scenarios without LFG collection, the FS value was lower than 1. The analysis suggests that the landfill side slope stability analysis should incorporate LFG generation and the resultant pressure for landfills containing high-moisture-content waste and for the landfill with pressurized leachate recirculation. The analysis suggests that an efficient gas collection system plays a critical role in the geotechnical stability of the slope of wet landfills and the performance of leachate recirculation trenches.

Gas collection system design for a landfill via three-dimensional stochastic waste heterogeneity models and kriging

Installation of a gas collection system (GCS) at a landfill helps extract gas for domestic usage, alongside minimizing greenhouse gas emissions. To maximize the efficiency of gas extraction, it is important but challenging to design a GCS by modelling the three-dimensional, multiphase, multicomponent gas migration in a landfill, incorporating spatio-temporal variabilities in the geotechnical properties of the waste (viz., heterogeneity) and uncertainties (via stochastic models). This work proposes a method to calculate the radius of influence (ROI) of a gas extraction well (GEW) and designs a GCS for an actual landfill. The method models three-dimensional gas migration in a landfill via TOUGH simulator. Geotechnical properties are estimated using stochastic models to calibrate the simulator and obtain the gas flows at specific spatio-temporal locations. Gas flow values at the remaining locations are obtained through Kriging, based on which ROI is calculated. To ensure gas collection from the entire area of the landfill, 36 GEWs are placed. The spacing between GEWs is consistent with certain prevailing heuristic guidelines, and this work provides a justification for their use. A gas recovery efficiency of 0.82 and gas pressure of 103 kPa are achieved for a passive GCS under heterogeneity. A homogeneous design only yields an efficiency of 0.56, exemplifying the utility of the heterogeneous model. For an active GCS, the efficiency is found to be improved to 0.86. The framework provided in this work can be used for accurate gas flow estimation in large landfills, and design safe GCS ensuring minimal methane emission.

Waste to Energy: Review on the Development of Land Fill Gas for Power Generation in Sub-Saharan Africa

This study focused on the development of land fill gas for power generation in Sub-Saharan Africa. In rapidly expanding cities in developing and emerging nations, it has been observed that municipal solid waste (MSW) has increased dramatically, raising public concern about the effects on the environment and public health. In Sub-Saharan Africa today, the garbage of people within this region especially in Nigeria is carelessly disposed. Environmental pollution and its effects on people's quality of life have become more sensitive topics among residents and decision-makers in Sub-Saharan Africa. Additionally, municipal solid waste management (MSWM) is becoming a more important topic on the local political agenda. Local decision-makers routinely debate whether to invest in waste-to-energy technologies as part of their effort to modernize waste management systems. Waste-to-Energy technologies are being promoted more and more as an alluring solution to a number of problems, including the urgent issue of waste disposal. These issues include inadequate power production, a shortage of landfill space, and greenhouse gas emissions from improper waste management. As an alternative to waste burning and composting, landfilling is one of the municipal solid waste (MSW) disposal techniques that are most frequently used. Due to its financial benefits, the sanitary landfill method is still often employed in various nations for the final disposal of solid waste. Landfill gas (LFG) is mostly produced by the anaerobic breakdown of the biodegradable component of municipal solid waste (MSW), specifically kitchen and yard trash, which is disposed of in landfills. Due to the anaerobic breakdown of the organic portion of solid waste, landfill gas is continuously produced. As a result, if an extraction system is not constructed in a landfill, there will be an overpressure that will force the biogas to be released into the atmosphere, which will have an adverse effect on the environment. Methane and carbon dioxide make up the majority of the gases that make up landfill gas, which is a mixture of other gases. Many landfill sites include an operational gas collection system that draws gas from both horizontal and vertical gas wells using a blower. The gas from the landfill was thought to only include carbon dioxide and methane. Methane's typical volume composition is 49%, hence it was believed that carbon dioxide would have a volume composition of 51%. Reviewing the information gathered by numerous studies regarding the volume of waste being dumped in landfills reveals that the waste produced in sub-Saharan Africa is sufficient to power the area with electricity. It was discovered that the quantity of electricity generated will fluctuate over time based on the flow rate of landfill gas. It will initially rise until a peak is attained. A million tons of landfill waste typically emits 434,000 cubic feet of LFG each day, which is sufficient to generate 0.80 MW of power. About 70% of LFG projects use internal combustion engines, gas turbines, and micro-turbines to produce power.

Assessment of CH4 and CO2 Emissions from a Gas Collection System of a Regional Non-Hazardous Waste Landfill, Harmanli, Bulgaria, Using the Interrupted Time Series ARMA Model

Municipal solid waste (MSW) landfills are among the major sources of greenhouse gas (GHG) emissions affecting global warming and the Earth’s climate. In Bulgaria, 53 regional non-hazardous waste landfills (RNHWL) are in operation, which necessitates conducting studies to determine the environmental risk from the emitted GHGs. This study attempted to assess the CH4 and CO2 emissions from three gas wells of a cell (in active and closed phases, each of 2.5 years duration) in an RNHWL, Harmanli (41°54′24.29″ N; 25°53′45.17″ E), based on monthly in situ measurements by portable equipment, using the Interrupted Time Series (ITS) ARMA model. The obtained results showed a significant variation of the CH4 and CO2 concentrations (2.06–15.1% v/v) and of the CH4 and CO2 emission rates (172.81–1762.76 kg/y) by gas wells (GWs), months and years, indicating the dynamics of the biodegradation of the deposited waste in the areas of the three GWs. Throughout most of the monitoring period (2018–2022), the CH4 concentrations were higher than the CO2 concentrations (% v/v), while CO2 emissions were lower than CH4 emissions (kg/y), a fact that could be explained by the differences in the mass of the two gases. The emissions rates of both gases from GW2 dominated over those from GW1 and GW3, giving a reason to determine the zone of GW2 as a hotspot of Cell-1. On the whole, CH4 and CO2 emission rates were higher in the winter (December–February) and partly in the spring (March–May) compared to summer–autumn (June–November). However, the CH4 and CO2 concentrations and emissions decreased drastically after the Cell-1 closure. The CH4/CO2 ratio (0.68–2.01) by months and gas wells demonstrated a great sensitivity, making it a suitable indicator for the assessment of organic waste biodegradation level in the landfills. The ITS ARMA model confirmed the negative and significant effect of the cell closure on CH4 and CO2 emissions; the correlations found between predicted and observed values were strong and positive (0.739–0.896).

Modelling and simulation of landfill methane model

Methane emission modelling is essential for predicting landfill gas emissions and recovery, including sizing the landfill gas collection system. This study presents a developed methane emission model which can be replicated globally. The steps of model development and model equation are highlighted. The output from the developed model shows an average methane generation rate of around 8.06 m3/h in 1997 to about 16.17 m3/h in 2021. The results of the developed model have been critically addressed, and a comparison of the output is discussed with other models. The simulation done using the Monte Carlo approach shows a maximum deviation of around 18% from the developed model, validating the accuracy of the developed model. The findings of this study will serve as the basis for the development of a more robust LFG model for Indian as well as global landfills for methane recovery.

SISTEM MONITORING BIODIGESTER BERBASIS ARDUINO NANO

Biogas is a renewable energy source that is now a trend among the wider community because biogas fermented from feces or organic waste is relatively easy to do by ordinary people. Biogas can be a solution to overcome rising fuel prices due to depletion of petroleum. the price of fuel that rises due to depletion of petroleum. the utilization of biogas is currently felt to be less than optimal because the control system is still manual and less effective. Biodigester is a gas collection system for methane, carbon dioxide and other mixed gases obtained from the decomposition of organic materials such as cow dung by bacteria that cause methanogens in an anaerobic biodigester. With the Smart Biodigester Control System we can see waste data and can make the system more optimal, namely with the automatic biogas control system in the biodigester. In a tank that is 40 cm high we can see the waste data in the tank and the AC motor in the tank will stop when at a height of 35 cm. Strobe is not active if the pressure value does not exceed 0.4 Bar. The DC valve is active from the pH data value exceeding 7.5. The success rate is 98%, the remaining 2% is further research.

Landfill Codisposal of On-Site Vegetation and Coal Combustion Residuals: Implications for Gas Management

Historically, ash from coal combustion has been disposed of in ponds that were not designed with engineered containment systems. As a result of regulatory changes, it is estimated that coal combustion residuals (CCRs) from hundreds of unlined ponds will have to be excavated and disposed of in new lined landfills or the existing CCR ponds will have to been closed in-place with an engineered final cover system. The excavated or in-place CCR may contain vegetative matter that has the potential to decompose to CH4 and CO2. The objective of this study was to demonstrate a framework to assess the need for a gas collection system to accommodate the disposal of a mixture of CCR and vegetation in a lined landfill. Methane generation rates and yields for vegetative matter mixed with CCR were measured in biochemical methane potential and specific methane activity tests at 15, 20, and 37 °C. The data were then used to parameterize a methane generation model to estimate the gas flux at the landfill surface for a series of hypothetical disposal scenarios. Results showed that the specific decay rate constant (k) ranged from 0.00037 to 0.00872 yr–1, while the methane yield (L0) ranged from 84 to 120 mL CH4/dry g. Temperature was the most important determinant of the decomposition behavior. Simulations of gas flux for several disposal scenarios showed that the modeled flux from the decomposition of vegetation was below the CH4 and CO2 transmission rates reported for a geomembrane liner final cover system, suggesting that an active gas collection will not be necessary under the modeled disposal conditions.

Quantitative monitoring of dissolved gases in a flooded borehole: calibration of the analytical tools

Gas monitoring is a prerequisite to understanding the exchange, diffusion, and migration processes of natural gases within underground environments, which are involved in several applications such as geological sequestration of CO2. In this study, three different techniques (micro-GC, infrared, and Raman spectroscopies) were deployed on an experimental flooded borehole for monitoring purposes after CO2 injection. The aim was to develop a real-time chemical monitoring device to follow dissolved gas concentrations by measurements in water inside the borehole but also at the surface through a gas collection system in equilibrium with the borehole water. However, all three techniques must be calibrated to provide the most accurate quantitative data. For this, a first step of calibration in the laboratory was carried out. A new calibrations were required to determine partial pressure and/or concentrations of gases in water or in the gas collection system. For gas phase analysis, micro-GC, FTIR spectroscopy, and Raman spectroscopy were compared. New calibration of the micro-GC was done for CO2, CH4, and N2 with uncertainty from ±100 ppm to 1.5 mol% depending on the bulk concentration and the type of gas. The FTIR and Raman spectrometers were previously calibrated for CO2, and CO2, N2, O2, CH4, and H2O, respectively with an accuracy of 1–6% depending on concentration scale, gas and spectrometer. Dissolved CO2 in water was measured using a Raman spectrometer equipped with an immersion probe. The uncertainty on the predicted dissolved CO2 concentration and partial pressure was ±0.003 mol·kg−1 and ±0.05 bar, respectively.

Gas extraction hood modeling in a steel converter for energy recovery using phase change materials

The steel industry is characterized by its energy-intensive processes. The steel forming process stands out, where the oxidation of carbon, when reacting, generates incomplete combustion gases at high temperature through the process basic oxygen injection in the furnace (BOF). A model of intermittent process and high temperature gas collection system is proposed and validated through experimental measurements. Through it, energy improvement opportunities are analyzed, highlighting energy recovery from high temperature flue gases by incorporating a phase change material (PCM) method for temporary energy storage. It was estimated that the fumes inside the hood could provide 77 GJ of available energy during the 15 min of oxygen injection (blowdown). With the use of a PCM device, between 13% and 32% residual energy recovery is obtained, equivalent to 10–25 GJ. In this way, a continuous heat flow could be generated during the whole process for steam generation through a cooling system in the gas collection system, with an electricity generation potential with a Rankine cycle of 14.5 MW.

Landfill gas as a source of anthropogenic antimony and arsenic release

Antimony is used extensively in consumer goods, including single use plastic bottles, electronics, textiles and automobile brakes, which are disposed of in landfills at the end of their service lives. As a result, Sb is a constituent of concern in landfill emissions. Previous research has focused on leachate (liquid) and waste incineration flue gas emissions; however, Sb has the potential to volatilize through chemical and microbial processes within a landfill. In this study, iron-amended granular activated carbon was used to adsorb volatile metals directly from gas in a full-scale landfill gas collection system. Metals were quantified using acid digestion and ICP-AES analysis. Antimony concentrations far exceeded those previously reported, at up to 733 μg m−3 (mean: 254 μg m−3). In addition to Sb, As was also measured at high levels compared to previous research, as high as 740 μg m−3 (mean: 178 μg m−3). Using US EPA landfill and landfill gas databases, total Sb emissions via landfill gas are estimated to be approximately 27.3 kg day−1 in the US. Based on other estimates of national and global Sb emissions, this corresponds to approximately 4.5% of total US atmospheric emissions of Sb and 0.42% of global atmospheric emissions. Sb mass release via landfill gas is approximately 3.9 times higher than via leachate emissions. Although gas emissions are higher than expected, the vast majority (99.9%) of Sb present in landfilled MSW remains within the waste mass indefinitely. In addition to these mass release estimates, this experiment suggests that iron-amended activated carbon may offer significant metals removal from LFG, especially in the first months of new well operation.

Numerical model for static chamber measurement of multi-component landfill gas emissions and its application

The quantitative assessment of landfill gas emissions is essential to assess the performance of the landfill cover and gas collection system. The relative error of the measured surface emission of landfill gas may be induced by the static flux chamber technique. This study aims to quantify effects of the size of the chamber, the insertion depth, pressure differential on the relative errors by using an integrated approach of in situ tests, and numerical modeling. A field experiment study of landfill gas emission is conducted by using a static chamber at one landfill site in Xi’an, Northwest China. Additionally, a two-dimensional axisymmetric numerical model for multi-component gas transport in the soil and the static chamber is developed based on the dusty-gas model (DGM). The proposed model is validated by the field data obtained in this study and a set of experimental data in the literature. The results show that DGM model has a better capacity to predict gas transport under a wider range of permeability compared to Blanc’s method. This is due to the fact that DGM model can explain the interaction among gases (e.g., CH4, CO2, O2, and N2) and the Knudsen diffusion process while these mechanisms are not included in Blanc’s model. Increasing the size and the insertion depth of static chambers can reduce the relative error for the flux of CH4 and CO2. For example, increasing the height of chambers from 0.55 to 1.1 m can decrease relative errors of CH4 and CO2 flux by 17% and 18%, respectively. Moreover, we find that gas emission fluxes for the case with positive pressure differential (∆Pin-out) are greater than that of the case without considering pressure fluctuations. The Monte Carlo method was adopted to carry out the statistical analysis for quantifying the range of relative errors. The agreement of the measured field data and predicted results demonstrated that the proposed model has the capacity to quantify the emission of landfill gas from the landfill cover systems.

Assessment of biogas production from mixtures of poultry waste and cow dung

The increase price of cooking gas and high rate of deforestation (firewood) has led to search for an alternative source for cooking. This study was carried out to produce biogas from cow dung and poultry waste as well as the respective co-digestion of cow dung and poultry dung as alternative fuel for cooking. Four-liters digester and gas collection system were designed and fabricated using locally available materials. The digesters were used to digest cow dung and poultry dung respectively as a single substrate as well as to digest cow dung and poultry dung respectively. The respective materials were collected locally. They were fermented, digested and analyzed in accordance with standard methods for the single substrate. The total volume of gas produced was recorded for different mixtures of cow and poultry waste. The total volume of gas produced ranged from 222 cm3 (20g cow dung plus 60g poultry waste) to 258cm3 (80g cow dung plus 0g poultry). The result shows that cow dung produces more gas than the poultry waste. Therefore, it is recommended that biogas factories or industries should be established that make use of the abundant animal waste. This will reduce the over-dependence on other forms of energy.

Design of gas collection systems: Issues and challenges.

The design of a gas collection system (GCS) for a landfill involves estimating several critical parameters, such as the radius of influence (ROI), suction pressures, number of wells and their spacing. One of the biggest challenges lies in the estimation of ROI for a particular landfill. In this study, the ROI for a Bagalur landfill is estimated for various possible gas generation rates. ROI for active and passive GCS is estimated with numerical modelling (two-dimensional) for all definitions of ROI at different suction pressures. An inverse correlation was observed between the values of various definitions of ROI at different gas generation rates. Justification for this behaviour is brought out by addressing the conceptual difference between these definitions. The number of wells along with their spacing was then calculated, and the efficiency of the design was assessed with three-dimensional modelling. Passive and active systems had average methane recovery rates of 84% and 88%, respectively, with an atmospheric methane flux ranging from 10-9 to 10-10 kg m-2 s-1. The high recovery rate and low methane flux indicate the effectiveness of the design. The values of the methane flow rate from the extraction well were validated with a theoretical method, suggesting the usability of the model for future investigations.