CH4 Removal Research Articles

In-situ neutralize methane emission from landfills in loess regions using leachate

In loess regions, landfilling is the predominant solid waste disposal and loess is usually used as landfill cover soil. However, the methane (CH4) bio-oxidation activity of virgin loess is usually below 0.01 µmol/(h g-soil). In this study, we proposed a method to improve CH4 removal capacity of loess by amelioration with mature landfill leachate, which is in-situ, easily available, and appropriate. The organic matter content of the ameliorated loess increased by 180%, reaching 19.69–24.88 g/kg-soil, with more than 90% being non-leachable. The abundance of type I methane-oxidizing bacteria and methane monooxygenase gene pmoA increased by 5.0 and 79 times, respectively. Consequently, the maximum CH4 removal rate of ameliorated loess reached 0.74–1.41 µmol/(h g-soil) at 25°C, which was 4-fold higher than that of water-irrigated loess. Besides, the CH4 removal rate peaked at 10 vt% CH4 concentration and remained at around 1.4 µmol/(h g-soil) at 15°C–35°C. The column test confirmed that the highest CH4 removal efficiency was at 30–10 cm below the surface, reaching 26.1%±0.4%, and the 50-cm-thick loess layer irrigated with leachate achieved more than 85% CH4 removal efficiency. These results could help to realize carbon neutrality in landfill sites of global loess regions.

Methane oxidation in the waters of a humic-rich boreal lake stimulated by photosynthesis, nitrite, Fe(III) and humics

Abstract. Small boreal lakes are known to contribute significantly to global CH4 emissions. Lake Lovojärvi is a eutrophic lake in southern Finland with bottom water CH4 concentrations up to 2 mM. However, the surface water concentration, and thus the diffusive emission potential, was low (< 0.5 µM). We studied the biogeochemical processes involved in CH4 removal by chemical profiling and through incubation experiments. δ13C-CH4 profiling of the water column revealed a methane-oxidation hotspot just below the oxycline and zones of CH4 oxidation within the anoxic water column. In incubation experiments involving the addition of light and/or oxygen, CH4 oxidation rates in the anoxic hypolimnion were enhanced 3-fold, suggesting a major role for photosynthetically fueled aerobic CH4 oxidation. We observed a distinct peak in CH4 concentration at the chlorophyll-a maximum, caused by either in situ CH4 production or other CH4 inputs such as lateral transport from the littoral zone. In the dark anoxic water column at 7 m depth, nitrite seemed to be the key electron acceptor involved in CH4 oxidation, yet additions of Fe(III), anthraquinone-2,6-disulfonate and humic substances also stimulated anoxic CH4 oxidation. Surprisingly, nitrite seemed to inhibit CH4 oxidation at all other depths. Overall, this study shows that photosynthetically fueled CH4 oxidation can be a key process in CH4 removal in the water column of humic, turbid lakes, thereby limiting diffusive CH4 emissions from boreal lakes. Yet, it also highlights the potential importance of a whole suite of alternative electron acceptors, including humics, in these freshwater environments in the absence of light and oxygen.

Pd/SiO2 as an active and durable CH4 oxidation catalyst for vehicle applications

The removal of CH4 is critical to address environmental concerns for developing natural gas vehicles (NGVs), because CH4 has a 20-fold-greater contribution to the greenhouse effect than CO2. Alumina supported Pd catalysts are widely used for CH4 oxidation due to their superior catalytic activity and durability compared to other CH4 oxidation catalysts. However, the continuous deactivation of Pd-based catalysts during vehicle applications needs further development of active and durable catalysts. Here, we report that Pd/SiO2 can be active and durable catalysts for CH4 oxidation in practically relevant condition via a simple reductive regeneration. CH4 oxidation light-off curves of freshly prepared Pd/SiO2 (air, 550°C) present higher activity than those of Pd/Al2O3, but severe deactivation was observed after hydrothermal aging (HTA, air with 10% H2O) at 850°C. However, X-ray diffraction (XRD), scanning transmission electron microscopy (STEM) and volumetric CO adsorption suggest that Pd/SiO2 has similar particle sizes as Pd/Al2O3 even after HTA, indicating that Pd/PdO particle sintering is not the origin of the deactivation of Pd/SiO2. Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) shows that the CO was not adsorbed on Pd/SiO2 after HTA, whereas it was adsorbed on Pd/Al2O3 after HTA. These results demonstrate that the deactivation of Pd/SiO2 originates mainly from the blockage of the Pd/PdO surface by the SiO2 overlayer formed during HTA. The Pd/PdO surfaces are re-exposed by a simple H2 treatment at 500°C, resulting in CO adsorption on the Pd/PdO surface and regeneration for CH4 oxidation activity, which suggests that the Pd/PdO surface was re-exposed by a reduction treatment. This work also demonstrates that SiO2-supported Pd catalysts can be a good candidate for active and durable CH4 oxidation catalysts by using the proper regeneration protocols.

Numerical Analysis of a Continuous Vulcanization Line to Enhance CH4 Reduction in XLPE-Insulated Cables.

Herein, we apply a computational diffusion model based on Fick’s law to study the manner in which a cable production line and its operating conditions can be enhanced to effectively reduce the CH concentration in cables insulated with cross-linked polyethylene (XLPE). Thus, we quantitatively analyze the effect of the conductor temperature, curing tube temperature distribution, transition zone length, and online relaxation on CH generation and transport during the production of 132 kV cables with an insulation thickness of 16.3 mm. Results show that the conductor temperature, which is initially controlled by a preheater, and the curing tube temperature distribution considerably affect the CH concentration in the cable because of their direct impact on the insulation temperature. The simulation results show 2.7% less CH remaining in the cable when the preheater is set at 160 °C compared with that when no preheater is used. To study the curing tube temperature distribution, we consider three distribution patterns across the curing tube: constant temperature and linear incremental and decremental temperature. The amount of CH remaining in the cable when the temperature was linearly increased from 300 to 400 °C was 1.6% and 3.7% lower than in the cases with a constant temperature at 350 °C and a linear temperature decrease from 400 to 300 °C, respectively. In addition, simulations demonstrate that the amount of CH removal from the cable can be increased up to 9.7% by applying an elongated and insulated transition zone, which extends the residence time for CH removal and decelerates the decrease in cable temperature. Finally, simulations show that the addition of the online relaxation section can reduce the CH concentration in the cable because the high cable temperature in this section facilitates CH removal up to 2.2%, and this effect becomes greater at low production speeds.

Enhancement of CH4 oxidation potential in bio-based landfill cover materials

This study evaluated the efficacy of two compost materials, yard waste and leaf compost (YWLC) and biosolids compost (BSC), as bio-based landfill cover materials for oxidizing methane (CH4). A series of laboratory batch incubations were conducted to assess the CH4 oxidation potential of the composts and potential enhancement of CH4 oxidation under different conditions. Higher initial rates of CH4 oxidation were yielded in a sample of YWLC cured beyond the maturity standard at the compost site due to a reduction in raBOD and subsequent reduction in heterotrophic competition for oxygen. Results showed that the YWLC already had methanotrophic bacteria within the compost community with an initial CH4 oxidation rate of up to 95.9 μmol g(d.w.)−1 d−1. An optimum moisture content (MC) of 65 % and 50 % ww was obtained for YWLC with CH4 oxidation rates of up to 175−180 μmol g(d.w.)-1 d-1. In an assessment of long-term CH4 oxidation rates, a sample of BSC showed a long lag (60 days) to start consuming CH4; however, after this lag, it reached a CH4 oxidation rate of 160−170 μmol g(d.w.)-1 d-1, which was similar to that of the YWLC (130−140 μmol g(d.w.)-1 d-1) at the end of the 100 day experiment. While very little initial CH4 removal was detected in the BSC, different blends of BSC with YWLC were found to enhance CH4 oxidation indicating that there was a benefit to mixing the two composts. The highest long-term CH4 oxidation rates were observed in 1:1 and 1:4 (YWLC:BSC) mixing ratios (360−380 μmol g(d.w.)-1 d−1). Neither the in-situ MC, heavy metals concentrations, nutrient content, nor the in-situ population of methanotrophs were determined to be limiting variables for CH4 oxidation start-up in the BSC.

Part B: Advances in gas emission control techniques for anaerobic-based STPs Technical Note 5 – Biofiltration systems for waste gas treatment

Nos efluentes de reatores anaeróbios estão presentes gases produzidos durante o processo de tratamento (e.g. CH4 and H2 S). The techniques for controlling the emissions of the gases presented in this collection of Technical Notes (TNs) are based on the principle of desorption of the dissolved gases in effluent, through their transfer to the gaseous phase. The resulting gas, called waste gas, must be properly managed, for example, by means of its destruction/oxidation in biofilters or biotrickling filters. These biofiltration techniques can also be used to treat the waste gas generated in confined areas for odor and corrosion control in the sewage treatment plants (STPs). In this sense, the present TN seeks to contribute to the knowledge of the H2 S and CH4 treatment process through biofiltration. The necessary conditions for the biofiltration of H2 S and CH4 are quite different, reaching H2 S removal efficiencies between 90% and 100% for detention times between 1 and 2 min, and CH4 removal efficiencies between 70% and 100% for much longer detention times, between 20 and 30 min, considering the use of sequential bioreactor systems.

Sulfate-Methane Transition Depths and Its Implication for Gas Hydrate

The biological removal of CH4 by methanotrophic (CH4 -oxidizing) archaea always occurs at a distinct zone which is known as sulfate-methane transition zone (SMTZ). It is an important indication for high methane flux and gas hydrate occurrence. In this study, we collected pore-water data from Southern China Sea, Carolina Rise and Blake Ridge to analyze the relationship between CH4, SO42−concentration and depth. We found that below the SMTZ, the methane concentration increases continuously with depth and sulfate concentration decrease linearly to zero. In addition, the geochemical data taken from all these sites show that SMTZ is relatively shallow (less than 20m), which may indicate that these areas have high methane flux.

Process optimization and energy analysis of vacuum degasifier systems for the simultaneous removal of dissolved methane and hydrogen sulfide from anaerobically treated wastewater

The control of dissolved methane (CH4) and hydrogen sulfide (H2S) emissions in anaerobic effluents is essential for minimizing the environmental implications of greenhouse gases, odor, and carbon footprint, as well as for preventing energy loss in the form of unrecovered dissolved methane. This study assessed the feasibility of a vacuum degasifier for the removal of CH4 and H2S from staged anaerobic fluidized membrane bioreactor (SAF-MBR) effluent. The optimization results showed that the efficiency of the nozzle fitted degasifiers were superior to the media packed ones. In three-stage vacuum degasifiers at a −0.8 bar vacuum pressure, H2S removal was mostly pH dependent and 88% removal efficiency was achieved with an initial concentration of 13.6 mg/L. Methane removal was dependent primarily on the number of degasifier units, and approximately 94% efficiency was achieved in a three-stage degasifier. Energy balance analysis showed that energy production exceeded the system energy requirements with 0.05–0.07 kWh/m3 of surplus energy. These results provide deep insights into this new technology for simultaneous removal of dissolved CH4 and H2S, which can be referred for potential future applications.

CO2-SR Cyclic Technology: CO2 Storage and in situ Regeneration with CH4 over a new dual function NiBa unsupported catalyst

A Ni-Ba unsupported catalyst has been developed to be used as a dual function material (DFM) for a new CO2 storage and in-situ regeneration (CO2-SR technology), consisting in a CO2 storage step followed by a CH4 regeneration phase, working in alternating, cyclic and isothermal regime. The heterometallic mixed-oxide catalyst -NiO.BaO- used in this technology was prepared by an ultrasonic assisted coprecipitation using 1:1 atomic ratio (Ni:Ba) and colloidal silica as an agent promoting surface area and improving mechanical properties. The solid obtained maintains the fcc-structure at higher temperatures, demonstrates high reducibility as a bulky catalyst and presents a connected and balanced strong basic sites and CH4 activation centres. It showed a CO2-storage net capacity of 0.232 mmolCO2 g−1 and a CO2 and CH4 removal rate of 13.97 % and 11.04 % respectively, with a remarkable selectivity to hydrogen as an enriched-synthesis gas (H2+CO) stream at 600 °C.

Impact of iron release by volcanic ash alteration on carbon cycling in sediments of the northern Hikurangi margin

We present geochemical data collected from volcanic ash-bearing sediments on the upper slope of the northern Hikurangi margin during the RV SONNE SO247 expedition in 2016. Gravity coring and seafloor drilling with the MARUM-MeBo200 allowed for collection of sediments down to 105 meters below seafloor (mbsf). Release of dissolved Sr2+ with isotopic composition enriched in 86Sr (87Sr/86Sr minimum = 0.708461 at 83.5 mbsf) is indicative of ash alteration. This reaction releases other cations in the 30-70 mbsf depth interval as reflected by maxima in pore-water Ca2+ and Ba2+ concentrations. In addition, we posit that Fe(III) in volcanogenic glass serves as an electron acceptor for methane oxidation, a reaction that releases Fe2+ measured in the pore fluids to a maximum concentration of 184 μM. Several lines of evidence support our proposed coupling of ash alteration with Fe-mediated anaerobic oxidation of methane (Fe-AOM) beneath the sulfate-methane transition (SMT), which lies at ∼7 mbsf at this site. In the ∼30-70 mbsf interval, we observe a concurrent increase in Fe2+ and a depletion of CH4 with a well-defined decrease in δ13C-CH4 values indicative of microbial fractionation of carbon. The negative excursions in δ13C values of both DIC and CH4 are similar to that observed by sulfate-driven AOM at low SO42− concentrations, and can only be explained by the microbially-mediated carbon isotope equilibration between CH4 and DIC. Mass balance considerations reveal that the iron cycled through the coupled ash alteration and AOM reactions is consumed as authigenic Fe-bearing minerals. This iron sink term derived from the mass balance is consistent with the amount of iron present as carbonate minerals, as estimated from sequential extraction analyses. Using a numerical modeling approach we estimate the rate of Fe-AOM to be on the order of 0.4 μmol cm−2 yr−1, which accounts for ∼12% of total CH4 removal in the sediments. Although not without uncertainties, the results presented reveal that Fe-AOM in ash-bearing sediments is significantly lower than the sulfate-driven CH4 consumption, which at this site is 3.0 μmol cm−2 yr−1. We highlight that Fe(III) in ash can potentially serve as an electron acceptor for methane oxidation in sulfate-depleted settings. This is relevant to our understanding of C-Fe cycling in the methanic zone that typically underlies the SMT and could be important in supporting the deep biosphere.

Choline-Based Ionic Liquids-Incorporated IRMOF-1 for H2S/CH4 Capture: Insight from Molecular Dynamics Simulation

The removal of H2S and CH4 from natural gas is crucial as H2S causes environmental contamination, corrodes the gas stream pipelines, and decreases the feedstock for industrial productions. Many scientific researches have shown that the metal-organic framework (MOF)/ionic liquids (ILs) have great potential as alternative adsorbents to capture H2S. In this work, molecular dynamics (MD) simulation was carried out to determine the stability of ILs/IRMOF-1 as well as to study the solubility of H2S and CH4 gases in this ILs/IRMOF-1 hybrid material. Three choline-based ILs were incorporated into IRMOF-1 with different ratios of 0.4, 0.8, and 1.2% w/w, respectively, in which the most stable choline-based ILs/IRMOF-1 composite was analysed for H2S/CH4 solubility selectivity. Among the three choline-based ILs/IRMOF-1, [Chl] [SCN]/IRMOF-1 shows the most stable incorporation. However, the increment of ILs loaded in the IRMOF-1 significantly reduced the stability of the hybrid due to the crowding effect. Solvation free energy was then computed to determine the solubility of H2S and CH4 in the [Chl] [SCN]/IRMOF-1. H2S showed higher solubility compared to CH4, where its solubility declined with the increase of choline-based IL loading.

Enhancement of the methane removal efficiency via aeration for biochar-amended landfill soil cover

Methane (CH4) mitigation of biocovers or biofilters for landfills is influenced by the bed material and oxygen availability. The improvement of active aeration for the CH4 oxidation efficiency of biochar-amended landfill soil cover was investigated over a period of 101 days. There were column 1 as the control group, column 2 with biochar amending the soil cover, and column 3 with daily active aeration besides the same biochar amendment. All groups were inoculated with enriched methane oxidation bacteria (MOB). The average CH4 removal efficiency was up to 78.6%, 85.2% and 90.6% for column 1, 2, and 3, respectively. The depth profiles of CH4 oxidation efficiencies over the whole period also showed that the stimulation of CH4 oxidation by biochar amendment was apparent in the top 35 cm but became very faint after two months. This probably was due to the rapid depletion of nitrogen nutrition caused by enhanced methanotrophic activities. While through aeration, CH4 oxidation efficiency was further improved for column 3 than column 2. This enhancement also lasted for the whole period with a reduced decline of CH4 oxidation. Finally, the major MOB Methylocystis, commonly found in the three columns, were most abundant in the top 35 cm for column 3. A more balanced ratio of MOB and more homogeneous microbial community structures across different soil depths were also the results of active aeration.

A finite-volume numerical model for temporal and spatial variability of methane oxidation in landfill covers

Abstract A multi-field model is proposed to study methane oxidation in landfill covers, especially its temporal and spatial variability. The proposed model consists of water-gas two-phase flow, multi-component gas flow, heat transfer, and biochemical reaction modules, and is solved using OpenFOAM based on the finite volume method. Applying this model, the coupled effect of gas diffusion, temperature and oxidation rate is studied, and the influence of water content on oxidation efficiency and capacity is quantified. The temporal variability of oxidation efficiency and capacity in landfill covers is illustrated by modelling a long-term field test. It is found that the CH4 removal rate can reach 40 g d−1 m−2 in the summers and drop to less than 10 g d−1 m−2 in the winters. A 3-D landfill cover cell with a cracked zone is applied to illustrate the spatial variability of oxidation, and a significant preferential flow can be observed when the cracked zone depth of a 1 m thick soil cover exceeds 0.8 m. The above studies demonstrate that the proposed model is able to predict temporal and spatial distributions of methane oxidation efficiency and capacity, and some results contribute to a better understanding of methane oxidation in landfill covers.

Selective Acetylene Adsorption within an Imino-Functionalized Nanocage-Based Metal-Organic Framework.

Removal of CH4 and CO2 from C2H2 streams remains challenging in the chemical industry. Herein, a robust three-dimensional metal-organic framework, Cu-CPAH, was designed and synthesized through a hydrothermal method. Cu-CPAH exhibits highly selective C2H2 adsorption capacity with respect to both CH4 and CO2, which is ascribed to the enrichment of active sites in the framework. Dynamic breakthrough results reveal that Cu-CPAH serves as a solid adsorbent for high-efficiency purification of C2H2 from an equal proportion of C2H2/CO2 or C2H2/CO2/CH4 at room temperature. Discrete Fourier transform simulations confirm that various active sites preferentially interact with C2H2 other than CO2 and CH4, signifying for the first time that the imino functional groups in the cage contribute greatly to the preferential affinity to C2H2 over CO2 and CH4.

Elucidating the influence of environmental factors on biogas-based polyhydroxybutyrate production by Methylocystis hirsuta CSC1

The valorization of biogas as a feedstock for the generation of added-value bioproducts will play a key role on the sustainability of anaerobic digestion. The present work assessed the influence of key environmental parameters (O2:CH4 ratio, temperature and nitrogen source) on the growth and polyhydroxybutyrate (PHB) synthesis under nitrogen limiting conditions of the type II methanotroph Methylocystis hirsuta CSC1 using biogas as a feedstock. The O2:CH4 ratios tested (1:1, 1.5:1 and 2:1) did not affect significantly M. hirsuta CSC1 growth yields (~5 g TSS mol−1 CH4), although lower CH4 removal rates were reached under O2-limiting conditions (ratio 1:1). The highest PHB content (45 wt%) was achieved at a ratio 2:1 and was threefold higher than those obtained at lower ratios (~15 wt%). The increase in temperature from 15 to 25 °C resulted in increases in the growth yield (from 5 to 6 g TSS mol−1 CH4) and PHB content (from 32 to 40 wt%). Conversely, the lowest PHB content (30 wt%) was reached at 37 °C, together with a negligible growth under nutrient sufficient conditions. The nitrogen source also played a key role on both M. hirsuta CSC1 growth and PHB synthesis. Thus, ammonium resulted in the highest growth yield (7 g TSS mol−1 CH4), although the maximum PHB content was achieved when biomass was previously grown in nitrate as the nitrogen source (41 wt%). Nitrite exerted an inhibitory effect on M. hirsuta CSC1 growth.

Moving from alcohol to methane biofilters: an experimental study on biofilter performance and carbon distribution

AbstractBACKGROUNDBiofilters can be used to eliminate different gaseous pollutants including alcohols (e.g. methanol, ethanol) and methane (CH4) individually or in a mixture. In this regard, the biofilter adaptability to feed composition variation is an industrial requisite. Inlet gas composition changes also give a better insight about carbon input and end‐points in biofilters. In this study, the gradual conversions of two biofilters from methanol and ethanol to CH4 were investigated.RESULTSBoth biofilters reached 100% removal efficiencies for the alcohols with no initial inoculation. Keeping the total inlet load constant (30 ± 1.3 g m−3 h−1), CH4 was progressively substituted in the feed with corresponding alcohol:CH4 mass ratios of 3:1, 1:1, 1:3 and 0 galcohol:gCH4. Maximum CH4 removal efficiencies of 52% and 29% were obtained (respectively) for biofilters started with methanol and ethanol. By moving from alcohols to CH4 biofilters, the gas phase output carbon increased from 273 to 666 gcarbon day−1 and from 377 to 681 gcarbon day−1 respectively for the methanol‐ and ethanol‐based biofilters.CONCLUSIONThis study showed a successful treatment based on inlet pollutant alteration from methanol or ethanol to CH4 in two separate biofilters. However, the methanol‐based biofilter displayed a better performance and a shorter acclimation time for CH4 conversion. © 2019 Society of Chemical Industry

Comparison of the methane-oxidizing capacity of landfill cover soil amended with biochar produced using different pyrolysis temperatures

The in-situ mitigation of methane (CH4) in landfill gas using landfill cover soil (LCS) is a cost-effective approach, but its efficiency needs to be enhanced. In this study, we incorporated an enriched methane-oxidizing bacteria (MOB) consortium into LCS and established four biochar-amended LCS groups with biochar produced at 300 °C (BC300), 400 °C (BC400), 500 °C (BC500), and 600 °C (BC600). The purpose was to evaluate the CH4 oxidation capacity of biochar-amended LCS after inoculation with MOB and to investigate how the physicochemical properties of biochar that are influenced by the pyrolysis temperature affect the performance and microbial activity of biochar-amended LCS. It was found that a 15% volume ratio (representing a mass ratio of 2.49%–2.78%) for biochar amendment in LCS enhanced CH4 removal efficiency, with the highest removal observed to be 46% for BC400-amended LCS compared to 30% for the original LCS. In addition, CH4 adsorption by the biochar was not observed, and a 15% mass ratio for biochar in the LCS had no or a negative impact. Besides improving the water-holding capacity and gas permeability of LCS, other possible advantages of biochar amendment in terms of CH4 oxidization include greater retention of nutrients, electron acceptors, and exchangeable cations, as well as introducing iron ions. It was also found that CH4 oxidation capacity and the methanotroph activity of biochar-amended LCS did not continue to increase with higher pyrolysis temperatures, even though higher micropore volumes and surface areas were obtained at higher pyrolysis temperatures. From this study, BC400 was identified as the optimal choice for the best performance in terms of enhancing both the CH4 oxidation capacity of the amended LCS and the growth of type II methanotroph Methylocystaceae, which can possibly be attributed to having the highest cation exchange capacity of the four biochars.

Methane decomposition and carbon deposition over Ni/ZrO2 catalysts: Comparison of amorphous, tetragonal, and monoclinic zirconia phase

The influence of crystal phase of ZrO2 on the catalytic performance of methane decomposition and the properties of deposited carbon on Ni/ZrO2 catalysts was investigated. Ni/ZrO2 catalysts were prepared by incipient-wetness impregnation method with 5% Ni loading, using amorphous, monoclinic, and tetragonal ZrO2 as supports. It was found that Ni/am-ZrO2 exhibited high activity and superior stability for carbon dioxide reforming of methane during 50 h of TOS, which could be attributed to the smaller Ni particle size and the lower coking rate. Additionally, the results of O2-TPO/TPH/CO2-TPO showed that the nature of carbon deposition via CH4 decomposition on Ni/ZrO2 catalysts was strongly influenced by both the Ni particle size and the crystal phase of zirconia. The lowest coking rate on Ni/am-ZrO2 for carbon dioxide reforming of methane was due to the lower CH4 decomposition rate and the higher gasification rate of carbon species by CO2. Carbon deposited on Ni/am-ZrO2 could be greatly removed by CO2, due to the presence of large amount of adsorbed oxygen species on the surface of amorphous ZrO2. For comparison, the imbalance of CH4 cracking and removal of coke by CO2 resulted in the accumulation of coke, leading to the deactivation of catalysts.

Experimental and numerical evaluation of CBM potential in Jharia Coalfield India

Geophysico-mechanical characterization of coal data are important in the economic success of CH4 extraction as well as a CO2 injection in deep coal seam reservoir. The heterogeneous nature of coal makes the CH4 removal quite challenging because of the complex behaviour of the seam at in situ as well as applied stress level. Coal matrix behaviour depends on several parameters as permeability, porosity, pore pressure, gas content, structural features, etc. plays a leading role in methane extraction. Therefore, extensive laboratory investigation is handiest approached to anticipate the behavior of coal effectively. This paper presents the results of coal characterization, gas permeability, adsorption/desorption capacity of coal as well as the performance of CBM production well in the replicated model of JH-MD-XVI-T coal seam at a depth of 580 m. The coal characterization was determined to evaluate the prospects of methane in the study area. The gas permeability was determined in a triaxial experimental set up using Darcy’s approach to in situ conditions. The decrease in permeability with an increase in confining as well as gas pressure was observed in all coal samples due to the crushing of grain, coal deformation and narrowing of fractures as well as cleats leading to hinder the flow of fluid through it. The well performance was evaluated to determine the gas rate as well as cumulative gas volume over twenty-five years of well life. Mutual relation between permeability, in situ confining pressure as well as gas pressure, has been established statistically.

Integrated biological–physical process for biogas purification effluent treatment

Biogas purification via water scrubbing produces effluent containing dissolved CH4, H2S, and CO2, which should be removed to reduce greenhouse gas emissions and increase its potential for water regeneration. In this study, a reactor built with air supplies at the top and bottom was utilized for the treatment of biogas purification effluent through biological oxidation and physical stripping processes. Up to 98% of CH4 was removed through biological treatment at a hydraulic retention time of 2 hr and an upper airflow rate of 2.02 L/day. Additionally, a minimum CH4 concentration of 0.04% with no trace of H2S gas was detected in the off gas. Meanwhile, a white precipitate was captured on the carrier showing the formation of sulfur. According to the developed mathematical model, an upper airflow rate of greater than 2.02 L/day showed a small deterioration in CH4 removal performance after reaching the maximum value, whereas a 50 L/day bottom airflow rate was required to strip the CO2 efficiently and raise the effluent pH from 5.64 to 7.3. Microbiological analysis confirmed the presence of type 1 methanotroph communities dominated by Methylobacter and Methylocaldum. However, bacterial communities promoting sulfide oxidation were dominated by Hyphomicrobium.