Methane Biodegradation Research Articles

Simultaneous biodegradation of methane and styrene in biofilters packed with inorganic supports: Experimental and macrokinetic study

Four upflow 0.018 m3 biofilters (3 beds), B-ME, B-200, B-500 and B-700, all packed with inorganic materials, were operated at a constant air flow rate of 0.18 m3 h−1 to eliminate methane (CH4), a harmful greenhouse gas (GHG), and styrene (C8H8), a carcinogenic volatile organic compound (VOC). The biofilters were irrigated with 0.001 m3 of recycled nutrient solution (NS) every day (flow rate of 60 × 10−3 m3 h−1). Styrene inlet load (IL) was kept constant in each biofilter. Different CH4-ILs varying in the range of 7–60 gCH4 m−3 h−1 were examined in B-ME (IL of 0 gC8H8 m−3 h−1), B-200 (IL of 9 gC8H8 m−3 h−1), B-500 (IL of 22 gC8H8 m−3 h−1) and B-700 (IL of 32 gC8H8 m−3 h−1). Finally, the effect of C8H8 on the macrokinetic parameters of CH4 biofiltration was studied based on the Michaelis-Menten model. Average C8H8 removal efficiencies (RE) varying between 64 and 100% were obtained at CH4-ILs increasing from 7 to 60 gCH4 m−3 h−1 and for C8H8-ILs range of 0–32 gC8H8 m−3 h−1. More than 90% of C8H8 was removed in the bottom and middle beds of the biofilters. By increasing C8H8-IL from 0 to 32 gC8H8 m−3 h−1, maximal EC in Michaelis-Menten model and macrokinetic saturation constant declined from 311 to 39 g m−3 h−1 and from 19 to 2.3 g m−3, respectively, which confirmed that an uncompetitive inhibition occurred during CH4 biofiltration in the presence of C8H8.

Methane biodegradation and enhanced methane solubilization by the filamentous fungi Fusarium solani.

Methane is one of the most important greenhouse gases emitted from natural and human activities. It is scarcely soluble in water; thus, it has a low bioavailability for microorganisms able to degrade it. In this work, the capacity of the fungus Fusarium solani to improve the solubility of methane in water and to biodegrade methane was assayed. Experiments were performed in microcosms with vermiculite as solid support and mineral media, at temperatures between 20 and 35 °C and water activities between 0.9 and 0.95, using pure cultures of F. solani and a methanotrophic consortium (Methylomicrobium album and Methylocystis sp) as a control. Methane was the only carbon and energy source. Results indicate that using thermally inactivated biomass of F. solani, decreases the partition coefficient of methane in water up to two orders of magnitude. Moreover, F. solani can degrade methane, in fact at 35 °C and the highest water activity, the methane degradation rate attained by F. solani was 300 mg m−3 h−1, identical to the biodegradation rate achieved by the consortium of methanotrophic bacteria.

A systematic comparison of two empirical gas-liquid mass transfer determination methodologies to characterize methane biodegradation in stirred tank bioreactors

This study aimed at systematically comparing the potential of two empirical methods for the estimation of the volumetric CH4 mass transfer coefficient (klaCH4), namely gassing-out and oxygen transfer rate (OTR), to describe CH4 biodegradation in a fermenter operated with a methanotrophic consortium at 400, 600 and 800 rpm. The klaCH4 estimated from the OTR methodology accurately predicted the CH4 elimination capacity (EC) under CH4 mass transfer limiting conditions regardless of the stirring rate (∼9% of average error between empirical and estimated ECs). Thus, empirical CH4-ECs of 37.8 ± 5.8, 42.5 ± 5.4 and 62.3 ± 5.2 g CH4 m−3 h−1vs predicted CH4-ECs of 35.6 ± 2.2, 50.1 ± 2.3 and 59.6 ± 3.4 g CH4 m−3 h−1 were recorded at 400, 600 and 800 rpm, respectively. The rapid Co2+-catalyzed reaction of O2 with SO3−2 in the vicinity of the gas-liquid interphase during OTR determinations, mimicking microbial CH4 uptake in the biotic experiments, was central to accurately describe the klaCH4.

Kinetics of type I methanotrophs mixed culture enriched from waste activated sludge

Methanotrophs are unique microorganisms that can upgrade the methane produced within wastewater treatment plants into diverse prominent commodities. The determination of the methanotrophic enrichments growth kinetics is a pivotal milestone to develop any methane based biotechnology. In this study, diversified batch incubations were performed to experimentally obtain, for the first time, the microbial growth kinetics for type I methanotrophs enriched from waste activated sludge. The key genus in the enriched culture includes Methylococcus, Methylobacter, Methaylocaldum, Methylomicrobium, Methylomonas, Methylosarcina, Methylosphaera. The attained maximum specific growth rate (μmax) (0.358 h−1) and maximum specific methane biodegradation rate (qmax) (g-CH4,Total g-DCW−1 h−1) were the highest reported in mixed cultures. Furthermore, the low substrate threshold concentration (Smin) (0.033 mg-CH4,aq./hr) observed shows that the microbial activity can be maintained at a very low methane aqueous concentrations. The obtained kinetic parameters confirm the prominence of utilizing type I methanotrophs mixed cultures in resources recovery processes from waste streams.

Evidence of Sulfate-Dependent Anaerobic Methane Oxidation within an Area Impacted by Coalbed Methane-Related Gas Migration.

We evaluated water quality characteristics in the northern Raton Basin of Colorado and documented the response of the Poison Canyon aquifer system several years after upward migration of methane gas occurred from the deeper Vermejo Formation coalbed production zone. Results show persistent secondary water quality impacts related to the biodegradation of methane. We identify four distinct characteristics of groundwater-methane attenuation in the Poison Canyon aquifer: (i) consumption of methane and sulfate and production of sulfide and bicarbonate, (ii) methane loss coupled to production of higher molecular weight (C2+) gaseous hydrocarbons, (iii) patterns of 13C enrichment and depletion in methane and dissolved inorganic carbon, and (iv) a systematic shift in sulfur and oxygen isotope ratios of sulfate, indicative of microbial sulfate reduction. We also show that the biogeochemical response of the aquifer system has not mobilized naturally occurring trace metals, including arsenic, chromium, cobalt, nickel, and lead, likely due to the microbial production of hydrogen sulfide which favors stabilization of metals in aquifer solids.

Assessment of methane biodegradation kinetics in two-phase partitioning bioreactors by pulse respirometry

Biological methane biodegradation is a promising treatment alternative when the methane produced in waste management facilities cannot be used for energy generation. Two-phase partitioning bioreactors (TPPBs), provided with a non-aqueous phase (NAP) with high affinity for the target pollutant, are particularly suitable for the treatment of poorly water-soluble compounds such as methane. Nevertheless, little is known about the influence of the presence of the NAP on the resulting biodegradation kinetics in TPPBs. In this study, an experimental framework based on the in situ pulse respirometry technique was developed to assess the impact of NAP addition on the methane biodegradation kinetics using Methylosinus sporium as a model methane-degrading microorganism. A comprehensive mass transfer characterization was performed in order to avoid mass transfer limiting scenarios and ensure a correct kinetic parameter characterization. The presence of the NAP mediated significant changes in the apparent kinetic parameters of M. sporium during methane biodegradation, with variations of 60, 120, and 150% in the maximum oxygen uptake rate, half-saturation constant and maximum specific growth rate, respectively, compared with the intrinsic kinetic parameters retrieved from a control without NAP. These significant changes in the kinetic parameters mediated by the NAP must be considered for the design, operation and modeling of TPPBs devoted to air pollution control.

Evaluation of simultaneous biodegradation of methane and toluene in landfill covers

The biodegradation of CH4 and toluene in landfill cover soil (LCS) and waste biocover soil (WBS) was investigated with a serial toluene concentration in the headspace of landfill cover microcosms in this study. Compared with the LCS sample, the higher CH4 oxidation activity and toluene-degrading capacity occurred in the WBS sample. The co-existence of toluene in landfill gas would positively or negatively affect CH4 oxidation, mainly depending on the toluene concentrations and exposure time. The nearly complete inhibition of toluene on CH4 oxidation was observed in the WBS sample at the toluene concentration of ∼80,000mgm−3, which was about 10 times higher than that in the LCS sample. The toluene degradation rates in both landfill covers fitted well with the Michaelis–Menten model. These findings showed that WBS was a good alternative landfill cover material to simultaneously mitigate emissions of CH4 and toluene from landfills to the atmosphere.

Numerical Model Investigation for Potential Methane Explosion and Benzene Vapor Intrusion Associated with High-Ethanol Blend Releases

Ethanol-blended fuel releases usually stimulate methanogenesis in the subsurface, which could pose an explosion risk if methane accumulates in a confined space above the ground where ignitable conditions exist. Ethanol-derived methane may also increase the vapor intrusion potential of toxic fuel hydrocarbons by stimulating the depletion of oxygen by methanotrophs, and thus inhibiting aerobic biodegradation of hydrocarbon vapors. To assess these processes, a three-dimensional numerical vapor intrusion model was used to simulate the degradation, migration, and intrusion pathway of methane and benzene under different site conditions. Simulations show that methane is unlikely to build up to pose an explosion hazard (5% v/v) if diffusion is the only mass transport mechanism through the deeper vadose zone. However, if methanogenic activity near the source zone is sufficiently high to cause advective gas transport, then the methane indoor concentration may exceed the flammable threshold under simulated conditions. During subsurface migration, methane biodegradation could consume soil oxygen that would otherwise be available to support hydrocarbon degradation, and increase the vapor intrusion potential for benzene. Vapor intrusion would also be exacerbated if methanogenic activity results in sufficiently high pressure to cause advective gas transport in the unsaturated zone. Overall, our simulations show that current approaches to manage the vapor intrusion risk for conventional fuel released might need to be modified when dealing with some high ethanol blend fuel (i.e., E20 up to E95) releases.

Kinetics of simultaneous methane and toluene biofiltration in an inert packed bed

AbstractBACKGROUNDBiofiltration of methane is of particular interest to contribute to limiting the greenhouse gas effect of biogas emissions from landfills. The complexity of the biogas mixture from landfills has underlined the importance of the presence of non‐methane organic compounds. The aim of this study was to determine the effect of toluene on the microkinetic and macrokinetic parameters of methane biodegradation using an inorganic filter bed.RESULTSTwo concentrations of toluene were tested, 0.7 and 3.4 gC m−3, and compared with the case of methane biofiltration alone. The specific growth rates of methane decreased from 0.793 to 0.574 to 0.278 d−1 when the toluene concentration was increased from 0 to 0.7 to 3.4 gC m−3, respectively. The maximum elimination capacity of methane decreased from 39.4 to 5.6 gC m−3 h−1 when toluene concentration was increased from 0 to 3.4 gC m−3. The half‐saturation constants decreased from 4.6 to 1.6 gC m−3 and from 4.6 to 0.7 gC m−3, respectively.CONCLUSIONSResults show that an inhibition occurred on methane biodegradation when toluene was introduced into the biofilter. © 2013 Society of Chemical Industry

Characterization of Methylocystis strain JTA1 isolated from aged refuse and its tolerance to chloroform

To accelerate the efficiency of methane biodegradation in landfills, a Gram-negative, rod-shaped, non-motile, non-spore-forming bacterium, JTA1, which can utilize methane as well as acetate, was isolated from the Laogang MSW landfills, Shanghai, China. Strain JTA1 was a member of genus Methylocystis on the basis of 16S rRNA and pmoA gene sequence similarity. The maximum specific cell growth rates (μmax= 0.042 hr−1, R2= 0.995) was derived through Boltzmann simulation, and the apparent half-saturation constants (Km(app) = 7.08 mmol/L, R2 = 0.982) was calculated according to Michaelis-Menton hyperbolic model, indicating that Methylocystis strain JTA1 had higher-affinity potential for methane oxidation than other reported methanotrophs. By way of adding the strain JTA1 culture, the methane consumption of aged refuse reached 115 mL, almost two times of control experiment. In addition, high tolerance of Methylocystis strain JTA1 to chloroform could facilitate the methane oxidation of aged refuse bio-covers. At the chloroform concentration of 50 mg/L, the methane-oxidation rate of bio-cover reached 0.114 mL/(day·g), much higher than the highest rate, 0.0135 mL/(day·g), of reported bio-covers. In conclusion, strain JTA1 opens up a new possibility for environmental biotechnology, such as soil or landfills bioremediation and wastewater decontamination.

Biodegradation of methane, benzene, and toluene by a consortium MBT14 enriched from a landfill cover soil

In this study, landfill cover soil was used as an inoculum source to enrich a methane, benzene, and toluene-degrading consortium MBT14. Under a single substrate, the maximum degradation rates of methane, benzene and toluene were 1.96, 0.15, and 0.77 mmole g-DCW−1 h−1, respectively. Although the coexistence of benzene and toluene inhibited the methane degradation rates, the consortium was able to simultaneously degrade methane, benzene and toluene. Methane had an insignificant effect on benzene or toluene degradation. Based on 16S rDNA sequencing analysis, Cupriavidus spp. are dominant in the consortium MBT14. The combined results of this study indicate that the consortium MBT 14 is a promising bioresource for removing CH4, benzene, and toluene from a variety of environments.

Effect of ammonium concentration on microbial population and performance of a biofilter treating air polluted with methane

The effect of ammonium concentration on the microbial population and performance of a biofilter operated at methane concentrations of 0.3% (v/v) was studied. In a range of ammonium concentration from 0.05 to 0.5 gN-NH 4 +/L, the removal efficiency, carbon dioxide production rate, biomass production, ammonium conversion and nitrate production rate were determined. The middle biofilter section microbial population was analyzed using denaturing gradient gel electrophoresis (DGGE). DNA sequence analysis revealed that the bacteria colonizing the middle biofilter section belonged essentially to 4 physiological groups: methanotrophs, methylotrophs, nitrifying and denitrifying bacteria. Ammonium concentration affected the presence of bacteria from each group and the interactions among them defined the biofilter performance. In the range of ammonium concentrations tested, the methane removal efficiency decreased from 70 to 13%, the carbon dioxide production rate from 25 to 7.5 g/(m 3 h), and the mean of dry biomass content in the packed bed from 12.8 to 6.7 g biomass/kg filter bed. The nitrate production rate increased with ammonium concentration; however, it presented negative values at nitrate concentrations around 0.5 gN/L. This suggests that denitrification occurred due to favourable conditions for the growth of denitrifiers. An analysis of methane biodegradation at different layers of the biofilter shows that the methanotrophic and nitrifying activities were more important in the upper section of the biofilter.

Production of poly-β-hydroxybutyrate (PHB) by Methylobacterium organophilum isolated from a methanotrophic consortium in a two-phase partition bioreactor

The biodegradation of methane, a greenhouse gas, and the accumulation of poly-β-hydroxybutyrate (PHB) were studied using a methanotrophic consortium and an isolated strain thereof. The specific rates for methane consumption were 100 and 17 m g C H 4 g x − 1 h − 1 for the isolate and the consortium, respectively. Also the effect of including 10% (v v −1) of silicone oil in a two-phase partitioning bioreactor (TPPB) was assayed for the elimination of 1% methane in air stream. TPPB allowed a 33–45% increase of methane elimination under growing conditions. Nitrogen limitation was assayed in bioreactors to promote PHB production. Under this condition, the specific methane degradation rate remained unchanged for the consortium and decreased to 36 m g C H 4 g x − 1 h − 1 for the isolated strain. The accumulated PHB in the reactor was 34% and 38% (w w −1) for the consortium and the isolate, respectively. The highest productivity was obtained in the TPPB and was 1 .61 m g PHB g x − 1 h − 1 . The CZ-2 isolate was identified as Methylobacterium organophilum, this is the first study that reports this species as being able to grow on methane and accumulate up to 57% (w w −1) of PHB under nitrogen limitation in microcosm experiments.

Methane biodegradation in a two‐phase partition internal loop airlift reactor with gas recirculation

AbstractBACKGROUND: The potential of organic liquid solvents and solid polymers to enhance CH4 mass transfer was studied in a two‐phase partition internal loop airlift reactor operated with gas recirculation under biotic and abiotic conditions. A preliminary screening of the most common liquid solvents (silicone oil 20 cSt, silicone oil 200 cSt and 2,2,4,4,6,8,8‐heptametilnonane) and solid polymers (Kraton® G6157, Desmopan® DP9370A and Elvax® 880) resulted in the selection of silicone oil 200 cSt (S200) and Desmopan DP9370A (D9370) for further investigation based on their high affinity for CH4, biocompatibility and nonbiodegradability.RESULTS: Under abiotic conditions, the increase in gas recirculation from 0 to 1 vvm in the absence of a transfer vector increased the overall mass transfer coefficient for oxygen (kLa) by 195%. The presence of S200 and D9370 at 10% (v/v) under operation at 1 vvm of gas recirculation rate mediated an increase in kLa of 100% and 136%, respectively. Likewise, the increase in gas recirculation from 0 to 1 vvm in the absence of a transfer vector and in the presence of S200 during the continuous biodegradation of methane at 3% (v/v) and 7.3 min empty bed residence time resulted in increases in CH4 removal and CO2 production rates of 47% and 36%, respectively. Nevertheless, no significant enhancement in CH4 removal due to the presence of 10% of Desmopan or silicone oil was recorded under operation at 1 vvm.CONCLUSIONS: These results suggest that microbial activity rather than mass transport could be the limiting step in biological CH4 abatement in this system, contrary to that observed in previous studies with stirred tank reactors, where the organic phase addition increased methane biodegradation. Copyright © 2010 Society of Chemical Industry

Effect of silicone oil fraction and stirring rate on methane degradation in a stirred tank reactor

AbstractBACKGROUND: Methane is an important greenhouse gas and its biological oxidation constitutes a cost‐effective alternative for low concentration emissions. Nevertheless, due to its low aqueous solubility (similar to oxygen), gas mass transfer is often the limiting step. Two‐phase partition bioreactors (TPPBs), have been proposed to increase the biodegradation of poorly soluble compounds. In this work, the effect of stirring rate and silicone oil fraction on abiotic volumetric oxygen transfer coefficient kLa and methane elimination capacity (EC) by a methanotrophic consortium in a stirred tank was studied.RESULTS: In abiotic conditions, the kLa increased when increasing both factors. Nevertheless, a negative effect on kLa was observed with silicone oil at the highest stirring rate (800 rpm). During methane biodegradation experiments, EC also improved when increasing both factors, but contrary to abiotic kLa, it was not affected at the highest stirring rate. While stirring rate was the dominant variable determining methane biodegradation, the effect of oil fraction was only significant above 200 rpm. A maximum EC improvement of 700% was observed when increasing stirring rate from 200 to 800 rpm with 10% of silicone oil.CONCLUSIONS: Increasing both stirring rate and oil fraction enhanced EC. The results were different from those observed with kLa suggesting that kLa is not sufficient to describe properly the mass transfer in TPPB because other factors (interfacial contact between the phases and physicochemical properties of organic phase) should be considered. Copyright © 2010 Society of Chemical Industry

Biodegradation of Methane and Halocarbons in Simulated Landfill Biocover Systems Containing Compost Materials

The attenuation potential of methane (CH(4)) and of selected volatile organic compounds (VOCs) was compared in four types of compost materials using dynamic flow column experiments over a period of 255 d. Garden waste compost mixed with wood chips showed the highest steady-state CH(4) oxidation rate (161 g m(-2) d(-1)), followed by a commercial compost product Supermuld (110 g m(-2) d(-1)). In the column containing the highest fraction of compost (compost/sand mixed in 1:1), CH(4) oxidation declined significantly during the period of operation, probably due to clogging by formation of exopolymeric substances. After 40 d of operation, CH(4) production was observed. All the VOCs tested were degraded. CFC-11 (CCl(3)F) and HCFC-21 (CCl(2)FH) were anaerobically degraded by reductive dechlorination, generating HCFC-31 (CClFH(2)) and HFC-41 (CFH(3)), which were both aerobically degraded in the oxic portion of the columns. Overall, the highest removal of VOCs was observed in the column containing the compost/wood chip mixture. This study demonstrates that biocovers consisting of compost materials have the potential to attenuate trace gas emissions from landfills.

Analysis of methane biodegradation by Methylosinus trichosporium OB3b

Analysis of methane biodegradation by Methylosinus trichosporium OB3b

Analysis of methane biodegradation by Methylosinus trichosporium OB3b.

The microbial oxidation of methane in the atmosphere is performed by methanotrophic bacteria that use methane as a unique source of carbon and energy. The objective of this work consisted of the investigation of the best conditions of methane biodegradation by methanotrophic bacteria Methylosinus trichosporium OB3b that oxidize it to carbon dioxide, and the use of these microorganisms in monitoring methods for methane. The results showed that M. trichosporium OB3b was capable to degrade methane in a more effective way with an initial microorganism concentration of 0.0700 g.L-1, temperature of 30ºC, pH 6.5 and using 1.79 mmol of methane. In these same conditions, there was no bacterial growth when 2.69 mmol of methane was used. The specific rate of microorganism growth, the conversion factor, the efficiency and the volumetric productivity, for the optimized conditions of biodegradation were, respectively, 0.0324 h-1, 0.6830 gcells/gCH4, 73.73% and 2.7732.10-3 gcells/L.h. The final product of methane microbiological degradation, carbon dioxide, was quantified through the use of a commercial electrode, and, through this, the grade of methane conversion in carbon dioxide was calculated.

Elimination of methane generated from landfills by biofiltration: a review

The production of biogas in landfills, its composition and the problems resulting from its generation are all reviewed. Biofiltration is a promising option for the control of emissions to atmosphere of the methane contained in biogas issued from the smaller and/or older landfills. A detailed review of the methane biofiltration literature is presented. The microorganisms, mainly the methanotrophs, involved in the methane biodegradation process, and their needs in terms of oxygen and carbon dioxide utilization, are described. Moreover, the influence of nutrients such as copper, nitrogen and phosphorus, and the process operating conditions such as temperature, pH and moisture content of the biofilter bed, are also presented. Finally, the performance of various filter beds, in terms of their elimination capacities, is presented for laboratory scale biofilters and landfill covers.

Methanotrophic biodegradation of cis-1,2-dichloroethylene in a continuously fed fixed-film bioreactor

Co-metabolic biodegradation of cis-dichloroethylene (cis-DCE) was investigated in a bench-scale fixed-film bioreactor inoculated with a mixed culture of methane oxidising bacteria. The aim of this work was to identify factors that affect the cis-DCE biodegradation. It was observed that the presence of methane was necessary to enhance the biodegradation of cis-DCE, but an excess of methane inhibited the cis-DCE removal. cis-DCE did not inhibit the methane biodegradation at concentrations up to 300 microg/L. Maximum cis-DCE removal was observed with a methane bulk concentration ranging from 0.2 to 0.7 mg/L. It was found that the activity of the biofilm was located in the upper 100 microm of the biofilm. On the basis of this study it is concluded that careful control of the oxygen and methane concentrations as well as of the biofilm thickness is necessary in order to optimise the biodegradation of cis-DCE in fixed film bioreactors.