Simultaneous Production Of Methane Research Articles

Simultaneously enhancement of methane production and active phosphorus transformation by sludge-based biochar during high solids anaerobic co-digestion of dewatered sludge and food waste: Performance and mechanism

Biochar has been proved to improve methane production in high solids anaerobic co-digestion (HS-AcoD) of dewatered sludge (DS) and food waste (FW), but its potential mechanism for simultaneous methane production and phosphorus (P) transformation has not been sufficiently revealed. Results showed that the optimal preparation temperature and dosage of sludge-based biochar were selected as 300 °C and 0.075 g·g−1, respectively. Under this optimized condition, the methane production of the semi-continuous reactor increased by 54%, and the active phosphorus increased by 18%. The functional microorganisms, such as Methanosarcina, hydrogen-producing, sulfate-reducing, and iron-reducing bacteria, were increased. Metabolic pathways associated with sulfate reduction and methanogenesis, especially hydrogenotrophic methanogenesis, were enhanced, which in turn promoted methanogenesis and phosphorus transformation and release. This study provides theoretical support for simultaneously recovery of carbon and phosphorus resources from DS and FW using biochar.

Fe-doped hydrochar facilitating simultaneous methane production and pharmaceutical and personal care products (PPCPs) degradation in co-anaerobic digestion of municipal sludge and food waste

Fe-doped hydrochar facilitating simultaneous methane production and pharmaceutical and personal care products (PPCPs) degradation in co-anaerobic digestion of municipal sludge and food waste

Enrichment of homoacetogens converting H2/CO2 into acids and ethanol and simultaneous methane production.

An anaerobic granular sludge was enriched to utilize H2/CO2 in a continuous gas-fed up-flow anaerobic sludge reactor by applying operating conditions expected to produce acetic acid, butyric acid, and ethanol. Three stages of fermentation were found: Stage I with acetic acid accumulation with the highest concentration of 35mM along with a pH decrease from initial 6 to 4.5. In Stage II, H2/CO2 was replaced by 100% H2 to induce solventogenesis, whereas butyric acid was produced with the highest concentration of 2.5mM. At stage III with 10 µM tungsten (W) addition, iso-valeric acid, valeric acid, and caproic acid were produced at pH 4.5-5.0. In the batch tests inoculated with the enriched sludge taken from the bioreactor (day 70), however, methane production occurred at pH 6. Exogenous 15mM acetate addition enhanced both the H2 and CO2 consumption rate compared to exogenous 10, 30, and 45mM acetate by the enriched sludge. Exogenous acetate was failed to be converted to ethanol using H2 as electron donor by the enriched acetogens.

Formula omitted] and [formula omitted] signatures of methane aerobically oxidized by Methylosinus trichosporium with implications for deciphering the provenance of methane gases

Aerobic oxidation of methane (MOx) is an important biologically mediated process that consumes methane in a wide range of environments. Here we report results of culture experiments with the aerobic methane-oxidizing bacterium Methylosinus trichosporium (OB3b) that are used to characterize the mass-18 isotopologue (Δ13CH3D and Δ12CH2D2) signatures of MOx in residual methane gases. MOx activity was confirmed by simultaneous decrease of methane and oxygen in the bulk gas headspace. Bulk carbon (13C/12C) and hydrogen (D/H) isotope ratios of the methane gas increased while both Δ13CH3D and Δ12CH2D2 decreased as the oxidation proceeded. The corresponding fractionation factors (α) calculated from our experimental results are 0.98485 ± 0.00006 for 13C/12C, 0.7265 ± 0.0010 for D/H, 0.7141 ± 0.0011 for 13CH3D/12CH4, and 0.4757 ± 0.0023 for 12CH2D2/12CH4. Deviations of the mass-18 fractionation factors from the Rule of the Geometric Mean (RGM) expressed as γ values are 0.9981 ± 0.0017 for 13CH3D/12CH4 and 0.9013 ± 0.0045 for 12CH2D2/12CH4. Our α and γ values suggest that while MOx fractionates 13CH3D within error of the RGM, the Δ13CH3D and Δ12CH2D2 trajectories are very sensitive to even small deviations in 13CH3D/12CH4 from the RGM. Fractionation of 12CH2D2 deviates considerably from RGM, and this causes dramatic and robust effects on the trajectories of residual methane in Δ13CH3D vs. Δ12CH2D2 space. Our models suggest that Δ13CH3D and Δ12CH2D2 could potentially mimic microbial methanogenesis signatures in an environment that exhibits a strong Rayleigh Distillation process with little to no replenishment of methane during oxidation. However, in closed or open systems where oxidation is attended by simultaneous methane production, we find that modest increases in Δ13CH3D and dramatic increases in Δ12CH2D2 are to be expected, thus resulting in isotopologue signatures distinct from microbial methanogenesis. The overall trend in these conditions suggest that methane altered by MOx is distinguishable from other methane sources in Δ13CH3D and Δ12CH2D2 space.

Anaerobic co-digestion of dissolved air floatation slurry and selenium rich wastewater for simultaneous methane production and selenium bioremediation

The energy potential of dissolved air floatation (DAF) slurry, a lipid-rich waste, is largely disregarded with the common practice of land spreading or landfilling. On the other hand, selenium (Se) contaminated wastewaters are perceived as unsuitable feedstocks because of their toxicity. This study aimed to evaluate the anaerobic co-digestion performance of a DAF slurry with Se rich wastewater using anaerobic granular sludge and waste activated sludge as the inocula. Anaerobic batch assays of DAF slurry supplemented with 0.05, 0.10, 0.25 and 0.50 mM selenate (SeO42−) and selenite (SeO32−), along with a control (without Se) were performed at 30 °C. Methanogenesis of the DAF slurry using anaerobic granular sludge was realised during co-digestion up to 0.50 mM SeO42−, whereas SeO32− was already toxic from 0.05 mM onwards. Co-digestion of the DAF slurry with 0.05 and 0.10 mM Se oxyanions (both selenate and selenite) containing wastewater using waste activated sludge achieved a similar cumulative methane yield of about 180 mL/g COD as that of mono-digestion (Se free DAF slurry) after 65 days of incubation. Simultaneously, more than 90% removal of Se was accomplished. The lag phase duration was, however, extended by 50 and 90% in the presence of 0.05 and 0.10 mM Se, respectively. The half maximal inhibitory concentration (IC50) for methane production using waste activated sludge was 0.08 mM for SeO42− and 0.07 mM for SeO32−. The IC50 amounted to 2.10 mM for SeO42− and 0.08 mM for SeO32− with anaerobic granular sludge. SeO42− and SeO32− were reduced to elemental Se nanoparticles, as shown by transmission electron microscopy. This study indicates the feasibility of methane production from a DAF slurry, codigested with wastewaters containing up to 0.10 mM SeO42− or SeO32−.

The impact of aerobic pretreatment of agro and industrial wastes on their biomethanation potential in Nisargruna technology

Anaerobic digestion is among the essential biological techniques used for stabilization of organic sludge from sewage and highly concentrated efflu-ents from food processing industries. It also recycles the municipal solid wastes into compost with simultaneous production of methane. The current study was performed to estimate the biomethanation potential of various agro- and industrial wastes like Jatropha de-oil cake, prawn shells, chicken feathers, bagasse, rice straw and wheat husk by mimicking the conditions in the biphasic Nisargruna biogas plant. A small volume of samples was chemi-cally characterized and allowed to decompose under aerobic and anaerobic conditions to determine the effect of aerobic predigestion (i.e. phase 1 of Nisargruna plant) on final methane production. The biogas produced was quantified by downward displacement of water. The observations indicated that approximately 60-80% methane was produced when Jatropha de-oil cake, prawn shells and rice straw was used. Conversely, the wheat straw and sugarcane wastes showed less methane formation, which may be due to the presence of complex polymers like lignocellulose and silica that considerably reduces the metabolic potential of microorganisms.

Dynamic changes in anaerobic digester metabolic pathways and microbial populations during acclimatisation to increasing ammonium concentrations

Transitions in microbial community structure in response to increasing ammonia concentrations were determined by monitoring mesophilic anaerobic digesters seeded with a predominantly acetoclastic methanogenic community from a sewage sludge digester. Ammonia concentration was raised by switching the feed to source segregated domestic food waste and applying two organic loading rates (OLR) and hydraulic retention times (HRT) in paired digesters. One of each pair was dosed with trace elements (TE) known to be essential to the transition, with the other unsupplemented digester acting as a control. Samples taken during the trial were used to determine the metabolic pathway to methanogenesis using 14C labelled acetate. Partitioning of 14C between the product gases was interpreted via an equation to indicate the proportion produced by acetoclastic and hydrogenotrophic routes. Archaeal and selected bacterial groups were identified by 16S rRNA sequencing, to determine relative abundance and diversity. Acclimatisation for digesters with TE was relatively smooth, but OLR and HRT influenced both metabolic route and community structure. The 14C ratio could be used quantitatively and, when interpreted alongside archaeal community structure, showed that at longer HRT and lower loading Methanobacteriaceae were dominant and hydrogenotrophic activity accounted for 77% of methane production. At the higher OLR and shorter HRT, Methanosarcinaceae were dominant with the 14C ratio indicating simultaneous production of methane by acetoclastic and hydrogenotrophic pathways: the first reported observation of this in digestion under mesophilic conditions. Digesters without TE supplementation showed similar initial changes but, as expected failed to complete the transition to stable operation.

The degradation and simultaneous influence of bisphenol A on methane production in a bio-anode single-chamber microbial electrolysis cell

The objective of this research was to estimate the effect of operational parameters on the performance of a bio-anode single-chamber microbial electrolysis cell (BSMEC) in degradation of bisphenol A (BPA) and simultaneous production of methane. To achieve this purpose, the influence of various parameters such as hydraulic retention time (HRT), applied voltage, C/N ratio and concentration of the BPA was examined on the performance of BSMEC during a 150-day period. According to the results, the BSMEC attained a BPA removal of 95.4%, a chemical oxygen demand (COD) removal rate of 94.9%, a methane production rate of 121.4 ± 2.2 mL/L.day and a methane content of 91.9% which were higher than these of the control system with 54.2%, 61.3% and 83.1 ± 2.2 mL/L.day and 71.1% respectively, at optimum condition (HRT=24 h, applied voltage=0.8 V, C/N ratio = 50 and BPA concentration = 10 mg/L). Our finding indicated that degradation of BPA, COD removal rate, methane production rate and methane content were improved as C/N ratio increased from 20 to 50. In the BSMEC, maximum energy efficiency was in the range of 93.1–96.8% with an average of 95.7%. As a result, the BSMEC is a promising alternative not only to degrade the endocrine disrupting compounds (EDCs) but also to generate the methane.

A Membrane-Bound Cytochrome Enables Methanosarcina acetivorans To Conserve Energy from Extracellular Electron Transfer.

Extracellular electron exchange in Methanosarcina species and closely related Archaea plays an important role in the global carbon cycle and enhances the speed and stability of anaerobic digestion by facilitating efficient syntrophic interactions. Here, we grew Methanosarcina acetivorans with methanol provided as the electron donor and the humic analogue, anthraquione-2,6-disulfonate (AQDS), provided as the electron acceptor when methane production was inhibited with bromoethanesulfonate. AQDS was reduced with simultaneous methane production in the absence of bromoethanesulfonate. Transcriptomics revealed that expression of the gene for the transmembrane, multiheme, c-type cytochrome MmcA was higher in AQDS-respiring cells than in cells performing methylotrophic methanogenesis. A strain in which the gene for MmcA was deleted failed to grow via AQDS reduction but grew with the conversion of methanol or acetate to methane, suggesting that MmcA has a specialized role as a conduit for extracellular electron transfer. Enhanced expression of genes for methanol conversion to methyl-coenzyme M and the Rnf complex suggested that methanol is oxidized to carbon dioxide in AQDS-respiring cells through a pathway that is similar to methyl-coenzyme M oxidation in methanogenic cells. However, during AQDS respiration the Rnf complex and reduced methanophenazine probably transfer electrons to MmcA, which functions as the terminal reductase for AQDS reduction. Extracellular electron transfer may enable the survival of methanogens in dynamic environments in which oxidized humic substances and Fe(III) oxides are intermittently available. The availability of tools for genetic manipulation of M. acetivorans makes it an excellent model microbe for evaluating c-type cytochrome-dependent extracellular electron transfer in ArchaeaIMPORTANCE The discovery of a methanogen that can conserve energy to support growth solely from the oxidation of organic carbon coupled to the reduction of an extracellular electron acceptor expands the possible environments in which methanogens might thrive. The potential importance of c-type cytochromes for extracellular electron transfer to syntrophic bacterial partners and/or Fe(III) minerals in some Archaea was previously proposed, but these studies with Methanosarcina acetivorans provide the first genetic evidence for cytochrome-based extracellular electron transfer in Archaea The results suggest parallels with Gram-negative bacteria, such as Shewanella and Geobacter species, in which multiheme outer-surface c-type cytochromes are an essential component for electrical communication with the extracellular environment. M. acetivorans offers an unprecedented opportunity to study mechanisms for energy conservation from the anaerobic oxidation of one-carbon organic compounds coupled to extracellular electron transfer in Archaea with implications not only for methanogens but possibly also for Archaea that anaerobically oxidize methane.

Simultaneous production of methane and acetate by thermophilic mixed culture from carbon dioxide in bioelectrochemical system

A thermophilic bioelectrochemical system was operated with mixed culture at 60 °C, while introducing only carbon dioxide. Methane production was initially observed in a membrane-less single chamber without a mediator, but eventually acetate was also found as 10.5 g/L after 137 days of operation. Comparing the microbial communities before and after the electricity supply using next-generation sequencing technology, acetoclastic methanogens such as Methanosaeta concilii were increased, and this result also indicates the production of acetate in bioelectrochemical CO2 conversion system. With the advent of sulfate-reducing bacteria, Desulfotomaculum peckii was considered to be an acetate production promoter. These high production results for both methane and acetate can be applied to CO2 storage using excess electricity for value-added chemicals.

Efficient methane production from petrochemical wastewater in a single membrane-less microbial electrolysis cell: the effect of the operational parameters in batch and continuous mode on bioenergy recovery.

The main objective of this study is to evaluate the treatment and simultaneous production of methane from low-strength petrochemical wastewater by single membrane-less microbial electrolysis cells. To achieve this objective, the influence of variables such as applied voltage, operation mode, and hydraulic retention time (HRT) on the performance of the MEC system was investigated over a period of 110days. According to the obtained results, the maximum COD removal efficiency in the batch mode was higher than which in the continuous mode (i.e. 85.9% vs 75.3%). However, the maximum methane production in the continuous mode was almost 1.6 times higher than which in the batch mode. The results show, COD removal, methane content, and methane production in both operation modes, were enhanced as applied voltage increased from 0.6 to 0.8-1V. The proportion of methane, methane production rate, and COD removal were increased as HRT decreased from 72 to 48h, while these values were decreased as the HRT decreased from 48 to 12h. In continues mode, the energy efficiency had a range of 94.7% to 97.9% with an average of 96.6% in phase III, which almost recovered all of the electrical energy input into the system. These results suggest that single membrane-less microbial electrolysis cell is a promising process in order to the treatment of low-strength wastewater and methane production.

Accelerated CO2 reduction to methane for energy by zero valent iron in oil reservoir production waters

We assessed the microbiological reduction of carbon dioxide into methane bioenergy through biochemical reaction by addition of zero valent iron (ZVI) as an alternative electron donor in oil reservoir production waters under strictly anaerobic conditions. Enhanced methane production was observed in all the treatments amended with ZVI compared with the controls. The outcome of the microbial community (Illumina Next Generation Sequencing) analysis indicated that CO2-reducing methanogens were closely related to Methanothermobacter spp. responsible for the production of methane. Moreover, the detection of FeCO3 in the culture medium amended with ZVI at the end of the experiment, characterized by X-ray Photoelectron Spectroscopy (XPS), indicated a potential CO2 transformation via mineralization under the investigation conditions with simultaneous methane production. This study offers an alternative strategy for carbon dioxide reduction into methane for energy and also a potential possibility for carbon dioxide reducing and subsequently clean bioenergy recovery in oil reservoirs.

Thermodynamic implications of adding N2 to CO2 for production of CH4 from hydrates

The huge resources of natural gas trapped in hydrate form are widely distributed worldwide in permafrost and offshore sediments. Pressure reduction and thermal stimulation have been dominating the research into production methods over the latest decades. More recently, a novel approach has emerged based on conversion of in situ methane hydrate to carbon dioxide-dominated hydrate through injection of carbon dioxide. This work applied the free energy analysis to determine whether addition of nitrogen into the injection mixture would result in a win-win situation of simultaneous methane production and safe long term storage of CO2. Our evaluation of data from two permafrost and two offshore fields indicates that injection of carbon dioxide at concentrations exceeding 50 mol % and pressures ranging between 9 and 25 MPa will result in formation of new carbon dioxide-dominated hydrate for all of these fields. While only reservoir simulations implementing reliable thermodynamic models can verify whether given injection will result in substantial storage of carbon dioxide in the form of hydrate, thermodynamic models developed in this work have their own significance. Pressure and temperature dependencies of hydrate stability have frequently been reported in studies of hydrates in sediments as the only criteria. Extending these criteria to include the concentration dependency will make it possible to implement an efficient free energy minimization scheme able to probe local phase distributions. Since one of four hydrate reservoirs used in our thermodynamic analysis is located in Alaska, we have also investigated the upper limit of water that can be tolerated during transport under extreme conditions prevailing the winter seasons in this region. It was found that hydrate formation triggered by water adsorbing on rusty surfaces will dominate the tolerance limit, which will correspond to practically zero water concentration.

Cathode material as an influencing factor on beer wastewater treatment and methane production in a novel integrated upflow microbial electrolysis cell (Upflow-MEC)

As a reliable source for methane production, the major goal of our research was to design and testify a novel microbial electrolysis assisted upflow anaerobic (Upflow-MEC) reactor for beer wastewater treatment and simultaneous methane production. Three reactors with different cathode materials were constructed and the reactor with Ni cathode had a maximum COD removal of 85%, methane yield of 142.8 mL/gCOD, TOC removal of 83%, Carbohydrate removal of 97%, Protein removal of 62% and current production of 8.6 mA, under 0.8 V applied voltage at HRT of 24 h. It was an application-oriented, membrane-free, continuous reactor and shortening the reaction time and increasing organic content conversion to methane were the key developing targets.

Simultaneous Production of Methane and Acetate from Carbon Dioxide with Bioelectrochemical Systems

Reduction of CO2 to organics with bioelectrical systems has become a research area of environmental microbiology.This study constructed a bioelectrochemical system(BES) capable of reducing CO2 to CH4 and CH3COOH via abiotical H2 gas production and/or direct extracellular electron transfer. CH4 and CH3COOH were produced at rates of 17.3 mL h-1L-1 and 13.9 mg h-1L-1, respectively(at potential of-1 100 mV). The current capture efficiency reached 94.0% in batch potentiostatic experiments. Microbial characterization revealed that the microbial populations consisted of Methanobacterium palustre,Methanocorpusculum parvum, and acetogen Acetobacterium sp. These results suggested that mixed culture in BESs can convert CO2 into various organic compounds by accepting electrons in different ways.

Simultaneous methane production and wastewater reuse by a membrane-based process: Evaluation with raw domestic wastewater

In this study, a membrane-based process was applied to simultaneously reclaim methane and generate reused water from raw domestic wastewater. The system was comprised of up-flow anaerobic sludge fixed bed (UAFB), anoxic sink (AS) and aerobic membrane bioreactor (MBR). The hydraulic retention time of UAFB (HRTU) was gradually shortened from 8h to 6h, 3h and to 1h, while the HRT of AS and MBR kept at 8h. It is found that HRTU of 3h was more suitable for the balancing production of biogas and volatile fatty acids (VFAs), and the VFAs served as carbon source for denitrification. The trans-membrane pressure (TMP) of the MBR kept lower than 0.04MPa without wash or change of membrane sheet, however, the scanning electron microscopy (SEM) analysis indicated that microbes attached to the inner-surface of membrane, causing irreversible fouling after 133-day operation. The denaturing gradient gel electrophoresis (DGGE) profiles of amplified 16S rDNA gene fragments proved that more functional bacteria and higher microbial diversity emerged at HRTU of 3h and 1h. Most bacteria belonged to Betaproteobacteria and were responsible for carbon and nitrogen removal.

Inhibitory effects of nitrogen oxides on a mixed methanogenic culture

The effect of nitrate, nitrite, nitric oxide (NO), and nitrous oxide on a mixed, mesophilic (35 degrees C) methanogenic culture was investigated. Short-term inhibition assays were conducted at a concentration range of 10-350 mg N/L nitrate, 17-500 mg N/L nitrite, 0.02-0.8 mg N/L aqueous NO, and 19-191 mg N/L aqueous nitrous oxide. Simultaneous methane production and N-oxide reduction was observed in 10 and 30 mg N/L nitrate and 0.02 mg N/L aqueous NO-amended cultures. However, addition of N-oxide resulted in immediate cessation of methanogenesis in all other cultures. Methanogenesis completely recovered subsequent to the complete reduction of N-oxides to nitrogen gas in all N-oxide-amended cultures, with the exception of the 500 mg N/L nitrite- and 0.8 mg N/L aqueous NO-amended cultures. Partial recovery of methanogenesis was observed in the 500 mg N/L nitrite-amended culture in contrast to complete inhibition of methanogenesis in the 0.8 mg N/L aqueous NO-amended culture. Accumulation of volatile fatty acids was observed in both cultures at the end of the incubation period. Among all N-oxides, NO exerted the most and nitrate exerted the least inhibitory effect on the fermentative/methanogenic consortia. The effect of multiple additions of nitrate (300 mg N/L) on the same methanogenic culture was also investigated. Long-term exposure of the methanogenic culture to nitrate resulted in an increase of N-oxide reduction rates and decrease of methane production rates, which was attributed to changes in the microbial community structure due to nitrate addition.

Thermophilic anaerobic fermentation of olive pulp for hydrogen and methane production: modelling of the anaerobic digestion process

The present study investigates the thermophilic biohydrogen and methane production from olive pulp, which is the semi-solid residue coming from the two-phase processing of olives. It focussed on: a) production of methane from the raw olive pulp; b) anaerobic bio-production of hydrogen from the olive pulp; c) subsequent anaerobic treatment of the hydrogen-effluent with the simultaneous production of methane; and d) development of a mathematical model able to describe the anaerobic digestion of the olive pulp and the effluent of hydrogen producing process. Both continuous and batch experiments were performed. The hydrogen potential of the olive pulp amounted to 1.6 mmole H2 per g TS. The methane potential of the raw olive pulp and hydrogen-effluent was as high as 19 mmole CH4 per g TS suggesting that: a) olive pulp is a suitable substrate for methane production; and b) biohydrogen production can be very efficiently coupled with a subsequent step for methane production.

Potential for biohydrogen and methane production from olive pulp

The present study investigates the potential for thermophilic biohydrogen and methane production from olive pulp, which is the semi-solid residue coming from the two-phase processing of olives. It focussed on: a) production of methane from the raw olive pulp, b) anaerobic bio-production of hydrogen from the olive pulp, and c) subsequent anaerobic treatment of the hydrogen-effluent with the simultaneous production of methane. Both continuous and batch experiments were performed. The hydrogen potential of the olive pulp amounted to 1.6 mmole H2 per g TS. The methane potential of the raw olive pulp and hydrogen-effluent was as high as 19 mmole CH4 per g TS. This suggests that olive pulp is an ideal substrate for methane production and it shows that biohydrogen production can be very efficiently coupled with a subsequent step for methane production.

End Products of Anaerobic Chitin Degradation by Salt Marsh Bacteria as Substrates for Dissimilatory Sulfate Reduction and Methanogenesis

The anaerobic pathway of chitin decomposition by chitinoclastic bacteria was examined with an emphasis on end product coupling to other salt marsh bacteria. Actively growing chitinoclastic bacterial isolates produced primarily acetate, H(2), and CO(2) in broth culture. No sulfate-reducing or methanogenic isolates grew on chitin as sole carbon source or produced any measurable degradation products. Mixed cultures of chitin degraders with sulfate reducers resulted in positive sulfide production. Mixed cultures of chitin-degrading isolates with methanogens resulted in the production of CH(4) with reductions in headspace CO(2) and H(2). The combination of all three metabolic types resulted in the simultaneous production of methane and sulfide, with more methane being produced in mixed cultures containing CO(2)-reducing methanogens and acetoclastic sulfate reducers because of less interspecific H(2) competition.