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This work proves the feasibility of employing regular secondary activated sludge for the enrichment of a microbial community able to perform the anaerobic oxidation of methane coupled to nitrate reduction (N-AOM). After 96 days of activated sludge enrichment, a clear N-AOM activity was observed in the resulting microbial community. The methane removal potential of the enriched N-AOM culture was then studied in a stirred tank reactor (STR) operated in continuous mode for methane supply and semi-continuous mode for the liquid phase. The effect of applying nitrate loads of ∼22, 44, 66, and 88 g NO 3 - m -3 on (i) STR methane and nitrate removal performance, (ii) N -1 O emission, and (iii) microbial composition was investigated. Methane elimination capacities from 21 ± 13.3 to 55 ± 12 g CH 2 O emission, and (iii) microbial composition was investigated. Methane elimination capacities from 21 ± 13.3 to 55 ± 12 g CH 4 m -3 were recorded, coupled to nitrate removal rates ranging from 6 ± 3.2 to 43 ± 14.9 g NO -1 were recorded, coupled to nitrate removal rates ranging from 6 ± 3.2 to 43 ± 14.9 g NO 3 - m -3 h -1 O emission in the continuous N-AOM process (i.e. ∼22-66 g NO 2 O production was not detected under the three nitrate loading rates applied for the assessment of potential N 2 O emission in the continuous N-AOM process (i.e. ∼22-66 g NO -3 m -3 h -1 ). The lack of N 2 O emissions during the process was attributed to the N 2 values ≤ 0.07 g m 2 and pH of 7.6 ± 0.4). Microbial characterization showed that the N-AOM process was performed in absence of putative N-AOM archaea and bacteria (ANME-2d, M. oxyfera). Instead, microbial activity was driven by methane-oxidizing bacteria and denitrifying bacteria (Bacteroidetes, α-, and γ-proteobacteria).2 values ≤ 0.07 g m -3 and pH of 7.6 ± 0.4). Microbial characterization showed that the N-AOM process was performed in absence of putative N-AOM archaea and bacteria (ANME-2d, M. oxyfera). Instead, microbial activity was driven by methane-oxidizing bacteria and denitrifying bacteria (Bacteroidetes, α-, and γ-proteobacteria)., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Objectives: To assess the effect of one-step temperature increase, from 35 to 55 °C, on the methane production of a mesophilic granular sludge (MGS) treating wine vinasses and the effluent of a hydrogenogenic upflow anaerobic sludge blanket (UASB) reactor., Results: One-step temperature increase from mesophilic to thermophilic conditions improved methane production regardless of the substrate tested. The biomethane potentials obtained under thermophilic conditions were 1.8-2.9 times higher than those obtained under mesophilic conditions. The MGS also performed better than an acclimated thermophilic digestate, producing 2.2-2.5 times more methane than the digestate under thermophilic conditions. Increasing the temperature from 35 to 55 °C also improved the methane production rate of the MGS (up to 9.4 times faster) and reduced the lag time (up to 1.9 times). Although the temperature increase mediated a decrease in the size of the sludge granules, no negative effects on the performance of the MGS was observed under thermophilic conditions., Conclusions: More methane is obtained from real agroindustrial effluents at thermophilic conditions than under mesophilic conditions. One-step temperature increase (instead of progressive sequential increases) can be used to implement the thermophilic anaerobic digestion processes with MGS.

Objectives: To assess the effect of adding solid manure fractions on the biomethane potential (BMP) of liquid dairy cow manure and on the biokinetic parameters of the process., Results: The methanogenic potential of liquid dairy cow manure was strongly effected by adding a solid manure fraction. The 90/10 % (w/w) liquid/solid manure fraction mixture was the best substrate for CH 4 production. This substrate mixture improved by 50 % the final CH 4 production per g substrate and decreased the lag time by 220 % relative to the reference BMP test without the addition. Moreover, the addition of 20 % solid manure fraction adversely affected both the final CH 4 production and the maximum methane production rate, while increased the lag time by 400 % compared to the reference BMP test without addition., Conclusions: Liquid dairy cow manure should be supplemented with no more than 10 % of solid manure fraction in order to improve the biomethane potential of this important agro-industrial residue.

Despite several fungal strains have been retrieved from methane-containing environments, the actual capacity and role of fungi on methane abatement is still unclear. The batch biodegradation tests here performed demonstrated the capacity of Graphium sp. to co-metabolically biodegrade methane and methanol. Moreover, the performance and microbiology of a fungal-bacterial compost biofilter treating methane at concentrations of ∼2% was evaluated at empty bed residence times of 40 and 20 min under different irrigation rates. The daily addition of 200 mL of mineral medium resulted in elimination capacities of 36.6 ± 0.7 g m(-3) h(-1) and removal efficiencies of ≈90% at the lowest residence time. The indigenous fungal community of the compost was predominant in the final microbial population and outcompeted the inoculated Graphium sp. during biofilter operation., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Methanotrophic communities were enriched in three stirred tank reactors continuously supplied with CH4-laden air at 20, 2 and 0.2 gCH4 m(-3) in order to evaluate the influence of CH4 concentration on the biodegradation kinetics, population structure and potential polyhydroxyalkanoate production under sequential nitrogen limitations. The population structure of the enriched cultures, dominated by type I methanotrophs, was influenced by CH4 concentration. No significant correlation between CH4 concentration and the maximum specific degradation rate (qmax) or the half-saturation constant (KS) was recorded, microorganisms enriched at 2 gCH4 m(-3) presenting the highest qmax and those enriched at 20 and 0.2 gCH4 m(-3) exhibiting the lowest KS. Maximum polyhydroxybutyrate (PHB) contents of 1.0% and 12.6% (w/w) were achieved at 20 and 2 g CH4 m(-3), respectively. Polyhydroxyvalerate (PHV) was also detected at PHV:PHB ratios of up to 12:1 and 4:1 in the communities enriched at 20 and 0.2 gCH4 m(-3), respectively., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

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., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Today, methane (CH4), nitrous oxide (N2O), and carbon dioxide (CO2) emissions represent approximately 98 % of the total greenhouse gas (GHG) inventory worldwide, and their share is expected to increase significantly in this twenty-first century. CO2 represents the most important GHG with approximately 77 % of the total GHG emissions (considering its global warming potential) worldwide, while CH4 and N2O are emitted to a lesser extent (14 and 8 %, respectively) but exhibit global warming potentials 23 and 298 times higher than that of CO2, respectively. Most members of the United Nations, based on the urgent need to maintain the global average temperature 2 °C above preindustrial levels, have committed themselves to significantly reduce their GHG emissions. In this context, an active abatement of these emissions will help to achieve these target emission cuts without compromising industrial growth. Nowadays, there are sufficient empirical evidence to support that biological technologies can become, if properly tailored, a low-cost and environmentally friendly alternative to physical/chemical methods for the abatement of GHGs. This study constitutes a state-of-the-art review of the microbiology (biochemistry, kinetics, and waste-to-value processes) and bioreactor technology of CH4, N2O, and CO2 abatement. The potential and limitations of biological GHG degradation processes are critically discussed, and the current knowledge gaps and technology niches in the field are identified.

Landfill biogas contains certain amounts of H 2 S that must be removed in order to prevent both equipment corrosion and SO 2 emissions to the atmosphere when burnt. Anoxic desulfurization has been proven to be an eco-friendly and cost-efficient method to remove H 2 S from biogas. Nevertheless, and despite all the reported benefits, the potential consumption of methane (CH 4) during the anoxic desulfurization of landfill biogas is a factor that has not yet been thoroughly investigated. The present study evaluates the microbial composition and methane assimilation activity of three microbial samples obtained when feeding different nitrate sources, namely nitrified landfill leachate (M1) or chemical nitrate (M2, M3) with 10 days (M2) and 1.5 days (M3) hydraulic residence times. The samples were characterized by the prevalence of sulfide oxidizing bacteria [ Thiomicrospira (11.4–25.5 %), Family Rhodobacteraceae (9.9–14.3 %), Sulfurimonas (0.34–17.9 %), Thioclava (0–23.5 %) and Arcobacter (0–11.5 %)], as well as the presence of methane oxidizing bacteria [ Halomonas (0.2–16.0 %), Methylophaga (0–0.2 %) and Methylophilacea (0–0.1 %)] and heterotrophic bacteria [ Lentimicrobium (0.1–9.7 %) and Roseovarius (0.1–1.2 %)]. The highest CH 4 assimilation levels were reached under anoxic conditions at 34.0 and 50.1 g CH 4 m−3 h−1 using nitrate and nitrite, respectively. The oxygen present in the landfill biogas itself had a detrimental effect on the anoxic bioreactor nitrate removal efficiency. The presence of organic matter in the nitrified influent gave rise to CH 4 inside the anoxic desulfurization bioreactors, which resulted in the offsetting of the CH 4 oxidation caused by methane-oxidizing bacteria (MOB). [Display omitted] • The anoxic stirred tank bioreactor achieved H 2 S removal efficiencies over 95 %. • Sulfur oxidizing bacteria dominated the bacterial communities. • The presence of methane oxidizing bacteria depended on the HRT and nitrate source. • The oxygen present in the landfill biogas itself reduced the nitrate consumption. [ABSTRACT FROM AUTHOR]