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Journal of Environmental Management Sep 2022This study investigated whole-farm methane emissions from five Danish pig farms with different manure management practices and compared measured emission rates to...
This study investigated whole-farm methane emissions from five Danish pig farms with different manure management practices and compared measured emission rates to international and national greenhouse gas inventory emission models. Methane emissions were quantified by using the tracer gas dispersion method. Farms were measured between five and eight times throughout a whole year. One of the farms housed sows and weaners (P1) and the others focused on fattening pigs (P2-P5). The farms had different manure treatment practices including biogasification (P3), acidification (P4-P5) and no manure treatment (liquid slurry) (P1-P2). Quantified methane emissions ranged from 0.2 to 20 kg/h and the highest rates were seen at the farms with fattening pigs and with no manure treatment (P2), while the lowest emissions were detected at farms with manure acidification (P4 and P5). Average methane emission factors (EFs), normalised based on livestock units, were 14 ± 6, 18 ± 9, 8 ± 7, 2 ± 1 and 1 ± 1 g/LU/h, for P1, P2, P3, P4 and P5, respectively. Emissions from fattening pig farms with biogasification (P3) and acidification (P4-P5) facilities were 55% and 91-93% lower, respectively, than from farm with no manure treatment (P2). Inventory models underestimated farm-measured methane emissions on average by 51%, across all models and farms, with the Danish model performing the worst (underestimation of 64%). A revision of model parameters related to manure emissions, such as the estimation of volatile solids excreted and methane conversion factor parameters, could improve model output, although more data needs to be collected to strengthen the conclusions. As one of the first studies assessing whole-pig farm emissions, the results showed the potential of the applied measuring method to identify mitigation strategy efficiencies and highlighted the necessity to investigate inventory model accuracy.
Topics: Animals; Denmark; Farms; Female; Greenhouse Gases; Manure; Methane; Swine
PubMed: 35642810
DOI: 10.1016/j.jenvman.2022.115319 -
Environmental Science & Technology Feb 2023Municipal wastewater collection and treatment systems are critical infrastructures, and they are also identified as major sources of anthropogenic CH emissions that... (Review)
Review
Municipal wastewater collection and treatment systems are critical infrastructures, and they are also identified as major sources of anthropogenic CH emissions that contribute to climate change. The actual CH emissions at the plant- or regional level vary greatly due to site-specific conditions as well as high seasonal and diurnal variations. Here, we conducted the first quantitative analysis of CH emissions from different types of sewers and water resource recovery facilities (WRRFs). We examined variations in CH emissions associated with methods applied in different monitoring campaigns, and identified main CH sources and sinks to facilitate carbon emission reduction efforts in the wastewater sector. We found plant-wide CH emissions vary by orders of magnitude, from 0.01 to 110 g CH/m with high emissions associated with plants equipped with anaerobic digestion or stabilization ponds. Rising mains show higher dissolved CH concentrations than gravity sewers when transporting similar raw sewage under similar environmental conditions, but the latter dominates most collection systems around the world. Using the updated data sets, we estimated annual CH emission from the U.S. centralized, municipal wastewater treatment to be approximately 10.9 ± 7.0 MMT CO-eq/year, which is about twice as the IPCC (2019) Tier 2 estimates (4.3-6.1 MMT CO-eq/year). Given CH emission control will play a crucial role in achieving net zero carbon goals by the midcentury, more studies are needed to profile and mitigate CH emissions from the wastewater sector.
Topics: Wastewater; Carbon Dioxide; Methane; Sewage; Carbon
PubMed: 36735881
DOI: 10.1021/acs.est.2c04388 -
Journal of Dairy Science Jun 2023Genetic selection to reduce methane (CH) emissions from dairy cows is an attractive means of reducing the impact of agricultural production on climate change. In this...
Genetic selection to reduce methane (CH) emissions from dairy cows is an attractive means of reducing the impact of agricultural production on climate change. In this study, we investigated the feasibility of such an approach by characterizing the interactions between CH and several traits of interest in dairy cows. We measured CH, dry matter intake (DMI), fat- and protein-corrected milk (FPCM), body weight (BW), and body condition score (BCS) from 107 first- and second-parity Holstein cows from December 2019 to November 2021. Methane emissions were measured using a GreenFeed device and expressed in terms of production (MeP, in g/d), yield (MeY, in g/kg DMI), and intensity (MeI, in g/kg FPCM). Because of the limited number of cows, only animal parameters were estimated. Both MeP and MeI were moderately repeatable (>0.45), whereas MeY presented low repeatability, especially in early lactation. Mid lactation was the most stable and representative period of CH emissions throughout lactation, with animal correlations above 0.9. The average animal correlations of MeP with DMI, FPCM, and BW were 0.62, 0.48, and 0.36, respectively. The MeI was negatively correlated with FCPM (<-0.5) and DMI (>-0.25), and positively correlated with BW and BCS. The MeY presented stable and weakly positive correlations with the 4 other traits throughout lactation, with the exception of slightly negative animal correlations with FPCM and DMI after the 35th week. The MeP, MeI, and MeY were positively correlated at all lactation stages and, assuming animal and genetic correlations do not strongly differ, selection on one trait should lead to improvements in all. Overall, selection for MeI is probably not optimal as its change would result more from CH dilution in increased milk yield than from real decrease in methane emission. Instead, MeY is related to rumen function and is only weakly associated with DMI, FPCM, BW, and BCS; it thus appears to be the most promising CH trait for selection, provided that this would not deteriorate feed efficiency and that a system of large-scale phenotyping is developed. The MeP is easier to measure and thus may represent an acceptable alternative, although care would need to be taken to avoid undesirable changes in FPCM and BW.
Topics: Methane; Female; Animals; Cattle; Lactation; Milk; Inheritance Patterns; Gene Expression; Selective Breeding
PubMed: 37105882
DOI: 10.3168/jds.2022-22855 -
Nature Sep 2023Methane (CH) is a potent greenhouse gas and its concentrations have tripled in the atmosphere since the industrial revolution. There is evidence that global warming has...
Methane (CH) is a potent greenhouse gas and its concentrations have tripled in the atmosphere since the industrial revolution. There is evidence that global warming has increased CH emissions from freshwater ecosystems, providing positive feedback to the global climate. Yet for rivers and streams, the controls and the magnitude of CH emissions remain highly uncertain. Here we report a spatially explicit global estimate of CH emissions from running waters, accounting for 27.9 (16.7-39.7) Tg CH per year and roughly equal in magnitude to those of other freshwater systems. Riverine CH emissions are not strongly temperature dependent, with low average activation energy (E = 0.14 eV) compared with that of lakes and wetlands (E = 0.96 eV). By contrast, global patterns of emissions are characterized by large fluxes in high- and low-latitude settings as well as in human-dominated environments. These patterns are explained by edaphic and climate features that are linked to anoxia in and near fluvial habitats, including a high supply of organic matter and water saturation in hydrologically connected soils. Our results highlight the importance of land-water connections in regulating CH supply to running waters, which is vulnerable not only to direct human modifications but also to several climate change responses on land.
Topics: Ecosystem; Lakes; Methane; Rivers; Wetlands; Global Warming; Human Activities
PubMed: 37587344
DOI: 10.1038/s41586-023-06344-6 -
Nature Communications Dec 2022Hydrogen (H) is expected to play a crucial role in reducing greenhouse gas emissions. However, hydrogen losses to the atmosphere impact atmospheric chemistry, including...
Hydrogen (H) is expected to play a crucial role in reducing greenhouse gas emissions. However, hydrogen losses to the atmosphere impact atmospheric chemistry, including positive feedback on methane (CH), the second most important greenhouse gas. Here we investigate through a minimalist model the response of atmospheric methane to fossil fuel displacement by hydrogen. We find that CH concentration may increase or decrease depending on the amount of hydrogen lost to the atmosphere and the methane emissions associated with hydrogen production. Green H can mitigate atmospheric methane if hydrogen losses throughout the value chain are below 9 ± 3%. Blue H can reduce methane emissions only if methane losses are below 1%. We address and discuss the main uncertainties in our results and the implications for the decarbonization of the energy sector.
Topics: Methane; Hydrogen; Greenhouse Gases; Atmosphere; Fossil Fuels
PubMed: 36513663
DOI: 10.1038/s41467-022-35419-7 -
Biochemistry Dec 2019Methyl-coenzyme M reductase (MCR) catalyzes the methane-forming step in methanogenic archaea. The active enzyme harbors the nickel(I) hydrocorphin coenzyme F-430 as a... (Review)
Review
Methyl (Alkyl)-Coenzyme M Reductases: Nickel F-430-Containing Enzymes Involved in Anaerobic Methane Formation and in Anaerobic Oxidation of Methane or of Short Chain Alkanes.
Methyl-coenzyme M reductase (MCR) catalyzes the methane-forming step in methanogenic archaea. The active enzyme harbors the nickel(I) hydrocorphin coenzyme F-430 as a prosthetic group and catalyzes the reversible reduction of methyl-coenzyme M (CH-S-CoM) with coenzyme B (HS-CoM) to methane and CoM-S-S-CoB. MCR is also involved in anaerobic methane oxidation in reverse of methanogenesis and most probably in the anaerobic oxidation of ethane, propane, and butane. The challenging question is how the unreactive CH-S thioether bond in methyl-coenzyme M and the even more unreactive C-H bond in methane and the other hydrocarbons are anaerobically cleaved. A key to the answer is the negative redox potential (') of the Ni(II)F-430/Ni(I)F-430 couple below -600 mV and the radical nature of Ni(I)F-430. However, the negative one-electron redox potential is also the Achilles heel of MCR; it makes the nickel enzyme one of the most O-sensitive enzymes known to date. Even under physiological conditions, the Ni(I) in MCR is oxidized to the Ni(II) or Ni(III) states, e.g., when in the cells the redox potential (') of the CoM-S-S-CoB/HS-CoM and HS-CoB couple (' = -140 mV) gets too high. Methanogens therefore harbor an enzyme system for the reactivation of inactivated MCR in an ATP-dependent reduction reaction. Purification of active MCR in the Ni(I) oxidation state is very challenging and has been achieved in only a few laboratories. This perspective reviews the function, structure, and properties of MCR, what is known and not known about the catalytic mechanism, how the inactive enzyme is reactivated, and what remains to be discovered.
Topics: Anaerobiosis; Biocatalysis; Methane; Nickel; Oxidation-Reduction; Oxidoreductases
PubMed: 30951290
DOI: 10.1021/acs.biochem.9b00164 -
Biochimica Et Biophysica Acta.... Sep 2019The atmospheric concentration of the potent greenhouse gases methane and nitrous oxide (NO) has increased drastically during the last century. Methylomirabilis bacteria...
The atmospheric concentration of the potent greenhouse gases methane and nitrous oxide (NO) has increased drastically during the last century. Methylomirabilis bacteria can play an important role in controlling the emission of these two gases from natural ecosystems, by oxidizing methane to CO and reducing nitrite to N without producing NO. These bacteria have an anaerobic metabolism, but are proposed to possess an oxygen-dependent pathway for methane activation. Methylomirabilis bacteria reduce nitrite to NO, and are proposed to dismutate NO into O and N by a putative NO dismutase (NO-D). The O produced in the cell can then be used to activate methane by a particulate methane monooxygenase. So far, the metabolic model of Methylomirabilis bacteria was based mainly on (meta)genomics and physiological experiments. Here we applied a complexome profiling approach to determine which of the proposed enzymes are actually expressed in Methylomirabilis lanthanidiphila. To validate the proposed metabolic model, we focused on enzymes involved in respiration, as well as nitrogen and carbon transformation. All complexes suggested to be involved in nitrite-dependent methane oxidation, were identified in M. lanthanidiphila, including the putative NO-D. Furthermore, several complexes involved in nitrate reduction/nitrite oxidation and NO reduction were detected, which likely play a role in detoxification and redox homeostasis. In conclusion, complexome profiling validated the expression and composition of enzymes hypothesized to be involved in the energy, methane and nitrogen metabolism of M. lanthanidiphila, thereby further corroborating their unique metabolism involved in the environmentally relevant process of nitrite-dependent methane oxidation.
Topics: Bacteria, Anaerobic; Bacterial Proteins; Methane; Multienzyme Complexes; Nitrates; Nitric Oxide; Oxidation-Reduction; Oxygenases
PubMed: 31376363
DOI: 10.1016/j.bbabio.2019.07.011 -
Journal of the American Chemical Society May 2022Biocatalytic carbene transfer from diazo compounds is a versatile strategy in asymmetric synthesis. However, the limited pool of stable diazo compounds constrains the...
Biocatalytic carbene transfer from diazo compounds is a versatile strategy in asymmetric synthesis. However, the limited pool of stable diazo compounds constrains the variety of accessible products. To overcome this restriction, we have engineered variants of protoglobin (Pgb) that use diazirines as carbene precursors. While the enhanced stability of diazirines relative to their diazo isomers enables access to a diverse array of carbenes, they have previously resisted catalytic activation. Our engineered Pgb variants represent the first example of catalysts for selective carbene transfer from these species at room temperature. The structure of an Pgb variant, determined by microcrystal electron diffraction (MicroED), reveals that evolution has enhanced access to the heme active site to facilitate this new-to-nature catalysis. Using readily prepared aryl diazirines as model substrates, we demonstrate the application of these highly stable carbene precursors in biocatalytic cyclopropanation, N-H insertion, and Si-H insertion reactions.
Topics: Azo Compounds; Biocatalysis; Catalysis; Diazomethane; Methane
PubMed: 35561334
DOI: 10.1021/jacs.2c02723 -
Current Opinion in Biotechnology Jun 2021Hemoprotein-catalyzed carbene and nitrene transformations have emerged as powerful tools for constructing complex molecules; they also nicely illustrate how new protein... (Review)
Review
Hemoprotein-catalyzed carbene and nitrene transformations have emerged as powerful tools for constructing complex molecules; they also nicely illustrate how new protein catalysts can emerge, evolve and diversify. These laboratory-invented enzymes exploit the ability of proteins to tame highly reactive carbene and nitrene species and direct their fates with high selectivity. New-to-nature carbene and nitrene transferases catalyze many useful reactions, including some that have no precedent using chemical methods. Here we cover recent advances in this field, including alkyne cyclopropenation, arene cyclopropanation, carbene CH insertion, intramolecular nitrene CH insertion, alkene aminohydroxylation, and primary amination. For such transformations, biocatalysts have exceeded the performance of reported small-molecule catalysts in terms of selectivity and catalyst turnovers. Finally, we offer our thoughts on using these new enzymatic reactions in chemical synthesis, integrating them into biological pathways and chemo-enzymatic cascades, and on their current limitations.
Topics: Hemeproteins; Imines; Methane; Transferases
PubMed: 33370622
DOI: 10.1016/j.copbio.2020.12.005 -
Nature Communications Nov 2022Anaerobic methanotrophic (ANME) archaea obtain energy from the breakdown of methane, yet their extrachromosomal genetic elements are little understood. Here we describe...
Anaerobic methanotrophic (ANME) archaea obtain energy from the breakdown of methane, yet their extrachromosomal genetic elements are little understood. Here we describe large plasmids associated with ANME archaea of the Methanoperedens genus in enrichment cultures and other natural anoxic environments. By manual curation we show that two of the plasmids are large (155,605 bp and 191,912 bp), circular, and may replicate bidirectionally. The plasmids occur in the same copy number as the main chromosome, and plasmid genes are actively transcribed. One of the plasmids encodes three tRNAs, ribosomal protein uL16 and elongation factor eEF2; these genes appear to be missing in the host Methanoperedens genome, suggesting an obligate interdependence between plasmid and host. Our work opens the way for the development of genetic vectors to shed light on the physiology and biochemistry of Methanoperedens, and potentially genetically edit them to enhance growth and accelerate methane oxidation rates.
Topics: Archaea; Anaerobiosis; Methane; Oxidation-Reduction; Plasmids
PubMed: 36400771
DOI: 10.1038/s41467-022-34588-9