-
Environmental Science & Technology Jul 2021Megacities, with their large and complex infrastructures, are significant sources of methane emissions. To develop a simple, low-cost methodology to quantify these...
Megacities, with their large and complex infrastructures, are significant sources of methane emissions. To develop a simple, low-cost methodology to quantify these globally important methane sources, this study focuses on mobile measurements of methane (CH) and its isotopic composition in Paris. Data collected between September 2018 to March 2019 resulted in 17 days of measurements, which provided spatial distribution of street-level methane mixing ratios, source type identification, and emission quantification. Consequently, 90 potential leaks were detected in Paris sorted into three leak categories: natural gas distribution network emissions (63%), sewage network emissions (33%), and emissions from heating furnaces of buildings (4%). The latter category has not previously been reported in urban methane studies. Accounting for the detectable emissions from the ground, the total estimated CH emission rate of Paris was 5000 L/min (190 t/yr), with the largest contribution from gas leaks (56%). This ranks Paris as a city with medium CH emissions. Two areas of clusters were found, where 22% and 56% of the total potential emissions of Paris were observed. Our findings suggest that the natural gas distribution network, the sewage system, and furnaces of buildings are ideal targets for street-level CH emission reduction efforts for Paris.
Topics: Air Pollutants; Cities; France; Methane; Natural Gas
PubMed: 34159780
DOI: 10.1021/acs.est.1c00859 -
Environmental Science & Technology Aug 2023Government policies and corporate strategies aimed at reducing methane emissions from the oil and gas sector increasingly rely on measurement-informed, site-level...
Government policies and corporate strategies aimed at reducing methane emissions from the oil and gas sector increasingly rely on measurement-informed, site-level emission inventories, as conventional bottom-up inventories poorly capture temporal variability and the heavy-tailed nature of methane emissions. This work is based on an 11-month methane measurement campaign at oil and gas production sites. We find that operator-level top-down methane measurements are lower during the end-of-project phase than during the baseline phase. However, gaps persist between end-of-project top-down measurements and bottom-up site-level inventories, which we reconcile with high-frequency data from continuous monitoring systems (CMS). Specifically, we use CMS to (i) validate specific snapshot measurements and determine how they relate to the temporal emission profile of a given site and (ii) create a measurement-informed, site-level inventory that can be validated with top-down measurements to update conventional bottom-up inventories. This work presents a real-world demonstration of how to reconcile CMS rate estimates and top-down snapshot measurements jointly with bottom-up inventories at the site level. More broadly, it demonstrates the importance of multiscale measurements when creating measurement-informed, site-level emission inventories, which is a critical aspect of recent regulatory requirements in the Inflation Reduction Act, voluntary methane initiatives such as the Oil and Gas Methane Partnership 2.0, and corporate strategies.
Topics: Methane; Natural Gas; Air Pollutants
PubMed: 37506319
DOI: 10.1021/acs.est.3c01121 -
Nature Communications Jul 2023Atmospheric methane is both a potent greenhouse gas and photochemically active, with approximately equal anthropogenic and natural sources. The addition of chlorine to...
Atmospheric methane is both a potent greenhouse gas and photochemically active, with approximately equal anthropogenic and natural sources. The addition of chlorine to the atmosphere has been proposed to mitigate global warming through methane reduction by increasing its chemical loss. However, the potential environmental impacts of such climate mitigation remain unexplored. Here, sensitivity studies are conducted to evaluate the possible effects of increasing reactive chlorine emissions on the methane budget, atmospheric composition and radiative forcing. Because of non-linear chemistry, in order to achieve a reduction in methane burden (instead of an increase), the chlorine atom burden needs to be a minimum of three times the estimated present-day burden. If the methane removal target is set to 20%, 45%, or 70% less global methane by 2050 compared to the levels in the Representative Concentration Pathway 8.5 scenario (RCP8.5), our modeling results suggest that additional chlorine fluxes of 630, 1250, and 1880 Tg Cl/year, respectively, are needed. The results show that increasing chlorine emissions also induces significant changes in other important climate forcers. Remarkably, the tropospheric ozone decrease is large enough that the magnitude of radiative forcing decrease is similar to that of methane. Adding 630, 1250, and 1880 Tg Cl/year to the RCP8.5 scenario, chosen to have the most consistent current-day trends of methane, will decrease the surface temperature by 0.2, 0.4, and 0.6 °C by 2050, respectively. The quantity and method in which the chlorine is added, its interactions with climate pathways, and the potential environmental impacts on air quality and ocean acidity, must be carefully considered before any action is taken.
Topics: Chlorine; Methane; Climate; Air Pollution; Ozone; Atmosphere; Halogens
PubMed: 37422475
DOI: 10.1038/s41467-023-39794-7 -
Nature Microbiology Feb 2023'Candidatus Methanophagales' (ANME-1) is an order-level clade of archaea responsible for anaerobic methane oxidation in deep-sea sediments. The diversity, ecology and...
'Candidatus Methanophagales' (ANME-1) is an order-level clade of archaea responsible for anaerobic methane oxidation in deep-sea sediments. The diversity, ecology and evolution of ANME-1 remain poorly understood. In this study, we use metagenomics on deep-sea hydrothermal samples to expand ANME-1 diversity and uncover the effect of virus-host dynamics. Phylogenetic analyses reveal a deep-branching, thermophilic family, 'Candidatus Methanospirareceae', closely related to short-chain alkane oxidizers. Global phylogeny and near-complete genomes show that hydrogen metabolism within ANME-1 is an ancient trait that was vertically inherited but differentially lost during lineage diversification. Metagenomics also uncovered 16 undescribed virus families so far exclusively targeting ANME-1 archaea, showing unique structural and replicative signatures. The expansive ANME-1 virome contains a metabolic gene repertoire that can influence host ecology and evolution through virus-mediated gene displacement. Our results suggest an evolutionary continuum between anaerobic methane and short-chain alkane oxidizers and underscore the effects of viruses on the dynamics and evolution of methane-driven ecosystems.
Topics: Archaea; Ecosystem; Phylogeny; Virome; Geologic Sediments; Anaerobiosis; Methane; Alkanes
PubMed: 36658397
DOI: 10.1038/s41564-022-01297-4 -
Bioengineered Dec 2019The rise in intermittent renewable electricity production presents a global requirement for energy storage. Biological hydrogen methanation (BHM) facilitates wind and... (Review)
Review
The rise in intermittent renewable electricity production presents a global requirement for energy storage. Biological hydrogen methanation (BHM) facilitates wind and solar energy through the storage of otherwise curtailed or constrained electricity in the form of the gaseous energy vector biomethane. Biological methanation in the circular economy involves the reaction of hydrogen - produced during electrolysis - with carbon dioxide in biogas to produce methane (4H + CO = CH + 2H), typically increasing the methane output of the biogas system by 70%. In this paper, several BHM systems were researched and a compilation of such systems was synthesized, facilitating comparison of key parameters such as methane evolution rate (MER) and retention time. Increased retention times were suggested to be related to less efficient systems with long travel paths for gases through reactors. A significant lack of information on gas-liquid transfer co-efficient was identified.
Topics: Biofuels; Bioreactors; Biotechnology; Carbon Dioxide; Hydrogen; Methane; Renewable Energy
PubMed: 31679461
DOI: 10.1080/21655979.2019.1684607 -
Trends in Microbiology Mar 2022Disposal of electrons generated during the fermentation of ingested feed is a fundamental feature of anaerobic microbial gut ecosystems. Here, we focus on the...
Disposal of electrons generated during the fermentation of ingested feed is a fundamental feature of anaerobic microbial gut ecosystems. Here, we focus on the well-studied rumen environment to highlight how electrons are transferred through anaerobic fermentation pathways and how manipulating this electron flow is important to reducing methane emissions from ruminants. Priorities for research that can accelerate understanding in this area are highlighted.
Topics: Animals; Ecosystem; Electrons; Fermentation; Methane; Rumen; Ruminants
PubMed: 35027237
DOI: 10.1016/j.tim.2021.12.005 -
Journal of Environmental Management Oct 2021Methane is a short-lived greenhouse gas (GHG) modelled distinctly from long-lived GHGs such as carbon dioxide and nitrous oxide to establish global emission budgets for...
Methane is a short-lived greenhouse gas (GHG) modelled distinctly from long-lived GHGs such as carbon dioxide and nitrous oxide to establish global emission budgets for climate stabilisation. The Paris Agreement requires a 24-47% reduction in global biogenic methane emissions by 2050. Separate treatment of methane in national climate policies will necessitate consideration of how global emission budgets compatible with climate stabilisation can be downscaled to national targets, but implications of different downscaling rules for national food production and climate neutrality objectives are poorly understood. This study addresses that knowledge gap by examining four methods to determine national methane quotas, and two methods of GHG aggregation (GWP and GWP*) across four countries with contrasting agriculture, forestry and other land use (AFOLU) sectors and socio-economic contexts (Brazil, France, India and Ireland). Implications for production of methane-intensive food (milk, meat, eggs and rice) in 2050 and national AFOLU climate neutrality targets are explored. It is assumed that methane quotas are always filled by food production where sufficient land is available. Global methane budgets for 1.5 °C scenarios are downscaled to national quotas based on: grand-parenting (equal percentage reductions across countries); equity (equal per capita emissions); ability (emission reductions proportionate to GDP); animal protein security (emissions proportionate to animal protein production in 2010). The choice of allocation method changes national methane quotas by a factor of between 1.7 (India) and 6.7 (Ireland). Despite projected reductions in emission-intensities, livestock production would need to decrease across all countries except India to comply with quotas under all but the most optimistic sustainable intensification scenarios. The extent of potential afforestation on land spared from livestock production is decisive in achieving climate neutrality. Brazil and Ireland could maintain some degree of milk and beef export whilst achieving territorial climate neutrality, but scenarios that comply with climate neutrality in India produce only circa 30% of national calorie and protein requirements via rice and livestock. The downscaling of global methane budgets into national policy targets in an equitable and internationally acceptable manner will require simultaneous consideration of the interconnected priorities of food security and (land banks available for) carbon offsetting.
Topics: Agriculture; Animals; Brazil; Cattle; Climate Change; France; Greenhouse Effect; India; Ireland; Methane; Paris
PubMed: 34171781
DOI: 10.1016/j.jenvman.2021.113058 -
The Journal of Physical Chemistry. B Jun 2024Particulate MMO (pMMO) catalyzes the oxidation of methane to methanol and also ammonia to hydroxylamine. Experimental characterization of the active site has been very...
Particulate MMO (pMMO) catalyzes the oxidation of methane to methanol and also ammonia to hydroxylamine. Experimental characterization of the active site has been very difficult partly because the enzyme is membrane-bound. However, recently, there has been major progress mainly through the use of cryogenic electron microscopy (cryoEM). Electron paramagnetic resonance (EPR) and X-ray spectroscopy have also been employed. Surprisingly, the active site has only one copper. There are two histidine ligands and one asparagine ligand, and the active site is surrounded by phenyl alanines but no charged amino acids in the close surrounding. The present study is the first quantum chemical study using a model of that active site (Cu). Low barrier mechanisms have been found, where an important part is that there are two initial proton-coupled electron transfer steps to a bound O ligand before the substrate enters. Surprisingly, this leads to large radical character for the oxygens even though they are protonated. That result is very important for the ability to accept a proton from the substrates. Methods have been used which have been thoroughly tested for redox enzyme mechanisms.
Topics: Oxidation-Reduction; Methane; Oxygenases; Ammonia; Catalytic Domain; Models, Molecular; Electron Spin Resonance Spectroscopy
PubMed: 38850249
DOI: 10.1021/acs.jpcb.4c01807 -
Optics Express Jul 2022The atmospheric concentration of methane has more than doubled since the start of the Industrial Revolution. Methane is the second-most-abundant greenhouse gas created...
The atmospheric concentration of methane has more than doubled since the start of the Industrial Revolution. Methane is the second-most-abundant greenhouse gas created by human activities and a major driver of climate change. This APS-Optica report provides a technical assessment of the current state of monitoring U.S. methane emissions from oil and gas operations, which accounts for roughly 30% of U.S. anthropogenic methane emissions. The report identifies current technological and policy gaps and makes recommendations for the federal government in three key areas: methane emissions detection, reliable and systematized data and models to support mitigation measures, and effective regulation.
Topics: Air Pollutants; Greenhouse Gases; Humans; Methane
PubMed: 36236990
DOI: 10.1364/OE.464421 -
Environmental Science & Technology Jun 2024Methane is a major contributor to anthropogenic greenhouse gas emissions. Identifying large sources of methane, particularly from the oil and gas sectors, will be...
Methane is a major contributor to anthropogenic greenhouse gas emissions. Identifying large sources of methane, particularly from the oil and gas sectors, will be essential for mitigating climate change. Aircraft-based methane sensing platforms can rapidly detect and quantify methane point-source emissions across large geographic regions, and play an increasingly important role in industrial methane management and greenhouse gas inventory. We independently evaluate the performance of five major methane-sensing aircraft platforms: Carbon Mapper, GHGSat-AV, Insight M, MethaneAIR, and Scientific Aviation. Over a 6 week period, we released metered gas for over 700 single-blind measurements across all five platforms to evaluate their ability to detect and quantify emissions that range from 1 to over 1,500 kg(CH)/h. Aircraft consistently quantified releases above 10 kg(CH)/h, and GHGSat-AV and Insight M detected emissions below 5 kg(CH)/h. Fully blinded quantification estimates for platforms using downward-facing imaging spectrometers have parity slopes ranging from 0.76 to 1.13, with values of 0.61 to 0.93; the platform using continuous air sampling has a parity slope of 0.5 ( = 0.93). Results demonstrate that aircraft-based methane sensing has matured since previous studies and is ready for an increasingly important role in environmental policy and regulation.
Topics: Methane; Aircraft; Greenhouse Gases; Environmental Monitoring; Climate Change; Air Pollutants
PubMed: 38759639
DOI: 10.1021/acs.est.4c02439