We include emissions from the end use of oil products and natural gas for the first time in the 2022 Global Methane Tracker (4 Mt or 3% energy-related methane). For example, Lamb et al. However, precision and accuracy are worse than what can be achieved using the ground-based network, making the quantification of large-scale trends more difficult. The three most common California cover types used for this simulation were taken from an independent dataset developed by the California Department of Resources Recycling and Recovery (Walker et al., 2012). Go to the equivalencies calculator page for more information. The technique is less costly compared with the investment to build and operate respiration chambers, and has been widely used by research groups around the globe. Isotopic fingerprinting using the 13C of methane and carbon dioxide has also been used to verify seasonal methane production in a landfill cover soil (Bogner et al., 2011). In the United States, Btu, a measure of heat energy, is the most common unit for comparing energy sources or fuels. Methane Emissions Detection and Measurement Techniques, Equipment and Costs. Schwietzke et al. In general, concentration is a measurement of the amount of some molecule (the solute) in some other medium (the solvent). Dividing by the path length in meters gives us back units of ppm. (2018) used both global inversions with high-resolution nested grids over Europe and Lagrangian inverse models to estimate European methane emissions. Occurring already for thousands of years, the biogenic carbon cycle sees atmospheric carbon sequestered by plants and transformed into carbohydrates. Top-down measurements confirmed the daily variability in emissions, and overall, the study confirmed that knowledge of both local facilities and daily operational schedules are important in comparing top-down and bottom-up emission estimates. Aircraft-based measurements can be used to estimate emissions from individual facilities (e.g., an animal feeding operation, a landfill, or a natural gas processing facility). Changes in digestive and metabolic activities at the same level of feed intake, differences in feed efficiency, and variation in rumen fermentation can influence the amount of carbon dioxide produced by the animal and thus affect the predicted methane emissions (Huhtanen et al., 2015). This leads naturally to using units of standard cubic feet per hour (SCFH) On the other hand, gas analyzers or sniffers, such as the SensIt, inhale a known volume of air, and determine the amount of methane mixed in with it, leading to the use of parts per million (PPM). If the vehicle drives along a path that is perpendicular to the wind direction, the horizontal extent of the plume can be determined. One approach uses estimated carbon dioxide emissions and measured carbon dioxide/methane ratio in exhaled air to estimate methane emissions (Madsen et al., 2010). In the atmosphere, it aggravates the climate change, but in industrial processes, it can be turned into useful products such as heat, electricity or biofuel. While methane is actively becoming CO2, this CO2 is different than the CO2 emitted from the burning of fossil fuels for several reasons. Satellite data can be used in atmospheric inversions in the same way as ground-based observations. Emissions averaged 0.20% of throughput for gathering facilities and 0.075% of throughput for processing facilities. Air samples have been collected from a variety of platforms including cargo ships, small aircraft, and tall telecommunications towers. By using multiple inverse models, Locatelli et al. Monitoring observations of some nonmethane hydrocarbons are currently being made in NOAA/ESRL air samples by both NOAA and INSTAAR, and by UC Irvine, and as in situ measurements at AGAGE stations. These numbers are regularly reported to the EPA. (2015), among others, discussed the difficulty of disentangling transport errors from errors in specifying the locations of the emission sources. Thats a personal decision based on many factors. Accurate hemispheric averages and decadal variations can only be fully captured by long-term in situ sampling networks, which must be the backbone of any global observing strategy. (2014). Does not rely on atmospheric modeling to derive fluxes. With an increasing number of underground mine closings, this is an important category that requires improvement in methane emission predictions. Emission rates are estimated using a mass balance approach; the concentration differences between the upwind and downwind portions of the flight paths are multiplied by the ventilation rate for the volume enclosed by the flight paths to arrive at the emission estimate (e.g., Conley et al., 2017; Gvakharia et al., 2017). Intensity-based targets measure the amount of greenhouse gas (GHG) emissions, such as methane and carbon dioxide, per unit of energy or barrel of oil and gas produced. The SI base unit for amount of substance is the mole. a The sensitivity footprint of an observation at a tower is the region over which emissions can be sensed at that tower. Feet? Houweling et al. This principal is known as Beers Law, which is sometimes colloquially expressed as The bigger the glass, the darker the brew, the harder it is for light to get through.[3] As a result, open-path systems will often report concentration as parts per million meter (ppm-m), which takes into account the effect of path length on the measurement. Mass balance techniques can be used to measure emissions from enclosed barns or other areas (manure storage) that are mechanically ventilated. University of California, Davis, One Shields Avenue, Davis, CA 95616 | 530-752-1011. For instance, one popular old-school approach for measuring natural gas emissions is bagging: one places a bag of a known volume over the leaking component, and times how long it takes to fill up. Environmental factors such as temperature, wind velocity (particularly important for grazing conditions), and humidity can affect the accuracy of the measurements). However, using the sun as a light source excludes nighttime measurements. What I will do is present the latest, most accurate research we have on animal agriculture and air quality in regards to climate. In addition, uncertainties were reduced by doubling the number of transects and employing a wind profiler. Careful evaluation of such data for use in national methane inventories is necessary to ensure representativeness of annual average assessments. Some measurement systems use open-path spectrometers with reflectors at multiple elevations to obtain cross sections of the methane plume (e.g., Childers et al., 2001; Goldsmith et al., 2012). One of the primary advantages of remote sensing is that, in principle, it enables global, frequent coverage with a single instrument. A technique similar to the sniffer method utilizes a laser methane detector to measure methane concentration in the air between the laser device and the animal (usually 1-3 m). To facilitate model use for future inventories, inputs are limited to site latitude/longitude, waste footprint area, cover soil areas, thickness and physical properties of each layered cover soil, and percentage of cover area with underlying biogas recovery. In general, emission estimates from abandoned underground mines are based on the emissions during the active phase of the mine, assuming that emissions experience a hyperbolic decline after abandonment. The uncertainty of network observations plays an important role in determining the sensitivity of the network to spatial and temporal variability of methane, and this translates into information about source distributions and their variability. Near strong local sources, gradients can be much larger, hundreds to thousands of parts per billion over relatively small distances. The use of monitoring observations from multiple institutions can significantly improve data coverage; however, it is necessary to ensure that the data are of comparable quality and are calibrated to the same scale. With the collective threat of climate disasters like flooding, drought, and more spreading around the globe, scientists are searching for ways to help reduce human-based impacts on the climate. Imagine a beam of light passing through a glass of liquid: The further the beam propagates through the liquid, the more chances it has to encounter solvent molecules, which can absorb or scatter photons out of the beam path, leading to lower observed light intensity. This metric looks at the GWP of the greenhouse gases over 100 years. Because U.S. emissions account. arbitrary units. (2017) found that emissions in the Four Corners region have likely not changed since estimates were made for 2003-2009 using space-based column-average data, and that these estimates were consistent with the EPA 2012 inventory. In particular, robustly linking cover-specific oxidation to site-specific climate is warranted. Mine-specific data are used to fit the decline curve equations (Karacan et al., 2011). Livestock are a large source of methane. MyNAP members SAVE 10% off online. The observed spatial distribution and temporal variability of atmospheric methane is a top-down constraint on its sources and sinks. This figure shows concentrations of carbon dioxide in the atmosphere from hundreds of thousands of years ago through 2021, measured in parts per million (ppm). These studies were constrained only by column-average methane from SCIAMACHY and GOSAT. 3 Methane Emission Measurement and Monitoring Methods, 5 Presenting Methane Emission Data and Results, 6 Meeting the Challenges of Characterizing Methane Emissions, Appendix B: Definition of U.S. Greenhouse Gas Inventory Categories, Appendix C: Other Anthropogenic Sources of Methane, Appendix D: U.S. Greenhouse Gas Inventory Development, Appendix E: Acknowledgment of Those Who Provided Input to the Committee, Appendix F: Common Units for Reporting Methane Concentrations and Emissions, Appendix G: Biographical Sketches of Committee Members, Appendix H: Disclosure of Conflict of Interest, Facility-scale in situ aircraft measurements, U.S. national sample of natural gas sites, Well completions, unloadings, leaks, pneumatic pumps, and controllers. Clarity and Leadership for Environmental Awareness and Research at UC Davis, GWP* a better way of measuring methane and how it impacts global temperatures. The methane increase in 2020 was not anomalous compared to other recent years. The main challenge with the estimation of methane emissions from the abandoned underground mines is generation of an accurate decline curve. Both top-down and bottom-up measurements used to estimate emissions can also be spatially and temporally sparse, leading to biases. Flow rates are relevant to oil and gas operations because they express the size of a leak intuitively. (2018) also demonstrated the value of having a relatively dense network of quasi-continuous measurements; they were able to use a network of 18 sites, as well as additional sites with less-frequent discrete sampling. Adequate observational coverage in space and time is required to fully constrain inverse models at national or regional scales. At these intermediate scales, emissions from multiple sources or components within a facility may be aggregated like a top-down assessment. 2023 KAIROS AEROSPACE All rights reserved by the content holders, independent verification of our leak rate quantification, this page put up by Highwood Emissions Management. Energy or heat content can be used to compare energy sources or fuels on an equal basis. Overall, the total error in atmospheric methane measurements has ranged from 2.4 ppb (95 percent confidence) early in the observational record to 1.1 ppb as of 2016. The animals have to acclimatize to the chamber environment before measurements take place. With the promulgation of New Source Performance Standards, requiring reduced emission completions for natural gas wells beginning in 2012, methane emissions were reduced by approximately 99 percent compared to an uncontrolled well completion for a limited number of wells on which completion emissions have been measured (Allen et al., 2013). Within specific equipment categories, such as pneumatic devices, there are also multiple potential emission subcategories, based on the method of operation of the device (for pneumatics, low bleed, high bleed, intermittent), as well as the type of service in which they are used (for pneumatics, plunger control, separator level control, emergency shutdown, and many others). Regional trends can be distinguished; for example, in comparisons with field data at 10 California sites, sites with hot/dry summers consistently had large seasonal increases in emissions due to reduced oxidation (Spokas et al., 2015). Aircraft-based measurements of methane, carbon monoxide, and ethane. All gases categorized as greenhouse gases have a global warming potential (GWP) value. underground mines by various research groups in the United States and elsewhere (Kirchgessner et al., 1993; Lunarzewski, 1998). 4 liters of milk = 1 gallon of milk). Figure 3.3 compares whole-landfill methane emissions for an Indiana landfill using an aircraft mass balance technique, tracer correlation, and modeled monthly emissions with and without oxidation (Cambaliza et al., 2017). Measuring methane emissions from manure storage is typically accomplished using external tracer techniques, inverse dispersion modeling, micrometeorology techniques, or chambers. Because of variable environmental conditions (temperature, moisture, soil processes), active microbial communities were highly diverse with distinct spatial and seasonal clustering, including the concurrent presence of atmospheric methane oxidizers. The uncertainties of both the NOAA and AGAGE network observations are very small, amounting to only about 0.06 percent of global average methane mole fraction, meaning that the network observations are sensitive across. Both approaches can be difficult to implement. Regional-scale methods are not fully developed. A map showing current sites for which greenhouse gas observations have been submitted is shown in Figure 3.5. Vulnerable to bias if the locations of tracer release differ significantly from the location of methane release. Methane, on the other hand, is a short-lived gas and breaks down in about ten years. The complementary information provided by top-down and bottom-up methods offers the opportunity to combine their strengths in coordinated measurement campaigns. Capturing the temporal variation in emissions can also be difficult because chambers may not be able to be deployed for long periods of time because the disturbance to the ambient atmospheric conditions is too great. The most commonly used metric to quantify greenhouse gas emissions is known as GWP100. In two experiments with lactating cows, Huhtanen et al. Not as accurate as in situ data, emissions not cleanly resolved. Methane concentrations, emissions, and flow rates (metered sources) are commonly reported using a wide range of units. These are calculated using GWPs from the Intergovernmental Panel on Climate . Site-specific research projects have applied multiple field techniques to measure methane emissions. A micrometeorological mass balance method can be utilized by measuring all input and output gas emissions within a given volume of air around the source with the emission rate calculated by subtraction of output and input fluxes (Harper et al., 2011; Ryden and McNeill, 1984). All of these open-air techniques have the advantage of being able to measure methane emissions from a source area without disturbing animals or altering ambient conditions. Depending on the type of system present at a facility, the measurement techniques for estimating emissions from these sources will vary. This page describes the calculations used to convert greenhouse gas emission numbers into different types of equivalent units. Potential future missions might also be able to map localized plumes from space (Thompson et al., 2016; Thorpe et al., 2016), a technique that is currently only achieved using airborne platforms (e.g., Bradley et al., 2011; Buchwitz et al., 2000; Frankenberg et al., 2016; Hulley et al., 2016; Thorpe et al., 2014; Tratt et al., 2014). Downwind sampling of sites, with onsite measurements and emission estimates. See Harper et al. At regional scales, some analyses employ mass balance approaches. Show this book's table of contents, where you can jump to any chapter by name. Methane emissions are becoming an increasingly hot topic, and for good reason: Methane is the primary component of natural gas, which accounts for 32% of US energy consumption. Commonly used units to measure Natural Gas or Methane - LNG - volume and weight: Multiply with. 9 Ed Dlugokencky, NOAA/ESRL (www.esrl.noaa.gov/gmd/ccgg/trends_ch4/). Environmental health and safety (EHS) regulations are often expressed in terms of ppm limits. . Therefore, CO2 is a stock gas because it accumulates over time. Accuracy may vary depending on the source to be measured. 1 thermie 10 6.
3 Methane Emission Measurement and Monitoring Methods | Improving Importantly, static chambers can also directly quantify uptake of atmospheric methane by soil methanotrophs with high oxidizing capacities (e.g., negative flux [Bogner et al., 1997] for landfill soils). It was initiated by the Rowland-Blake Group at the University of California (UC), Irvine, in 1978 and is ongoing, making these observations the longest-running time series of atmospheric methane concentrations. The advantage of using a regional atmospheric model is that transport can be simulated at higher resolution and is likely to be more accurate than with a coarser global model. However, even small changes in head position can result in large differences in gas concentration (Huhtanen et al., 2015). . In contrast to other anthropogenic sources of methane, simple (activity data multiplied by emission factor) calculations are generally inappropriate for estimating landfill methane emissions because of the complexity of soil-gas transport and oxidation processes in landfill cover soils (see also Chapter 2). While chamber systems can be utilized to measure emissions from ruminants and nonruminants, there are a variety of other techniques available to measure enteric methane emissions from ruminant animals. Common simple methods of measuring flow rates are bagging, in the case of leaks, or in the case of controlled flow, by using a flow metering device. Appropriate meteorological conditions are necessary for technique to work properly. When these conditions are met, the SF6 tracer technique can produce accurate methane emission data from a large group of animals. Time-series measurements of concentrations, analyzed by eddy covariance or by inverse modeling. Current satellite instruments have been shown to have persistent biases in space and time (e.g., Bergamaschi et al., 2013; Houweling et al., 2014) that must be accounted for if satellite data are to be assimilated into atmospheric inverse models. At global, continental, and regional scales, forward and inverse modeling methods are used. What GWP100 did not account for was that methane, as a short-lived gas, was actively removed from the atmosphere relatively soon after being emitted. The study by Bergamaschi et al. Measurement of emissions from fixed points based on flow rate and methane composition. However, most of the NOAA tower network is not equipped to measure methane continuously, although there are some Earth Networks data available for urban areas, as noted above. By using inverse modeling to evaluate bottom-up models of emissions, improvements can be made to the bottom-up models, and the result may be better confidence in coupled climatecarbon cycle predictions. (2015) and Mitchell et al. Air bottle samples are collected at the mines main ventilation fans along with airflow rate measurement. Limited to sunlit, cloud-free, snow-free scenes. The National Oceanic and Atmospheric Administration (NOAA) Cooperative Air Sampling Network methane measurements started in 1983 and continue through today at more than 60 sites where volunteers collect samples that are shipped to the NOAA Earth System Research Laboratory (ESRL) in Boulder, Colorado, for analysis (Dlugokencky et al., 1994). Moreover, using the DiAL method, working area emissions could be shown to be reduced approximately 50 percent at the end of the working day following the placement of daily cover. Multiple vertical measurements of atmospheric methane and wind-speed gradients above a source area to derive an emission rate. In our next post on this topic, well explore in greater depth how leak rate and concentration measures differ, why theyre so incompatible, and the problems associated with using concentration measures for quantifying leak rates. Simulation methods for atmospheric transport are developmental, and current uncertainties limit the reliability of regional inversions. Estimates temporal trends when measurements are made continuously. The main advantage of respiration chambers is that (1) they are accurate when properly calibrated and operated, (2) all methane emissions, including from the anus, are captured, and (3) measurements take place continuously over several days, accounting for diurnal variation in methane emissions. Schwietzke et al. Often limited to measurements from normal operations or where there are no safety concerns. I make the case [above link] that even if . A later study using the same WRF-STILT model configuration concluded that for 2007 and 2008, anthropogenic emissions were significantly underestimated for North America (Miller et al., 2013). niques are also easily employed over longer time periods, which provide coverage of temporal variability, enabling more accurate prediction of longer-term emissions. Because the EPA has incorporated some of this new information into Greenhouse Gas Inventory (GHGI) development and new regulations have been finalized that have reduced emissions from specific types of equipment and operations, large changes in the estimated inventories of methane from petroleum and natural gas systems have occurred. Complementary data on methane oxidation using a stable carbon isotopic method (Chanton and Liptay, 2000; Liptay et al., 1998) ranged from 7 to 25 percent for daily covers and from 15 to 45 percent for intermediate covers, with differences attributable both to variable cover thickness and decreased methane loading to the base of the cover due to the biogas extraction system. direction. There are two sources of methane emissions from livestock: enteric fermentation (predominantly in the digestive tract of ruminant animals) and manure management (methane produced by methanogenesis during manure storage). As documented in Table 3.3, these high-emitting sources are found in many studies of various source categories, including many studies with site access and cooperation of industry participants.
Appendix D: Comparison of Units of Measurement of Amounts of Methane by The assumption can also break down if some emissions are released from elevated locations (e.g., from the top of a storage tank) while others are at ground level. Estimates total methane emissions from point and area sources. Difficult to isolate various sources within the source area depending on source layout and meteorological conditions. Copyright The Regents of the University of California, Davis campus. (2015) found that normalized emissions (emissions as a percentage of natural gas throughput) ranged from less than 0.1 percent to more than 10 percent. Several important conditions have to be met to reduce variability in the methane measurement data when the SF6 technique is used. Quantifies diffusive emission rates from a small source area (typically 1 m. Accurately measures emissions from individual or small groups of animals in a controlled environment. Air samples at approximately 45 sites distributed throughout the Pacific Basin from Alaska to New Zealand are collected four times per year, with many of the sampling sites located on remote islands in the Pacific and along the West Coast of the United States. To prevent the occurrence of high methane levels in gassier mines, degasification of coal seams takes place prior to mining. Research results indicate that seasonal oxidation is highly variable and underestimated by the current Intergovernmental Panel on Climate Change (IPCC, 2006) default of 10 percent. The sampling frequency is about once per week, although at NOAA observatories, continuous observations are possible because air is sampled and analyzed in situ. Regional atmospheric methane observations can be made using networks of tower sites similar to those used in continental networks, but at a smaller scale. Measurement of methane and tracer concentrations across well-mixed downwind plumes to derive emission rate. Coarse spatial resolution with current instruments (>10 km). Rental Products A number of sampling technologies exist for measuring methane in a variety of applications, from source/stack testing to leak detection to CEMS. Ruminant animals are. Another direct technique with limited application is the ventilated hood chamber or box (Kebreab, 2015), which is a polycarbonate chamber enclosing the head of the animal, allowing continuous collection and analysis of eructated and exhaled gases. (2009) found that emissions in California were underestimated by 37 percent compared to prior estimates, the largest underestimate likely due to livestock. Jump up to the previous page or down to the next one. Difficult to isolate individual sources within source area depending on layout and meteorological conditions. The document below was a presentation conducted at the 1st Global Methane Initiative Workshop and Exhibition in the Middle East. Moreover, methane is estimated to be responsible for 16% of anthropogenic climate change[1]. [1] See https://gml.noaa.gov/aggi/aggi.html for details. For example, several validation studies using a backward Lagrangian stochastic inverse dispersion technique to measure emissions from livestock report errors of less than 20 percent, likely because these emissions are relatively uniform (e.g., Gao et al., 2010; McGinn et al., 2009; Ro et al., 2013). The national-park sites provide a particularly useful baseline, because there are few methane sources west of the Guadalupes. Very high combustion efficiencies (>99.5%) for a single well completion flare; bottom-up inventories generally assume 98% efficiency. Quantifies rates for soil oxidation of atmospheric methane (i.e., negative emissions resulting from high soil oxidation capacities). At larger spatial scales (e.g., global, continental, and regional), atmospheric methane concentrations can be transformed, using a variety of modeling tools, to estimate methane emissions from broad geographic areas. Coupling increased observations of atmospheric methane with improved measurements of important diagnostic quantities for atmospheric modeling (such as planetary boundary-layer depth) will likely help improve the accuracy of emission estimates, increasing observational constraints and providing critical datasets that may be used to improve atmospheric transport models. Methane emissions from livestock are microbially driven and therefore can have large spatial and temporal variability, because microbial activity is governed by the substrate available as well as other conditions. Because of these two different mechanisms of generation, typically coals of low coalification levels are targets for biogenic methane, whereas coals of high coalification level may contain thermogenic methane (e.g., Mastalerz, 2014). Its also common for leak rates to be expressed as Standard Cubic Feet per Day (SCFD) and Thousand Standard Cubic Feet per Day (MSCFD). adhered to (Hristov et al., 2015a). For example, gathering and processing facilities can process from <1 to about 1,000 metric tons (or 0.001 Tg) of gas per hour, and emission rates can vary as a result. Aircraft-based measurements upwind and downwind of production region, complemented by ground-based data. chambers, diffusive methane emissions are quantified directly from the change in methane concentration over a short time series multiplied by the chamber volume/area ratio (Rolston, 1986). In underground coal mining, activity data such as numbers of mines and quantities of coal produced are well known and emission estimates rely on stack-based sampling of. The AGAGE network also measures more than 50 other atmospheric compounds, many of which are related to methane.
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