Measured Emission Rates Research Articles

Measurements of methane emissions from natural gas gathering facilities and processing plants: measurement methods

Abstract. Increased natural gas production in recent years has spurred intense interest in methane (CH4) emissions associated with its production, gathering, processing, transmission, and distribution. Gathering and processing facilities (G&P facilities) are unique in that the wide range of gas sources (shale, coal-bed, tight gas, conventional, etc.) results in a wide range of gas compositions, which in turn requires an array of technologies to prepare the gas for pipeline transmission and distribution. We present an overview and detailed description of the measurement method and analysis approach used during a 20-week field campaign studying CH4 emissions from the natural gas G&P facilities between October 2013 and April 2014. Dual-tracer flux measurements and on-site observations were used to address the magnitude and origins of CH4 emissions from these facilities. The use of a second tracer as an internal standard revealed plume-specific uncertainties in the measured emission rates of 20–47%, depending upon plume classification. Combining downwind methane, ethane (C2H6), carbon monoxide (CO), carbon dioxide (CO2), and tracer gas measurements with on-site tracer gas release allows for quantification of facility emissions and in some cases a more detailed picture of source locations.

A measurement system for alpha and beta surface emission rate using MWPC**Supported by National Natural Science Foundation of China (41204133)

We have developed a large area multi-wire proportional counter (MWPC) as a standard for the measurement of alpha and beta surface emission rate at the Shanghai Institute of Measurement and Testing Technology (SIMT). To shorten the preparation time for chamber gas refilling, a self-designed gas control unit was adopted. Various characteristics of the system have been studied. The uncertainties were analysed. Three certified alpha plane sources (Am-241) and six certified beta plane sources (Tl-204 and Sr-90/Y-90) were measured by this system. The results show excellent agreement with the surface emission rate reported by the National Institute of Measuring, China (NIM) that En values of all measured sources are within ±1.

Estimating terpene and terpenoid emissions from conifer oleoresin composition

The following algorithm, which is based on the thermodynamics of nonelectrolyte partitioning, was developed to predict emission rates of terpenes and terpenoids from specific storage sites in conifers:Ei=xoriγoripi∘where Ei is the emission rate (μg C gdw−1 h−1) and pi∘ is the vapor pressure (mm Hg) of the pure liquid terpene or terpenoid, respectively, and xori and γori are the mole fraction and activity coefficient (on a Raoult's law convention), respectively, of the terpene and terpenoid in the oleoresin. Activity coefficients are calculated with Hansen solubility parameters that account for dispersive, polar, and H-bonding interactions of the solutes with the oleoresin matrix. Estimates of pi∘ at 25 °C and molar enthalpies of vaporization are made with the SIMPOL.1 method and are used to estimate pi∘ at environmentally relevant temperatures. Estimated mixing ratios of terpenes and terpenols were comparatively higher above resin-acid- and monoterpene-rich oleoresins, respectively. The results indicated a greater affinity of terpenes and terpenols for the non-functionalized and carboxylic acid containing matrix through dispersive and H-bonding interactions, which are expressed in the emission algorithm by the activity coefficient. The correlation between measured emission rates of terpenes and terpenoids for Pinus strobus and emission rates predicted with the algorithm were very good (R = 0.95). Standard errors for the range and average of monoterpene emission rates were ±6 – ±86% and ±54%, respectively, and were similar in magnitude to reported standard deviations of monoterpene composition of foliar oils (±38 – ±51% and ±67%, respectively).

Concentration effect on the spectroscopic behavior of Tb3+ ions in zinc phosphate glasses

Zinc phosphate glasses (PZABPTb) in the compositional system: P2O5–ZnO–Al2O3–BaO–PbO doped with variable Tb3+ concentrations (1–5wt% Tb2O3) were prepared and characterized through absorption, excitation, emission and intensity decay rate measurements. The Judd–Ofelt model has been adopted to evaluate the radiative properties of the 5D4→7F6–3 emission transitions. The effect of Tb3+ ion concentration on the emissions from the 5D3,4 excited levels is discussed in detail. Analysis of the intensity decay curves corresponding to blue and green emissions from levels 5D3 and 5D4, respectively, allowed determination of effective lifetimes, which confirmed the Tb3+ ion concentration quenching of the blue emission in these glasses. The decay curves for the 5D3 level are found to be non-exponential in nature for all the studied concentrations due to ion–ion energy transfer through cross-relaxation. In an attempt to identify the origin of the energy transfer mechanism, the decay curves were well fitted to the Inokuti–Hirayama model for S=6, which indicates that the energy transfer process is of dipole–dipole type. The optical band gap energy (Eopt) has been evaluated taking into account the ultraviolet edge of absorption spectra.

Heterogeneity of O2 dynamics in soil amended with animal manure and implications for greenhouse gas emissions

Soil oxygen (O2) availability influences nitrification and denitrification, the major biological processes responsible for nitrous oxide (N2O) production and emissions from soil. In this study O2-specific planar optodes were used to visualise O2 distribution with high spatial and temporal resolution in soils in which the same amount of solid fraction of pig manure had been distributed in three different ways (mixed, layered, single patch) and which were maintained at a water potential of −5 kPa (corresponding to 91% of water-filled pore space). In parallel, the greenhouse gas emissions (N2O, CO2 and CH4) from soil at high temporal resolution were monitored. At the end of the incubations, vertical profiles of mineral nitrogen (ammonium and nitrate) in the soil matrix were quantified. The optode results revealed that anoxia rapidly developed in zones with manure addition and gradually expanded to the entire soil during the 66-h experimental period. The anoxia in the soil developed more quickly as the heterogeneity of manure distribution decreased (from single patch to layered to mixed). The single patch distribution of manure solids delayed peak emission rates of both N2O and CO2, but stimulated the cumulative N2O emissions and reduced the cumulative CO2 fluxes. The faster the anoxia developed, the less the nitrification process appeared to contribute to N2O emissions. No treatment effects on CH4 emissions were observed. Combined high resolution imaging of O2 dynamics and measurements of N2O emission rates are essential to get a detailed understanding of how O2 availability regulates the distribution and coupling of denitrification and nitrification activity in soil. Such unique information on soil O2 dynamics could be used for further modelling and quantification of processes producing greenhouse gases from soil ecosystems.

Variability of OH(3–1) emission altitude from 2003 to 2011: Long-term stability and universality of the emission rate–altitude relationship

Vertical volume emission rate profiles of the OH(3–1) Meinel emission near the mesopause are retrieved from nighttime limb-emission observations with the SCIAMACHY (Scanning Imaging Absorption spectroMeter for Atmospheric CHartographY) instrument on the Envisat satellite. Mean emission altitudes are determined by weighting altitude with the vertical OH(3–1) volume emission rate profile. Analysis of the SCIAMACHY data set from January 2003 to December 2011 shows a clear semi-annual variation of the mean emission altitudes at low latitudes – where SCIAMACHY performs measurements throughout the year – with an amplitude of 0.5–1.0km. Confirming earlier studies, we find a near constant, or universal, scaling of mean OH emission altitude and vertically integrated emission rate, which can be employed by ground-based observers to infer indirect information on OH emission altitude and its variability, if measurements of OH emission rates are performed. For this purpose we provide climatological fit parameters for the altitude/emission rate relationship. No obvious long-term trends or 11-year solar cycle signatures are present in the OH emission altitude time series, partly contradicting earlier studies. The long-term stability in OH emission altitude at the local time of the SCIAMACHY nighttime observations (10 p.m.) strengthens the use of ground-based OH rotational temperature measurements to study middle atmospheric climate change.

Real-time emissions from construction equipment compared with model predictions

The construction industry is a large source of greenhouse gases and other air pollutants. Measuring and monitoring real-time emissions will provide practitioners with information to assess environmental impacts and improve the sustainability of construction. We employed a portable emission measurement system (PEMS) for real-time measurement of carbon dioxide (CO2), nitrogen oxides (NOx), hydrocarbon, and carbon monoxide (CO) emissions from construction equipment to derive emission rates (mass of pollutant emitted per unit time) and emission factors (mass of pollutant emitted per unit volume of fuel consumed) under real-world operating conditions. Measurements were compared with emissions predicted by methodologies used in three models: NONROAD2008, OFFROAD2011, and a modal statistical model. Measured emission rates agreed with model predictions for some pieces of equipment but were up to 100 times lower for others. Much of the difference was driven by lower fuel consumption rates than predicted. Emission factors during idling and hauling were significantly different from each other and from those of other moving activities, such as digging and dumping. It appears that operating conditions introduce considerable variability in emission factors. Results of this research will aid researchers and practitioners in improving current emission estimation techniques, frameworks, and databases.Implications: Construction equipment is an important source of air pollutant emissions. There are large uncertainties in estimates of emissions from construction equipment, partly due to the small number of published measurements. The authors have expanded the database by measuring emissions of CO2, NOx, hydrocarbons, and CO from construction equipment under actual operating conditions on-site. There were large discrepancies between measured emissions and those predicted by models, including NONROAD and OFFROAD. Emission factors associated with idling and hauling were significantly different from each other and from those of other activities. These results can be used to improve the next generation of emission estimation models.

Estimating daily methane production in individual cattle with irregular feed intake patterns from short-term methane emission measurements

Spot measurements of methane emission rate (n = 18 700) by 24 Angus steers fed mixed rations from GrowSafe feeders were made over 3- to 6-min periods by a GreenFeed emission monitoring (GEM) unit. The data were analysed to estimate daily methane production (DMP; g/day) and derived methane yield (MY; g/kg dry matter intake (DMI)). A one-compartment dose model of spot emission rate v. time since the preceding meal was compared with the models of Wood (1967) and Dijkstra et al. (1997) and the average of spot measures. Fitted values for DMP were calculated from the area under the curves. Two methods of relating methane and feed intakes were then studied: the classical calculation of MY as DMP/DMI (kg/day); and a novel method of estimating DMP from time and size of preceding meals using either the data for only the two meals preceding a spot measurement, or all meals for 3 days prior. Two approaches were also used to estimate DMP from spot measurements: fitting of splines on a ‘per-animal per-day’ basis and an alternate approach of modelling DMP after each feed event by least squares (using Solver), summing (for each animal) the contributions from each feed event by best-fitting a one-compartment model. Time since the preceding meal was of limited value in estimating DMP. Even when the meal sizes and time intervals between a spot measurement and all feeding events in the previous 72 h were assessed, only 16.9% of the variance in spot emission rate measured by GEM was explained by this feeding information. While using the preceding meal alone gave a biased (underestimate) of DMP, allowing for a longer feed history removed this bias. A power analysis taking into account the sources of variation in DMP indicated that to obtain an estimate of DMP with a 95% confidence interval within 5% of the observed 64 days mean of spot measures would require 40 animals measured over 45 days (two spot measurements per day) or 30 animals measured over 55 days. These numbers suggest that spot measurements could be made in association with feed efficiency tests made over 70 days. Spot measurements of enteric emissions can be used to define DMP but the number of animals and samples are larger than are needed when day-long measures are made.

Validation of the SO2 camera for high temporal and spatial resolution monitoring of SO2 emissions

Ground-based measurements of sulfur dioxide (SO2) are a key part of monitoring networks at many volcanic centers. SO2 camera systems represent an attractive addition to conventional spectroscopic methods such as COSPEC or DOAS, because they offer higher sampling rates (up to 1Hz) and two-dimensional concentration mapping which provides additional contextual information for emission rate calculation and interpretation. Here we present the results of an SO2 camera development project and corresponding validation experiment conducted at a coal-burning power plant in Arizona (USA), where the emissions are independently measured. Emissions of SO2 and other acid gases are regulated in the United States, and hourly data are publicly reported by the US Environmental Protection Agency (EPA). We measured the emissions from two exhaust stacks that had an average combined rate of 8.2±2.1×10−2kgs−1 (7±1.8td−1) over a period of 3h. Masses integrated from our dataset are within 10–20% of the emissions reported by the EPA. The contextual information contained in the images allowed the identification and measurement of the individual plumes from each stack. Measured emission rates decrease with increasing distance from the source, pointing to an apparent loss of SO2 primarily by gas dilution processes, with SO2 concentrations dropping below the detection limit at the edge of the plume at distances>200m from the source. Cross-sections very close to the vent (within 50m; ~2 vent diameters), through the optically thick condensing part of the plume, yielded emission rates lower than those reported to the EPA. This near-vent discrepancy is interpreted to be the result of light dilution effects due to attenuation and reflections off the surface of the condensing plume. This work is the first reported validation of emission rate measurements produced by an SO2 camera in a volcano-like geometry, and demonstrates that reliable emission rates can be measured, but also emphasizes the importance of the selection of the cross-section locations.

Large methyl halide emissions from south Texas salt marshes

Abstract. Coastal salt marshes are natural sources of methyl chloride (CH3Cl) and methyl bromide (CH3Br) to the atmosphere, but measured emission rates vary widely by geography. Here we report large methyl halide fluxes from subtropical salt marshes of south Texas. Sites with the halophytic plant, Batis maritima, emitted methyl halides at rates that are orders of magnitude greater than sites containing other vascular plants or macroalgae. B. maritima emissions were generally highest at midday; however, diurnal variability was more pronounced for CH3Br than CH3Cl, and surprisingly high nighttime CH3Cl fluxes were observed in July. Seasonal and intra-site variability were large, even taking into account biomass differences. Overall, these subtropical salt marsh sites show much higher emission rates than temperate salt marshes at similar times of the year, supporting the contention that low-latitude salt marshes are significant sources of CH3Cl and CH3Br.

Impact of changes in barometric pressure on landfill methane emission

AbstractLandfill methane emissions were measured continuously using the eddy covariance method from June to December 2010. The study site was located at the Bluff Road Landfill in Lincoln, Nebraska, USA. Our results show that landfill methane emissions strongly depended on changes in barometric pressure; rising barometric pressure suppressed the emission, while falling barometric pressure enhanced the emission, a phenomenon called barometric pumping. There was up to a 35‐fold variation in day‐to‐day methane emissions due to changes in barometric pressure. Wavelet coherence analysis revealed a strong spectral coherency between variations of barometric pressure and methane emission at periodicities ranging from 1 day to 8 days. Power spectrum and ogive analysis showed that at least 10 days of continuous measurements was needed in order to capture 90% of the total variance in the methane emission time series at our landfill site. From our results, it is clear that point‐in‐time measurements taken at monthly or longer time intervals using techniques such as the trace plume method, the mass balance method, or the closed‐chamber method will be subject to large variations in measured emission rates because of the barometric pumping phenomenon. Estimates of long‐term integrated methane emissions from landfills based on such measurements could yield uncertainties, ranging from 28.8% underestimation to 32.3% overestimation. Our results demonstrate a need for continuous measurements to quantify annual total landfill emissions. This conclusion may apply to the study of methane emissions from wetlands, peatlands, lakes, and other environmental contexts where emissions are from porous media or ebullition. Other implications from the present study for hazard gas monitoring programs are also discussed.

A comparison of satellite‐ and ground‐based measurements of SO2 emissions from Tungurahua volcano, Ecuador

AbstractSatellite‐measured SO2 mass loadings and ground‐based measurements of SO2 emission rate are not directly comparable, with ∼40% differences between mean emissions reported by each technique from Tungurahua volcano, Ecuador, during late 2007. Numerical simulations of postemission processing and dispersal of Tungurahua's SO2 emissions enable more effective comparison of ground‐ and satellite‐based SO2 data sets, reducing the difference between them and constraining the impact of plume processing on satellite SO2 observations. Ground‐based measurements of SO2 emission rate are used as the model input, and simulated SO2 mass loadings are compared to those measured by the Ozone Monitoring Instrument (OMI). The changing extent of SO2 processing has a significant impact on daily variation in SO2 mass loading for a fixed volcanic emission rate. However, variations in emission rate at Tungurahua are large, suggesting that overall volcanic source strength and not subsequent processing is more likely to be the dominant control on atmospheric mass loading. SO2 emission rate estimates are derived directly from the OMI observations using modeled SO2 lifetime. Good agreement is achieved between both observed and simulated mass loadings (∼21%) and satellite‐derived and ground‐measured SO2 emission rates (∼18%), with a factor of 2 improvement over the differences found by simple direct comparison. While the balance of emission source strength and postemission processing will differ between volcanoes and regions, under good observation conditions and where SO2 lifetime is ∼24 hours, satellite‐based sensors like OMI may provide daily observations of SO2 mass loading which are a good proxy for volcanic source strength.

Experimental and Monte Carlo simulation on new manganese bath facility for absolute neutron source emission rate measurement at ENEA-INMRI

This work deals with the absolute measurement of the neutron emission rate from a 241Am–Be source by means of the manganese sulphate bath technique, which is the principal method for the absolute determination of the neutron emission rate from radionuclide neutron sources. The facility consists of a spherical container filled with an aqueous solution of manganese sulphate with a 241Am–Be neutron source placed at the center. As well known, neutrons from the source, after having been thermalized by the aqueous solution, undergo neutron capture by hydrogen, manganese, sulphur, and oxygen nuclei, thus inducing a certain activity to the solution. Subsequent gamma spectrometry measurements of 56Mn activity generated by 55Mn neutron activation allows to determine the neutron emission rate of the source, The experimental activity has involved a variety of measurement techniques and calculation procedures, ranging from neutron reactor activation to liquid scintillation counting and Monte Carlo calculations. Neutron activations of 55Mn samples has been carried out with the TRIGA reactor of the ENEA-Casaccia Research Centre, and 56Mn activated samples were subsequently characterized by liquid scintillation counting, in order to obtain reference standards for the calibration of the NaI(Tl) scintillation detectors utilized to record gamma-ray emission from 56Mn. Monte Carlo calculations, carried out by the MCNPX code, were required to calculate neutron transport within the sulphate manganese bath, in particular to determine 55Mn neutron capture probability, and (n, α) and (n, p) concurrent reactions, as well as the neutron leakage. Such a procedure has allowed to maintaining the neutron emission rate uncertainty well below 1 %. All the measurements have been carried out at the ENEA-Casaccia Research Centre by the Italian National Institute of Ionizing Radiation Metrology.

The emission rates of CH, CD and C2 spectral bands and a re-evaluation of the chemical sputtering yield of the JT-60U carbon divertor plates

The CH photon emission rate, defined as the number of photons over a dissociation and/or ionization event of CH4, has been determined from the ratio of the measured emission intensity of the CH spectral band over the CH4 injection rate into the divertor plasma of JT-60U. Similar photon emission rates of CD for CD4, and CH and C2 for C2H4 and C2H6, have also been determined. Interestingly, the C2 spectral band intensity is found to increase during the CH4 and CD4 injection, suggesting that the injected CH4 reacts with the carbon divertor plates to form heavier hydrocarbons. Previously published chemical sputtering yields (Nakano et al 2002 Nucl. Fusion 42 689) evaluated with the photon efficiencies determined in PISCES-A (Pospieszczyk et al 1989 UCLA Report UCLA-PPG-1251) have been re-evaluated using the measured emission rates. By applying the photon emission data found here and taking into account the C2 emission process originating from CH4, the re-evaluated total chemical sputtering yield becomes lower (∼7%) compared to the original in (Nakano et al 2002 Nucl. Fusion 42 689) (∼8%), and the dependence on the incident ion flux and energy becomes weaker.

Nitrous Oxide Fluxes from a Commercial Beef Cattle Feedlot in Kansas

Emission of greenhouse gases, including nitrous oxide (N2O), from open beef cattle feedlots is becoming an environmental concern; however, research measuring emission rates of N2O from open beef cattle feedlots has been limited. This study was conducted to quantify N2O emission fluxes as affected by pen surface conditions, in a commercial beef cattle feedlot in the state of Kansas, USA, from July 2010 through September 2011. The measurement period represented typical feedlot conditions, with air temperatures ranging from -24 to 39°C. Static flux chambers were used to collect gas samples from pen surfaces at 0, 15, and 30 minutes. Gas samples were analyzed with a gas chromatograph and from the measured concentrations, fluxes were calculated. Median emission flux from the moist/muddy surface condition was 2.03 mg m−2 hour−1, which was about 20 times larger than the N2O fluxes from the other pen surface conditions. In addition, N2O peaks from the moist/muddy pen surface condition were six times larger than emission peaks previously reported for agricultural soils.

Measurement of the 250Cf component in a 252Cf neutron source at KRISS

Neutron emission rate measurements have been carried out at the Korea Research Institute of Standards and Science using a manganese sulphate bath system for (252)Cf and (241)Am-Be sources since 2004. The relative measurement method was chosen in 2012, and the neutron emission rates agreed with those by the absolute measurement method within uncertainties. The neutron emission rate of an old (252)Cf source has been measured three times: in 2004, 2009 and 2012. The (250)Cf component was fitted to a double-exponential function of (252)Cf+(250)Cf, and the ratio of the (250)Cf component to the (252)Cf component was estimated to be 7.8 % in 2004 and 46.8 % in 2012. Underestimation of the neutron emission rates of old (252)Cf sources can be corrected if the neutron emission rate of the (250)Cf component is taken into account.

Automated online measurement of N2, N2O, NO, CO2, and CH4 emissions based on a gas-flow-soil-core technique

The gas-flow-soil-core (GFSC) technique allows to directly measure emission rates of denitrification gases of incubated soil cores. However, the technique was still suffering some drawbacks such as inadequate accuracy due to asynchronous detection of dinitrogen (N2) and other gases and low measurement frequency. Furthermore, its application was limited due to intensive manual operation. To overcome these drawbacks, we updated the GFSC system as described by Wang et al. (2011) by (a) using both a chemiluminescent detector and a gas chromatograph detector to measure nitric oxide (NO), (b) synchronizing the measurements of N2, NO, nitrous oxide (N2O), carbon dioxide (CO2) and methane (CH4), and (c) fully automating the sampling/analysis of all the gases. These technical modifications significantly reduced labor demands by at least a factor of two, increased the measurement frequency from 3 to 6 times per day and resulted in remarkable improvements in measurement accuracy (with detection limits of 0.5, 0.01, 0.05, 2.3 and 0.2μgN or Ch−1kg−1ds, or 17, 0.3, 1.8, 82, and 6μgN or Cm−2h−1, for N2, N2O, NO, CO2, and CH4, respectively). In some circumstances, the modified system measured significantly more N2 and CO2 and less N2O and NO because of the enhanced measurement frequency. The modified system distinguished the differences in emissions of the denitrification gases and CO2 due to a 20% change in initial carbon supplies. It also remarkably recovered approximately 90% of consumed nitrate during incubation. These performances validate the technical improvement, and indicate that the improved GFSC system may provide a powerful research tool for obtaining deeper insights into the processes of soil carbon and nitrogen transformation during denitrification.

Impact of tropospheric tides on the nitric oxide 5.3 μm infrared cooling of the low‐latitude thermosphere during solar minimum conditions

This paper explores the impact of diurnal tides that begin near the surface as heat is released by evaporation and condensation on Earth's upper atmosphere natural thermostat: the nitric oxide (NO) infrared cooling of the thermosphere at 5.3 μm. Equatorial NO volume emission rate measurements from 100 to 180 km made by Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) on TIMED during the solar minimum year 2008 are analyzed on two important nonmigrating tides, the DE2 and DE3 components. DE3 (DE2) amplitudes maximize around 125 km altitude and, depending on season, are on the order of 0.18 (0.16) nW/m3. This represents a substantial modulation of the mean NO emission that maximizes in the same altitude range with a value of about 0.8 nW/m3. Tropospheric tides are therefore important not only for the dynamics and electrodynamics of the ionosphere‐thermosphere system but also for modulating the thermospheric energy budget. Supporting photochemical tidal modeling indicates that the main tidal coupling mechanism is the temperature dependence of the collisional excitation of the NO (ν=1) vibrational state. However, the response to vertical tidal advection is also important. It is in‐phase with the response to temperature and contributes as much as 50% to the NO tides at and above the emission maximum. Neutral density tidal variations contribute about 25% but with a 9 h phase offset resulting in a net damping. These results imply that NO 5.3 μm emissions are a suitable proxy for studying tidal dynamics in the thermosphere where no global temperature measurements are available.

Calorespirometry as a tool for studying temperature response in carrot (Daucus carota L.)

Calorespirometric measurements of metabolic heat rates and CO2 emission rates of respiring tissues as functions of temperature enable rapid determination of the temperatures that plants are adapted to without growing them in different environmental temperatures. However, the correct choice of target material for measurements that enable prediction of growth temperature responses is crucial, and needs to be identified in a species‐ and trait‐specific manner. In this study, different carrot materials were tested: a primary culture system proposed as an in vitro test system for carrot yield potential, taproots of young plants, and the root meristem of actively growing plants during secondary root growth. The central root meristem is the most suitable for studying temperature response by calorespirometry for genotype comparison. Calorespirometric methods for predicting genotype‐specific temperature responses of crop plant cultivars can be used to predict productivity in environments with differing temperature conditions.

Calibration of a fugitive emission rate measurement of an area source

A major challenge to measuring fugitive emission rates from large area sources, such as landfills or tailings ponds, has been the establishment of the accuracy of such methods, or of a particular measurement. When such measurements are carried out, they are invariably associated with a relatively high degree of uncertainty. The Airborne Matter Mapping (AMM) method is a new method of measuring fugitive emission rates that can be applied to large area sources. The method was applied to the measurement of methane emissions from a landfill to assess the potential accuracy of the method, and the measurement process was calibrated to increase confidence in the measured value. First, a measured rate of methane from a gas cylinder was released from near the center of the landfill and the AMM method was applied to measure the methane flow rate across a measurement surface. Then, the AMM method was performed a second time along the same measurement surface without the intentional release of methane. The difference of the flow rates across the measurement surface were then compared with the measured rate of methane released from the gas cylinder. The relatively small difference of –5.7% between the flow rates, relative to the methane release rate from the gas cylinder, provides confidence in the accuracy of this AMM method measurement. An adjustment to the AMM method analysis was made such that the difference between the flow rates was negligible, which resulted in a calibrated measurement of the methane emission rate from the landfill of 0.87 g/sec. Implications: To properly manage fugitive emissions to the atmosphere, accurate measurement of fugitive emission rates is necessary. The Airborne Matter Mapping (AMM) method has the potential to provide accurate measurements of fugitive emission rates from large area sources, such as landfills, tailings ponds, and mines. The measurements can be calibrated against the metered release of a standard. This calibration can provide confidence in the accuracy of an AMM method measurement of the fugitive emission rate from a source.