Methane Emission Rates Research Articles

Avoiding methane emission rate underestimates when using the divergence method

Methane is a powerful greenhouse gas, and a primary target for mitigating climate change in the short-term future due to its relatively short atmospheric lifetime and greater ability to trap heat in Earth’s atmosphere compared to carbon dioxide. Top-down observations of atmospheric methane are possible via drone and aircraft surveys as well as satellites such as the TROPOspheric Monitoring Instrument (TROPOMI). Recent work has begun to apply the divergence method to produce regional methane emission rate estimates. Here we show that when the divergence method is applied to spatially incomplete observations of methane, it can result in negatively biased time-averaged regional emission rates. We show that this effect can be counteracted by adopting a procedure in which daily advective fluxes of methane are time-averaged before the divergence method is applied. Using such a procedure with TROPOMI methane observations, we calculate yearly Permian emission rates of 3.1, 2.4 and 2.7 million tones per year for the years 2019 through 2021. We also show that highly-resolved plumes of methane can have negatively biased estimated emission rates by the divergence method due to the presence of turbulent diffusion in the plume, but this is unlikely to affect regional methane emission budgets constructed from TROPOMI observations of methane. The results from this work are expected to provide useful guidance for future implementations of the divergence method for emission rate estimation from satellite data—be it for methane or other gaseous species in the atmosphere.

Quantification of – And determining factors affecting – Methane emissions from composting plants

Methane is a potent greenhouse gas contributing to climate change. Reliable data for methane emissions from the waste management sector are paramount in terms of providing national methane budgets and developing climate mitigation efforts. This study quantified total methane emissions and characterised temporal as well as operational emission patterns at five commercial composting plants in Denmark. Methane emissions were measured over a one-year period, using the tracer gas dispersion method. The results show that methane emission rates ranged from 8.0 ± 0.1 to 42.5 ± 1.5 kg CH4 h−1 and were significantly affected by factors including the type of feedstock and composting technology, treated feedstock mass, operational patterns and season. The results indicate that the highest methane emission factors were obtained at the combined anaerobic digestion and open windrow composting plant (4.51–5.21 kg CH4 Mg−1 wet garden/park waste (GPW) and food waste), followed by open windrow plants co-composting GPW, sewage sludge and straw (3.49–3.76 kg CH4 Mg−1 wet feedstock). The lowest methane emission factors were found at open windrow composting plants treating GPW (1.56–3.24 kg CH4 Mg−1 wet feedstock). Emissions tended to be higher when measurements were performed during working hours, in comparison to when they were measured after the plant closed for the day. At one plant, emissions were measured monthly over one year, and emissions were about 50% higher in spring and summer in comparison to autumn and winter.

Methane emission rates averaged over a year from ten farm-scale manure storage tanks

Methane (CH4) emissions from animal manure stored in outdoor tanks are difficult to predict because of several influencing factors. In this study, the tracer gas dispersion method (TDM) was used to quantify CH4 emissions from ten manure storage tanks, along with the collection of supporting information, in order to identify its emission drivers. The dataset included two tanks storing dairy cattle manure, six holding pig manure, and two with digestate from manure-based biogas plants. CH4 emissions from the tanks were measured six to 14 times over a year. Emissions varied from 0.02 to 14.30 kg h−1, or when normalised by the volume of manure stored, emission factors (EFs) varied from 0.05 to 11 g m−3 h−1. Annual average CH4 EFs varied greatly between the tanks, ranging from 0.20 to 2.75 g m−3 h−1. Normalised EFs are similar to literature values for cattle and digested manure, but at the high end of the interval for pig manure. The averaged manure temperature for all tanks varied from 10.6 to 16.4 °C, which was higher than reported in a previous Danish study. Volatile solids (VS) concentration was in average higher for cattle manure (ranging from 3.1 and 4.4 %) than pig manure (ranging from 1.0 to 3.6 %). CH4 emission rates were positively correlated with manure temperature, whereas this was not the case for VS concentration. Annual average EFs were higher for pig than for cattle manure (a factor of 2.5), which was greater than digested manure emissions (a factor of 1.2). For the pig manure storage tanks, CH4 emissions were higher for covered tanks than for uncovered tanks (by a factor of 2.3). In this study, manure storage tanks showed a large disparity in emission rates, driven not only by physical factors, but also by farm management practices.

Extension of Methane Emission Rate Distribution for Permian Basin Oil and Gas Production Infrastructure by Aerial LiDAR.

Aerial LiDAR measurements at 7474 oil and gas production facilities in the Permian Basin yield a measured methane emission rate distribution extending to the detection sensitivity of the method, 2 kg/h at 90% probability of detection (POD). Emissions are found at 38.3% of facilities scanned, a significantly higher proportion than reported in lower-sensitivity campaigns. LiDAR measurements are analyzed in combination with measurements of the heavy tail portion of the distribution (>600 kg/h) obtained from an airborne solar infrared imaging spectrometry campaign by Carbon Mapper (CM). A joint distribution is found by fitting the aligned LiDAR and CM data. By comparing the aerial samples to the joint distribution, the practical detection sensitivity of the CM 2019 campaign is found to be 280 kg/h [256, 309] (95% confidence) at 50% POD for facility-sized emission sources. With respect to the joint model distribution and its confidence interval, the LiDAR campaign is found to have measured 103.6% [93.5, 114.2%] of the total emission rate predicted by the model for equipment-sized emission sources (∼2 m diameter) with emission rates above 3 kg/h, whereas the CM 2019 campaign is found to have measured 39.7% [34.6, 45.1%] of the same quantity for facility-sized sources (150 m diameter) above 10 kg/h. The analysis is repeated with data from CM 2020-21 campaigns with similar results. The combined distributions represent a more comprehensive view of the emission rate distribution in the survey area, revealing the significance of previously underreported emission sources at rates below the detection sensitivity of some emissions monitoring campaigns.

Technology Focus: Health, Safety, and Environment (August 2023)

This year’s HSE Technical Focus feature showcases environmental sustainability. Offshore hybrid renewable power generation, electrically driven well abandonment in urban and natural settings, and the use of remotely controlled, low-carbon-footprint underwater intervention/inspection drones demonstrate HSE- and sustainability-conscious planning and successful implementation in the field. Environmental, social, and governance guidelines, as well as regulatory and sustainability-related frameworks, provide guidance to achieve the social license to operate. Risk management and stakeholder engagement practices help predict nontechnical risks and keep the community informed. In paper SPE 204901, which involves using renewable energy sources for offshore oil and gas platform power generation, one operator proposes harnessing wind energy in weak-wind areas by replacing gas-turbine generators with offshore wind turbines adapted to low-wind-speed regions, thereby lowering maintenance costs and carbon exposure. In paper OTC 31394, a service company, acting as project management lead, and an operator collaborate to use fully electrified equipment to abandon wells in sensitive areas such as urban and natural settings where smell and noise are significant issues. In paper OTC 32481, an operator advocates the use of underwater intervention/inspection drones for offshore projects and describes their advantages, including operational risk reduction, lower carbon footprint, lower costs, reduced intervention time, and improved quality and frequency of inspection data. One of the recommended-reading papers, SPE 210788, describes how an operator advocates for mental health or “mental hygiene,” a “preventive measure for sustaining good emotional health” to mitigate workers’ distress in the oil and gas industry and an indication of the growing emphasis upon total wellness. Many more examples of recent notable achievements in HSES can be found in the list of recommended additional reading and in the OnePetro online library. Knowledge sharing, on the local and global levels, encourages collaboration and solutions generation. See the SPE Health, Safety, Environment and Sustainability website for more information and to learn how you could be involved. Recommended additional reading at OnePetro: www.onepetro.org. SPE 210788 Shifting Paradigm of Mental Hygiene—A Novel Approach To Mitigate Workers’ Distress in the Oil and Gas Industry by Adeela Khalid, RPM, et al. SPE 212791 An Improved Work Flow in Mass-Balance Approach for Estimating Regional Methane Emission Rate Using Satellite Measurements by Jeffrey Y. Bian, University of Alberta, et al. SPE 210245 Insights From Benchmarking Methane Emissions of Oil and Natural Gas Production in the United States by Tom Curry, ERM, et al.

Controlled-release testing of the static chamber methodology for direct measurements of methane emissions

Abstract. Direct measurements of methane emissions at the component level provide the level of detail necessary for the development of actionable mitigation strategies. As such, there is a need to understand the magnitude of component-level methane emission sources and to test methane quantification methods that can capture methane emissions at the component level used in national inventories. The static chamber method is a direct measurement technique that has been applied to measure large and complex methane sources, such as oil and gas infrastructure. In this work, we compile methane emission factors from the Intergovernmental Panel on Climate Change (IPCC) Emission Factor Database in order to understand the magnitude of component-level methane flow rates, review the tested flow rates and measurement techniques from 40 controlled-release experiments, and perform 64 controlled-release tests of the static chamber methodology with mass flow rates of 1.02, 10.2, 102, and 512 g h−1 of methane. We vary the leak properties, chamber shapes, chamber sizes, and use of fans to evaluate how these factors affect the accuracy of the static chamber method. We find that 99 % of the component-level methane emission rates from the IPCC Emission Factor Database are below 100 g h−1 and that 77 % of the previously available controlled-release experiments did not test for methane mass flow rates below 100 g h−1. We also find that the static chamber method quantified methane flow rates with an overall accuracy of +14/-14 % and that optimal chamber configurations (i.e., chamber shape, volume, and use of fans) can improve accuracy to below ±5 %. We note that smaller chambers (≤20 L) performed better than larger-volume chambers (≥20 L), regardless of the chamber shape or use of fans. However, we found that the use of fans can substantially increase the accuracy of larger chambers, especially at higher methane mass flow rates (≥100 g h−1). Overall, our findings can be used to engineer static chamber systems for future direct measurement campaigns targeting a wide range of sources, including landfills, sewerage utility holes, and oil and natural gas infrastructure.

Methane and Hydrocarbon Emission Rates from Oil and Gas Production in the Province of Basra, South of Iraq

Petroleum deposits typically contain a gaseous component known as “associated gas”. If associated gas is not collected or used on-site, it may be flared or vented as a byproduct of oil production. Flaring is preferential to venting in terms of global warming. Flaring oxidizes carbon and produces CO2, but by destroying methane and other hydrocarbons, it decreases the overall risk of global warming emissions. On a 100-year time scale, fossil methane is 36 times more potent than CO2. The measurements were taken at six oil fields (AlTuba, Allhais, Artawi, North Rumaila, Nahran Omar, and Majnoon) and two power plants (Alnajebia power plant and Shatt Al-Basra). To measure the concentrations of hydrocarbons, a direct measurement was taken for six months. ANOVA test was used to analyze the results at p ≤ 0.05 and a correlation between hydrocarbon concentrations, wind speed, and temperature was done. The result showed that the hydrocarbons were found in all stations, in all measurements with different concentrations except in Alnajebia and Shatt Al-Basra power plant at first measurements, the device did not detect hydrocarbons concentration. The highest average of hydrocarbon concentrations was at Allhais which was recorded as 995, 598.15, 418.7, 358.89 and 279.13 ppm for methane, ethane, propane, butane and pentane respectively. The lowest average was found at the majnoon oil field for methane, ethane, propane, butane and pentane 395, 238.8, 167.16, 142.2 and 111.4 ppm respectively. The relationship between the average hydrocarbon concentrations with the average monthly wind speed and with average monthly temperature was positive.

Carbon loss and emissions within a permafrost collapse chronosequence

Permafrost carbon release is potentially the largest terrestrial feedback contributing to climate change. However, the changes in carbon release caused by the abrupt thawing of permafrost and their controlling factors remain largely unknown. Here, we measured soil organic carbon (SOC), total nitrogen (TN) concentrations, and carbon dioxide (CO2) and methane (CH4) emission rates among seven permafrost collapse features over 3 years in the northern Qinghai-Tibetan Plateau (QTP). The results showed soil carbon and nitrogen loss caused by permafrost collapse ranged from − 12% to 28% and − 1% to 38%, respectively. We found there was a nonlinear relationship between soil carbon loss and permafrost collapse chronosequence. Permafrost collapse significantly reduced ecosystem respiration (Reco) and weakened carbon sinks. The net ecosystem exchange (NEE) decreased from − 2.59 to − 0.21 µmol CO2 m−2 s−1. The Reco and NEE values showed no significant changes over time after the initial permafrost collapse. In contrast, the CH4 fluxes increased over time following permafrost collapse, and the CH4 fluxes significantly increased 2 to 10 times in the exposed area compared with that in the control area. Soil temperature, moisture, and nutrient availability exerted the most controls over the carbon emission during permafrost collapse. This study provides the patterns of carbon loss and emissions in different permafrost collapse landscapes, which will provide deep insights and reliable data for future prediction of the abrupt thawing of permafrost-carbon feedback.

On the cost of zero carbon hydrogen: A techno-economic analysis of steam methane reforming with carbon capture and storage

This article challenges the view that zero carbon hydrogen from steam methane reforming (SMR) is prohibitively expensive and that the cost of CO2 capture increases exponentially as residual emissions approach zero; a flawed narrative often eliminating SMR produced hydrogen as a route to net zero. We show that the capture and geological storage of 100% of the fossil CO2 produced in a SMR is achievable with commercially available post-combustion capture technology and an open art solvent. The Levelised Cost of Hydrogen (LCOH) of 69£/MWhth HHV (2.7£/kg) for UK production remains competitive to other forms of low carbon hydrogen, but retains a hydrogen lifecycle carbon intensity of 5 gCO2e/MJ (LHV) due to natural gas supply chain and embodied greenhouse gas (GHG) emissions. Compensating for the remaining lifecycle GHG emissions via Direct Air Capture with geological CO2 Storage (DACCS) increases the LCOH to 71–86 £/MWhth HHV (+3–25%) for a cost estimate of 100–1000 £/tCO2 for DACCS and the 2022 UK natural gas supply chain methane emission rates. Finally, we put in perspective the cost of CO2 avoidance of fuel switching from natural gas to hydrogen with long term price estimates for natural gas use and DACCS, and hydrogen produced from electrolysis.

Effect of Covering Deep Litter Stockpiles on Methane and Ammonia Emissions Analyzed by an Inverse Dispersion Method

Ammonia (NH3) and methane (CH4) emission rates from cattle deep litter and horse manure deep litter in farm-scale stockpiles were measured using an inverse dispersion method based on the backward Lagrangian Stochastic (bLS) model. The aims of the study were to (i) evaluate the effects of timing and carefulness of covering a stockpile, (ii) measure emissions from handling and storing deep litter, (iii) compare emissions from manure stored in a container and stockpile, (iv) determine emissions from cattle and horse manure deep litter, and (v) evaluate potential effects of pile temperature on emissions. New emission data with relatively high temporal resolution are provided. High variability in CH4 emissions was observed with no clear effects on the timing of covering, even though the temperatures inside the piles were different. NH3 emissions occur immediately after pile establishment and the emissions were highly influenced by the timing of covering. In the first week of storage, covering reduced NH3 emissions by 92 ± 9% when comparing the emissions from a noncovered and totally covered stockpile. This demonstrates the effect of applying a cover immediately to avoid NH3 emissions. The long-term effects of covering strategies as well as the influence of temperature and season are also discussed. For horse manure deep litter, storage in a closed (covered) container instead of a covered stockpile was observed to reduce CH4 emissions by 50 ± 58% and NH3 emissions by 67 ± 37%.

Tiered Leak Detection and Repair Programs at Simulated Oil and Gas Production Facilities: Increasing Emission Reduction by Targeting High-Emitting Sources.

Distributions of methane emission rates originating from oil and gas production facilities are highly skewed and span 6-8 orders of magnitude. Traditional leak detection and repair programs have relied on surveys with handheld detectors at intervals of 2 to 4 times a year to find and fix emissions; however, this approach may lead unintended emissions to be active for the same interval independently of their magnitude. In addition, manual surveys are labor intensive. Novel methane detection technologies offer opportunities to further reduce emissions by quickly detecting the high-emitters, which account for a disproportionate fraction of total emissions. In this work, combinations of methane detection technologies with a focus of targeting high-emitting sources were simulated in a tiered approach for facilities representative of the Permian Basin, a region with skewed emission rates where emissions above 100 kg/h account for 40-80% of production site-wide total emissions, which include sensors on satellites, aircraft, continuous monitors, and optical gas imaging (OGI) cameras, with variations on survey frequency, detection thresholds, and repair times. Results show that strategies that quickly detect and fix high-emitting sources while decreasing the frequency of OGI inspections, which find the smaller emissions, achieve higher reductions than quarterly OGI and, in some cases, reduce emissions further than monthly OGI.

Characterizing methane emissions from orphaned coalbed methane wells in the powder river basin

In 2018, the U.S. EPA Greenhouse Gas Inventory (GHGI) began including methane emissions from abandoned oil and gas (AOG) wells and estimated that they may constitute up to 4% of total methane emissions from the oil and gas sector. Several studies have shown that these emissions vary by location which introduces regionally dependent uncertainty into inventory estimates. In Wyoming, there are over 1000 wells identified as ‘orphaned’ indicating that they are both abandoned and unplugged, approximately 80% of which are coalbed methane (CBM) wells. In this pilot study, 3-hour measurements of ten orphaned CBM wells were taken to support the characterization of AOG well emission rates in the Powder River Basin (PRB) in Wyoming. The mean methane emission rate measured at these wells was 653 mg CH4/hr with the majority of these wells emitting in the 100-1000mg CH4/hr range. The highest emitting well in the study was measured at 4.53 g CH4/hr. Compared to the GHGI AOG wells emission factor of 10.04 g CH4/hr, these findings suggest that AOG wells emission rate in the PRB are overestimated by national inventory methods. Finally, the addition of AOG well emissions data from this study doubles the number of sampled AOG wells in Wyoming and triples the number of sampled CBM wells in the U.S.

Evaluation of open- and closed-path sampling systems for the determination of emission rates of NH3 and CH4 with inverse dispersion modeling

Abstract. The gas emission rates of ammonia (NH3) and methane (CH4) from an artificial source covering a surface area of 254 m2 were determined by inverse dispersion modeling (IDM) from point-sampling and line-integrated concentration measurements with closed- and open-path analyzers. Eight controlled release experiments were conducted with different release rates ranging from 3.8±0.21 to 17.4±0.4 mg s−1 and from 30.7±1.4 to 142.8±2.9 mg s−1 for NH3 and CH4, respectively. The distance between the source and concentration measurement positions ranged from 15 to 60 m. Our study consisted of more than 200 fluxes averaged over intervals of 10 or 15 min. The different releases cover a range of different climate conditions: cold (<5 ∘C), temperate (<13 ∘C), and warm (<18 ∘C). As the average of all releases with all instrument types, the CH4 recovery rate QbLS/Q was 0.95±0.08 (n=19). There was much more variation in the recovery of NH3, with an average of 0.66±0.15 (n=10) for all the releases with the line-integrated system. However, with an improved sampling line placed close to the source an average recovery rate of 0.82±0.05 (n=3) was obtained for NH3. Under comparable conditions, the recovery rate obtained with an open-path analyzer was 0.91±0.07 (n=3). The effects of measurement distance, physical properties of the sampling line, and deposition are discussed.

Estimasi Produksi Gas Metana Untuk Pemanfaatan Sebagai Sumber Energi Di TPA Talang Gulo, Jambi

Landfills (TPA) are a significant source of methane emissions into the atmosphere. In Indonesia, the estimation of methane gas production from a landfill has not been widely carried out. The purpose of this research is to measure production and measure the concentration of methane gas emitted into the atmosphere, assess methane gas emissions as an energy source, and analyze the potential costs and benefits of electrical energy that can be generated from methane gas emissions at the Talang Gulo TPA. The emission data obtained can be used as material for analysis to create a project for developing a gas processing system from a landfill. This estimation approach is carried out in three ways, namely prediction with LandGEM-v302 software, field measurements with methane flux and utilization of methane gas production as an energy source. The LandGEM-v302 simulation results obtained a total landfill gas of 29.96 Gg/year consisting of CH4 of 8.002 Gg/year, CO2 of 21.96 Gg/year and NMOC (non-methane organic compounds) of 0.344 Gg/year. The results of field measurements on the surface of the closed chamber TPA obtained CH4 emissions from TPA Talang Gulo of 4.75 Mg/year. The different characteristics of the landfill surface greatly affect the gas emissions released into the atmosphere. Moisture conditions or water content in the waste also affect the methane emission rate. The electricity potential from methane gas is 15.718 MW so that the cost benefit analysis shows an NPV of Rp. 6,028,622,852.18, B/C Ratio of 0.00196 and IRR of 2.445%.

Forage type affects the temporal methane emission profiles in dairy cows fed fresh forages

Methane (CH4) emission rates increase after feeding till a peak and then decrease until the next feeding. Understanding the CH4 emission patterns when animals are fed different forages and the drivers for variation in temporal CH4 emission may be a tool for using short-lived CH4 inhibitors efficiently in grazing systems when fed during milking only. The objectives of this study were: a) to compare the temporal CH4 emission profile of non-lactating cows fed plantain or ryegrass and, b) evaluate the relationship between feed nutrient intake and dry matter intake rate, with CH4 emissions accumulated during the first 3 h after feeding as a percentage of 24 h CH4 emissions. After the CH4 emissions peaked, they decreased more rapidly in PLT compared to RG fed cows. The cumulative CH4 emissions during the first 3 h after feeding as a percentage of 24 h emissions was 18 % greater in PLT than in RG fed cows, and 13 % greater in the afternoon compared to the morning. The soluble sugars concentration in the forage was the only feed feature with significant effect on the cumulative CH4 emissions during the first 3 h after feed delivery, whereas there was no relationship with dry matter intake during the first 3 h after feeding. In grazing systems forages resulting in greater CH4 emissions during the first 3 h after feeding as a percentage of 24 h emissions would be more suitable to be combined with short lifespan CH4 inhibitors.

Manganese Slag Amendment Reduces Greenhouse Gas Emissions from Paddy Soil

Increasing crop productivity and minimizing greenhouse gas emissions from paddy fields are increasingly receiving attention. Slag application not only can maximize the use of solid wastes as beneficial resources for agricultural production, but it also reduces greenhouse gas emissions. In order to determine the most effective slags as soil amendments for greenhouse gas emission reduction, three major slags, i.e., steel, titanium and manganese slags, were applied as soil amendments to paddy soils; correspondingly, the greenhouse gas emissions, cumulative emissions and global warming potential of the soils during one growing season were measured. It was found that applying all these three slags could reduce the methane emission rates and the cumulative methane emissions. Manganese slag significantly decreased methane emissions by 55% compared with the control. Carbon dioxide caused no significant changes among different slag treatments; however, the cumulative carbon dioxide emissions from fields treated with steel and manganese slags were lower than those from control fields. The global warming potential of paddy soil with manganese application was 63% lower than that of the control. Finally, manganese oxide was found to have a negative relation with greenhouse gas emissions. It was inferred that the electron acceptors and the photocatalysis of manganese oxide minerals might have been the main reasons for greenhouse gas reduction. This preliminary result could be further applied to utilizing solid wastes as beneficial resources and to developing carbon fixation and greenhouse gas reduction fertilizers.

Estimation Effect of Weather Factors on Biogas Emissions Rate (Methane) from Landfill Stations in Baghdad, Iraq

The topic of this study examines the release of methane gas from the landfill stations in the Baghdad Governorate, the biological decomposition and anaerobic decomposition (absence oxygen) breakdown of garbage, after the garbage is buried in the landfill stations. The objective of this research is to estimate the methane (CH4) emission rate, from landfill stations ineffective weather factors such as (temperature, wind speed and direction), and also the possibility of using it as a source of sustainable energy in Baghdad Governorate. Garbage was collected in nine congregational stations, located on both sides of Karkh and Rusafa. Through study the period from 2016 to 2018, the highest methane emission rate was 0.046 GgYr-1 in 2018, and the lowest methane emission rate was 0.0077GgYr-1 in 2017, while the annual total municipal solid waste (MSW) was 2421808m3 and 407665m3 respectively. The results also showed a monthly greatest amount of methane emission rate occurred in July and August at a rate 0.003 Gg/ month with average temperatures of 36Co and average wind speed of 4.3 m/s, while the lowest occurred in January and February at a rate 0.001Gg/month, with an average temperature of 11Co and average wind speed of 3 m/s, the prevailing wind direction is about 270o-337.5o. By converting municipal solid waste disposal sites (open dumps) to sanitary landfills with methane collection and utilization facilities. The methane from the garbage disposal sites can be used as a sustainable energy source to generate electrical energy estimated years 2016, 2017 and 2018, from the methane emission rate of about 57.666 kW/h -105.661kW/h.

Emissions rate measurement with flow modelling to optimize landfill gas collection from horizontal collectors

A two-dimensional landfill gas flow model using the FEFLOW numerical code was developed to assess the potential improvement in landfill gas (LFG) collection and the reduction in greenhouse gas emissions at a landfill due to increases in the vacuum of horizontal collectors and/or installation of additional LFG collection infrastructure. A key calibration input parameter for the model, the fugitive methane emission rate from the study area, was measured using the airborne matter mapping method. The measurement showed that, at the time, the methane collection efficiency for the study area was approximately 37 %. The model indicated that increasing the vacuum of the existing collection system by 0.75 kPa could result in an improvement in collection efficiency from 37 % to 49 % within the selected study area. A similar increase of collection efficiency could be obtained by either doubling the number of horizontal collectors on a platform or installing a layer of permeable demolition waste on that level, without an increase in collection system vacuum. Combining the addition of collection infrastructure with an increase in collection system vacuum by 1 kPa was predicted to improve the collection efficiency for the study area to about 74 %.

Quantification of methane emission rate from oil and gas wells in Romania using ground-based measurement techniques

The ROMEO campaign (ROmanian Methane Emissions from Oil and gas) focused on measurements of methane (CH4) emission rates from oil and natural gas (O&G) production in Romania. The campaign took place in October 2019 and covered the southern part of Romania around the cities Bucharest, Ploiesti, Pitesti, and Craiova. This study presents emission rates calculated from mobile in situ measurement of CH4 and wind measurements using the Other Test Method 33a from U.S. Environmental Protection Agency and the Gaussian Plume Method. These methods were used to determine emission rates from 112 O&G well sites and other production-related facilities. Estimated mean CH4 emission rate with a 95% confidence interval equals 0.49 [0.35, 0.71] kg CH4 h−1 per site; 10% of all quantified sites account for 56% of the estimated emission rates. In addition, more than 1,000 O&G sites were visited for a qualitative “screening” (CH4 detection without quantification). Analysis of the screening data shows that 65% of the sites emitted methane at detectable rates. The CH4 emission rates obtained during the ROMEO campaign are comparable to the methane emission rates in study carried out in other Romanian regions.

Retrieving CH4-emission rates from coal mine ventilation shafts using UAV-based AirCore observations and the genetic algorithm–interior point penalty function (GA-IPPF) model

Abstract. There are plenty of monitoring methods to quantify gas emission rates based on gas concentration measurements around the strong sources. However, there is a lack of quantitative models to evaluate methane emission rates from coal mines with less prior information. In this study, we develop a genetic algorithm–interior point penalty function (GA-IPPF) model to calculate the emission rates of large point sources of CH4 based on concentration samples. This model can provide optimized dispersion parameters and self-calibration, thus lowering the requirements for auxiliary data accuracy. During the Carbon Dioxide and Methane Mission (CoMet) pre-campaign, we retrieve CH4-emission rates from a ventilation shaft in Pniówek coal mine (Silesia coal mining region, Poland) based on the data collected by an unmanned aerial vehicle (UAV)-based AirCore system and a GA-IPPF model. The concerned CH4-emission rates are variable even on a single day, ranging from 621.3 ± 19.8 to 1452.4 ± 60.5 kg h−1 on 18 August 2017 and from 348.4 ± 12.1 to 1478.4 ± 50.3 kg h−1 on 21 August 2017. Results show that CH4 concentration data reconstructed by the retrieved parameters are highly consistent with the measured ones. Meanwhile, we demonstrate the application of GA-IPPF in three gas control release experiments, and the accuracies of retrieved gas emission rates are better than 95.0 %. This study indicates that the GA-IPPF model can quantify the CH4-emission rates from strong point sources with high accuracy.