Satellite observations of enhanced atmospheric methane removal

Abstract

The invention provides a method for evaluating enhanced atmospheric methane oxidation in a tropospheric space (500) above an ocean or a sea and induced by a target object (400) using satellite data, wherein the method comprises: (i) comparing satellite data from at least part of the tropospheric space (500) for an indicator species (1) related to enhanced atmospheric methane oxidation with reference data for the indicator species (1), wherein the indicator species (1) is not methane; and (ii) evaluating the enhanced atmospheric methane oxidation induced by the target object based on a comparison of the satellite data and the reference data.

Description

[0001] Satellite observations of enhanced atmospheric methane removal

[0002] FIELD OF THE INVENTION

[0003] The invention relates to a method for evaluating enhanced atmospheric methane oxidation. The invention further relates to an enhanced atmospheric methane oxidation evaluation system. The invention further relates to a computer program product comprising instructions to carry out the method of the invention.

[0004] BACKGROUND OF THE INVENTION

[0005] Methods for evaluating atmospheric methane are known in the art. For instance, WO2019068178A1, describes a method for tracking at least one emission type generated by an entity, the entity generating one or more emissions types including the at least one emission type, the method comprising: receiving a first emission data associated with the at least one emission type at a first time; analyzing the first emission data received at the first time to determine a first emission output value designated as an emission baseline; recommending at least one emission reduction step corresponding to the at least one emission type; receiving a second emission data associated with the at least one emission type at a second time, wherein the second emission data is received after implementation of the at least one emission reduction step; analyzing the second emission data received at the second time to determine a second emission output value; and determining an emission offset measurement corresponding to the at least one emission type based on the emission baseline and the second emission output value.

[0006] Riess Tobias Christoph et al (2022): “Improved monitoring of shipping NO2 with TROPOMI: decreasing NOx emissions in European seas during COVID-19 pandemic”, Atmospheric Measurement Techniques, vol. 15, nr. 5, describes the demonstration of TROPOMI's capability to detect shipping emissions applying a typical data selection and comparing it to OMI's. Additionally, the FRESCO+ wide cloud pressure retrieval and its impact on the TROPOMI NO2 columns is evaluated in vl.4-2.1 of the operational TROPOMI NO2 algorithm. Based on the findings, a data set of historical TROPOMI NO2 columns consistent with the v 1.4 data was created. Finally, the effects of the CO VID- 19 pandemic on ship pollution were quantified using the data set.

[0007] Holmes C. D. et al (2014): “The climate impact of ship NOXemissions: an improved estimate accounting for plume chemistry”, Atmospheric Chemistry and Physics, vol.

[0008] 14, nr. 13, describes parametric representation of exhaust-gas chemistry developed in the GEOS-Chem chemical transport model (CTM) to provide an estimate of RF from shipping thataccounts for sub-grid-scale ship plume chemistry. The CTM is described to calculate O3 production and CH4 loss both within and outside the exhaust plumes and also accounts for the effect of wind speed.

[0009] Prados-Roman C. et al (2020): “Atmospheric formaldehyde at El Teide and Pic du Midi remote high-altitude sites”, Atmospheric Environment, vol. 234, nr. 117618, describes assessment of the presence of CH2O at two high-altitude remote sites: El Teide (TEI, 3570 m a.s.l., Tenerife, Canary Islands. Spain) and Pic du Midi (PDM, 2877 m a.s.L, French Pyrenees) using ground-based remote sensing measurements.

[0010] Chen Yujia et al (2021): “Kilometer-level glyoxal retrieval via satellite for anthropogenic volatile organic compound emission source and secondary organic aerosol formation identification”, Remote Sensing of Environment, vol. 270, nr. 112852, describes utilization of satellite observations of glyoxal to identify anthropogenic VOC sources, which can be utilized to formulate pollution control policies.

[0011] SUMMARY OF THE INVENTION

[0012] Atmospheric methane removal is one category of "negative emissions technologies" being explored as part of efforts to achieve net-zero greenhouse gas emissions. Some of the key challenges surrounding the implementation of atmospheric methane removal include measurement, reporting, monitoring and verification for which the state of the art tools and / or capabilities appear to be lacking still.

[0013] Satellite observations are a proven method for monitoring emission of air pollution and greenhouse gases, supporting policy makers in e.g. the international drive to reduce global methane (CH4) emissions. The capacity to globally map concentrations cannot be matched by other means. E.g., the TROPOspheric Monitoring Instrument (TROPOMI) - one of the currently most advanced satellite instruments for atmospheric composition monitoring - is being used for monitoring emissions like CH4, NO2, CO, HCHO and SO2 from continental scales down to the scale of oil and gas infrastructure.

[0014] Besides CH emissions reduction, atmospheric CH4 removal approaches may address increasing natural CH4 emissions, as well as anthropogenic CH4 emissions that cannot be mitigated with technology. Potential open-system atmospheric CH4 removal approaches have been suggested, including enhancing oxidizing radicals in the atmosphere, methanotrophy in the biosphere and coating surfaces with photocatalysts.The most studied approach to enhance oxidizing radicals in the atmosphere is the use of iron salt aerosols (ISA), in which iron-based particles are lofted into the atmosphere to catalytically generate chlorine radicals that oxidize methane.

[0015] If proven to be climate beneficial and cost-effective, open-system approaches, particularly atmospheric oxidation enhancement, likely may have the largest potential scale and fastest time to scale. However, open-systems may also be tougher to verify and have higher risks of unintended consequences, and therefore require strong governance approaches. Such governance requires quantification and observations to verify any hypothetical future methane removal. For methane emission estimates, satellite -based observations have shown to be better suited to do these observations than local observations. However, a problem may be how to observe enhanced atmospheric methane oxidation using satellite observations above the ocean. Due to technical limitations direct satellite CH4 observations are not available over the oceans, where proposed open-system approaches are envisioned to operate. Methane (CH4) may be measured by satellite instruments such as TROPOMI in the short-wave infrared (SWIR) spectral region, typically around 2300-2400 nm, where absorption features of methane may be strong. Trace-gas retrievals in this spectral range may rely primarily on sunlight reflected by the Earth’s surface. Over ocean surfaces, however, water exhibits very low reflectance in the SWIR, except under specific sun- glint geometries. As a result, the measured radiance may be weak, leading to a low signal-to-noise ratio that may severely limit retrieval of methane columns over most ocean surfaces. Consequently, methane products from SWIR sensors may generally be restricted to land surfaces or special ocean-glint conditions. Such limitation may be fundamentally spectral-band dependent and therefore may not necessarily apply to trace-gas retrievals performed in other wavelength regions. In particular, several reactive trace gases may be retrieved in the near-ultraviolet (UV), where the measured signal may be dominated not by surface reflection alone but by atmospheric backscattering (Rayleigh scattering) and Earthshine. In this spectral region, ocean surfaces may provide sufficient radiance for trace-gas detection despite their low albedo.

[0016] A prominent example may be formaldehyde (HCHO), which may be retrieved using differential optical absorption spectroscopy (DOAS) in the 320-360 nm spectral window. In this range, the combination of molecular scattering in the atmosphere and moderate ocean reflectivity may enable robust HCHO retrievals over both land and ocean. As a result, satellite HCHO products may routinely include oceanic regions.A similar situation may apply to formic acid (HCOOH), which may be retrieved in the near-UV spectral range using absorption features overlapping those of HCHO. Global satellite retrievals of HCOOH developed by International Institute for Applied Systems Analysis (IIASA) exploit this UV window, allowing observations over oceans as well as land. Because HCOOH retrievals rely on UV backscattered radiation rather than SWIR surface reflection, they may not be subject to the same ocean-related limitations that affect methane.

[0017] One could thus imagine the use of indirect indicators for CH4 oxidation. For instance, formaldehyde (HCHO or CH2O) might be applied. However, formaldehyde may have the problem that it is not only produced from CH4 oxidation, but may also have other sources, such as for example biomass burning emissions, or NOx emissions by ships, which could be falsely identified as enhanced methane oxidation (induced by a target object).

[0018] Hence, it is an aspect of the invention to provide an alternative method for evaluating enhanced atmospheric methane oxidation, which preferably further at least partly obviates one or more of above-described drawbacks. The present invention may have as object to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative.

[0019] According to a first aspect, the invention provides a method, such as especially a computer- implemented method, for evaluating enhanced atmospheric methane oxidation in a tropospheric space above an ocean or a sea using satellite data. In embodiments, the enhanced atmospheric methane oxidation may especially be induced by a target object, for example due to a local emission of an enhancing compound configured to enhance atmospheric methane oxidation. In embodiments, the method may especially comprise (a (collecting) stage comprising) collecting satellite data from at least part of the tropospheric space for an indicator species (different from the enhancing compound) related to enhanced atmospheric methane oxidation. Especially, in embodiments, the indicator species may not be methane (i.e., a nonmethane indicator species). Further, in embodiments, the method may comprise (a (comparing) stage comprising) comparing the satellite data from at least part of the tropospheric space for the indicator species with reference data for the indicator species. Yet further, in embodiments, the method may comprise evaluating the enhanced atmospheric methane oxidation induced by the target object based on a comparison of the satellite data and the reference data. Herein, a comparison of the satellite data and the reference data may also be indicated as “compared satellite data”.

[0020] Hence, in an aspect the invention (also) provides a (computer-implemented) method for evaluating enhanced atmospheric methane oxidation in a tropospheric space abovean ocean or a sea and induced by a target object using satellite data, wherein the method may comprise: (a (comparing) stage comprising) (i) comparing satellite data from at least part of the tropospheric space for an indicator species (different from the enhancing compound) related to enhanced atmospheric methane oxidation with reference data for the indicator species, wherein the indicator species is not methane; and (a (evaluating) stage comprising) (ii) evaluating the enhanced atmospheric methane oxidation induced by the target object based on a comparison of the satellite data and the reference data. Hence, the indicator species may also be indicated as “non-methane indicator species”. Note, however that, though the indicator species may not be methane, it may be an (non-methane) indicator for methane oxidation.

[0021] This invention thus may provide a method to observe enhanced atmospheric methane oxidation using satellite observations. Especially, the method of the invention may use satellite observations of indicator species that are related to methane oxidation, and can be detected over ocean regions. Subsequently, the method of the invention may comprise comparing these satellite observations with either modelled data or with a referral species, to account for other sources of the indicator species. Preferably, in embodiments, the observation of formaldehyde (HCHO) or formic acid (HCOOH or CH2O2) may be used to observe enhanced atmospheric methane oxidation. In specific embodiments, enhanced methane oxidation may be detected by comparing modelled and observed measurements, or by using changes in tracertracer ratios. Such embodiments may be beneficial as satellite detection of the indicator species for methane removal may be available over the ocean and the sea, where satellite detection of methane itself is hindered. Therewith, the method of the invention may enable effective, facile, and high-scale quantification of methane removal as a result of atmospheric methane oxidation.

[0022] In an aspect of the invention, the method may comprise (a) collecting data relating to a target object using a remote monitoring device, such as a satellite, (b) comparing the collected data to reference data, and (c) evaluating the enhanced atmospheric methane oxidation induced by the target object based on a comparison of the remote monitoring data and the reference data. Hence, the method may provide a result or resulting conclusion with respect to enhanced atmospheric methane oxidation (induced by the target object) (through evaluation thereof) based on the comparison of the remote monitoring data and the reference data. As described above, in embodiments, the collection step may be executed using a remote monitoring device such as e.g. a satellite, a drone, or an aircraft (see also further below). Further, in embodiments, the comparison and evaluation stage may be executed using advanced data processing systems, such as computer systems. Accordingly, the invention may provide acomputer-implemented method. The term “computer-implemented method” herein refers to a method that is carried out by a computer system (or “data processing system”), particularly wherein the computer system carries out one or more steps of the method, such as all steps of the method. The computer-implemented method may, for brevity, hereinafter also be referred to as “the method”. The term “remote monitoring device” may also refer to a plurality of remote monitoring devices (which may all be the same or which may include two or more different types of remote monitoring device).

[0023] Instead of using satellite data, in embodiments, the method may also comprise evaluating enhanced atmospheric methane oxidation in the tropospheric space above an ocean or a sea using remote monitoring data. In embodiments, the remote monitoring data may for example be collected using an aircraft (i.e. aircraft data), such as aircraft mounted with (i) a hyperspectral, (ii) a multispectral imaging device, or (iii) an imaging spectroscopy device such as a spectrograph. Alternatively, in embodiments, the remote monitoring data may be collected using a drone (i.e. drone data). Alternatively, the remote monitoring data may be collected using a drone (or unmanned aerial vehicles UAVs), such as a drone mounted with (i) a hyperspectral, (ii) a multispectral imaging device, or (iii) an imaging spectroscopy device such as a spectrograph. When using one or more drones, in general these will be aerial vehicles, though sea drones are herein not excluded). Hence, in embodiments, the remote monitoring data comprises data collected using one or more of a satellite, an aircraft, and a drone.

[0024] The term “remote monitoring data” may thus also be referred to as aerial remote monitoring data, or overhead remote monitoring data (referring to the location of the data collection device being above the target object). The use of an aircraft or a drone may provide the advantage that higher spatial resolution in comparison to the use of a satellite, while additionally having more flexibility in the time-of-day for collecting the data. Conversely, an advantage of the use of satellites over aircrafts or drones may be that satellites are relatively cheaper for routine monitoring application and have (e.g. compared to drones) less limits to their spatial range as satellites may cover a large area, for example scanning the entire globe every day, but at a lower spatial resolution. For open-system atmospheric methane enhancement the region to be monitored may typically be very large, making satellites especially suited for the task. Hence, in embodiments, the method for evaluating enhanced atmospheric methane oxidation in a tropospheric space above an ocean or a sea and induced by a target object may comprise using remote monitoring data, wherein the method may comprise: (i) comparing remote monitoring data from at least part of the tropospheric space for an indicator species related to enhanced atmospheric methane oxidation with reference data forthe indicator species, wherein the indicator species may not be methane; and (ii) evaluating the enhanced atmospheric methane oxidation induced by the target object based on a comparison of the remote monitoring data and the reference data. In embodiments, the remote monitoring data may comprise data collected using one or more of a satellite (i.e. satellite data), an aircraft, and a drone. In specific embodiments, the remote monitoring data may comprise satellite data. In alternative specific embodiments, the remote monitoring data may comprise aerial remote monitoring data, or overhead remote monitoring data. However, also a combination of using satellite data and using (other) remote monitoring data may be applied.

[0025] The invention may thus provide a method for evaluating enhanced atmospheric methane oxidation in a tropospheric space above an ocean or a sea and induced by a target object using remote monitoring data, such as especially satellite data.

[0026] The term “atmospheric methane oxidation” may refer to the breakdown of methane present in the atmosphere. Methane has a limited atmospheric lifetime, about 10 years, due to substantial methane sinks. The primary methane sink may be atmospheric oxidation, from hydroxyl radicals and chlorine radicals. The rest of the atmospheric methane may be primarily consumed by methanotrophs and other methane-oxidizing bacteria and archaea in soils. Herein, enhanced atmospheric methane oxidation may especially refer to a category of approaches to accelerate such breakdown of methane present in the atmosphere, for the purpose of further mitigating some of the impacts of climate change.

[0027] In embodiments, the enhanced atmospheric methane oxidation may be due to a local emission of an enhancing compound. For example, in embodiments, the enhanced atmospheric methane oxidation may be due to a local emission of an enhancing compound from the target object Especially, in such embodiments, the enhancing compound may comprise a compound that enhances atmospheric methane oxidation. More especially, in embodiments, the target object may (be configured to) enhance atmospheric methane oxidation by locally increasing the concentration of Cl atoms through the emission of the enhancing compound.

[0028] Methane may be naturally oxidized by a radical called hydroxyl (OH), resulting in an atmospheric lifetime of about 10 years for methane. The source of OH may be ozone (O3), and the source of the ozone may be NOx, in the presence of sunlight and fuel such as a hydrocarbon or CO. Herein, NOx may be defined as the sum of NO + NO2 + NO3. By increasing the concentration of NOx in the air, the natural atmospheric methane oxidation process may be enhanced. Therefore, in embodiments, the enhancing compound may comprise NOx, such as one or more of NO, NO2, and NO3. However, the use of such compounds as the enhancing compound may be disadvantageous as NOx comprises relatively polluting nitrogen oxides,which gases contribute to the formation of smog and acid rain. Hence, in embodiments, the enhancing compound may preferably not be NOx.

[0029] Further, when chlorine (Ch) gas is (directly) added to the atmosphere, it may generate Cl radicals (or chlorine atoms) that can similarly oxidize methane, and thus also enhance the natural methane oxidation. Hence, in embodiments, the enhancing compound may comprise Ch. Alternatively, in embodiments, the enhancing compound may comprise a compound configured to (indirectly) release Ch into the air. For example, the (direct) release of iron into the atmosphere may result in the production of Ch (indirectly) via iron-salt aerosol formation. Hence, by lofting Iron Salt Aerosols (ISA) into the atmosphere, chlorine radicals may be catalytically generated through photocatalytic oxidation and reduction of Fe(II) and Fe(III) chlorides (mixed with NaCl salt) to produce Ch gas in the atmosphere, which may oxidize methane. Hence, in embodiments, the enhancing compound may comprise an iron-salt aerosol. Alternatively, in embodiments, the enhancing compound may comprise another compound configured to (indirectly) release CI2 into the air, such as a compound selected from the group comprising a chloride salt (such as e.g. sodium hypochlorite), an iron-comprising compound, an iron-chloride comprising compound, and a chlorine-comprising compound.

[0030] By emitting the enhancing compound in the vicinity of a methane source, such as a methane-fueled vessel, the atmospheric removal of methane may be locally enhanced. Hence, in embodiments, the enhancing compound may be emitted locally, especially local with respect to a methane source or a target object.

[0031] Especially, in embodiments, the enhancing compound may be emitted locally with respect to a target object. By emitting the enhancing compound, the target object may be configured to facilitate emission data relating to the, such as e.g. information concerning type of enhancing compound and concentrations or amount of the enhancing compound being emitted. Such data relating to the enhancing compound may especially be made publicly available. As such, the data relating to the enhancing compound may be accessible to a given authority of a given country. Especially, in embodiments, the data relating to the enhancing compound may be accessible to a given authority of a given country if at least one of the following conditions is satisfied: (i) the target object (e.g. a ship) is of the same nationality as these authorities, (ii) the target object (e.g. a ship) is in the territorial waters of these authorities, and (iii) the target object’s destination is a port of the given country and the target object (e.g. a ship) is close to its final destination. Herein, the term “territorial waters” may especially refer to the waters extending up to 12 nautical miles from a coastal country's baselines.In a further aspect, the invention may provide a method for controlling enhanced atmospheric methane oxidation. Especially, the method may be for controlling enhanced atmospheric methane oxidation in a tropospheric space above an ocean or a sea. Additionally, the method may be for controlling enhanced atmospheric methane oxidation induced by a target object as described herein. Hence, in embodiments, the invention may provide a method for controlling enhanced atmospheric methane oxidation (i) in a tropospheric space above an ocean or a sea, and (ii) induced by a target object as described herein.

[0032] The method may especially comprise controlling emission of an enhancing compound as defined above from the target object. For example, the method may comprise changing one or more of an emission rate, an emission amount or concentration, and an emission duration of the enhancing compound into the tropospheric space. Such control of the emission of the enhancing compound may be based on the evaluation of enhanced atmospheric methane oxidation resulting from the computer-implemented method as defined herein. Hence, in embodiments, the invention may provide a method for controlling enhanced atmospheric methane oxidation (i) in a tropospheric space above an ocean or a sea and (ii) induced by the target object, the method comprising: controlling emission from the target object of an enhancing compound in dependence of the evaluating (i.e. especially thus in dependence of the evaluation) of the enhanced atmospheric methane oxidation induced by the target object as defined herein. Especially, in embodiments, the emission from the target object may be controlled in dependence of a result from the evaluation of the enhanced atmospheric methane oxidation (induced by the target object) based on the comparison of the remote monitoring data and the reference data. For example, the method for evaluating enhanced atmospheric methane oxidation using remote monitoring data and the method for controlling enhanced atmospheric methane oxidation as described herein may be performed in consecutive manner, such as even in an alternating manner. As such, these two methods may synergistically be used together to create a feedback and / or feed forward loop.

[0033] Further, in such embodiments, the target object may comprise a vessel or a structure. The term “structure” may herein refer to a single structure, such as a single wind turbine or a single lighthouse. Alternatively, the term “structure” may also refer to a plurality of structures, or arrangement of structures, such as e.g. a field or arrangement of (multiple) (offshore) wind turbines.

[0034] The term “controlling” and similar terms especially refer at least to determining the behavior or supervising the running of an element. Hence, herein “controlling” and similar terms may e.g. refer to imposing behavior on the element, such as e.g. measuring, displaying,actuating, opening, shifting, changing temperature, etc.. Beyond that, the term “controlling” and similar terms may additionally include monitoring. Hence, the term “controlling” and similar terms may include imposing behavior on an element and monitoring the element. The controlling of the element can be done with a controller or “control system”. The controller and the element may thus at least temporarily, or permanently, functionally be coupled. The element may comprise the controller. The controller and element may be physically separated. Control can be done via wired and / or wireless control. The term “controller” may also refer to a plurality of different controllers, which especially are functionally coupled, and of which e.g. one controller may be a master controller and one or more others may be slave controllers. A controller may comprise or may be functionally coupled to a user interface.

[0035] The controller may be configured to provide at least the operational mode. Would other modes be available, the choice of such modes may be executed via a user interface, though other options, like executing a mode in dependence of a sensor signal or a (time) scheme, may also be possible. Hence, the controller may control in dependence of one or more of an input signal of a user interface, a sensor signal (of a sensor), and a timer. The term “timer” may refer to a clock and / or a predetermined time scheme. The controller may also be configured to receive and execute instructions from a remote control.

[0036] As described above, in embodiments, the enhancing compound may especially be emitted in the tropospheric space. Herein the term “tropospheric space” may especially refer to a volume or area defined in the troposphere, i.e., in the lowest layer of the atmosphere of earth (extending up to about 20 kilometers above the earth’s surface). Tn embodiments, the tropospheric space may especially be defined above an ocean or a sea. Herein, the terms “ocean” and “sea” may be defined as (relatively large) bodies of salt water, especially bodies of water as distinguished from the land and the air. Moreover, in embodiments, the tropospheric space may herein be defined as a space (or volume) directly over the sea surface and (the space) having a height (hi) (relative to the sea surface) selected from the range of 1-4 km, such as from the range of 1,5-3 km, such as about 2 km. Therewith, in embodiments, the tropospheric space may especially be defined within a marine boundary layer, i.e., within a part of the atmosphere that has direct contact with (and hence may be directly influenced by) the ocean (or sea). Hence, in embodiments, the enhancing compound may especially be emitted in a space directly over the sea surface and (the space) having a height of about 2 km. Note that the term “sea surface” may also refer to the surface of an ocean.

[0037] Moreover, in (other) embodiments, the enhancing compound may be emitted in a maritime region. Especially, in such embodiments, the enhancing compound may be emittedin a space above a virtual plane Vp at land, wherein the virtual plane is at sea-level. In such embodiments, the virtual plane Vp may be defined at land at 0 m height but within a shortest distance di of 3 km from an ocean or a sea, especially a shortest distance di of 2 km, such as a shortest distance di of 1,5 km, like a shortest distance di of 1 km. Hence, in embodiments, the enhancing compound may be emitted in a space above land but near the sea, i.e. in a coastal region (i.e. especially within at maximum 3 km from an ocean or sea). Hence, the term “maritime region” may refer to sea or ocean, and also to land within 3 km from an ocean or sea. The height (hi) of the tropospheric space over land (in a maritime region) is especially defined relative to sea level. Especially, in embodiments, the maritime region may refer to a region at maximum 3 km from the nearest sea surface.

[0038] In specific embodiments, the enhanced atmospheric methane oxidation may be due to a local emission of an enhancing compound that enhances atmospheric methane oxidation. Especially, in embodiments, the enhancing compound may enhance atmospheric methane oxidation by locally increasing the concentration of Cl atoms. More especially, in embodiments, the enhancing compound may comprise one (or more) of an iron salt aerosol, Ch (g), and sodium hypochlorite.

[0039] The method of the invention may, in embodiments, comprise (a stage comprising) collecting remote monitoring data from at least part of the tropospheric space for an indicator species. Especially, the method of the invention may, in embodiments, comprise (a stage comprising) collecting satellite data from at least part of the tropospheric space for an indicator species. The remote monitoring (such as satellite) data for the indicator species may be collected using a remote monitoring instrument (or remote monitoring system), such as one or more satellites and / or one or more drones.

[0040] In embodiments, the indicator species may be related to enhanced atmospheric methane oxidation. The indicator species may especially be selected from a species directly involved in a methane oxidation mechanism. The methane oxidation mechanism may herein especially be defined as the methane oxidation mechanism comprising oxidation of methane into carbon monoxide and / or carbon dioxide via one or more of methyl (CH3), methyl peroxy radical (CH3O2), formaldehyde (H2CO or HCHO) and formyl radical (HCO). The methane oxidation mechanism is highlighted further in Figure 3 (see below) and the respective section of the detailed description below. In embodiments, the indicator species may further be different from the enhancing compound. Further, in embodiments, the indicator species may not be methane. Hence, the indicator species may also be indicated as “non-methane indicatorspecies”. Note, however that, though the indicator species may not be methane, it may be an (non-methane) indicator for methane oxidation.

[0041] In embodiments, the indicator species may be directly involved in the oxidation of methane. Especially, in embodiments, the indicator species may be formaldehyde. Such embodiments may be beneficial as formaldehyde (H2CO) may be formed as part of the methane oxidation mechanism (see also further in Figure 3 and the respective section of the detailed description below). With an atmospheric loss rate of for example around 2.6 hours at peak sunlight for HCHO in the tropics, the lifetime may be 13 km at wind speed of 5 km / h. This means HCHO advantageously may be only locally enhanced close to the enhanced methane oxidation. Further, HCHO may be advantageous as an indicator species as it may be directly related to CH4 oxidation.

[0042] Furthermore, in embodiments, the indicator species may be indirectly involved in the oxidation of methane. For example, in embodiments, the indicator species may comprise formic acid, which may be formed from methyl peroxy radical (CH3O2) or formaldehyde (H2CO). Additionally or alternatively, in embodiments, the indicator species may comprise BrO, in which case Cl may react with its precursor O3 in the atmosphere, therewith decreasing the concentration of BrO. As methane also reacts with Cl in the atmosphere, the concentration of BrO may indirectly provide a sort of “proxy” indication of the atmospheric methane oxidation. Similarly, in embodiments, the indicator species may comprise glyoxal (CHOCHO or C2H2O2), which may be formed from oxidation of larger hydrocarbons. In such embodiments, the glyoxal may provide a distinction between oxidation of methane or oxidation of other compounds. Hence, in embodiments, the indicator species may be selected from the group comprising formaldehyde, formic acid, acetic acid, glyoxal, and hypobromite. Moreover, in embodiments, the indicator species may comprise carbon monoxide (CO).

[0043] Alternatively, in specific embodiments, the indicator species may comprise formic acid. Such embodiments may be beneficial as formic acid (HCOOH) may be formed as indirectly related to part of the methane oxidation mechanism via a methyl peroxy radical or formaldehyde (see also further in Figure 3 and the respective section of the detailed description below). The lifetime of HCOOH may depend strongly on the presence of clouds, due to which it may be hard to detect under high humidity conditions. For low humidity the lifetime of HCOOH may be weeks, making it a preferred indicator for enhancing compounds that work over multiple days (such as iron-salt aerosol), because the HCOOH can accumulate and represents an accumulated amount of total methane oxidation. Further, the concentration ofHCOOH may be lower in high NOx conditions. Thus, in embodiments, NOx may be a preferred referral species (see also further below) in combination with HCOOH as indicator species.

[0044] In embodiments (of the method), a single indicator species may be selected, such as formaldehyde. In other embodiments (of the method), two or more indicator species may be selected, such as formaldehyde and BrO.

[0045] The indicator species may especially form (in the tropospheric space) as a response to enhanced methane oxidation, for example due to the emission of an enhancing compound by a target object. As a result, the indicator species may be present in the tropospheric space, especially in the vicinity (i.e. locally) relative to the target object. While emitting the enhancing compound, the target object may be configured to ((in)directly) provide data relating to the (generation of the) indicator species, such as e.g. information concerning type of enhancing compound used, concentrations or amount of enhancing compound emitted, and therefrom derivable information on enhanced methane oxidation. Such data relating to the enhancing compound may thus be made publicly available (as a result of operations performed at the target object) in the tropospheric space. As such, the data relating to the enhancing compound (and derivable therefrom data relating to the indicator species) may be accessible to a given authority of a given country. Especially, in embodiments, the data relating to the enhancing compound (and derivable therefrom data relating to the indicator species) may be accessible to a given authority of a given country if at least one of the following conditions is satisfied: (i) the target object (e.g. a ship) is of the same nationality as these authorities, (ii) the target object (e.g. a ship) is in the territorial waters of these authorities, and (iii) the target object’s destination is a port of the given country and the target object (e.g. a ship) is close to its final destination.

[0046] As can be derived from the above, especially, the indicator species may be a transient molecule, having a limited life time in the atmosphere (and at least shorter than methane).

[0047] The method of the invention may further, in embodiments, comprise (a stage (i)) comparing satellite data from at least part of the tropospheric space for the indicator species with reference data for the indicator species.

[0048] In embodiments, the reference data for the indicator species may comprise model data for the indicator species. In other words, in embodiments, the reference data may comprise data derived from a model for the indicator species. In embodiments, the model data may for example be derived from a model selected from or derived from the group comprising: Goddard Earth Observing System model (GEOS-Chem), Weather Research and Forecastingmodel coupled with Chemistry (WRF-Chem), Community Earth System Model (CESM), Copernicus Atmosphere Monitoring Service (CAMS) Reanalysis, ECHAM / MESSy Atmospheric Chemistry (EMAC) model and Hybrid Single-Particle Lagrangian Integrated Trajectory model (HYSPLIT). Herein, the phrase “ECHAM / MESSy Atmospheric Chemistry (EMAC) model” may especially refer to a combination of ECHAM5 (the 5th generation European Centre - Hamburg general circulation model) and the Modular Earth Submodel System (MESSy). Use of a high resolution model such as WRF-CHEM and HYSPLIT may be advantageous when methane oxidation enhancements are local, while use of a lower resolution global models such as GEOS-CHEM, CAMS Reanalysis and CESM may be advantageous for large scale methane oxidation enhancements. In embodiments, the reference data may comprise the model data for the indicator species. Hence, in embodiments, the method (in stage (i)) may comprise comparing the satellite data for the indicator species with the model data for the indicator species.

[0049] Additionally or alternatively, in embodiments, the reference data may comprise remote monitoring, such as satellite data, for the indicator species from at least another part of the (same) tropospheric space. Yet additionally or alternatively, the reference data may comprise remote monitoring, such as satellite data, for the indicator species from another time period of the (same part of the) same tropospheric space. For example, in embodiments, remote monitoring data for the indicator species (e.g. HCHO) at a first point in time (for example on a day where one or more of methane and the enhancing compound is actively emitted by a target object) may be compared to remote monitoring data for the indicator species at a second point in time (for example on a day where the target object is not actively emitting the one or more of methane and the enhancing compound). In embodiments, the first point in time and the second point in time may for example be separated by a time period of at least 1 day, such as at least 2 days. Moreover, in embodiments, the time period may be at most a month, such as at most 30 days, like at most 21 days. In other embodiments the reference data may be taken during the night, and compared with indicator species measurements during the day, to account for photochemical effects. In embodiments the reference data may be an average, for example a weekly or monthly average of another period of the (same part of the) same tropospheric space. In specific embodiments, the reference data (similarly to the remote monitoring data collected for the indicator species) may especially be collected during the daytime.

[0050] In embodiments, the method in stage (i) may further comprise collecting remote monitoring data, such as satellite data, from at least part of the tropospheric space for a referralspecies. The referral species may especially be different from the enhancing compound. Additionally, in embodiments, the referral species may be different from the indicator species.

[0051] The referral species may, in embodiments, be correlated to a background source of production of the indicator species. For example, the background source of production may be biomass burning. Biomass burning may produce formaldehyde and carbon monoxide. Hence, in embodiments, carbon monoxide may be an indicator for biomass burning, and therewith function as a referral species for formaldehyde (as indicator species) being produced by biomass burning. In specific embodiments, the background source (or origin) of production of the indicator species may be selected from the group comprising: (a) burning, including biomass burning, (b) anthropogenic emissions, including shipping emissions and industrial emissions, (c) atmospheric oxidation, including (i) atmospheric oxidation by OH or Cl and (ii) atmospheric oxidation of non-methane VOCs, and (d) direct emissions.

[0052] Yet alternatively, in embodiments, the referral species may be correlated to a background source of removal of the indicator species. For example, the background source of removal may be photolysis of HCHO induced by sunlight. Using another compound that is similarly affected by such photolysis as a referral species may enable estimation of the loss of HCHO through such photolysis. In specific embodiments, the background source (or origin) of removal of the indicator species may be selected from the group comprising: (a) photolysis, including photolysis by sunlight UV, (b) atmospheric oxidation, including atmospheric oxidation by OH and Cl, (c) dry deposition, (d) wet deposition, (e) uptake by aerosols, and (f) heterogeneous reactions. Herein, heterogeneous reactions may especially refer to reactions on the surface of aerosols, including during dry deposition.

[0053] In specific embodiments, the reference data may comprise the satellite data from at least part of the tropospheric space for the referral species. Herein, in embodiments, the tropospheric space may be defined as the space (or volume) directly over the sea surface and (the space) having a height selected from the range of 1-4 km, such as from the range of 1,5-3 km, such as about 2 km. Therewith, in embodiments, the tropospheric space may especially be defined within a marine boundary layer, i.e., within a part of the atmosphere that has direct contact with (and hence may be directly influence by) the ocean (or sea). The method may thus, in embodiments, comprise (in stage (i)) collecting satellite data for the referral species from at least part of the tropospheric space. As such, in embodiments, the method may comprise comparing the satellite data for the indicator species with the satellite data for the referral species. In specific embodiments, the remote monitoring data collected for the referral species(similarly to the remote monitoring data collected for the indicator species) may especially be collected during the daytime.

[0054] The method of the invention thus may provide the benefit that the origin of the methane removal may be distinguished based on the satellite data for the indicator species being compared to one or more of model data for the indicator species and satellite data for a referral species. With such comparison, the method may provide a check for potential interference, registering the methane removal quantification as valid or invalid (with reference to registration for carbon (footprint) credits). Invalid methane removal may for example be caused by fraudulent behavior by a methane removal implementer, or by coincidental interference due to, for example, a local biomass burning event.

[0055] For example, if the method of quantifying methane removal uses HCHO as an indicator species, an implementer might emit additional HCHO to cause the method according to the present invention to overestimate methane removal. To check for this, a comparison with model data can be used, where the emission of the enhancing compound may be modelled. Such a comparison may reveal that the HCHO was released directly, instead of formed downstream of the release site, upon which quantification may be marked as invalid.

[0056] Especially in the case of iron-salt aerosol emissions as enhancing compound, the HCHO enhancement would appear downstream of the release site. However, when high local HCHO emissions would be detected by the system, methane removal quantification would be registered as invalid. Fraudulent behavior might also include the release of HCHO through biomass burning at the site of the enhancing compound release. This may be accounted for by including CO as referral species in the comparison. Alternatively, in embodiments, carbon monoxide may be used as the indicator species, while formaldehyde may be used as the referral species. Such embodiments may especially be beneficial for extremely highly enhanced atmospheric methane oxidation with chlorine, which may lead to a strong increase of carbon monoxide, while formaldehyde may remain at a specific fixed concentration (because at high Cl concentrations formaldehyde becomes a fixed concentration). By using formaldehyde as a referral species it may be asserted that the carbon monoxide detected may indeed be due to high Cl conditions (as with a relatively high or relatively low concentration of formaldehyde the carbon monoxide may not be due to enhanced methane oxidation). Hence, in some embodiments, the referral species may comprise formaldehyde.

[0057] In another example, in embodiments, using HCHO as the indicator species together with CHOCHO (glyoxal) or acetic acid as the referral species may enable distinguishing between the oxidation of CH4 and the oxidation of non-methane VOCs.The use of a plurality of indicator species may also be used to prevent interfering activities. For example, in a location that is free from clouds, and where the enhancing compound works through Cl oxidation of CFU, the simultaneous use of HCHO and HCOOH as indicator species would detect local emission of HCHO or HCOOH. Hence, in embodiments, the satellite data may comprise satellite data of at least two (different) indicator species. Such embodiments may be advantageous as a plurality of sources or sinks for the indicator species may be taken into account. Similarly, in embodiments, a plurality of referral species may be taken into account. Hence, in embodiments, the satellite data may comprise satellite data of at least two (different) referral species.

[0058] The referral species may, in embodiments, be selected from the group comprising: carbon monoxide, nitrogen dioxide, ozone, acetic acid, glyoxal, formic acid, hydrogen cyanide, water vapor, carbon dioxide, chlorine monoxide, hydrochloric acid, ethane, acetylene, isoprene, dimethyl sulfide and hypobromite. For example, in embodiments, the referral species may comprise hydrogen cyanide, which may be an important indicator for biomass burning. In another example, in embodiments, the referral species may comprise water (H2O (g)), which may be an important indicator for formic acid (HCOOH) deposition. In another example, in embodiments, the referral species may comprise carbon monoxide, which may be an important indicator for industrial emissions or biomass burning. In another example, in embodiments, the referral species may comprise chlorine monoxide or hydrochloric acid, which may be indicators for chlorine chemistry. Further, in embodiments, the referral species may comprise a volatile organic compound, such as one or more of ethane, acetylene, isoprene, and dimethyl sulfide. Especially, in embodiments, the referral species may be selected from the group comprising: carbon monoxide, nitrogen dioxide, ozone, acetic acid, glyoxal, formic acid, and hypobromite. Acetic acid may be formed from the atmospheric oxidation of longer hydrocarbons, and may be detected with satellites. Therefore, use of acetic acid as the indicator species (for generally enhanced atmospheric oxidation) or as referral species (for oxidation of longer hydrocarbons) may be advantageous.

[0059] In specific embodiments, the referral species may comprise at least carbon monoxide. Further, in specific embodiments, the indicator species may comprise formaldehyde and the referral species may comprise at least carbon monoxide.

[0060] In embodiments (of the method), a single referral species may be selected, such as carbon monoxide. In other embodiments (of the method), two or more referral species may be selected, such as carbon monoxide and nitrogen dioxide. Note that in embodiments the oneor more referral species (when applied in the method) may differ from the one or more indicator species (applied in the method).

[0061] In further embodiments, (remote monitoring data, such as) satellite data may be collected in stage (i) using a tropospheric monitoring instrument (such as a TROPOMI satellite). Especially, in embodiments, the method in stage (i) may comprise collecting satellite data during the daytime. The method (in a stage (ii)) may especially comprise quantifying a change in atmospheric methane oxidation over a predetermined time -period. Furthermore, in embodiments, the method (in stage (ii)) may comprise accounting for one or more of: a direction of movement of the (target object, i.e. ,) vessel, a speed of the vessel, wind-velocity at the location of the vessel, and a flow speed of the methane-comprising plume from the outlet. The term “wind-velocity at the location of the vessel” may refer to both the velocity and the direction of the wind.

[0062] Hence, in embodiments, the method may comprise an open-system method. Herein the term “open-system”, such as in open-system method or open-system approach, may refer to a method or approach that (regularly) exchanges feedback with its external environment. In particular, in embodiments, the method may be applied in an open-air environment, i.e., outside (or outdoors). Hence, in embodiments, e.g. due to the abovedescribed accounting for a speed of the vessel, and a wind-velocity at the location of the vessel, the method of the invention may comprise an open-system method.

[0063] Further, in embodiments, the method may comprise quantifying (especially in stage (ii)) (whether a local emission of the enhancing compound may have led to) a local change in atmospheric methane oxidation. Especially, in embodiments, the method may comprise quantifying (whether a local emission of the enhancing compound may have led to) a local increase or decrease in atmospheric methane oxidation. Therefore, in embodiments, the satellite data for the indicator species may comprise a column density of the indicator species. Column density may herein especially be defined as a measure of the amount of intervening matter (herein especially the indicator species and / or the referral species) between an observer and the object being observed (i.e. molecules per area). In embodiments, the column density may comprise one of vertical column density or slanted column density. When schematically displaying the paths of sunlight, reflected by the earth's surface and scattered in the atmosphere, reaching a satellite through the atmosphere, some photons are absorbed by trace gases (such as the indicator and / or referral species) in the atmosphere. The spectrum of the light measured by the satellite provides information on the trace gases along the entire light path of the sunlight as detected by the satellite. In other words, the total density of a given gas, such as the indicatorspecies, may be defined as the concentration of this gas along the entire path, which is also referred to as the slanted column density. This slanted column density may, in embodiments, especially be associated with the point on the earth's surface which the satellite is “looking at”, also known as the foot point.

[0064] The slanted column density does not provide an indication of total concentration right above the foot point. Said total concentration above the foot point may be called the vertical column density. This vertical column density may provide more directly interpretable information on the distribution and concentration of trace gases such as the indicator and / or referral species.

[0065] Hence further, in embodiments, the satellite data for the referral species may comprise a column density of the referral species. Further, in embodiments, the method in stage (ii) may comprise determining a (tracer: tracer) ratio of the column density of the indicator species relative to the column density of the referral species. In embodiments, the (tracer tracer) ratio may thus be calculated by dividing the satellite-derived concentrations of the two species (indicator and referral, respectively). For example, in embodiments, the indicator species may comprise formaldehyde having a concentration [HCHO] and the referral species may comprise carbon monoxide having a concentration [CO], such that the (tracertracer) ratio may be [HCHO]: [CO], Such embodiments may be beneficial as the (tracer Tracer) ratio may be analyzed without a need for complex transport models.

[0066] Additionally or alternatively, in embodiments, the method in stage (ii) may comprise determining an enhancement ratio by comparing the (tracertracer) ratio of the column density of the indicator species relative to the column density of the referral species to a background location outside the tropospheric space. For example, in embodiments, the indicator species may comprise formaldehyde having a first concentration [HCHO]i at the measurement location and a second concentration [HCHO] at the background location providing a relative difference of AHCHO=|[HCHO]i-[HCHO]2, the referral species may comprise carbon monoxide having a first concentration [CO] i at the measurement location and a second concentration [CO] 2 at the background location providing a relative difference of ACO=|[CO]I-[CO]2, and the enhancement ratio maybe AHCHOACO. Use of the enhancement ratio may be advantageous because it may be sensitive to local enhancements. Further, an advantage of using complex transport models may be that several species (e.g. HCHO, O3, NO2 and CO) may be combined in one analysis, therewith improving the accuracy or sensitivity. Furthermore, using complex transport models may provide the benefit that a comparisonbetween model and observations may reveal unexplained atmospheric methane oxidation that can be related to the emission of the enhancing compound.

[0067] Further, in embodiments, the method may comprise evaluating (especially in stage (ii)) the enhanced atmospheric methane oxidation. Herein, the evaluating of the enhanced atmospheric methane oxidation may especially refer to determining the actual amount of methane that is being oxidized, for example expressed as an oxidation rate, based on the comparison of the remote monitoring data. Hence, the evaluation may be based on calculated changes in methane oxidation (rate). Of note, the measurement of an increased concentration of pollutants such as NO2, which emissions are known to be related to methane oxidation, does not necessarily indicate an increase in methane oxidation, since NOXemissions may both result in a local increase as well as a decrease in methane oxidation. Moreover, the rate of methane oxidation is influenced by a plurality of factors, including but not limited to NOx emissions.

[0068] Thus, in embodiments, the method may comprise (a) collecting data relating to a target object using a remote monitoring device, such as a satellite, (b) comparing the collected data to reference data, and (c) evaluating the enhanced atmospheric methane oxidation induced by the target object based on a comparison of the satellite data and the reference data. In other words, in embodiments, the invention may comprise a method for rebroadcasting of data (i) publicly derivable from emissions from the target object into the tropospheric space, (ii) collected by a satellite, and (iii) rebroadcast by the satellite to the ground, such as to a data processing system at land, where the data may be compared and evaluated.

[0069] Further, in embodiments, the method may comprise an intervention stage. In the intervention stage, in embodiments, an intervention may be staged upon the target object to adjust the emission of the enhancing compound. For example, should it be established in the evaluation stage that a desired target amount of enhanced atmospheric methane oxidation was not achieved, in embodiments, in the intervention stage the emission rate of the enhancing compound from the target object may be increased. In other words, the method, in the intervention stage, may comprise emitting higher concentrations of enhancing compound from the target object into the tropospheric space.

[0070] The method may, in embodiments, comprise a cycle of the above mentioned steps. Especially, the method may comprise after executing the intervention stage, re-executing the (collection,) comparison, and evaluation stages. Hence, in embodiments, the method may comprise an evaluation cycle, or “feedback loop”. The term “feedback loop” may herein refer to a method where a system's output (such as e.g. the target object output) may be used as input to modify or reinforce future actions. In other words, the method of the invention may comprisea (continuous) cycle of action, results, analysis, and adjustment. Such embodiments may provide the benefit that efforts providing enhanced methane oxidation through emission of enhancing compounds on a target object may be improved and self-regulated up to an optimum performance point. Hence, in embodiments, the invention may provide a method for evaluating (and controlling) enhanced atmospheric methane oxidation in a tropospheric space above an ocean or a sea and induced by a target object using remote monitoring data, wherein the method comprises a feedback loop comprising: (i) comparing remote monitoring data from at least part of the tropospheric space for an indicator species related to enhanced atmospheric methane oxidation with reference data for the indicator species, wherein the indicator species is not methane; (ii) evaluating the enhanced atmospheric methane oxidation induced by the target object based on a comparison of the remote monitoring data and the reference data; and (iii) intervening at the target object to adjust the enhanced atmospheric methane oxidation induced by the target object.

[0071] Further, in embodiments, the target object may comprise a vessel. For example, in embodiments, the target object may comprise a vessel selected from the group comprising: a ship, a barge, a yacht, an oiler, and a tanker. Alternatively, in embodiments, the target object may comprise a structure. For example, in embodiments, the target object may comprise a structure selected from the group comprising: an (oil) platform, a flare stack, a (factory) chimney, and a wind turbine. Furthermore, in embodiments, the target object may comprise a flying (or airborne) target object (or flying structure) such as selected from the group comprising: an aircraft, a (hot-air) balloon, and a helicopter. In embodiments where the target object comprises a balloon, it may be desirable (in view of protecting the ozone layer) that the balloon is not a stratospheric balloon. Further, in embodiments, the (oil) platform may be an off-shore platform or an on-shore platform, wherein the on-shore platform may be configured to provide (such as exhaust) the enhancing compound in a direction over the sea or ocean. Similarly, in embodiments, the wind turbine may be an off-shore turbine or an on-shore turbine, wherein the on-shore turbine may be configured to provide (such as exhaust) the enhancing compound in a direction over the sea or ocean. Especially, in embodiments, the vessel may comprise a methane-fueled vessel. Hence, in embodiments, the target object may comprise a vessel or structure, wherein the vessel or structure may be selected from the group comprising: a ship, a barge, a yacht, an oiler, an off-shore (oil) platform, and a tanker or an off-shore wind turbine. Especially, the vessel may comprise an outlet (such as a chimney) configured to provide a methane-comprising plume (and / or enhancing compound comprising plume, see alsobelow). The target object may also comprise an arrangement of a plurality of off-shore wind turbines.

[0072] In embodiments, the target object may thus especially be configured to emit the enhancing compound. Hence, in embodiments the target object may emit the enhancing compound (e.g. permanently or intermittently). Further, in embodiments the method may be applied when the target object emits or has emitted the enhancing compound (e.g. within 6 hours after emission of the enhancing compound).

[0073] Hence, in embodiments, the enhanced atmospheric methane oxidation may be due to a local emission of the enhancing compound from the target object. The enhancing compound may especially be mixed with methane. In embodiments, the methane may be exhausted by the vessel, i.e., an exhaust of the vessel (such as an enhancing compoundcomprising plume) may comprise the methane. Hence, in such embodiments, the vessel may be configured to provide (via its outlet and in the enhancing compound-comprising plume) both the methane and the enhancing compound. Additionally or alternatively, in embodiments, the enhancing compound-comprising plume may comprise methane that is ambiently present (at the respective location of the enhancing compound-comprising plume). In other words, in embodiments, the ambiently present methane may be the result of an exhaust of the vessel comprising methane and / or an exhaust of another source of methane.

[0074] Furthermore, in embodiments, the method may further comprise (in a (quantifying) stage (iii)) quantifying an amount of methane removed through the detected enhanced atmospheric methane oxidation. Especially, in embodiments where the satellite data for the indicator species was compared to model data for the indicator species, the difference between model data and satellite observation may be used to quantify the amount of extra methane removal.

[0075] For example, in embodiments, enhanced methane oxidation may be quantified using a satellite retrieval image, e.g. by determining an amount of molecules / cm2 / s. Further, in embodiments, a total amount of methane removed over the area of enhancement due to the enhanced methane oxidation may be quantified by multiplying the enhancement with the surface area (i.e., resulting in a total number of molecules / s). Yet further, in embodiments, the total amount of methane removed over the area of enhancement may be calculated for the total time period of the emission from the target object to provide a total number of methane molecules removed.

[0076] Alternatively, in embodiments, where the satellite data for the indicator species was compared to satellite data for the referral species, the result from the comparison may yieldan amount of extra indicator species in the observation. In an example, a HCHO enhancement of 1.8 1015molecules / cm2may be found based on the first steps of the method. Using the average HCHO photolysis rate in the target region (for example determined using a tropospheric ultraviolet and visible radiation model (TUV) calculator, the enhancement of HCHO may be converted into an estimated extra methane removal (or “oxidation”) rate using an approximated equation:

[0077] Extra methane oxidation rate)

[0078] = [HCHO]enhancement■ (average HCHO photolysis rate) This equation may provide an approximated estimation of extra methane removal, for example using an average HCHO photolysis rate of 6.4 10’5s’1may result in an extra methane oxidation rate of 1.152 1011molecules / cm2 / s. The extra methane oxidation rate may be multiplied by the total area of the observed HCHO enhancement to quantify the total additional methane removal per second. This quantification method may be further improved by including also other factors that influence HCHO lifetime (such as OH and Cl oxidation).

[0079] In embodiments, the method may further be improved by using the observed extra methane oxidation rate, or the satellite data as input in a model. In such embodiments, the model may be used to calculate a total additional methane removal per second, which may be subsequently integrated over a specific time period. In other words, stages (ii) and (iii) of the method may be performed by a model using the data obtained from the satellite in stage (i).

[0080] Further, in another aspect, the invention may provide a use of the method as defined herein for determining the validity of methane removal to detect fraudulent behavior. The method of the invention thus may be used such that the origin of the methane removal may be distinguished based on the satellite data for the indicator species being compared to one or more model data for the indicator species and satellite data for a referral species. With such comparison, the method may be used to check for potential interference, registering the methane removal quantification as valid or invalid (with reference to registration for carbon (footprint) credits). Invalid methane removal may for example be caused by fraudulent behavior by a methane removal implementer, or by coincidental interference due to for example a local biomass burning event.

[0081] In a further aspect, the invention may provide an enhanced atmospheric methane oxidation evaluation system (or “evaluation system”) configured for evaluating enhanced atmospheric methane oxidation in a tropospheric space. Tn embodiments, the tropospheric space may especially be above an ocean or a sea. Further, in embodiments, the evaluation system may especially be configured for evaluating enhanced atmospheric methane oxidationinduced by a target object, for example due to a local emission of an enhancing compound configured to enhance atmospheric methane oxidation. Therefore, in embodiments, the evaluation system may comprise a processing unit. In embodiments, the processing unit may be configured to receive remote monitoring data, such as satellite (observation) data, from at least part of the tropospheric space for an indicator species related to enhanced atmospheric methane oxidation. In specific embodiments, the indicator species may not be methane. Examples of indicator species have been described above in relation to the method and may similarly apply here for the system.

[0082] The processing unit may for example be configured to receive remote monitoring data from a remote monitoring device, such as selected from one or more of a satellite, a drone, and an airplane. Thus, in embodiments, the processing unit may be configured in a data-receiving relationship with the remote monitoring device. In other words, the processing unit may be communicatively connected to a remote monitoring device.

[0083] Hence, in embodiments, the evaluation system may comprise a remote monitoring device configured to collect remote monitoring data from at least part of the tropospheric space for an indicator species related to enhanced atmospheric methane oxidation. In embodiments, the remote monitoring device may be selected from one or more of a satellite, a drone, and an aircraft.

[0084] Further, in embodiments, the processing unit may be configured to evaluate the enhanced atmospheric methane removal in the tropospheric space by using the method as defined herein. Especially, the processing unit may be configured to evaluate the enhanced atmospheric methane removal in the tropospheric space by (a) comparing the collected data relating to the indicator species to reference data for the indicator species, and (b) evaluating the enhanced atmospheric methane oxidation induced by the target object based on a comparison of the remote monitoring (e.g. satellite) data and the reference data. Therefore, the evaluation system may further, for example, comprise a data processing system configured to compare and evaluate the remote monitoring (e.g. satellite) data and the reference data. In embodiments, the data processing system may be configured in a data-receiving relationship with the processing unit. In other words, the data processing system may be communicatively connected to processing unit. Hence, in specific embodiments, the invention may provide an enhanced atmospheric methane oxidation evaluation system configured for evaluating enhanced atmospheric methane oxidation in a tropospheric space above an ocean or a sea induced by a target object, wherein the evaluation system may comprise a processing unit configured to (a) receive satellite data from at least part of the tropospheric space for anindicator species related to enhanced atmospheric methane oxidation, wherein the indicator species may not be methane, and (b) evaluate the enhanced atmospheric methane removal in the tropospheric space by using the method of the invention. The system of the invention may provide the benefit of satellite detection of the indicator species for methane removal over the ocean and the sea, where satellite detection of methane itself is hindered. Therewith, the system of the invention may enable effective, facile, and high-scale quantification of methane removal as a result of atmospheric methane oxidation.

[0085] Further, in embodiments, the enhanced atmospheric methane oxidation evaluation system may be configured to provide daily assessment. The evaluation system may especially, in embodiments, comprise a continuous system, meaning a system that may provide assessment based on variables that change continuously over time (according to a set of differential equations).

[0086] Moreover, in embodiments, the enhanced atmospheric methane oxidation evaluation system may be further configured to monitor the enhanced atmospheric methane oxidation in the tropospheric space over a predetermined time-period. Especially, in embodiments, the evaluation system may be configured to operate during the daytime. Moreover, in embodiments, the evaluation system may be configured to operate over multiple days, such as at least 2 days, like at least 3 days, especially at least 5 days. Furthermore, in embodiments, the evaluation system may be configured to operate over multiple weeks, such as at most 6 weeks, like at most 4 weeks, especially at most 2 weeks.

[0087] In embodiments, the enhanced atmospheric methane oxidation evaluation system may thus comprise a processing unit. In embodiments, the processing unit may be configured to receive satellite (observation) data from at least part of the tropospheric space for the indicator species (that may be different from the enhancing compound). Further, in embodiments, the processing unit may be configured to receive satellite (observation) data from at least part of the tropospheric space for a referral species (that may be different from the enhancing compound, and) that may be correlated to a background source of production of the indicator species. Additionally or alternatively, in embodiments, the processing unit may be configured to receive satellite (observation) data from at least part of the tropospheric space for a referral species (that may be different from the enhancing compound, and) that may be correlated to a background source of removal of the indicator species.

[0088] Further, in embodiments, the enhanced atmospheric methane oxidation evaluation system may be configured to quantify (whether a local emission of the enhancing compound may have led to) a change (especially an increase or decrease) in atmosphericmethane oxidation. Especially, in embodiments, the system may be configured to quantify (whether a local emission of the enhancing compound may have led to) a local increase or decrease in atmospheric methane oxidation. Therefore, in embodiments, the system may be configured to collect satellite data for the indicator species comprising a column density of the indicator species. Similarly, in embodiments, the system may be configured to collect satellite data for the indicator species comprising a column density of the referral species.

[0089] Further, in embodiments, the system may be configured to determine a (tracer: tracer) ratio of the column density of the indicator species relative to the column density of the referral species based on the collected satellite data. In embodiments, the (tracertracer) ratio may especially be calculated by dividing the satellite-derived concentrations of the two species (indicator and referral, respectively). For example, in embodiments, the indicator species may comprise formaldehyde having a concentration [HCHO] and the referral species may comprise carbon monoxide having a concentration [CO], such that the (tracertracer) ratio may be [HCHO]: [CO], Such embodiments may be beneficial as the (tracertracer) ratio may be analyzed using the system without a need for complex transport models.

[0090] Additionally or alternatively, in embodiments, the system may be configured to determine an enhancement ratio by comparing the (tracer tracer) ratio of the column density of the indicator species relative to the column density of the referral species to a background location outside the tropospheric space. For example, in embodiments, the indicator species may comprise formaldehyde having a first concentration [HCHO] i at the measurement location and a second concentration [HCHO]2 at the background location providing a relative difference of HCHO=|[HCHO]I-[HCHO]2, the referral species may comprise carbon monoxide having a first concentration [CO]i at the measurement location and a second concentration [CO]2 at the background location providing a relative difference of ACO=|[CO]I-[CO]2, and the enhancement ratio may be AHCHO:ACO. Use of the enhancement ratio may be advantageous because it may be sensitive to local enhancements. Further, an advantage of using complex transport models may be that several species (e.g. HCHO, Oa, NO2 and CO) may be combined in one analysis, therewith improving the accuracy or sensitivity. Furthermore, using complex transport models may provide the benefit that a comparison between model and observations may reveal unexplained atmospheric methane oxidation that can be related to the emission of the enhancing compound.

[0091] Embodiments of the indicator species and the referral species have been described further above for the method and may similarly apply here for the system. Especially, in embodiments, the indicator species may comprise one of formaldehyde and formic acid.Especially, in embodiments, the referral species may comprise carbon monoxide. More especially, in embodiments, the indicator species may comprise formaldehyde and the referral species may comprise carbon monoxide.

[0092] In another aspect, the invention may provide an arrangement of the target object (as defined herein), an emitter of the enhancing compound (as defined herein), and an emitter control system. In embodiments, the emitter may be comprised by the target object. In other embodiments, the emitter may not be comprised by the target object. In such embodiments, the emitter may be functionally coupled to, such as especially physically associated with, the target object. For example, in embodiments, the target object may comprise a vessel and the emitter may be configured on-board the vessel. In an alternative example, the target object may comprise a wind turbine and the emitter may be configured physically associated to (the top of) the wind turbine, such that the enhancing compound may be emitted at the altitude of the wind turbine.

[0093] The emitter control system may be configured to control emission of the enhancing compound by the emitter. For example, the emitter control system may be configured to initiate or terminate emission of the enhancing compound from the emitter. Additionally or alternatively, in embodiments, the emitter control system may be configured to increase or decrease emission rates of emission of the enhancing compound. Yet additionally or alternatively, the emitter control system may be configured to increase or decrease an amount per time of enhancing compound being emitted by the emitter. The emitter control system may especially be configured to control emission of the enhancing compound by the emitter in dependence of the evaluating of the enhanced atmospheric methane oxidation induced by the target object as defined by the computer-implemented method described above. In embodiments, the emitter may comprise one or more selected from the group comprising: an exhaust, a flare stack, a chimney, and a flow generating device.

[0094] Further, in embodiments, the emitter may comprise an enhancing-compound production device. For example, in embodiments, the emitter may comprise an electrolyser configured to generate the chlorine-comprising compound. In such embodiments, the enhancing-compound production device may be configured functionally coupled, such as e.g. fluidically connected, to the emitter, such that the enhancing compound produced by the enhancing-compound production device may be emitted by the emitter, e.g. by a flare stack or chimney. Additionally or alternatively, the emitter may be functionally coupled, such as fluidically coupled, to a storage container comprising the chlorine-comprising compound.In another aspect, the invention may provide a method for functionally coupling an emitter of the enhancing compound (as defined herein), to a target object (as defined herein). The method may especially comprise functionally coupling an emitter and an emitter control system (see above) to the target object. Functionally coupling the emitter to the target object may for example refer to positioning the emitter on board the target object or in another manner (such as through mechanical securing thereof) physically associating the emitter to the target object to facilitate emission of the enhancing compound into the tropospheric space at or near the target object. Hence, in such embodiments, the target object (e.g. a (methane-fueled) vessel) and the emitter may be physically interconnected. Further, functionally coupling the emitter control system to the target object may for example refer to providing an electrical and / or wireless communication connection between the emitter control system to the emitter and the target object to facilitate control over e.g. the injection rate of the enhancing compound into the tropospheric space.

[0095] In a further aspect, the invention provides a method for evaluating enhanced atmospheric methane oxidation in a tropospheric space above an ocean or a sea and induced by a target object using remote monitoring data. The method may comprise locally emitting an enhancing compound into the tropospheric space. Especially, the enhancing compound may be locally emitted from the target object. Such local emission into the tropospheric space may, in embodiments, be above the ocean or the sea. In embodiments, the enhancing compound may cause conversion, such as especially oxidation, of methane into an indicator species. The indicator species may especially be detectable in a spectral band suitable for ocean observation. Moreover, the indicator species may be detectable in a spectral band different than an infrared band used for direct detection of (atmospheric) methane. Especially, the indicator species may be detectable in one or more spectral (e.g. absorption) bands, such as one or more spectral bands in the UV and / or visible wavelength range. The indicator species may especially be detectable in one or more spectral bands different from one or more infrared (e.g. absorption) bands used for detection of atmospheric methane.

[0096] In embodiments, the indicator species may not be methane. Especially, in embodiments, the enhancing compound, methane, and the indicator species may be mutually different species.

[0097] Furthermore, in embodiments, the emission of the enhancing compound may lead to oxidation of atmospheric methane into the indicator species. Additionally or alternatively, the emission of the enhancing compound may cause oxidation of atmospheric methane into the indicator species, i.e. methane available in the tropospheric space above theocean or the sea. The methane may, in embodiments, be made available in the tropospheric space above the ocean or the sea by the target object. Hence, additionally or alternatively, in embodiments, the enhancing compound may cause oxidation of methane, emitted from the target object into the tropospheric space above the ocean or the sea, into the indicator species.

[0098] The method may further comprise acquiring remote monitoring data representing a change in the indicator species concentration in the tropospheric space above the ocean or the sea. Such a change in the indicator species may especially be due to the emission of the enhancing compound from the target object. For example, in embodiments, the remote monitoring data may be acquired by detecting a change in intensity of one or more spectral bands. Hence, the method may comprise acquiring remote monitoring data representing a change in the indicator species in the tropospheric space above the ocean or the sea induced by locally emitting the enhancing compound from the target object.

[0099] Further, the method may comprise quantifying a local change in atmospheric methane oxidation due to the local emission of the enhancing compound from the target object. Such quantifying may, in embodiments, especially be based on the change in the indicator species represented by the remote monitoring data. For example, in embodiments, the local change in atmospheric methane oxidation due to the local emission of the enhancing compound from the target object may be quantified based on a change in intensity of the one or more spectral bands suitable for ocean observation of the indicator species. In embodiments, the quantifying of the local change in atmospheric methane oxidation may additionally involve the use of reference data and referral species data.

[0100] Hence, in embodiments, the invention provides a method for evaluating enhanced atmospheric methane oxidation in a tropospheric space above an ocean or a sea and induced by a target object using remote monitoring data, wherein the method comprises: (i) locally emitting an enhancing compound into the tropospheric space above the ocean or the sea from the target object, the enhancing compound causing oxidation of atmospheric methane into an indicator species detectable in a spectral band suitable for ocean observation and different than an infrared band used for direct detection of atmospheric methane, wherein the indicator species is not methane; (ii) acquiring remote monitoring data representing a change in the indicator species in the tropospheric space above the ocean or the sea induced by locally emitting the enhancing compound from the target object; and (iii) quantifying a local change in atmospheric methane oxidation due to the local emission of the enhancing compound from the target object based on the change in the indicator species represented by the remote monitoring data.In a further aspect, the invention provides a method for evaluating enhanced atmospheric methane oxidation in a tropospheric space above an ocean or a sea and induced by a target object using satellite remote monitoring data, wherein the method comprises: (i) enhancing atmospheric methane oxidation by locally emitting an enhancing compound into the tropospheric space from the target object, causing a change in an indicator species related to enhanced atmospheric methane oxidation, wherein the indicator species is not methane; and (ii) quantifying enhanced atmospheric methane oxidation induced by the target object using remote monitoring data from at least part of the tropospheric space for the indicator species and using reference data for the indicator species, wherein the remote monitoring data for the indicator species is derived from spectrometer measurements acquired in a spectral band suitable for ocean observation and different from an infrared band required for direct methane detection.

[0101] In a further aspect, the invention provides a method for evaluating enhanced atmospheric methane oxidation in a tropospheric space above an ocean or a sea and induced by a target object, wherein the target object locally emits an enhancing compound into the tropospheric space above the ocean or the sea from the target object, the enhancing compound causing conversion of methane, available in the tropospheric space above the ocean or the sea or emitted from the target object into the tropospheric space above the ocean or the sea, into the an indicator species; wherein the enhancing compound, methane, and the indicator species are mutually different species; the method comprising: (i) acquiring remote monitoring data representing a change in the indicator species availability in the tropospheric space above the ocean or the sea induced by the local emission of the enhancing compound from the target object by detecting a change in intensity of one or more spectral bands suitable for ocean observation of the indicator species and different from one or more infrared spectral bands used for direct a detection of atmospheric methane; and (ii) quantifying a local change in atmospheric methane oxidation due to the local emission of the enhancing compound from the target object based on the change in indicator species represented by the remote monitoring data.

[0102] Further, in another aspect, the invention may provide a use of the computer program product as defined herein for determining the validity of methane removal to detect fraudulent behavior. The system of the invention thus may be used such that the origin of the methane removal may be distinguished based on the acquired satellite data for the indicator species and its being compared to one or more of model data for the indicator species and satellite data for a referral species. With such comparison, the system may be used to check forpotential interference, registering the methane removal quantification as valid or invalid. Invalid methane removal may for example be caused by fraudulent behavior by a methane removal implementer, or by coincidental interference due to for example a local biomass burning event.

[0103] In yet another aspect, the invention may provide a computer program product comprising instructions for execution on a control system. The control system may especially be configured functionally coupled to the enhanced atmospheric methane oxidation evaluation system as defined herein, or may comprised thereby. As such, in embodiments, the instructions (comprised by the computer program product), when executed by the control system, may cause the evaluation system to cany out the method as defined herein. Hence, in specific embodiments, the invention may provide a computer program product comprising instructions for execution on a control system functionally coupled to the enhanced atmospheric methane oxidation evaluation system as defined herein, or comprised thereby, wherein the instructions, when executed by the control system, may cause the evaluation system carry out the method of the invention. Further, in another aspect, the invention may provide a use of the computer program product as defined herein for determining the validity of methane removal to detect fraudulent behavior. The computer program product of the invention thus may be used such that the origin of the methane removal may be distinguished based on the satellite data for the indicator species being compared to one or more of model data for the indicator species and satellite data for a referral species.

[0104] In a further aspect, the invention may provide a data carrier, carrying thereupon program instructions which, when executed by a data processing system, cause the data processing system to carry out the computer-implemented method according to the invention. Herein, the term “data”, such as in “satellite data”, even when used in singular, may refer to a plurality of data.

[0105] The embodiments described herein are not limited to a single aspect of the invention. In particular, any embodiment describing the method may further relate to the computer program product and to the data carrier, i.e., the (program) instructions of the computer program product and the data carrier may correspond to any embodiment of the method described herein.

[0106] BRIEF DESCRIPTION OF THE DRAWINGS

[0107] Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings in which corresponding referencesymbols indicate corresponding parts, and in which: Figs. 1-4 schematically depict embodiments of the invention. The schematic drawings are not necessarily to scale.

[0108] DETAILED DESCRIPTION OF THE EMBODIMENTS

[0109] Fig. 1 schematically depicts the method of the invention. In specific embodiments, the invention provides a method for evaluating enhanced atmospheric methane oxidation in a tropospheric space 500 above an ocean or a sea and induced by a target object 400 using satellite data.

[0110] As depicted in Fig. 1, a target object 400 may be configured to provide an enhancing compound-comprising plume 45. In embodiments, the target object 400 may (thus) be configured to emit an enhancing compound 3. For example, the enhancing compound 3 may be emitted in the plume 45 provided from, such as especially by, the target object 400. Especially, in embodiments, the target object 400 may comprise a vessel 410 or structure 420. In specific embodiments, the vessel 410 or structure 420 may be selected from the group comprising: a ship (as depicted here), a barge, a yacht, an oiler, an off-shore (oil) platform, and a tanker or an off-shore wind turbine 425. Yet in embodiments, the vessel 410 or structure 420 may comprise an on-shore (oil) platform or an on-shore wind turbine 425, where the enhancing compound 3 may be provided (such as exhausted) in a direction over the sea or ocean. In embodiments, the vessel 410 may comprise an outlet (such as a chimney) 40 configured to provide the enhancing compound-comprising plume 45 (optionally comprising the enhancing compound 3).

[0111] In specific embodiments, the vessel 410 may comprise a methane-fueled vessel (e.g. a vessel using LNG as fuel). Especially, in such embodiments, the vessel 410 may be configured to emit the enhancing compound-comprising plume 45 together with methane 5.

[0112] Furthermore, in embodiments (not depicted), the target object 400 may comprise a flying (or airborne) target object (or flying structure) such as selected from the group comprising: an aircraft, a (hot-air) balloon, and a helicopter.

[0113] The method may comprise three stages, as indicated in Fig. 1 by (i), (ii), and (iii). In embodiments, the method may comprise in stage (i) collecting satellite data from at least part of the tropospheric space 500 for an indicator species 1 related to enhanced atmospheric methane oxidation. Further, in embodiments, the method in stage (i) may comprise collecting satellite data during the daytime. The indicator species 1 may especially not be methane. Moreover, in embodiments, the indicator species 1 may be different from an enhancing compound 3, see also further below.In embodiments, the satellite data may be collected in stage (i) using a system ( 100) such as a satellite configured downstream of the enhancing compound-comprising plume 45. The terms “upstream” and “downstream” relate to an arrangement of items or features relative to the propagation of the enhancing compound-comprising plume 45 from a plume generating means (here especially the target object 400), wherein relative to a first position within the methane-comprising plume 45, a second position the enhancing compoundcomprising plume 45 closer to the plume generating means is “upstream”, and a third position within the enhancing compound-comprising plume 45 further away from the plume generating means is “downstream”. Especially, in embodiments, the system (100) such as a satellite may be configured to observe the enhancing compound-comprising plume 45. In general a satellite may (i) make pass, or make an ‘overpass’, over the location of interest, or (ii) be a stationary satellite that observes the area continuously. In embodiments, the system (100), such as the satellite, may pass over the respective area of measurement (i.e. the tropospheric space) 1 or 2 times per day.

[0114] In embodiments, the satellite data may especially be collected in stage (i) using a tropospheric monitoring instrument (such as the TROPOMI satellite). Further, in embodiments, the method may comprise in stage (i) comparing satellite data from at least part of the tropospheric space 500 for the indicator species 1 with reference data for the indicator species 1.

[0115] In embodiments, the reference data may comprise model data for the indicator species 1. In embodiments, the model data may be derived from a model selected from or derived from the group comprising: Goddard Earth Observing System model (GEOS-Chem), Weather Research and Forecasting model coupled with Chemistry (WRF-Chem), Community Earth System Model (CESM), Copernicus Atmosphere Monitoring Service (CAMS) Reanalysis, ECHAM / MESSy Atmospheric Chemistry (EMAC) model and Hybrid SingleParticle Lagrangian Integrated Trajectory model (HYSPLIT). Additionally or alternatively, in embodiments, the reference data may comprise satellite data for the indicator species 1 from at least another part of the (same) tropospheric space 500. Yet additionally or alternatively, in embodiments, the reference data may comprise satellite data for the indicator species 1 from another time period of the same tropospheric space 500.

[0116] Further, in embodiments, the method may comprise in stage (i) collecting satellite data from at least part of the tropospheric space 500 for a referral species 2 that may be correlated to (a) a background source of production of the indicator species 1 or (b) a background source of removal of the indicator species 1. In embodiments, the backgroundsource (or origin) of production of the indicator species 1 may be selected from the group comprising: (a) burning, including biomass burning, (b) anthropogenic emissions, including shipping emissions and industrial emissions, (c) atmospheric oxidation, including (i) atmospheric oxidation by OH or Cl and (ii) atmospheric oxidation of non-methane VOCs, and (d) direct emissions. Furthermore, in embodiments, the background source (or origin) of removal of the indicator species 1 may be selected from the group comprising: (a) photolysis, including photolysis by sunlight UV, (b) atmospheric oxidation, including atmospheric oxidation by OH and Cl, (c) dry deposition, (d) wet deposition, (e) uptake by aerosols, and (f) heterogeneous reactions.

[0117] In embodiments, the referral species 2 may especially be different from the indicator species 1. Further, in embodiments, the referral species 2 may also be different from the enhancing compound 3, see also further below. Hence, in embodiments, the reference data may comprise the satellite data from at least part of the tropospheric space 500 for the referral species 2. Further, in embodiments, the satellite data may comprise satellite data of at least two (different) referral species 2.

[0118] Further, in embodiments, the method may comprise in stage (ii) evaluating the enhanced atmospheric methane oxidation induced by the target object 400 based on a comparison of the satellite data and the reference data. Especially, the method in stage (ii) may comprise quantifying (whether a local emission of the enhancing compound 3 may have led to) a local change (especially an increase or decrease) in atmospheric methane oxidation. Moreover, in embodiments, the method in stage (ii) may comprise quantifying a change in atmospheric methane oxidation over a predetermined time -period. Moreover, in embodiments, the method in stage (ii) may comprise accounting for one or more of: a direction of movement of the (target object 400, i.e.,) vessel 410, a speed of the vessel 410, wind-velocity at the location of the vessel 410, and a flow speed of the enhancing compound-comprising plume 45 from the outlet 40.

[0119] In embodiments, the satellite data for the indicator species 1 may comprise a column density of the indicator species 1. Furthermore, in embodiments, the satellite data for the referral species 2 may comprise a column density of the referral species 2. As such, in embodiments, the method in stage (ii) may comprise determining a (tracer: tracer) ratio of the column density of the indicator species 1 relative to the column density of the referral species 2. In further embodiments, the method in stage (ii) may comprise determining an enhancement ratio by comparing the (tracertracer) ratio of the column density of the indicator species 1relative to the column density of the referral species 2 to a background location outside the tropospheric space 500.

[0120] In further embodiments, the method may comprise in stage (iii) quantifying an amount of methane removed through the detected enhanced atmospheric methane oxidation.

[0121] Fig. 2 schematically depicts some further embodiments of the invention, especially highlighting the outlet 40 of the target object 400, especially the vessel 410. Especially, in embodiments, the invention may provide a method for evaluating enhanced atmospheric methane oxidation in the tropospheric space 500 induced by the target object 400 due to a local emission of an enhancing compound 3 configured to enhance atmospheric methane oxidation. Especially, as depicted in the figure, the enhancing compound 3 may be provided to the outlet 40 of the vessel 410. Therefore, in embodiments, the vessel 410 may comprise an enhancing compound source 30 configured to host the enhancing compound 3. Further, in embodiments, the vessel 410 may comprise an inlet 31 configured to fluidically connect the enhancing compound source 30 to the outlet 40. Especially, in embodiments, the inlet 31 may be configured to provide the enhancing compound 3 to the outlet 40 (to be mixed with methane 5). Hence, in embodiments, the enhanced atmospheric methane oxidation may be due to a local emission of an enhancing compound 3 that enhances atmospheric methane oxidation. The enhancing compound 3 may especially be mixed with methane 5. In embodiments, the methane 5 may be exhausted by the vessel 410, i.e., an exhaust of the vessel 410, such as the enhancing compound-comprising plume 45 may comprise the methane 5. Hence, in such embodiments, the vessel 410 may be configured to provide (via its outlet 40 and in the enhancing compound-comprising plume 45) both the methane 5 and the enhancing compound 3. Additionally or alternatively, in embodiments, the enhancing compoundcomprising plume 45 may comprise methane 5 that is ambiently present (at the respective location of the enhancing compound-comprising plume 45). In other words, in embodiments, the ambiently present methane 5 may be the result of an exhaust of the vessel 410 comprising methane 5 and / or an exhaust of another source of methane 5.

[0122] In embodiments, the enhancing compound 3 may especially enhance atmospheric methane oxidation by locally increasing the concentration of Cl atoms. Therefore, in embodiments, the enhancing compound 3 may comprise one or more of: a chloride salt, an iron-comprising compound, an iron-chloride comprising compound, and a chlorine-comprising compound. Especially, in embodiments, the enhancing compound 3 may comprise one or more of an iron salt aerosol, Ch, and sodium hypochlorite.In specific embodiments, the invention may (thus also) provide an enhanced atmospheric methane oxidation evaluation system 100 configured for evaluating enhanced atmospheric methane oxidation in a tropospheric space 500 above an ocean or a sea induced by a target object 400 (due to a local emission of an enhancing compound 3 configured to enhance atmospheric methane oxidation). In embodiments, the evaluation system 100 may especially comprise a processing unit 10 configured to receive satellite (observation) data from at least part of the tropospheric space 500 for an indicator species 1 related to enhanced atmospheric methane oxidation. Further, in embodiments, the processing unit 10 may be further configured to receive satellite (observation) data from at least part of the tropospheric space 500 for a referral species 2 (that is different from the enhancing compound 3, and) that may be correlated to (a) a background source of production of the indicator species 1 or (b) a background source of removal of the indicator species 1.

[0123] In embodiments, the enhanced atmospheric methane oxidation evaluation system 100 may be configured to provide daily assessment.

[0124] Furthermore, in embodiments, the enhanced atmospheric methane oxidation evaluation system 100 may be further configured to monitor the enhanced atmospheric methane oxidation in the tropospheric space 500 over a predetermined time-period.

[0125] Further, in embodiments, the enhanced atmospheric methane oxidation evaluation system 100 may be configured to quantify (whether a local emission of the enhancing compound 3 may have led to) a change (especially an increase or decrease) in atmospheric methane oxidation.

[0126] In specific embodiments, the invention further may provide a computer program product comprising instructions for execution on a control system 300 functionally coupled to the enhanced atmospheric methane oxidation evaluation system 100 as described herein, or comprised thereby. Especially, the instructions, when executed by the control system 300, may cause the evaluation system 100 to carry out the method.

[0127] The invention is based on the insight that locally enhanced atmospheric methane (CH4) oxidation can be revealed through combining satellite observations of gas-phase species that are involved in the CH4 oxidation mechanism, in particular formaldehyde (HCHO) or formic acid (CHOOH).

[0128] Figure 3 schematically depicts the atmospheric CEU oxidation mechanism. In short, CEU oxidation in the general troposphere may be mainly driven by reactions with hydroxyl (OH) radicals, and a few percent of CH4 may be oxidized by reaction with chlorine atoms (Cl). OH may be produced by ozone (O3) photolysis, and O3 may be produced from NO2photolysis. HCHO is an intermediate semi-stable species that oxidizes to CO within a few hours. CO is a much more stable intermediate species with lifetime of about 30 days that eventually oxidizes into CO2.

[0129] Therefore, in embodiments, the indicator species 1 may be selected from a species directly involved in a methane oxidation mechanism. Especially, as depicted in Fig. 3, the methane oxidation mechanism may comprise oxidation of methane via one or more of CH3, CH3O2, H2CO and HCO to carbon monoxide and / or carbon dioxide.

[0130] Especially, the indicator species 1 may be selected from the group comprising: formaldehyde, formic acid, acetic acid, glyoxal, carbon monoxide, and hypobromite. In specific embodiments, the indicator species 1 may comprise one of formaldehyde and formic acid.

[0131] Moreover, in embodiments, the referral species 2 may be selected from the group comprising: carbon monoxide, nitrogen dioxide, ozone, acetic acid, glyoxal, formic acid, hydrogen cyanide, water vapor, carbon dioxide, chlorine monoxide, hydrochloric acid, ethane, acetylene, isoprene, dimethyl sulfide and hypobromite. Especially, in embodiments, the referral species 2 may comprise at least carbon monoxide.

[0132] In specific embodiments, the indicator species 1 may comprise formaldehyde and the referral species may comprise carbon monoxide.

[0133] Figs. 4 schematically depicts some definitions as used with respect to the invention. As described above, in embodiments, the enhancing compound 3 may especially be emitted in the tropospheric space 500. In embodiments, the tropospheric space 500 may especially be defined above an ocean or a sea 70. Moreover, in embodiments, the tropospheric space 500 may herein be defined as a space (or volume) directly over the sea surface 75 and (the space) having a height hi (relative to the sea surface 75) selected from the range of 1-4 km.

[0134] Moreover, in (other) embodiments, the enhancing compound 3 may be emitted in a maritime region. Especially, in such embodiments, the enhancing compound 3 may be emitted in a space above a virtual plane Vp at land, wherein the virtual plane Vp is at sea-level. In such embodiments, the virtual plane Vp may be defined at land at 0 m height but within a shortest distance di of 3 km from an ocean or a sea 70. Hence, in embodiments, the enhancing compound 3 may be emitted in a space above land but near the sea 70, i.e. in a coastal region. Hence, the term “maritime region” may refer to ocean or sea 70 , and also to land within 3 km from an ocean or sea 70. The height hi of the tropospheric space 500 over land (in a maritime region) is especially defined relative to sea level. Especially, in embodiments, the maritime region may refer to a region at maximum 3 km from the nearest sea surface 75.Fig. 4 A schematically depicts an embodiment of an arrangement 2000 of a target object 400, such as a vessel 410, an emitter 200 of the enhancing compound 3, and a control system 300, such as especially an emitter control system 1300. Here, in embodiments, the emitter 200 may be comprised by or functionally coupled (such as physically associated) to the target object 400. For example, the emitter 200 may be coupled to an exhaust device 250 (like a chimney 40) of the vessel 410. In embodiments, the exhaust device 250 (especially chimney 40) of the vessel 410 may be configured as emitter 200. The exhaust device 250 may especially be configured to provide an exhaust stream 90, which may function as a gaseous flow 50 comprising the enhancing compound 3. Reference 5 may herein refer to a pollutant 5, such as e.g. methane.

[0135] Fig. 4B schematically depicts an embodiment of the arrangement 2000 configured of a target object 400, such as a structure 420, e.g. a wind turbine 425. Here, in embodiments, the emitter 200 may be comprised by or functionally coupled (such as physically associated to the target object 400. For example, the emitter 200 may be incorporated into the structure 420, such as e.g. into the hub (i.e. the part of the wind turbine 425 where the blades are connected) of a wind turbine 425. The blades of the wind turbine 425 may especially be configured to provide a flow of gas into a different direction relative to (natural) wind captured by the wind turbine 425, which flow may function as the gaseous flow 50 for the emission of the enhancing compound 3.

[0136] Fig. 4C schematically depicts an embodiment of the arrangement 2000 comprising an off-shore structure 420, e.g. as depicted here a wind turbine 425, and a chimney 40 configured to function as the emitter 200. Here, in embodiments, the wind turbine 425 may be configured to provide electricity to the chimney 40.

[0137] Here below, some further embodiments and aspects are described. Formaldehyde as indicator species (1):

[0138] It appears possible that formaldehyde (HCHO) column enhancements may be detectable along shipping lanes using TROPOMI observations. Therefore, the method of the invention may especially provide advantage when applied to situations where the enhancing compound 3 may not be sufficiently detected directly, in which case there may be a need for an indicator species 1 that is different from the enhancing compound 3 (in this example, HCHO). Hence, in embodiments, the indicator species 1 may comprise formaldehyde.

[0139] The atmospheric concentration of HCHO may depend on its production sources and removal sinks. In figure 3 it can be seen that every CH4 that may be oxidized, either by Cl or OH, will go through a cycle that leads to the formation of HCHO (H2CO). In a steady statethis means that the combined source of HCHO via CH3O and CH3OOH may be approximately equal to the total CH4 oxidation. Assuming negligible direct HCHO sources over the remote marine boundary layer, the main sources for HCHO may be the oxidation of CH4 (i.e., CH4 + HCHO with reaction rate coefficient kcH4+OH and CH4 + Cl

[0140]

[0141] HCHO with reaction rate coefficient kcH4+ci) and the main loss may be photolysis and HCHO oxidation by OH and Cl

[0142]

[0143] H2O + HCO with reaction rate coefficient kncno+OH, HCHO + Cl

[0144]

[0145] HC1 + CO + HO2 with reaction rate coefficient kncHO+ci, HCHO + hv

[0146]

[0147] H + HCO with photolysis rate J2, and HCHO + hv

[0148]

[0149] H2 + CO with photolysis rate J3). Herein “hv” may refer to a photon, such as coming from sunlight.

[0150] Using a steady-state approximation, the concentration of [HCHO] becomes:

[0151] <<

[0152]

[0153] wherein J2 and J3 represent photolysis rates for the two photolysis rations listed above, kcH4+on[OH][CH4] represents the reaction rate of methane oxidation by OH, kcH4+ci[Cl][CH4] represents the reaction rate of methane oxidation by Cl, kHCHO+ou[OH] represents the first order reaction rate of HCHO oxidation by OH, and kncHo+ci[Cl] represents the first order reaction rate of HCHO oxidation by Cl.

[0154] Using an average [OH] of 106molecules / cm3and kncno+OH = 8.5xl0’12cm3 / molecule / s leads to kHCHO+OH[OH] = 8.6xl0’6s’1, and using [Cl] of 104atoms / cm3, combined with kncno+ci = 7.32xl0’ncm3 / molecule / s results in kncHO+ci [Cl] = 7.32xl0’7s’1, while photolysis may be much faster: J2 = 4xl0’6s’1and J3=6xl0’5s’1. Thus, under typical conditions in the remote marine boundary layer, [OH] may only determine 8% of the loss rate for HCHO and the impact of [Cl] may be negligible, while OH and Cl may determine close to 100% of the production rate through CH4 oxidation. Thus, when methane oxidation goes up by increased [OH] or [Cl], the production may go up, while the loss rate may not increase as much, leading to an increase of HCHO. In these typical conditions, the concentration of HCHO may be approximated as (showing a linear relation between methane oxidation rate and HCHO concentration):

[0155]

[0156] However, if the concentration of Cl becomes very high, above 106atoms / cm3, the reaction between HCHO and Cl may become the main loss for HCHO and the reaction between CH4 and Cl may become the main source, resulting in the following approximation:

[0157] 1900 ppb = 2.7 ppb

[0158]

[0159] This means that under very high Cl conditions, the concentration of HCHO will either increase or decrease (if there are local sources) towards a fixed value of around 3 ppb (in case of only CH4 oxidation). If there are local non-methane VOCs, then those would change the magnitude of this fixed HCHO concentration.

[0160] OH cannot be increased as much as Cl, but under very high OH conditions, for example 107- 108molecules / cm3, the loss of HCHO to OH can become the main sink, in which case the concentration of HCHO will also approach a fixed value, in this case around 1.4 ppb:

[0161]

[0162] Thus, in conclusion HCHO may be used as indicator species for atmospheric methane oxidation, and may be approximated to be linearly depending on total methane oxidation rate, except under very high Cl or OH concentrations (in which case it is no longer linear, but moves towards a fixed HCHO concentration). Because the ratio ofkcH4+clbeingkHCHO+Cl relatively large compared to the ratio ofkcH4+0Hthe strength of the HCHO signal may bekHCHO+OH

[0163] relatively strong for methane oxidation enhancement with Cl. Therefore, in specific embodiments, enhancing compound 3 may enhance atmospheric methane oxidation by increasing the concentration of Cl atoms.

[0164] Formic acid as indicator species (1):

[0165] In embodiments, the indicator species 1 may comprise formic acid. Formic acid (HCOOH) may be formed as part of the methane oxidation mechanism via formaldehyde. Additionally or alternatively, formic acid may be formed via the reaction of water with a Criegee intermediate that forms by the reaction of CH3O2 + Cl. In prior art this formic acid formation reaction has been used as a proxy for the reaction of CH3O2 + OH and found that the source via the Criegee intermediate becomes the main source of HCOOH for OH levels of 106molecules / cm3, increasing the concentration of HCOOH by 1 OOx from 0.16 ppt to 10 ppt. Thus, for a concentration of Cl in the range of 106atoms / cm3, similar impact on HCOOH may be expected. The production of HCOOH from this mechanism will depend on the concentration of Cl for the reaction of CH3O2 + Cl

[0166]

[0167] CH2O2 + HC1, which competes with reactions of CH3O2 with HO2, NO and CIO. At the same time a concentration of CH3O2 may also depend on the Cl concentration from the reaction of CH4 + Cl. Therefore, the source of HCOOH may depend squarely on the concentration of Cl. In embodiments, the source of HCOOH may be approximated as:

[0168]

[0169] wherein SHCOOH represents the source rate of HCOOH, Omrepresents the total methane oxidation rate, kcH3O2+ci[Cl] represents the rate of the reaction CH3O2 + Cl, kcH3O2+No[NO] represents the rate of the reaction CH3O2 + NO, kcH3O2+HO2[HO2] represents the rate of the reaction CH3O2 + HO2, and kcn3O2+cio[ClO] represents the rate of the reaction CH3O2 + Cl.

[0170] The term “plurality” refers to two or more. Furthermore, the terms “a plurality of’ and “a number of’ may be used interchangeably. The terms “substantially” or “essentially” herein, and similar terms, will be understood by the person skilled in the art. The terms “substantially” or “essentially” may also include embodiments with “entirely”, “completely”, “all”, etc. Hence, in embodiments the adjective substantially or essentially may also be removed. Where applicable, the term “substantially” or the term “essentially” may also relate to 90% or higher, such as 95% or higher, especially 99% or higher, even more especially 99.5% or higher, including 100%. Moreover, the terms ’’about” and “approximately” may also relate to 90% or higher, such as 95% or higher, especially 99% or higher, even more especially 99.5% or higher, including 100%. For numerical values it is to be understood that the terms “substantially”, “essentially”, “about”, and “approximately” may also relate to the range of 90% - 110%, such as 95%-105%, especially 99%-101% of the values(s) it refers to. The term “comprise” also includes embodiments wherein the term “comprises” means “consists of’. The term “and / or” especially relates to one or more of the items mentioned before and after “and / or”. For instance, a phrase “item 1 and / or item 2” and similar phrases may relate to one or more of item 1 and item 2. The term "comprising" may in an embodiment refer to "consisting of' but may in another embodiment also refer to "containing at least the defined species and optionally one or more other species". Use of the verb "to comprise" and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. Unless the context clearly requires otherwise, throughout the description and the claims, the words “comprise”, “comprising”, “include”, “including”, “contain”, “containing” and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of “including, but not limited to”. The article "a" or "an" preceding an element does not exclude the presence of a plurality of such elements.

[0171] Furthermore, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. It is to be understood that the terms so used areinterchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein.

[0172] The term “further embodiment” and similar terms may refer to an embodiment comprising the features of the previously discussed embodiment, but may also refer to an alternative embodiment. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim.

[0173] It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims.

[0174] The devices, apparatus, or systems may herein amongst others be described during operation. As will be clear to the person skilled in the art, the invention is not limited to methods of operation, or devices, apparatus, or systems in operation. The invention may be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In a device claim, or an apparatus claim, or a system claim, enumerating several means, several of these means may be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. The invention also provides a control system that may control the device, apparatus, or system, or that may execute the herein described method or process. Yet further, the invention also provides a computer program product, when running on a computer which is functionally coupled to or comprised by the device, apparatus, or system, controls one or more controllable elements of such device, apparatus, or system.

[0175] The invention further applies to a device, apparatus, or system comprising one or more of the characterizing features described in the description and / or shown in the attached drawings. The invention further pertains to a method or process comprising one or more of the characterizing features described in the description and / or shown in the attached drawings. Moreover, if a method or an embodiment of the method is described being executed in a device, apparatus, or system, it will be understood that the device, apparatus, or system is suitable for or configured for (executing) the method or the embodiment of the method, respectively.

[0176] The various aspects discussed in this patent can be combined in order to provide additional advantages. Further, the person skilled in the art will understand that embodiments can be combined, and that also more than two embodiments can be combined. Furthermore, some of the features can form the basis for one or more divisional applications.

Claims

CLAIMS:

1. A computer-implemented method for evaluating enhanced atmospheric methane oxidation in a tropospheric space (500) above an ocean or a sea and induced by a target object (400) using remote monitoring data, wherein the method comprises:(i) comparing remote monitoring data from at least part of the tropospheric space (500) for an indicator species (1) related to enhanced atmospheric methane oxidation with reference data for the indicator species (1), wherein the indicator species (1) is not methane; and(ii) evaluating the enhanced atmospheric methane oxidation induced by the target object based on a comparison of the remote monitoring data and the reference data.

2. The computer-implemented method according to claim 1, wherein the remote monitoring data comprises data collected using one or more of a satellite, an aircraft, and a drone, wherein one of the following applies:the reference data comprises model data for the indicator species (1); or the remote monitoring data comprises satellite data; and the reference data comprises satellite data for the indicator species (1) from (i) at least another part of the tropospheric space (500) or (ii) another time period of the same tropospheric space (500).

3. The computer- implemented method according to any one of the preceding claims, wherein the method in stage (i) further comprises collecting remote monitoring data from at least part of the tropospheric space (500) for a referral species (2) that is correlated to (a) a background source of production of the indicator species (1) or (b) a background source of removal of the indicator species (1), wherein the reference data comprises the remote monitoring data from at least part of the tropospheric space (500) for the referral species (2).

4. The computer-implemented method according to any one of the preceding claims, wherein the indicator species (1) is selected from the group comprising: formaldehyde, formic acid, acetic acid, glyoxal, and hypobromite.

5. The computer- implemented method according to claim 4, wherein the indicator species (1) comprises formaldehyde.

6. The computer-implemented method according to claim 4, wherein the indicator species (1) comprises formic acid.

7. The computer- implemented method according to any one of the preceding claims, wherein the referral species (2) as defined in claim 3 is selected from the group comprising: carbon monoxide, nitrogen dioxide, ozone, acetic acid, glyoxal, formic acid, hydrogen cyanide, water vapor, carbon dioxide, chlorine monoxide, hydrochloric acid, ethane, acetylene, isoprene, dimethyl sulfide and hypobromite.

8. The method according to claim 7, wherein the referral species (2) comprises at least carbon monoxide.

9. The computer- implemented method according to any one of the preceding claims 3 and 7-8, wherein remote monitoring data comprises remote monitoring data of at least two referral species (2).

10. The computer- implemented method according to any one of the preceding claims, wherein the enhanced atmospheric methane oxidation is due to a local emission of an enhancing compound (3) from the target object (400) that enhances atmospheric methane oxidation; wherein the indicator species (1) is different from the enhancing compound (3).

11. The computer- implemented method according to claim 10, wherein the enhancing compound (3) enhances atmospheric methane oxidation by locally increasing the concentration of Cl atoms12. The computer- implemented method according to any one of the preceding claims, wherein the method in stage (ii) comprises quantifying a local change in atmospheric methane oxidation over a predetermined time -period.

13. The computer- implemented method according to any one of the preceding claims, further comprising (iii) quantifying an amount of methane removed through the detected enhanced atmospheric methane oxidation.

14. The computer- implemented method according to any one of the preceding claims, wherein the target object (400) comprises a vessel (410) or structure (420), wherein the vessel (410) or structure (420) is selected from the group comprising a ship, a barge, a yacht, an oiler, an off-shore (oil) platform, a tanker, an off-shore wind turbine (425).

15. The computer- implemented method according to any one of the preceding claims, wherein the remote monitoring data for the indicator species (1) comprises a column density of the indicator species (1), wherein the remote monitoring data for the referral species (2), according to claim 3 and any one of claims 7-9, comprises a column density of the referral species (2); and wherein the method in stage (ii) comprises determining a ratio of the column density of the indicator species (1) relative to the column density of the referral species (2).

16. The computer-implemented method according to claim 15, wherein the method in stage (ii) comprises determining an enhancement ratio by comparing the ratio of the column density of the indicator species (1) relative to the column density of the referral species (2) to a background location outside the tropospheric space (500); and wherein the remote monitoring data comprise satellite data.

17. An enhanced atmospheric methane oxidation evaluation system (100) configured for evaluating enhanced atmospheric methane oxidation in a tropospheric space (500) above an ocean or a sea induced by a target object (400); wherein the evaluation system (100) comprises a processing unit (10) configured to (a) receive remote monitoring data from at least part of the tropospheric space (500) for an indicator species (1) related to enhanced atmospheric methane oxidation, wherein the indicator species (1) is not methane, and (b) evaluate the enhanced atmospheric methane removal in the tropospheric space (500) by using the method according to any one of the preceding claims.

18. A computer program product comprising instructions for execution on a control system (300) functionally coupled to the enhanced atmospheric methane oxidation evaluation system (100) according to claim 17, or comprised thereby, wherein the instructions, when executed by the control system (300), cause the evaluation system (100) to carry out the computer-implemented method according to any one of the preceding claims 1-16.

19. Use of the computer- implemented method according to any one of the preceding claims 1-16, the evaluation system (100) according to claim 17 or the computer program product according to claim 18 for determining the validity of methane removal to detect fraudulent behavior.

20. A method for controlling enhanced atmospheric methane oxidation (i) in a tropospheric space above an ocean or a sea and (ii) induced by the target object (400) as defined in any one of the preceding claims 1-16, the method comprising:controlling emission from the target object (400) of an enhancing compound (3), as defined in any one of claims 10-11, in dependence of the evaluating of the enhanced atmospheric methane oxidation induced by the target object (400) according to any one of the preceding claims 1-16.

21. An arrangement (2000) of (a) the target object (400) as defined in any one of the preceding claims, (b) an emitter (200) of the enhancing compound (3) according to any one of claims 10-11, wherein the emitter (200) is comprised by the target object (400) or functionally coupled to the target object (400), and (c) an emitter control system (1300); wherein the emitter control system (1300) is configured to control emission of the enhancing compound (3) by the emitter (200) in dependence of the evaluating of the enhanced atmospheric methane oxidation induced by the target object (400) according to any one of the preceding claims 1-16.

22. A method for functionally coupling an emitter (200) for an enhancing compound (3), as defined in claim 21, to a target object (400), as defined in any one of the preceding claims, wherein the method comprises:functionally coupling the emitter (200) and an emitter control system ( 1300), to the target object (400).

23. The method according to claim 22, wherein the target object (400) comprises a vessel (410) or an arrangement of multiple wind turbines (425).

24. A method for evaluating enhanced atmospheric methane oxidation in a tropospheric space (500) above an ocean or a sea and induced by a target object (400) using remote monitoring data, wherein the method comprises:(i) locally emitting an enhancing compound (3) into the tropospheric space (500) above the ocean or the sea from the target object (400), the enhancing compound (3) causing oxidation of atmospheric methane into an indicator species (1) detectable in a spectral band suitable for ocean observation and different than an infrared band used for direct detection of atmospheric methane, wherein the indicator species (1) is not methane;(ii) acquiring remote monitoring data representing a change in the indicator species (1) in the tropospheric space (500) above the ocean or the sea induced by locally emitting the enhancing compound (3) from the target object (400); and(iii) quantifying a local change in atmospheric methane oxidation due to the local emission of the enhancing compound (3) from the target object (400) based on the change in the indicator species (1) represented by the remote monitoring data.

25. A method for evaluating enhanced atmospheric methane oxidation in a tropospheric space (500) above an ocean or a sea and induced by a target object (400), wherein the target object locally emits an enhancing compound (3) into the tropospheric space (500) above the ocean or the sea from the target object (400), the enhancing compound causing conversion of methane, available in the tropospheric space (500) above the ocean or the sea or emitted from the target object (400) into the tropospheric space (500) above the ocean or the sea, into the an indicator species (1); wherein the enhancing compound (3), methane, and the indicator species (1) are mutually different species; the method comprising:(i) acquiring remote monitoring data representing a change in the indicator species availability (1) in the tropospheric space (500) above the ocean or the sea induced by the local emission of the enhancing compound (3) from the target object (400) by detecting a change in intensity of one or more spectral bands, wherein the one or more spectral bands are suitable for ocean observation of the indicator species (1) and different from one or more infrared spectral bands used for direct a detection of atmospheric methane; and(ii) quantifying a local change in atmospheric methane oxidation due to the local emission of the enhancing compound (3) from the target object (400) based on the change in indicator species ( 1 ) represented by the remote monitoring data.

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