Sensors
- GHGSat: Commercial hyperspectral imager operating in the shortwave-infrared around 1.65 µm. Published detection limit for methane is approximately 100 kg per hour per pixel at roughly 25 m ground resolution per scene. Designed for point-source attribution at individual landfill cells or gas wells. Tasked on demand; no fixed revisit.
- MethaneSAT: EDF-funded satellite launched 2024, measuring methane and CO₂ in the 1.65 µm and 2.3 µm SWIR bands. Designed to detect area sources as well as point sources, with sensitivity down to roughly 2 parts per billion volume at regional scale. Covers large areas per pass, useful for establishing whether a landfill is a dominant regional source.
- Sentinel-5P TROPOMI: ESA atmospheric sounder with a 7 x 5.5 km pixel at nadir (improved to 5.5 x 3.5 km from August 2019). Daily global coverage. Detects column-averaged methane concentrations to better than 1% precision. Too coarse for individual-site attribution but essential for regional background concentration and for identifying anomalous clusters that warrant higher-resolution tasking.
- EMIT (Earth Surface Mineral Dust Source Investigation): NASA imaging spectrometer on the International Space Station, operating 380–2500 nm including the methane-sensitive SWIR window. Spatial resolution approximately 60 m. Primarily a mineral-dust mission but has been demonstrated in peer-reviewed work to detect large methane point sources, including landfills, opportunistically. Coverage is ISS ground-track dependent, not systematic.
Why a closed landfill is not a closed question
A landfill that stopped accepting waste twenty years ago can still generate substantial methane. Organic material buried under anaerobic conditions continues to decompose for decades. The gas migrates laterally through permeable soils, following the path of least resistance, and has been documented reaching residential foundations hundreds of metres from the waste boundary. In the United Kingdom, the Environment Agency's guidance on gas migration risk zones extends to 250 metres from a landfill edge as a default screening distance, though actual migration depends heavily on local geology.
For property buyers, lenders and planners, the question is not simply whether a landfill exists nearby but whether it is currently emitting, at what rate, and in which direction. Planning registers and historical maps identify sites; they say nothing about present-day flux. That is where satellite observation adds something that desk research cannot.
What shortwave-infrared absorption spectroscopy actually measures
Methane absorbs solar radiation strongly near 1.65 µm and 2.3 µm. A hyperspectral sensor looking down through the atmosphere sees less reflected energy at those wavelengths above a methane plume than it does in clean air. The deficit, compared to a modelled clean-atmosphere baseline, is proportional to the column concentration of gas between the surface and the sensor. This is passive remote sensing: no active illumination required, which keeps costs down and makes it practical at satellite scale.
The physics sets hard limits. Clouds block the signal entirely. Low sun angles in winter at high latitudes reduce signal-to-noise. Sensors with coarser pixels, such as TROPOMI, average the plume signal across a large area, making a concentrated point source appear weaker than it is. This is why the workflow requires multiple instruments: TROPOMI for regional context, GHGSat or EMIT for site-level attribution, and wind-field data to reconstruct source location from observed plume geometry.
Translating plume data into property risk scores
A raw methane concentration map is not a risk score. Converting it into something useful for a mortgage valuer or a planning officer requires several additional steps. First, the detected emission rate must be compared against the site's permitted or estimated capacity: a small landfill emitting at the high end of its expected range is a different signal from a large site emitting modestly. Second, the plume geometry, combined with prevailing wind climatology, produces a probability surface showing which directions downwind carry elevated concentrations most frequently. Third, local soil permeability data, where available, modifies the lateral migration estimate.
The output is a distance-and-direction risk surface, not a binary safe/unsafe boundary. Properties directly downwind on permeable ground score differently from properties at the same distance upwind on clay. That granularity is what makes satellite-derived data useful beyond what a simple buffer analysis on a planning map provides. Honest caveat: satellite detection cannot substitute for on-site borehole gas monitoring where regulatory decisions are being made. It is a screening and prioritisation tool.
Sensor limits that buyers and lenders should understand
GHGSat's published minimum detection threshold of around 100 kg per hour is meaningful context. The UK Environment Agency has reported that well-managed landfills with gas capture systems may emit below this threshold, meaning a clean GHGSat observation does not confirm zero emission. Smaller or older sites with degraded gas capture may emit at detectable rates; larger sites in active decomposition phases typically emit well above the detection floor.
TROPOMI's 5.5 x 3.5 km pixel means that in urban areas with multiple potential sources, attributing elevated column methane to a specific landfill rather than to nearby agriculture, wastewater treatment or industrial activity requires careful wind-back modelling. EMIT's 60 m resolution is better for attribution but its ISS-track coverage means a given site may be observed only a handful of times per year. None of these sensors provides the continuous monitoring that a borehole gas probe does. The satellite layer is most valuable for initial screening, for monitoring sites where ground instrumentation is absent, and for providing independent verification of reported emission reductions.
The analytic workflow from tasking to valuation report
A practical engagement begins with TROPOMI archive analysis, which is freely available and covers every landfill on Earth daily. Anomalous column methane concentrations above the site or its downwind sector, persistent across multiple overpasses, justify commercial tasking of GHGSat or a request for EMIT scene review. The higher-resolution observation, combined with ERA5 or similar reanalysis wind fields at the time of acquisition, allows Gaussian plume inversion to estimate surface emission rate and source location within the landfill boundary.
That emission estimate feeds a soil-migration model parameterised with publicly available geology. The resulting risk surface is delivered as a GIS layer that integrates directly with property valuation workflows. For lenders assessing portfolios near multiple sites, batch processing across dozens of landfills in a single region is straightforward once the workflow is established.
Regulatory and market context that makes this timely
Methane disclosure requirements are tightening. The EU Methane Regulation, which entered into force in 2024, imposes monitoring and reporting obligations on fossil-fuel operators, and similar pressure is building on waste sector operators. In several US states, landfill gas monitoring and reporting under EPA regulations already generates public data that can be cross-validated against satellite observations. Where regulatory data exists, satellite analysis can identify discrepancies between reported and observed emission rates, a due-diligence signal that sophisticated lenders are beginning to request.
Property markets near landfills already show measurable price discounts in published academic literature, though the magnitude varies widely by country, site type and local awareness. The novel contribution of satellite methane mapping is that it can distinguish between a well-capped, low-emitting site that carries mostly stigma risk and a genuinely high-emitting site that carries physical risk. That distinction has direct implications for how large a discount is warranted and whether it is stable over time.
Typical figures
| GHGSat spatial resolution | Approximately 25 m per pixel |
| GHGSat minimum detectable emission | ~100 kg CH₄ per hour (published figure) |
| TROPOMI pixel size | 5.5 x 3.5 km (post-August 2019) |
| TROPOMI revisit | Daily global coverage |
| TROPOMI methane precision | Better than 1% column-averaged dry-air mole fraction |
| EMIT spatial resolution | ~60 m; ISS ground-track dependent coverage |
| Spectral bands used | SWIR 1.65 µm and 2.3 µm methane absorption windows |
| TROPOMI archive depth | From May 2018 (Sentinel-5P launch) |
| Key limiting condition | Cloud cover blocks all SWIR methane retrievals |
| Typical deliverable format | GeoTIFF concentration grids, GIS risk-surface layers, PDF valuation summary |
Analytics Satellize can run
| Regional methane anomaly screen | TROPOMI column-methane time-series analysis with wind-back attribution | PDF report flagging landfill sites with persistent above-background column concentrations, ranked by anomaly magnitude |
| Point-source emission rate estimate | Gaussian plume inversion applied to GHGSat or EMIT scene with ERA5 wind fields | Estimated kg CH₄ per hour per site, with uncertainty range, delivered as structured data table |
| Plume direction probability surface | Wind climatology convolved with observed plume geometry to produce directional frequency distribution | GeoTIFF risk surface showing probability of elevated methane exposure by compass sector around each site |
| Property-level proximity risk score | Plume surface combined with soil permeability classification and distance decay model | Scored address list or polygon layer compatible with standard GIS and valuation platforms |
| Regulatory cross-validation flag | Comparison of satellite-derived emission estimates against publicly reported regulatory figures | Discrepancy alert report for due-diligence use, noting confidence level and data vintage |
| Multi-site portfolio screen | Batch TROPOMI archive query across user-supplied list of landfill coordinates | Ranked portfolio dashboard identifying sites requiring higher-resolution follow-up tasking |
Who does the work
We can get this done for you. Satellize runs its own analyst desk and a strong science team. You do not buy a data feed and work out what it means; our people source the imagery, run the analysis described on this page, and hand you the answer with its confidence limits stated. Discuss this requirement.