When a French steel plant slowed down, satellites caught it from orbit

When SatVu's thermal satellite caught Blast Furnace 1 going dark at ArcelorMittal's Dunkerque plant in March 2023, Floodlight's CO₂ measurements told the same story from a different orbit.

ArcelorMittal's Dunkerque plant in northern France has been producing steel since 1991. At full capacity, the facility turns out roughly seven million tonnes of finished steel a year. Like every blast-furnace integrated mill, it runs continuously when it is running, and the volume of CO₂ leaving its stacks tracks closely with how many furnaces are active and how hard they are being pushed.

The right facility for a stress test

That tight relationship between operations and emissions is what makes Dunkerque an ideal test case for satellite-based monitoring. If satellite observations can detect a change in furnace status from orbit, they can plausibly do the same across the rest of the world's heavy industry, where on-site instrumentation is uneven and self-reporting is not always timely. The research question Floodlight and SatVu set out to answer together was direct: do changes in the thermal profile of a facility correspond with measurable shifts in its CO₂ emissions?

The thermal record from HotSat-1

SatVu's HotSat-1 satellite captures high-resolution thermal imagery, which made it possible to identify when individual blast furnaces at Dunkerque were running and when they were not. The thermal record showed that Blast Furnace 1 was permanently shut down on March 30, 2023, that Blast Furnace 3 went offline briefly and resumed in early April, and that Blast Furnace 4 stayed dark until October. With those operational timestamps in hand, Floodlight ran a top-down CO₂ analysis against the same windows.

Three CO₂ snapshots, one operational story

The benchmark month was February 2023, before any of the shutdowns and well clear of any lingering COVID disruption. Floodlight processed an OCO-2 overpass for that period using its proprietary plume dispersion methodology, modeled the wind transport between the facility and the satellite sounding points, and arrived at a monthly emission estimate of 328,455 tonnes of CO₂. That figure became the all-furnaces-active baseline.

For the next test, Floodlight targeted June 2023, when Blast Furnace 1 was permanently offline and Blast Furnace 4 was also down. The same methodology returned 161,663 tonnes of CO₂ for that month, roughly half the baseline. The thermal data and the CO₂ measurements were telling the same story without sharing any source.

Finally, Floodlight ran the analysis for September 2024, after Blast Furnace 4 came back online. The result was 230,905 tonnes of CO₂, sitting between the two earlier readings exactly as the operational profile would predict.

What it means for monitoring at scale

The conclusion is straightforward but powerful. A facility's atmospheric signature shifts in lockstep with what happens inside the gate, and satellite measurements catch that shift with no instrumentation on site, no self-reporting, and no delay. For the next generation of MRV requirements, regulatory disclosures, and creditor due diligence in heavy industry, that signal-grade independence is the difference between a number that can be argued with and a number that cannot.

The Dunkerque analysis was carried out using publicly available OCO-2 satellite observations and SatVu's HotSat-1 thermal imagery. It demonstrates a methodology that Floodlight now applies routinely across cement, refining, chemicals, and other heavy-industry asset classes for institutional clients.