Emissions associated with mining operations in Africa’s Copperbelt can be quantified from space, according to new research led by the National Center for Atmospheric Research (NCAR).

The new open-access study is published in Geophysical Research Letters, and shows for the first time that satellite monitoring can provide valuable information on the impact of the copper and cobalt mining boom on air quality in nearby towns and villages. The research also opens the door to the possibility of remotely monitoring increases and decreases in mining activities in a region of the world where surface monitoring is scarce and reporting by mine operators can be inconsistent or altogether absent.

Africa’s Copperbelt straddles Zambia and the Democratic Republic of Congo, which produced 73% of the world’s supply of cobalt in 2022, according to the Cobalt Institute. Cobalt production in the Copperbelt increased about 600% between 1990 and 2021, according to data from the US Bureau of Mines and the US Geological Survey.

The vast majority of cobalt is produced as a byproduct of copper mining, though some copper mines do not produce any cobalt.

Most of the energy consumed in copper and cobalt mining—including the operation of large machinery and electricity production—is generated by burning diesel fuel—which produces large amounts of NO_x emissions.

To quantify the emissions, the research team turned to data from the TROPOspheric Monitoring Instrument (TROPOMI) onboard the European Space Agency’s Copernicus Sentinel-5 Precursor satellite (S-5P). TROPOMI can monitor a number of trace gases important for air quality, including NO_x.

While biomass burning, urban activity, and other industrial operations beyond mining also produce NO_x—as do some natural processes—the researchers found that they could distinguish the emissions from copper and cobalt mines in the data. They also found that the annual emissions from each mine strongly correlated with their annual metal production.

Average nitrogen dioxide detected by the TROPOMI instrument onboard the S-5P satellite over the Democratic Republic of Congo. The image shows the significant increase in nitrogen dioxide over a copper/cobalt mine (circled in yellow) compared to the city of Kolwezi (circled in yellow). Image courtesy: Pepijn Veefkind, KNMI

The S-5P satellite that carries TROPOMI is polar-orbiting and passes over any given location on the Earth’s surface once a day, limiting the number of observations over the Copperbelt. A geostationary satellite over the continent could provide a much more in-depth picture of emissions in the region, providing hourly instead of daily observations, according to Pieternel Levelt, director of NCAR’s Atmospheric Chemistry Observations and Modeling Lab and senior author of the paper. Currently, there are no geostationary satellites over Africa or anywhere in the global South.

Resources

• S. Martínez-Alonso, J.P. Veefkind, B. Dix, B. Gaubert, N. Theys, C. Granier, A. Soulié, S. Darras, H. Eskes, W. Tang, H. Worden, J. De Gouw, and P.F. Levelt (2023) “S-5P/TROPOMI-derived NO_x emissions from copper/cobalt mining and other industrial activities in the Copperbelt (Democratic Republic of Congo and Zambia)” Geophysical Research Letters doi: 10.1029/2023GL104109