PartagerNot restricted under the Montreal Protocol, feedstock emissions are delaying the recovery of the ozone layer
Emissions from ozone-depleting substances (ODS) used as feedstocks are projected to be seven times higher than previous assumptions, with a global use that increased by 163% between 2000 and 2024, according to a recent study by an international team of researchers, including IIR STC member Lambert J. M. Kuijpers.
2025 marked the 40th anniversary of the Montreal Protocol, an international agreement that has successfully led to the phase-out of over 100 ozone-depleting substances (ODSs), including chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs), which were widely used in refrigeration, air conditioning, and aerosols (see our previous article).
In contrast, the production and consumption of ODS used as chemical building blocks in the production of other chemical end products – known as feedstock – are not restricted under the Montreal Protocol.
This exemption was based on initial estimates that feedstock-related emissions represented less than 0.5% of global production in 1990 and were expected to decrease between the mid-1990s and 2000.
Contrary to these earlier assumptions, the reported global use of ODS as feedstock chemicals did not decline after 2000 but has increased by 163% between 2000 and 2024, according to a recent study published in Nature Communications by an international team of researchers from Empa, Dübendorf, Switzerland, the University of Bristol, UK, the Massachusetts Institute of Technology, USA, Georgetown University, USA, Nolan Sherry & Associates Ltd, UK, National Oceanic and Atmospheric Administration (NOAA), USA, National Institute for Public Health and the Environment (RIVM), the Netherlands, Utrecht University, the Netherlands, NASA, USA, Kyungpook National University, South Korea, as well as IIR STC member Lambert J. M. Kuijpers, the Netherlands.
The team projected that global ODS feedstock-related emissions would represent 3.6% of the amount produced over the period 2024–2100 in a business-as-usual (BAU) scenario, a seven-fold increase from the earlier estimate of 0.5%.
Without additional measures, these elevated emissions could delay the recovery of the mid-latitude stratospheric ozone layer by 6 to 11 years.
For more information, the study is available in open access in Nature communications.
Sources
Reimann, S., Western, L.M., Lickley, M.J. et al. Continuing industrial emissions are delaying the recovery of the stratospheric ozone layer. Nat Commun 17, 3190 (2026). https://doi.org/10.1038/s41467-026-70533-w