Ozone Depleting Substances (ODS)

ODS are internationally regulated by the Montreal Protocol of 1987 and its succession amendments. These are implemented into European legislation by Regulation (EU) 2024/590 on substances that deplete the ozone layer, valid from 11. March 2024. This regulation supersedes the former Regulations (EC) 1005/2009 and (EC) 2037/2000.

The two former ODS Regulations had no impact on chlorinated solvents, but the new ODS Regulation does now for Dichloromethane (DCM) & Perchloroethylene (PER): these solvents have been newly listed on Annex II of the regulation (= substances listed by the EU beyond the requirements of the Montreal Protocol) despite their negligible contribution to ozone depletion, similar to Methyl Chloride (MeCl) that is listed on Annex II since 2010 due to a political agreement. The consequence is that annual volume and use reporting also has to be done for DCM & PER (starting in the first quarter of 2025 with data for 2024), while the substance uses are not restricted at all.

Carbon Tetrachloride (CTC) remains listed in Annex I, as it is a true ODS whose uses are highly restricted by the Montreal Protocol and the ODS Regulation since their establishment. CTC shows a stratospheric ozone-depleting potential (ODP) of 1.1 (reference: R 11 = 1), and also a global warming potential (GWP) of 2200 (reference: CO2 = 1, 100 years horizon), therefore its manufacture, use, recycling, disposal, import and export have been strictly regulated since the implementation of the Montreal Protocol and the EU’s ODS legislation (this applies also for mixtures or wastes containing CTC > 1 %). CTC is almost exclusively used as an industrial intermediate, and only a small fraction is used as a special solvent (‘process agent’) in a few, individually permitted industrial processes or as a laboratory solvent for essential uses only. Emissions during manufacture, transport, use and disposal must be minimised.

MeCl shows a stratospheric ozone depleting potential (ODP) of 0.02 (reference: R 11 = 1), and also a global warming potential (GWP) of 5,54 (reference: CO2 = 1, 100 years horizon). Both figures are at the low end of the scales, because MeCl is fairly degradable in the atmosphere (half-life ~ 1 y) and in turn defined by the WMO as a ‘very short-lived substance’ (VSLS), that is not controlled by the Montreal Protocol. MeCl is almost exclusively used as an industrial intermediate, and only a small fraction as a low temperature solvent in a special industrial process fur butyl rubber production, or as a laboratory reagent. It is a highly flammable gas that is used under practically strictly controlled conditions (closed systems) for explosion prevention, that is stored and transported pressure liquefied.

It should be noted that not only the ODP is relevant for ozone depletion, but also the global emissions. In this respect, man-made industrial emissions are not at all relevant compared to the several million tons of MeCl naturally produced per year by algae, bacteria, fungi and certain plants in the oceans and in soil all over the world, as well as by biomass and coal burning.