More to offer from the Montreal protocol: how the ozone treaty can secure further significant greenhouse gas emission reductions in the future

Figures & data

Table 1. Emissions linked to fluorochemical production, illegal production or unknown sources.

Chemical	World Meteorological Organization (WMO) (2022) GWP	Estimated Emissions (Gg/yr)	Estimated Emissions (Million Tonnes CO2e/yr)	Observation Year(s)	Description of Emission Sources	Reference
HFC-23	14,700	17.20	252.84	2019	Top-down estimate of global emissions. By-product emissions from production of HCFC-22, as well as from pyrolysis of HCFC-22 to produce TFE and HFP. Potential by-product emissions from production of HFC-32, HFC-125 and other controlled substances. Also includes emissions from banks of niche refrigerant and fire suppression uses.	World Meteorological Organization (WMO) (2022)
CFC-12	12,500	18.30	228.75	2014–2016	Top-down estimate of unexpected emissions excluding emissions from banks. Emissions are linked to illegal production and use or other unknown sources.	Lickley et al. (2021)
CFC-11	6,410	23.20	148.71	2014–2016	Top-down estimate of unexpected emissions excluding emissions from banks. Emissions are linked to illegal production and use or other unknown sources.	Lickley et al. (2021)
CTC	2,150	34.00	73.10	2020	Top-down estimates of global CTC emissions are 44 ± 15 Gg/yr from 2016 and 2020. Once legacy emissions from landfills and contaminated soils (5-10Gg) are subtracted, total emissions from production and unexplained sources are 44–10 = 34Gg. Unexplained emissions are assumed to be from feedstock and chloromethane production or other unknown sources. CTC is a feedstock to various CFCs, HFCs, HFOs, & chloroform, which is used to make HCFC-22.	World Meteorological Organization (WMO) (2022) (Update to Sherry et al, 2018)
CFC-113	6,530	7.8	50.93	2014–2016	Top-down estimate of unexpected emissions excluding emissions from banks. CFC-113 is a common feedstock used to make HFC-134a, TFA, pesticides and chlorotrifluoroethylene (CTFE) which is a precursor used to make fluoropolymers.	Lickley et al. (2021)
HCFC-22	1,910	21.40	40.87	2019	Bottom-up estimate of emissions from feedstock production and use. Feedstock to TFE/HFP to produce PTFE and other fluoropolymers.	World Meteorological Organization (WMO) (2022)
PFC-318	10,600	2.50	26.50	2020	Top-down estimate. By-product of hexafluoropropylene (HFP) production, which is used to make fluoropolymers including PTFE (aka Teflon)	World Meteorological Organization (WMO) (2022)
CFC-115	9,630	n/a	14.30	2020	Top-down estimate of global emissions. No significant banks from end uses. By-product of HFC-125 production	Western et al. (2023)
CFC-113a	3,930**	n/a	14.00	2020	Top-down estimate of global emissions. No significant banks from end uses. Feedstock/By-product in HFC-125, HFC-134a, HFO-1334mzz production; feedstock in production of TFA & pesticides	Western et al. (2023)
CFC-13	16,300**	n/a	12.00	2020	Top-down estimate of global emissions. Unknown sources. Potential use as a feedstock for CFC-11, however emissions have not declined in recent years with CFC-11 emissions.	Western et al. (2023)
CFC-114a	7,410**	n/a	6.00	2020	Top-down estimate of global emissions. No significant banks from end uses. Feedstock/intermediate in production of HFC-125 and HFC-134a	Western et al. (2023)
HCFC-133a	378	2.30	0.87	2016–2019	Top-down estimate of global emissions. No known dispersive end-uses or banks. Feedstock to produce HCFC-123, CFC-113a.	Vollmer et al. (2021)
HCFC-132b	332	1.10	0.37	2019	Top-down estimate of global emissions. No known dispersive end-uses or banks. Likely by-product of HFC production.	Vollmer et al. (2021)
CFC-112a	3,550**	n/a	0.10	2020	Top-down estimate of global emissions. No significant banks from end uses. Unexplained, previous uses as a solvent and feedstock in fluorovinyl ether production	Western et al. (2023)
HCFC-31	85	0.71	0.06	2016–2019	Top-down estimate of global emissions. No known dispersive end-uses or banks. By-product of HFC production.	Vollmer et al. (2021)

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Data availability statement

The authors confirm that the data supporting the findings of this study are available within the article.