Mitigation potential of banned hydrofluorocarbons (HFCs) towards global warming – An assessment of Kigali Amendment in the Indian scenario

Abstract

In order to combat the climate change resulting from climate forcing agents such as hydrofluorocarbons (HFCs), Kigali Amendment to Montreal Protocol was proposed in 2016. India gave its nod to Kigali Amendment, where the phase down of HFCs will take place in four steps from 2032 to 2047. In the present study, the emission scenarios for five majorly used HFCs in India, HFC-125, HFC-134a, HFC-143a, HFC-152a and HFC-227ea, with and without Kigali Amendment are developed. In the absence of Kigali Amendment, the GWP weighted emissions of these HFCs are estimated to increase to 0.16 GtCO2 eq. in 2050 from 0.09 GtCO2 eq in 2020. The Kigali Amendment reduction target for these emissions is estimated to be ∼0.03 GtCO2 eq. in 2050. Except for HFC-134a, the other HFCs have almost zero RF by 2050 in the presence of Kigali Amendment. The atmospheric oxidation potential of HFCs calculated through their reaction with atmospheric OH/Cl radicals reveal that HFC-134a is degraded rapidly in the atmosphere, whereas the oxidation potential of HFC-143a is very low. This leads to a longer lifetime of HFC-143a in the atmosphere. Thus, GWP alone is not a metric in determining the climate forcing properties of HFCs. In addition, the atmospheric oxidation potential, product toxicity and chemical stability should also be included as policy-relevant metrics and the Kigali Amendment should be revisited in including the compounds based on these metrics.