Environmental Impact: GWP, ODP and Why Charge Size Matters
Two different yardsticks
Every refrigerant has two headline numbers. ODP (ozone depletion potential) is referenced to CFC-11 = 1.0 and measures chlorine/bromine-driven stratospheric ozone destruction. GWP is referenced to CO2 = 1.0 over a 100-year horizon and measures radiative forcing. A refrigerant can be poor on one and acceptable on the other: R-22 has both a high ODP and a high GWP; HFCs such as R-134a have zero ODP but GWP in the thousands.
The impact equation
Total climate impact of a system = direct emissions (refrigerant leaked or vented, weighted by GWP) + indirect emissions (energy used over the equipment's life). For high-GWP systems the direct fraction can dominate, which is why containment, leak detection and end-of-life recovery are the highest-value actions. Recovery and destruction at decommissioning avoids a one-off release of the entire charge - often many tonnes of CO2e in a single afternoon.
Traps in questions
- Treating "zero ODP" as "environmentally harmless" - HFCs are the classic counter-example.
- Forgetting that blends are assessed on the GWP of the mixture, and that leaking a blend can change the remaining composition (fractionation), affecting performance.
- Assuming lower GWP always means safe - flammability (A2L, A3) and pressure change with the refrigerant.
- Mixing up the ozone hole mechanism (chlorine catalysis in the stratosphere) with the greenhouse mechanism.
Rule of thumb
When comparing two options, compare total equivalent warming impact, not GWP alone. A worked check: 10 kg of R-404A (GWP 3922) released = ~39 tCO2e; the same mass of R-32 (GWP 675) = ~6.8 tCO2e. Same leak, roughly six times the climate damage.