Kigali Amendment HFC Phasedown: What It Means for US Compliance

What the Kigali Amendment Is and Why It Exists

On October 15, 2016, the 197 Parties to the Montreal Protocol adopted an amendment in Kigali, Rwanda, adding hydrofluorocarbons to the Protocol's list of controlled substances. The goal: an 80–85% reduction in global HFC production and consumption by the late 2040s.

HFCs entered widespread use as replacements for ozone-depleting CFCs and HCFCs — themselves phased out under earlier Montreal Protocol action. The substitution solved the ozone problem but created a new one. HFCs carry global warming potentials (GWPs) hundreds to thousands of times higher than CO2. R-410A has a GWP of 2,088. R-404A has a GWP of 3,922. These are not trace industrial gases — they are in air conditioners, supermarket refrigeration systems, and cold-chain equipment worldwide, and they leak.

The UNEP OzonAction Kigali factsheet projects that full implementation could avoid up to 0.5°C of global warming by 2100. Pair the phasedown with cooling-equipment efficiency improvements and that figure roughly doubles to approximately 1°C — one of the largest single contributions any international agreement can make to climate targets.

For compliance officers, the significance is simpler: this is the treaty that made the current refrigerant supply constraints legally binding on the United States.

How the Three-Group Phasedown Schedule Works

The Kigali Amendment divides countries into three groups with different reduction timelines. Progress is measured in metric tonnes of CO2 equivalent — each HFC is weighted by its 100-year GWP, so a kilogram of R-404A counts for 3.922 tonnes of CO2e in the accounting. See the US HFC phasedown allowance schedule by year for the specific step-down percentages that apply to domestic operations.

The group structure matters for US supply chains. HFC imports from Article 5 Group 1 countries (notably China, a major refrigerant manufacturer) are subject to the trade provisions under Montreal Protocol Article 4, which restrict transactions with non-ratifying parties. As those countries proceed through their own phasedown, global supply dynamics will shift further.

US Ratification: From Montreal Protocol Leadership to Senate Vote

The United States has led Montreal Protocol enforcement since the treaty's inception — but Kigali ratification took six years after adoption. The US Department of State confirmed that the Senate gave advice and consent on September 21, 2022, with formal ratification deposited at the United Nations on October 26, 2022.

The vote was bipartisan and drew support from both environmental advocates and the HVACR industry — a coalition that reflected the economic stakes. US manufacturers of low-GWP alternatives and HFO-based refrigerants had a direct commercial interest in ratification, which would lock in global demand for the next generation of products they were already producing.

Ratification also activated trade restriction provisions. Under Montreal Protocol Article 4, parties can restrict HFC imports from and exports to non-ratifying countries. This affects procurement decisions for any US company sourcing refrigerants from international suppliers.

From Treaty to Regulation: How Kigali Becomes 40 CFR Part 84

International treaties do not self-execute as domestic law in the United States. Congress must pass implementing legislation. For Kigali, that legislation is the American Innovation and Manufacturing (AIM) Act, codified at 42 U.S.C. § 7675. The AIM Act authorizes EPA to phase down bulk HFC production and consumption through an allowance system. EPA codified the phasedown schedule at 40 CFR 84.7; the allowance program began January 1, 2022.

The AIM Act targets mirror Kigali's non-Article 5 schedule precisely:

Allowances are GWP-weighted and non-transferable across calendar years. The statute explicitly states they do not constitute a property right — meaning EPA can adjust the program without triggering takings claims. For a full analysis of how the allowance system operates, see the Federal Register rulemaking on allowance allocation methodology.

The legal framework connecting the treaty to facility-level obligations runs from the Montreal Protocol through the AIM Act to EPA's regulatory text. Every obligation in your refrigerant management program traces back to a Montreal Protocol commitment.

Subpart C: From Treaty Obligation to Facility Rules

The macro phasedown caps mean nothing if refrigerant continues to leak undetected from equipment in the field. That is the problem Subpart C addresses. Effective January 1, 2026, 40 CFR Part 84 Subpart C covers any appliance with a full charge of 15 pounds or more of a regulated HFC substance.

The core obligations:

• Owners and operators must calculate leak rates each time refrigerant is added to a covered appliance and initiate repairs when those rates exceed regulatory thresholds.
• Repairs must be completed within defined timelines using certified technicians (§ 84.106).
• Automatic leak detection systems are required for certain high-charge appliances under § 84.108 — a requirement that extends beyond what Section 608 of the Clean Air Act imposed.
• Reclamation requirements under § 84.112 ensure recovered refrigerant is returned to specification before reuse, tightening the loop on refrigerant that remains in circulation.

These facility-level rules are how the treaty's macro objective — cutting HFC consumption — translates into measurable emissions reductions at the equipment level. Without them, allowance caps on production and import would be undermined by uncontrolled field losses.

Climate and Market Drivers Behind the Agreement

The urgency behind the Kigali Amendment was data-driven. Global HFC emissions were growing at more than 10% annually before controls. Without action, EPA projections indicated HFCs could reach 3.5–8.8 billion metric tonnes of CO2e per year by 2050 — a volume that would negate substantial progress on fossil fuel emissions reductions. Full Kigali implementation is estimated to prevent more than 80 billion metric tonnes of CO2e through 2050.

The agreement also reshaped global refrigerant markets. The Multilateral Fund under the Montreal Protocol provides financing to Article 5 nations to support technology transitions — creating export markets for US manufacturers of low-GWP alternatives. Industry investment in HFO refrigerants and natural refrigerants (ammonia, CO2, propane) accelerated in parallel with treaty momentum, with manufacturers timing capital expenditures to regulatory certainty.

For compliance officers, the market consequence is direct: high-GWP refrigerants like R-410A and R-404A are structurally more expensive and harder to source at each allowance step-down. That trajectory is locked in by treaty.

Practical Implications for US Operations

Related Resources

• AIM Act authority and structure under 40 CFR Part 84 — How the domestic statute implements the Kigali obligations and what EPA is authorized to do
• US HFC phasedown allowance schedule by year — Specific allowance caps, baseline years, and step-down dates for US operations
• Legal framework connecting the treaty to facility-level obligations — The regulatory chain from Montreal Protocol to Subpart C enforcement

Sources

• EPA — Background on HFCs and the AIM Act
• EPA — Recent International Developments under the Montreal Protocol
• EPA — Frequent Questions on the Phasedown of Hydrofluorocarbons
• US Department of State — U.S. Ratification of the Kigali Amendment
• UNEP OzonAction — The Kigali Amendment: HFC Phase-down Factsheet
• UNEP Ozone Secretariat — Kigali Amendment Overview
• Federal Register — Phasedown of HFCs: Allowance Allocation Methodology for 2024 and Later Years
• eCFR — 40 CFR Part 84 Subpart C: Management of Regulated Substances