Natural refrigerants: CO2, NH3 and hydrocarbons in industry

Natural refrigerants, mainly CO2 (R-744), ammonia (R-717) and hydrocarbons (R-290 and R-600a), are the technical and regulatory alternative to HFCs in industrial refrigeration. They have GWP between 0 and 3 (versus 2,000 to 4,000 for common HFCs), zero ozone depletion potential, and they sit outside the phase-down schedule imposed by the Kigali Amendment, which Brazil ratified in 2022.

The migration is no longer a matter of preference: it is a regulatory, economic and technical shift already underway in the sector. The key question is which natural refrigerant makes sense for which application, and what safety and code precautions each one requires.

Why the migration is happening now

The Kigali Amendment to the Montreal Protocol, signed in 2016, establishes a progressive phase-down of HFCs (hydrofluorocarbons) on a global scale. Brazil ratified the Amendment in 2022 and promulgated it through Decree No. 11,666/2023, committing to reduce HFC consumption by 80% by 2045 (relative to the baseline), with a freeze in 2024 and intermediate cuts of 10% in 2029, 30% in 2035 and 50% in 2040.

Refrigerants widely used in Brazilian industry, such as R-404A (GWP 3,922), R-507A (GWP 3,985) and R-410A (GWP 2,088), are part of the reduction schedule. In practice, this creates two simultaneous pressures on industrial operators:

• Availability: HFC imports depend on an annual quota in tonnes of CO2 equivalent, controlled by Ibama (Normative Instruction No. 29/2023), with national consumption frozen since 2024.
• Horizon: from 2029 the limit falls in steps, and equipment with a service life beyond that date will operate under a lower HFC consumption limit at each cut.

Natural refrigerants do not depend on that quota. They are not subject to the phase-down. And ASHRAE, IIAR and manufacturers have invested heavily in equipment optimized for them.

R-744 (CO2): the transcritical fluid

CO2 as a refrigerant (R-744) is technically different from HFCs in important ways:

• GWP = 1 (the lowest possible value, it is the reference of the scale).
• ODP = 0 (does not destroy ozone).
• Non-flammable, very low toxicity (ASHRAE 34 classification: A1).
• Very high operating pressures, up to 100-130 bar in a transcritical cycle, versus 15-25 bar for typical HFCs.

The high pressure is the critical point: it requires design, welds, valves and instrumentation rated for a severe regime. You cannot directly retrofit an HFC system with CO2, it is a new project.

Typical applications in the industrial sector

• Supermarkets and distribution centers: cascade systems (CO2 low-temperature plus HFC or ammonia for the medium stage) or transcritical booster systems. In the European Union, Regulation (EU) No 517/2014 banned, from 2022, new multipack centralised refrigeration systems for commercial use with a capacity of 40 kW or more that use fluorinated gases with a GWP of 150 or more, except in the primary circuit of cascade systems, where a GWP below 1,500 is allowed. In Brazil, adoption is slower but growing among large retail chains.
• Light and medium industry: beverage, dairy and processing plants. CO2’s advantage: it works well at low temperatures (-40 to -55 °C).
• Where it does not make sense: very large industrial plants (ammonia is still more efficient at high capacity) or hot climates without some form of pre-cooling (the transcritical cycle loses efficiency above 25-30 °C ambient).

In the Smart Cold line, multi-compressor racks can be designed for transcritical R-744 (CO2).

R-717 (Ammonia): the historic industrial standard

Ammonia is the oldest natural refrigerant in industrial use, with systems operating since the 19th century. It has three unbeatable advantages at industrial scale:

• Thermodynamic efficiency superior to virtually any other refrigerant (very high enthalpy of vaporization).
• GWP = 0, ODP = 0.
• Low cost compared to HFCs and even CO2.

The trade-off is safety: ammonia is toxic (ASHRAE 34 classification: B2L, toxic, slightly flammable) and requires strict containment, ventilation, detection and operator training.

Code and safety

In Brazil, industrial ammonia systems are subject to:

• NR-13, pressure vessels (every R-717 system above certain volume and pressure ranges falls under NR-13 with mandatory periodic inspection).
• ANSI/IIAR 2, the American standard for the safe design of closed-circuit ammonia systems; the ANSI/IIAR family complements it with installation (IIAR 4), startup (IIAR 5), inspection, testing and maintenance (IIAR 6) and operating procedures (IIAR 7). It is the technical reference used by engineers in the sector worldwide.
• Training and an emergency plan for leaks.

When it makes sense

• Large industrial plants, especially food, beverages, frozen goods and large-volume refrigerated storage.
• Operations with a dedicated technical team. It is not a refrigerant for an unstaffed machine room.
• Systems with a long planned service life, the initial CAPEX is offset by efficiency over 15-20 years.

R-290 and hydrocarbons: the compact option

R-290 (propane), R-600a (isobutane) and other hydrocarbons are natural refrigerants with very low GWP (GWP 3 for both R-290 and R-600a):

• Good thermodynamic efficiency, comparable to or better than HFCs.
• Normal operating pressures, similar to HFCs (15-25 bar).
• High flammability (ASHRAE 34 classification: A3), which limits the maximum charge per circuit.

Industrial application

The charge restriction (IEC 60335-2-89, revised in 2019, raised the charge limit for A3 refrigerants such as R-290 from 150 g to 500 g per circuit in commercial refrigerating appliances) rules out R-290 in large industrial systems. But it is excellent for:

• Commercial plug-ins and self-contained units, where the total charge is low.
• Small chillers and heat pumps.
• Dedicated applications as a direct replacement for small R-404A units.

In heavy industrial refrigeration, hydrocarbons are rarely the first choice. But for light refrigeration with low GWP, they are unbeatable.

In the Smart Cold line, plug-ins are available with R-290.

Quick comparison table

100-year GWP values per Regulation (EU) No 517/2014 (IPCC AR4 values for HFCs); safety class per ASHRAE Standard 34.

How to choose for your application

The decision is not “which natural refrigerant is best”, it is “which one makes sense for my system, scale and operational context”. The factors that weigh in:

1. Total cooling capacity of the system. Large → ammonia favored. Small → hydrocarbons or CO2. The calculation is covered in the cold room sizing guide.
2. Operating temperature range. Very low (-40 °C or below) → CO2 or cascade.
3. Ambient (average outdoor temperature). Hot → transcritical CO2 requires pre-cooling or loses efficiency.
4. Operational structure. Do you have a dedicated technical team? You can opt for ammonia. Lay operation? Hydrocarbons or low-charge CO2.
5. Code applicable to the sector (food, pharmaceuticals, nearby residential areas).
6. CAPEX vs OPEX. Ammonia has medium CAPEX and very low OPEX. Transcritical CO2 has high CAPEX and OPEX that depends on the climate.

For a new medium-to-large industrial project in Brazil today, the standard technical recommendation tends to be ammonia for heavy industry or transcritical or cascade CO2 for supermarkets and light industry, barring safety or operational constraints that point elsewhere.

Frequently asked questions

Will R-404A stop existing in Brazil?

No. R-404A is not banned, it is under a progressive phase-down. HFC consumption in Brazil has been frozen since 2024, with scheduled cuts of 10% in 2029, 30% in 2035, 50% in 2040 and 80% in 2045, relative to the baseline. Existing R-404A systems can keep operating and receive charge top-ups, but a new project with R-404A will depend, throughout its service life, on a fluid with a declining consumption limit.

Can I retrofit an HFC system to ammonia or CO2?

Not directly. Natural refrigerants have very different thermodynamic properties, pressures and compatible materials than HFCs. A retrofit at that level is equivalent to a new project: piping, compressor, valves, sensors and controls all go. You can reuse the physical structure (machine room, evaporators in some cases), but the system is new.

Is ammonia safe in a food plant?

Yes, as long as it is designed to ANSI/IIAR 2, operated and maintained to the complementary ANSI/IIAR standards (operating procedures in IIAR 7; inspection, testing and maintenance in IIAR 6), and kept in compliance with NR-13 and safety protocols. Most of the world’s industrial refrigerated capacity in food (slaughterhouses, processors, warehouses) uses ammonia. The risk is managed by design (containment, ventilation, detection, emergency valves) and by operator training, not eliminated by the choice of fluid.

Is it worth migrating now or waiting?

For existing systems in good condition: keep operating and plan replacement when they reach end of service life. For new projects: a natural refrigerant is already the defensive choice in 2026, because it stays outside the HFC reduction schedule throughout the equipment’s service life.

Conclusion

The migration to natural refrigerants is already underway and will accelerate. For industrial operators, three practical actions make sense in 2026:

1. Map the current fluid of critical systems and their end-of-life schedule.
2. In new projects, specify a natural refrigerant by default, CO2, ammonia or hydrocarbons according to scale and context.
3. Train the team in the safety and operation of the natural fluids relevant to the plant.

Want Smart Cold’s expert help choosing the right refrigerant for your project? Talk to our engineering team →