Carbon dioxide could be the next big compound used in cooling machinery in North America, including transport refrigeration. Yes, the same CO2 that government regulators work to control as a greenhouse gas responsible for global warming might be embraced as a more environmentally friendly compound to keep our perishables at safe temperatures.

CO2 is a “natural refrigerant” that’s thousands of times safer for the environment than current compounds that damage the atmosphere and the Earth as a whole, says Carrier Transicold. It’s already using CO2 as called R-744 in stationary systems in the European Union, which has approved it, and in transport refrigeration units on ocean containers.

“We are committed to expanding our proven, environmentally responsible natural refrigerant systems for road transport,” said David Appel, president, Carrier Transicold & Refrigeration Systems, in a statement issued this week. “Specifically, we are building on our expertise with the natural refrigerant carbon dioxide (CO2), which has a significantly lower global warming potential (GWP) than current synthetic refrigerants and their alternates.”

Truck and trailer reefer units in North America now use R-404A, one of a number of hydrofluorcarbon (HFC) refrigerants, Carrier explained. R-404A is many times safer than previous compounds, including the R-12 (called Freon by its maker, DuPont) that was used for many years but is now outlawed in the U.S.

The European Union is forcing the phase-out of R-404A in favor of safer alternatives, the company said. One is R-452A, a three-component blend that includes a hydrofluoroolefin (HFO) and has a global warming potential about 45% percent lower than R-404A. R-452A is awaiting approval by the U.S. Environmental Protection Agency for use in the United States.

If approved by the EPA, R-452A could become an interim option for U.S. truck and trailer customers seeking more environmentally responsible refrigerants, Carrier said. 

But Carrier wants to go further.

“Carrier Transicold’s greater goal for transport refrigeration significantly surpasses the benefits of R-452A,” Appel said. “The natural refrigerant CO2 is cost-effective, readily available worldwide and has a GWP of only 1, which is roughly 2,000 times better than R-452A (GWP 2,140) and 4,000 times better than R-404A (GWP 3,922).”

Why is CO2 bad when emitted from exhausts of engine and power plants, but good as a refrigerant? Because it’s recycled as a useful compound instead of being blown into the atmosphere and it’s held inside the refrigeration unit. If released, such as during improper servicing, it does no more harm than if it had been emitted in the first place.

CO2 has been used before as a refrigerant, but requires high pressure to operate, and compressor outlet temperatures are also high. So manufacturers turned to other compounds, according to narratives on the Internet. Now those two drawbacks are seen as advantages: The high pressure creates density that boosts efficiency, and, in automotive air conditioning applications, high outlet temps defrost windshields quickly.

Carrier said it has successfully applied CO2 in both stationary commercial refrigeration and marine transport applications. Since its introduction in 2004, more than 1,600 supermarkets across Europe have adopted Carrier’s CO2OLtec commercial refrigeration system.

In 2013, Carrier Transicold launched the NaturaLine, claimed to be the world's first marine container reefer unit using CO2 refrigerant, which can lower carbon emissions by 28% compared to previous systems, according to the company. The NaturaLine unit is available to shipping lines and container leasing companies worldwide.

As for CO2 being readily available, it’s as close as our breaths. Exhale and there it is. I think I’ll breathe into a bag and sell it.