CO₂ refrigeration systems are optimal options for operators prioritizing sustainability. This statement rings true for several reasons:

• CO₂ has a much lower global warming potential (GWP) than nearly all other refrigerants. Several of the hydrofluorocarbon (HFC) refrigerants that are commonly used in supermarkets boast high GWPs, i.e., R-507 has a GWP of 3,985; R-404A, 3,922; R-410A, 2,088; and R-22, 1,810. By contrast, CO₂, commonly recognized as R-744, has a GWP of 1.
• GWP numbers are especially important when examining the leakage rate of supermarket refrigeration systems. A report by the Environmental Investigation Agency revealed that 55% of its surveyed stores in the U.S. were actively leaking refrigerant. On average, a single supermarket emits 875 pounds (400 kg) of HFCs annually. This is equivalent to the carbon emissions from 300 cars.
• Supermarket refrigeration systems are heavy consumers of energy. These refrigeration systems account for 40%-60% of total supermarket electricity usage, which is about 2%-3% of total commercial building energy consumption in the U.S. According to a study authored by Sawalha et al, CO₂ systems have higher coefficients of performance (COP) than HFC systems, meaning CO₂ systems are more efficient when comparing their power output versus input. R-744 achieves this elevated COP rating because its systems are generally smaller in size, thanks in part to smaller compressors and pipe diameters.

Case in Point

Estes Refrigeration Inc. is a Richmond, California-based family-owned low-temperature refrigeration business that specializes in the service, engineering, and installation of environmental rooms. The company, which has been in business since 1953, has a very close relationship with The Roche Group, owner of Genentech. Genentech issued a sustainability directive restricting the company’s refrigerant use. Going forward, the company pledged to only use refrigerants with GWPs of 10 or lower. As its primary service provider, Estes was tasked with meeting this demand.

“This severely limited our refrigeration options to hydrocarbons [HCs], CO₂, and ammonia,” said Mark Doninelli, vice president, Estes Refrigeration. “Ammonia and HC refrigerants have their own set of challenges, including flammability. While CO₂ has high pressures, when examining the class of A1 refrigerants, I believe it’s the most future-proof option of the bunch.”

Since its first project in 2012, Estes Refrigeration has designed and built approximately 50 CO₂ systems.

“CO₂ is going to be the top choice for the foreseeable future,” he said. “It’s not a blend, so we don’t have to worry about troublesome glides. It will most likely continue to be our first choice going forward.”

AAA Refrigeration Service Inc. in Bronx, New York, has built or provides service to 37 locations that utilize R-744. Peter Savage, project manager, controls division, said AAA jumped aboard the R-744 bandwagon very early, largely because of its sustainability benefits.

“Other than R-717, there is no other refrigerant with a lower GWP,” he said. “R-744 is a highly efficient heat transfer element and is less expensive than most other synthetic refrigerants.”

Adam Dykstra, refrigeration operations manager, DeTroye Electric Service, Oostburg, Wisconsin, said CO₂ refrigeration systems simply run cleaner.

“From a service standpoint, there’s no issue with blowing a little bit of gas off here and there, since it’s not going to harm the environment,” he said. “Also, I don’t have to worry about recovering it either, which saves us a ton of time.”

While CO₂ systems may be more expensive upfront, their environmental benefits and ability to meet any future regulations make them an optimal option for contractors and facility managers.

“Sure, they’re going to cost more to install, but, at the end of the day, all of that can be justified through cost of ownership and stability,” Dykstra said. “These systems will never be phased out based on their GWP, which, for contractors and customers, is priceless.”