Natural Refrigerants: Separating Myths From Facts

FACT:

Ammonia vapor is lighter than air and therefore should rise and dissipate over time and distance. This is not always the case. Dangerous air concentrations of ammonia may remain close to the ground depending upon relative humidity, temperature, and wind speed. Cooler temperatures with high relative humidity will encourage the vapor to hover near the ground. Be aware of downwind depressions that may collect and hold toxic ammonia vapor.

The white cloud that develops with most significant ammonia releases is a poor indicator of the extent of the plume. Dangerous air concentrations of ammonia can extend far beyond the visible white cloud.

SUPPORTING RESOURCES:

• Even the smallest ammonia leak can be dangerous | CPECN
• 7 hospitalized after ammonia leak at Modesto ice cream parlor - CBS Sacramento (cbsnews.com)
• Dangerous chemical leaks have injured workers at one of America’s largest meat processors | CNN Business
• Minnesota Fire Department Response Plan to Ammonia Release

FACT:

Ice quality in skating rinks is determined by only 3 factors: water quality, building conditions, and rink slab temperature.

For typical rink systems, the slab temperature is controlled by flow of a low temperature heat transfer fluid (brine or glycol) under the floor so the ice surface is separated physically from any refrigerant within the refrigeration system (located outdoors or in the machine room). In other words, the rink slab has no way of knowing what refrigerant is inside of the system since it only sees brine, and therefore, as long as the brine temperature and flow remain adequate, the ice is indifferent.

FACT:

"Natural" is a marketing buzz word, not based on engineering or sound science. Refrigerant grade CO₂, hydrocarbons and ammonia sold and used in the HVACR industry are not extracted from nature. Rather, they are made through industrial processes like all other refrigerants.

SUPPORTING RESOURCES:

• An Expert's Take on So-called "Naturals": Future of Refrigerants
• EFCTC Fact Sheet - Natural Refrigerants
• "No Such Thing as Naturals" — Video
• The Cold Truth: A look at what is real, speculation, and hype in the HVACR Industry
• Chemical & Engineering News - CO₂ emissions from Industrial ammonia production

FACT:

GWP is just one factor out of many in the selection of a refrigerant. As highlighted in Section 3.1 of the ASHRAE Position Document on Refrigerants and their Responsible Use: "Selection of refrigerants and their systems must be based on a holistic analysis including energy efficiency and performance attributes, environmental impacts, employee and public safety, and economic considerations. A refrigerant should not be selected based on any one single factor such as GWP, operating pressure, flammability, etc. The wide range of HVAC&R applications and their requirements throughout the world necessitates a variety of refrigerants to meet these needs."

SUPPORTING RESOURCES:

• ASHRAE: Position Document on Refrigerants & Their Responsible Use

FACT:

In the US, public data reported by EPA GreenChill partners indicate that in 2019, CO₂ use as a % of install refrigerant remained <1%. Supermarket retailers have a variety of needs for existing and new stores and technology adoption trends vary by region. CO₂ is not a solution for existing system designs and requires purchase and installation of all new equipment. Supermarkets worldwide have had great success using retrofit refrigerants like Opteon™ XP40 (R-449A), resulting in lower GWP, while staying on track with their sustainability goals. In addition, an increasing number of refrigeration design engineers and end-users are exploring ultra-low GWP HFO solutions with new system architectures as a means to deliver the performance, cost, and sustainability they need to maintain seamless operations.

SUPPORTING RESOURCES:

• Grocers Not Yet Sold On CO₂ Refrigeration Systems | ACHR News
• Grocers Share Concerns Over Alternative Refrigerants | ACHR News
• Grocers' Growing Interest in HFO Solutions

FACT:

CO₂ systems are complex and require high pressures to operate. A disruption to this system, such as a heat wave, can cause shut down.

The loss of a full system charge of CO₂ can lead to loss of refrigeration for up to several days, depending on qualified service technician availability and supply. When a CO₂ system loses full charge, it can freeze up and produce dry ice; in turn it becomes impossible to restart the system until the dry ice is removed. In the case of grocery stores, a loss of refrigeration for several days can result in significant food waste and impact costs for the Grocers and Consumers, as seen during heat waves in recent years.

In order to resolve this issue, retailers are needing to install back-up systems which add additional cost and complexity to an already expensive system.

SUPPORTING RESOURCES:

• CO₂ as a Refrigerant – Five Potential Hazards of R-744 (copeland.com)
• CO₂ Freeze Up: Why it happens, what you can do (harrisproductsgroup.com)
• CO₂: The Incovenient Truth
• Brief Video: Major UK Retailer, ASDA, Chooses A2L Refrigerants
• Emerson E360 Webinar: Preparing for the Safe Use of A2L Refrigerants in Commercial Refrigeration

FACT:

The efficiency of a refrigeration system is largely determined by design, equipment selection and operating conditions. In fact, many modern systems with fluorinated refrigerants have equivalent, or better, efficiency compared to ammonia R-717 plants. Modern refrigeration system designs are constantly being innovated and improved, especially when optimizing energy efficiency. To truly assess the performance of any refrigeration plant requires a deep and expert engineering analysis considering the specific details of the system, application, locality and operational conditions. Blanket statements simply comparing refrigerants, without consideration of other factors is an oversimplification and could lead to potentially inaccurate conclusions.

SUPPORTING RESOURCES:

• System Efficiency is More Important Than GWP
• ORFA Spring 2019 Publication: Efficiency 2.0

FACT:

Due to their high pressure operation, CO₂ systems are significantly more susceptible to loss of full charge during power outages and maintenance. In fact, for safety reasons, emergency discharge valves are built into CO₂ systems to encourage the release of charge if/when required. A 2018 study in the US of ~200 transcritical systems found them to have a very high leak rate (~48.3%), which means each store is losing the equivalent of their entire charge every other year.

In order to avoid business disruptions, most retailers are installing back-up refrigeration systems to cool the receiver or are storing full CO₂ system charges on-site and paying the associated cylinder rental fees. All of these mitigations add cost to the owner/operator.

SUPPORTING RESOURCES:

• Emerson Climate Conversations: CO₂ as a Refrigerant — R-744 Advantages/Disadvantages
• Five Facts to Consider Before Switching to CO₂

FACT:

Although marketed as a "natural" refrigerant, the production of refrigerant grade ammonia contributes significantly to green house gas and fossil fuel use.

SUPPORTING RESOURCES:

• Scientists seek way to make ammonia production more sustainable - Cooling Post
• globalFACT: Do you know where your ammonia refrigerant has been?

FACT

Large carbon dioxide leaks can displace oxygen and cause an asphyxiation risk. Also the Acute Toxicity Exposure Limit (ATEL) for R-744 is 54 g/m3, or 30,000 ppm, and exposures above this even for short times can be of concern. In fact, CO₂ is toxic from 2% (Vol/Vol) concentrations and can be deadly from 25%.

SUPPORTING RESOURCES:

• CO₂ as a Refrigerant – Five Potential Hazards of R-744

FACT:

The total lifecycle emissions from systems operating on “natural refrigerants” are actually higher than F-gases.

Most f-gases are removed from the atmosphere quickly compared to a “natural refrigerant” like CO₂. For example, after 100 years 30% of CO₂ emission persist in the environment for over a thousand years.

SUPPORTING RESOURCES:

• Atmospheric Chemistry and Physics Journal, 2013. 
• The Atmosphere: Getting a Handle on Carbon Dioxide - NASA Science

FACT:

Industrial gases, like CO₂, are more energy intensive than F-gases and can be detrimental to environmental and climate objectives. 

CO₂ is a significantly less efficient refrigerant. Low efficiency means higher electricity consumption and thus higher greenhouse gas emissions. Mitigation technologies exist today to improve the efficiency of CO₂ systems, but in most cases they are complex, and may require the use of water to compensate.

FACT:

Rigorous studies have deemed F-gases safe for their intended use and preferable over “natural” options like propane, ammonia, and CO₂, because these industrial gases are highly flammable, corrosive, or have high operational costs. These risks limit their viability to support global climate goals.

Propane is highly flammable and can be explosive – even static discharge from walking on a carpet can ignite propane accidentally leaked. In fact, a minimum ignition energy to ignite R-1234yf is greater than 5,000 mJ whereas R-290 is less than 0.5 mJ, that's a factor of 10,000X.

Ammonia already has restricted use due to its high toxicity and health risks when it leaks. Ammonia is also flammable and considered a serious health hazard because it is corrosive to the skin, eyes, and lungs, and exposure to 300 parts per million (ppm) is dangerous to life and health.

SUPPORTING RESOURCES:

• Ammonia Refrigeration - Overview | Occupational Safety and Health Administration (osha.gov)
• The potential of propane as a refrigerant - ACR Journal
• Flammability characteristics of HFO‐1234yf - Minor - 2010 - Process Safety Progress - Wiley Online Library
• On the minimum ignition energy (MIE) for propane/air - ScienceDirect

FACT:

While some F-gases can degrade into TFA, it’s a naturally occurring substance and the concentrations currently measured in the environment and predicted in the distant future are well below the thresholds of concern related to human health and the environment. 

TFA does not pose a threat to humans or to the environment because the amounts of it in the environment are significantly below thresholds of (eco)toxicological concern, it is easily excreted by animals, and it has unique qualities that prevent it from bioaccumulating in the food chain.

SUPPORTING RESOURCES:

• UN Environment Programme, “Environmental Effects of Ozone Depletion Amid its Interactions with Climate Change,”  

FACT:

Though CO₂ does not pose the same risks posed by other “Natural” refrigerants, but it is considered an asphyxiant and has a very high leak rate. 

Due to their high-pressure operation, CO₂ systems are significantly more susceptible to loss of full charge during power outages and maintenance. And when they leak, they leak rapidly, which can quickly shut down operations and depending on the application create safety risks since it is an asphyxiant. CO₂ is also heavier than air; this means that in confined spaces a leakage can become extremely dangerous for anybody exposed. At concentrations as low as 2% it is considered as Toxic.

A 2023 report by CO₂ supplier, NASCR, reported that CO₂ supermarkets on average had leak rate of ~100%, essentially emitting the equivalent of the entire charge in one year. In order to avoid business disruptions, most retailers are installing back-up refrigeration systems and/or power generators, ultimately increasing costs for their owner/operator.

SUPPORTING RESOURCES:

• CO₂ Supply - NASRC - Presented at the 2023 FMI Energy and Store Design Conference, Baltimore, MD
• USDA Carbon Dioxide: Health Hazard Information Sheet
• Five Fact to Consider Before Switching to CO₂

FACT:

“Natural” is a marketing buzzword and not based on engineering or sound science. Refrigerant-grade CO₂, hydrocarbons, and ammonia are not extracted from nature. They are made through industrial processes like all other refrigerants.  

“Natural” are the same synthetically manufactured industrial gases that were adopted more than a century ago and broadly abandoned for good reason. Moreover, equipment using industrial gasses like CO₂ are often less energy efficient than the F-gas solutions they are claimed to replace; ultimately incurring higher lifecycle emissions compared to f-gases.

SUPPORTING RESOURCES:

UN Environment Programme, “Environmental Effects" 2022 Assessment Report

FACT:

F-gases are key to achieving EU’s climate targets, strategic autonomy, and innovation objectives.

F-gases help advance EU’s goals by moving heating and cooling away from fossil fuel use and towards energy-efficient solutions, like the adoption of heat pumps. F-gases can also be re-used once equipment reach their end of life, hence contributing to the implementation of circular economies.

Limiting access to f-gases would slow adoption, increase transition costs, create an incredible amount of material waste (from unusable systems), bringing the use and deployment of heat pumps across Europe to a halt.

Rigorous studies have deemed F-gases safe and preferable over certain alternatives. “Natural” options like propane, ammonia, and CO₂ all have high risks including toxicity, flammability, and high operational costs making them non-viable options to achieving EU climate goals.