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Environment

Hot Times Ahead for Refrigerants

As worry over refrigerants' threat to the ozone layer recedes, concern over global warming rises

by Marc S. Reisch
October 3, 2005 | A version of this story appeared in Volume 83, Issue 40

COKE IS IT
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Credit: Courtesy of Refrigerants, Naturally
Coca-Cola is rolling out vending machines with non-HFC refrigerants.
Credit: Courtesy of Refrigerants, Naturally
Coca-Cola is rolling out vending machines with non-HFC refrigerants.

A little more than a year ago, Coca-Cola, Unilever, and McDonald's joined forces to find alternatives to the hydrofluorocarbon refrigerants they use in soft-drink vending machines, ice-cream display cases, and restaurant refrigerators.

Urged on by the United Nations Environment Programme and the environmental group Greenpeace, the three food companies, which together operate 12 million coolers and freezers worldwide, met in Belgium at a conference dubbed Refrigerants, Naturally. If current trends continue, the food companies say, the contribution by hydrofluorocarbons (HFCs) to global warming will increase from 1.5% today to as much as 8.6% by 2050. Their mission: to discuss HFC-free refrigeration systems that reduce the global warming impact of their equipment.

Not surprisingly, HFC producers have a different take. Companies such as DuPont, Ineos Fluor, and Arkema don't deny the global-warming potential of their products, part of a $7 billion global fluorocarbon market. HFC-free systems might be right in some cases, but certainly not in all, they say. Buyers of refrigeration units, they caution, must consider total life-cycle costs. That means not only factoring in the environmental impact of the refrigeration system, but also energy efficiency and safety.

Coca-Cola and its allies are undeterred by these arguments and think they can do their part to limit global warming gases through energy-efficient refrigerant systems. By itself, Coca-Cola accounts for only 1% of world compressor sales and less than 0.2% of HFC sales. But Coca-Cola's visibility with consumers means its actions have a powerful effect on the market.

At the Refrigerants, Naturally conference, Coca-Cola's vice president of environment and water resources, Jeff Seabright, said, "We recognized the need to take responsibility on refrigerants early on." In the 1990s, Seabright said, Coca-Cola led a worldwide move to HFCs because they were an ozone-friendly alternative to chlorine-containing chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs). And now, with the widening recognition of HFCs' global warming potential, Coca-Cola is moving away from HFC refrigerants as well.

According to Greenpeace, Coca-Cola didn't come to this realization entirely on its own. The soda company had signed on as a sponsor of the 2000 Olympic Games in Sydney, Australia. The games had a "green" theme, explains Kert Davies, a research director with Greenpeace, and Coca-Cola had planned to sell its beverages at the games from HFC-cooled vending machines.

As Greenpeace saw it, the HFC-chilled machines were an environmental no-no. "We threatened a campaign against them," Davies says. As part of that campaign, the group planned to publicize its own version of Coca-Cola's logo with a polar bear sitting on a block of melting ice.

Greenpeace's German affiliate had already developed a hydrocarbon-driven refrigeration unit and knew that other alternative coolants-such as ammonia and, paradoxically, carbon dioxide-existed. CO2 is the biggest culprit among global warming gases because it is produced in such huge quantities from burning fossil fuels, but on a molecule-to-molecule basis, its global-warming potential is less than that of most fluorocarbons.

Coca-Cola gave in and promised to put alternative chillers in its vending machines by 2004. Greenpeace promised not to go ahead with its planned campaign against Coca-Cola, which has since debuted CO2-chilled vending machines in Japan and Europe.

When Coca-Cola brought together refrigeration users and equipment makers at the Refrigeration, Naturally conference, Greenpeace was delighted. "Greenpeace can dance with corporations as well as dance on them," Davies says.

Fluorine-based refrigerant manufacturers have been on the defensive for years. CFCs were commercially introduced in 1931 as a safe alternative to toxic and flammable refrigerants commonly used then, such as ammonia and sulfur dioxide. In the 1970s, though, CFCs were implicated in the depletion of the ozone layer, which protects the Earth from the sun's harmful ultraviolet radiation. The Montreal Protocol on Substances That Deplete the Ozone Layer, effective since 1989, set a timeline for phaseout of chlorine-containing CFCs and the intermediate HCFCs. HFCs, fluorocarbons with no chlorine and zero ozone-depletion potential, were the refrigeration alternative of choice.

Evidence that the Montreal protocol has led to some recovery of the ozone layer is now in. According to a report from the UN Intergovernmental Panel on Climate Change, chlorine levels in the stratosphere have stabilized and may even be on the decline (C&EN, May 2, page 28). The report also notes that limits on CFCs and HCFCs have reduced the global warming contribution these gases also make.

Susan Solomon, a senior scientist at the National Oceanographic & Atmospheric Administration's Aeronomy Laboratory and a coauthor of the report, points out that in 1990, annual emissions of fluorine-containing compounds-mainly CFCs, HCFCs, and HFCs-had the same warming potential as 7.5 billion metric tons of CO2. That is about one-third of the CO2 produced globally in 1990 by fossil-fuel burning. By 2000, fluorine compounds released into the environment declined to the equivalent of 2.5 billion metric tons of CO2, or about one-tenth of CO2 produced globally by burning fossil fuel.

The main point of the report, Solomon says, is to show that the replacement of CFCs has had a substantial benefit on the climate system. And HFCs, which by and large have a shorter lifetime in the atmosphere than CFCs, offer a "remarkable benefit to the environment."

"We no longer use fluorocarbons in the same way we once did, for instance as solvents to clean electronic chips," Solomon says. "And so fluorocarbons, which have a greater global warming potential than an equivalent amount of CO2, are not as readily vented into the atmosphere. We have a far greater emphasis now on containing the molecule."

In the old days, refrigerators with leaky seals might lose 30% of their coolant charge annually. Today, the average leak rate is 6%, Solomon says. As manufacturers work to push the leak rate lower, attention is shifting to the energy used to run an appliance. And the more energy needed to run a refrigerator, the more CO2 that fossil-fuel-burning plants pour into the atmosphere.

Overall, refrigeration systems based on hydrocarbons might look good if users don't consider life-cycle environmental costs, Solomon says. CO2 could be a good alternative refrigerant, but systems containing the gas pose a real engineering challenge. To be effective, CO2 systems need to operate at pressures eight times greater than fluorocarbon systems, and so leakage and energy efficiency are both a concern.

To Solomon's criticism of alternative refrigerants, Mack McFarland, a DuPont environment fellow, adds that hydrocarbons pose a flammability concern and that ammonia is toxic. When refrigeration units are used in stores, homes, and densely populated areas, "safety is paramount." Only a narrow range of compounds has low toxicity, low or no flammability, and can be designed for minimal leakage, McFarland says. HFCs fit the bill.

The future may bring refrigeration technologies such as thermoacoustic systems that use sound waves to cool. But Mark S. Baunchalk, global business manager for refrigerants at DuPont Fluorochemicals, says he is confident that 10 years from now HFCs will still play a significant role in refrigeration.

DuPont and other HFC makers are working with system manufacturers to improve HFC containment in automotive air conditioners, for instance. Under the aegis of the Society of Automotive Engineers, the Improved Mobile Air Conditioning Cooperative Research Program has 27 sponsors. They include HFC makers such as DuPont, Arkema, Honeywell, and Ineos Fluor; equipment makers such as Delphi, Visteon, and Denso; and automobile manufacturers such as DaimlerChrysler, Ford, General Motors, and Toyota. The group has a goal to reduce HFC-134a (CF3CH2F) leakage 50% by 2007.

According to McFarland, DuPont promotes recycling of used refrigerant where possible. And when that can't be done, it promotes collection and incineration programs to be sure HFCs are not released into the atmosphere. The end-of-life issue is most important, he says. "We are working to be sure that HFCs can be a sustainable solution."

Solomon agrees that end-of-life concerns must be addressed. She is worried about what will happen to "banked" HFCs stockpiled in used and discarded equipment. Because HFC equipment doesn't leak much these days, stockpiles of the gas are growing. Few countries have "an end-of-game plan" for these HFCs, she says.

Greenpeace's Davies points out that no mandatory recycling program is now in place for HFCs. "Even with the best recovery and recycling program, you'll see some losses into the environment, especially from automotive air conditioners," he says. "Add in accidental releases and just plain sloppiness," and the added burden of global-warming gases could be substantial. At best, he says, "mandatory recovery would be a good interim step."

Thomas E. Werkema Jr., vice president of regulatory activities at Arkema, says that "in terms of energy efficiency, a hydrocarbon such as pentane works great compared to HFC-134a." However, he argues that a total-life-cycle climate performance analysis gives HFCs an environmental edge. And, he asks, what about legal issues? If pentane leaks, it can pool at floor level and then ignite. In a risk-adverse society such as in the U.S., that would be unacceptable.

U.S. refrigerator manufacturers are worried about the safe use of refrigerants, says Stephen R. Yurek, general counsel for the Air-Conditioning & Refrigeration Institute. "Hydrocarbons used in small charges may be safe," he says. But where a larger refrigerant charge is called for, the explosive hazards are higher. "That is more risk than most people are willing to take." As Yurek sees it, for most residential and small commercial applications, " really is no alternative to HFCs."

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