The Environmental Protection Agency is clearing the way for additional chemicals to replace hydrofluorocarbons (HFCs), potent greenhouse gases that are used as refrigerants.
An EPA proposal released in late March “would reduce the use and emissions of some of the most harmful HFCs, which are thousands of times more potent than carbon dioxide,” in terms of their global warming potential, says agency Administrator Gina McCarthy. As part of its effort to combat human-caused climate change, the Obama Administration is promoting a global phaseout of HFCs.
EPA’s proposal would also allow use of safer, more climate-friendly alternatives to HFCs. For instance, it would clear the way for more uses of hydrofluoroolefin-1234yf, a substance gaining popularity in automobile air conditioners as an alternative for HFC-134a. HFO-1234yf has less than one thousandth of the global warming potential of HFC-134a. The proposal would allow use of the HFO-1234yf in heavy-duty pickup trucks and vans sold in the U.S.
EPA’s proposal would halt the use of HFCs and methylene chloride for blowing plastic into certain types of closed-cell foams. The move is intended to dissuade companies from considering methylene chloride as an alternative when they switch away from HFCs, the agency says.
Methylene chloride, which EPA regulates as a toxic air pollutant, has a low global warming potential. The agency says its potential for depleting stratospheric ozone is “considered negligibly small.” However, EPA adds, “Recent research indicates that emissions of methylene chloride from multiple industrial sources have been increasing.” This could impact the ozone layer (Nat. Geosci. 2015, DOI: 10.1038/ngeo2363).
Under the proposal, EPA would also allow use of 2-bromo-3,3,3-trifluoropropene (2-BTP) in fire suppression equipment on aircraft that previously relied on halon 1211 or halon 1301. Both halons have high potentials for global warming and stratospheric ozone depletion. According to the proposal, 2-BTP has very low global warming and ozone depletion potentials.
In addition, EPA would allow use of propane as a refrigerant in new commercial ice machines, water coolers, and very low temperature equipment. The proposal, however, would restrict other hydrocarbon refrigerants. For example, EPA would halt the use of propylene and refrigerant-443A, which is a blend of propylene, propane, and isobutane, in new residential heat pumps and air conditioning systems.