AFEAS Research and Assessment Program

"All information to date suggests that the proposed substitutes are significantly much better than the current CFCs relative to protection of the ozone layer. The ODPs and GWPs are much smaller than those for the CFCs, and they should not contribute to tropospheric ozone or acid deposition. Consequently, industry is scientifically justified in proceeding rapidly towards the commercialization of these chemicals."

R.T. Watson, M.J. Prather and D.L. Albritton
UNEP/Ozl.Pro.WG.II(1)/CRP.1 13 Nov 1989

The benefits of refrigeration, air conditioning, and energy efficient insulation can be provided conveniently and effectively by hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs). These retain many of the properties of CFCs that are desired by users. However, the presence of hydrogen in their structures means that, unlike CFCs, the alternatives are largely removed in the lower atmosphere by natural processes.
The environmentally important properties of HCFCs and HFCs were reviewed by the Alternative Fluorocarbons Environmental Acceptability Study (AFEAS) in 1989. Leading experts from around the world evaluated the available scientific information. The experts concluded that the ozone depletion potentials (ODPs) and global warming potentials (GWPs) of HCFCs and HFCs are much smaller than those for the CFCs, and they should not contribute to tropospheric ozone or acid deposition. The scientists also identified a number of gaps in what was then known, and concluded that:

"There should be an accelerated research program to ensure the environmental acceptability of all of the proposed HCFCs and HFCs."

R.T. Watson, M.J. Prather and D.L. Albritton
UNEP/Ozl.Pro.WG.II(1)/CRP.1 13 Nov 1989

Fluorocarbon Alternatives to CFCs

HCFC-22	CHClF2
HCFC-123	CHCl2CF3
HCFC-124	CHClF2CF3
HCFC-141b	CH3CCl2F
HCFC-142b	CH3CClF2
HCFC-225ca	CHCl2CF2CF3
HCFC-225cb	CHClFCF2CClF2

HFC-32	CH2F2
HFC-125	CHF2CF3
HFC-134a	CH2FCF3
HFC-143a	CH3CF3
HFC-152a	CH3CHF2
HFC-227ea	CF3CHFCF3
HFC-236fa	CF3CH2CF3
HFC-245fa	CF3CH2CHF2
HFC-245ca	CHF2CF2CH2F
HFC-245eb	CF3CHFCH2F
HFC-365mfc	CF3CH2CF2CH3
HFC-4310mee	CF3CHFCHFCF2CF3

In the interest of good product stewardship and in response to the need for further research, AFEAS was expanded. From 1990 through 1995, the 11 companies participating in AFEAS provided ten million U.S. dollars to fund the research program. The work, which was carried out by independent scientists at academic and governmental institutions, was coordinated with and complementary to national and international studies on the effects of human activities on the environment.

The AFEAS research program had two overall goals:

To identify and help resolve uncertainties regarding potential environmental effects of HCFCs and HFCs.

To stimulate prompt dissemination of accurate scientific information to the research community, government decision makers, affected industries, and the general public.

With the completion of the AFEAS research program, the environmental properties of the alternative fluorocarbons have been more intensively and publicly scrutinized, before significant commercialization, than those for any similar class of compounds. A reliable body of data has been assembled to enable rational decisions to be taken on the utility of the compounds.

Results from scientific studies show that the use of HCFCs - as transitional substances - will reduce the amount of stratospheric chlorine compared to the CFCs they displace. HFCs contain no chlorine and therefore do not contribute to ozone depletion.

The compounds are used in systems which convert or conserve energy and the direct contribution from emissions of the alternative fluorocarbons is usually minor compared with the indirect contribution of carbon dioxide emissions resulting from energy required to operate the systems. An important component of the AFEAS program is the Global Warming and Energy Efficiency Study, co-funded with the U.S. Department of Energy. In this study, the total equivalent warming impact (TEWI) from both direct emissions and indirect energy-related contributions has been quantified for CFC alternative products and technologies, including a wide range of potential new technologies many of which are not yet available to assist in CFC phaseout. Results indicate that HCFCs and HFCs often provide substantial improvements in total energy efficiency over other CFC alternatives.

Unlike CFCs, the alternative fluorocarbons will break down readily in the lower atmosphere. Studies funded by AFEAS, the Commission of the European Communities, and the U.S. Environmental Protection Agency indicate that the decomposition products from most of the compounds will be simple inorganic species already present in the atmosphere. The contribution of these breakdown products to acid deposition will be negligible and, in the breakdown process, ozone pollution will not be formed in the lower atmosphere.

A few of the HCFCs and HFCs can be expected to form trifluoroacetyl halides that will dissolve in water to give trifluoroacetate (TFA) salts. It is anticipated that these salts would then be present in rain or sea water at very low concentrations. Laboratory studies have shown that TFA may be degraded by microorganisms naturally present in soils and sediments. Furthermore, TFA has already been detected at low levels in rain and tropospheric air samples before significant amounts of HFC or HCFC precursors have been produced.

Because the alternative compounds do not accumulate in the atmosphere to the same extent as CFCs, they have a smaller potential to contribute to the greenhouse effect.


	Based on Wigley, T.M.L., Holt, T. and Raper, S.C.B., 1991: STUGE (an Interactive Greenhouse Model): User's Manual, Climatic Research Unit, Norwich, U.K., 44pp.