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€SaPRECIS onfronted with alarming drops in stratospheric ozone levels, lawmakers are accelerating the timetables for eliminatine the use and p r o d u c t i l n of ozone-destroying halocarbons. As a result, industry and research institutions are being forced to quickly find replacements for CFCs [chlorofluorocarbons], halons, and other chlorinated and brominated hydrocarbons. Efforts have centered on compounds with zero ozone-depleting potential (zero ODP) and on new technologies that completely eliminate these compounds. The place to evaluate progress toward these goals has become the annual International CFC and Halon Alternatives Conference sponsored by The Alliance for Responsible CFC Policy [Arlington, VA)-an industry-funded coalition. At this year’s meeting in Washington, DC, overflow crowds listened to speakers ranging from basic researchers to refrigerator manufacturers. As a rule, speakers were confident that timetables for phase-outs could be met. However, the two most common questions from audiences were, “When will it be available?” and “How much will it cost?” These concerns are understandable. This year President Bush ordered an end to CFC production in the United States by January 1, 1996.Moreover, the 1990 Clean Air Act mandates that HCFCs (hydrochlorofluorocarbons), the firstgeneration replacements for CFCs that still possess some potential for depleting ozone, be out of new equipment by 2020 and out of production by 2030. Even these timetables may be accelerated. The Natural Resources Defense Council [NRDC) petitioned EPA last year to move up the phaseout date of HCFC-22-a CFC replacement compound used in refrigerators and air conditioners. The NRDC advocates eliminating HCFC22 in new equipment by the year Pdcis articles are reports of meetings of unusual significance, international or national developments of environmental importance, significant public policy developments, and related items.
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To deal with these time pressures, industry has formed alliances to share information and costs of bringing zero-ODP materials to the market. For instance, the R-22 Alternative Refrigerants Evaluation Program (AREP) was formed to identify replacements for HCFC-22, establish testing procedures, and conduct tests. Currently, more than 35 companies are collaborating with AREP, including European and Japanese manufacturers. In addition, another major effort, the Program for Alternative Fluorocarbon Toxicity Testing, pools resources to conduct the expensive toxicity tests for candidate materials. The goal is to replace CFCs or HCFCs with zero-ODP materials that work in existing equipment. As outlined by Michael Hughes of Allied-Signal, Inc. [Buffalo, NY), that means searching for new refrigerants that are nonflammable, noncorrosive, of low toxicity, and reasonably priced. Anticipating potential future environmental concerns, Hughes also listed as de-
2342 Environ. Sci. Technol.. Vol. 26, No. 12. 1992
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sirable a low potential for direct global warming. Given these criteria, hydrofluorocarbons (HFCs)--especially fluorinated propanes-me the most likely substitutes. These compounds generally fulfill most of the above criteria and fall into the proper boiling range required for refrigerants. As an example, Hughes described HFC-245ca [CHF,CF,CH,F, bp= 77.9 “F) as a “good match for CFC11.”Still to be determined are HFC245’s toxicity and effects on lubricants. However, as a rule HFCs have low toxicity and are compatible with CFC lubricants. A different approach to replacement materials relies on identifying HFC blends with appropriate properties. Rajiv Singh, also of AlliedSignal, described a promising zeroODP mixture containing HFC-125 and HFC-143a in a ratio of 45:55% by weight. At this ratio the combination is an azeotrope. Combining the two compounds avoids a pitfall of using pure HFC-143a; it is flammable when present at levels greater than 60% by weight. Nonazeotropic blends also are be-
0013-936W9Z0926-2342$03.00/0 Q 1992 American Chemical Society
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The Environmental Engineering Program of the Department of Civil Engineering at the University of MassachusetMAmherst invites applications for two tenure track positions in Envlronmentai Engineering commencing September 1993. For the first position, candidates should be strong in the biological area of environmental engineering with teaching and research interests in one or more of the foliowlng: biological processes; blorestoration of groundwater aquifers; and/or; biodegradation of hazardous substances. For the second position, candidates should have expertise in a water related discipline, with an interest in: chemical or biological processes; environmental quality models; or: the application of fluid mechanics to the environment. The intent is to fill one positionat the Assistant or Associate Professor level and ¶he other at the Associate or Full Professor level. Applicants for both positions should have an ABET accredited engineerlng degree and must have an earned doctorate in environmental engineering or a related discipline. Preference will be given to candidates with Prcfessionai Engineering Registration. Salaries are commensurate with qualifications and experlence. Responsibilities include graduate and undergraduate teaching and contributions to an active graduate research program. The Environmental Engineering Program is ABET accredited at the advanced level and has seven permanent faculty positions. There are approximately 25 full-time M.S. and Ph.D. students in the Program and 1991-1992 research expenditures were approximately $600,000. interested candidates should send a resume, a statement of research and teaching interests, and the names of at least three references to: Dr. James W. Male, Department of Clvll Englneering, 1SB Maraton Hail, Unlverslty of Massachusetts, Amherst, MA 01003. Applications will be reviewed beginning 1 February 1993 and will be accepted until the positions are filled. The University of Massachusetts Is an A f f i m l l v e Action Equal @pzhmity emplayer.
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ing considered. These mixtures could provide higher energy efficiencies than azeotropes. However, a leaking system could alter the composition of a nonazeotrope and hence affect performance. (A leak in an azeotrope system would not affect composition because the mixture has a single boiling point). Although developed countries are leading the research on CFC alternatives, a promising note at the conference was the significant presence of researchers from mainland China describing their work on alternative refrigerants. (In international negotiations China’s government has been reluctant to abandon its fledgling CFC industry.) For instance, Bin Lu of the Beijing Snow Flake Electric Appliance Group Corporation described experiments with the refrigerant mixture HCFC-BB/HFC152a in a mole ratio of 0.7 to 0.3. Yet another avenue of investigation eliminates halocarbons entirely. Eliezer Manor of IST Engineering (Tel Aviv, Israel) described a 150-BTU refrigeration unit based on a Stirling engine design that uses rotary technology. The unit acts like a heat pump, using helium as the carrier gas. It has fewer moving parts and is smaller in size than a conventional refrigeration unit. In comparison tests after installation into a small refrigerator, Manor claimed that “[the Stirling unit] had the same rate of cooling as a vapor cycle unit, but used 40% less power.” To date, the Stirling unit has run 2000 hours, but Manor believes that with fewer moving parts it should be more reliable than a conventional refrigeration unit. Manor’s company is now constructing a prototype 3-kW unit for air conditioning studies. Another source of ozone-destroying chemicals is the release of halons in extinguishing fires. In many instances, halons can be replaced by CO,. However, in some cases there are no alternatives. The military faces this problem with its use of halons in tanks, armored vehicles, and fighter planes. When these units are damaged or hit in combat, halons automatically flood them and reduce the danger of fire and explosion in less than 250 ms! According to James O’Bryon (Department of Defense, Washington, DC), only halons are currently considered safe in crew compartments at the concentrations required to suppress fire. Where human exposure is not an issue, such as in en-
Environ. Sci. Technol., Vol. 26, No. 12, 1992
gines, replacing halons with bulkier and heavier CO, fire extinguishers poses additional problems of space and, for planes, weight. Currently, the military is stockpiling halon 1301 (to comply with the phase-out of halon manufacture) for expected future needs. At the same time the ubiquitous halon-containing hand-held fire extinguishers are being replaced with CO, canisterswhich, says O’Bryon, should eliminate “about 75% of the releases.” The military is also investigating replacements for halons. Other sessions at the conference dealt with eliminating halocarbons as blowing agents and solvents (especially in the electronics industry) and with alternatives for the fumigant methyl bromide. Yet t h e progress i n eliminating CFCs, HCFCs, halons, and other ozonedestroying chemicals raises a new problem; how to get rid of the unwanted stockpiles. “It will take almost 20 years to destroy what is in the bank,” cautioned John Reed (Environment Canada, Ottawa, Ontario). Furthermore, international agreements specify that destruction methods must meet a minimum destruction level of 99.99%. “That,” said C. W. Lee of EPA (Research Triangle, NC), “is technically feasible.” High-temperature conventional incineration methods can destroy halocarbons to these tolerances, probably with an added cofactor because of the low heating value of many ozone-destroying chemicals. The preferred combustion products are HX, which is removed by a scrubber, and CO,. Other techniques for destruction that are being studied include supercritical water oxidation, plasma discharges, UV photolysis, and biological degradation. However, Maurice Oubre of Dow Chemical (Plaquemine, LA) pointed out that anything destroyed is a lost resource, In dealing with the problem, he recommended a “waste hierarchy’’ of first minimizing production, then recycling or reusing the product, converting to a zeroODP material, and last of all destruction. Next year the conference will return to Washington, DC, to continue highlighting advances. As Hughes warned listeners, “I don’t think we can halt the search for alternatives.”
Alan Newman is an associate editor on the Washington staffof ES&T.
