Energy and global warming impacts of CFC alternative technologies for foam building insulations
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Chlorofluorocarbons (CFCS) have been used as blowing agents in foam insulation, as the working fluids in cooling and refrigeration equipment, and as solvents in general and precision cleaning applications since their introduction in the 1930s. The number of applications and volumes of CFCs used grew at a tremendous pace during the 1960s and 1970s, but in the mid-1980s it was confirmed that these extremely useful chemicals contribute to the destruction of stratospheric zone and that they are the primary cause of the CFCs have also been found to be second only to carbon dioxide as a factor causing increased greenhouse warming. These chemicals are being phased out of use rapidly to protect the ozone layer and it is very important that the replacements for CFCs do not result in a net increase in global warming by introducing less efficient processes that lead to higher energy use and increased carbon dioxide emissions. A study was conducted to identify those alternative chemicals and technologies that could replace CFCs in energy related applications before the year 2000, and to assess the total potential impact of those alternatives on global warming. The analysis for this project included an estimate of the direct effects frommore » the release of blowing agents, refrigerants, and solvents into the atmosphere and the indirect effects of carbon dioxide emissions resulting from energy use for commercial and residential building insulation, household and commercial refrigeration, building and automobile air conditioning, and general metal and electronics solvent cleaning. This paper focuses on those aspects of the study relevant to building insulation. In general the hydrofluorocarbon (HFC) and hydrochlorofluorocarbon alternatives for CFCs lead to large and sometimes dramatic reductions in total equivalent warming impact, lifetime equivalent C0{sub 2} emissions (TEWI). Most of the reductions result from decreased direct effects without significant changes in energy use.« lessCite
The report estimates total chlorofluorocarbon (CFC) emissions from the various rigid foam manufacturing processes and from the foam products themselves, and examines potential methods for reducing these emissions. Options studied include replacement of CFC-blown products with alternative products not requiring CFCs, replacement of ozone-depleting CFCs with other chemicals less likely to destroy stratospheric ozone, and recovery/recycle of CFCs released during manufacturing processes. In the production of rigid cellular foams, CFCs are used as physical blowing agents to reduce foam density and impart thermal insulating properties. Such rigid foams include polyurethane, polystyrene, polyethylene, polypropylene, polyvinyl chloride, and phenolic foams. Uses of these foams include building insulation, packaging materials, and single-service dinnerware. Depletion of stratospheric ozone through action of halocarbons, particularly CFCs, has been the subject of extensive study and wide debate. Although many uncertainties remain, current scientific evidence strongly suggests that anthropogenic CFCs could contribute to depletion of the stratospheric ozone layer as was first postulated in 1974.
Chlorofluorocarbon
Blowing agent
Polypropylene
Ozone Depletion
Polystyrene
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Tropospheric ozone
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With the increasing concern regarding environmental protection, the problems of stratospheric ozone depletion and global warming become key factors when choosing refrigerants. Traditional refrigerants such as ammonia are satisfactory in terms of environmental protection, while CFCs and HCFCs have relatively high ozone depletion potentials and total equivalent warming impacts. With the gradual prohibition of CFCs and HCFCs, ammonia should be widely applied as one of the natural refrigerants in the heating and ventilation air-conditioning industry, provided that essential safety precautions are ensured.
Ozone Depletion
Global-warming potential
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The earlier discovery of the Antarctic ozone "hole" and current scientific evidence indicate that CFC emissions into the atmosphere deplete the ozone layer and present a long-term threat to the quality of human life. The items of most concern, from an ozone protection standpoint, are the long-lived, fully halogenated compounds—halons, CFCs, and chlorocarbons. Scientific information indicates that most, if not all, of the chlorine or bromine content of these compounds is transported to the stratosphere, where it has the potential to destroy ozone. Furthermore, these compounds remain in the atmosphere for an extended number of years, providing a significant background chlorine concentration. According to DuPont.2 an 85 percent reduction in global CFC emissions from 1986 levels is necessary just to maintain current atmospheric levels of chlorine from these compounds. The refrigerants used within environmental test chambers have been included among those identified as ozone depleting. Specifically, these are CFC-12 and CFC-502. The 1987 Montreal Protocol was revised in June of 1990. Further regulations on CFC products are contained within the Clean Air Bill that is being debated in the Fall of 1990. Restrictions pertaining to CFC-13 are being proposed.
Montreal Protocol
Ozone Depletion
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Montreal Protocol
Ozone Depletion
Chlorofluorocarbon
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Global-warming potential
Tonne
Scope (computer science)
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The report provides technical assistance to aerosol product marketers and fillers in other nations now faced with eliminating chlorofluorocarbons (CFCs) under the terms of the Montreal Protocol. It addresses the issues of hydrocarbon propellant supply, product reformulation, equipment conversion, and safety concerns for both the manufacturing plants and the aerosol products themselves. Because stratospheric ozone provides protection from biologically damaging ultraviolet-B radiation, and because CFCs have been strongly implicated in the thinning of the Earth's stratospheric ozone layer, there is an urgent need to eliminate production and use of the CFCs. In the U.S., CFCs were banned for use as propellants from nearly all aerosol products as early as 1978. In place of the CFC propellants, liquified hydrocarbons such as propane, n-butane, and isobutane were found to be acceptable substitutes for most aerosol products.
Isoprene
Isobutane
Butane
Propane
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Pollution from hydrofluorocarbons (HFC) poses a serious challenge to the environmental community. Released from industrial operations, they have contaminated both the atmosphere and groundwater and are considered persistent in both media.1 For over the past 20 years, the practice of synthesizing hydrofluorocarbons as alternatives to chlorofluorocarbons (CFC) has been conducted in an effort to reverse the effects of stratospheric ozone layer depletion. 2,3 However, in doing so these new fluorinated compounds exhibited an unexpected property as a potent global warming greenhouse gas (GHG) with radiative forcing potentials in the range of 100 to 10,000 equivalents greater than carbon dioxide.4 Conversely, HFCs exhibit desirable properties as precision cleaning solvents due to their low surface energy but that use has lead to releases contaminating groundwater resulting in recalcitrant pollution in the form of dense nonaqueous phase liquids (DNAPL).5 The Environmental Protection Agency (EPA) has recently requested studies on the environmental impact of HFCs with respect to a number of petitions received from various environmental action groups imploring the use of the Montreal Protocol as the vehicle by which to achieve elimination of the compounds from industrial operations.6,7 Additionally, results from studies requested by the international community have shown HFCs to exhibit developmental and neurological damage in animal life along with their impact to humans remaining not completely understood.8,9,10 Therefore, the potential hazards of HFCs to human health and the environment necessitates the development of an effective and environmentally responsible technology for their remediation from groundwater. The National Aeronautics and Space Administration (NASA) has employed the use of various halogenated solvents in its spacecraft cleaning operations at its facilities for many years iv and in that time experienced accidental releases which eventually resulted in environmental contamination.11,12,13 Many of the organic solvents employed in these operations consisted of halogenated compounds with most being partially chlorinated and fluorinated hydrocarbons. Through normal use and operation, releases of these materials found their way into the environs of atmosphere, soil and groundwater. Remediation of fluorinated compounds has not followed the successful path laid by clean-up technologies developed for their chlorinated counterparts.14,15,16,17 Fluorinated compounds are resistant however to those methods due to their unreactive nature stemming from the properties of the strong carbon-fluorine bond. 18 This unique bonding property also ensures that their environmental persistence endures. 19 One particular fluorinated groundwater contaminant, the HFC 1,1,1,2,2,3,4,5,5,5-decafluoropentane (DFP), which serves as an excellent cleaning agent and has been used by NASA since the late 1990’s and still remains in use today, was selected as the focus of this study. 20 For this study, various reductive metal systems were…
Montreal Protocol
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The paper deals with the expected environmental problems arising from the use of halocarbons, the ozone depletion and the global warming. A list of hydrogen – containing halocarbons as well as their mixtures is presented as alternatives to the environmentally harmful halogenated hydrocarbons. This paper intends to make a characterization of some international protocols and restrictions on CFCs, HCFCs and HFCs which affect the refrigeration, heat pumping and air-conditioning industries. Emerging alternatives to the environmentally harmful halocarbons include newly developed refrigerants. A number of candidate working fluids and some possible replacements for the most commonly used refrigerants are summarized. The environmentally acceptable halocarbon refrigerants to active lower environmental impacts during their service life are reviewed.
Global-warming potential
Environmentally Friendly
Halocarbon
Ozone Depletion
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Organic chemicals
Nitrous oxide
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