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The production and release to the atmosphere of CCl3F and CCl2F2 (chlorofluorocarbons CFC 11 and CFC 12)
AmwSpherir tiiF+rintcd in Great
I Vol. 20. No. 6. pp. 1077-1085.
0004-698l/a6 kwmon
1986.
Britain.
53.00+0.00 Joumrlr Ltd.
THE PRODUCTION AND RELEASE TO THE ATMOSPHERE OF CC13F AND CC12Ft (CHLOROFLUOROCARBONS CFC 11 AND CFC 12) P. H. GAMLEN,B. C. LANE and P. M. MIDGLEY ICI Americas Inc., Wilmington, DE 19897, U.S.A. and J. M. STEED E. I. du Pont de Nemours and Company Inc., Corpus Christi, TX, U.S.A. (First receiued 26 Nouember 1984 and in jnul form 30 October 1985) Abstract-In order to understand the present concentration distribution of CCl,F and CC12FI in the atmosphere and their atmospheric lifetimes, accurate data on the global production and release of these materials are needed. This papezrreports improvements in the understanding of certain production and use categories which increase the accuracy of the estimates of these releases. However, lack of recent production data from certain sources prevents the total world production, and hence release, estimates from reflecting similar accuracy. Key word index: Atmosphere, atmospheric abundance, concentration. lifetime, chlorofluorocarbon, production. release.
1.
INTRODUCTION
Accurate global production and release data are vital to an understanding of the present concentration distribution of CCllF (CFC 11) and CCIIFl (CFC 12) in the atmosphere and to the analysis of their atmospheric lifetimes. For several years, the Fluorocarbon Program Panel of the Chemical Manufacturers Association (CMA FPP) has published annual estimates of the production, sales and release to the atmosphere of CFC 11 and CFC 12. This paper reports the resuIts of a study to improve these estimates and to reduce the uncertainties in the published figures. Up to 1980, these figures (CMA, 1981a, b) were based on release scenarios developed by McCarthy and his co-workers (McCarthy et al., 1977) for various defined end use categories. Subsequent improvements in the understanding of certain production and use categories for CFC I 1 and CFC 12 increase the accuracy of the estimates of releases for these categories, but lack of recent production data from other sources seriously limits the accuracy of estimates of global production and release (CMA, 1982a, b. 1983). This paper addresses the following aspects of release estimation: the collection and estimation of production data, the categorization of production into various end uses, and the pattern of release to the atmosphere from these end uses. Finally the significant uncertainties in the release estimates are considered.
2. PRODUCTION ESTIMATES
2.1. Reporting companies Production of CFC I1 and CFC I2 is reported. annually on a confidential basis to an independent accountant, Alexander Grant and Co., by the CFC producing companies who are members of the CMA FPP (see Table 1).Alexander Grant supply CMA FPP with the total production figure for CFC 11 and CFC 12 for these companies. The participating companies include all producers in the U.S.A., Canada, the EEC and Japan. Production in countries such as Australia, Argentina, Brazil, Mexico, South Africa, Spain and Venezuela is reported either directly or through companies which participate in the CMA FPP programme. The reported figures are essentially sales figures, that is production corrected for inventory changes, and are not corrected for any CFC 11 or CFC I2 which is manufactured but lost to the atmosphere during the manufacturing or packing processes at the production site. This particular emission is considered in the release section of this paper. 2.2. Other CFC producers Not all CFC producers are members of the CMA FPP. Production from non-participating companies has been estimated by the CMA FPP from the limited information available as follows.
1078
P. H. GAMLEN
Table 1. Chlorofluorocarbon manufacturers involved in the production survey The following is a listing of the reporting companies including any related subsidiaries and/or joint ventures that reported production and release data throueh 1982: I Akzo Chemie, BV (Holland) 2 Allied Corporation (U.S.) (a) Allied Canada Inc. (Canada) (b) Qu~o~icos, SA (Mexico) 3 Asahi Glass Co. Ltd (Japan) 4 Atochem (France) formerly Chioe Chimie and PCUK [a) Pacific Chemical Industries Pty Ltd (Australia) (b) Ugimica, SP (Spain) (c) Prcduven (Venezuela) 5 Australian Fluorine Chemical Pty Ltd (Australia) 6 Da&in Kogyo Co. Ltd (Japan) 7 E. 1. du Pont de Nemours & Company Inc. (U.S.1 (a) Du Pont de Nemours (N~er~nd} NV (b) Ducilo, SA (Argentina) (c) Du Ponl do Brasil, SA (Brazil) (d) Halocarburos, SA (Mexico) 8 Du Pont Canada, Inc. (Canada) 9 Essex Chemical Corporation (Racon) (U.S.) 10 Hoechst, AG (West Germany) (a) Hocchst Iberica (Spain) (b) Hoechst do Brasil Q&mica e Farmaceutica, SA II Imperia] Chemical Industries PLC (England) (a) African Explosives & Chemical Industries Ltd 12 ISC Chemicals’ Ltd (England) 13 Kaiser Aluminum & Chemical Corwration (U.S.) 14 Kali-Chemie Akliengesekchaft (W&t Germany) (a) KaIi-Chemie Iberia, SA (Spain) 1s Mirsui Ftuor~hern~ats Co. Ltd (Japan) 16 Montefluos SpA (Formerly Montedison SpA) (Italy) 17 Pennwalt Corporation (U.S.) 18 Showa Denko, KK (Japan) 19 SICNG (Greece) 20 Union Carbide Corporation (U.S.r (Union Carbide ceased production in 1977).
India. Two producers exist (Aegis Chemical Industries Ltd and Navin Fluorine Industries) whose production capacity is reasonably well known. Since their production is relatively small, errors in these estimates are unlikely to produce any signifi~nt error in the world production total. Navin Fluorine Industries recently agreed to report their production for 1983 which will be included in the 1984 CMA FPP report. Argentina Two independent producers (Tool Research SA and IRA SA) operated in Argentina during the 197Os,but both companies closed in 1979. Estimates of their relatively small production during the 1970s have been revised and, as in the case of India, errors here do not introduce any significant error in the world production total. People’s
Repub~jc oj China. CFCs are known to he
the People’s Republic of China (PRC) but the production capacity is believed lo be still relatively
produced in
small. For lack of hcttcr information,
the PRC pro-
CMA FPP estimates. U.S.S.R.The only published data for U.S.S.R. production of CFC 11 and CFC 12 are for the years 1968-1975 (Borisenkov and Kazakov, 1980). For the duction
is assumed to he zero
in the
er al
principal product, CFC 12, these data show an average compound growth of 18% per year throughout the period. Until I982, these figures were incorporated into the CMA FPP estimates, together with an assumption of zero production before 1968 and 3 >Aper year growth after 1975 (CMA, 1981b). In reality, it is unlikely that U.S.S.R. production could have commenced in I968 at such significant levels, and it therefore seems more reasonable to assume a gradual build-up in production from 19.50 to 1968. More recent CMA FPP estimates (CMA, 1982a. b, 1983) have assumed that the historic growth of 18 “,i per year continued after 1975. The continued application of this assumption over severaf years is likely to be wrong and contributes an increasingly large uncertainty in the estimate of U.S.S.R. production and hence in the estimates of world production and release. The U.S.S.R. production of CFC 11 and CFC 12 estimated on this basis has grown from 8 % of the total world estimate in 1975 to 22% in 1982, the latest year for which estimates have been publish~ (CMA, 1983). It is believed that the U.S.S.R. production capacity for CFC 11 and CFC 12 in fact totals no more than 70-80 x lo6 kgcompared to the 1982 CMA FPP estimate of production of 123 x 10’ kg. This is a matter of serious concern and the FPP has endeavoured to obtain more reliable data. To date, these have proved unobtainable. Eastern Europe. There are believed to be a number of CFC plants in the countries of Eastern Europe other than the U.S.S.R., specifically in the German Democratic Republic, Czechoslovakia and possibly in Hungary and Poland. No information has been pubfished on the production in these countries, other than an estimate in the IMOS report (1975) of uncertain quality. In the CMA FPP world estimates, the production for Eastern Europeexcluding the U.S.S.R. was set at 15 7; of the U.S.S.R. production for each year. This is also likely to be increasingly in error if the U.S.S.R. figure is in error.
2.3. Uncertainties
in the production
estimates
The uncertainties in the production data from the CMA FPP reporting companies are probabfy not more than _+O.S%, once plant losses have been separately accounted for (see fugitive releases below). The principal sources of uncertainty in the world production estiinate have been arbitrarily set at the values shown below to permit a sensitivity analysis. PRC production: the figure of zero presently used obviously underestimates any true production figure. In the uncertainty analysis in section 5, an upper limit of pr~~tion in the PRC is set at 1 ‘%,of the world figure. U.S.S.R. production since 1975 has been estimated assuming 18 y0 growth per year. The estimated range for uncertainty analysis is 3-21:~ per year. Eastern European production excluding the U.S.S.R.: the present a~umption of IS:4 of the U.S.S.R. production is unsupported by any firm data.
1079
Production and rckase to the atmosphere of &C&F and CClzFFI
For uncertainty analysis, the limits ased were zero production and twice the current estimate. Inclusion of the 18 % per year increase for U.S.S.R. production has become a significant factor in estimating world production of CFC 11 and CFC 12 (see Fig. 1). In the absence of reported data from the U.S.S.R. and other producers, the CMA FPP has reluctantly discontinued its estimates of world production. Starting in 1984, the annual report will on11 include reported data.
3. DEFlNlTlON
OF END USE
CATEGORIES
In order to calculate the overall release rate of CFC 11 and CFC 12, the time delay for release from their varied uses must be estimated. McCarthy et al. (1977) proposed grouping the uses of CFC 11 and CFC 12 into six categories, where the uses within each category had a similar release pattern. This approach has been applied in the CMA FPP estimates (CMA, 1981a, b). The six categories given by McCarthy et al. are: Aerosols Heretically sealed refrigeration (long lifetime, about 12 y) Non-hermetically sealed refrigeration (short lifetime, about 4 y) Closed cell foams Open cell foams Other uses. Each year the participating companies submit to Alexander Grant, along with production numbers, the sales in each category. Alexander Grant compile the
figures and transmit the totals in each use category to CMA FPP. It is important to note that the end uses are not known for the non-reporting companies and, in
release calculations, this estimate-dproduction is assumed to have the same end use split as the participating company data. The reliability of the end use analysis is thought to be accurate for the major markets, i.e. aerosols, refrigeration and foam. This confidence arises from the way company sales data are normally assembled and the separate nature of these three broad areas. Care is needed with the ~tego~tion of sales to refrigemtion equipment manufacturers who use chlorofluorocarbons both as refrigerant (almost entirely CFC 12), and in pour-in-place foam insulation for the refrigerator itself (almost entirely CFC 11). Of less certain reliability is the subdivision within each category. The sub-division of foam into closed cell and open cell types can be checked to some extent by comparison of published CMA FPP data for the U.S.A. only (CMA, 1981~:collected as described above but for U.S.A. producing plants only), and data in the Rand report (Rand, 1980) for the year 1976. Since the Rand report concerns itself only with U.S.A. domestic consumption, whereas the CMA FPP data refer to U.S.A. domestic plus export sales, exact agreement would not be expected. The CMA FPP reported that 55 % of CFC 11 usage in foams went into closed cell foam. This agrees well with the 52 % figure determined by Rand’s market survey of end users. The same agreement is not found for the subdivision of the refrigeration category. The Rand report identifies only domestic refrigerators and freezers as having the 12-y product use lifetime of the hermetically sealed
45-I
5 1960
I 1962
I 1964
c 1966
I,
1968
,
1970
,
19721974
,
1976
(
1976
(
1960
]
,
1982
1984
Fig. 1. Annual production of CFC 11and CFC 12,1%0-1983.1 I-CMA and 12-CMA arc reported production of CMA FPP participating companies for CFC 11and CFC 12,respectively. 1l-world and 12.world arc estimated total production for these compound% Ettimates for world production were discontinued in 1983. The annual production reports arc available from the Chcmicaf Manufacturers Assoc&tion (CMA 1983,1984).
P. H. GAMLENet al.
1080
category. Market analysis by Rand shows these uses consumed 2.7 x lo6 kg of CFC 12 and no CFC 11 in 1976. The CMA FPP report however shows 33 x lo6 kgofCFC 12and3.6 x lo6 kgofCFC 11 inthis category for 1976. A market survey (Ward, 1982, Private Communication) of the U.S.A. refrigerant market confirms the Rand analysis and suggests that the error is in the McCarthy ef al. categorization used in the CMA FPP estimates. One source of error is the definition of he~eti~Ily sealed which, in a strict mechanical sense, would mean uses where there is no rotating shaft seal retaining the refrigerant. Under such a definition, reciprocating compressors would be classed as hermetically sealed, whereas Rand shows that the initial charge is lost in about 4 y, and this use is better classified in the short lifetime category. Since 1982, the definition of long and short lifetime refrigeration categories for the CMA FPP release estimates has been based on market research analysis (CMA, 1982a, b). For CFC 11, ail reported refrigeration sales are placed in the short lifetimecategory. For CFC 12,3.5 7; of the total is placed in the long lifetime category, and the balance in the short lifetime category. However, for CFC 12 in particular, this introduces some uncertainties. It has been noted (CMA, 1982a) that placement of only 3.5”/, of CFC 12 in this category, whilst appropriate for the U.S.A., would not be applicable for the rest of the world. U.S.A. refrigeration is dominated by automobile air conditioning (in 1976, 41 x IO6 kg), whereas in Europe this use is negligible. However, the errors introduced by the 3.5 y; assumption are not considered serious, since the U.S.A. accounted for 607; of the total refrigeration sales by the participating companies in 1976, and 54 % in 1980. A recent survey of Western Europe showed that 22 % of the 22 x lo* kg consumption in refrigeration was in the long lived category (EFCTC, 1982). The two surveys (Ward, 1982, Private Communication; EFCTC, 1982) together cover some 70% of CFC 12 refrigeration sales by the participating companies. Combining their findings suggests that, of the total CFC 12 sold for refrigeration, 8 + 2 % is of the long lived type and this paper adopts this figure. Further uncertainty arises over the assumptions made for the remaining 30 4; of the sales. The principal remainjng uncertainty in the end use categorization is the ~sumption that the use pattern for CFCs produced by CMA FPP companies is the same for the rest of the world. The errors this introduces into the release estimate can be assessed by examining two limiting assumptions. Firstly, that all the non-reporting companies production is used in aerosols with a fast release and secondly, that all this production is released after a 4-y delay (see section 5). To summarize, the subdivision of chlorofluorocarbon production into end use categories is described by the following equation: p, = R(P), + S(A), + S(LRB -t-S(SR), + S(OC), + S(X), + S(O), + @A),
where P = production, R = release and S = sales and the end use fractions are given by F = fugitive emission A = aerosol LR = long lived refrigeration SR = short lived refrigeration UC = open cell foam CC = ciosed cell foam 5 = other, see section 4.7 SA = stock adjustments t = year. For refrigeration and where
where c @A), ‘-t 0 t
S(LR), = O.OSS(TR), for CFC 12 S(SR), = S(TR), for CFC 1I
TR = total refrigeration.
4. RELEASE SCENARIOS 4.1.
Fug&e
emissions
Not all the CFC 11 and CFC 12 manufactured is sold. Some escapes from plant vents, and some is lost during the packing operation. These losses are immediate, with no delay between production and release. In recent release calculations (CMA, 1982a, b), 2 % of the total product has been estimated to be lost in this way and a higher proportion of this will be the more volatile CFC 12. These fugitive emissions have been incorporated into release estimates by adding 2.5 “/, of CFC 12 production, and 1.5 y0 of CFC 11 production into the prompt release category. More recently, a carbon mass balance has been carried out on about 60% of the production from reporting companies to determine these fugitive losses more precisely (CMA, 1982~).This survey showed that the percentage ofCC1, taken into the manufacturing plants that does not appear in the CFC 11 and CFC 12 sold or stocked, or as known byproducts such as CFC 13, averaged 2.7 + 0.6% for 1969-1979. Applying an assumption that 66 % is lost as CFC 12 and 33 % as CFC 11 gave an estimate of fugitive emissions of 3.3 % of CFC 12 production and 2.0% of CFC 11 production (CMA, 1983). Hence R(F), = 0.02 f, for CFC I 1 = 0.033 P, for CFC 12. (The un~rtainty in the 2.7 % figure is best regarded as the standard error of the mean, i.e. for 1969-1979 where e = f0.6 for an individual annual determination, the standard error in the mean is +-O&J1 I = * 0.2.) 4.2. Aerosols McCarthy et al. (1977) calculated that release from aerosols, on average, took place 6 months after sale, so that only half of aerosol sales were released in the year of sale, and half the following year. R(A), = 0.5 S(A), +0.5 S(A),,_ II. The &month dehy was based on U.S. usage in f 977; at
Production and rckasc to the atmosphere of CC&F and CCltFt that time the major aerosol market. A survey in Italy, Ciermany, France and the U.K., now the major producers of CFC-propelled aerosols, supports this figure (Mills, 1982, Private Communication). The data showed a release delay of approximately 24 weeks. These data suggest that the uncertainty in the &month figure is not more than 1 month. 4.3. Long-lived refrigeration Analysis by McfZarthy et at. (1977) for domestic refrigerators and freezers indicated an average lifetime of 12 y (Q = f 4 y), with a 2 % loss to the atmosphe~ during filling. The Rand report (1980) broadly sup ports this scenario, stating that the manufacturing losses include a 3 % loss on filling and testing. Rand also includes a further 5 y0 loss from system rework. The 12 f4 y lifetime assumed by McCarthy et ol. differs slightly from the Rand estimate of 1.5 % failure per year plus a 17-20 y appliance lifetime. However the differences are not significant sources of error in the overall release estimate, because the percentage of CFC 12 sales in this application is small. Consequently the McCarthy et al. analysis is retained in the CMA FPP estimates. 4.4. S~orr-lied refiberation
use
McCarthy et al. (1977) proposed a 4-y life for this category (a = f 2 y). Most of this use is in industrial refrigerators. This does not imply that the refrigerator life is 4 y but that the refrigerant charge life is 4 f 2 y and the refrigerator is recharged several times during its lifetime. The detailed data in the Rand report (1980) on original equipment manufacturer use and service use for various refrigeration applications can be used to test the validity of the McCarthy scenario. All the sign~~nt uses identified by Rand in this~tego~ have refrigerant lives of 3-5 y and thus substantially confirm the McCarthy scenario. 4.5. Open cell foam A 6-month delay similar to that for aerosols was used by CMA FPP to calculate the release from open cell foam (CMA. 198lb). More recent analysis, however, suggests that CFC 11is released within a few days or weeks after it is used in making the foam. A 2-month release delay is now considered to be a better estimate (CMA, 1982a, b). Thus R(OC), =0.83S(~+O.l7S(~_*. 4.6. Closed cell &am The Rand report (1980) subdivides the closed ceil foam category into rigid polyurethane and isocyanurate foams (CFC 11) and non- urethane foams, polystyrene and some extruded polyoiefins (mainly CFC 12 when the blowing agent is a chlorofluorocarbon). A breakdown for this category follows. 4.61. CFC 12. Most oftheuseofCFC 12forclosed cell foam is in polyolefin foam with a very thin cross section. McCarthy et a!. (1977) quoted data showing
1081
that the CFC is lost from the product to the atmosphere within 2 y, 75 % being lost within 1 y. In this paper, half is considered to be lost in the year of manufacture, and half in the following year. Hence for CFC 12, R(E),
= 0.5 S(CC), +0.5 S(CC),,_ ,,.
The Rand report (1980) states that for non-urethane foams, such as polystyrene sheet, 45-79 % of the CFC 12 is released during manufacture and the rest during the first year and that ~lyoiefin foams are also prompt emitters. Only for polystyrene board does the loss rate equate to that of rigid urethane foams (see 4.6.2). However, in 1976, polystyrene board constituted only a small fraction of the total U.S.A. CFC 12 use in the closed cell foam category (about 20%: Rand, 1980). Hence, provided that the polystyrene board fraction is as small in the rest of the world, the McCarthy ef al. algorithm appears adequate. 4.6.2. CFC 11. The release of CFC 11 from closed cell foam (principally rigid polyurethane foam) is the least well-defined of ail the cateogories. The three principal factors which determine the actual release are: production loss, diffusion loss during product use, and losses on disposal. The current CMA FPP estimate uses the McCarthy et nl. (1977) analysis of a production loss of lo%, followed by a loss of 4.5 % per year for 20 y, representing a combination of product lifetime and diffusional loss. A production loss of IO:,; has been substantiated by market research surveys by Rand (1980) and A. D. Little Inc. (Little, 1980). although a BASF report (BASF, 1981) suggests a 5 % loss. The subsequent loss rate after manufacture is more contentious. An earlier assumption that the rise in thermal conductivity of foams over time was necessarily associated with WC loss has been questioned by B~ndreth and fngresoll (1980). They showed that this change was principally associated with air ingress, which raised the pressure inside the microcells to one atmosphere from the initial 0.5 atmosphere. Under controlled laboratory conditions, diffusion of CFC 11 from polyurethane foams in an accelerated test is very slow, indicating a lifetime of the order of 100~. On the other hand, some commercial glass filled poiyisocyanurate foams lose CFC 11 quite rapidly, indicating a lifetime of around 10 y (Rasmussen, 1982). Analysis is further complicated because the products into which the foam is incorporated have use lifetimes ranging from 1 to 80 y. Disposal practices for these products determine whether the CFC continues to be lost slowly, is released on disposal (as assumed by McCarthy et al.), or is destroyed on disposal by incineration. The A. D. Little report (1980) studied rigid urethane foam in the U.S.A. It did not directly address the question of the release rate of CFC 11 in normal use since this release rate was, and still is, poorly quantified. However, it addressed the other parameters involved, such as release during manufacture, normal use lifetime prior to disposal, disposal practices etc. A.
P. H. GAMLEN et al. D. Little’s findings are summarized in Tabld 2. A. D. Little found that on average, 11 % of CFC 11 was emitted during manufacture, and also that disposal practices were 95% burial and 5 % incineration. Emissions at, and subsequent to, burial are complex. One draft analysis (EPA, 1980) assumed that half of the remaining CFC It was released on disposal, and half continued to dfluse slowly. For the construction categories, demolition practices would suggest that all the remaining CFC I 1 wilt be released on disposaf. For transport uses, a similar assumption seems reasonable. Household appliances are fargeiy buried with some crushing, and refease of only 25 % at disposal seems reasonable. Weighting these assumptions by the percentage of their market share allows an average release rate on disposal by burial to be calculated. For disposal by incineration, the amount of CFC 11 released unchanged must be small. Since the proportion of foam disposed of in this manner is also small, release of CFC following incineration is set at zero. To summarize: I 15; Initial release Fate on disposal 5 %---no release (incineration) of remaining CFC 11: 75 y<---immediate release 20%--continues at normal release rate
The A. D. Little lifetime data show a reasonably Gaussian distribution with an in-use lifetime of 26 y (a= *13y). The range of uncertainty in the present estimate of the rate of CFC loss during the product lifetime can be evaluated estimating the fastest and slowest likely relase rates. A reasonable, fast loss rate assumes that 10% of CFC 11 is lost during manufacture and the remainder is lost over 10 y. The stow rate assumes a 10&y diffusion half life, in the form of i 1 y/,initial foss, followed by 1% per year diffusion losses but with disposal rate and subsequent emissions following the A.D. Little (1980) data. The releases in this category for these three conditions are given in Table 3. A best estimate of release is perhaps the average of the fast and slow loss rates. This figure is very close to that calculated using the McCarthy et al. scenario, which therefore continues to be used for the CMA FPP calculations. The slow and fast release scenarios are used in section 5 to estimate the associated uncertainties. 4.7. Other This category currently comprises about 7”,; of production. The major uses identified are those of CFC 12 in steriiant gas mixtures and the use of CFC 1I
Table 2. Rigid urethane foam use in the U.S.A. (Little, 1980) CFC 11 eonttnt “/,
Foam
Use lifetime
Use
type
(Y)
Commercial construction
39.1
ss 4.4 LB 17.8
35
Residential construction
2.4
Industriaf construction
12.9
Household refrigeration Household freezers Commercial refrigeration Transport
8.0 8.7 4.1 12.4
Packaging Marine floatation
5.4 4.7
Polystyrene
2.1
FS 13.6 PIP 3.3 ss 0.5 LB 1.9 ss 0.7 FS 10.8 PIP 1.4 PIP PIP ss FS PIP PIP ss PIP
8.0 8.7 4.7 1.4 3.0 8.0 5.4 2.1 2.6
80 30
::, 20 15
1 15 35
SS = slabstock, LB = laminated board, FS = field spray, PIP = pour in place. Table 3. Loss of CFC I I from rigid foams, units IO6kg
(I) (2) (3) (4)
McCarthy er al. (1977) scenario Slow loss rate Fast loss rate Mean of (2) and (3)
Cumulative to 1980
Cumulative to 1979
327.5 172.1 511.5
284.8 150.2 450.6
Total relcasc all Release sources 1980 in 1980 42.7 21.9 60.9
4297.6 4142.2 4482.6 4311.9
Production and rehsc
to
the atmosphere of CC&F and CCIrFr
and CFC 12 as solvents. These uses are treated like aerosols with a 6-month release delay (CMA, 1981a, b, 1982a, b). The category also includes sales which have not been attributed to any other use. The maximum reasonable uncertainty can be evaluated by treating ‘other” releases as if they were in the short lifetime refrigeration category. Errors in the release estimates arising from lack of detailed knowledge of the category ‘other’ are unlikely to be si~~~nt in the total ~kulation because this category is a small fraction of the total.
5. RELEASEUNCERTAINTIES The uncertainty in the overall estimate of releases can now be calculated using the above analysis. The significance of the uncertainties in the various release categories depends on what the release estimate is to be used for. For lifetime cakulations based on the global inventory, absolute errors in the release total that matters, T;R,, are im~rtant. For lifetime calculations using trend analysis, it is the un~rtainty in the release trend that matters, i.e. Rt980&9eoR,. The magnitudes of the uncertainties and their estimated impact on the lifetimes calculated by the two methods are given in Table 4. Although the errors cannot be statistically defined as 2u, they appear to approximate 95 “/b confidence limits, i.e. there is less than a 5% chance that the true value lies outside these limits. The
1083
table shows that the significant uncertainties in the release estimates are: For CFC 11, (1) the closed cell foam release scenario (2) the end use pattern for non-participating companies (3) U.S.S.R. production growth since 1975 (4) PRC production (in dete~ining inventory lifetime). For CFC 12, (1) U.S.S.R. production growth since 1975 (2) the end use pattern for non-participating companies (3) production in Eastern Europe excluding the U.S.S.R. (4) the short lifetime refrigeration release scenario (5) PRC production (in determining inventory lifetime). This analysis re-emphasizes the need for production and use of data from producers not participating in the CMA FPP programme, as well as a better understanding of the release from the closed cell foam and short lifetime refrigeration categories. 6. CURRENT WORLD
PRODUCTIONAND RELEASE ESTIMATES
The latest estimates of world production of CFC 11 and CFC 12 are given in Fig. 1 and in Table 5 which
Tat&r 4. Sources of uncertainty and their impact on lifetime calcubtions Uncertainty in release estimate
Participating company production i 0.5 % U.S.S.R.growth since 1975:3 to 21 % PRC production: 1% of world production since 1960 Eastern Europe production: 15% of U.S.S.R. f 15% of U.S.S.R. Non-participating use pattern: all aerosol or all 4-y release delay Long lived refrigeration comprises 8 f 2 % of refrigeration total Fugitive emissions 2.7 &0.4 % Aerosol release delay 6 months f 1 month Short lived refrigeration 4 f 0.5 y Open cell foam. Release delay 2 f 1 month Closed cell foam. Fast and slow limits
Other category treated as short lifetime refrigeration not aerosol CJ;n$a$e
r
I f
ucertainity
Resulting % change inX ISIORI CFC 11 CFC 12
Resulting % change inR 1910 Z 1990 RI CFC 11 CFC 12
*0.5 - 0.4 +0.1
&OS - 1.4 + 0.3
0 - 2.0 +0.6
0 -6.9 +1.8
+0.8
+ 0.8
N
N
N
f 1.1
N
4 1.7
kO.8
*2
N io.4 N N N k4.0
N rto.4 N +0.6 N -
ii
+3
N N N N f0.5 +0.5 N It1 N N + 2.9 -4.8 (Overall - 1 f 4)-
N
N
N
N
+0.2 lt4.2
-0.1 f2.8
-1.7 f4.3
-2.5 k5.6
l‘Uhere the calculated change is substantially lessthan 0.5 %, i.e. negligible, this is marked by N.
1084
P. H. GAMLENet a(. Table 5. Estimates of total world production and release in 1982, units 1O’kg (CMA, 1983) Annual
CFC 11 CFC 12
Cumulative
Production
Released
Production
Released
Unreleased
310.2 443.7
258.8 422.8
5583.5 8196.0
4898.3 7520.2
768.9 880.7
Table 6. Cumulative estimated release up to the end of 1974, units lo6 kg CFC 11
McCarthy ( 1977) Rowland (1975). CMA (1981b) CMA (1982b) This work
CFC 12
Production estimate
Release estimate
% difference in release from this work
3073.7 2639 3068.1 3017.1 3017.1
2587.3 2349 2526.0 2582.5 2597.6
-0.4 -9.6 -2.7 -0.5 -
Production estimate
Release estimate
y0 difference in release from this work
4663.5 3909 4640.8 4698.5 4698.5
3991.8 3521 3949.1 4248.6 4286.2
-6.9 - 17.8 - 7.9 -0.9 -
*Rowland estimate is to 1 Nov. 1974, to which has been added one sixth of the production and refeasefor 1974 from this work to give comparable data.
also includes estimates of releases (CMA, 1983, 1984). The methods of estimation used in this paper are those used in the most recent CMA FPP reports (CMA, 1983, 1984). The production and release estimates for the years up to 1974 (i.e. before U.S.S.R. production was first reported) are given in Table 6. The table shows estimates made using the current methods, those of McCarthy er al., the earlier CMA FPP methods and those of Rowland (1975) For CFC 11, the total release estimate for 1974 from this work barely differs from that of McCarthy et al. (1977) although the sub-totals differ. Differences between CMA (1981b) and CMA (1982b) and this work reflect the inclusion of fugitive emissions in the estimate, firstly at 1.5 % of production in CMA (l982b), and at 2.0% in this work. For CFC 12, the release estimate for 1974 from this paper is about 7% higher than that of McCarthy et ol. (1977). Detailed investigation of this difference (294 x IO6 kg) shows that about 60% arises from the introduction of fugitive emissions and about 40% from the changed treatment of the two refrigeration categories. It is consistent with this analysis to note that the 1974 production total estimated in this paper for CFC 12 is less than 1% different from that of McCarthy er al. (I 977). As emphasized in section 2.2, in the years after 1975 there is an increasingly large difference for CFC 12 world production estimates (and a lesser difference for CFC 11) between CMA (1981b) and CMA (1982b). This can be almost exactly accounted for by the increase in the CMA FPP estimate of U.S.S.R, production growth (from 3 to 18 % growth per year). This change is also ref%-cted in the release estimate.
7. CONCLUSIONS
Updated estimates of world production for CFC I I and CFC 12 presented in this paper differ somewhat from those of McCarthy et al. (1977). The revised release estimates for CFC 12 are some 7 % higher than those estimated by McCarthy et al. (1977). Treatment of fugjtive iosses in manufacture, acceptance of market research data on refrigeration product lifetimes, and re-evaluation of U.S.S.R. production growth have led to larger release estimates, particularly for CFC 12, compared to the previous CMA FPP release estimates (CMA, 1981b) and to McCarthy et al. (1977). From an examination of uncertainties it is concluded that the cumulative release figure for CFC I 1 is uncertain to & 4 y0 (95 7; confidence limits), whereas that for CFC 12 is uncertain to f 2.8 %_The standard deviations of lifetime estimates arising from this source are calculated as reciprocaf lifetime uncerlainties of *0.~5y-ifor~FClland~0.~3y-‘forCFC~2. These may be underesti~ted uncertainties if U.S.S.R. production growth has been overestimated as appears likely (section 2.2). The analysis of uncertainties points out the importance of reported data from the U.S.S.R., Eastern Europe and the People’s Republic of China, as well as highlighting the need for improved understanding of the release of CFC 12 from closed cell foams.
Rcknmvledt7emenzs-We thank our collegues in the Fluorocarbon Program Panel of the Chemical M~ufacture~ Association for their help and advice. Wc are grateful to C. Hales and A. Owens (E.I. du Font de Nemours and Co.) who carried out the release calculations.
Production and release to the atmosphere of CCI,F and CCllFl REFERENCES
BASF (1981) Losses of F-1 I during the production of PUR foams. Distributed by the International Isocyanurate Institute, Feb 1982. Borisenkov E. P. and Kazakov Y. E. (1980) Action of Freons and halocarbons on the ozone layer of the atmosphere and on the climate. Tr. GL. Geofiz Obs. 43& 62-74. Brandreth D. and Ingersoll H. (1980) J. cell. Plastics 16, 54-47. CMA (198la) 1980 world production and sales of fluorrxarbons FC-II and FC-12. Chemical Manufacturers Association, 2501 M Street, NW, Washington, DC 20037. CMA (1981b) World production and release ofchlorofluorocarbons 1I and I2 through 1980. CMA. CMA (198lc) United States production and sales of chlorofluorocarbons FC- I I and FC- I2 from 1976 through 1980. CMA. CMA (l982a) World production and release of chlorofluorocarbons II and 12 through 1?80. An Update. CMA. CMA (1982b) Production, sales and calculated release of CFC II and CFC I2 through 1981. CMA. CMA (1982c) Carbon tetrachloride consumption in production of chlorofluorocarbons FC-I I and FC-12. CMA. CMA (1983) Production, sales and calculated release of CFC II and CFC I2 through 1982. CMA. CMA (I 984) Production, sales and calculated release of CFC I I and CFC I2 through 1983. CMA. Cunnold D. M.. Prinn R. G., Rasmussen R. A., Simmonds P.
1085
G. Alyea F. N., Cardelino C. A.. Crawford A. J., Fraser P. J. and Rosen R. D. (1983) The Atmospheric Lifetime Experiment-3. Liietime methodology and application to three years of CFCI, data. J. geophys. Res. 88,8379-8400. EFffC (1982) CFC production and use. 1981. Report to the Fluorocarbon Commission. European European Technical Committee. EPA (1980) Communication from the US Environmental Protection Agency reported in Little (1980). IMOS (1975) Report of Federal Task Force on Inadvertent Modification of the Stratosphere. Council on Environmental Quality, Federal Council for Science and Technology, Washington DC. Little A. D.: Inc (1980) U.S. emissions of CFC I I from rigid plastic foams. Final report on contract FC-79-275. CMA. McCarthy R. L., Bower F. A. and Jason J. P. (1977) The fluorocarbon-ozone theory--I. Production and release: world production and release of CCI,F and CClrFr (fluorocarbons II and 12) through 1975. Afmospheric Environmenf I I, 49 I-497. implications of regulating Rand (1980) Economic chlorofluorocarbon emissions from non-aerosol applications. Report issued by U.S. Environmental Protection Agency, EPA-560/12-80-001. Rasmussen R. A. (1982) Report from Oregon Graduate Centre on contract FC-82-34.5, CMA. F. s. and Molina M. J. (1975) Rowland Chlorofluoromethancs in the environment, Reu. Geophys. Space Phys. 13, I.
I Vol. 20. No. 6. pp. 1077-1085.
0004-698l/a6 kwmon
1986.
Britain.
53.00+0.00 Joumrlr Ltd.
THE PRODUCTION AND RELEASE TO THE ATMOSPHERE OF CC13F AND CC12Ft (CHLOROFLUOROCARBONS CFC 11 AND CFC 12) P. H. GAMLEN,B. C. LANE and P. M. MIDGLEY ICI Americas Inc., Wilmington, DE 19897, U.S.A. and J. M. STEED E. I. du Pont de Nemours and Company Inc., Corpus Christi, TX, U.S.A. (First receiued 26 Nouember 1984 and in jnul form 30 October 1985) Abstract-In order to understand the present concentration distribution of CCl,F and CC12FI in the atmosphere and their atmospheric lifetimes, accurate data on the global production and release of these materials are needed. This papezrreports improvements in the understanding of certain production and use categories which increase the accuracy of the estimates of these releases. However, lack of recent production data from certain sources prevents the total world production, and hence release, estimates from reflecting similar accuracy. Key word index: Atmosphere, atmospheric abundance, concentration. lifetime, chlorofluorocarbon, production. release.
1.
INTRODUCTION
Accurate global production and release data are vital to an understanding of the present concentration distribution of CCllF (CFC 11) and CCIIFl (CFC 12) in the atmosphere and to the analysis of their atmospheric lifetimes. For several years, the Fluorocarbon Program Panel of the Chemical Manufacturers Association (CMA FPP) has published annual estimates of the production, sales and release to the atmosphere of CFC 11 and CFC 12. This paper reports the resuIts of a study to improve these estimates and to reduce the uncertainties in the published figures. Up to 1980, these figures (CMA, 1981a, b) were based on release scenarios developed by McCarthy and his co-workers (McCarthy et al., 1977) for various defined end use categories. Subsequent improvements in the understanding of certain production and use categories for CFC I 1 and CFC 12 increase the accuracy of the estimates of releases for these categories, but lack of recent production data from other sources seriously limits the accuracy of estimates of global production and release (CMA, 1982a, b. 1983). This paper addresses the following aspects of release estimation: the collection and estimation of production data, the categorization of production into various end uses, and the pattern of release to the atmosphere from these end uses. Finally the significant uncertainties in the release estimates are considered.
2. PRODUCTION ESTIMATES
2.1. Reporting companies Production of CFC I1 and CFC I2 is reported. annually on a confidential basis to an independent accountant, Alexander Grant and Co., by the CFC producing companies who are members of the CMA FPP (see Table 1).Alexander Grant supply CMA FPP with the total production figure for CFC 11 and CFC 12 for these companies. The participating companies include all producers in the U.S.A., Canada, the EEC and Japan. Production in countries such as Australia, Argentina, Brazil, Mexico, South Africa, Spain and Venezuela is reported either directly or through companies which participate in the CMA FPP programme. The reported figures are essentially sales figures, that is production corrected for inventory changes, and are not corrected for any CFC 11 or CFC I2 which is manufactured but lost to the atmosphere during the manufacturing or packing processes at the production site. This particular emission is considered in the release section of this paper. 2.2. Other CFC producers Not all CFC producers are members of the CMA FPP. Production from non-participating companies has been estimated by the CMA FPP from the limited information available as follows.
1078
P. H. GAMLEN
Table 1. Chlorofluorocarbon manufacturers involved in the production survey The following is a listing of the reporting companies including any related subsidiaries and/or joint ventures that reported production and release data throueh 1982: I Akzo Chemie, BV (Holland) 2 Allied Corporation (U.S.) (a) Allied Canada Inc. (Canada) (b) Qu~o~icos, SA (Mexico) 3 Asahi Glass Co. Ltd (Japan) 4 Atochem (France) formerly Chioe Chimie and PCUK [a) Pacific Chemical Industries Pty Ltd (Australia) (b) Ugimica, SP (Spain) (c) Prcduven (Venezuela) 5 Australian Fluorine Chemical Pty Ltd (Australia) 6 Da&in Kogyo Co. Ltd (Japan) 7 E. 1. du Pont de Nemours & Company Inc. (U.S.1 (a) Du Pont de Nemours (N~er~nd} NV (b) Ducilo, SA (Argentina) (c) Du Ponl do Brasil, SA (Brazil) (d) Halocarburos, SA (Mexico) 8 Du Pont Canada, Inc. (Canada) 9 Essex Chemical Corporation (Racon) (U.S.) 10 Hoechst, AG (West Germany) (a) Hocchst Iberica (Spain) (b) Hoechst do Brasil Q&mica e Farmaceutica, SA II Imperia] Chemical Industries PLC (England) (a) African Explosives & Chemical Industries Ltd 12 ISC Chemicals’ Ltd (England) 13 Kaiser Aluminum & Chemical Corwration (U.S.) 14 Kali-Chemie Akliengesekchaft (W&t Germany) (a) KaIi-Chemie Iberia, SA (Spain) 1s Mirsui Ftuor~hern~ats Co. Ltd (Japan) 16 Montefluos SpA (Formerly Montedison SpA) (Italy) 17 Pennwalt Corporation (U.S.) 18 Showa Denko, KK (Japan) 19 SICNG (Greece) 20 Union Carbide Corporation (U.S.r (Union Carbide ceased production in 1977).
India. Two producers exist (Aegis Chemical Industries Ltd and Navin Fluorine Industries) whose production capacity is reasonably well known. Since their production is relatively small, errors in these estimates are unlikely to produce any signifi~nt error in the world production total. Navin Fluorine Industries recently agreed to report their production for 1983 which will be included in the 1984 CMA FPP report. Argentina Two independent producers (Tool Research SA and IRA SA) operated in Argentina during the 197Os,but both companies closed in 1979. Estimates of their relatively small production during the 1970s have been revised and, as in the case of India, errors here do not introduce any significant error in the world production total. People’s
Repub~jc oj China. CFCs are known to he
the People’s Republic of China (PRC) but the production capacity is believed lo be still relatively
produced in
small. For lack of hcttcr information,
the PRC pro-
CMA FPP estimates. U.S.S.R.The only published data for U.S.S.R. production of CFC 11 and CFC 12 are for the years 1968-1975 (Borisenkov and Kazakov, 1980). For the duction
is assumed to he zero
in the
er al
principal product, CFC 12, these data show an average compound growth of 18% per year throughout the period. Until I982, these figures were incorporated into the CMA FPP estimates, together with an assumption of zero production before 1968 and 3 >Aper year growth after 1975 (CMA, 1981b). In reality, it is unlikely that U.S.S.R. production could have commenced in I968 at such significant levels, and it therefore seems more reasonable to assume a gradual build-up in production from 19.50 to 1968. More recent CMA FPP estimates (CMA, 1982a. b, 1983) have assumed that the historic growth of 18 “,i per year continued after 1975. The continued application of this assumption over severaf years is likely to be wrong and contributes an increasingly large uncertainty in the estimate of U.S.S.R. production and hence in the estimates of world production and release. The U.S.S.R. production of CFC 11 and CFC 12 estimated on this basis has grown from 8 % of the total world estimate in 1975 to 22% in 1982, the latest year for which estimates have been publish~ (CMA, 1983). It is believed that the U.S.S.R. production capacity for CFC 11 and CFC 12 in fact totals no more than 70-80 x lo6 kgcompared to the 1982 CMA FPP estimate of production of 123 x 10’ kg. This is a matter of serious concern and the FPP has endeavoured to obtain more reliable data. To date, these have proved unobtainable. Eastern Europe. There are believed to be a number of CFC plants in the countries of Eastern Europe other than the U.S.S.R., specifically in the German Democratic Republic, Czechoslovakia and possibly in Hungary and Poland. No information has been pubfished on the production in these countries, other than an estimate in the IMOS report (1975) of uncertain quality. In the CMA FPP world estimates, the production for Eastern Europeexcluding the U.S.S.R. was set at 15 7; of the U.S.S.R. production for each year. This is also likely to be increasingly in error if the U.S.S.R. figure is in error.
2.3. Uncertainties
in the production
estimates
The uncertainties in the production data from the CMA FPP reporting companies are probabfy not more than _+O.S%, once plant losses have been separately accounted for (see fugitive releases below). The principal sources of uncertainty in the world production estiinate have been arbitrarily set at the values shown below to permit a sensitivity analysis. PRC production: the figure of zero presently used obviously underestimates any true production figure. In the uncertainty analysis in section 5, an upper limit of pr~~tion in the PRC is set at 1 ‘%,of the world figure. U.S.S.R. production since 1975 has been estimated assuming 18 y0 growth per year. The estimated range for uncertainty analysis is 3-21:~ per year. Eastern European production excluding the U.S.S.R.: the present a~umption of IS:4 of the U.S.S.R. production is unsupported by any firm data.
1079
Production and rckase to the atmosphere of &C&F and CClzFFI
For uncertainty analysis, the limits ased were zero production and twice the current estimate. Inclusion of the 18 % per year increase for U.S.S.R. production has become a significant factor in estimating world production of CFC 11 and CFC 12 (see Fig. 1). In the absence of reported data from the U.S.S.R. and other producers, the CMA FPP has reluctantly discontinued its estimates of world production. Starting in 1984, the annual report will on11 include reported data.
3. DEFlNlTlON
OF END USE
CATEGORIES
In order to calculate the overall release rate of CFC 11 and CFC 12, the time delay for release from their varied uses must be estimated. McCarthy et al. (1977) proposed grouping the uses of CFC 11 and CFC 12 into six categories, where the uses within each category had a similar release pattern. This approach has been applied in the CMA FPP estimates (CMA, 1981a, b). The six categories given by McCarthy et al. are: Aerosols Heretically sealed refrigeration (long lifetime, about 12 y) Non-hermetically sealed refrigeration (short lifetime, about 4 y) Closed cell foams Open cell foams Other uses. Each year the participating companies submit to Alexander Grant, along with production numbers, the sales in each category. Alexander Grant compile the
figures and transmit the totals in each use category to CMA FPP. It is important to note that the end uses are not known for the non-reporting companies and, in
release calculations, this estimate-dproduction is assumed to have the same end use split as the participating company data. The reliability of the end use analysis is thought to be accurate for the major markets, i.e. aerosols, refrigeration and foam. This confidence arises from the way company sales data are normally assembled and the separate nature of these three broad areas. Care is needed with the ~tego~tion of sales to refrigemtion equipment manufacturers who use chlorofluorocarbons both as refrigerant (almost entirely CFC 12), and in pour-in-place foam insulation for the refrigerator itself (almost entirely CFC 11). Of less certain reliability is the subdivision within each category. The sub-division of foam into closed cell and open cell types can be checked to some extent by comparison of published CMA FPP data for the U.S.A. only (CMA, 1981~:collected as described above but for U.S.A. producing plants only), and data in the Rand report (Rand, 1980) for the year 1976. Since the Rand report concerns itself only with U.S.A. domestic consumption, whereas the CMA FPP data refer to U.S.A. domestic plus export sales, exact agreement would not be expected. The CMA FPP reported that 55 % of CFC 11 usage in foams went into closed cell foam. This agrees well with the 52 % figure determined by Rand’s market survey of end users. The same agreement is not found for the subdivision of the refrigeration category. The Rand report identifies only domestic refrigerators and freezers as having the 12-y product use lifetime of the hermetically sealed
45-I
5 1960
I 1962
I 1964
c 1966
I,
1968
,
1970
,
19721974
,
1976
(
1976
(
1960
]
,
1982
1984
Fig. 1. Annual production of CFC 11and CFC 12,1%0-1983.1 I-CMA and 12-CMA arc reported production of CMA FPP participating companies for CFC 11and CFC 12,respectively. 1l-world and 12.world arc estimated total production for these compound% Ettimates for world production were discontinued in 1983. The annual production reports arc available from the Chcmicaf Manufacturers Assoc&tion (CMA 1983,1984).
P. H. GAMLENet al.
1080
category. Market analysis by Rand shows these uses consumed 2.7 x lo6 kg of CFC 12 and no CFC 11 in 1976. The CMA FPP report however shows 33 x lo6 kgofCFC 12and3.6 x lo6 kgofCFC 11 inthis category for 1976. A market survey (Ward, 1982, Private Communication) of the U.S.A. refrigerant market confirms the Rand analysis and suggests that the error is in the McCarthy ef al. categorization used in the CMA FPP estimates. One source of error is the definition of he~eti~Ily sealed which, in a strict mechanical sense, would mean uses where there is no rotating shaft seal retaining the refrigerant. Under such a definition, reciprocating compressors would be classed as hermetically sealed, whereas Rand shows that the initial charge is lost in about 4 y, and this use is better classified in the short lifetime category. Since 1982, the definition of long and short lifetime refrigeration categories for the CMA FPP release estimates has been based on market research analysis (CMA, 1982a, b). For CFC 11, ail reported refrigeration sales are placed in the short lifetimecategory. For CFC 12,3.5 7; of the total is placed in the long lifetime category, and the balance in the short lifetime category. However, for CFC 12 in particular, this introduces some uncertainties. It has been noted (CMA, 1982a) that placement of only 3.5”/, of CFC 12 in this category, whilst appropriate for the U.S.A., would not be applicable for the rest of the world. U.S.A. refrigeration is dominated by automobile air conditioning (in 1976, 41 x IO6 kg), whereas in Europe this use is negligible. However, the errors introduced by the 3.5 y; assumption are not considered serious, since the U.S.A. accounted for 607; of the total refrigeration sales by the participating companies in 1976, and 54 % in 1980. A recent survey of Western Europe showed that 22 % of the 22 x lo* kg consumption in refrigeration was in the long lived category (EFCTC, 1982). The two surveys (Ward, 1982, Private Communication; EFCTC, 1982) together cover some 70% of CFC 12 refrigeration sales by the participating companies. Combining their findings suggests that, of the total CFC 12 sold for refrigeration, 8 + 2 % is of the long lived type and this paper adopts this figure. Further uncertainty arises over the assumptions made for the remaining 30 4; of the sales. The principal remainjng uncertainty in the end use categorization is the ~sumption that the use pattern for CFCs produced by CMA FPP companies is the same for the rest of the world. The errors this introduces into the release estimate can be assessed by examining two limiting assumptions. Firstly, that all the non-reporting companies production is used in aerosols with a fast release and secondly, that all this production is released after a 4-y delay (see section 5). To summarize, the subdivision of chlorofluorocarbon production into end use categories is described by the following equation: p, = R(P), + S(A), + S(LRB -t-S(SR), + S(OC), + S(X), + S(O), + @A),
where P = production, R = release and S = sales and the end use fractions are given by F = fugitive emission A = aerosol LR = long lived refrigeration SR = short lived refrigeration UC = open cell foam CC = ciosed cell foam 5 = other, see section 4.7 SA = stock adjustments t = year. For refrigeration and where
where c @A), ‘-t 0 t
S(LR), = O.OSS(TR), for CFC 12 S(SR), = S(TR), for CFC 1I
TR = total refrigeration.
4. RELEASE SCENARIOS 4.1.
Fug&e
emissions
Not all the CFC 11 and CFC 12 manufactured is sold. Some escapes from plant vents, and some is lost during the packing operation. These losses are immediate, with no delay between production and release. In recent release calculations (CMA, 1982a, b), 2 % of the total product has been estimated to be lost in this way and a higher proportion of this will be the more volatile CFC 12. These fugitive emissions have been incorporated into release estimates by adding 2.5 “/, of CFC 12 production, and 1.5 y0 of CFC 11 production into the prompt release category. More recently, a carbon mass balance has been carried out on about 60% of the production from reporting companies to determine these fugitive losses more precisely (CMA, 1982~).This survey showed that the percentage ofCC1, taken into the manufacturing plants that does not appear in the CFC 11 and CFC 12 sold or stocked, or as known byproducts such as CFC 13, averaged 2.7 + 0.6% for 1969-1979. Applying an assumption that 66 % is lost as CFC 12 and 33 % as CFC 11 gave an estimate of fugitive emissions of 3.3 % of CFC 12 production and 2.0% of CFC 11 production (CMA, 1983). Hence R(F), = 0.02 f, for CFC I 1 = 0.033 P, for CFC 12. (The un~rtainty in the 2.7 % figure is best regarded as the standard error of the mean, i.e. for 1969-1979 where e = f0.6 for an individual annual determination, the standard error in the mean is +-O&J1 I = * 0.2.) 4.2. Aerosols McCarthy et al. (1977) calculated that release from aerosols, on average, took place 6 months after sale, so that only half of aerosol sales were released in the year of sale, and half the following year. R(A), = 0.5 S(A), +0.5 S(A),,_ II. The &month dehy was based on U.S. usage in f 977; at
Production and rckasc to the atmosphere of CC&F and CCltFt that time the major aerosol market. A survey in Italy, Ciermany, France and the U.K., now the major producers of CFC-propelled aerosols, supports this figure (Mills, 1982, Private Communication). The data showed a release delay of approximately 24 weeks. These data suggest that the uncertainty in the &month figure is not more than 1 month. 4.3. Long-lived refrigeration Analysis by McfZarthy et at. (1977) for domestic refrigerators and freezers indicated an average lifetime of 12 y (Q = f 4 y), with a 2 % loss to the atmosphe~ during filling. The Rand report (1980) broadly sup ports this scenario, stating that the manufacturing losses include a 3 % loss on filling and testing. Rand also includes a further 5 y0 loss from system rework. The 12 f4 y lifetime assumed by McCarthy et ol. differs slightly from the Rand estimate of 1.5 % failure per year plus a 17-20 y appliance lifetime. However the differences are not significant sources of error in the overall release estimate, because the percentage of CFC 12 sales in this application is small. Consequently the McCarthy et al. analysis is retained in the CMA FPP estimates. 4.4. S~orr-lied refiberation
use
McCarthy et al. (1977) proposed a 4-y life for this category (a = f 2 y). Most of this use is in industrial refrigerators. This does not imply that the refrigerator life is 4 y but that the refrigerant charge life is 4 f 2 y and the refrigerator is recharged several times during its lifetime. The detailed data in the Rand report (1980) on original equipment manufacturer use and service use for various refrigeration applications can be used to test the validity of the McCarthy scenario. All the sign~~nt uses identified by Rand in this~tego~ have refrigerant lives of 3-5 y and thus substantially confirm the McCarthy scenario. 4.5. Open cell foam A 6-month delay similar to that for aerosols was used by CMA FPP to calculate the release from open cell foam (CMA. 198lb). More recent analysis, however, suggests that CFC 11is released within a few days or weeks after it is used in making the foam. A 2-month release delay is now considered to be a better estimate (CMA, 1982a, b). Thus R(OC), =0.83S(~+O.l7S(~_*. 4.6. Closed cell &am The Rand report (1980) subdivides the closed ceil foam category into rigid polyurethane and isocyanurate foams (CFC 11) and non- urethane foams, polystyrene and some extruded polyoiefins (mainly CFC 12 when the blowing agent is a chlorofluorocarbon). A breakdown for this category follows. 4.61. CFC 12. Most oftheuseofCFC 12forclosed cell foam is in polyolefin foam with a very thin cross section. McCarthy et a!. (1977) quoted data showing
1081
that the CFC is lost from the product to the atmosphere within 2 y, 75 % being lost within 1 y. In this paper, half is considered to be lost in the year of manufacture, and half in the following year. Hence for CFC 12, R(E),
= 0.5 S(CC), +0.5 S(CC),,_ ,,.
The Rand report (1980) states that for non-urethane foams, such as polystyrene sheet, 45-79 % of the CFC 12 is released during manufacture and the rest during the first year and that ~lyoiefin foams are also prompt emitters. Only for polystyrene board does the loss rate equate to that of rigid urethane foams (see 4.6.2). However, in 1976, polystyrene board constituted only a small fraction of the total U.S.A. CFC 12 use in the closed cell foam category (about 20%: Rand, 1980). Hence, provided that the polystyrene board fraction is as small in the rest of the world, the McCarthy ef al. algorithm appears adequate. 4.6.2. CFC 11. The release of CFC 11 from closed cell foam (principally rigid polyurethane foam) is the least well-defined of ail the cateogories. The three principal factors which determine the actual release are: production loss, diffusion loss during product use, and losses on disposal. The current CMA FPP estimate uses the McCarthy et nl. (1977) analysis of a production loss of lo%, followed by a loss of 4.5 % per year for 20 y, representing a combination of product lifetime and diffusional loss. A production loss of IO:,; has been substantiated by market research surveys by Rand (1980) and A. D. Little Inc. (Little, 1980). although a BASF report (BASF, 1981) suggests a 5 % loss. The subsequent loss rate after manufacture is more contentious. An earlier assumption that the rise in thermal conductivity of foams over time was necessarily associated with WC loss has been questioned by B~ndreth and fngresoll (1980). They showed that this change was principally associated with air ingress, which raised the pressure inside the microcells to one atmosphere from the initial 0.5 atmosphere. Under controlled laboratory conditions, diffusion of CFC 11 from polyurethane foams in an accelerated test is very slow, indicating a lifetime of the order of 100~. On the other hand, some commercial glass filled poiyisocyanurate foams lose CFC 11 quite rapidly, indicating a lifetime of around 10 y (Rasmussen, 1982). Analysis is further complicated because the products into which the foam is incorporated have use lifetimes ranging from 1 to 80 y. Disposal practices for these products determine whether the CFC continues to be lost slowly, is released on disposal (as assumed by McCarthy et al.), or is destroyed on disposal by incineration. The A. D. Little report (1980) studied rigid urethane foam in the U.S.A. It did not directly address the question of the release rate of CFC 11 in normal use since this release rate was, and still is, poorly quantified. However, it addressed the other parameters involved, such as release during manufacture, normal use lifetime prior to disposal, disposal practices etc. A.
P. H. GAMLEN et al. D. Little’s findings are summarized in Tabld 2. A. D. Little found that on average, 11 % of CFC 11 was emitted during manufacture, and also that disposal practices were 95% burial and 5 % incineration. Emissions at, and subsequent to, burial are complex. One draft analysis (EPA, 1980) assumed that half of the remaining CFC It was released on disposal, and half continued to dfluse slowly. For the construction categories, demolition practices would suggest that all the remaining CFC I 1 wilt be released on disposaf. For transport uses, a similar assumption seems reasonable. Household appliances are fargeiy buried with some crushing, and refease of only 25 % at disposal seems reasonable. Weighting these assumptions by the percentage of their market share allows an average release rate on disposal by burial to be calculated. For disposal by incineration, the amount of CFC 11 released unchanged must be small. Since the proportion of foam disposed of in this manner is also small, release of CFC following incineration is set at zero. To summarize: I 15; Initial release Fate on disposal 5 %---no release (incineration) of remaining CFC 11: 75 y<---immediate release 20%--continues at normal release rate
The A. D. Little lifetime data show a reasonably Gaussian distribution with an in-use lifetime of 26 y (a= *13y). The range of uncertainty in the present estimate of the rate of CFC loss during the product lifetime can be evaluated estimating the fastest and slowest likely relase rates. A reasonable, fast loss rate assumes that 10% of CFC 11 is lost during manufacture and the remainder is lost over 10 y. The stow rate assumes a 10&y diffusion half life, in the form of i 1 y/,initial foss, followed by 1% per year diffusion losses but with disposal rate and subsequent emissions following the A.D. Little (1980) data. The releases in this category for these three conditions are given in Table 3. A best estimate of release is perhaps the average of the fast and slow loss rates. This figure is very close to that calculated using the McCarthy et al. scenario, which therefore continues to be used for the CMA FPP calculations. The slow and fast release scenarios are used in section 5 to estimate the associated uncertainties. 4.7. Other This category currently comprises about 7”,; of production. The major uses identified are those of CFC 12 in steriiant gas mixtures and the use of CFC 1I
Table 2. Rigid urethane foam use in the U.S.A. (Little, 1980) CFC 11 eonttnt “/,
Foam
Use lifetime
Use
type
(Y)
Commercial construction
39.1
ss 4.4 LB 17.8
35
Residential construction
2.4
Industriaf construction
12.9
Household refrigeration Household freezers Commercial refrigeration Transport
8.0 8.7 4.1 12.4
Packaging Marine floatation
5.4 4.7
Polystyrene
2.1
FS 13.6 PIP 3.3 ss 0.5 LB 1.9 ss 0.7 FS 10.8 PIP 1.4 PIP PIP ss FS PIP PIP ss PIP
8.0 8.7 4.7 1.4 3.0 8.0 5.4 2.1 2.6
80 30
::, 20 15
1 15 35
SS = slabstock, LB = laminated board, FS = field spray, PIP = pour in place. Table 3. Loss of CFC I I from rigid foams, units IO6kg
(I) (2) (3) (4)
McCarthy er al. (1977) scenario Slow loss rate Fast loss rate Mean of (2) and (3)
Cumulative to 1980
Cumulative to 1979
327.5 172.1 511.5
284.8 150.2 450.6
Total relcasc all Release sources 1980 in 1980 42.7 21.9 60.9
4297.6 4142.2 4482.6 4311.9
Production and rehsc
to
the atmosphere of CC&F and CCIrFr
and CFC 12 as solvents. These uses are treated like aerosols with a 6-month release delay (CMA, 1981a, b, 1982a, b). The category also includes sales which have not been attributed to any other use. The maximum reasonable uncertainty can be evaluated by treating ‘other” releases as if they were in the short lifetime refrigeration category. Errors in the release estimates arising from lack of detailed knowledge of the category ‘other’ are unlikely to be si~~~nt in the total ~kulation because this category is a small fraction of the total.
5. RELEASEUNCERTAINTIES The uncertainty in the overall estimate of releases can now be calculated using the above analysis. The significance of the uncertainties in the various release categories depends on what the release estimate is to be used for. For lifetime cakulations based on the global inventory, absolute errors in the release total that matters, T;R,, are im~rtant. For lifetime calculations using trend analysis, it is the un~rtainty in the release trend that matters, i.e. Rt980&9eoR,. The magnitudes of the uncertainties and their estimated impact on the lifetimes calculated by the two methods are given in Table 4. Although the errors cannot be statistically defined as 2u, they appear to approximate 95 “/b confidence limits, i.e. there is less than a 5% chance that the true value lies outside these limits. The
1083
table shows that the significant uncertainties in the release estimates are: For CFC 11, (1) the closed cell foam release scenario (2) the end use pattern for non-participating companies (3) U.S.S.R. production growth since 1975 (4) PRC production (in dete~ining inventory lifetime). For CFC 12, (1) U.S.S.R. production growth since 1975 (2) the end use pattern for non-participating companies (3) production in Eastern Europe excluding the U.S.S.R. (4) the short lifetime refrigeration release scenario (5) PRC production (in determining inventory lifetime). This analysis re-emphasizes the need for production and use of data from producers not participating in the CMA FPP programme, as well as a better understanding of the release from the closed cell foam and short lifetime refrigeration categories. 6. CURRENT WORLD
PRODUCTIONAND RELEASE ESTIMATES
The latest estimates of world production of CFC 11 and CFC 12 are given in Fig. 1 and in Table 5 which
Tat&r 4. Sources of uncertainty and their impact on lifetime calcubtions Uncertainty in release estimate
Participating company production i 0.5 % U.S.S.R.growth since 1975:3 to 21 % PRC production: 1% of world production since 1960 Eastern Europe production: 15% of U.S.S.R. f 15% of U.S.S.R. Non-participating use pattern: all aerosol or all 4-y release delay Long lived refrigeration comprises 8 f 2 % of refrigeration total Fugitive emissions 2.7 &0.4 % Aerosol release delay 6 months f 1 month Short lived refrigeration 4 f 0.5 y Open cell foam. Release delay 2 f 1 month Closed cell foam. Fast and slow limits
Other category treated as short lifetime refrigeration not aerosol CJ;n$a$e
r
I f
ucertainity
Resulting % change inX ISIORI CFC 11 CFC 12
Resulting % change inR 1910 Z 1990 RI CFC 11 CFC 12
*0.5 - 0.4 +0.1
&OS - 1.4 + 0.3
0 - 2.0 +0.6
0 -6.9 +1.8
+0.8
+ 0.8
N
N
N
f 1.1
N
4 1.7
kO.8
*2
N io.4 N N N k4.0
N rto.4 N +0.6 N -
ii
+3
N N N N f0.5 +0.5 N It1 N N + 2.9 -4.8 (Overall - 1 f 4)-
N
N
N
N
+0.2 lt4.2
-0.1 f2.8
-1.7 f4.3
-2.5 k5.6
l‘Uhere the calculated change is substantially lessthan 0.5 %, i.e. negligible, this is marked by N.
1084
P. H. GAMLENet a(. Table 5. Estimates of total world production and release in 1982, units 1O’kg (CMA, 1983) Annual
CFC 11 CFC 12
Cumulative
Production
Released
Production
Released
Unreleased
310.2 443.7
258.8 422.8
5583.5 8196.0
4898.3 7520.2
768.9 880.7
Table 6. Cumulative estimated release up to the end of 1974, units lo6 kg CFC 11
McCarthy ( 1977) Rowland (1975). CMA (1981b) CMA (1982b) This work
CFC 12
Production estimate
Release estimate
% difference in release from this work
3073.7 2639 3068.1 3017.1 3017.1
2587.3 2349 2526.0 2582.5 2597.6
-0.4 -9.6 -2.7 -0.5 -
Production estimate
Release estimate
y0 difference in release from this work
4663.5 3909 4640.8 4698.5 4698.5
3991.8 3521 3949.1 4248.6 4286.2
-6.9 - 17.8 - 7.9 -0.9 -
*Rowland estimate is to 1 Nov. 1974, to which has been added one sixth of the production and refeasefor 1974 from this work to give comparable data.
also includes estimates of releases (CMA, 1983, 1984). The methods of estimation used in this paper are those used in the most recent CMA FPP reports (CMA, 1983, 1984). The production and release estimates for the years up to 1974 (i.e. before U.S.S.R. production was first reported) are given in Table 6. The table shows estimates made using the current methods, those of McCarthy er al., the earlier CMA FPP methods and those of Rowland (1975) For CFC 11, the total release estimate for 1974 from this work barely differs from that of McCarthy et al. (1977) although the sub-totals differ. Differences between CMA (1981b) and CMA (1982b) and this work reflect the inclusion of fugitive emissions in the estimate, firstly at 1.5 % of production in CMA (l982b), and at 2.0% in this work. For CFC 12, the release estimate for 1974 from this paper is about 7% higher than that of McCarthy et ol. (1977). Detailed investigation of this difference (294 x IO6 kg) shows that about 60% arises from the introduction of fugitive emissions and about 40% from the changed treatment of the two refrigeration categories. It is consistent with this analysis to note that the 1974 production total estimated in this paper for CFC 12 is less than 1% different from that of McCarthy er al. (I 977). As emphasized in section 2.2, in the years after 1975 there is an increasingly large difference for CFC 12 world production estimates (and a lesser difference for CFC 11) between CMA (1981b) and CMA (1982b). This can be almost exactly accounted for by the increase in the CMA FPP estimate of U.S.S.R, production growth (from 3 to 18 % growth per year). This change is also ref%-cted in the release estimate.
7. CONCLUSIONS
Updated estimates of world production for CFC I I and CFC 12 presented in this paper differ somewhat from those of McCarthy et al. (1977). The revised release estimates for CFC 12 are some 7 % higher than those estimated by McCarthy et al. (1977). Treatment of fugjtive iosses in manufacture, acceptance of market research data on refrigeration product lifetimes, and re-evaluation of U.S.S.R. production growth have led to larger release estimates, particularly for CFC 12, compared to the previous CMA FPP release estimates (CMA, 1981b) and to McCarthy et al. (1977). From an examination of uncertainties it is concluded that the cumulative release figure for CFC I 1 is uncertain to & 4 y0 (95 7; confidence limits), whereas that for CFC 12 is uncertain to f 2.8 %_The standard deviations of lifetime estimates arising from this source are calculated as reciprocaf lifetime uncerlainties of *0.~5y-ifor~FClland~0.~3y-‘forCFC~2. These may be underesti~ted uncertainties if U.S.S.R. production growth has been overestimated as appears likely (section 2.2). The analysis of uncertainties points out the importance of reported data from the U.S.S.R., Eastern Europe and the People’s Republic of China, as well as highlighting the need for improved understanding of the release of CFC 12 from closed cell foams.
Rcknmvledt7emenzs-We thank our collegues in the Fluorocarbon Program Panel of the Chemical M~ufacture~ Association for their help and advice. Wc are grateful to C. Hales and A. Owens (E.I. du Font de Nemours and Co.) who carried out the release calculations.
Production and release to the atmosphere of CCI,F and CCllFl REFERENCES
BASF (1981) Losses of F-1 I during the production of PUR foams. Distributed by the International Isocyanurate Institute, Feb 1982. Borisenkov E. P. and Kazakov Y. E. (1980) Action of Freons and halocarbons on the ozone layer of the atmosphere and on the climate. Tr. GL. Geofiz Obs. 43& 62-74. Brandreth D. and Ingersoll H. (1980) J. cell. Plastics 16, 54-47. CMA (198la) 1980 world production and sales of fluorrxarbons FC-II and FC-12. Chemical Manufacturers Association, 2501 M Street, NW, Washington, DC 20037. CMA (1981b) World production and release ofchlorofluorocarbons 1I and I2 through 1980. CMA. CMA (198lc) United States production and sales of chlorofluorocarbons FC- I I and FC- I2 from 1976 through 1980. CMA. CMA (l982a) World production and release of chlorofluorocarbons II and 12 through 1?80. An Update. CMA. CMA (1982b) Production, sales and calculated release of CFC II and CFC I2 through 1981. CMA. CMA (1982c) Carbon tetrachloride consumption in production of chlorofluorocarbons FC-I I and FC-12. CMA. CMA (1983) Production, sales and calculated release of CFC II and CFC I2 through 1982. CMA. CMA (I 984) Production, sales and calculated release of CFC I I and CFC I2 through 1983. CMA. Cunnold D. M.. Prinn R. G., Rasmussen R. A., Simmonds P.
1085
G. Alyea F. N., Cardelino C. A.. Crawford A. J., Fraser P. J. and Rosen R. D. (1983) The Atmospheric Lifetime Experiment-3. Liietime methodology and application to three years of CFCI, data. J. geophys. Res. 88,8379-8400. EFffC (1982) CFC production and use. 1981. Report to the Fluorocarbon Commission. European European Technical Committee. EPA (1980) Communication from the US Environmental Protection Agency reported in Little (1980). IMOS (1975) Report of Federal Task Force on Inadvertent Modification of the Stratosphere. Council on Environmental Quality, Federal Council for Science and Technology, Washington DC. Little A. D.: Inc (1980) U.S. emissions of CFC I I from rigid plastic foams. Final report on contract FC-79-275. CMA. McCarthy R. L., Bower F. A. and Jason J. P. (1977) The fluorocarbon-ozone theory--I. Production and release: world production and release of CCI,F and CClrFr (fluorocarbons II and 12) through 1975. Afmospheric Environmenf I I, 49 I-497. implications of regulating Rand (1980) Economic chlorofluorocarbon emissions from non-aerosol applications. Report issued by U.S. Environmental Protection Agency, EPA-560/12-80-001. Rasmussen R. A. (1982) Report from Oregon Graduate Centre on contract FC-82-34.5, CMA. F. s. and Molina M. J. (1975) Rowland Chlorofluoromethancs in the environment, Reu. Geophys. Space Phys. 13, I.