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First estimates of global flaring of natural gas
Atmospheric
Environment
Vol. 8. pp. 681-686.
Pergamon
Press 1974. Printed in Great Britain
FIRST ESTIMATES OF GLOBAL FLARING OF NATURAL GAS RALPH Air Resources Laboratories,
M. ROTTY*
National Oceanic and Atmospheric Administration, Laboratories, Silver Spring, Maryland 20910, U.S.A.
Environmental
Research
(First received 1.5October 1973)
Abstract-Appreciable amounts of the world’s energy supply are lost through the flaring of gas, and environmental monitoring requires that quantitative information be avilable. From data reported or estimated for 1968-1971 a regression line was fitted to correlate world-wide gas Baring to crude petroleum production and thus arrive at estimates on flared gas for each year since 1935.
In 1971 the total energy produced and used by all the nations of the world was 198 x 10” Btu, World Energy Supplies (1972). Not included in this total is the potential supply of energy from the natural gas which was flared. This flared gas (largely in the producing oil fields) is estimated to have totalled 6 trillion ft3 in 19’71,and represents 6 x 10” Btu of energy which could be a 3 per cent supplement to the current energy supply. The idea of conserving global energy supplies and the economic potential for utilizing at least a portion of this wasted source strongly suggest an effort be made to assign quantitative values to the global flaring of natural gas. Also, for scientific purposes in monitoring the env~onmen~ it is necessary to know not only how much gas is being flared but also how much was flared during a given period in the past. For example, in 1971 the flaring of natural gas contributed about 2 per cent of the CO1 produced by the combustion of fossil fuels and released to the global atmosphere (Rotty, 1973). Keeling has indicated a need for an estimate of the amount of natural gas flared in past years in attempts to determine the fraction of CO* remaining airborne (Keeling, 1973). In the modeling studies of CO2 exchanges between the atmosphere, the oceans, and the biosphere, it is essential to know the total anthropogenic production since the time man began producing COz to establish the proper exchange coefficients. The data published in the UN. Statistical Yearbook (1973) and until recently in the Minerals Yearbook (1973) of the US. Bureau of Mines for natural gas as a fuel were for “marketed production” and specifically excluded gas flared or vented and that used in repressuring the wells. To determine the total burne& the gas flared must be added to the published (marketed) production. Until now no tabulation of gas flared on a global basis has existed, although the Minerals Yearbook (1973) has given values for flared gas in the U.S. for each year since 1935. In the process of constructing these data where none has existed before, several interesting observations were made. However, so that the observations can be suitably interpreted it is necessary to describe the procedures by which the data were determined. * On leave from Old Dominion University. A.E.S/7-.,
681
682
RALPH M. ROTTY
The natural gas section of the 1970 Minerals Yearbook (1970) for the first time gives a world summary which tabulates both “gross production” and “marketed production” and that yearbook also includes data for 1968 and 1969. The gross production comprises marketed production plus the gas vented, flared, reinjected for repressuring and used to drive turbines (without being burned). In most cases the flaring and reinjection account for the difference and the gas vented and that used to drive turbines can be neglected. Thus, for each year since 1968, data for natural gas flared would be available if one could separate the amount used for repressuring from the difference of “gross production” and “marketed production”. The Office ofTechnical Data Services of the U.S. Bureau of Mines receives a completed questionnaire from most of the countries of the world giving data on mineral production including natural gas. Information is requested on amounts produced, amounts flared, and amounts used in repressuring. Individual questionnaires for 1970 and 1971 were made available for this investigation and in about half the cases reasonable numbers were found for flaring. In the other cases assistance of Bureau of Mines personnel was called upon to estimate the fraction flared vs that used in repressuring. The results are tabulated in Table 1. The years 1968 and 1969 presented a different problem in that the questionnaires from the individual countries were not available. With the assistance of Bureau of Mines personnel, including the regional petroleum experts for several geographical areas estimates on the division between the gas flared and that used for repressuring were made for 1968 and 1969. Thus, information similar to that in Table 1 for the two previous years was prepared but because of the great reliance on estimated data, the confidence level in the values for individual countries is reduced. The total world wide figure is probably accurate to within a few percent, since errors for individual countries should be at least partially compensating. The problem then remaining was that of projecting the data backwards in time to obtain estimates on gas flared prior to 1968. Bureau of Mines personnel suggested that gas flared Table I. Gas flared--1970.
Abu Dhabi Algeria Angola Argentina Austria Barbados Bolivia Brazil Brunei Canada Columbia Congo (Brazzaville) Czechoslovakia Dubai Ecuador France Gabon Germany, W. Hungary India
1970
1971
6783 5664 772 1649
9226 5664 889 1624 71
0
388 1038 3361 2252 567 2 222 538 274 2553 32 194 168 748
655 942 3172 2441 652 2 148 736 258 2589 270 215 766
1971: (in millions
of cm3) 1970
Indonesia Iran Iraq Japan Kuwait Libya Mexico Netherlands New Zealand Nigeria Oman Peru Qatar Saudi Arabia Trinidad U.S.S.R. UAR (Egypt) U.S. Venezuela World Total
1812 28970 4879 18 11477 12378 4915 267 7983 566 1438 2492 13433 1001 12942 963 13862 18446 165348
1971 2172 28497 5360 22 11801 9855 4088 96 58 12477 566 1253 3198 20917 929 12806 793 8510 16168 169887
683
Global flaring of natural gas
160 000 -
1969/
140 000 -
Non U.S. world 1968-1971
120 000 -
100 000
-
“E
eoooo-
h *
60000-
k E ::
u
40000-
/
20 000
Slope = I I I
4;3.* 47 43’ 45 1938-42
U.S. only 1935-1947
3 .;“6’
I/ V 0
500
1000
Crude
petroleum
1500
IO6 metric
2000
tons
Fig. 1. Correlation of gas flared with crude petroleum production.
should correlate best with crude petroleum production, at least in the first approximation. Most of the gas produced in gas fields is collected and marketed because the collection equipment and procedures are available. In oil fields the collection of the gas associated with the oil requires an investment which oil producers are frequently not prepared to make. For the U.S., published data exist for both natural gas flared and crude petroleum produced for the years from 1935 and to the present (Minerals Yearbook, 1973). Until near the end of World War II, the U.S. gas flared and the U.S. crude petroleum produced both increased, a situation somewhat analagous to the remainder of the world today. During the 1940’s there was a change in practice in the U.S. toward less flaring and while the national petroleum production increased, the gas flared did not follow in proportion. Since 1947 the amount of gas flared in the U.S. has trended generally downward with a few yearly increases while during this period petroleum production has risen steadily. The gas flared vs the crude petroleum production is plotted in Fig. 1 and up to 1947 a regression line with a slope of 111 provides a reasonable fit to the data as shown in the lower left of the figure. Since there was no reliable tabulation of gas flared for the rest of the world, it was necessary to estimate amounts from the data for crude petroleum. Figure 2 shows the crude petroleum production for the total world the U.S., and the world minus the U.S. production. In addition to being helpful in estimating gas flared in previous years, this figure shows several interesting things: (a) The world-wide crude petroleum production has grown smoothly along an exponential curve for the period of the figure (i.e. since 1930) while the U.S. crude petroleum production shows a steady linear growth.
684
RALPH M.ROTTY Crude
petroleum
production -70
-60 zzoo-
f % U.S.
= 20000 ', 1600: i
-50 0 ," -40 ';;
16001400-
vi -30 j
6 1200P .o IOOO-
.-
a*.. World..’
:
*.
8 ‘._
600-
-20 +on-U.S.’ World
:’
6001
.:
400
. . . ,....
‘.’
.‘,*J
_O
‘U.S.
0” ,,:.“‘,,*‘~‘.”
..I.~
- 10
t 2ooi;;In::::::::::::...
10930 , 34 I 3I 6 42 I 48 I 50 b 54 I 56 I 62 I 66 88 70 74 I,
'
Year
Fig. 2. Crude petroleum
production
(b) The U.S. produced 60 per cent or more of the worlds crude petroleum until 1950 but this percentage has dropped steadily since then and wasless than 20 per cent in 1971. (c) The non-U.S. production curve is smooth with an exponential growth rate of 9.1% y- ‘. The smoothness and rapidity of growth are indicators that the amounts of natural gas flared should be growing in proportion. The correlation of the natural gas flared in the non-U.S. world with the petroleum produced in the non-U.S. world for the years 1968, 1969, 1970 and 1971 for which data or estimates of gas flared were prepared is shown in the upper right portion of Fig. 1. Weighing the points for 1970 and 1971 (for which confidence is higher) by a factor 1.5 in comparison with the points for 1968 and 1969 gave a slope of 86 for the regression line through the origin best fitting the data. The natural gas flared in the non-U.S. portion of the world could then be estimated for prior years by multiplying the crude petroleum produced by 86 in order to get gas flared in millions of cubic meters. It should be emphasized that this line is suitable for estimation only for years prior to 1971 since the practice in non-U.S. fields shows evidence of changing as was the case in the U.S. in the 1940’s. Table 2 is a tabulation of the estimated amounts of natural gas which have been flared on a global basis since 1935. The first column is the amount flared in the non-U.S. part of the world and is determined from the crude petroleum production for the non-U.S. world multiplied by the slope of the non-U.S. regression line in Fig. 1. The second column is the U.S. gas flared obtained from Minerals Yearbook data (not from estimates based on the U.S. regression line of Fig. 1). The third column for the total world is, of course, the sum of the other two, and is shown graphically in Fig. 3. The sharp exponential rise in the recent past results statistically from the amounts reasonably well known to have been flared in 1970 and 1971 and indicates that if world crude petroleum production continues to grow along the type of curve shown in Fig. 2, then even larger amounts of gas must
Global flaring of natural gas Table 2. Estimated gas flared-106
685 m3
Year
Non-U.S. World gas flared
U.S. gas Flared
Total
Year
Non-U.S. World gas flared
U.S. gas Flared
Total
1935 1936 1937 1938 1939 1940 1941 1942 1943 1944 1945 1946 1947 1948 1949 1950 1951 1952 1953
7628 8022 8812 8975 9524 9232 9489 8194 8709 10605 10210 11729 13514 16388 18112 21210 23595 25989 28305
13871 11116 14902 18383 19181 18578 17847 17751 25547 28612 25380 31209 30243 22945 24182 22684 22463 24032 22948
21499 19138 23714 27357 28705 27810 27337 25945 34256 39217 35591 42938 43756 39333 42295 43894 46058 50021 51253
1954 1955 1956 1957 1958 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971
31326 36422 40661 44281 48228 52793 59288 64487 71952 78679 87241 95195 104256 112158 124805 137314 152724 164633
20492 21908 20589 22914 17938 16171 15941 14826 12053 10858 9629 9037 10640 13874 14627 14891 13863 8510
51818 58330 61249 67195 66166 68963 75229 79313 84005 89536 96870 104232 114895 126032 139432 152205 166587 173143
be disposed of, either by collection, processing and sale, or by flaring or other onsite disposal. It is evident that where locations make the collection economical, the practice will very rapidly change away from flaring and larger petroleum production does not indicate proportional increases in gas flaring.
i
100 -
“0 -
d
e
r, ;
..
a
..I,e,
:.
50..
‘1966-71 Observed VOItmS
.:
.
. . .. 11 34
$30
.
. . ..
36 I
.
42I
46I
50I
54 I
56 I
62 Ii
66
70 1
74 I
Year
Fig. 3. Estimated global flaring of natural gas.
686
RALPH M. ROTTY
The data in Table 2 and in Fig. 3 should be regarded as first estimates only. The confidence in these data decreases as one moves toward earlier years. It is certain however that the amounts of gas flared decrease significantly in the earlier years and a 10 per cent error in the 1935 amount is about the same magnitude as a 1 per cent error in the amount for 1970. The procedure suggested here is a method of estimating the gas flared globally for past years only. It is not recommended for projections into the future, since shortages of fuels will cause changes in procedures throughout the world. Acknowledgements-The author acknowledges with gratitude the assistance of the National Research Council through the award ofa NRC Senior Resident Research Associateship in the Air Resources Laboratories, NOAA. It was during the tenure on this appointment that the need existed for consistent data on flaring of natural gas. Dr. C. D. Keeling encouraged this study after a preliminary estimate was made for recent years in connection with atmospheric COz. Charles Kimbell and David Carleton of the Bureau of Mines were very helpful in obtaining data and estimates for flaring in many individual countries. Dr. Lester Machta has been Research Advisor for the Research Associateship, and the author is indebted for his advice and encouragement.
REFERENCES Keeling C. C. (1973) Private communication. Minerals Yearbook, (annually) Bureau of Mines, United States Department of the Interior, U.S. Government Printing Office, Washington, D.C. Rotty R. M. (1973) Commentary on and extension of calculative procedures for CO1 production. Te/lu.s 25 (5) 50885 17. Statistica/ Yearbook, (annually) Department of Economic and Social Atfairs, United Nations, New York. World Energy Supplies, United Nations Statistical Papers, Series J. No. 16. 1972,(In press) Department of Economic and Social Affairs, United Nations, New York.
Environment
Vol. 8. pp. 681-686.
Pergamon
Press 1974. Printed in Great Britain
FIRST ESTIMATES OF GLOBAL FLARING OF NATURAL GAS RALPH Air Resources Laboratories,
M. ROTTY*
National Oceanic and Atmospheric Administration, Laboratories, Silver Spring, Maryland 20910, U.S.A.
Environmental
Research
(First received 1.5October 1973)
Abstract-Appreciable amounts of the world’s energy supply are lost through the flaring of gas, and environmental monitoring requires that quantitative information be avilable. From data reported or estimated for 1968-1971 a regression line was fitted to correlate world-wide gas Baring to crude petroleum production and thus arrive at estimates on flared gas for each year since 1935.
In 1971 the total energy produced and used by all the nations of the world was 198 x 10” Btu, World Energy Supplies (1972). Not included in this total is the potential supply of energy from the natural gas which was flared. This flared gas (largely in the producing oil fields) is estimated to have totalled 6 trillion ft3 in 19’71,and represents 6 x 10” Btu of energy which could be a 3 per cent supplement to the current energy supply. The idea of conserving global energy supplies and the economic potential for utilizing at least a portion of this wasted source strongly suggest an effort be made to assign quantitative values to the global flaring of natural gas. Also, for scientific purposes in monitoring the env~onmen~ it is necessary to know not only how much gas is being flared but also how much was flared during a given period in the past. For example, in 1971 the flaring of natural gas contributed about 2 per cent of the CO1 produced by the combustion of fossil fuels and released to the global atmosphere (Rotty, 1973). Keeling has indicated a need for an estimate of the amount of natural gas flared in past years in attempts to determine the fraction of CO* remaining airborne (Keeling, 1973). In the modeling studies of CO2 exchanges between the atmosphere, the oceans, and the biosphere, it is essential to know the total anthropogenic production since the time man began producing COz to establish the proper exchange coefficients. The data published in the UN. Statistical Yearbook (1973) and until recently in the Minerals Yearbook (1973) of the US. Bureau of Mines for natural gas as a fuel were for “marketed production” and specifically excluded gas flared or vented and that used in repressuring the wells. To determine the total burne& the gas flared must be added to the published (marketed) production. Until now no tabulation of gas flared on a global basis has existed, although the Minerals Yearbook (1973) has given values for flared gas in the U.S. for each year since 1935. In the process of constructing these data where none has existed before, several interesting observations were made. However, so that the observations can be suitably interpreted it is necessary to describe the procedures by which the data were determined. * On leave from Old Dominion University. A.E.S/7-.,
681
682
RALPH M. ROTTY
The natural gas section of the 1970 Minerals Yearbook (1970) for the first time gives a world summary which tabulates both “gross production” and “marketed production” and that yearbook also includes data for 1968 and 1969. The gross production comprises marketed production plus the gas vented, flared, reinjected for repressuring and used to drive turbines (without being burned). In most cases the flaring and reinjection account for the difference and the gas vented and that used to drive turbines can be neglected. Thus, for each year since 1968, data for natural gas flared would be available if one could separate the amount used for repressuring from the difference of “gross production” and “marketed production”. The Office ofTechnical Data Services of the U.S. Bureau of Mines receives a completed questionnaire from most of the countries of the world giving data on mineral production including natural gas. Information is requested on amounts produced, amounts flared, and amounts used in repressuring. Individual questionnaires for 1970 and 1971 were made available for this investigation and in about half the cases reasonable numbers were found for flaring. In the other cases assistance of Bureau of Mines personnel was called upon to estimate the fraction flared vs that used in repressuring. The results are tabulated in Table 1. The years 1968 and 1969 presented a different problem in that the questionnaires from the individual countries were not available. With the assistance of Bureau of Mines personnel, including the regional petroleum experts for several geographical areas estimates on the division between the gas flared and that used for repressuring were made for 1968 and 1969. Thus, information similar to that in Table 1 for the two previous years was prepared but because of the great reliance on estimated data, the confidence level in the values for individual countries is reduced. The total world wide figure is probably accurate to within a few percent, since errors for individual countries should be at least partially compensating. The problem then remaining was that of projecting the data backwards in time to obtain estimates on gas flared prior to 1968. Bureau of Mines personnel suggested that gas flared Table I. Gas flared--1970.
Abu Dhabi Algeria Angola Argentina Austria Barbados Bolivia Brazil Brunei Canada Columbia Congo (Brazzaville) Czechoslovakia Dubai Ecuador France Gabon Germany, W. Hungary India
1970
1971
6783 5664 772 1649
9226 5664 889 1624 71
0
388 1038 3361 2252 567 2 222 538 274 2553 32 194 168 748
655 942 3172 2441 652 2 148 736 258 2589 270 215 766
1971: (in millions
of cm3) 1970
Indonesia Iran Iraq Japan Kuwait Libya Mexico Netherlands New Zealand Nigeria Oman Peru Qatar Saudi Arabia Trinidad U.S.S.R. UAR (Egypt) U.S. Venezuela World Total
1812 28970 4879 18 11477 12378 4915 267 7983 566 1438 2492 13433 1001 12942 963 13862 18446 165348
1971 2172 28497 5360 22 11801 9855 4088 96 58 12477 566 1253 3198 20917 929 12806 793 8510 16168 169887
683
Global flaring of natural gas
160 000 -
1969/
140 000 -
Non U.S. world 1968-1971
120 000 -
100 000
-
“E
eoooo-
h *
60000-
k E ::
u
40000-
/
20 000
Slope = I I I
4;3.* 47 43’ 45 1938-42
U.S. only 1935-1947
3 .;“6’
I/ V 0
500
1000
Crude
petroleum
1500
IO6 metric
2000
tons
Fig. 1. Correlation of gas flared with crude petroleum production.
should correlate best with crude petroleum production, at least in the first approximation. Most of the gas produced in gas fields is collected and marketed because the collection equipment and procedures are available. In oil fields the collection of the gas associated with the oil requires an investment which oil producers are frequently not prepared to make. For the U.S., published data exist for both natural gas flared and crude petroleum produced for the years from 1935 and to the present (Minerals Yearbook, 1973). Until near the end of World War II, the U.S. gas flared and the U.S. crude petroleum produced both increased, a situation somewhat analagous to the remainder of the world today. During the 1940’s there was a change in practice in the U.S. toward less flaring and while the national petroleum production increased, the gas flared did not follow in proportion. Since 1947 the amount of gas flared in the U.S. has trended generally downward with a few yearly increases while during this period petroleum production has risen steadily. The gas flared vs the crude petroleum production is plotted in Fig. 1 and up to 1947 a regression line with a slope of 111 provides a reasonable fit to the data as shown in the lower left of the figure. Since there was no reliable tabulation of gas flared for the rest of the world, it was necessary to estimate amounts from the data for crude petroleum. Figure 2 shows the crude petroleum production for the total world the U.S., and the world minus the U.S. production. In addition to being helpful in estimating gas flared in previous years, this figure shows several interesting things: (a) The world-wide crude petroleum production has grown smoothly along an exponential curve for the period of the figure (i.e. since 1930) while the U.S. crude petroleum production shows a steady linear growth.
684
RALPH M.ROTTY Crude
petroleum
production -70
-60 zzoo-
f % U.S.
= 20000 ', 1600: i
-50 0 ," -40 ';;
16001400-
vi -30 j
6 1200P .o IOOO-
.-
a*.. World..’
:
*.
8 ‘._
600-
-20 +on-U.S.’ World
:’
6001
.:
400
. . . ,....
‘.’
.‘,*J
_O
‘U.S.
0” ,,:.“‘,,*‘~‘.”
..I.~
- 10
t 2ooi;;In::::::::::::...
10930 , 34 I 3I 6 42 I 48 I 50 b 54 I 56 I 62 I 66 88 70 74 I,
'
Year
Fig. 2. Crude petroleum
production
(b) The U.S. produced 60 per cent or more of the worlds crude petroleum until 1950 but this percentage has dropped steadily since then and wasless than 20 per cent in 1971. (c) The non-U.S. production curve is smooth with an exponential growth rate of 9.1% y- ‘. The smoothness and rapidity of growth are indicators that the amounts of natural gas flared should be growing in proportion. The correlation of the natural gas flared in the non-U.S. world with the petroleum produced in the non-U.S. world for the years 1968, 1969, 1970 and 1971 for which data or estimates of gas flared were prepared is shown in the upper right portion of Fig. 1. Weighing the points for 1970 and 1971 (for which confidence is higher) by a factor 1.5 in comparison with the points for 1968 and 1969 gave a slope of 86 for the regression line through the origin best fitting the data. The natural gas flared in the non-U.S. portion of the world could then be estimated for prior years by multiplying the crude petroleum produced by 86 in order to get gas flared in millions of cubic meters. It should be emphasized that this line is suitable for estimation only for years prior to 1971 since the practice in non-U.S. fields shows evidence of changing as was the case in the U.S. in the 1940’s. Table 2 is a tabulation of the estimated amounts of natural gas which have been flared on a global basis since 1935. The first column is the amount flared in the non-U.S. part of the world and is determined from the crude petroleum production for the non-U.S. world multiplied by the slope of the non-U.S. regression line in Fig. 1. The second column is the U.S. gas flared obtained from Minerals Yearbook data (not from estimates based on the U.S. regression line of Fig. 1). The third column for the total world is, of course, the sum of the other two, and is shown graphically in Fig. 3. The sharp exponential rise in the recent past results statistically from the amounts reasonably well known to have been flared in 1970 and 1971 and indicates that if world crude petroleum production continues to grow along the type of curve shown in Fig. 2, then even larger amounts of gas must
Global flaring of natural gas Table 2. Estimated gas flared-106
685 m3
Year
Non-U.S. World gas flared
U.S. gas Flared
Total
Year
Non-U.S. World gas flared
U.S. gas Flared
Total
1935 1936 1937 1938 1939 1940 1941 1942 1943 1944 1945 1946 1947 1948 1949 1950 1951 1952 1953
7628 8022 8812 8975 9524 9232 9489 8194 8709 10605 10210 11729 13514 16388 18112 21210 23595 25989 28305
13871 11116 14902 18383 19181 18578 17847 17751 25547 28612 25380 31209 30243 22945 24182 22684 22463 24032 22948
21499 19138 23714 27357 28705 27810 27337 25945 34256 39217 35591 42938 43756 39333 42295 43894 46058 50021 51253
1954 1955 1956 1957 1958 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971
31326 36422 40661 44281 48228 52793 59288 64487 71952 78679 87241 95195 104256 112158 124805 137314 152724 164633
20492 21908 20589 22914 17938 16171 15941 14826 12053 10858 9629 9037 10640 13874 14627 14891 13863 8510
51818 58330 61249 67195 66166 68963 75229 79313 84005 89536 96870 104232 114895 126032 139432 152205 166587 173143
be disposed of, either by collection, processing and sale, or by flaring or other onsite disposal. It is evident that where locations make the collection economical, the practice will very rapidly change away from flaring and larger petroleum production does not indicate proportional increases in gas flaring.
i
100 -
“0 -
d
e
r, ;
..
a
..I,e,
:.
50..
‘1966-71 Observed VOItmS
.:
.
. . .. 11 34
$30
.
. . ..
36 I
.
42I
46I
50I
54 I
56 I
62 Ii
66
70 1
74 I
Year
Fig. 3. Estimated global flaring of natural gas.
686
RALPH M. ROTTY
The data in Table 2 and in Fig. 3 should be regarded as first estimates only. The confidence in these data decreases as one moves toward earlier years. It is certain however that the amounts of gas flared decrease significantly in the earlier years and a 10 per cent error in the 1935 amount is about the same magnitude as a 1 per cent error in the amount for 1970. The procedure suggested here is a method of estimating the gas flared globally for past years only. It is not recommended for projections into the future, since shortages of fuels will cause changes in procedures throughout the world. Acknowledgements-The author acknowledges with gratitude the assistance of the National Research Council through the award ofa NRC Senior Resident Research Associateship in the Air Resources Laboratories, NOAA. It was during the tenure on this appointment that the need existed for consistent data on flaring of natural gas. Dr. C. D. Keeling encouraged this study after a preliminary estimate was made for recent years in connection with atmospheric COz. Charles Kimbell and David Carleton of the Bureau of Mines were very helpful in obtaining data and estimates for flaring in many individual countries. Dr. Lester Machta has been Research Advisor for the Research Associateship, and the author is indebted for his advice and encouragement.
REFERENCES Keeling C. C. (1973) Private communication. Minerals Yearbook, (annually) Bureau of Mines, United States Department of the Interior, U.S. Government Printing Office, Washington, D.C. Rotty R. M. (1973) Commentary on and extension of calculative procedures for CO1 production. Te/lu.s 25 (5) 50885 17. Statistica/ Yearbook, (annually) Department of Economic and Social Atfairs, United Nations, New York. World Energy Supplies, United Nations Statistical Papers, Series J. No. 16. 1972,(In press) Department of Economic and Social Affairs, United Nations, New York.