GeoJournal 10.4 3 3 9 - 3 5 2

339

© 1985 by D. Reidel Publishing Company 0343--2521/85/0104--033952.10

The Acid Rain/Carbon

Dioxide Threat - Control Strategies

Bach, Wilfrid, Prof. Dr., University of MUnster, Center for Applied Climatology and Environmental Studies, Department of Geography, Robert-Koch-Str. 26, D-4400 MiJnster, FR Germany

Abstract: Many of the world's most troublesome problems are closely interrelated. A case in point is the acid rain/carbon dioxide threat. Acid rain is the commonly used synonym for the major ingredients in the ongoing regional forest dieback, and carbon dioxide is a major influencing factor in the man-induced global geophysical experiment which is feared to lead to unacceptable climatic changes. Both problems have a major common cause, namely the squanderous use of fossil fuels. For this the most effective short-term preventive control measure is the reduction of fossil fuel combustion through more efficient use which drastically reduces the pollution output by minimizing the need of having to burn fossil fuels in the first place. However, the large differences in the quantity of the emissions involved (some 20 000 million tons of CO2/yr. and about 130 and 50 million tons of SO2 and NOx, respectively) necessitate a different control measure at the source. While SO2 and NOx, the main ingredients of acid rain, can be stripped from the gas stream by technical means which are affordable, the sheer quan~ty of CO2 involved renders its sequestering and disposal technically, logistically and economically unfeasible. Through short-term measures the necessary time is gained for a sensible introduction of pollution-free sustainable resources. The long market penetration times (typically 50-100 years) force us to act now, if we do not wish to have upon us in the near future a major CO2/climate problem that is of similar severity as the acid rain/forest dieback problem of today. To my knowledge this is the first attempt to analyse the acid rain/CO 2 problems in their genetic and functional context and to present ways which lead to feasible solutions.

Introduction Today mankind is faced w i t h a number o f serious world problems including the rapid population increase, food shortages, energy waste, resource scarcity, the inequities between the developed and the developing countries, the arms race, ;nternational conflicts, nuclear proliferation, waste disposal, and last, but not least, the destruction of man's life-support system, notably the erosion of the genetic resources, the loss o f soil and vegetation through air pollutants such as acid rain, and the impacts o f a C Q induced global climatic change, especially in the area o f agriculture, thereby threatening world food security. Many o f these world problems are closely interrelated. A case in point are the threats caused by acid rain and C02 which do not only have a common source, namely the combustion o f fossil fuels, but have also a common effective control strategy, namely the reduction of fossil fuel

burning through more efficient use, thereby minimizing the need of having to burn them in the first place. There are also major differences between the two influencing factors and these involve quantity and time. Every second man puts some 600 tons of C02 into the atmosphere. This amounts currently to a staggering 20 000 million tons of C 0 2 / y r , i.e. about 150 and 400 times as much as the anthropogenic global annual emission of S02 and NOx, respectively, which are believed to be the main ingredients o f the acid rain problem. While S02 and NO x can be controlled at the source by technical means which are affordable, the sheer amounts o f C02 involved render, its sequestering and disposal technically, logistically a n d economically unfeasible (Baes et al. 1980; Steinberg and Albanese 1980). The other major difference is time, i.e. when the damaging impacts become critical. This point has already been reached in many regions o f the world for the impact

340

of acid deposition. Recent surveys show that most of the spruce and fir stands in the Black Forest and the Bavarian and Bohemian Forests are sick or dying, and that many of the other forested areas in the Federal Republic of Germany, including both coniferous and deciduous trees, are seriously damaged. No doubt, for many of these stands even crash relief programs will come too late. Nevertheless, drastic control measures will have to be taken now on both the national and international levels, if the chance for recovery of some of the lesser damaged trees and reforestation is not to be foreclosed. In contrast to acid rain, the threshold of a potentially irreversible CO2-induced climatic change is believed by most experts to be reached some time in the next century. It is, however, our present energy policy which sets the points for the CO2/climate hazard in the next century. It is exactly these long market penetration times that force us to act now, if we do not want to have upon us, in the not too distant future, a major CO2/ climate problem that is of similar severity as the acid rain problem today. Therefore, both related problems must be tackled simultaneously and now (Bach 1985b). By far the most effective short-term precautionary measures are the more efficient use of our energy resources which is the fastest and safest way to reduce emissions from fossil fuels, and the stripping of hazardous pollutants from the gas stream at the source. Both measures have been shown to be highly effective and economical. Through these measures time is gained for a sensible introduction of pollution-free sustainable resources (Bach 1982/1984, 1985a). This paper puts the acid rain/carbon dioxide threat in perspective and discusses some reasonable solutions.

Acid Rain and Forest Dieback - the Facts

Acid rain is the commonly used, but not scientifically accurate, collective term for a phenomenon which is to a large extent responsible for the dieback of forests. The term as used here is to include the three major mechanisms

GeoJournal 10.4/1985

involved, namely absorption and adsorption of gases, gravitational settling of particles, and acid precipitation which includes dissolved substances that are removed from the atmosphere by rain, snow, hail, fog and dew (Wisniewski and Klinsman 1982). Plant injury due to acid rain has been observed in the vicinity of industrial plants since the 17th century. But it was only through the tall stack policy during the last decades that the acid rain phenomenon has turned into a world-wide problem affecting now large areas of Europe, the USSR, the United States, Canada, and Japan. The Federal Republic of Germany, with a relatively large share of forest land, is not only one of the most severely affected countries, but it has also conducted the most detailed damage inventories hitherto, so that it can serve as an example of what might be in stock also for other countries. Fig 1 shows for a total of 44 test plots the development of the disease status in 556 spruce and 1675 fir trees in Baden-WiJrttemberg over the longest available sequence of seasons (Scheifele 1984). The rapidity with which a large percentage of these trees has turned from healthy to sick is quite apparent. While in the fall of 1980 all spruce trees were still grouped as healthy, by spring 1983 a healthy tree could no longer be found in either tree species. The results from a nationwide inventory for the three ye~s 1982 to 1984 are now also available (BML 1982, 1983, 1984). Although not entirely comparable, because in 1982 different methods were used, the obtained results do nevertheless indicate that injury has become more severe and more widespread affecting now all trees in all parts of the FR Germany. Tab 1 indicates that coniferous trees, and above all fir trees, are most severely affected, but that deciduous trees follow suit quickly. There is a sixfold increase in the overall injury rate between 1982 and 1984. Tab 2 shows that the damaged forest area in the FRG has increased more than sevenfold from ca. 0.5 mill. ha in 1982 to 3.7 mill. ha in 1984. Most severely affected are the southern German lands of Baden-WLirttemberg and Bavaria and the city states of Hamburg and Berlin with well over

Tab 1 Areal Extent of Damage by Type of Treefor 1982, 1983 and 1984 in the Federal Republic of Germany

Source: BML (1982, 1983, 1984).

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341

% SPRUCE ( 17 OBSERVATION PLOTS WITH 556 TREES ) 100 m:lim:m:l:': : ) 90 :2:121111112 '.'.'.',-.'. 80 70 60 50 4 0 "...'.,.,.., 30 20 10 0 1980 1981 1981 1982 1982 1983 1983 1984 Fall Spring Fall Spring Fall Spring Fall Spring ".'.'.'.'.', '.','.'.'.'.

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Light Heavy Very Heavy

0.419 0.108 0.035

1.846 0.635 0.064

2.424 1.163 0.111

6 1.5 0.5

25 8.5 0.9

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Total

0.562

2.545

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8

34

50.2

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% 100 90 80 70 60 50 40 30 20 10 0

Percent of Forested Area 1982 1983 1984

...,.........

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Damaged Forest Area (Mill. ha) 1982 1983 1984

.....,...,...

Tab3 Areal Extent by Severity of Damage for 1982, 1983 and 1984 in the Federal Republic of Germany

FIR (27 OBSERVATION PLOTS WITH 1675 TREES )

1980 1981 1981 1982 1982 1983 "1983 1984 Fall Spring Fall Spring Fall Spring Fall Spring ~

healthy NEEDLE LOSS: 0-10

slightly injured 11-20

~

injured 21-60

m

severely injured 61-99

m

category experience a" preferred cut whilst they are still of some economic value. It is very likely that other countries would find similar damages, if they had conducted comparable inventories. Adopting the German sampling method Luxembourg and Switzerland found that in 1984 already 16.8% and 34% of their forests were damaged, respectively (Lehringer 1985). It should also be realized that with the present effectiveness of national and international air pollution control legislation, in the foreseeable future, the trend of damages is a one way road from light to heavy.

dead 100%

Possible Causes of Forest Dieback Figl Trend and disease status of fir and spruce trees in BadenWfirttemberg Adapted from Scheifele (1984)

half their forests damaged. Finally, the tabulation by severity of damage in Tab 3 shows that the individual shares within the injury classes have increased from 1982 to 1984 - but not equally. The share and the increase in class "very heavy" remained small, because trees in this

It is fairly save to say that hypotheses which relate the forest dieback to any one single cause fail to explain this complex phenomenon. The new damages leading to forest dieback are not mono-causal but rather a multiple stress problem (Ulrich and Pankrath 1983; Ulrich 1984; SchiJtt et al. 1984). There is a host of abiotic and biotic influencing factors involved which can be grouped into six categories (Moosmayer 1984; SchiJtt et al. 1984; Reichelt 1984):

Tab 2 Areal Extent of Damage by Federal Land for 1982, 1983 and 1984 in the Federal Republic of Germany

Source: BML (1982, 1983, 1984).

342

•

• • • •

•

GeoJournal 10.4/1985

primary and secondary air pollutants (such as sulfur dioxide, nitrogen oxides, sulfuric and nitric acid and their corresponding sulfates and nitrates as main ingredients of acid rain; ozone and organic peroxides; fluorines; heavy metals and dust) weather and climate biotic factors (such as fungi, viruses, viroids, mycoplasmas or bacteria) forest site and forest management radioactive radiation (from atomic test fallout, uranium mining, nuclear power stations and reprocessing plants) electromagnetic waves (from radar and other stations transmitting mainly in the microwave range, and low frequency electromagnetic fields).

Regarding the appropriate control strategies the answer to the question which of the above factors are of primary and which are of secondary importance must be clarified first. It is often argued that monoculture, forest growth at sites unfavorable to the respective species, lack of cultivation and fertilization have weakened the forests to the point that they now dieback on a large scale (ACI 1983). The fact is, however, that the widespread forest dieback began with the dying of the fir tree which is hardly ever found in monoculture. Moreover, the fir tree in Germany is dying in areas that belong to its optimal habitat. It is interesting to note that the spruce tree which is often grown in monoculture began to develop symptoms of the disease years after the fir tree. More interesting still is the fact that dieback in spruce trees was not first observed in lowland monocultures unsuitable for spruce, but in the exposed parts of the upper mountain ranges which are the natural habitat of spruce. Next in line to become affected were pine, beech, ash, birch, and elm trees which almost never occur in monoculture. Forest dieback is not restricted to any specific form of forest growth and cultivation methods so that bad forest management can be excluded as a primary cause. Spells of drought, heat and frost are often quoted as main stress factors responsible for forest dieback (Cramer and Cramer-Middendorf 1984). For this hypothesis to hold damage should occur immediately after a drought, only drought-sensitive trees should be affected, the observed symptoms after different droughts should be the same, and tree injury should be noticed first on sites known to be more susceptible to drought. None of this has been observed (ACI 1983; Burschel 1985). On the contrary, irrespective of drought or other climatic factors the dieback began with spruce trees followed by fir trees in early 1980 unrelated to the drought years of 1969, 1971, 1973, and 1976. Even the droughtresistent pine tree with its tap-root is not spared in the ongoing dieback process. Besides, forest dieback started in the rainy highlands and not in the drier lowlands. More-

over, there is no connection between the regional occurrence of severe frost spells and forest dieback. If there were, deciduous trees should be affected first since they are more frost-sensitive than coniferous trees - but this has not been the case. From this we can conclude that climatic factors (Rehfuess and Rodenkirchen 1984), and often as an aftermath, viruses (Kandler 1983) and pests, (Eichhorn 1981), as well as the tack of fertilization (Evers et al. 1984) and bad forest management are all important contributing factors which can further weaken the trees, but that this wide-spread occurrence of dieback across all tree species cannot reasonably be explained without the effect of air pollutants from the combustion of fossil fuels. The present state-of-the-art on the causes of forest dieback is sufficient to justify measures which lead to a rapid and comprehensive reduction of air pollutants. Before discussing suitable control strategies it is appropriate to look at the emission characteristics of some of the main acid rain ingredients, namely SO2 and NOx.

S u l f u r and N i t r o g e n O x i d e s f r o m Fossil Fuel Combustion The release of SO2 per unit of energy production differs for different fuel types (depending on the S-content of the fuel used) and for different combustion sources as shown in Tab 4. Clearly, for the same fuel type power plants emit considerably more SO2 per unit energy than residential and commercial sources. Gas contributes by far the least to S-pollution. Tab 5 shows the most common air pollutants and radionuc[ides from burning coal, oil or gas in a 1000MWe power plant. Notably, the coal-burning system emits the largest amounts of pollutants, except for aldehydes, hydrocarbons and NO2. All of these air pollutants are contributing factors to forest dieback. Note, for comparison, the extremely large amounts of CO2 emitted by coal- and oil-fired power plants. These are not related to forest dieback but are of concern to questions of climatic change and its impact as discussed

Tab 4 S02 emission factors (kg/TJ) by fuel source for power plants and residential and commercial use

1) S = heavy distillate; 2) EL= medium distillate After Fritsche (1982)

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343

Tab 5 Annual emission of air pollutants from a 1000 MWe fossil fuel power plant operating at a 75 % load factor

Source: Bach (1981)

in the following section. Because of the enormous quantities involved, the stripping of CO2 from the gas stream, a common control method for SO2 and NOx, is not feasible for CO2. From an air pollution effects point of view it is revealing to evaluate how much the various sources contribute to their immediate vicinity and how much to remote areas. Fig 2 shows that in the Ruhr district 40% of the SO= emissions are from power plants, 50 % from industry, 9 % from residential and commercial sources, and 1% from transportation. However, due to the different emission heights the SO2 concentration in the surrounding areas is largely due to industry (60 %) and residential and commercial sources (23%). The tall stack policy is responsible that most of the SO=-pollution from power plants and also industry is spread over great distances Fig 2 Effect of various emission groups in the Ruhr District on ambient air quality in the vicinity and in remote areas 180~ Adapted from Arbeitskreis Chemische Industrie (I 983)

thereby contributing significantly to the acidity of the rain and the ensuing dieback of forest trees. The trends in the use of coal and oil in Europe from 1900 to 1972 are closely matched by the SO2 trends over the same time period (Fig 3). It is tempting to relate the sharp rise in coal and oil use together with the steep SO2 increase over the 20-year period beginning in 1950 to the dramatic increase in damaged forest area as observed in recent years. There is a concensus that the high air pollution levels have to be drastically reduced. Tab 6 shows that over the period of 1966 to 1982 in the FR Germany the emission trend of suspended particulates has been steadily downward followed by a similar downward trend also in SO2 and organic compounds. As for NOx, the major ingredient of the damaging photochemical oxidants, the steep upward trend seems to be stabilizing at

Responsible for Damage in Vicinity Emi

sio

n

Immission

Responsible for Damage in Remote Areas Immission

Power Plants

Power Plants 40% Industry 50% Residential & Commercial9% I

75-

!~

Residential& Transportation Oistance from Urban / Industrial Area Slack - height (m)

344

GeoJournal 10.4/1985

the relatively high value of 3.1 mill. t/yr. The ongoing forest dieback demands that without any further delay, emission of these pollutants must be controlled at the source much more effectively, if the trend in the rapid dieback of forests is to be reversed. The control strategies available to do this are discussed after the following section.

- 50 1000-

~20-

-4o~ -3o -=0 ~~ ~ =~

so2

.=?::===::

15500-

1900

1920

1940

Year

1960 1972

1900

1920

1940

1960

1972

Carbon Dioxide from Fossil Fuel Burning

Year

Fig 3 Use of fossil fuels and SO2-emission in Europe, 1900-1972 Adapted from OECD (1981)

Another major substance produced during fossil fuel combustion is carbon dioxide. The huge quantity of some 20000 mill.t of CO2 presently emitted into the atmosphere per year dwarfs the ca. 130 mill. t/yr of SO2 and the ca. 50 mill. t/yr of NO x. To put this, however, in the right perspective it must be realized that CO2 at these

Tab 6 Trend in annual emissions (Mr, %) of sulfur doxide, nitrogen oxides and hydrocarbonsby emissionsourcefor the Federal Republic of Germany, 1966-1982

Adapted from BMI (1984)

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345

quantities is not a health hazard, whereas both SO2 and NO x at these amounts constitute a severe threat not only to living beings, such as man, animal and plant, but also to inanimate matter. The mechanisms involved in the CO= threat are quite different from those of SO2 and NOx, while the magnitude of the potential socio-economic damage is again quite comparable. Carbon dioxide, by letting penetrate the shortwave part of the solar radiation to the earth's surface and by trapping the [ongwave outgoing radiation, leads to a warming of the lower atmosphere, the well-known greenhouse effect. This, in turn, will bring about a distinct alteration in the regional and seasonal behavior of climate, which, in view of the increasing world population, could have catastrophic consequences for the world's water, food and energy supplies. Before, in the following section, control strategies are considered it is appropriate to take a look at the emission characteristics of CO2. The CO2 release from a fossil fuel depends on its hydrogen: carbon ratio. As the H:C ratio increases, the energy per unit CO2 output increases. Tab ? shows that oil has a factor of 1.5, coal one of 1.8, oil shale one of 2, synthetic fuels one of the order of 3, and recent biomass (wood) only a fraction of the CO: emission from natural gas. Using the emission factors (kgC/MWh) also shown in Tab ? and UN production statistics, the amount of carbon released by coal, oil and gas, by gas flaring and cement production can be calculated for individual countries (Keeling 1973; Marland and Rotty 1984). Fig4 shows that the total global carbon emission has increased from about 0 . 1 G t C 1) in 1860 to ca. 5 . 1 O t C in 1982. This corresponds to an average exponential growth rate of

F i g 4 Global CO2-production from fossil fuels, cement and gas flaring, 1860-1982 Source: Keeling (1973 for 1 8 6 0 1949); Marland and R o t t y (1984 for 1950-1982)

4,0 3.G

Adapted from JASON (1980) Tab 7 Comparison o f carbon dioxide release from production o f thermal energy by various fuels (average values)

3.4%/yr only interrupted by WWI and WWII and the first world economic crisis. The detailed breakdown in Fig. 4 shows that the drastic increase in energy costs, resulting from the energy crisis of 1973/74, apparently was able to slow down the fast growth of oil consumption from 7.1%/ yr to O.04%/yr and that of gas from 8.1%/yr to 3.3%/yr. Coal has slightly increased from 1.7%/yr to 2.6%/yr. In the mid-1960s oil became the largest contributor to atmospheric CO2. It appears that coal will soon resume first place again, especially if more of the unconventional fossil fuel sources (coal gasification and liquefaction) are put tO use.

I0,000

-

u J"

5,000

2.0 -r D.. 09 0 ~1.0 < 0.8 -iI.-. 0.5

Z 0.4 O 0,3 O < 0.2 FZ U../ ...1

3,000 2,000

1,000

500~

3ooi 0.1

20G

0

100 18@

, , I I I I I f 1870 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 19;0 YEAR

346

The growth rate for the overall CO2 emission has decreased from the long-term mean of 3.4%/yr (1860 1980) to the present rate of 1.5%/yr (1974-]982) with the prospect of a further reduction due to the increasing resource scarcity and the expected long-term price increases (Bach 1985c). This encouraging trend is taken by most governments as a pretext to ignore again the CO2/climate threat, because its impacts appear to become effective in a more distant future. This ignores, however, the large array of the other infrared-absorbing gases, such as CFM, N20, CHa, 03 etc., which also grow exponentially and which, in part, have a considerably longer residence time in the atmosphere than CO2 (Bach 1984). Many believe that the total contribution of these trace gases is comparable in magnitude to that of CO2. Viewed realistically, this means that, despite the desirable reduction in fossil fuel use, the added effect of the other forcing factors brings us back to the former urgency. C o n t r o l Strategies Decision-makers, in their daily work, are confronted with a host of environmental problems, notably the acid rain and the CO2/climate threats. Although these may indeed have catastrophic consequences for mankind, in the past they have been pushed aside on account of insufficient information regarding the causes (viz. the acid rain problem), or because the problem threatens to become acute only in the distant future (viz. the CO2/climate risk). A course of action, involving first of all the collection of sufficient information (who decides how much information is sufficient?) and only then to make decisions, sounds reasonable but brings us into a dilemma. This is because in the case of acid rain the dieback of forests is so rapid that only crash programs can bring relief, and because in the case of CO2 the present energy policies, that opt for specific energy carriers, thereby also determine the levels of CO2 in the atmosphere and related climate variations for the coming decades. Therefore, relief measures, if they are to be at all effective, must already be introduced now. If we wait until we know all the causes, in the case of acid rain there may not be much vegetation left to be protected. If we wait until the atmosphere itself performs the experiment so that we can- unequivocably determine the C02-induced climate effects, it would be too late for countervailing measures (Bach 1982/1984). There are three main control strategies which, used in combination, can bring the necessary relief on time. These are: energy consumption reduction through more efficient use emission reduction through abatement techniques, and energy source substitution using non-polluting technology.

GeoJournal 10.4/1985

Efficient energy use Presently about 84% of our energy use is based on fossil fuels, and this is not likely to change dramatically in the future. Therefore, the more efficiently we use energy, the smaller will be the consumption of fossil fuels, and the smaller will be the emissions of SO2, NOx, CO2 and a host of other hazardous substances. The potential for improving energy efficiency is very large. Methodically convincing empirical studies from about a dozen different countries show through a least-cost energy approach, which implies that people will use energy in a way that saves them money, that in the future energy needs, and hence fossil fuel use, can be expected to go down, not up. The same or even more energy services can be offered with a lower energy input simply by increasing energy productivity (Lovins et al. 1981/1983; Bach 1985d). Without requiring any technological breakthroughs much can be achieved simply by applying present technological knowledge in a rational way. For example, the overall efficiency of conventional power plants could be increased from about 36% to 85 % simply by cogeneration, i.e. by combined heat and power generation. By building decentralized neighborhood cogeneration systems the losses incurred in transporting energy and the investment needed for grid systems could be significantly reduced. With fluidized bed combustion, not only is efficiency increased by 10%, but also the emission of SO2 and NO x is reduced drastically, as is shown in the next section. Efficient insulation is one of the most effective means of reducing fuel consumption. Sodium-vapor, quartz-halogen lamps are now available that use 75% less current than conventional light bulbs while lasting 4 5times longer. Fuel consumption of motor cars can be reduced with existing technology from the current level of 8 101/100km to about 2 1/100 km in a VW Rabbit (Golf) type car. More specifically, Tab 8 shows the savings in primary energy in various heating technologies as compared to a conventional oil central heating system. ]-he reduced primary energy demand translates into reduced SO2 emissions. Most effective are the gas heat pump, passive-solar construction with insulation, and insulation plus double glazing. Note, on the other hand, the significant increase in SO2 emission, if electric heat pumps and direct electric night-time heat storage are used. The results of a detailed study comparing different energy scenarios are highlighted in Tab 9. Compared to 1980 the low and high IIASA 2) scenarios (Haefele et al. 1981; Rogner n. yr.) postulate increases by 2030 of 1 2 fold for oil, 2 - 4 fold for gas, and 3 -5 fold for coal. This is in sharp contrast to the efficiency scenario developed for the German Government (Lovins et al. 1981/1983) which finds reductions of 17 fold for oil, 5 fold for gas, and 7 fold for coal cost-effective. The need for the enormous increase in nuclear power from 0.30TW (1980) to 8.09

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Tab 8 Effect of efficiency technologies on primary energy use and SO 2 em ission

I) Values are not accumulative. 2) All percent values are related to a conventional oil heatingsystem; emission factor 200 kg SO2/T J. 3) E.g. electronic sensors and thermostats, thermostatic valves, electronic fuel-air mixing regulators, etc. 4) Monovalent system. 5) Emission factor 6 X lO-3kgSO2/kWh for electric current. Source: Fritsche (1982)

TW (2030) in the high I I A S A scenario is justified by proponents o f nuclear power as a means to reduce fossil fuel use and hence air pollution. This measure can, however, not be very effective, since at the same time, this scenario postulates a dramatic increase in fossil fuel use

f r o m 8.40TW (1980) to 24.78TW (2030). In stark contrast to this, the scenario based on economically efficient energy use requires o n l y about 1 TW o f fossil fuels in 2030, so that the rest can be supplied fairly easily by pollution-free renewables, leaving no need for nuclear

Tab9 Global primary energy supply(TWyr/yr) for different energy sources and a variety of energy scenarios, 1980 2030

1 Using the fuel shares of the low I IASA scenario; the 16 TW scenario is also known as the "zero growth scenario" because it assumesthat the present per capita energy consumption will be the same in 2030 but that a doubling in world population from 4 to 8 billion will lead to a doubling in total energy consumption. 2 Mostly soft solar (e.g. rooftop collectors) but also small amounts of centralized solar electricity. 3 Includes biogas, geothermal, commercial and non-commercial wood use. Sources: Colombo and Bernardini(1979),H~.feleetal.(1981),Lovinsetal.(1981),and Rogner(n.y.)

GeoJournal 10.4/1985

348

energy which itself is plagued with a host of unsolved problems, (e.g. waste disposal, proliferation), and reducing, at the same time, significantly the acid rain and CO2/climate threats. In summary, an economically efficient energy future in 2030 would not require a 3.6 fold increase in global primary energy demand as postulated for the high I IASA scenario, but would rather result in a 48% decrease as derived by the efficiency scenario (Tab 9). These differences produce strikingly different effects. Interpreting only the highest and the lowest estimates it is seen that compared to base year 1980 the IIASA high scenario in 2030 shows a 3fold increase in CO= emission (Fig5) and a 55% increase in CO2 concentration (Fig6) resulting in a more than 4fold increase in global air temperature over the 1946-1960 mean value from 0.4 to 1.9°C for the CO2 effect only (Fig 7). For the combined effect, i.e. CO2 plus other trace gases, we obtain an almost 8fold increase from 0.4 to about 3°C (Fig 8). In contrast, over the same time period, the efficiency scenario shows a 9fold decrease in CO2 emission (Fig 5) and only a 14% increase in CO2 concentration (Fig 6) leading to a mere 2fold temperature increase for the CO2 effect only (Fig7). Again, when adding other trace gases the temperature increase is enhanced 4fold instead of twofold (Fig 8). To put this in perspective for the total effects, the high growth I IASA scenario could result in a warming that has not been experienced since the mid Pliocene (ca. 5 - 3 million years ago), and for the efficiency scenario this could lead to a warming similar to that in the Eem-Sangamon Interglacial (ca. 125 000 years ago).

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36 TW High Scenario ( i l ASA 1981 ) 22 TW Low Scenario ( II ASA 1981 ) 16 TW CEC ~Scenario ( Colombo/Bemardini 19 r9 ) 5.2 TW Efficiency Scenario (Lovins et a1.19811)

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Fig 5 Simulation of CO2 emission from UN fossil fuel statistics (1860--1980). Projection to 2030 based on energy scenarios -

500-

1 36 TW 2 3 4-

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I ',

/ i -50( -500

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C O 2 concentration

based on C O 2 emission

Fig7 Simulation of temperature response to CO 2 effect only (18601980) and projection to 2030 4.0 It o O v

3"5t! 3.0 2.5- ,

36 22 16 5.2

TW TW TW TW

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G e o J o u r n a / 10.4/1985

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349

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Abatement techniques Theoretically there is a host of technical fixes available for CO2 reduction. Amongst these are the removal of CO2 from flue gases or from the atmosphere, storage of CO2 in the oceans and in caverns, recycling of CO2 in coal-based chemical industries, efforts to compensate for increasing CO2 by modifying the albedo, and finally, storage in fast growing plants. The problem of CO2 removal and storage is one of quantity and cost. The current annual global CO2 production amounts to some 20000 mill. t compared to about 130 mill. t of SO2 per year. It is the unanimous opinion of all experts who have carefully studied such technical fixes that they require too much energy, and, because they are unaffordable, are unfeasible for CO2 control. Albedo manipulation is fraught with many uncertain outcomes and is best left alone. Fast-growing plants can serve as an important interim carbon storage, if the potential for CO2 sequestering is not neutralized by the acid rain impact (Bach 1982/1984). In contrast to CO2, the smaller quantities involved make the control of SO2 and NO x much more feasible. The available abatement techniques for stationary sources such as industry and power plants can be grouped into three categories(Persson 1976; SMA 1982):

-

-

those that reduce the sulfur content of the fuel prior to combustion (coal cleaning, coal gasification, desulfurization of liquid fuels, e.g. MUller 1984; Henne and Elsaesser 1984}; those that reduce SO2 emission during combUstion (burner technology, fluidized bed combustion, e.g. Bitterlich 1980}; and

--

those that reduce SO2 and NOx emissions a f t e r combustion (flue gas control, e.g. Baumbach 1984).

C o a l c l e a n i n g - Bituminous coal contains both pyritic and organic sulfur in roughly equal proportions. Coal washing is standard practice for the removal of ash. Washing and other physical separation techniques used to remove pyrites can reduce the sulfur content of coal by 40 to 60% by weight at a cost of $ 2.50 to g 3.25/t (at 1975 US prices). However, these processes cannot remove the organic sulfur in the coal. Coal gas/f/cation a n d / i c l u e f a c t i o n - Currently available techniques can remove up to 90% of the sulfur from the gaseous and liquid fuels. The costs of sulfur removal are likely to be low compared to the cost of gasification or liquefaction. o f l i c l u i d fuels - There are a number of processes available. Desulfurization of gas oil achieves a sulfur removal of 90% requiring an additional 3.5% of energy for the removal process. Direct residual fuel oil desulfurization can reduce the sulfur level of the residue by ca. 80% requiring 6 - 8 % additional energy of the feedstock. The degree of desulfurization that can be achieved by the indirect method of residual fuel oil desulfurization is only about 30-45%; and the additional energy consumption is about 5%. Desulfurization plants require for planning and construction a lead time of 3 to 5 years. Tab 10 shows cost comparisons for the various desulfurization methods. Desulfurization

B u r n e r t e c h n o l o g y - Through the use of multistage burners

80% of the SO: and 50% of the NOx can be removed as compared to emissions from conventional burners. The

350

Source: Persson(I 976) Tab 10 Desulfurization costs (1974 price level)

additional cost of combustion modifications is generally less than 1% of the capital cost of the power plant. F l u i d i z e d b e d c o m b u s t i o n - The boiler consists of a reaction chamber in which finely ground coal is burned in suspension over a bed of moving air in the presence of fragmented limestone capable of removing SO2. The movement of the coal particles gives a larger heat transfer thereby making a boiler of half the usual size possible and improving the energy efficiency by 10%. Fluidized bed combustion is most suitably used in connection with smaller-scale cogeneration plants, thereby reducing the waste heat release by 80%, the SO2 emission by close to 95% and, as a result of the lower combustion temperatures (800-900°C as compared to the usual 1600°C), the NOx emission by about 50%. Many experts consider this the most promising process. Additional investment costs are less than $10/kWe (in 1982 US $).

There are two main processes, the dry and the wet scrubbing of stack gases. In the dry process gases pass through a bed of absorbant, such as activated coal, which reacts with the SO2 in the flue gas. When the absorbant is fully loaded with SO2, clean gas is passed through the bed, stripping out the SO2, which is subsequently converted to sulfur or sulfuric acid. This method can only remove some 50% of the SO2 in the stack gas. In the wet process the gas is washed with an alkaline solution removing up to 95% of the SO2 from the stack gas. The SO2 is converted to a waste product (sludge) or to a saleable b'y-product (gypsum). For cost comparisons see Tab 10. Catalytic methods achieving NOx removal rates of up to 80% are practised widely in Japan. The costs of these systems amount to about 5 % of the total cost of generating electricity. Significant advantages of this method over the coal conversion route are that the total capital and operating costs are almost an order of magnitude lower, that Flue "gas c o n t r o l -

GeoJournal

10.4/1985

thermal efficiencies are higher, and that utility requirements are lower (Yan 1984). Abatement techniques for mobile sources are the other major control strategy to reduce air pollution. These include speed limits of 100km/h and 80km/h on freeways and interstate highways, respectively; leadfree gasoline; catalysts and lean fuel mixtures. Speed limits exist in every industrialized country, except for Germany. Given the political will they could be introduced immediately. US and Japanese cars were equipped with catalysts during the 1970s. European Community policy is set up to prevent effective catalyst use in Common Market countries until the 1990s. Automobile exhausts substantially contribute to the lead, NOx and hydrocarbon (HC) pollution. NO x is a major ingredient in acid rain, and both NO x and HC together with sunlight produce the photochemical smog. All of these pollutants are considered to be causally related to forest dieback.

Energy source substitution The more widespread use of renewable energy resources and nuclear energy has been suggested as a substitution strategy for the reduction of SO2, NOx, CO2 and a host of other hazardous substances. Except for biomass burning _which would produce small amounts of SO2 and NO x as compared to fossil fuel burning, and CO2 which would be recycled if used in bioplantations together with reforestation, all other solar-based renewables operate pollutionfree. IIASA (H~fele et al. 1981) and UN studies (Bach et al. 1980) have estimated a theoretical global potential of 20 to 30TW and a practicable potential of about 10TW. Tab 9 has shown that if energy is used efficiently in a costsaving manner, then the required global demand of 4.3TW allocated to pollution-flee renewables can be met fairly easily by 2030 (Lovins et al. 1981/1983). The potential of nuclear energy to substitute other fuels with the purpose of reducing the acid rain and the CO2/climate threats is less clear and thus warrants a closer look. In the FR Germany nuclear energy produces close to 30% of the electricity (which itself accounts for ca. 15 % of the end-use energy) so that it approximately supplies 4.5% of the end-use energy. In 1980 savings in the use of heating oil alone amounted to about 10% of end-use energy. German power stations use less than 5% of the total oil to produce electricity. More than 53% of the oil is used to produce heat. Thus, to make a noticeable contribution, nuclear power would have to penetrate the heat market. A power plant of the Biblis type (1300 MW) would produce ca. 6.8 bill. kWh/yr or 0.84 MTCE 3) electricity equivalent, taking a load factor of 60%. The present German oil consumption is about 190 MTCE. Thus 10 large nuclear power plants could just replace barely 5% of the oil, half that experienced through savings in the

GeoJournal 10.4/1985

heating oil sector alone. The situation is not much different in other industrial nations (Bossel/Hoecker 1982). In the report of the Enquete-Commission (1980) to the German Parliament, energy path I projects, compared to the base year 1978, for the year 2030 a 24% increase in fossil fuel use while at the same time considering a staggering 16fold increase in nuclear power. In contrast, energy path 4, by following a strategy of more efficient energy use, shows a reduction of 43% in fossil fuel use while, at the same time, finding no need for nuclear power. Similar results were found for global energy scenarios. As shown above and in Tab 9, the high IIASA scenario postulates over the period of 1980 to 2030 a 27fold increase in nuclear power and at the same time a 3fold increase in fossil fuel use. Again, in stark contrast, the scenario based on the efficient use of energy finds that a strategy reducing fossil fuel use 9fold, phasing out nuclear power, and supplying the remainder demand of 4.27 TW with renewables, is the most cost-effective. With the siting and acceptance problems inherent in nuclear power plant construction, it would take at least 10 to 30 years to put on line the 30 to 40 large nuclear power plants required as a minimum to replace the existing fossil fuel plants in Germany. This, very definitely, would come too late to halt the acid rain catastrophe. Because of the long world-wide market penetration times (50 years plus) for energy supply systems it would almost certainly take too long also to reduce or avert a CO2/ climate threat. In contrast, the efficiency measures and the abatement techniques have very short lead times (< 1 to 5 years), and are hence inherently more suitable as effective control strategies than nuclear power. The 30 to 40 nuclear power plants would require an investment sum of at least 190 billion marks at current prices - ignoring all corrollary costs. According to the German utility industries desulfurization of the stack gases by 50% of the current values in all existing fossil fuel power plants would require an investment of some 6 bill. marks - or just the construction costs of one single 1300 MWe nuclear power plant. The use of the various available flue gas desulfurization methods with SO= removal efficiencies of 85 to 95 %, such as atmospheric and pressurized fluidized bed boilers and cogeneration, could, by the year 2000, effectively remove all SO2 emissions up to a small residual costing about 20 bill. marks. To this should be added the 20 to 30 bill. marks slated by the German Government for investment in the extension of the district heating grid. Thus for a total of 50 to 60 bill. marks the acid rain problem could be effectively prevented supplying at the same time some 50000 people with a secure job. To provide the same number of people with jobs would require the construction of about 13 nuclear power plants costing some 85 bill. marks. Thus, investment in nuclear power instead of sulfur control would cost much more, provide fewer jobs, and by barely replacing some 6% of

351

the German oil consumption, would have an almost negligible potential to reduce SO2 emission (Goez et al. 1982). Finally, by first making the energy supply system more efficient the overall demand can be markedly reduced so that in the case of the efficiency scenario shown in Tab 9 the modest supply of some 4.3 TW through renewables does not require any large-scale encroachment on the environment. The decentralized use of renewables at a scale appropriate to do the respective job, and the efficiency improvements discussed above are all known and will not cause any additional risks to man or his environment. In stark contrast, the risks from nuclear power are manifold and grave including the release of radionuclides to the environment involving the entire fuel cycle, the likelihood of accidents, the disposal of wastes, and the proliferation of nuclear fuel for the purpose of manufacturing atomic bombs. The suspicion is growing that nuclear power is also a contributing factor to "Waldsterben" (Reichelt 1984a, b). Recent forest damage inventories revealed for a number of nuclear power plants (Obrigheim, Wiirgassen and Esenshamm in Germany as well as Bugey in France) that forest damage is significantly enhanced downwind of the main wind direction. In the vicinity of the Karlsruhe reprocessing plant it was found that Krypton (8s Kr) in air, and tritium (3H) in water and in pine needles had increased by a factor of 5000, 40-160, and 9, respectively. 14C, 8s Kr and 3 H are known to reduce the enzymatic power of plants to repair damages so that the more conventional pollutants (SO2, NOx, 03, heavy metals etc.) can have a greater adverse impact. Finally, radioactive substances cause cancer and genetic defects in humans and other life forms living now and in future generations. Therefore, nuclear power is quite unsuitable as a strategy to replace fossil fuels, and hence to reduce the acid rain and CO2/climate threat.

Footnotes I)

I G t C = 109 or billion tons of C corresponds to 3.67 Gt of

CO2 2) 3)

IIASA: International Institute for Applied Systems Analysis, Austria MTCE= million tons of coal equivalent -~ 928 X 103kWyr

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