Pollution of the Atmosphere

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Energy generation also pollutes the atmosphere as well as the land and the sea. Several estimates of the atmospheric carbon dioxide emissions are given in Table 6.2. They agree reasonably well and show very clearly the overwhelming preponderance of emissions from the fossil fuels coal, oil and gas. In sharp contrast, the emissions from nuclear, wind and hydro are only around 1% of those due to the fossil fuels. The relative emissions due to various sources in the European Union are: oil 50%, coal 28% and gas 20%. In terms of consumer sectors electricity generation accounts for 37%, transport 28%, industry 16%, household 14% and the service sector 5%. The emissions from transport are expected to increase by 50% between 1990 and 2010 (Nuclear Issues 23, March 2001). Worldwide, the relative emissions are oil 42%, coal 37% and natural gas 20%. Between 1990 and 2001 world carbon dioxide emissions increased from 21,563 to 23,899 million tonnes (US Department of Energy Outlook for 2004; Nuclear Issues 27, March 2005).

There are notable differences in the emissions in various countries, as shown in Table 6.3.

The emissions of carbon dioxide from various form of transport in grams of carbon dioxide per 100 passenger-km are 278 for an average 1990 car; 161 for a diesel car; 69 for a bus; 79 for a diesel train; 76 for

Table 6.2. Atmospheric Carbon Dioxide Emissions in g/kWh

Energy Source

OECD

BNFL2001

Vattenfall*

NI2007

Coal

955

955

980

750-800

Oil

828

818

550

Gas

430

446

450

400-440

Nuclear

4

4

3.1

15

Wind

8

7

5.5

10-30

Hydro

8

4

5-20

Biomass

17

30

Geothermal

79

Solar

133

*Vattenfall is the Swedish State Power Board (Nuclear Issues 28, January 2006).

*Vattenfall is the Swedish State Power Board (Nuclear Issues 28, January 2006).

Table 6.3. Atmospheric Carbon Dioxide Emissions in g/kWh (Kivisto 2000)

Japan

Sweden

Finland

Coal

975

98G

894

Gas (Thermal)

6G8

ll5G

Gas (combined cycle)

519

45G

472

Solar photovoltaic

53

5G

95

Wind

29

5.5

l4

Nuclear

22

6

1G-26

Hydroelectric

ll

S

Table 6.4. Values of the Kyoto Index for the UK in 1999 (Nuclear Issues 22, November 2000)

Source

Electricity

GWh

Mte Kyoto

Generated

Carbon

Index

Coal

lG6G72

26.52

G.5

Oil

555l

l.ll

G.6

Gas

l4lS65

l7.67

l.G

Nuclear

9628l

G.24

5G

Biomass

8S77

G.lG

lG

Hydro

5S52

G.GS

2l

Wind

898

G.GG5

24

an electric train and 853 for aircraft, assuming 80% occupancy for aircraft and 40% for the other modes of transport (MacKay 2008, p. 135).

The relative purity of the emissions from different energy sources can be measured by the Kyoto Index, which is the percentage share of generation divided by the percentage share of carbon emissions. Values of this Index for emissions from the UK in 1999 are given in Table 6.4.

The pollution due to the fossil fuels is partly the carbon dioxide that is a natural product of the burning fuel and partly a wide range of poisonous chemicals due to impurities in the fuel. This latter pollution depends on the constituents of the fuel, and some typical figures for coal are given in Section 2.2. Much of this returns to the earth in the form of acid rain, and is responsible for the destruction of forests and the poisoning of seas and lakes. In the 1920s and 30s lakes in Scandinavia lost most of their salmon and trout and by the 1980s, 4000 lakes were almost dead and 5000 had lost most of their fish. Other forms of aquatic life and birds were also affected, and conifers, beech, oaks and spruce in the forests of Europe and North America were observed to be dying (Christianson 1999).

Initially it was suspected that the effects on the trees were due to some virus, but measurements of the acidity of the rainwater showed that it was due to industrial effluent from factories hundreds of miles away. It was thought that pollution could be avoided by building taller and taller factory chimneys, but this serves only to spread the poisons even more widely. The only solution to the problem of acid rain is to remove the pollution at its source.

Detailed surveys are necessary to assess the extent of the effects of acid rain and some studies have shown that the effects are comparatively small; for example, it has been estimated that acid rain affected only about 0.5% of the European forest area. Many lakes are still affected, though most are recovering due to reductions in the emissions of sulphur dioxide. In some cases, the sulphur and the nitrogen in the acid rain actually helped plant growth (Lomborg, op. cit. pp. 178-181). However, the pollution of the atmosphere due to sulphur dioxide, nitrous oxide and ozone from fossil fuels is estimated to be responsible for 330,000 deaths in 14 years in the UK.

Serious local pollution is caused by factories and energy sources pouring their effluent into the atmosphere or into lakes, rivers and seas. The effect of acid rain on lakes and land is determined by the buffering capacity of the geology of the region but in many cases it is severe. This hazard is now recognised, and stringent regulations have stopped many of these discharges, and then as a result the air has become cleaner, and fishes have returned to rivers and lakes. Thus in the nineteenth and early twentieth century millions of domestic coal fires produced the London smogs. The notorious example in 1952 killed about three thousand people, mostly among those already suffering from respiratory diseases. I recall that smog very well; it was easy to get lost in familiar streets, as this smog was so thick that one could not see one's feet. When one was directly underneath a street light it was just possible to see it through the gloom, and when walking along the road one had to walk in the general direction until one saw the next street light. Of course all traffic was stopped. Now that domestic coal fires are forbidden the air has become cleaner and such smogs can never occur again.

A paper issued by the European Community on energy strategy points out that nuclear power 'will make it possible for Europe to save about 330 million tonnes of carbon dioxide emissions in 2010'. 'This is equivalent to taking a hundred million cars off the road' (Nuclear Issues 23, March 2001).

The renewable energy sources emit practically no poisonous gases, except from those associated with the manufacture of the devices. The amounts of radioactivity emitted by several types of power stations are given in Table 6.5. These amounts are all very small compared with the natural background radiation, but it is nevertheless notable that coal power stations emit more radioactivity than nuclear.

Although localised pollution is usually dispersed until it is no longer noticeable, this simply means that it is spread throughout the atmosphere. Thus, as in the case of carbon dioxide, the average global pollution steadily rises. Apart from the special case of carbon dioxide, the level of the global pollution by heavy metals and other chemicals with the possible exception of some pesticides is still so low that it cannot cause appreciable harm on a global scale.

There are also some chemicals that can destroy the ozone layer in the stratosphere about thirty miles above the earth that absorbs the ultraviolet light that is harmful to some plants and insects and can cause skin cancer in unwary sunbathers. From the beginning of the twentieth century these chemicals were widely used as cleaning solvents, pest control and for fire protection. The major threat to the ozone layer came from the development of the chlorofluorocarbons (CFCs) in the nineteen thirties, and their widespread use in refrigerators

Table 6.5. Emissions of Nuclear Radiation from Various Power Sources in Man-Sieverts Per Gigawatt-Year (IAEA world average)

Coal

Nuclear

Geothermal

Peat

Gas and aerosol propellants. Two chemists, Mario J. Molina and F. Sherwood Rowland, suggested in 1974 that the CFCs could undergo photodissociation in the stratosphere, producing chlorine that destroys the ozone layer. The chlorine acts as a catalyst in the reaction dissociating the ozone, so that a single chlorine atom can destroy many thousands of ozone molecules. In addition, in 1975, the chemist Veerabhadran Ramanathan showed that the CFCs are also efficient greenhouse gases. Not surprisingly, the CFC industry responded by denying these effects.

Confirmation eventually came through the work of Joe Farman of the British Antarctic Survey, who year after year made measurements of the ozone level with his spectrophotometer. By 1984 he had records stretching back for twenty-seven years, and he found that the ozone level progressively decreased in the years from 1982 to 1984 until they were 40% below the average value. He had found a hole in the ozone layer. He also had a theory about why it occurred in the Antarctic region, for there the seasonal increase in the intensity of the ultraviolet radiation renders the stratosphere over the Antarctic especially sensitive to chlorine. Farman's results were confirmed by analysis of data obtained by NASA's satellite Nimbus.

As a result of this work, the United Nations Environment Programme initiated intensive research on the subject. In addition, many companies looked for alternatives and started to reduce the emission of CFC's and other ozone-destroying chemicals, culminating in the signing of the regulatory Montreal Protocol in 1987. This encouraged manufacturers to develop alternative environmentally-friendly products and eventually to the significant reduction of ozone-destroying chemicals. The concentration of such chemicals in the atmosphere peaked in 1994 and is now declining and should eventually lead to the closing of the ozone hole (Anderson and Madhava Sarma 2002; Christianson 1999; Lomborg 2004, pp. 273-276).

Once again it is useful to put the results of the depletion of the ozone layer in perspective by comparing estimates of the number of skin cancers with and without the ozone hole. The numbers of cases of skin cancers increased greatly during the twentieth century, but since there is a long period of latency most of the increase must be attributed to exposures some decades before the depletion of the ozone layer. These exposures to harmful ultraviolet radiation increased over previous levels due to more sunbathing, increased life span and other causes.

The depletion of the ozone layer has certainly increased the exposure, and with it the number of cancer cases. Most skin cancers are easily curable and only about 5% are the more lethal melanomas. It is estimated that of about a million cancer cases each year those attributable to the depletion of the ozone layer will peak at about 27,000 cases per year in the year 2060 in the USA. In other words, the depletion of the ozone layer is responsible for an increase in the number of cases of about 3%. Since the intensity of the ultraviolet radiation depends strongly on latitude, the increased probability of contracting skin cancer due to the depletion of the ozone layer is the same as that incurred by moving about 200 km closer to the equator.

There is increasing public recognition of the importance of reducing carbon emissions into the atmosphere. To do this industrial companies are being encouraged to assess the carbon emissions from the whole production process from obtaining the raw material and manufacturing the product, to its distribution and eventual disposal. It is planned that the product will bear a label giving its carbon emission, so that the purchaser can take this into account. If all manufacturers do this, commercial pressures will stimulate them to reduce their carbon emissions. Such an examination of the whole production process could also produce significant fuel savings (Cave 2008).

It is useful to consider the minimum reduction of carbon dioxide emissions necessary to avert a serous crisis. MacKay (2008) notes that there is some agreement that global warming must be kept below 2°C. Any higher rise could have many highly undesirable consequences. For example, the Greenland ice cap would start to melt, thus raising the sea level by about seven metres over a long period. This would be sufficient to inundate many large cities, from London to Tokyo and from New York to Calcutta. To keep the temperature below this level requires the level of carbon dioxide in the atmosphere to be kept below about 400 ppm. This in turn requires each person to limit their emissions to about one tonne of carbon dioxide each year. Since the current emissions in the United Kingdom are in the region of ten tonnes per person per year, it is evident that drastic changes to our lifestyle are necessary.

In recent years there have been several conferences on the need to tackle global warming, and most countries have agreed to reduce their emissions by 10% to 15% over the next decade. There are strong disagreements about the actual amounts and how the burden should be shared between the developed and developing nations. It is becoming increasingly clear that these arguments are increasingly unreal, as the amounts under discussion only scratch the surface of the problem. To avoid disaster, all countries must recognise that they must strive to reduce their emission to zero as soon as possible. This will require vast and costly changes in our living styles, but the results of just making small changes will be far worse.

One way to reduce carbon dioxide emissions is by means of a tax on all processes leading to such emissions, and this is already in operation in several countries. This is a useful source of revenue, but to be effective the level of taxation needs to be high enough to alter people's behaviour. At present the tax is in the region of £7 to £21 per tonne of carbon dioxide. However, assuming that doubling the price of fuel would significantly affect car usage, the tax would need to be about £500 per tonne. To discourage air travel, a figure of around £400 per tonne is needed, and other activities would require similarly high taxes. Thus much higher taxes are needed to be effective. Low taxes that do not affect people's behaviour are worse than useless, as they give the illusion of helping to solve the problem and may even be counterproductive because they encourage the idea that paying the taxes removes the damage (MacKay 2008).

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