Energy and EnviroFiciency
global warming impacts (the latter on an avoided-cost basis), ac-
cidents (except those of very low frequency and potentially very
high impact, for which no methodology of quantifying the costs has
yet been evolved) and energy security. There were some issues that
were – at least in the opinion of the ExternE team – not external costs,
such as impacts on employment and the depletion of non-renewable
natural resources, and which were consequently not included. What
this makes apparent is that:
• The estimation of external costs is not a trivial exercise, and
• In evaluating the impacts, baseline and dose response are critical
Local studies
One of the earliest studies was that of Dutkiewicz and de Villiers [3],
who estimated a cost of the order of 1 c/kWh in 1994 Rand. van Horen
(1996) [4] estimated between 5 and 8 c/kWh, also in 1994 Rand. Unfor-
tunately, his study suffered from a disastrous arithmetical error – in
calculating the impact, he employed the wrong set of data, with the
result that the costs were overstated by a large factor. Spalding-Fecher
and Matibe (1999) [5] estimated that external costs were between 1
and 9 c/kWh in 1999 Rand. Interestingly, they assessed the health
benefits of electrification at between -0.1 and -1,4 c/kWh, and the
pollution and health effects at between 0,5 and 0,9 c/kWh. However,
climate change impacts were large, with costs between 1 and 9,8 c/
kWh, and therefore dominated the overall externalities. Recently,
Riekert and Koch [1] have attempted to estimate the external costs
of generating power by coal-fired plant. They found a wide range,
between 0,1 and 6,8 c/kWh, for health impacts fromair pollution alone.
One reason for the difference from earlier studies is the effect of
inflation, and Riekert and Koch cited the earlier study of Tophil and
Pouris [6] who inflation-accounted the earlier studies to a common
2006 base date. Thus Spalding-Fecher and Matibe’s estimate of
external costs was 0,4 – 2,7 USc/kWh in 2006 money, for all damage
including health impacts, whereas Riekert and Koch focussed only
on health impacts.
Riekert and Koch’s study was not without problems. For instance,
they assumed that they could use data on PM10 emissions from
Kendal power station, but Kendal is only equipped with electrostatic
precipitators, and Kusile will employ high-temperature baghouses
[7], which will reduce the emissions by a factor of at least 10. They
assumed a range of stack heights from 150 to 310 m, but managed
to include the actual height of Kusile’s stacks, 220 m. They presented
data on As, Cr(VI), Pb and Ni in their Table 8, but this table was not
referenced in the text in any way, and there was no indication of the
source of the data. It is suspected that they employed some relation-
ship to the PM10 which, as already noted, is itself in error.
In any event, arsenic is effectively absent from South African
coal – indeed, a recent review [8] concluded that:
‘In Africa, arsenic contamination is most remarkable for its general
absence.’ Similarly, the source of the Cr(VI), Pb and Ni in Riekert and
Koch’s Table 8 does not appear to have a solid base. Finally, there is
a feature of Riekert and Koch’s analysis that must be questioned. In
general, they followed the methodology employed in ExternE, How-
ever, when they came to consider the dose response, they employed
a single model. The expected outcomes are given by Sakulniyomporn
et al (2011:3467) and Thomas and Scorgie (2006:2.16), based on the
assumption of zero-threshold linear ERFs.’
Zero-threshold linear exposure
Zero-threshold linear exposure response is relatively widespread in
epidemiological circles. However, its scientific validity has been seri-
ously questioned. It entered epidemiological thinking via radiation
exposure. A major driver for its acceptance was the simplification
that it allowed – the dose accumulated over any given period such
as a year could readily be calculated. The US National Academy of
Sciences has concluded that: ‘The preponderance of information
indicates that there will be some risk, even at low doses.’ [9]
However, there is debate over this matter even as regards ra-
diation. In France, the Academy of Sciences rejected the linear no-
threshold model, preferring a threshold for any response to a dose
of radiation [10]. The Society of Health Physicists states [11]:
‘There is substantial and convincing scientific evidence for health
risks following high-dose exposures. However, below 50 -100 mSv
(which includes occupational and environmental exposures), risks of
health effects are either too small to be observed or are nonexistent’.
When considering the health impacts of other agents such as pol-
lutants, the evidence for a zero-threshold linear response is equivocal.
Consider, for example, the question of exposure to sulphur dioxide,
and one million people being exposed to an additional 1 ppb due
to a coal-fired power station. According to the zero-threshold linear
response, that is the equivalent of one person being exposed to one
million times 1 ppb, or 1 000 ppm, 0,1%, which would be fatal within
an hour. So the impact of 1 ppb SO
2
above background is assumed
to be one death per million exposed. Is this reasonable?
Consideration of the part played by sulphur in nature makes it
seem most unlikely. Most plants contain around 0,25% S, and sul-
phur is a fertiliser with a potency similar to that of potassium. Under
natural circumstances, plants that die recycle their sulphur for use by
the next generation. However, harvesting a crop for food will remove
the sulphur, and the essential element will be removed from the field.
In former times, it was the practice to allow fields to lie fallow for a
period after a few harvests, in order to allow the sulphur and other
nutrient levels to be restored.
It transpires that, in the tropical and temperate zones of the world,
all rain contains quite a lot of sulphur, either as dissolved SO
2
or as
sulphite/sulphate. The annual flux is about 10 – 20 kgS/ha, somewhat
higher closer to the sea. But plants are clever - if there is insufficient
in the ground, they can always scavenge some directly from the air
[12]. This is one reason why the fertility seems to be so good near
volcanoes; and there can be insufficient sulphur in both ground and
air. Interestingly, the decision to use flue-gas desulphurisation in
Britain led to poor wheat in Western Europe 13:
‘Deficiency of sulphur (S) has been recognised as a limiting fac-
tor for crop production in many regions in the world. In particular,
incidence of S deficiency has increasingly been reported in Brassica
Electricity+Control
December ‘13
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