Although not every scientist agrees, emissions of carbon dioxide from the combustion of
fossil fuels, mostly petroleum, natural gas and coal are considered to be a major factor
in causing the onset of global warming. Unacceptable rises in temperature are leading to
rising sea levels from the melting of polar ice and corresponding climate changes may
effect plant and animal life in otherwise temperate zones.
Technological advances reduce the growth in energy demand to around 1% below the rate
of economic growth, but the world’s demand for energy is expected to continue to rise
exponentially, particularly in respect to emerging economies such as China and India. What
is desired is a number of renewable sources of energy, not limited by resource depletion
(as is the case with fossil fuels) that are "clean" in that they emit little or
no so-called "greenhouse gases". Renewable sources include wind and sea current
power, but nuclear power, which is purported to meet both criteria, must be excluded, as
it does not fulfil either.
Before considering alternative sources, it is necessary to understand the size of the
problem by examining current global energy consumption. Energy units exhibit little
uniformity, but the joule can be used as a universally acceptable basis for analysis. Big
numbers have to be employed to express global energy parameters, i.e., the exajoule (joule
x 1018) and the petajoule (joule x 1015), abbreviated as EJ and PJ
respectively. The world’s energy consumption in 2003 was 409 EJ, of which fossil
fuels provided 90% as primary energy. Of this 60 EJ was in the form of electrical energy,
with only 10 EJ provided by nuclear generation.
Transport constrained to fixed guide systems, such as rail and tramways can use
electrical energy directly from current collectors, but mobile transport able to move on
roads or rough terrain uses mostly liquid fuels derived from oil. As oil reserves deplete,
liquid fuels will be synthesised increasingly from natural gas and then coal, until all
fossil fuels able to be economically extracted are exhausted.
To use electrical energy as an alternative to conventional liquid fuels for mobile
transport requires the production of hydrogen from electrolysis and its subsequent
cryogenic liquefaction for on-vehicle storage. This has an inherent energy penalty over
the derivatives of primary fuels and of course, unless the electricity used to produce the
hydrogen fuel is from a renewable and "clean" source, offers no panacea to
global warming. Assuming mobile transport requires 40% of global energy and taking into
account the energy loss in conversion, the requirement for global electrical generation
rises to 700 EJ. The problem is that electrical energy of whatever means of generation is
a poor substitute for the adaptable primary energy obtained from fossil fuels.
A typical 1200 MW nuclear power plant produces 32 PJ per annum, so to provide for 700
EJ around 20,000 nuclear power stations would have to be built. To fuel this number of
stations, around 4,600,000 tonnes/annum of uranium would be required.
Current world annual mine production totals only 36,000 tonnes of which Canada produces
10,000 tonnes and Australia around 8,000 tonnes. The balance of 30,000 tonnes required to
meet the generators’ demand for 66,000 tonnes/annum comes from inventories,
ex-weapons material, MOX and re-worked mine tailings. So primary production would have to
be increased 140-fold to match present global energy needs exclusively from nuclear power.
*
However the emerging economies of China and India are setting the pace for growth and
rising energy demand, so to meet their aspirations the initial requirement for the
building of 20,000 nuclear power stations is likely to be insufficient. In reality there
is little chance of fuelling the current modest building programme of new stations as
secondary sources of uranium are expected to be exhausted by 2012, creating a shortfall in
supply unable to be filled by additional mining, so the first desired characteristic of
sustainability is unattainable.
Then the claim for the carbon-free status of nuclear power proves to be false. Carbon
dioxide is released in every component of the nuclear fuel cycle except the actual fission
in the reactor. Fossil fuels are involved in the mining, milling and enrichment of the
ore, in the fuel can preparation, in the construction of the station and in its
decommissioning and demolition, in the handling of the spent waste and its re-processing
and in digging the hole in the rock for its deposition.
The lower the ore grade, the more energy is consumed in the fuel processing, so that
the amount of the carbon dioxide released in the fuel cycle depends on the ore grade. Only
Canada and Australia have ores of a sufficiently high grade to avoid excessive carbon
releases and to provide an adequate energy gain. At ore grades below 0.01% for
‘soft’ ores and 0.02% for ‘hard’ ores more CO2 than an
equivalent gas-fired station is released and more energy is absorbed in the cycle that is
gained in it. Ores of a grade approaching the "crossover" point such as those in
India of 0.03%, if used, risk going into negative energy gain if there are a few
"hiccups" in the cycle. **
The industry points to the presence of uranium in phosphates and seawater, but the
concentrations are so low that the energy required to extract it would exceed many times
the energy obtained from any nuclear power resulting.
Maybe the world does not need to stop all carbon dioxide emissions, but even a doubling
of nuclear generation capacity would only provide 20 EJ, i.e., 5% of world energy
consumption. There is no possibility of an extension of nuclear capacity solving to any
significant degree the problem of global warming.
It is claimed that nuclear power meets the two characteristics of sustainability and
zero or low carbon dioxide emissions and so might be able to substitute for fossil fuels
once they are exhausted and in the meantime to avoid release of some greenhouse gases. The
claims are baseless.
In conclusion, perhaps the scale of global warming has been overstated by omitting to
take into account fossil fuel depletion. A guide to the maximum amount of carbon dioxide
released from the combustion of fossil fuels can be calculated, given that they are
limited. The graph shows that if economic growth continues as
currently, the reserves of oil, gas and then most of the coal will have emptied by the end
of the century. From a knowledge of the carbon content of the three fuels, it is then
possible to work out the total amount of carbon dioxide likely to be released.
This comes out as 5 exagrams or 5,000 billion tonnes.
An earth scientist should be able to work out the likely temperature rise that the
release of this limited amount, mostly over the next 50 years, is likely to produce.
Before hampering the world with useless measures unable to reduce the eventual amount of
the release of carbon dioxide, it would be more appropriate to estimate the ultimate
consequences of today’s immoderate exploitation and exhaustion of fossil fuels.
John Busby 6 February 2005.
For a full analysis of the consequences of fossil fuel depletion visit The Busby Report.
References
* WNA Symposium 2004, Dzhakishev,
http://www.world-nuclear.org/sym/2004/pdf/dzhakishev.pdf
** Storm van Leeuwen and Smith, http://www.oprit.rug.nl/deenen/
