schaffer at optonline.net
Tue Dec 3 07:31:32 MST 2002
Richard Wilson wrote:
> We should convert to ethanol as the main source of fuel for
> automobiles as it is cleaner than gasoline and without taxes &
> subsidy on gasoline, would only be a bit more expensive and would
> help our dieing agriculture sector.
to save Comrade Jones from a heart attack, check out the comments on
ethanol production below (4-th paragraph) ... its been some time since
i studied all these kinds of numbers, would be worth revisiting
ethanol, for example, to see if things are as bad as Rees says.
Nature 420, 267 - 268 (2002) © Macmillan Publishers Ltd.
Footprint: our impact on Earth is getting heavier
Sir - Bjorn Lomborg's comments as reported in your recent News
story (Nature 419, 656; 2002) betray ignorance of
ecological-footprint analysis (EFA). This is a method I proposed
(W. E. Rees Popul. Environ. 24, 15-46; 2002) specifically to assess
the assertions made by some economists that, because of
technological advances, the human economy is "dematerializing" or
"decoupling" from the natural world. If true, this implies that
modern society is becoming less dependent on nature, and can be
used to justify further economic growth. If false, the additional
stress likely to be imposed on the natural world will be
Certainly, no single index can represent the total human impact on
the ecosphere. However, EFA is comprehensive enough to show,
unambiguously, that the human eco-footprint on Earth is steadily
increasing. Comparative studies (such as the Worldwide Fund for
Nature's Living Planet Report 2002, criticized by Lomborg) show
that the most technologically advanced nations are the most energy-
and material-intensive and have the largest per-capita ecological
footprints. Hence, the consumer lifestyles of their average
citizens (and of the wealthy residents of the developing world) are
the least ecologically sustainable on Earth, and cannot be safely
extended to humans everywhere.
Lomborg's ignorance of eco-footprint science is illustrated by his
claim that it ignores the potential growth in the use of renewable
resources, and that if the use of such resources increases, the
2050 footprint would not be as large as projected. The fact is that
EFA is already largely based on use of renewable resources, with
the exception of the fossil-fuel (carbon sink) component. A shift
to exclusive use of renewable energy does not necessarily imply a
reduction in the eco-footprint.
Biomass fuels, for example, are likely on thermodynamic grounds
alone to demand a larger growing area than the amount of land
needed to provide the energetically equivalent amount of fossil
energy (via carbon assimilation) today. One proposed 'renewable'
resource, fuel ethanol production, is not even a net source of
energy. In the United States, 70% more energy (mostly fossil fuel)
is consumed in producing a litre of ethanol than is contained in
the product. Even without counting the energy cost of the
fermentation and distillation process, or the carbon-sink footprint
of the fossil fuel used to grow the maize feedstock, the average US
automobile would require 4.4 hectares of cropland to provide its
annual fuel requirements. (This whopping -- but only partial -- fuel
eco-footprint is about seven times the cropland needed annually to
feed one person in the United States.) To run all US cars on
ethanol would require an area of cropland equivalent to nearly the
total US land area. More generally, the United States uses 85% more
fossil energy each year than the total energy captured by all its
plant biomass over the same period. Clearly, regardless of the
efficiency of the conversion technology, there is no possibility of
renewable biomass substituting, joule for joule, for fossil fuel.
The much-touted solar alternatives may not fare much
better. Although the solar flux represents a vast flow of potential
energy, various analysts argue, from both thermodynamic principles
and empirical data, that humanity faces enormous technological
obstacles in converting this flow into the energetic equivalent of
contemporary fossil-fuel use.
In the light of such data and the implicit uncertainty about
prospects for sustainability, Lomborg's "sceptical challenge" to
the ecological footprint concept falls flat. EFA may be static, but
this does not invalidate estimates of future footprints based on
reasonable assumptions about technological development. Dynamic
modelling is just as vulnerable to implicit error in this regard.
William E. Rees
School of Community and Regional Planning, University of British
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