Here is an interesting letter published in Nature:

Nature 445, 364 (25 January 2007) | doi:10.1038/445364c; Published
online
24 January 2007
Polluting effects of Brazil's sugar-ethanol industry

Luiz Antonio Martinelli1 and Solange Filoso

1. Centro de Energia Nuclear na Agricultura, Avenida Centenàrio
303,
13416-000, Piracicaba, SP, Brazil
2. Department of Entomology, University of Maryland, 4112 Plant
Sciences Building, College Park, Maryland, 20742-4415, USA

Sir:

As Brazilian environmental scientists, we believe that the Business
Feature "Drink the best and drive the rest"1 understates the serious
environmental and social problems associated with Brazil's sugar-cane
ethanol industry. For instance, although you say that soil erosion is
a "potentially" damaging side-effect of sugar-cane cultivation, there
is abundant scientific evidence already that environmental
degradation from soil erosion in sugar-cane fields is widespread2. In
the state of São Paulo, which is the core of the ethanol industry in
Brazil, estimated rates of soil erosion in sugar-cane fields are up
to 30 tonnes of soil per hectare per year. Moreover, despite laws to
protect the riparian buffers that prevent soil inputs to rivers and
streams, only 30% of riparian zones have been preserved in river
basins.

The burning of sugar-cane fields before manual harvesting twice a
year is another serious environmental problem related to the ethanol
industry in Brazil. Although a law passed in 2002 by the state of São
Paulo decrees that, by 2006, 30% of the sugar-cane fields with slopes
lower than 12% (called mechanizable areas) should not be burned,
farmers have been reluctant to replace cheap manual labour with more
expensive mechanized harvesting. The deadlines imposed to reduce the
burning of sugar-cane fields have been postponed several times, under
pressure by sugar-cane farmers. Thus, it is likely that smoke
pollution from sugar-cane fields will continue to be a major problem
in São Paulo and other Brazilian states for many years, leading to
further acidification of the already poor tropical soils3.
Additionally, high particulate concentrations in the atmosphere from
sugar-cane burning have been associated with a growing number of
human respiratory diseases in sugar-cane regions4, 5.

Last but not least, although the sugar-cane industry generates jobs in
Brazil, working conditions, especially for manual harvesters, are
extremely poor and often associated with causes of death. Thus —
although we agree that Brazil's ethanol industry is "able to get
better" — from an environmental and social standpoint, it is far from
being as good as you portray.

We believe that the present ethanol industry and proposals for
expansion of ethanol production in Brazil and worldwide should be
carefully evaluated, to avoid environmental and social problems far
outweighing long-term economic gains.

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References

1. Nature 444, 670–672 (2006)| Article |.
2. Sparovek, G. & Schnug, E. Soil Sci. Soc. Am. J. 65, 1479–1486
(2001). | ChemPort |
3. Krusche, A. V. et al. Environ. Pollut. 121, 389–399 (2003). |
Article | PubMed | ChemPort |
4. Arbex, M. A. et al. J. Air Waste Manag. Assoc. 50, 1745–1749
(2000).
| PubMed | ChemPort |
5. Cançado, J. E. D. et al. Environ. Health Persp. 114, 725–729
(2006).