World Energy Outlook 2006

according to the conversion process, the scale of production and region, and
the type of crop used.
Biofuels production and use can have other important environmental effects.
In particular, major changes in the use of farm land could profoundly affect
local and regional ecosystems, with both positive and negative implications for
flora and fauna. These effects depend on what land is used, which crops are
grown for biofuels and farming techniques:
� Conventional agricultural crops, such as rapeseed, corn and cereals used
to produce first-generation biofuels generally require high-quality farm
land and substantial amounts of fertilizer and chemical pesticides. The
production of such crops for biofuels would increase global competition
for arable land, increase the pressure to turn more land over to crops,
including rain forests, and drive up food and fodder prices.
� The environmental impact of sugar-cane cultivation, as practiced in
Brazil, is generally smaller. Experience has shown that soil quality
productivity can be maintained, over decades of production, by recycling
the nutrients in the waste from the sugar mill and distillery back to the
fields. However, using more bagasse as an energy input to ethanol
production would reduce the amount of nutrients recycled. Most sugarcane
production in Brazil and other countries depends on rainfall and
does not require irrigation.
� Palm oil is produced on plantations, typically on poor soils, but without
the need for extensive use of fertilizers and pesticides. However, increases
in the size of plantations can lead to the loss of rain forests, especially in
southeast Asia.
Perennial ligno-cellulosic crops, such as eucalyptus, poplar or willow trees, can
be harvested several times at intervals of three to seven years. Grasses can be
harvested each year. Management is far less intensive compared to annual crops
and fossil-energy inputs are generally low, with typical energy input/output
ratios of between 1:10 and 1:20. Ligno-cellulosic crops can be grown on poorquality
land, requiring less fertilizer. In addition, most nutrients remain on the
land because, for deciduous trees, the harvest takes place after the nutrient-rich
leaves have dropped. As a result, soil carbon and quality tends to increase over
time, especially when compared to conventional farming. Switching to the
second-generation ligno-cellulosic ethanol technology, currently under
development, could, therefore, greatly reduce the environmental drawbacks of
biofuels production.
Chapter 14 - The Outlook for Biofuels
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