Abstract Ethanol production from sugar cane crops uses significant amount of water in the
agricultural and industrial processing phases. Most of the sugar cane plantations in Brazil
rely on natural irrigation complemented by partial fertiirrigation, carried out mainly to
manage water wastes, limiting their production to regions where reasonable rainfall index
occurs. Sugar cane processing to ethanol uses water collected mainly from surface water
flows and, in few cases, from underground natural reservoirs for many different activities and it become contaminated with organic and inorganic pollutants. Water availability is not a problem now or in the midterm in a water rich country like
Brazil, except in some specific regions where the amount of rainfall is not the most
recommendable for sugar cane growth. Nevertheless, due the increasing demand for ethanol and the high prices paid for it sugar cane crops tend to expand to regions where
natural irrigation needs to be complemented with artificial water spray. On the other hand
water pollution caused by application of fertilizers and agrochemicals, by soil erosion, by
cane washing, by fermentation, by distillation, by the energy producing units installed in
the mills and by other minor sources of waste water is a major concern due the large size
of such agroindustrial activity. The paper describes agricultural and industrial activities
involved in ethanol production trying to quantify the amount of potential pollutants that
are sources of water contamination and provides description of measures commonly used
to mitigate such contamination and the ones used to clean waste water. Waste water quality returned to soil and to surface water flows is regulated by the government and
such regulations are properly described and discussed. Suggestions on how to improve
the quality of waste water above the present level imposed by regulation are also
discussed. In particular, the main source of water pollution, stillage, is examined in detail
as potential source of energy and other products while its intensity of contamination is
reduced.