Ministry of Agriculture, Livestock and Food Supply - Embrapa

in the sugar & alcohol production chain, especially in the Rankine and
combined cycles10 .
Projections of the International Energy Agency indicate that the
participation of biomass in electric power generation throughout the world will
rise from 10TWh in 1995 to 27TWh by 2020.
According to FAO approximately 1,333 Mt of sugarcane were produced
in 1997, or 335 Mt (25%) of bagasse. One ton of bagasse with 50% humidity
holds 2.85 GJ of energy.
According to the National Energy Balance, the share of biomass in the
Brazilian energy matrix was 27% in 2003. Energy from sugarcane bagasse
was 12.6%; from firewood and charcoal, 11.9%; and from other sources,
2.5%. During the 1985-1992 period cogeneration already accounted for 3.6%
of the electric power produced in Brazil (WALTER, 1994).
Processing sugarcane requires huge amounts of thermal, mechanical
and electrical energy. Nevertheless, after the juice is extracted, it is possible
to burn the sugarcane bagasse11 in boilers to produce steam, which is used
to obtain three sources of energy.
In addition to the bagasse, sugarcane furnishes straw and styles,
which account for 55% of the energy accumulated in the sugar plantation.
Although most of this energy remains in the fields, it can represent up to 30%
of the total sugarcane biomass. Its maximum caloric power exceeds 15 GJ/t
and its minimum caloric power is approximately 13 GJ/t. Although it could
double the amount of energy obtained from sugarcane, all this potential is
seldom used and, in most cases, is burned in the fields.
The bagasse – 25% to 30% the weigh of the sugarcane processed –
was initially, used in the sugar mills instead of firewood to generate heat.
More recently, however, it has been used to generate steam, with the additional
possibility of being transformed into other forms of energy, such as heat,
electric power, or mechanical traction. The increased costs of electric power
and petroleum have made the use of bagasse in cogeneration very attractive.
10 In the Rankine cycle, a boiler is used in which a source of energy (sugarcane bagasse or straw)
generates steam under high pressure at a temperature above 100ºC. The steam is released by
means of mechanical systems that move machinery and transfer heat to the industrial processes or
move turbines to generate electric power. The cycle is completed when the steam returns to the
boiler to be heated again. In the combined cycle, a high-temperature gas turbine drives a generator
and the heat of the gas is transferred to the water, generating steam. The steam moves a second
generator, and both generators produce electric power.
11 Understood as the macerated sugarcane stalk with 50% humidity, a residue from the crushing
operation in the sugar mill.
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