Sugarcane - Bioenergy Crop Plants - page 526

In Brazil, bioethanol production from sugarcane is expected to reach 28.5 billion L in 2010/11.
Almost 70% of the ethanol produced is hydrated (5.6% water/volume) and 30% anhydrous. Hydrated
ethanol is used in automotive vehicles equipped with engines that run exclusively on ethanol or flex-
fuel vehicles. Anhydrous ethanol is mixed with gasoline. Several countries are adding ethanol to
gasoline to reduce fossil fuel consumption, increase octane rating and reduce pollution. This trend
started in Brazil in 1931 and legislation that establishes a mixture of up to 25% of ethanol in gaso-
line dates to 1966.
Nowadays almost all of the 35,000 gas stations in Brazil have a hydrated ethanol pump (E100).
Initially, cars were designed to run on either gasoline or ethanol. Now, flex-fuel cars are available
that run on any mixture of ethanol to gasoline (from 0 to 100%). In 2008, flex-fuel cars represented
82% of the new cars sold, totaling around 23% of the automotive fleet in Brazil (around 6 million
units). Motorcycle engines are already available that uses ethanol. New progress on combustion
engines is underway to allow buses to also run on ethanol. This is greatly advantageous because
the production and use of bioethanol as opposed to gasoline and diesel reduces greenhouse gas
(GHG) emissions by 90%. This has been calculated on the basis of the whole sugarcane cycle
including planting, harvesting, processing, and transporting of the fuel. And, because sugarcane is
a renewable source of energy with a rapid growth and up to six annual harvests without the need for
replanting, high dry matter yield per unit of fertilizer applied, minimal needs for pesticides—which
require great quantities of fossil fuel for their production—and high CO 2 fixing capacity, the use of
its ethanol can mitigate global warming.
The success of a biofuel crop is based on its economical and environmental advantages. To
achieve sustainability, energy crops should not require extensive use of prime agricultural lands
and they should have low-cost energy production from biomass. Basically, the crop energy output
must be more than the fossil fuel energy equivalent used for its production. Studies have shown
that the output to input ratio of sugarcane first-generation ethanol production is approximately
8-10, compared with 1.6 for maize (Goldemberg 2008). Several crops are being tested for bio-
ethanol production, which can also be produced from starch and sugars from maize, wheat, sugar
beet, cassava, and others, but they rarely reach two units of renewable energy produced relative
to each unit of fossil fuel energy used. In 2007, the production and use of bioethanol in Brazil
reduced GHG in 25.8 million t equivalents of CO 2. This corresponds to 360,000 diesel buses/year
(Goldemberg 2008).
After juice extraction, the sugarcane stalk residue (bagasse) can be burned in the sugarcane
factories for production of steam and electrical energy. Bioelectricity is the most important new
product of the sugarcane business. All mills and distilleries in Brazil are self-sufficient in electric
energy through co-generation. Approximately one third of the energy is stored in the cane juice,
one third in the bagasse, and one third in the trash. Until recently, most of the sugarcane was burned
in the fields to facilitated manual cutting, but increased pollution and decreased the energetic effi-
ciency because the straw and leaves were not used for energy generation. Presently, in the state of
São Paulo, responsible for 60% of the sugarcane production in Brazil, almost 50% of harvesting is
mechanized without burning. Regulation determines that burning should be prohibited by 2014.
This trend is spreading to other regions as well.
Bagasse is burned in highly efficient boilers (over 60 bars) that will allow for surplus energy
to be commercialized in the electric grid. In 2008, sugar and ethanol mills produced an aver-
age of 1,800 MW. With the more efficient boilers being implemented and new investments in co-
generation an estimated 11,500 MW can be produced, which is equivalent to 15% of the electricity
demanded by Brazil. Bioelectricity brings several advantages, including low environmental impact,
carbon credits, and the need for relatively small and low-risk investments. In Brazil, bioelectricity
brings an additional advantage because sugarcane harvest takes place mostly in the dry season
when hydroelectric mills are at their lowest production.
Alternatively, ethanol can be produced from bagasse and trash lignocellulose by hydrolysis of the
cell wall using enzymes, physical, and chemical treatments (Ragauskas et al. 2006). The processing