Page 89 - Biofuels for a More Sustainable Future

80 Biofuels for a More Sustainable Future

a diesel or gasoline additive, it provides better fuel properties (Ndaba et al.,
2015). In addition, butanol can be used as a solvent for paints and varnishes,
or as a raw material for production of other chemical inputs, such as n-butyl
acrylate, also an important monomer for production of polymers and emul-
sions used in paints. Other uses include n-butyl acetate as solvent, as well as
glycol, plasticizers, extraction of active pharmaceutical and cosmetics pro-
duction (Natalense and Zouain, 2013; Mascal, 2012). Nowadays, butanol
production is accomplished by three different processes: Acetone-butanol-
ethanol (ABE) fermentation, acetaldehyde condensation, and hydroformy-
lation (OXO) synthesis, the latter being the most employed process in the
world. The ABE process uses carbohydrate-rich raw materials, such as
molasses, which in recent years have been increasing in price, and being a
source of food, this can interfere with food safety. Limitations of the
ABE process include its low yield, high fermentation times, and problems
related to product inhibition. However, it is possible to use renewable
raw materials that do not compete with food crops, such as residual crop
biomass (Singh and Singh, 2011).
Table 4.1 presents a summary of the main steps utilized in the biochem-
ical route for production of biofuels.

Table 4.1 Summary of the processes contemplated in the biochemical route
Step Objective Characteristics
Pretreatment Disrupt the vegetal tissue, Instantaneous compressions and
making the cellulose decompressions by means of
polymers accessible steam injection at high
pressures in acid environment
Hydrolysis Convert cellulose and Enzymes act in the rupture of
hemicellulose polymers chemical bonds, breaking the
into fermentable sugars polymers into glucose
molecules
Separation of Separates the hydrolyzed Takes place in centrifuges that
solids solution from components separate the sugared solution,
that interfere with fibrous parts, and other
fermentation components that interfere in
fermentation. Enables the
recovery of the lignin
Fermentation Convert sugar into the Under adequate conditions,
desired products, through bacteria metabolize sugar and
the action of bacteria the products are obtained
Distillation Separates and purifies the Due to the difference in the
and final products for final volatility of the fermented
dehydration destination solution, the most volatile
compounds evaporate