Page 207 - Lignocellulosic Biomass to Liquid Biofuels

170 Lignocellulosic Biomass to Liquid Biofuels

petroleum and coal materials) utilization will lead to an energy crisis in
the near future, that is, increasing the fossil fuel consumption would result
in the rapid rise of fuel or oil prices, fast depletion of fossil fuel resources
or reserves, and change the environmental condition, say global warming,
which all consequently lead to the search for alternative strategies for
energy production or generation from other sources [2 6]. Since the sec-
ond half of the 20th century, many researchers as well as industrialists
have been continuously searching for a substitute of petroleum-based fossil
fuel sources with the development of novel, low-cost and eco-friendly,
clean, and sustainable renewable energy sources that reduce the global
GHG (greenhouse gas) emissions and also cause fulfillment of the global
energy crisis. Many renewable clean energy group sectors, such as wind,
solar, hydrothermal, and geothermal, have been mainly developed for the
production of electricity but not for transportation fuels. The liquid bio-
fuel or bio-oil generated from different kinds of solid biomass materials
are regarded as promising alternative sustainable renewable energy sectors
to fossil fuel sources [7 9]. Also, the biomass materials could assist as a
source of foodstuffs for human and higher animal consumptions, raw
materials for various developmental activities, and are utilized as energy
sectors for heating, cooking, etc. [10]. Especially, the production of bioe-
nergy from lignocellulosic biomass materials, such as barley straw, corn
cobs, stover, straw and fiber, rice straw, green bean, giant reed leaves and
stalk, wheat straw, bioenergy crops (switchgrass, Miscanthus), soybean
straw, softwood stem, sunflower stalk, and sugarcane bagasse [11,12], are
the most promising renewable resources, because they are cheap, non-
toxic, widely dispersed, highly abundant, indigenous, autoregenerating
(via photosynthesis), eco-friendly natural resources, which all can be used
to replace or act as an alternative to fossil fuels and also reduce the GHGs
during the combustion process [13 16]. Furthermore, lignocellulosic bio-
mass materials comprise three major constituents, namely, cellulose
(30% 50%), hemicellulose (15% 35%), and lignin (10% 20%); they
may contain xylan, arabinan, galactan, glucuronic, acetic, ferulic acid,
coumaric acid, etc., which are the potential substrates for the production
of bio-oils, say ethanol and butanol [17 19].
Hence, many challenges are upgrading to generate alternative liquid
transportation bio-oil or biofuel, which are more superior to bioethanol,
but have similar fuel properties with those of petroleum-based gasoline.
Among the various liquid biofuels, a four-carbon alcohol of biobutanol
(C 4 H 9 OH), when the butanol or 1-butanol or butyl alcohol is generated