4.1
Introduction
Human population shows an increasing trend and it is projected to increase to 8.6
billion in 2030 (United Nations 2017). The increasing numbers of the human
population had caused a high demand for energy especially for transportation and
industrial activities. For more than two centuries after petroleum was found, now it
supplies 90% of world energy (Chew and Bhatia 2008). Unfortunately, the petroleum is non-renewable resource and utilization of petroleum had caused the negative
consequences to the environment including direct impact to the global warming due
to the release of greenhouse gases. Besides, due to its unrenewable resource, the
world also faces the insecure energy source due to the depletion of fossil fuels
reserves (Adams et al. 2013). Therefore, the alternative energy is highlighted in these
few decades, as scientific community is continuously reporting and exploring the
possible alternative energy source to overcome this major problem.
“Biobutanol, a C4 compound, is construed as an alternative fuel of biological
origin to gasoline due to its high energy density (29.2 MJ/L) and octane number of
87” (Shah and Venkatramanan 2019). Biobutanol is one of the promising alternative
energy with the estimated fuel market around $247 billion by 2020 (Green 2011). As
compared to other bioenergy, biobutanol has lower vapour pressure, less volatile and
explosive, less hygroscopic, easily mixes with gasoline, and can be transported in
existing pipeline (García et al. 2011). Apart from that, biobutanol can reduce
hydrocarbon emissions by 95%; and oxides of nitrogen by 37% (Bellido et al.
2014). Interestingly biobutanol can be produced through acetone–butanol–ethanol
(ABE) fermentation which has been produced for several decades after World War
II. Recently, researchers are focusing on ABE fermentation using lignocellulosic
biomass as substrate. The lignocellulosic biomass is cheap, abundant, and readily
available that can be obtained from most agricultural and forestry industry. The
utilization of lignocellulosic biomass will be feasible in the future as several studies
reported positive aspects of using feedstocks such as whey permeate (Setlhaku et al.
2013), corn fibre (Guo et al. 2013), wood pulp (Lu et al. 2013), and other agricultural
wastes for biobutanol production, besides reducing air pollution from burning of
wastes.
4.2
Biobutanol
Biobutanol is an alcohol produced through acetone–butanol–ethanol (ABE) fermentation by Clostridia spp. The biobutanol properties depend on their four-carbon
structure, either in linear or branched form. Biobutanol produced through fermentation is normally a straight-chained n-butanol, also known as 1-butanol, where the
OH group attached to the terminal carbon (Mascal 2012). The other type of linear
form of biobutanol is 2-butanol where the internal carbon is attached by hydroxyl
group (ÀOH) (Fig. 4.1). Butanol with 4-carbon structure is more complex alcohol
compared to methanol and ethanol that only has 1 and 2-carbon structure, respectively (Ranjan and Moholkar 2012).
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N. H. Alias et al.
Introduction
Human population shows an increasing trend and it is projected to increase to 8.6
billion in 2030 (United Nations 2017). The increasing numbers of the human
population had caused a high demand for energy especially for transportation and
industrial activities. For more than two centuries after petroleum was found, now it
supplies 90% of world energy (Chew and Bhatia 2008). Unfortunately, the petroleum is non-renewable resource and utilization of petroleum had caused the negative
consequences to the environment including direct impact to the global warming due
to the release of greenhouse gases. Besides, due to its unrenewable resource, the
world also faces the insecure energy source due to the depletion of fossil fuels
reserves (Adams et al. 2013). Therefore, the alternative energy is highlighted in these
few decades, as scientific community is continuously reporting and exploring the
possible alternative energy source to overcome this major problem.
“Biobutanol, a C4 compound, is construed as an alternative fuel of biological
origin to gasoline due to its high energy density (29.2 MJ/L) and octane number of
87” (Shah and Venkatramanan 2019). Biobutanol is one of the promising alternative
energy with the estimated fuel market around $247 billion by 2020 (Green 2011). As
compared to other bioenergy, biobutanol has lower vapour pressure, less volatile and
explosive, less hygroscopic, easily mixes with gasoline, and can be transported in
existing pipeline (García et al. 2011). Apart from that, biobutanol can reduce
hydrocarbon emissions by 95%; and oxides of nitrogen by 37% (Bellido et al.
2014). Interestingly biobutanol can be produced through acetone–butanol–ethanol
(ABE) fermentation which has been produced for several decades after World War
II. Recently, researchers are focusing on ABE fermentation using lignocellulosic
biomass as substrate. The lignocellulosic biomass is cheap, abundant, and readily
available that can be obtained from most agricultural and forestry industry. The
utilization of lignocellulosic biomass will be feasible in the future as several studies
reported positive aspects of using feedstocks such as whey permeate (Setlhaku et al.
2013), corn fibre (Guo et al. 2013), wood pulp (Lu et al. 2013), and other agricultural
wastes for biobutanol production, besides reducing air pollution from burning of
wastes.
4.2
Biobutanol
Biobutanol is an alcohol produced through acetone–butanol–ethanol (ABE) fermentation by Clostridia spp. The biobutanol properties depend on their four-carbon
structure, either in linear or branched form. Biobutanol produced through fermentation is normally a straight-chained n-butanol, also known as 1-butanol, where the
OH group attached to the terminal carbon (Mascal 2012). The other type of linear
form of biobutanol is 2-butanol where the internal carbon is attached by hydroxyl
group (ÀOH) (Fig. 4.1). Butanol with 4-carbon structure is more complex alcohol
compared to methanol and ethanol that only has 1 and 2-carbon structure, respectively (Ranjan and Moholkar 2012).
68
N. H. Alias et al.