166
I. A. Sanusi et al.
Alternatively, second-generation biofuels consist of non-food crops as substrate,
commonly lignocellulosic materials which include rice bran, sawdust, potato waste,
corncob, bagasse and sugarcane leaves (Gueuguim-Kana et al. 2012; Baeyens et al.
2015; Sebayang et al. 2017; Sewsynker-Sukai and Gueguim-Kana 2018; Chohan
et al. 2020). And, the third-generation biofuels use various types of microalgal
biomass as feedstock for the production of biofuels (Sekoai et al. 2019). In the
recent time, second- and third-generation biofuels have gained interest as advanced
energy sources that could be harnessed from waste materials such as potato peels,
cassava peels, sugarcane leaves, bagasse and corn cobs (Khawla et al. 2014; Sekoai
et al. 2019). These wastes are abundantly available via agricultural activities (Lateef
et al. 2008; Adeoye et al. 2015; Elegbede and Lateef 2018).
Currently, the bio-energy market is expanding (Renewable Fuels Association
2018). For instance, the global biodiesel production is expanding with an estimated
annual increase of 7.3%, to a total of 54.8 billion USD by 2025, while, the production
of bioethanol is projected to have an annual growth of 3–7% (Sekoai et al. 2019).
The global bioethanol production was estimated at around 100 billion litres in 2017
and is envisaged to double by 2027 (Sekoai et al. 2019). The International Energy
Agency (IEA) predicts that biofuels production is expected to increase 15% over the
next five years, reaching 165 billion litres.
The most commonly researched biofuels attracting global attention include
bioethanol, biodiesel, biohydrogen and biogas. Particularly, bioethanol from lignocellulosic feedstock. The production of lignocellulosic-based bioethanol involves
four phases. These include pretreatment, hydrolysis, fermentation and distillation
processes (Deniz et al. 2015; Kim et al. 2016; Sewsynker-Sukai and Gueguim-Kana
2018; Moodley and Gueguim-Kana 2019). Bioethanol has been characterised as an
environmentally friendly, efficient fuel with higher oxygen content and higher octane
number. In the same vein, fermentative biohydrogen production has unlimited potential, as its production is commonly based on the use of wastes generated from the
food, municipal and industrial sectors (Zhao et al. 2013). Biohydrogen is particularly remarkable as a fuel source for the near future, due to its high energy yield
(Zhang and Shen 2007; Han et al. 2011; Gueguim-Kana et al. 2013). Additionally,
the combustion of hydrogen produces water as its major end-product (Zhang and
Shen 2007; Zhao et al. 2013). Biodiesel production using microalgae, animal and
vegetable oils represents another potential fuel source. Biodiesel has similar combustion properties to petroleum-based diesel and therefore can be used in current diesel
engines (Ma and Hanna 1999). In addition, it is less toxic, renewable and accounts
for lower carbon emissions compared to traditional diesel (Schenk et al. 2008).
Despite the merits associated with microbial biofuel production processes from
lignocellulosic biomass, microalgae biomass and industrial wastewaters, several
challenges plague its application at large scale. Major limitations of biofuel production may include (1) high cost and energy requirement, (2) lack of a suitable substrate
that can be utilized by the microbes and (3) low product yield (Aruwajoye et al. 2017;
Sewsynker-Sukai and Gueguim-Kana 2018). In an attempt to overcome these challenges, several bioprocess optimization strategies are being investigated such as more
cost-effective substrates, low-cost pretreatment procedures, low energy input and the
I. A. Sanusi et al.
Alternatively, second-generation biofuels consist of non-food crops as substrate,
commonly lignocellulosic materials which include rice bran, sawdust, potato waste,
corncob, bagasse and sugarcane leaves (Gueuguim-Kana et al. 2012; Baeyens et al.
2015; Sebayang et al. 2017; Sewsynker-Sukai and Gueguim-Kana 2018; Chohan
et al. 2020). And, the third-generation biofuels use various types of microalgal
biomass as feedstock for the production of biofuels (Sekoai et al. 2019). In the
recent time, second- and third-generation biofuels have gained interest as advanced
energy sources that could be harnessed from waste materials such as potato peels,
cassava peels, sugarcane leaves, bagasse and corn cobs (Khawla et al. 2014; Sekoai
et al. 2019). These wastes are abundantly available via agricultural activities (Lateef
et al. 2008; Adeoye et al. 2015; Elegbede and Lateef 2018).
Currently, the bio-energy market is expanding (Renewable Fuels Association
2018). For instance, the global biodiesel production is expanding with an estimated
annual increase of 7.3%, to a total of 54.8 billion USD by 2025, while, the production
of bioethanol is projected to have an annual growth of 3–7% (Sekoai et al. 2019).
The global bioethanol production was estimated at around 100 billion litres in 2017
and is envisaged to double by 2027 (Sekoai et al. 2019). The International Energy
Agency (IEA) predicts that biofuels production is expected to increase 15% over the
next five years, reaching 165 billion litres.
The most commonly researched biofuels attracting global attention include
bioethanol, biodiesel, biohydrogen and biogas. Particularly, bioethanol from lignocellulosic feedstock. The production of lignocellulosic-based bioethanol involves
four phases. These include pretreatment, hydrolysis, fermentation and distillation
processes (Deniz et al. 2015; Kim et al. 2016; Sewsynker-Sukai and Gueguim-Kana
2018; Moodley and Gueguim-Kana 2019). Bioethanol has been characterised as an
environmentally friendly, efficient fuel with higher oxygen content and higher octane
number. In the same vein, fermentative biohydrogen production has unlimited potential, as its production is commonly based on the use of wastes generated from the
food, municipal and industrial sectors (Zhao et al. 2013). Biohydrogen is particularly remarkable as a fuel source for the near future, due to its high energy yield
(Zhang and Shen 2007; Han et al. 2011; Gueguim-Kana et al. 2013). Additionally,
the combustion of hydrogen produces water as its major end-product (Zhang and
Shen 2007; Zhao et al. 2013). Biodiesel production using microalgae, animal and
vegetable oils represents another potential fuel source. Biodiesel has similar combustion properties to petroleum-based diesel and therefore can be used in current diesel
engines (Ma and Hanna 1999). In addition, it is less toxic, renewable and accounts
for lower carbon emissions compared to traditional diesel (Schenk et al. 2008).
Despite the merits associated with microbial biofuel production processes from
lignocellulosic biomass, microalgae biomass and industrial wastewaters, several
challenges plague its application at large scale. Major limitations of biofuel production may include (1) high cost and energy requirement, (2) lack of a suitable substrate
that can be utilized by the microbes and (3) low product yield (Aruwajoye et al. 2017;
Sewsynker-Sukai and Gueguim-Kana 2018). In an attempt to overcome these challenges, several bioprocess optimization strategies are being investigated such as more
cost-effective substrates, low-cost pretreatment procedures, low energy input and the