option for production of bioethanol (Ban-Koffi and Han 1990; Rodriguez et al. 2010;
Upadhyay et al. 2010).
7.2.1.3 Limitations of 1G Feedstocks
The 1G bioethanol generated from food crops is the most developed technology
providing relief in GHG emission; however, it has its limitation which arises due to
concern associated with food security and availability of cultivable land and can also
lead to breakage of food chain due to non-availability and soaring prices of food
crops. This claim may be supported by the work done by Shikida et al. (2014) where
they concluded an interesting point that the food crops used by the USA, Brazil,
China, India, and the Netherlands for bioethanol generation can feed up to 200 million people starving in their own nation. Similarly, Rulli et al. (2016) evaluated that
the amount of food crops used for production of 1 Terajoule of 1G bioethanol can be
used to feed 110 people. The growth of food crops for bioethanol production can
compete with 3% global water requirement for food production (Agência Nacional
doPetróleo 2015). Therefore, based on the above observation, there is an urgent need
to revisit the potential feedstocks for future ethanol generation.
7.2.2 Second-Generation (2G) Feedstock for Bioethanol Production
The food versus fuel, food-fuel-land-water nexus, and environmental impacts of
large-scale 1G bioethanol have led to a search for an alternative. 2G feedstock-based
bioethanol from nonfood lignocellulosic feedstocks are considered as a feasible
option because lignocellulosic biomass is abundant all over the world which can
be used without competing with land, water, and food requirement of animal kind.
Annually, global production of plant biomass is around 200 Â 10
9 ton per year, of
which around 8 Â 10
9
–20 Â 10
9 can be used for generation of biofuel such as
bioethanol, biogas, and bioelectricity (Kuhad and Singh 1993; Saini et al. 2015). It
can even mitigate the problem of pollution which is usually generated due to burning
of these lignocellulosic wastes. Overall lignocellulosic feedstock-based biorefineries
are the need of the hour for both rural and urban areas as it can provide energy
security, mitigate environmental concern, promote agriculture, provide employment
opportunities, and save foreign exchange (earlier used to procure petroleum) and
have large-scale socioeconomic impact (Zafar 2018). Different lignocellulosic biomass used for 2G bioethanol production can be divided into several groups such as
woody biomass, i.e., forest residues, or non-woody biomass, i.e., agricultural
residues, energy crops, aquatic plants, and municipal waste. These various
biomasses are discussed below.
7.2.2.1 Woody Biomass for Bioethanol Production
Forest biomass can be collectively considered as woody biomass which mainly
includes hardwood and softwoods along with forest residues such as dead leaves,
dead branches, sawdust, woodchips, and pruning and bark thinning residues. The
USA has forest cover of around 310 million hectares and generates around 370 million tons of woody biomass per year (Robert et al. 2005). Softwood trees are the
162
B. Kumar et al.
Upadhyay et al. 2010).
7.2.1.3 Limitations of 1G Feedstocks
The 1G bioethanol generated from food crops is the most developed technology
providing relief in GHG emission; however, it has its limitation which arises due to
concern associated with food security and availability of cultivable land and can also
lead to breakage of food chain due to non-availability and soaring prices of food
crops. This claim may be supported by the work done by Shikida et al. (2014) where
they concluded an interesting point that the food crops used by the USA, Brazil,
China, India, and the Netherlands for bioethanol generation can feed up to 200 million people starving in their own nation. Similarly, Rulli et al. (2016) evaluated that
the amount of food crops used for production of 1 Terajoule of 1G bioethanol can be
used to feed 110 people. The growth of food crops for bioethanol production can
compete with 3% global water requirement for food production (Agência Nacional
doPetróleo 2015). Therefore, based on the above observation, there is an urgent need
to revisit the potential feedstocks for future ethanol generation.
7.2.2 Second-Generation (2G) Feedstock for Bioethanol Production
The food versus fuel, food-fuel-land-water nexus, and environmental impacts of
large-scale 1G bioethanol have led to a search for an alternative. 2G feedstock-based
bioethanol from nonfood lignocellulosic feedstocks are considered as a feasible
option because lignocellulosic biomass is abundant all over the world which can
be used without competing with land, water, and food requirement of animal kind.
Annually, global production of plant biomass is around 200 Â 10
9 ton per year, of
which around 8 Â 10
9
–20 Â 10
9 can be used for generation of biofuel such as
bioethanol, biogas, and bioelectricity (Kuhad and Singh 1993; Saini et al. 2015). It
can even mitigate the problem of pollution which is usually generated due to burning
of these lignocellulosic wastes. Overall lignocellulosic feedstock-based biorefineries
are the need of the hour for both rural and urban areas as it can provide energy
security, mitigate environmental concern, promote agriculture, provide employment
opportunities, and save foreign exchange (earlier used to procure petroleum) and
have large-scale socioeconomic impact (Zafar 2018). Different lignocellulosic biomass used for 2G bioethanol production can be divided into several groups such as
woody biomass, i.e., forest residues, or non-woody biomass, i.e., agricultural
residues, energy crops, aquatic plants, and municipal waste. These various
biomasses are discussed below.
7.2.2.1 Woody Biomass for Bioethanol Production
Forest biomass can be collectively considered as woody biomass which mainly
includes hardwood and softwoods along with forest residues such as dead leaves,
dead branches, sawdust, woodchips, and pruning and bark thinning residues. The
USA has forest cover of around 310 million hectares and generates around 370 million tons of woody biomass per year (Robert et al. 2005). Softwood trees are the
162
B. Kumar et al.