waste or even brackish water, high CO 2 absorption capacity (1.9 tons of CO 2 for
1 ton cellulose produced), high cellulose content and high productivity even in less
fertile condition. The outer layer of different bast crops such as sun hemp, jute,
ramie, flax, and industrial hemp constitutes around one third of their weight and can
be obtained as fibrous bundles that can be used as suitable feedstocks for production
of bioethanol. Among different bast crops, industrial hemps are considered as the
most sustainable substrates for production of bioethanol (Cherney and Small 2016).
Annual production of hemp is 1 Â 10
5 tons, and it has very high 70–90% cellulosic
content by weight. Similarly, the cellulosic content for different bast crops is also
very high for flax, ramie, and jute, i.e., 60–80%, 68–76%, and 51–84%, respectively
(Paridah et al. 2011).
7.2.2.2.2 Energy Crops for Bioethanol Production
7.2.2.2.2.7 Native Grasses for Bioethanol Production
In order to maintain low-cost ethanol production, there is a need of an uninterrupted
and consistent supply of raw materials. The native grasses are one alternative which
has a short growth period, minimal cultivable land, fertilizers/pesticides, and water
requirement. These grasses also have huge carbon storage capacity due to its C4
carbon fixation ability. These plants are perennial in nature, grown mostly in warm
and temperate regions, and generate large biomass by huge carbon capture around
the year (Lewandowski et al. 2003). Thus, these native grasses have all inherent
properties to be considered as energy crops. C4 grass such as coastal bermuda grass,
napier grass, saw grass, and switch grass are potential substrates for bioethanol
production.
Miscanthus giganteus (saw grass) has carbohydrate content of 40–60% cellulose
and 20–40% hemicelluloses, making it capable of generating five to eightfold more
ethanol as compared to corn (Brosse et al. 2012). Similarly, Panicum virgatum
(switch grass) has lignocellulosic content of 37–40% cellulose, 25–29%
hemicelluloses, and 18–25% lignin. Pennisetum purpureum (napier grass) has
carbohydrate content, i.e., 40–50% cellulose and 20–40% hemicelluloses. It
produces huge biomass under limited nitrogen supply (presence of diazotrophic
nitrogen-fixing bacteria) and highly efficient CO 2 fixation and has fast-growing
capability. Cynodon dactylon (bermuda grass) has high carbohydrate content, i.e.,
40–55% of cellulose and hemicellulose accompanied with a high yield of 14.1–24.2
ton/ha (Takara and Khanal 2015). These C4 plants have high carbohydrate content
and fast-growing capability, making it a suitable substrate for ethanol generation.
Some of the C3 grasses such as Medicago sativa (alfalfa), Phalaris arundinacea
(reed canary grass), Arundo donax (giant reed), and Dactylis glomerata (cocksfoot
grass) are also reported to have high hemicellulosic content and thus used as
bioethanol-generating substrate. Njoku et al. (2013) utilized hemicellulose fraction
of cocksfoot grass for generation of ethanol with yield 89–158 mL/kg of dry
biomass.
7 Bioethanol Production: Generation-Based Comparative Status Measurements
165
1 ton cellulose produced), high cellulose content and high productivity even in less
fertile condition. The outer layer of different bast crops such as sun hemp, jute,
ramie, flax, and industrial hemp constitutes around one third of their weight and can
be obtained as fibrous bundles that can be used as suitable feedstocks for production
of bioethanol. Among different bast crops, industrial hemps are considered as the
most sustainable substrates for production of bioethanol (Cherney and Small 2016).
Annual production of hemp is 1 Â 10
5 tons, and it has very high 70–90% cellulosic
content by weight. Similarly, the cellulosic content for different bast crops is also
very high for flax, ramie, and jute, i.e., 60–80%, 68–76%, and 51–84%, respectively
(Paridah et al. 2011).
7.2.2.2.2 Energy Crops for Bioethanol Production
7.2.2.2.2.7 Native Grasses for Bioethanol Production
In order to maintain low-cost ethanol production, there is a need of an uninterrupted
and consistent supply of raw materials. The native grasses are one alternative which
has a short growth period, minimal cultivable land, fertilizers/pesticides, and water
requirement. These grasses also have huge carbon storage capacity due to its C4
carbon fixation ability. These plants are perennial in nature, grown mostly in warm
and temperate regions, and generate large biomass by huge carbon capture around
the year (Lewandowski et al. 2003). Thus, these native grasses have all inherent
properties to be considered as energy crops. C4 grass such as coastal bermuda grass,
napier grass, saw grass, and switch grass are potential substrates for bioethanol
production.
Miscanthus giganteus (saw grass) has carbohydrate content of 40–60% cellulose
and 20–40% hemicelluloses, making it capable of generating five to eightfold more
ethanol as compared to corn (Brosse et al. 2012). Similarly, Panicum virgatum
(switch grass) has lignocellulosic content of 37–40% cellulose, 25–29%
hemicelluloses, and 18–25% lignin. Pennisetum purpureum (napier grass) has
carbohydrate content, i.e., 40–50% cellulose and 20–40% hemicelluloses. It
produces huge biomass under limited nitrogen supply (presence of diazotrophic
nitrogen-fixing bacteria) and highly efficient CO 2 fixation and has fast-growing
capability. Cynodon dactylon (bermuda grass) has high carbohydrate content, i.e.,
40–55% of cellulose and hemicellulose accompanied with a high yield of 14.1–24.2
ton/ha (Takara and Khanal 2015). These C4 plants have high carbohydrate content
and fast-growing capability, making it a suitable substrate for ethanol generation.
Some of the C3 grasses such as Medicago sativa (alfalfa), Phalaris arundinacea
(reed canary grass), Arundo donax (giant reed), and Dactylis glomerata (cocksfoot
grass) are also reported to have high hemicellulosic content and thus used as
bioethanol-generating substrate. Njoku et al. (2013) utilized hemicellulose fraction
of cocksfoot grass for generation of ethanol with yield 89–158 mL/kg of dry
biomass.
7 Bioethanol Production: Generation-Based Comparative Status Measurements
165