240
Another source of biomass is microalgae and macroalgae (seaweed) as a feedstock
for bioenergy but is limited due to its relatively low dry matter content. So it is
difficult to evaluate the sustainability and economic competitiveness of algal
biomass [3].
Even though the potentials of biomass can be evaluated, the question remains as
to how effectively this potential can be utilized? Factors like economic and
environmental impact have to be taken into account while evaluating the utilization
of biomass potential. Typically, USD 3–4/GJ is considered as a threshold value to
compare it with fossil fuel price. Higher fossil fuel price and government incentives
in favor of bioenergy can certainly make it more sustainable [3].
The land for agriculture and for bioenergy crops will compete with each other,
and preference will be given to agriculture in the countries with an agriculturalbased economy, like India. Additionally, the land will be constrained by
environmental and logistical factors. The modern and efficient methods of
agriculture can free part of the land for bioenergy crops. It is apparent that the first
generation of food crops will contribute in a major way compared to secondgeneration energy crops. The selection of conversion technology is chosen on the
basis of feedstock availability and suitability. The various available technologies are
elaborated in the following sections. A huge estimate of ten billion tons of dry
biomass is produced annually, which is equivalent to 10% of the global energy
demand. This biomass could generate energy equivalent to two billion tons of
standard coal [5].
1.2 Components of Lignocellulosic Biomass
The biomass is available at a low cost, and there are no competing interests between
lignocellulosic biomass and food source. The three basic components of
lignocellulosic biomass are (1) hemicellulose consisting of five-carbon sugar
polymers (20–35%), (2) cellulose consisting of six carbon glucose polymers
(35–50%), and (3) lignin consisting of aromatic compound polymers (10–25%).
Hemicellulose is easy to hydrolyze and can be converted at mild operating conditions
due to the low degree of polymerization. Cellulose is a straight-chain polymer and
can be depolymerized into glucose, which is further decomposed into useful
chemicals and fuels. The processing of cellulose and hemicelluloses involves similar
reactions but yields different products. Lignin is an amorphous polymer and has
aromatic functionality. The structure of hemicellulose and lignin varies from
biomass to biomass. The decomposition behavior of each of these components is
different from each other and depends on temperature, heating rate, and
contamination. Hemicellulose and lignin can affect the degradation of cellulose but
will not hinder each other’s process. As a rule of thumb, cellulose leads to bio-oil
formation, and lignin leads to bio-char formation. Also, higher volatile matter leads
to bio-oil and syngas formation, and high fixed carbon leads to bio-char formation.
R. Bhoi et al.
Another source of biomass is microalgae and macroalgae (seaweed) as a feedstock
for bioenergy but is limited due to its relatively low dry matter content. So it is
difficult to evaluate the sustainability and economic competitiveness of algal
biomass [3].
Even though the potentials of biomass can be evaluated, the question remains as
to how effectively this potential can be utilized? Factors like economic and
environmental impact have to be taken into account while evaluating the utilization
of biomass potential. Typically, USD 3–4/GJ is considered as a threshold value to
compare it with fossil fuel price. Higher fossil fuel price and government incentives
in favor of bioenergy can certainly make it more sustainable [3].
The land for agriculture and for bioenergy crops will compete with each other,
and preference will be given to agriculture in the countries with an agriculturalbased economy, like India. Additionally, the land will be constrained by
environmental and logistical factors. The modern and efficient methods of
agriculture can free part of the land for bioenergy crops. It is apparent that the first
generation of food crops will contribute in a major way compared to secondgeneration energy crops. The selection of conversion technology is chosen on the
basis of feedstock availability and suitability. The various available technologies are
elaborated in the following sections. A huge estimate of ten billion tons of dry
biomass is produced annually, which is equivalent to 10% of the global energy
demand. This biomass could generate energy equivalent to two billion tons of
standard coal [5].
1.2 Components of Lignocellulosic Biomass
The biomass is available at a low cost, and there are no competing interests between
lignocellulosic biomass and food source. The three basic components of
lignocellulosic biomass are (1) hemicellulose consisting of five-carbon sugar
polymers (20–35%), (2) cellulose consisting of six carbon glucose polymers
(35–50%), and (3) lignin consisting of aromatic compound polymers (10–25%).
Hemicellulose is easy to hydrolyze and can be converted at mild operating conditions
due to the low degree of polymerization. Cellulose is a straight-chain polymer and
can be depolymerized into glucose, which is further decomposed into useful
chemicals and fuels. The processing of cellulose and hemicelluloses involves similar
reactions but yields different products. Lignin is an amorphous polymer and has
aromatic functionality. The structure of hemicellulose and lignin varies from
biomass to biomass. The decomposition behavior of each of these components is
different from each other and depends on temperature, heating rate, and
contamination. Hemicellulose and lignin can affect the degradation of cellulose but
will not hinder each other’s process. As a rule of thumb, cellulose leads to bio-oil
formation, and lignin leads to bio-char formation. Also, higher volatile matter leads
to bio-oil and syngas formation, and high fixed carbon leads to bio-char formation.
R. Bhoi et al.