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5 Biomass Decomposition and Nanotechnology
when treated at supercritical conditions (>22.1 MPa and > 374 °C). In these conditions, the oxygen in the water behaves as an oxidant. When the supercritical water
is allowed to react with the biomass (a carbonaceous material) it will oxidize the
carbon of the biomass resulting in the generation of CO. After further oxidation,
the CO results in the formation of CO 2 . When carbon of the biomass is utilized,
the H 2 and O 2 of both biomass and water were liberated. This method appears very
promising but is very costly and is only suitable for biomass with high moisture
content [17, 18].
Fermentation is common biological process for the generation of hydrogen from
biomass. There are two types of fermentation for the evolution of hydrogen from
biomass, i.e., the light fermentation and the dark fermentation. The light fermentation
utilizes photoheterotrophic microorganisms whereas the dark fermentation makes
use of the anaerobic microbes for the fermentation of the biomass. In the process of
fermentation, the first step is hydrolysis (either enzymatic or acidic) of the biomass to
produce the concentrated solution of sugars which is later on fermented to hydrogen,
oxygen, and volatile fatty acids with anaerobic organisms. The organic acids present
in the concentrate are additionally fermented by the photoheterotrophic bacteria such
as Rhodobacter sp. and liberate H 2 and CO 2 . When light and dark fermentation are
used collectively greater amount of H 2 is generated from the carbohydrates [19]. The
chemical reaction for the conversion of carbohydrate to H 2 by fermentation can be
given as.
C 6 H 12 O 6 + 2H 2 O 2 → 2CH 3 COOH + 2CO 2 + 4H 2
C 6 H 12 O 6 → CH 3 (CH 2 ) 2 · COOH + 2CO 2 + 2H 2
Biomass is also converted to H 2 via photosynthesis process. Different phototropic
microbes like cyanobacteria, green bacteria, and purple bacteria and numerous algae
are utilized for the generation of hydrogen from biomass in the presence of sunlight.
Green algae and other microbes absorb the sunlight and produce electrons, and the
photosystem sends these ferredoxin electrons.
Biological water gas shift reaction is yet another biochemical process in which
the particular microbes like Rubrivivax gelatinosus are used for the conversion of the
biomass to sustainable hydrogen. These microbes are capable of carrying out water
gas shift reactions with biomass at optimized temperature and pressure. The general
reaction of the process can be given as [20].
Biomass → H 2 O + CO → CO 2 + H
Both the thermochemical and the biological processes of biomass conversion
for the generation of sustainable H 2 involve the extensive use of nanotechnology.
Many studies have used the nanotechnology for the thermochemical conversion of
the algal mass to the sustainable hydrogen [21]. Similarly, various studies of biomass
5 Biomass Decomposition and Nanotechnology
when treated at supercritical conditions (>22.1 MPa and > 374 °C). In these conditions, the oxygen in the water behaves as an oxidant. When the supercritical water
is allowed to react with the biomass (a carbonaceous material) it will oxidize the
carbon of the biomass resulting in the generation of CO. After further oxidation,
the CO results in the formation of CO 2 . When carbon of the biomass is utilized,
the H 2 and O 2 of both biomass and water were liberated. This method appears very
promising but is very costly and is only suitable for biomass with high moisture
content [17, 18].
Fermentation is common biological process for the generation of hydrogen from
biomass. There are two types of fermentation for the evolution of hydrogen from
biomass, i.e., the light fermentation and the dark fermentation. The light fermentation
utilizes photoheterotrophic microorganisms whereas the dark fermentation makes
use of the anaerobic microbes for the fermentation of the biomass. In the process of
fermentation, the first step is hydrolysis (either enzymatic or acidic) of the biomass to
produce the concentrated solution of sugars which is later on fermented to hydrogen,
oxygen, and volatile fatty acids with anaerobic organisms. The organic acids present
in the concentrate are additionally fermented by the photoheterotrophic bacteria such
as Rhodobacter sp. and liberate H 2 and CO 2 . When light and dark fermentation are
used collectively greater amount of H 2 is generated from the carbohydrates [19]. The
chemical reaction for the conversion of carbohydrate to H 2 by fermentation can be
given as.
C 6 H 12 O 6 + 2H 2 O 2 → 2CH 3 COOH + 2CO 2 + 4H 2
C 6 H 12 O 6 → CH 3 (CH 2 ) 2 · COOH + 2CO 2 + 2H 2
Biomass is also converted to H 2 via photosynthesis process. Different phototropic
microbes like cyanobacteria, green bacteria, and purple bacteria and numerous algae
are utilized for the generation of hydrogen from biomass in the presence of sunlight.
Green algae and other microbes absorb the sunlight and produce electrons, and the
photosystem sends these ferredoxin electrons.
Biological water gas shift reaction is yet another biochemical process in which
the particular microbes like Rubrivivax gelatinosus are used for the conversion of the
biomass to sustainable hydrogen. These microbes are capable of carrying out water
gas shift reactions with biomass at optimized temperature and pressure. The general
reaction of the process can be given as [20].
Biomass → H 2 O + CO → CO 2 + H
Both the thermochemical and the biological processes of biomass conversion
for the generation of sustainable H 2 involve the extensive use of nanotechnology.
Many studies have used the nanotechnology for the thermochemical conversion of
the algal mass to the sustainable hydrogen [21]. Similarly, various studies of biomass