metal ions contained in the seaweed extract become separated during hydrolysis
under low pH conditions, and an absorbent can be used at this time to remove them.
Improved metal solubilization has been reported in non-algae energy crops such as
willows, sugar beets, and grass with a two-stage process at a pH 4. Once heavy
metals are removed, organic acid drainage can undergo methane fermentation in the
second fermentation tank.
Nkemka and Murto subjected algae to organic acid fermentation and removed
heavy metals using a porous cryogel from a polyacrylamide base to which iminiodiacetic acid had been introduced as a ligand. The results reported respective
reductions of 79, 59, 70, and 41% for cadmium, copper, nickel, and zinc, with no
problems for methane fermentation (Singh and Olsen 2011).
9.4 Biohydrogen Production
In addition to polluting the atmosphere, the use of fossil fuels also leads to global
warming through the accumulation of carbon dioxide emissions. It is a situation that
urgently calls for development of new energy materials that do not cause atmospheric pollution (Levin et al. 2004).
By unit weight, hydrogen’s exothermic energy is three times higher than that of
petroleum. In addition to potentially offering a superior energy source, it does not
carry a risk of atmospheric pollution from its combustion. This, along with the
possibility of conversion to electrical power and use as both a solid and liquid fuel,
has resulted in it drawing attention as a key fuel source for the future. Because
hydrogen is not produced as a simple substance anywhere on Earth, however, other
energy sources must be used to produce it artificially.
Approaches considered for the production of hydrogen include such physical
and chemical methods as water electrolysis and pyrolysis. All of these methods
require large amounts of energy for hydrogen production. For this reason, solar
energy is a beneficial source for hydrogen production. The use of bioprocesses
involving photosynthetic bacteria capable of efficiently exploiting solar energy is
now drawing attention as one of the most promising potential approaches.
The use of photosynthetic bacteria for hydrogen production offers many
advantages: the production system is quite simple, the resulting gases can easily be
separated into hydrogen and carbon dioxide, and renewable biomass or waste can
be used as a source. Once efficient hydrogen production systems using photosynthetic bacteria become established, they may well become the chief energy production systems of the future.
Photosynthetic bacteria are typically prokaryotes that survive under anaerobic
conditions through exposure to sunlight. They exist throughout the soil and
hydrosphere and perform photosynthesis and nitrogen fixing through the use of
solar energy and suitable electron donors. They possess chlorophores and bacterial
chlorophyll to perform photosynthesis, as well as large amounts of carotenoids as
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9 Marine Bioenergy Production
under low pH conditions, and an absorbent can be used at this time to remove them.
Improved metal solubilization has been reported in non-algae energy crops such as
willows, sugar beets, and grass with a two-stage process at a pH 4. Once heavy
metals are removed, organic acid drainage can undergo methane fermentation in the
second fermentation tank.
Nkemka and Murto subjected algae to organic acid fermentation and removed
heavy metals using a porous cryogel from a polyacrylamide base to which iminiodiacetic acid had been introduced as a ligand. The results reported respective
reductions of 79, 59, 70, and 41% for cadmium, copper, nickel, and zinc, with no
problems for methane fermentation (Singh and Olsen 2011).
9.4 Biohydrogen Production
In addition to polluting the atmosphere, the use of fossil fuels also leads to global
warming through the accumulation of carbon dioxide emissions. It is a situation that
urgently calls for development of new energy materials that do not cause atmospheric pollution (Levin et al. 2004).
By unit weight, hydrogen’s exothermic energy is three times higher than that of
petroleum. In addition to potentially offering a superior energy source, it does not
carry a risk of atmospheric pollution from its combustion. This, along with the
possibility of conversion to electrical power and use as both a solid and liquid fuel,
has resulted in it drawing attention as a key fuel source for the future. Because
hydrogen is not produced as a simple substance anywhere on Earth, however, other
energy sources must be used to produce it artificially.
Approaches considered for the production of hydrogen include such physical
and chemical methods as water electrolysis and pyrolysis. All of these methods
require large amounts of energy for hydrogen production. For this reason, solar
energy is a beneficial source for hydrogen production. The use of bioprocesses
involving photosynthetic bacteria capable of efficiently exploiting solar energy is
now drawing attention as one of the most promising potential approaches.
The use of photosynthetic bacteria for hydrogen production offers many
advantages: the production system is quite simple, the resulting gases can easily be
separated into hydrogen and carbon dioxide, and renewable biomass or waste can
be used as a source. Once efficient hydrogen production systems using photosynthetic bacteria become established, they may well become the chief energy production systems of the future.
Photosynthetic bacteria are typically prokaryotes that survive under anaerobic
conditions through exposure to sunlight. They exist throughout the soil and
hydrosphere and perform photosynthesis and nitrogen fixing through the use of
solar energy and suitable electron donors. They possess chlorophores and bacterial
chlorophyll to perform photosynthesis, as well as large amounts of carotenoids as
314
9 Marine Bioenergy Production