useful algae. Also in need of development of liquefaction and saccharification
methods with high sugar recovery rates, the identification and culturing of efficient
fermentation microbes, and low-energy input ethanol refinement approaches.
The most important thing is to acquire algae as a source, which will require
large-scale farming of promising algae species. Farming methods for the algae used
in food are quite costly, and new farming methods with lower costs will need to be
developed. Also needed are methods for harvesting algae and dedicated harvesting
vessels that reflect the characteristics of specific sea area and the structure of
farming facilities.
Because the concentration of ethanol produced from fermentation with algae is
relatively low, low-concentration alcohol solution must be isolated and enriched.
New isolation methods need to be developed that apply membrane separation to the
existing distillation approach, allowing for the separation and enrichment of
low-concentration alcohol.
Once these problems are solved, perhaps ethanol can be produced from algae for
use as a renewable energy source.
9.3 Methane Production from Algae
9.3.1 Methane Production from Algae
Several methods are currently being applied to use biomass for energy. Methods for
conversion into biofuel consist chiefly of thermochemical and biochemical conversion. For thermochemical conversion, methods such as pyrolytic gasification,
fast pyrolysis, and carbonization are used. For biochemical conversion, microorganism reactions (fermentation) are used to convert biomass into methane gas,
alcohol, or other fuels.
The fuels obtained through these conversion methods can be converted by
combustion into heat, electrical, or kinetic energy. For heat energy conversion,
boilers are sometimes used. For conversion to electrical energy, engines or turbines
with a generator are used. Because engines and turbines release high-temperature
waste gases, cogeneration systems are often used to produce electrical and heat
energy simultaneously through heat exchange with these gases. The fuels obtained
can also be used for kinetic energy in the form of vehicle fuels (Park and Li 2012).
In terms of fuel conversion technology, thermochemical conversion is typically
used when moisture content is low, and biochemical conversion is used when it is
high. Because thermochemical conversion is accompanied by high-temperature
reactions, the temperature is reduced as a result of evaporation of moisture contained in the biomass. As a consequence, the necessary reaction temperature for
conversion may not be obtained in cases where moisture content is high. Biochemical conversion, in contrast, uses the reactions of microorganisms, and conversion takes place at a temperature range where moisture does not evaporate. An
advantage of the thermochemical conversion approach is the low quantity of
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methods with high sugar recovery rates, the identification and culturing of efficient
fermentation microbes, and low-energy input ethanol refinement approaches.
The most important thing is to acquire algae as a source, which will require
large-scale farming of promising algae species. Farming methods for the algae used
in food are quite costly, and new farming methods with lower costs will need to be
developed. Also needed are methods for harvesting algae and dedicated harvesting
vessels that reflect the characteristics of specific sea area and the structure of
farming facilities.
Because the concentration of ethanol produced from fermentation with algae is
relatively low, low-concentration alcohol solution must be isolated and enriched.
New isolation methods need to be developed that apply membrane separation to the
existing distillation approach, allowing for the separation and enrichment of
low-concentration alcohol.
Once these problems are solved, perhaps ethanol can be produced from algae for
use as a renewable energy source.
9.3 Methane Production from Algae
9.3.1 Methane Production from Algae
Several methods are currently being applied to use biomass for energy. Methods for
conversion into biofuel consist chiefly of thermochemical and biochemical conversion. For thermochemical conversion, methods such as pyrolytic gasification,
fast pyrolysis, and carbonization are used. For biochemical conversion, microorganism reactions (fermentation) are used to convert biomass into methane gas,
alcohol, or other fuels.
The fuels obtained through these conversion methods can be converted by
combustion into heat, electrical, or kinetic energy. For heat energy conversion,
boilers are sometimes used. For conversion to electrical energy, engines or turbines
with a generator are used. Because engines and turbines release high-temperature
waste gases, cogeneration systems are often used to produce electrical and heat
energy simultaneously through heat exchange with these gases. The fuels obtained
can also be used for kinetic energy in the form of vehicle fuels (Park and Li 2012).
In terms of fuel conversion technology, thermochemical conversion is typically
used when moisture content is low, and biochemical conversion is used when it is
high. Because thermochemical conversion is accompanied by high-temperature
reactions, the temperature is reduced as a result of evaporation of moisture contained in the biomass. As a consequence, the necessary reaction temperature for
conversion may not be obtained in cases where moisture content is high. Biochemical conversion, in contrast, uses the reactions of microorganisms, and conversion takes place at a temperature range where moisture does not evaporate. An
advantage of the thermochemical conversion approach is the low quantity of
304
9 Marine Bioenergy Production