9.2 Producing Ethanol with Algae
As a fossil fuel, petroleum exists in limited deposits, and the carbon dioxide produced with its combustion has been identified as responsible for global warming.
More and more attention is focusing on the development of alternative energy
sources to take its place.
Nuclear power had been regarded as one major alternative source of energy.
After a 2011 mega-earthquake and tsunami in Japan resulted in an explosion at the
Fukushima Nuclear Power Plant with catastrophic consequences, many are now
calling for changes or reconsideration not only of the future construction of additional nuclear powerful plants but also the operation of existing ones (Visschers and
Siegrist 2013).
In addition to requiring members of the public to conserve energy more to
prepare for a future energy shortage, there have also been calls around the world to
make greater use of natural energy sources such as solar, water, and wind power
and increase the use of sustainable energy sources such as bioethanol from biomass.
In addition to farming crops and food resources such as soybeans, corn, sugarcane,
and sugar beets, other resources used for ethanol production to date have included
timber, hay, leaves, barley straws, and rice straws (Pimentel and Patzek 2005).
The use of corn, soybeans, sugarcane, and other crops as biofuels in Brazil, the
U.S., and Europe has led to problems with a global food shortage amid skyrocketing grain prices. This in turn has led to the recent identification of non-edible
biomass in the form of algae and lignocellulose biomass from weeds, rice straw,
and waste lumber. In the case of lignocellulose biomass, the lignin surrounding the
cellulose prevents extraction and must be removed first. Cellulose is not readily
degradable, making saccharification difficult. Because of these factors and difficulties related to chemical treatment, progress has not been made in the development of production technology (Pimentel and Patzek 2005).
In contrast, algae may be seen as a more or less unlimited source of ethanol
biomass. Though a portion of seaweeds are currently used for food, they can also be
mass-produced in the oceans (Bush and Hall 2006).
Here, “seaweeds” is understood to refer to the larger varieties of green, brown, and
red algae. While chiefly distributed in coastal regions, they are produced in seas
around the world in quantities that exceed the yields of tropical rain forest zones.
Other great advantages of algae biomass compared to the farming of land biomass for
ethanol production include the fact that it grows naturally in the vast environment of
the seas, which means that it does not compete with edible crops for farmland or
water and presents no environmental load in terms of pesticides (Percival 1979).
As an ethanol source, algae contain large amounts of sugar, including cellulose
polysaccharides, starch polysaccharides, high-molecular weight sulfate polysaccharides, alginic acid (a uronic acid compound), and sugar alcohols such as mannitol. Because algae either do not possess or have only very small quantities of the
lignin that prevents cellulose polysaccharide extraction in land biomass, they may
be seen as amenable to usage as a fuel for ethanol fermentation (Wei et al. 2013).
9.2 Producing Ethanol with Algae
299
As a fossil fuel, petroleum exists in limited deposits, and the carbon dioxide produced with its combustion has been identified as responsible for global warming.
More and more attention is focusing on the development of alternative energy
sources to take its place.
Nuclear power had been regarded as one major alternative source of energy.
After a 2011 mega-earthquake and tsunami in Japan resulted in an explosion at the
Fukushima Nuclear Power Plant with catastrophic consequences, many are now
calling for changes or reconsideration not only of the future construction of additional nuclear powerful plants but also the operation of existing ones (Visschers and
Siegrist 2013).
In addition to requiring members of the public to conserve energy more to
prepare for a future energy shortage, there have also been calls around the world to
make greater use of natural energy sources such as solar, water, and wind power
and increase the use of sustainable energy sources such as bioethanol from biomass.
In addition to farming crops and food resources such as soybeans, corn, sugarcane,
and sugar beets, other resources used for ethanol production to date have included
timber, hay, leaves, barley straws, and rice straws (Pimentel and Patzek 2005).
The use of corn, soybeans, sugarcane, and other crops as biofuels in Brazil, the
U.S., and Europe has led to problems with a global food shortage amid skyrocketing grain prices. This in turn has led to the recent identification of non-edible
biomass in the form of algae and lignocellulose biomass from weeds, rice straw,
and waste lumber. In the case of lignocellulose biomass, the lignin surrounding the
cellulose prevents extraction and must be removed first. Cellulose is not readily
degradable, making saccharification difficult. Because of these factors and difficulties related to chemical treatment, progress has not been made in the development of production technology (Pimentel and Patzek 2005).
In contrast, algae may be seen as a more or less unlimited source of ethanol
biomass. Though a portion of seaweeds are currently used for food, they can also be
mass-produced in the oceans (Bush and Hall 2006).
Here, “seaweeds” is understood to refer to the larger varieties of green, brown, and
red algae. While chiefly distributed in coastal regions, they are produced in seas
around the world in quantities that exceed the yields of tropical rain forest zones.
Other great advantages of algae biomass compared to the farming of land biomass for
ethanol production include the fact that it grows naturally in the vast environment of
the seas, which means that it does not compete with edible crops for farmland or
water and presents no environmental load in terms of pesticides (Percival 1979).
As an ethanol source, algae contain large amounts of sugar, including cellulose
polysaccharides, starch polysaccharides, high-molecular weight sulfate polysaccharides, alginic acid (a uronic acid compound), and sugar alcohols such as mannitol. Because algae either do not possess or have only very small quantities of the
lignin that prevents cellulose polysaccharide extraction in land biomass, they may
be seen as amenable to usage as a fuel for ethanol fermentation (Wei et al. 2013).
9.2 Producing Ethanol with Algae
299