154
O. M. Darwesh et al.
Chlorella vulgaris and Spirulina platensis microalgae by electrolysis. They obtained
high process yield of 96.8%, at temperature of 25 °C without using of hazardous
sodium hydroxide or sulfuric acids and without the side reaction of saponification
which means high quality biodiesel product. Instead, in conventional esterification
and transesterification, in addition to the required high heat, acid or base as catalysts
are required, respectively, which are considered of less sustainability for overall
process.
Moreover, in magnetic nanocatalysts, it is easy to recover (by external magnetic
field), regenerate and reuse the catalyst for further production cycles. On the other
hand, Darwesh et al. (2019b) used peroxidase enzymes immobilized on magnetic NPs
as a nano-biocatalyst for bioremediation of textile wastewater dye in a reactor. They
reported more stability, reusability of the biocatalyst due to the immobilization with
the magnetic NPs as well as more bioremediation efficiency. It is could be concluded
that, application of nanocatalysts enables the sustainability of catalyst, less hazardous
waste discharges into the environment and more environmental sustainability.
4.5 Application of Biogenic NPs in Renewable Energy
Production
Energy consumption is a manifestation of life on this planet as it is required for all life
activities, and this consumption is linked to industrial development and population
growth. Unfortunately, the biggest portion of consumed energy came from the limited
carbon-based fossil fuels such as oil, coal and natural gas which in turn results in
the greenhouse gas emission and global warming. In addition, the depletion of fossil
fuels will threaten the current lifestyle through the outbreak of wars to compete
for limited fuel in addition to the disruption of many factories and power plants
around the world. Hence, the orientation towards relying on clean and renewable
energy is an important and vital issue to keep the world sustainable. Solar and wind
energy are among the cleanest and renewable energies on the planet. In addition,
there are other important sources of clean, ecofriendly and renewable energies such
as hydrothermal, marine, bio-mass and solar that are sustainable and leading to a
sustainable environment. The application of nanotechnology had a clear imprint in
improving the efficiency of production, transmission and consumption of new and
renewable energy. As a result of advances in nanotechnology, solar and microbial
fuel cells benefit from the advantages of unique properties of NPs such as titaniumbased NPs (TiO 2 ), silicon dioxide (SiO 2 ) NPs, graphene and carbon nanotubes to
efficiently produce energy (Sohail et al. 2019). It should be noted that the use of
microbes to manufacture nanomaterials related to the production of clean energy is
an environmentally friendly approach in addition to the main benefits arising from
the use of clean and sustainable energy sources.
Biofuels could be defined as solid (e.g., biochar), liquid (e.g., bioethanol,
biodiesel) or gaseous (e.g., biogas, biohydrogen) fuels that are predominantly
O. M. Darwesh et al.
Chlorella vulgaris and Spirulina platensis microalgae by electrolysis. They obtained
high process yield of 96.8%, at temperature of 25 °C without using of hazardous
sodium hydroxide or sulfuric acids and without the side reaction of saponification
which means high quality biodiesel product. Instead, in conventional esterification
and transesterification, in addition to the required high heat, acid or base as catalysts
are required, respectively, which are considered of less sustainability for overall
process.
Moreover, in magnetic nanocatalysts, it is easy to recover (by external magnetic
field), regenerate and reuse the catalyst for further production cycles. On the other
hand, Darwesh et al. (2019b) used peroxidase enzymes immobilized on magnetic NPs
as a nano-biocatalyst for bioremediation of textile wastewater dye in a reactor. They
reported more stability, reusability of the biocatalyst due to the immobilization with
the magnetic NPs as well as more bioremediation efficiency. It is could be concluded
that, application of nanocatalysts enables the sustainability of catalyst, less hazardous
waste discharges into the environment and more environmental sustainability.
4.5 Application of Biogenic NPs in Renewable Energy
Production
Energy consumption is a manifestation of life on this planet as it is required for all life
activities, and this consumption is linked to industrial development and population
growth. Unfortunately, the biggest portion of consumed energy came from the limited
carbon-based fossil fuels such as oil, coal and natural gas which in turn results in
the greenhouse gas emission and global warming. In addition, the depletion of fossil
fuels will threaten the current lifestyle through the outbreak of wars to compete
for limited fuel in addition to the disruption of many factories and power plants
around the world. Hence, the orientation towards relying on clean and renewable
energy is an important and vital issue to keep the world sustainable. Solar and wind
energy are among the cleanest and renewable energies on the planet. In addition,
there are other important sources of clean, ecofriendly and renewable energies such
as hydrothermal, marine, bio-mass and solar that are sustainable and leading to a
sustainable environment. The application of nanotechnology had a clear imprint in
improving the efficiency of production, transmission and consumption of new and
renewable energy. As a result of advances in nanotechnology, solar and microbial
fuel cells benefit from the advantages of unique properties of NPs such as titaniumbased NPs (TiO 2 ), silicon dioxide (SiO 2 ) NPs, graphene and carbon nanotubes to
efficiently produce energy (Sohail et al. 2019). It should be noted that the use of
microbes to manufacture nanomaterials related to the production of clean energy is
an environmentally friendly approach in addition to the main benefits arising from
the use of clean and sustainable energy sources.
Biofuels could be defined as solid (e.g., biochar), liquid (e.g., bioethanol,
biodiesel) or gaseous (e.g., biogas, biohydrogen) fuels that are predominantly