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11 Usage of Microalgae: A Sustainable Approach to Wastewater Treatment

11.4.5

Microbial Fuel Cells

Microalgae can be used for energy production by hydrolysis and fermentation of

biomolecules [39]. Bioenergy can be obtained from microalgae using microbial fuel

cells (MFCs). An MFC is a bioelectrochemical reactor containing a microorgan-

ism that can oxidize both organic and inorganic matter in the reactor generating

current. MFCs represent bioelectrochemical systems using exoelectrogenic bacteria

for the generation of electricity using wastewater. When MFCs used photosynthetic

microorganisms as a catalyst for oxidation–reduction reactions, they are known as

photo-MFCs. A microbial electrolysis cell (MEC) are another type of cell they gener-

ate hydrogen by applying an electric current on wastewater and works on the same

principle as MFCs [39]. MFCs can be used to address various problems like bioreme-

diation, wastewater treatment, and desalination. The cathode in MFCs is stored in an

environment with no oxygen where hydrogen is generated as the electron acceptor

[35, 39]. Microalgae interact with the photosynthetic bacteria in a healthy manner

and serve as electron donors and oxygen suppliers for the removal of organic matter.

The wastewater provides nutrients for the microorganisms which is broken down

into simple forms and utilized. The COD reduced by microalgae finds an important

application in the field of MFC. Studies have shown up to 90% COD removal which

makes MFC quite promising and can be scaled up commercially in future [39].

11.5

Conclusion

Although lists of benefits are offered by algae-based fuel, it is exorbitantly expen-

sive. Large amounts of energy are required for algae cultivation and harvesting.

Microalgae cultivation is the best approach for CO2 removal and the cultivation

system depends on the microalgae species, scale, and expenditure. Open ponds

were projected to be economically favorable than closed photobioreactors. HRAP

provides efficient tertiary-level wastewater treatment at a reasonable cost. Although

microalgae can be independently used for CO2 bio-fixation, biofuel production

or wastewater treatment, integration of all these processes would make the pro-

cess economical. In addition, different biomass of microalgae like carbohydrates

and lipids can be utilized for bioethanol and biodiesel production. Commercial

by-products can also be obtained from proteins, pigments, and vitamins derived from

microalgae. This technology can be sustainable technology, if the advancements

coupled with research can allow the commercialization of biofuel and wastewater

treatment.

References

1 Pham, T.-L. and Bui, M.H. (2020). Removal of nutrients from fertilizer plant

wastewater using Scenedesmus sp.: formation of bioflocculation and enhance-

ment of removal efficiency. Journal of Chemistry 2020: 1–9.