**3. Bio-active organisms**

fuels on combustion pollute the environment by emitting huge amount of CO<sup>2</sup>

been catching up with other bioconversion concepts in recent years.

energy or employed in the synthesis of other molecules [5, 6].

AFC is a promising technology which can capture CO<sup>2</sup>

**2. Algal fuel cell configuration**

CO<sup>2</sup>

of extensive researches during last decades.

92 Microalgal Biotechnology

sphere resulting in global climate change. The risks of over-dependence on fossil fuels can be avoided by using renewable and carbon-neutral energy sources in a large amount. The concern and awareness of the harmful impact of mineral-based fuels on the environment have pushed the research towards the production of eco-friendly energy from renewable sources. Renewable energy, which can be harvested from the sun either by photovoltaic energy or in the form of biomass energy as solar energy is considered as the mother of all energy, will play a predominant role in future. Globally, carbon neutral energy has been receiving the attention

During the eighteenth century, the novel idea of generating electric energy from biological route emerged. The potential of using microorganisms that convert organic or inorganic compounds into electrical power was studied [1]. This process occurs through metabolic activity of microorganisms at ambient pressure and temperature [2]. Microbial fuel cells are the devices capable of producing bioelectricity from different sources of substrates [3, 4]. The substrate is regarded as one of the essential biochemical factors affecting power generation in microbial fuel cells. The consideration of microbial fuel cells as a marginal scientific issue has

New designs have evolved and the operation has moved towards AFC for generating bioelectricity through the photosynthesis reaction by microalgae. Microalgae are considered as eco-friendly organisms having high photosynthetic efficiency and rapid reproduction and are also a good source of fuel with their neutral lipid content. Algae use energy from sunlight in the photosynthetic reaction in which they consume carbon dioxide to produce oxygen. The first creations of algae were cyanobacteria, the small sized blue green algae responsible for the early transformation of the earth's atmosphere. Algae play a significant role in the production of oxygen. In the current situation, there is need to reduce carbon dioxide and in

Calvin cycle. The photosynthesis reaction is considered as one of the complex biological redox reactions happening naturally and carried out by algae and plants in which they are able to use energy from the sun to produce carbohydrates and oxygen through multiple redox reactions. They also produce additional compounds during the process which may be utilized for

Generally, microalgae grow in a bioreactor or open pond where they can use the sunlight,

AFCs are electro biochemical devices which have anode and cathode compartments enclosed with a photosynthetic microorganism. Here photosynthesis is carried out and they act as electron donors producing organic metabolites. The main objective of configuring AFC is to

and nutrient. Therefore, new designs were employed for enabling the microalgae in a

this way algae convert carbon dioxide to oxygen where lights stimulate the CO<sup>2</sup>

microbial fuel cell to generate electricity with different electrode materials.

to the atmo-

fixation by

inexpensively with the help of algae.

Microalgae are one of the best bioactive metabolites for a microbial fuel cell which can mitigate CO<sup>2</sup> . The mechanism of donating an electron and accepting it is still uncertain. The understanding of the mechanism is important for improving the performances of AFCs. Some studies predicted that dumping of cells in a certain environment causes the reduction of power against oxidative stress. Researchers have explained these mechanisms by using specific inhibitors of electron transport chain in microalgae [14, 15]. Another prediction has reported that microorganisms use electrical signal for communicating and this is explained in many complex communities containing autotrophic and heterotrophic, eukaryotic and prokaryotic organisms where electrogenic microorganisms exist [16]. Many researchers have reviewed and recommended microbial fuel cells using microalgae for the right selection of the type of algal strain to maximize power production [17, 18]. The study to determine the method of screening the right strain is few in number. A recent study has made an effort for cost-effective photosynthetic microbial fuel cell design with highly reproducible electrochemical characteristics that can be used to screen algae and cyanobacteria for photosynthetic electrogenic activity. *Paulschulzia pseudovolvox* (*Chlorophyceae*) is identified as good electrogenic qualities among several cyanobacteria [19].

**5. Membrane**

The membrane is the heart of this system which is highly expensive. This results in the increase of the overall cost of AFC. Membranes act as a separator for the anode and cathode compartments. The substrate that is used in this system tends to produce electrons and protons which are passed through the membrane for the separation of specific ions. Though the membranes are used as a barrier, it has some issues. The motion of ions from the anode to cathode chamber slowly increases the protons in the anode chamber and the negatively charged ions in the

The overall performance of AFC can improve by a membrane separator having micellar porous structure separating the specific ions from anode chamber to cathode chamber. Proton exchange membrane and electron exchange membrane are the most preferred membranes due to their superior conductivity properties. But these are unsuitable for high power scale application due to their need for hydration and high cost. Some of the studies have explored the use of alternative membranes of low cost which are: cation exchange membranes such as sulfonated polyether ether ketone, sulfonated polystyrene-ethylene-butylene-polystyrene, CMI-7000 and Hyflon ion, anion exchange membranes such as AMI-7000, salt bridges and porous materials such as J-Cloth, glass fiber filters, nylon, nonwoven cloth, earthenware pot, ceramic, terracotta, compostable bags and latex glove. The use of these inexpensive mem-

The healthy growth of algae in AFC is essential for efficient power production which is influ-

ence of light and organic carbon the result of which is the production of daytime electricity depending on the organic loading rate and light irradiation. In some cases, a higher concen-

Algae and higher plants contain two major photosynthetic systems in thylakoid membrane. They are classified as photosystem I and photosystem II containing chlorophylls and carotenoid

eventually decreases the pH of the electrolyte and this pH of the algal inoculums must be

causes adverse effect on algae during the early stages of growth. The dissolved

. The optimal growth of microalgae

produced

Algal Fuel Cell

95

http://dx.doi.org/10.5772/intechopen.74285

by consuming

concentrations. A

supply [30].

in the pres-

or by diverting CO<sup>2</sup>

produced in the anionic chamber which

concentration also affects the lipid content of

cathode chamber. This results in low and high pH in anode and cathode.

branes occasionally causes difficulties like high internal resistance.

enced by growth media, nutrient supplement and CO<sup>2</sup>

the inorganic carbon in cathodic chamber and CO<sup>2</sup>

high initially to overcome. Apart from this, CO<sup>2</sup>

**7. Influence of light source**

is achieved when the cathodic chamber is bubbled with CO<sup>2</sup>

in the anodic chamber which concludes that the microalgae is able to fix CO<sup>2</sup>

microalgae. The cells produce polyunsaturated fatty acids under high CO<sup>2</sup>

6% lipid content increase was observed accompanied by a 10–15% increase in CO<sup>2</sup>

permeates through the membrane [23, 29]. The micro-algae also prefer to use CO<sup>2</sup>

**6. Influence of carbon dioxide**

tration of CO<sup>2</sup>

CO<sup>2</sup>
