no inverter, no generator, own a powerhouse in basement

NO GENERATOR, NO INVERTER- OWN A POWERHOUSE
24 HOURS ELECTRICITY
(FUTURE APPROACH)



Power plant in basement-

• Within a decade or two, we find ourselves living in home whose electricity coming not from a generating plant many kms away but rather from a refrigerator sized power station in basement or backyards.
• Not just homes but shops, hotels, apartment buildings & possibly factories may all be powered in same way.

This would have been possible by use of microbes based fuel cell (MFCs).

CONTENTS:

• Microbes
• Electricity
• Sources for Electricity Generation
• Limitations of Different Sources
• Microbial Fuel Cells
• Types:
- Organic Waste Water Based
- Sugar Based
- Diesel Based

• Improved Performance In MFCs:
- By Addition of Sulphate Compounds
- Using Stacked MFCs

• Limitation in Commercialization Of MFCs
• Microbes Used In MFCs
• Conversion of Mud Into Electricity
• Mechanism of Electron Transfer
• Advantages of MFCs
• Conclusion
• References


What Are Microbes?

Living organisms that are usually too small to be seen clearly with naked eyes OR with a diameter of 1mm or less.

Mainly include bacteria, viruses, yeasts &molds, algae, protozoa &helminthes.


What Is Electricity?

Flow of electrons generates electricity.

In a closed circuit, electrons flow from positive pole to negative pole & current flows in opposite direction.



Sources for Electricity Generation-

• Water
• Coal
• Wind
• Atomic power


Limitations of Different Sources-


Water-
• Depletes natural flora.
• Processed water affects crop in nearby fields.
• Not available everywhere & so transportation of current makes it cost effective.

Coal-
• Nonrenewable & exhaustible.
• Creates pollution problems.

Wind-
• Not available everywhere & all the time.

Atomic power-
• Poses health hazard.


The latest research proves that Organic Waste when acted upon by microbes generates electric current.


So MICROBIAL FUEL CELLS have been constructed. In this a particular substrate is used as fuel and particular microbial species act on this, releases electrons exocellularly and throws electrons on electrode which flows through circuit & generates electricity.






Types of Microbial Fuel Cells-

1. Organic waste water based.
2. Sugar based.
3. Diesel based.

1. Organic waste water based-

• Fuel - organic waste water
• Current - 0.2 mA
• Resistance - 1k ohm
• Fall in COD - from 1700mg/l to 50mg/l
• Identification of microbes - by denaturing gradient gel electrophoresis.

Microbial population is found to be different from that in sludge used as inoculum.On electrode surface a thin biofilm is observed in which nanobacteria like particles were present.

2. Sugar based-

• Fuel - Sugar
• Current density - 158mA/m²
• Resistance - 510 Ω
• Microbe - Rhodoferax ferriducans

Following 20 days growth, large no. of bacterial cells attached to electrode surface. Planktonic cell conc. was 140mg/l & attached biomass of electrode surface was 1180mg/l. By analyzing voltage value it was proved that planktonic cell conc. play no role in electricity production & microbial electricity generation is attributed only to biologically active cells attached to electrode.

This kind of MFC is efficient in biomass utilization & energy restoration.

3. Diesel based-

Involves anaerobic biodegradation of diesel

• Power generated - 31mW/m²
• Identification of microbes - 16S rRNA gene sequencing.

Majority of microbes more than 98% show similarity to bacteria capable of denitrification such as Citrobacter spp., Pseudomonas & Stenotrophomonas. Remaining show similarity to Shewanella, Alishewanella.
Also observed that anaerobic biodegradation of diesel was enhanced in MFC (82% removal) as compared to an anaerobically incubated control cell (31% removal) over 21 days at 30ºC




Improved Performances In MFCs-

1. By addition of sulphate compounds
2. By using stacked MFCs


1. By addition of sulphate compounds- Mechanism of electron transfer from microbes found in anaerobic sludge to anode electrode in MFCs have been investigated. In doing so, both energy accumulation & improved performance were observed as a result of addition of exogenous sulphate compounds. Treatment of anaerobic sludge by washing & centrifugation can provide samples devoid of sulphide/ sulphate. Addition of exogenous sulphate can give matched samples of S-deplete & S-replete suspensions. When these are compared in exp MFCs power output of S-deplete is only 20 % of S-replete systems.


2. By using stacked MFCs- WILLY VERSTREATE & his colleagues at Ghent University in Belgium tested fuel cells in an array of configuration :

• in series
• in parallel
• individually

They observed that connecting several MFC units in series or parallel can increase voltage and current. Six individual MFC units in stacked configuration produced-

• Max power output - 258 W/m³
• Increase voltage - 2.02 V
• Increase current - 255mA

Also observed that with time, initial microbial community decreased in diversity & Gram positive species dominant. The shift of microbial community accompanied tripling of short time power output of individual MFC from 73 W/m³ to275 W/m³ and decrease of internal ohmic resistance from 6.5Ω to 3.5Ω
Among different configurations, parallel stack was found to be most efficient.




Limitations in Commercialization of MFCs-


Mainly due to two reasons-

• Power produced is limited
• High internal ohmic resistances

MFCs are not yet commercialized but they show great promises as a power sources for environmental sensors as well as a method of waste water treatment.
Improvements in system architecture will soon result in power generation dependant on capabilities of microorganisms.

Microbes Used In MFCs-

• Among different groups of microbes, mainly bacterial communities dominate in MFC.
• These show great diversity ranging from proteobacteria including several species of Geobacter & Shewanella to communities composed of proteobacteria, firmicutes & uncharacterized clones in other MFC. But by the end of experiment when performance was at its peak – one species, Brevibacillus brevi made up majority of electron producing microbes.
• Bacteria capable of exocellular electron transfer are called as Exoelectrogens.
• Also called as Electricigens because producing electricity.



Conversion of Mud into Electricity-

Certain microbes found at bottom of ocean can transform organic matter into electrical energy. These microbes could not only be used to produce power in subsurface settings but also have implications in industry & military.





Acc to DEREK K. LOVELY, UMass microbiologist & team leader, an understanding of how microbes generate & use electrical energy may also prompt development of new technologies.

EXP. SET UP- They used water & sediment from Boston Harbor, a collection of Mason jars, sterile graphite electrode, ordinary electrical wirings to determine science behind mechanics of simple sediment battery. They added a layer of common mud to water in jars, put one graphite electrode in mud & another in overlying water. The resulting electric current was strong enough to activate a light bulb or a simple computer.

“Even using a primitive electrode made from graphite, it is possible to produce current to power basic electronic marine instruments.”

Through more refined exp. Lovely’ group found that a family of energy harvesting microbes commonly referred to as Geobacters were key to production of electric current.

Characteristics of Geobacters- As most life forms get their energy oxidizing organic compounds, Geobacters can grow in envt lacking oxygen by using iron naturally present in soil, in place of oxygen. So Geobacters can also substitute an unnatural substance such as iron for electrode.

A large no. of Geobacter species Desulphoromonas acetoxidans were found on anode end of primitive batteries. When researchers destroyed D. acetoxidans in sediment, the current stopped. In mud community of microbes break down complex organic matter into acetate. Geobacters then transfer electron from acetate to electrode generating electrical energy.

Earlier studies had shown that bacteria could produce electricity under artificial conditions in which special chemicals were added, but UMass study was first to prove that microbes living in a typical marine envt. could produce electricity under natural conditions of environment.



Advantages of MFCs-


1. NASA has believed that such microbes could be used to recycle waste on long space flights.

2. Reliable source of electricity in poor countries-

• In poor countries like Uganda, use of a cell phone or MP3 player charger can be a struggle due to difficulty in accessing electrical grid.
• More than 99% of rural households in African nation are cut off from reliable source of electricity.
• So to solve this problem, a group of MIT students has devised a microbial fuel cell that run entirely on plant waste. The students’ BioVolt MFC prototype uses cellulose munching bacteria to generate electricity.
• But main challenge for students was to develop cheap, yet efficient, device one that use non platinum catalyst.
• Though they were not willing to share exact specifications for fuel cell but they claimed that they will provide such fuel cell at cost of as little as 2 US dollars.

3. Power plant in basement-

• Within a decade or two, we find ourselves living in home whose electricity coming not from a generating plant many kms away but rather from a refrigerator sized power station in basement or backyards.
• Not just homes but shops, hotels, apartment buildings & possibly factories may all be powered in same way.

4. Companies & industrial research laboratories in Belgium, Canada, Denmark, Italy, Japan, Korea & US have fuel cell development efforts under way & few are already selling units.
Some United Tech has sold about 170 units, which are being use for generation of both heat & power.

5. MFCs are also use for treatment of wastewater and in green facilities.



Conclusion-

Today’s world is highly commercialized & every aspect of our life depends on electricity. Various sources used for electricity generation suffer certain limitations. So alternative power sources are needed-

• To reduce nation’s dependence on foreign oil.
• To reduce global warming.
• To reduce pollution problems.

So use of organic waste material as a source for electricity generation could bring about revolution in commercialized world dependant on electrical energy. But this project is in its infancy & much research work is required to be done.