algal biofuel

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Biofuel are the fuel of biological origin these constitute renewable from of energy.


CONT.Energy crisisBased on the current consumption of about 11.6 million tons of crude oil per day, it is expected that the entire resources can only suffice for a rather short time period.Global warming and global climate changesThe use of oil can cause the risks of the rise of greenhouse effect, which can result in all kinds of disasters to our planet Earth and its inhabitants.

BiodieselBiobutanolBiogasoline etc.


It is a biofuel consisting of monoalkyl esters that are derived from organic oils , plant or animal through the process of transesterification.



The triglycerides methanol and catalyst are placed in a controlled reaction chamber to undergo transesterification.The initial product is laced in a separator to remove the glycerin by product.The excess methane ,oils removed from the methyl ester through evaporation.

PROCESS OF MAKING BIODIESELSpecies oil content (% based on dry weight)

Algal cultivation system( are two type)Open Pond SystemPond consist of closed loop recirculation channel in which mixing and circulation are provided by paddle wheel.Depth=0.20.5Limitation=Loss of water due to evaporationUnwanted algal & microorganism growth.


Closed Photo bioreactor System(PBR)Provide a controlled environmentTubular shape & Flat shapeBiological &Physiological controlReducing contamination levelLimitation=High operating cost

Open pond system

Closed Photobioreactor System

1-Energycrisis2-Global Warming3-Incresing Industrialization 4-Heigh Cost Of Fossils Fuel

Requirement of biofuel-

ALGAE HARVESTINGThe termalgae harvestingrefers to concentration of diluted algaesuspensionuntil a thickalgae pasteis obtained.Harvesting method is based upon size and properties of algae strain.Harvesting of microalgae from algaecultivationpond or photobioreactorsemploy several techniques:FLOTATIONCENTRIFUGATIONFILTRATIONTheseprocessesare aided by cell flocculation. Itcauses the cells to become aggregated into larger clumps which are more easily filtered and/or settle more rapidly. It is done by addition of chemicalflocculants or through autoflocculation.FiltrationSuitable for larger algal species with cell diameters >70 m. For smaller algal species membrane ultrafiltration can be employed.Limitation is that biomass settles on the filter and eventually block filter pores, which makes filtration less efficient, thus increasing energy consumption.In addition membrane replacement and pump operation increase operating expenses therefore better suitable to handle smaller volumes.CentrifugationMethod of separatingalgaefrom the medium by using acentrifugeto cause the algae to settle to the bottom of a flask or tank.Quick and effective method.Limitation is very high energy consumption .Flotation It is performed using compressed air to inject air microbubbles at the bottom of the culture medium, algae adhere to the microbubbles and accumulate on the medium surface.ALGAE OIL EXTRACTIONExtraction can be broadly classified into two categories:-MECHANICAL METHODExpeller pressCHEMICAL METHODHexane Solvent MethodSoxhlet extractionSupercritical fluidExtractionEXPELLER PRESS Algae is dried .Oil content can be "pressed" out with an oil pressHEXANE SOLVENT METHOD Uses chemicals (such as hexane).Can be harmful and explosive.Cold press & hexane solvent = extract 95% of oil

SOXHLET EXTRACTION -In this method, oils from the algae are extracted through repeated washing, orpercolation, with an organic solvent such as hexane, underreflux in a special glassware.The value of this technique is that the solvent is reused for each cycle.

SUPERCRITICAL FLUID EXTRACTION CO2 is liquefied under pressure and heated to the point that it has the properties of both a liquid and gas.This liquefied fluid then acts as the solvent in extracting the oil.Can Extract almost 100% of the oils.Expensive equipment.

Sodium ethanolate is used as catalyst, ethanol is reacted with the algal oil ( the triglyceride) to produce bio-diesel & glycerol. The end products of this reaction are hencebiodiesel, sodium ethanolate and glycerol.End-mixture is separated as follows: Ether and salt water are added to the mixture and mixed well. After sometime, the entire mixture get separated into two layers, with the bottom layer containing a mixture of ether andbiodiesel. This layer is separated.Biodiesel is in turn separated from ether by a vaporizer under a high vacuum. As the ether vaporizes first, thebiodiesel will remain. The biodiesel fromalgaeis now ready for use.Oil extraction from algae (occur by two method given as below)Mechanical methodExpeller PressChemical methodHexane Solvent MethodSoxhlet Extraction Supercritical Fluid ExtractionCONCLUSIONAlgae are promising source for biodiesel production, as they can perform photosynthesis, grow in heterotrophic conditions, grow faster, do not require a special growth medium, and contain 50 % or more of their mass as oil.Carbon dioxide necessary for photosynthesis can be obtained from stationary sources of environment air pollution such as fuel combustion units, which would help to reduce emissions of greenhouse gases.Algal oil is similar to vegetable oil, the existing traditional biodiesel production technologies can be easily adjusted to use this new raw material.