Energy production from microalgae represents a 3rd coevals of biofuel with a batch of potencies because of its advantage over first and 2nd coevals biofuels which have sustainabililty issues such as their competition for land and H2O and menace to nutrient security. However, bring forthing energy from these cells has yet to make commercial application as a consequence of the demand to detect engineerings that can do them cost-competitive and minimise the complexness associated with such coevals. For the first clip, “ a individual phase procedure ” which will affect utilizing NyexA®100, an adsorbent, to retrieve ( crop ) microalgae cells from a dilute stock and subsequent electrochemical regeneration of the adsorbent with the purpose of interrupting the cells is considered in this undertaking. It is expected that such cell break will non merely extract lipoids but will besides minimise the cost, high energy strength and the troubles inherent in other known two-stage procedures which normally require either farther desiccation of microalgal biomass or add-on of chemicals or a combination of both methods.
2.2.1 Quest for Sustainable Energy
The International Energy Agency ( 2010 ) reported that in 2008 dodo fuel accounted for about 81.3 per cent of universe entire primary energy supply and this high quality in the planetary energy mix will go on undisputed in the foreseeable hereafter. However, the sum of CO2 emanations from fossil fuels chiefly through burning is 96.4 per centum of universe CO2 emanations by fuel use ( IEA ) .
With the concern of the impacts of these emanations on the clime coupled with the security of supply as a consequence of the finite nature of dodo fuel, planetary society is at hamlets ; how can the demands of the lifting population for increasing energy supply be met while minimising the footmarks of such addition on the environment? Renewable energy from biomass is one of the extenuation options to supply sustainable energy in which security of supply can be guaranteed and emanations of anthropogenetic nursery gases to the ambiance can be kept at a sensible degree in order to cut down the negative effects of clime alteration ( IPCC, 2007 ) .
2.2.2 Microalgae Biofuel as an Option
Microalgae represent a big and diverse group of unicellular photo- and heterotrophic beings which have attracted much international attending in recent old ages as a consequence of the of import natural merchandises they produce, their ability to rectify wastewaters and for their possible as energy harvests ( Greenwell et al 2010 ) . Microalgae accumulate lipoids such as triacylglycerols ( TAG ) and depending on the sort of species ; make so either of course or under stress conditions such as high visible radiation or alimentary famishment ( USDOE, 2010 ) . Lipids along with other valuable merchandises from the microalgae cell are possible biofuel or biofuel precursors which therefore makes apprehension of the metabolic tracts and processes that generate them a important research country in order to progress biofuels production ( USDOE, 2010 ) . Though non yet produced at commercial graduated table, it is believed that renewable energy from microalgae has the possible to replace liquid fuel from fossil fuel without the sustainable contentions other beginnings of biomass fuel have generated ( Brennan and Owende 2010 ) .
2.2.3 Present Methods of Microalgae Biofuel Production ; Challenges and Prospects
Production of lipoids from microalgal cells requires the undermentioned: ( 1 ) cultivation of the microalgal biomass ; ( 2 ) harvest/recovery of the biomass from a comparatively dilute stock ; ( 3 ) extraction of the lipoids from the biomass ; and ( 4 ) purification of the petroleum infusion ( Grima et al 2003 ) . The costs of reaping microalgal biomass which by and large requires one or more solid-liquid separation stairss is a ambitious stage of the algal biomass production procedure accounting for up to 20-30 % of the entire cost of production ( Greenwell et al 2010 ; Brennan and Owende 2010 ) . The first challenge is to concentrate cells from comparatively dilute solutions and the cardinal harvest home and dewatering operations presently used are flocculation, deposit in gravitation field, centrifugation, floatation and filtration ( Greenwell et al 2010 ; Brennan and Owende 2010 ) . To expeditiously pull out the lipoids or other valuable merchandises, a 2nd phase is normally needed in which the concentrated biomass cells are ruptured either through mechanical or chemical methods or a combination of both methods ( Greenwell et al 2010, Brennan and Owende 2010 ) . The mechanical break of cells which is preferred as it offers a methodological analysis that avoids farther chemical taint of the algal readying while continuing most of the functionality of the stuff within the cell includes the usage of high-pressure homogenisers, ultrasounds, autoclaving and bead Millss ( Greenwell et al 2010 ; Brennan and Owende 2010 ; USDOE 2010 ) . Chemical methods involve the usage of organic dissolver mixtures such as hexane/ethanol ; usage of organic dissolvers at high force per unit area and temperatures above their boiling point ; usage of H2O at temperatures merely below its critical temperature and force per unit area high plenty to keep the liquid province ; and use of supercritical fluid ( Greenwell et al 2010 ; USDOE 2010 ) .
As discussed above, the harvest home of microalgal biomass and extraction of lipids/metabolites normally involves two phases. However, because the harvested microalgal biomass slurry is perishable and must be processed quickly after crop ; desiccation or drying is normally used to widen the viability depending on the concluding merchandise required ( Brennan and Owende 2010 ) . Likewise, the usage of mechanical break increases the cost of production as optimal metabolites extraction can merely be achieved when the microalgal biomass is dried ( Grima et al 2003 ) .Apart from increasing the costs of production, desiccating or drying is linked to a hazard of material loss during motion of microalgal biomass ( Brennan and Owende 2010 ) . A disadvantage of utilizing dissolvers is that it can do denaturing of cellular stuffs which finally affects the quality of biofuel oil produced ( Greenwell et al 2010 ) . In add-on, the usage of dissolvers at a big graduated table requires extra costs due to the really high criterion of works design standards because of the hazard of fire and detonation jeopardies ( Greenwell et al 2010 ) . Hence, there is still necessitate for farther research to cut down the costs, minimise the procedure energy strength and complexness associated with utilizing present methods in harvest home of microalgal biomass and extraction of lipoids ( Grima et al 2003 ; Greenwell et Al 2010 ; USDOE 2010 ) .
2.2.4 Our Proposed Methodology
The method we intend to research on is “ a individual phase extraction procedure ” which is aimed at developing an efficient lipid extraction procedure from a harvested microalgal biomass. It is an application of an surface assimilation procedure and electrochemical regeneration of an adsorbent ( NyexA®100 is the adsorbent in this instance ) that had been successfully used in the H2O industry ( Brown et al 2004a ; Brown et al 2004b ) .
18.104.22.168 Adsorption Procedure
It is a mass transportation procedure of roll uping stuffs ( adsorbate ) in solution ( liquid stage ) on a suited solid stage referred to as the adsorbent ( Metcalf and Eddy, 2003 ) . The demand for a better quality of treated effluent wastewater has led to the usage of this procedure where in most instances activated C is the adsorbent. The features and concentration of adsorbate and the temperature determines the sum of adsorbate taken up by the adsorbent ( Metcalf and Eddy, 2003 ) . To set up the adsorbent capacity of the adsorbent to take up measure of adsorbate, an surface assimilation isotherm is developed and prepared for the adsorbate/adsorbent system by exposing a given sum of adsorbate in a known volume of liquid to changing measures of adsorbent ( Metcalf and Eddy, 2003 ) . The adsorptive stage concentration is so determined utilizing equation ( 1 ) which are so utilised to develop surface assimilation isotherms ( Metcalf and Eddy, 2003 ) .
Where = adsorptive stage concentration after equilibrium, mg adsorbate/g adsorbent ; = initial concentration of adsorbate, mg/L ; = concluding equilibrium concentration of adsorbate after surface assimilation has occurred, mg/L ; = volume of liquid, L ; = mass of adsorbent, g.
Freundlich, Langmuir, and Brunauer, Emmet, and Teller ( BET ) isotherms are developed equations frequently used to depict experimental isotherm informations.
22.214.171.124 Electrochemical Regeneration
Regeneration implies a procedure used to retrieve the adsorbent capacity of the “ dog-tired ” adsorbent ( Metcalf and Eddy, 2003 ) . For case, instead than dispose dog-tired activated C by landfill or incineration, regeneration is the most commercially feasible and environmentally acceptable option ( Brown et al 2004a ) . Electrochemical regeneration was developed as a effect of the demand to minimise energy strength, high cost and loss of stuff associated with other widely known methods of regeneration ( Brown et al 2004a ; Brown et al 2004b ) . It involves the regeneration of laden adsorbent inside an electrolytic cell which consequence into desorption and/or devastation of the adsorbed organic affair ; thereby reconstructing the adsorbent capacity of the adsorbent ( Brown et al 2004a ) . However, the restriction of electrochemical regeneration of activated Cs is that it requires long surface assimilation and regeneration periods because the rate of surface assimilation and desorption of organics from activated Cs is frequently governed by intra-particle diffusion ( Brown et al 2004b ) .
This is an alternate adsorbent stuff developed to take the restrictions inherent in the electrochemical regeneration of activated Cs. NyexA®100, a graphite embolism compound, is a low cost, highly-conducting carbon-based adsorptive stuff consisting of non-porous atoms with no internal surface country ( Brown et al 2004a ) . Though its low surface country gives rise to a low capacity adsorbent, other belongingss such as ( 1 ) speedy surface assimilation rate ; ( 2 ) ability to accomplish low discharge concentrations ; ( 3 ) its high electrical conduction ; and ( 4 ) improved surface assimilation efficiency after electrochemical regeneration makes it a cost effectual and efficient adsorptive stuff in the removal/ intervention of contaminations such as atrazine, chlorinated wastewaters and organic dye ( Brown et al 2004a ; Brown et al 2004b ) .
Hypothesis and Aims of Proposed Undertaking
The overall purpose of this undertaking is to develop an efficient procedure for microalgal biomass recovery and lipid extraction using the surface assimilation procedure and electrochemical regeneration of the adsorbent which has been successfully applied in the waste H2O industry. It is expected that when NyexA®100, an adsorbent, is assorted with a dilute stock of microalgal cells, the latter will roll up on the surface of the adsorbent, thereby reaping the cells from the dilute stock. It is believed that subsequent electrochemical regeneration of the adsorbent can take to oxidization of the adsorbed microalgal biomass and which can therefore do the break of the microalgae cells taking to let go of of lipoids while the staying biomass sinks to the underside of the electrochemical bed which so makes the recovery of the extracted lipoids easier. To verify the hardiness of our proposed method, different microalgal cells will be explored. Hence, the aims of this undertaking are to ;
Evaluate and develop surface assimilation isotherms for microalgae cells/NyexA®100 systems.
Measure the effectivity of NyexA®100 for the surface assimilation ( reaping ) of microalgae cells.
Measure the measure and quality of the lipoids produced.
Evaluate different microalgal species in order to place the species that give the optimal lipoids yield utilizing the proposed methodological analysis.
Measure the optimal conditions to accomplish high lipoids extraction from microalgal biomass.
Carry out a life rhythm appraisal of the proposed and conventional methods.
Programme and Methodology
The coinage that will be ab initio investigated is Chlamydomonas reinhardtii because it can be cultivated easy in the research lab ( Hu et al 2008 ) . This coinage and other microalgae species to be investigated will be cultivated and their growing monitored at the Faculty of Life Sciences because its research installations are designed and adapted for such cultivation. Before the surface assimilation procedure starts, the harvest home of microalgae cells will be evaluated through supervising the growing of the cells in footings of prohibitionist cell weight and lipid content ( Kim et al 2005 ) . This will be achieved by mensurating the optical denseness ( O.D ) of the civilization utilizing a spectrometer and the O.D is plotted against figure of yearss of cultivation. Reaping can be done when the O.D remains comparatively changeless for 1 or 2 yearss before decease of the cells start ( Kim et al 2005 ) . This is to guarantee that harvest home is carried out when microalgae cells can give the maximal harvest output ( Kim et al 2005 ) .
Once the harvest home clip is estimated, a batch surface assimilation experiment will be carried out whereby a known dosage of the NyexA®100 will be added and assorted with a dilute solution of the microalgal cells for the intent of reaping the microalgae cells. At regular intervals, samples will be taken and spectroscopically analysed to mensurate the rate of surface assimilation ( reaping ) of the microalgal cells by NyexA®100. From this, the clip required to accomplish equilibrium can be determined and will enable us to understand the surface assimilation dynamicss.
Consequently, surface assimilation surveies will be investigated by adding assorted known weights of adsorbent to a dilute solution of the microalgal cells which will be assorted for the clip measured to accomplish equilibrium. Using the equation ( 1 ) stated above, surface assimilation isotherms can be evaluated and developed for the Chlamydomonas reinhardtii/NyexA®100 system. Outcome from these experiments can help us to measure the effectivity of NyexA®100 to reap microalgal biomass.
An electrochemical regeneration of the adsorbent will so be achieved by puting a mixture of the filtered, wet adsorbent and NaCl in the anode compartment of a batch electrochemical cell. A direct current will be applied to renew the adsorbent which in bend can take to the oxidization of the adsorbed microalgal biomass. It is expected that this procedure will interrupt the microalgal cells taking to let go of of lipoids. The volume of entire lipid released will be measured utilizing the modified Bligh and Dyer method. The latter, a comparatively speedy dissolver extraction method, involves quantifying the entire lipoid released utilizing a mixture of trichloromethane, methyl alcohol and H2O. ( Bligh and Dyer, 1959 ) . The result from this phase will enable us to measure the feasibleness of pull outing lipoids from microalgal cells utilizing this method.
Because NyexA®100 has a low adsorbing capacity ( Brown et al 2004a ) , the procedure may merely be commercially feasible and competitory with other known procedures for pull outing lipoids from microalgal biomass if the adsorbent is capable of being cheaply regenerated many times and can still pull out lipoids. Hence, regenerated NyexA®100, without any farther intervention, will be used to reap more microalgal biomass and more lipoids can be extracted following the process described above. The public presentation of the adsorbent, clip required to perchance accomplish 100 % regeneration, regeneration rhythms within which the adsorbent is still effectual and the entire measure lipoids extracted will be evaluated at this phase. A conventional method which involves reaping by centrifugation and pull outing lipoids from harvested biomass by sonification method ( the application of ultrasound ) will besides be carried out ( USDOE, 2010 ) . Results obtained will so be compared with consequences of our proposed method in order to verify whether the proposed method is more effectual and efficient.
It has been reported that the sum of lipoids extracted is a map of the type of procedure employed and on the sort of harvested microalgae coinage ( Kim et al 2005 ) . Consequently, it will be sensible to measure different microalgal species in order to place the species that gives the optimal lipoids yield utilizing proposed methodological analysis. Other microalgal species that will be assessed include Chlorella vulgaris, Dunaliella and Nannochloropsis oculata. Each of them has different physiology and lipid accretion features. For case, Dunaliella and Nannochloropsis oculata are marine species which are really high lipoid bring forthing species but unlike the former, the latter has a really thick cell wall ( Sheehan et al 2008 ) ; hence, their breakage belongingss coupled with their growing in salt H2O will be interesting to analyze for our proposed methodological analysis.
The regeneration of the adsorbent in the anodal compartment of the electrochemical cell implies that electrolysis of H2O is likely to be a important side reaction bring forthing H ions ( Brown et al 2004a ; Brown et al 2004b ) . The deduction of this may be that at lower pH, the public presentation of the adsorbent may be hampered. It has been shown from earlier plants that acidic/alkalinity feature of microalgae cells affect the easiness of their recovery because of course microalgae cells have negative charges on their surface which tends to maintain them in suspension ( Greenwell et al 2010 ) ; hence an probe of the effectivity of the adsorbent to retrieve microalgal biomass under acidic/basic status will be carried out. Kim et Al ( 2005 ) reported that add-on of NaCl enhances the recovery of certain microalgae species with gas cyst by floatation method, as a consequence, we will transport out an probe of how NaCl affects the public presentation of our procedure since the latter is used as an electrolyte in the electrochemical regeneration of the adsorbent which is so used to accomplish extra lipid extraction. The result at this phase will enable us understand the optimal conditions to accomplish high lipoids yield from microalgae cells utilizing our proposed methodological analysis. Besides, depending on the results of the experiments carried out above, farther probes may be required to determine the hardiness of our proposed method.
Last, a life rhythm appraisal of the proposed and conventional methods will be carried out to find the environmental impacts of these methods in the recovery of microalgae biomass and lipids extraction. The CCaLC tool will be employed in this respect to mensurate the C footprinting of these methods and to place chances for procedure betterment.
Adsorption isotherms for Chlamydomonas reinhardtii/NyexA®100 system.
A study on our proposed method to reap C.reinhardtii and extract lipoids.
Adsorption isotherms for other microalgal species/NyexA®100 systems.
A study on our proposed method to reap other microalgal species and pull out their lipoids.
An LCA study on our proposed and conventional methods.
A concluding study for Supervisor ‘s reappraisal.
Dissertation study for entry.
Each study will besides include presentation of experimental informations and consequences.
2.4.3 Programme Management
The pupil transporting out the research will be largely based in the research lab as the undertaking mostly involves transporting out experiment. Due to the interdisciplinary nature of the undertaking, he will be working from research labs of the Faculty of Life Sciences ( LF ) and the School of Chemical Engineering and Analytical Sciences ( CEAS ) . A hebdomadal meeting will be held where the pupil will supply updates ( either through study or presentation of consequences ) to the supervisor so as to discourse and analyze consequences, to supervise the advancement of the undertaking and decide challenges that may be encountered during the continuance of the undertaking. Researchers ( either Dr Pittman or Olumayowa or both ) will besides be available at LF to analyze the results of experiment and do occasional visits to CEAS so that consequences can be farther analysed while besides doing usage of their expertness in microalgae biofuel to do relevant suggestions that can help the success of the research.
The work program for the undertaking is attached with this proposal which shows that an estimation of approximately 14 hebdomads. A start day of the month of June 6, 2011 is suggested ( though theoretical surveies have started long before this day of the month ) and a deadline day of the month for entry of a thesis study by the pupil to the School of Chemical Engineering and Analytical Sciences ( CEAS ) is September 9, 2011.
It is likely that all the stated aims may non be achieved during the continuance of this undertaking sing the short period involved and possibility of unexpected challenges that may originate along the manner ; which is non uncommon for application of fresh methods. However, the concluding study that will be submitted will be comprehensive plenty to detail the challenges and chances of this method for future research.
2.5 Relevance to Beneficiaries
We will be working closely with Dr. Jon Pittman of the Faculty of Life Sciences and Olumayowa Osundeko of the Sustainable Consumptive Institute both of whom have been transporting out research on optimising and bettering the lipid content of microalgae cells through sustainable cultivation. We will be using their research installations to cultivate microalgae cells, monitor their growing and step the entire lipoids extracted. These research workers have echt involvement in the result of this undertaking as a consequence of the demand to develop a downstream procedure that will ease harvest home of microalgal biomass particularly from a effluent wastewater and subsequent lipid extraction. This implies that our proposed method, if successful, will profit research workers within the Faculty of Life Sciences, Sustainable Consumptive Institute, and their United kingdom and international webs.
Furthermore, generated experimental informations and consequences and developed surface assimilation isotherms for microalgae cells/ NyexA®100 systems will be the first of its sort which can be utilized by the research community to enable them understand the recovery rules of microalgal biomass and extraction of lipoids utilizing surface assimilation and electrochemical procedures severally. The research community has been wishful of a engineering that is cost-efficient and simple in operating ; our proposed method has the possible to accomplish this position. In add-on, new accomplishments and cognition will be generated that will authorise the research community towards detecting a sustainable energy option ; a sine qua non for a secured hereafter.
The benefit of the research will besides include development of a methodological analysis, if successful, will intend that a novel and advanced technique has been introduced for the first clip which can so be farther exploited to measure the possibility of its commercial application.
This method is a individual phase extraction procedure that will non necessitate the demand to transport harvested microalgal biomass thereby taking the hazard of material loss. Furthermore, as it involves neither the usage of extra dissolver nor usage of mechanical equipment to do cell break, it is expected to be comparatively cheaper than present methods. In add-on, it can take down the energy strength associated with present methods as intracellular merchandises such as lipoids will be extracted from the wet biomass without demand for drying. Furthermore, an indispensable consideration in the procedure of microalgal cells, as with managing biological stuffs, is that it should take topographic point every bit quickly as possible to continue the value of stuffs in the beginning cells ( Greenwell et al 2010 ) ; doubtless, this may be a cardinal advantage of our procedure as it involves a individual phase process. All these advantages will evidently be to the benefits of the microalgae biofuel industry.