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Microalgae for the production of bulk chemicals and fuels

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Microalgae for the production of bulk chemicals and fuels

  1. 1. Correspondence to: Rene H. Wijffels, Wageningen University, Bioprocess Engineering, PO Box 8129, 6700 EV Wageningen, the Netherlands.E-mail: rene.wijffels@wur.nl© 2010 Society of Chemical Industry and John Wiley & Sons, LtdReview287Microalgae for the productionof bulk chemicals and biofuelsRene H Wijffels, Bioprocess Engineering, Wageningen University, the NetherlandsMaria J Barbosa, Food and Biobased Research, Wageningen University and Research Center, the NetherlandsMichel H M Eppink, Bioprocess Engineering, Wageningen University, the NetherlandsReceived January 19, 2010; revised March 17, 2010; accepted March 18, 2010Published online in Wiley InterScience (www.interscience.wiley.com); DOI: 10.1002/bbb/215;Biofuels, Bioprod. Bioref. 4:287–295 (2010)Abstract: The feasibility of microalgae production for biodiesel was discussed. Although algae are not yet producedat large scale for bulk applications, there are opportunities to develop this process in a sustainable way. It remainsunlikely, however, that the process will be developed for biodiesel as the only end product from microalgae. In orderto develop a more sustainable and economically feasible process, all biomass components (e.g. proteins, lipids, car-bohydrates) should be used and therefore biorefining of microalgae is very important for the selective separation anduse of the functional biomass components. If biorefining of microalgae is applied, lipids should be fractionated intolipids for biodiesel, lipids as a feedstock for the chemical industry and w-3 fatty acids, proteins and carbohydratesfor food, feed and bulk chemicals, and the oxygen produced should be recovered also. If, in addition, production ofalgae is done on residual nutrient feedstocks and CO2, and production of microalgae is done on a large scale againstlow production costs, production of bulk chemicals and fuels from microalgae will become economically feasible.In order to obtain that, a number of bottlenecks need to be removed and a multidisciplinary approach in which sys-tems biology, metabolic modeling, strain development, photobioreactor design and operation, scale-up, biorefining,integrated production chain, and the whole system design (including logistics) should be addressed. © 2010 Societyof Chemical Industry and John Wiley & Sons, LtdKeywords: microalgae; bulk chemicals; biorefinery process designIntroductionMicroalgae are receiving a lot of attention presentlybecause of their potential use as a feedstock forthe production of biodiesel. Worldwide researchprograms are initiated to develop technology for the produc-tion of biodiesel from microalgae and many new companieshave been developed and most probably will develop in thefuture.Microalgae have potentially an areal productivity superiorto traditional agricultural crops.1,2Realistic estimates forareal productivity are in the order of magnitude of 40-80tonnes of dry matter per year depending on the technol-ogy used and the location of production.3In many cases,estimates published are too high and sometimes higher thantheoretically possible. These overestimations lead to unre-alistic expectations; even in the European Union Researchand Development framework, consortia are invited to submit
  2. 2. 288 © 2010 Society of Chemical Industry and John Wiley & Sons, Ltd | Biofuels, Bioprod. Bioref. 4:287–295 (2010); DOI: 10.1002/bbbRH Wijffels, MJ Barbosa, MHM Eppink Review: Microalgae for bulk chemicals and biofuelsproposals to develop demonstration projects with the objec-tive of establishing a 10 ha production facility with productiv-ity between 90 and 120 tonnes of dry algal biomass per year.The objective is to build three of these demonstration plants(www.cordis.europa.eu: FP7-ENERGY-2010-2 BIOFUELFROM ALGAE).In contrast to terrestrial crops, hardly any productioncapacity for microalgae exists at this stage. Production isdone in niche markets for high-value products, such as themost common products carotenoids and w-3-fatty acids.The world production of microalgae is about 5 million kg ofdry biomass with a total market volume of €1.25 billion. Themarket price of microalgae is on average €250/kg dry bio-mass.4Nevertheless, microalgae are considered a very prom-ising crop for production of biofuels due to their high arealproductivity in comparison to terrestrial crops and the lackof competition for land that is suitable for agriculture –microalgae can be grown on seawater. To make microalgaereally interesting as a source of biofuels, the cost price forproduction needs to be reduced and the scale of productionneeds to be increased significantly. We believe that techni-cally this will be feasible, but it will take a tremendous effortto realize this and we expect that development to a com-mercial process will at least take 10 years.5Simultaneouslywith the development of the technology, it is important topay attention to the design of the whole system taking intoaccount the logistics of water, nutrient, and CO2 supply anda complete life cycle analysis to determine at which scale andlocations production needs to take place.For production of algal biomass for biodiesel purposes, itis essential that the production capacity (hectares of culture)increases and the cost of production decreases dramatically.Presently there is no significant algal production capacity;the technology is immature and needs to be fully developed,implying that a large effort in research, pilot studies, anddemonstration studies is required. It is unrealistic to expectthat the technology of algal production will be competitivefor the energy market within the coming five years but withsufficient effort it might become attractive after ten.Microalgae contain 30–60% lipids that can be convertedinto biodiesel.6The value for diesel is presently €0.50/liter.This indicates that the production cost of microalgae maynot be higher than €0.40/kg, excluding costs of extractionand conversion of lipids into biodiesel. If, however, thetechnology develops, the production capacity will graduallyincrease and the production cost will reduce. As capacityincreases and the prices go down, new markets will openand markets will evolve from niche products toward food,feed, pharma, bulk chemicals, and finally also fuels.In this review, we will describe the present status of thetechnology and discuss the potential cost price of produc-tion as well as the need for biorefining for developmentof sustainable markets. Finally, we will describe the idealagenda for research and development of algal technology.The present hype around microalgae is not realistic, but if wehave the patience and the resources to develop fundamen-tal and applied research, the technology will develop as animportant pillar of sustainable production of large quantitiesof biomass for food, feed, bulk chemicals, and energy.Biodiesel from microalgaeMicroalgae accumulate large quantities of hydrophobic com-pounds. The best example of that is Botryococcus braunii.Botryococcus braunii does not produce lipids, but less oxygen-ated isoprenoids; almost alkane-like structures with approxi-mately 32 to 38 C-atoms. These components can be usedin existing oil refineries. The concentration of these com-pounds can be as high as 70% of the biomass. In addition,the cell wall of Botryococcus is thin and the oil can be easilyextracted. The cells almost spontaneously excrete these oils(Fig. 1). Unfortunately, Botryococcus is difficult to culture andFigure 1. Botryococcus braunii excretes oil spontaneously.
  3. 3. © 2010 Society of Chemical Industry and John Wiley & Sons, Ltd | Biofuels, Bioprod. Bioref. 4:287–295 (2010); DOI: 10.1002/bbb 289Review: Microalgae for bulk chemicals and biofuels RH Wijffels, MJ Barbosa, MHM Eppinktherefore isn’t so much used in development of processes forproduction of biodiesel from microalgae. This example, how-ever, shows that oil excretion could simplify part of the biore-finery approach for other algae strains with oil excretion.The production of lipids from microalgae, preferablytri-acylglycerides, is receiving the most attention. The con-centration varies between 20 and 60%. Accumulation tohigh concentrations in lipid globules generally takes placeafter stress.7First algae are grown and then they need to bestressed – for example by nutrient limitation – to induceaccumulation of lipids. Generally the biomass productivitydecreases substantially under these stress conditions.At present, hardly any algae are produced for the produc-tion of lipids for biofuels. Estimates are therefore very rough.We estimate that with algae it will be possible to produce 20000–80 000 liters of lipids per hectare per year. On the basisof the present technology, the productivity will not be higherthan 20 000 liters per hectare per year; if the technologydevelops, we might eventually reach 80 000 liters per year.This is considerably higher than production via terrestrialcrops: palm and rapeseed oils are produced at 6000 and 1500liters per hectare per year, respectively.Lipids need to be extracted from the microalgae to producebiodiesel. There are two processes to convert the lipids intobiodiesel: esterification and hydrogenation. In the case ofesterification, the glycerol esters are converted into methylesters.1By catalytic hydro conversion, triglycerides are con-verted into linear hydrocarbon chains. In hydrogenation, thelipids are converted into alkanes.8Feasibility studyAlthough large-scale processes for biodiesel productionfrom algae have not been developed, expectations of algaefor this application are very high. Production of algae needsto take place on a large scale and against minimal costs.Currently, algal products are on the market for equivalentbiomass values two orders of magnitude higher than theymay be for biodiesel production. The question is whetheralgal biomass can be produced at a cost below €0.50/kg.For this reason, we executed a feasibility study. In thisfeasibility study, process designs were made for productionof algae in systems that could be built with the presenttechnology, without further technological advances. Threesystems were designed: an open pond raceway system, atubular photobioreactor and a flat panel reactor. Designswere made at a scale of 1 hectare and at 100 hectares tounderstand the effect of scale. The objective was not only tocalculate the absolute cost of production of 1 kg of algae, butalso to understand the cost factors involved in order to beable to optimize the process.The designs were based on industrial processes; costsfor tubing, maintenance, and operation were taken intoaccount. In the designs, we made conservative estimates: forexample, we used solar conditions in the Netherlands witha moderate climate; if plastic materials were used for thephotobioreactor, it was assumed that the plastic needed to berenewed every year; we assumed productivities that are cur-rently obtained at large scale with these techniques; and weassumed we had to buy CO2 and nutrients.As an example, the production cost is shown in a flatpanel reactor system at a scale of 1 ha. The cost of produc-tion is approximately €9/kg. The main cost factors in thiscase are power and labor (Fig. 2). If the system is scaled up,labor costs can be reduced significantly. The cost price forbiomass in a reactor of 100 ha is about €4/kg. A cost priceof €4/kg would be acceptable for the production of biomassfor high-value compounds but unacceptable for the produc-tion of biodiesel. More than 24% of the cost was for energyconsumption; i.e. pumping around of water and sparging ofair/CO2 in the system. As a matter of fact, the energy inputwas larger than the energy chemically stored in the biomass,which makes the technology unsuitable for production ofbiodiesel. We have to realize, however, that there has neverbeen a driver for those commercial companies currentlyoperating in the field of microalgae to reduce the cost ofenergy. The cost of energy in this example is less than €2/kgbiomass. The total value of algal biomass for high-valueproducts is about €100/kg, which means there is hardly anydriver for the industry to reduce energy input.In order to evaluate whether cost prices could be signifi-cantly reduced if the technology is further developed forbiodiesel production, we performed a sensitivity analysisand studied the effect of reducing specific cost factors; forexample, the source of CO2 and nutrients. In our cost cal-culations, we assumed that these feeds had to be boughtand we then looked at the effect of getting these resources
  4. 4. 290 © 2010 Society of Chemical Industry and John Wiley & Sons, Ltd | Biofuels, Bioprod. Bioref. 4:287–295 (2010); DOI: 10.1002/bbbRH Wijffels, MJ Barbosa, MHM Eppink Review: Microalgae for bulk chemicals and biofuelsfor free if they were obtained from residues. Another factorwe analyzed was a reduction of energy input to 10% of theoriginal value. We also assumed we could raise the produc-tivity by assuming a photosynthetic efficiency of 7% insteadof the 5% we originally used. Finally we assumed that theprocess would be applied in an area with more sunshine: theisland of Bonaire in the Caribbean. If all these factors wereincluded, a cost price for biomass production of €0.40/kgcould be obtained.The cost prices of the other processes (raceway pond andflat panel reactor) were in the same order of magnitude.There was, however, a difference in the cost reduction thatcould be obtained. While in the tubular photobioreactor, wecould reduce the cost price by 90% after optimization, wecould only reduce the costs in a raceway pond by 50%. Thereason for this is that raceway ponds are used much moreat larger scale and there is less room for improvement inthese systems. Although generally assumed that productionin photobioreactors is much more expensive than in a race-way system, we found that after optimization, cost prices inclosed systems were actually lower than in a raceway pond.Biorefining of microalgaeThe next question is whether it is economically feasible toproduce biodiesel from microalgae if we are able to reducecost price of biomass production to €0.40/kg. If we assumethat algae contain 40% lipids and the value of biodiesel is€0.50/liter, the value of the biomass used for biodiesel produc-tion is only €0.20/kg. It also needs to be considered that costsfor extracting the lipid and converting the lipids into biodie-sel were not taken into account. This means that it will not befeasible to produce algae solely for the production of biodiesel.For this reason we looked at the possibility of refining algalbiomass into different products and analyzed the total valueof the biomass. We did not assume a combination of high-value products in niche markets because the market volumesof high-value products and biodiesel are incompatible. Weassumed biorefining of algal biomass into products for bulkmarkets making use of the functionality of the products. Thecase is randomly chosen and is only used to analyze whether1 ha100 hapotentialIron frame Centrifuge westfalia separator AGCentrifuge Feed Pump Medium Filter UnitMedium Feed pump Medium preparation tankHarvest broth storage tank Seawater pump stationAutomatic Weighing Station with Silos Air BlowersInstallations costs Instrumentation and controlPiping BuildingsPolyethylene Culture mediumCarbon dioxide Media FiltersAir filters PowerLabor Payroll chargesMaintenance General plant overheads7.9 /kg biomass4.0 /kg biomass0.4 /kg biomass15 /GJFigure 2. Costs and cost factors for the design of flat panel photobioreactors at a scale of 1 and 100 ha.Figure 3. Value of algal biomass per 1000 kg after biorefining.
  5. 5. © 2010 Society of Chemical Industry and John Wiley & Sons, Ltd | Biofuels, Bioprod. Bioref. 4:287–295 (2010); DOI: 10.1002/bbb 291Review: Microalgae for bulk chemicals and biofuels RH Wijffels, MJ Barbosa, MHM Eppinkthe total value of the biomass produced is sufficient to allowproduction costs of €0.40/kg (Fig. 3).We assumed production of algal biomass consisting of40% lipids, 50% proteins and 10% carbohydrates. A moredetailed overview is presented in Carioca et al.6If the lipidfraction is not only used for production of biodiesel but alsoas a feedstock for the chemical industry (e.g. in coatings) orfor edible oils (e.g. w-3-fatty acids) the lipid fraction of thealgae increases in value. We assumed in this case that 25% ofthe lipids is used for these functional products with an esti-mated value of €2/kg and 75% is used for biodiesel produc-tion with a value of €0.50/kg.In addition, proteins could be fractionated into a watersoluble fraction (e.g. Rubisco) of 20% and a water insolublefraction of 80%, taking into account that the water solublefraction has a food value (€5/kg) and the insoluble fraction afeed value (€0.75/kg).Finally a carbohydrate fraction of 10% was assumed. Thecarbohydrates in algae are very low in cellulose. They are,in general, storage products such as fructans, glucans, andglycerol which can be used as chemical building blocks orfor production of bioenergy. We assumed the value of carbo-hydrates to be €1/kg.Besides these main products, there are additional byprod-ucts, such as reduction of nutrients in waste streams andproduction of oxygen. In waste-water treatment, the removalof nitrogen compounds via nitrification and denitrifica-tion is an expensive process; the cost of nitrogen removalis €2/kg. Microalgae contain 70 kg of nitrogen per 1000 kgof microalgae. If algal production would be combined withwaste-water treatment we would save €140 for nitrificationand denitrification per ton of algae produced. A similaranalysis could be made for phosphate.Algae produce oxygen-rich gas. Per ton of algae 1600 kg ofoxygen-rich gas is produced. In aquaculture, oxygen-rich gasis used for supply of sufficient oxygen to the fish. The value ofthe gas produced is approximately €0.16/kg of oxygen. If thetotal value of all these products is added up, we come to a totalvalue of the biomass of €1.65/kg of algae. Of course the refin-ing of these components will be at a certain cost. The analysisshows, however, that if algal biorefining is used, the total valueis higher (€1.65/kg) than the total cost for algae production(€0.40/kg) and makes it worthwhile to develop this approach.Overall, we can conclude that the production of only biodie-sel from microalgae is economically not feasible but that anintegrated biorefinery concept of microalgae with biodiesel asone of the products can lead to a feasible process.Development of a new technologyWe have shown that the production of microalgae for copro-duction of biodiesel and bulk chemicals can become eco-nomically feasible. In addition, if the technology develops,we expect that the cost price of production of microalgaewill reduce gradually. Microalgae are now produced forhigh-value products in niche markets; however, if the costprice of production goes down; it is expected that new mar-kets will open with every step in reduction. Initially, mostprobably the production of edible oils for food and fish feedwill become feasible, but after some time production of bulkchemicals, biomaterials, and biodiesel may also become fea-sible. For that the technology needs to develop from a small-sized activity to an industrial scale technology. We expectthat such a development will at least take ten years. For thata multidisciplinary approach needs to be developed as sche-matically shown in Fig. 4.Systems biologySystems biology in microalgae has hardly been developed.In the first place, algae originate from different families,Figure 4. Multidisciplinary approach for development of industrialalgae production.
  6. 6. 292 © 2010 Society of Chemical Industry and John Wiley & Sons, Ltd | Biofuels, Bioprod. Bioref. 4:287–295 (2010); DOI: 10.1002/bbbRH Wijffels, MJ Barbosa, MHM Eppink Review: Microalgae for bulk chemicals and biofuelsvarying from prokaryotes like cyanobacteria to eukaryoteslike green algae (chlorophytes).Establishing industrial production with algae requiresamong others, in-depth knowledge of basic biologicalfunctions and tools for steering the metabolism, with theobjective of improving, for example, the photosyntheticefficiency in photobioreactors or enhancing lipid produc-tivity. This can be done by an optimal design of condi-tions inside the reactor or by metabolic engineering. A keytechnology in the successful application of both optimalconditions design and metabolic engineering is the avail-ability of well-annotated genomes and quantitative tools forgenome-scale metabolic models that permit understand-ing and manipulation of the genome. There are still veryfew algae for which full or near-full genome sequenceshave been obtained and transvection systems have barelybeen developed. An additional challenge remains to inte-grate the genome datasets with datasets from other levelsof biological organization. An integrated approach usingstate-of-the-art technologies, such as genome sequencing,transcriptomics, metabolomics, proteomics, metabolicmodeling (fluxomics), and bioinformatics, is needed inorder to gain the best possible insight into metabolic path-ways leading to the product of interest. This systems biol-ogy approach is the basis for the enhancement of the physi-ological properties of algae strains and the optimizationof algae production systems. Even though this approach isused more and more in microbial and plant sciences, it isstill new in algal biology. It is expected that research in thisfield will develop quickly and tools will become available toimprove photosynthesis in algae, to enhance productivityof lipids in microalgae, and many other features that maylead to a reduction in cost prices or a higher reliability ofthe whole process chain.Metabolic flux modelingGenome-based metabolic flux models are in their infancyand are expected to be developed in the coming years. Withthese metabolic flux models, we will be able to understandand steer metabolism in microalgae with the objective ofimproving, for example, the photosynthetic efficiency inphotobioreactors or enhancing lipid productivity. Metabolicflux models can be used both to design the conditions in areactor such that a better process is obtained and to targetmetabolic engineering approaches.Strain developmentOnly a few microalgal strains are produced commercially(e.g. Spirulina, Chlorella, Dunaliella, Haematococcsu andNannochloropsis). These strains are probably not the beststrains for the production of biodiesel. For this reason weneed to screen for new strains or modify the strains suchthat optimal production of lipids for biodiesel becomes feasi-ble. Ideally microalgae should have the following qualities:• High productivity (of metabolites)The productivity of biomass should be high. If it is pos-sible to produce large quantities of biomass per surfacearea, the cost of production reduces significantly. Inaddition to productivity of biomass, the productivityof metabolites, such as lipids, should also be high. Veryoften the process is done in two stages. Biomass is grownand then stressed at which stage the lipids start to accu-mulate. Although the concentration of lipids obtained ishigh, the volumetric productivity is in general low. It isimportant to select or improve strains in such a way thata high productivity in lipids is obtained.• High yield on lightRelated to productivity is the yield on light. The maxi-mum yield on solar light is 9%. In practice, it is a lotlower. Strains have already been developed with smallerantenna sizes allowing a higher photosynthetic yield athigh light intensities.• RobustThe process, and consequently the microalgae, needsto be robust. For biodiesel production, the scale of pro-duction needs to be so large that axenic operation oradvanced process control will hardly be possible. Thestrains therefore need to be stable under production cir-cumstances and stronger than possible infections. Ideallyit should be possible to grow the algae on a large scaleunder extreme conditions such as high or low pH, hightemperatures, or high salinity.• Grow at high pHWhile the supply of CO2 is essential for growth of algaeat high productivities, it is also an important cost factor.Ideally CO2 should be used from the atmosphere, but the
  7. 7. © 2010 Society of Chemical Industry and John Wiley & Sons, Ltd | Biofuels, Bioprod. Bioref. 4:287–295 (2010); DOI: 10.1002/bbb 293Review: Microalgae for bulk chemicals and biofuels RH Wijffels, MJ Barbosa, MHM Eppinkconcentration is too low to make high productivities pos-sible. Alternatively, the CO2 source is a residual gas thatneeds to be bubbled through the water column. As gasbubbling already requires energy, it is important that themass transfer of CO2 is efficient. At high pH (10–11), themass transfer is much higher and in addition the opera-tional conditions are selective.• Insensitive for oxygenMicroalgae produce oxygen. In many processes, oxygenaccumulates to high concentrations. At high concentra-tions of oxygen, the productivity of microalgae reducesconsiderably. Nevertheless, we would prefer to operateprocesses at high oxygen concentrations because degas-sing of the system requires energy and oxygen-rich gas isa nice byproduct.• FlocculateHarvesting microalgae is expensive. Microalgae aresmall and mostly individual cells. For that reasoncentrifugation is mostly used as a harvesting method.The biomass concentration is in general also low.Centrifugation of diluted streams requires a large-capac-ity centrifuge and consequently harvesting is expensive.If algae flocculate, harvesting costs could be reduced sig-nificantly and filtration, sedimentation or flotation canbe used for harvesting instead of centrifugation. Ideallyalgae would flocculate spontaneously at a certain stage ofthe process.• Large cells with a thin cell wallMicroalgae are, in general, relatively small and havea thick cell wall. In order to break cells to extract theproducts, very harsh conditions need to be used (e.g.mechanical, chemical, physical stress). This makes break-ing up cells not only very expensive but also affects thefunctionality of compounds like proteins. Ideally theextraction could be so mild that water extraction at lowtemperatures can be applied. This requires cells that areeasy to break but are strong enough that no shear dam-age takes place during production. Small spherical cellswith a thick cell wall, like Nannochloropsis, clearly arenot the ideal algae for this reason.Photobioreactor design and operationThe ideal photobioreactor requires low investment costs andlow operational costs but still has a high productivity and isscalable. Design of photobioreactors is not easy as a large sur-face-to-volume ratio is required for efficient supply of solarlight. At the same time, the high surface-to-volume ratiomakes scale-up difficult in respect to mass and heat transfer.On top of that, solar conditions change continuously. Manytypes of photobioreactors have been developed and probablyFigure 5. Thin plastic film photobioreactor of Proviron (A) and Solix Biofuels (B).(A) (B)
  8. 8. 294 © 2010 Society of Chemical Industry and John Wiley & Sons, Ltd | Biofuels, Bioprod. Bioref. 4:287–295 (2010); DOI: 10.1002/bbbRH Wijffels, MJ Barbosa, MHM Eppink Review: Microalgae for bulk chemicals and biofuelsmany more will still be developed. For evaluation of designs,it is important to compare performance of the differentsystems under the same operational conditions for longerperiods of time. In the feasibility analysis we showed thatphotobioreactors could become competitive if investmentcosts were reduced significantly. Investment costs should beless than €15/m2.9Thin plastic film bioreactors are presentlydeveloped for this reason. Examples are shown in Fig. 5.Scale-upDevelopments in the microalgae field are mainly drivenby end users. For the end users there is a limited supplyof biomass to develop further processes. For this reasononly, some production capacity needs to be realized.Single products like biodiesel from algae can then bedeveloped and tested and the biorefinery program can bedeveloped.In addition, there is no or hardly any experience withproduction of algae on a larger scale under outdoor condi-tions for longer periods of time. For this reason, it is veryimportant not only to do research at laboratory scale butalso to develop pilot programs to evaluate and compare theirperformance as a basis for design of demonstration-scalefacilities.In order to facilitate quick development of the technologyresearch at laboratory scale, pilot scale and demonstrationscale programs should run parallel with a good exchange ofinformation such that technology developed in the labora-tory can be tested under realistic conditions and research atlaboratory scale can be done for the problems encountered atlarge scale.BiorefineryEconomical, feasible production of microalgae for biodieselwill only be possible if it is combined with production ofbulk chemicals and food and feed ingredients. Research anddevelopment of biorefineries is therefore very important inthis field to explore mild cell disruption, and extraction andseparation technologies on algal biomass. Compounds suchas w-3-fatty acids, carbohydrates, pigments, vitamins, andproteins should maintain their functionality in this processand at the same time scalability, low energy costs, and easeof use also need to be taken into account.Integrated process chainSo far, individual productions steps have been discussed andit is highly recommended to develop an integrated algae pro-duction chain by combining the different process units intoa complete process. Uncertainties in specific process units(upstream) may have an impact on the process units down-stream in the production chain. Therefore, whole productionprocesses, upstream and downstream, should be developedand tested on pilot and demonstration scales.Systems designProduction of microalgae on a large scale will be complexwith respect to logistics and space needed. Productivity ofmicroalgae does not only depend on the availability of sun-light, but on the availability of land, water resources, CO2,and nutrients as well. Transport of the different feedstocksover long distances most probably is not a feasible option.This makes it more difficult to determine beforehand whatthe best locations for production are and what the scale ofproduction should be. At this moment it is unclear if futurealgae production plants will be of enormous scale or whetherit will become an activity similar to farming land cropsnowadays.To design the system processes, logistics and Life CycleAssessments needs to be analyzed.ConclusionsWe have discussed production of microalgae for biodiesel.We have shown that although algae are not yet produced ona large scale for bulk applications, there are opportunitiesto develop these processes in a sustainable way. However, itis unlikely that the process will be developed for biodieselas the sole end product. In order to develop a sustainableand economically feasible process, all biomass componentsshould be used; therefore biorefining of microalgae is veryimportant for the development of the technology.The production technology of microalgae is, however,immature and efforts have to be made to develop an eco-nomical sector. In respect to the development of the technol-ogy, it is proposed to develop multidisciplinary research onsystems biology, metabolic flux modeling, strain develop-ment, photobioreactor design, scale-up, biorefining, inte-grated process chain, and systems design.
  9. 9. © 2010 Society of Chemical Industry and John Wiley & Sons, Ltd | Biofuels, Bioprod. Bioref. 4:287–295 (2010); DOI: 10.1002/bbb 295Review: Microalgae for bulk chemicals and biofuels RH Wijffels, MJ Barbosa, MHM EppinkReferences1. Chisti Y, Biodiesel from microalgae. Biotechnol Advances 25:294–306(2007).2. Clarens AF, Resurreccion EP, White MA and Colosi LM, Environmentallife cycle comparison of algae to other bioenergy feedstocks. Env SciTechnol 44:1813–1819 (2010).3. Wijffels RH, Potential of sponges and microalgae for marine biotechno-logy. Trends Biotechnol 26:26–31(2008).4. Pulz O and Gross W, Valuable products from biotechnology of micro-algae. Appl Microb Biotechnol 65:635–648 (2004).5. Barcley B, Algae oil production. Keynote lecture at the Algal BiomassOrganization 2009 summit, San Diego; October 7–9 (2009).6. Carioca JOB, Hiluy Filho JJ, Leal MRLV and Macambira FS, The hardchoice for alternative biofuels to diesel in Brazil. Biotechno Adv 27:1043–1050 (2009).7. Rodolfi L, Chini Zittelli G, Bassi N, Padovani G, Biondi N, Bonini Mand Tredici MR, Microalgae for oil: strain selection, induction of lipidsynthesis and outdoor mass cultivation in a low-cost photobioreactor.Biotechnol Bioeng 102:100–112 (2009).Dr René H. WijffelsDr René H. Wijffels is a professor at Wage-ningen University. He heads the BioprocessEngineering Group which is researching thedevelopment of new biotechnological proc-esses for manufacturing of pharmaceuticals,healthy food ingredients, bulk chemicals, andbiofuels. Dr Wijffels received his MSc in Envi-ronmental Technology and his PhD in Bioprocess Engineering.Dr Maria BarbosaDr Maria Barbosa is a researcher at the busi-ness unit Biobased Products at WageningenUniversity and Research Centre. Her presentarea of expertise is the cultivation and biorefin-ing of microalgae, with a focus on applied re-search. Dr Barbosa holds a PhD in BioprocessEngineering obtained at Wageningen University.Dr Michel EppinkDr Michel Eppink is Associate Professor at theBioprocess Engineering Group at WageningenUniversity. He is also Department Head ofDownstream Processing at the Biopharma-ceutical Division of Synthon BV. Dr Eppink re-ceived his MSc in Biology/Chemistry in 1993from the University of Utrecht and his PhD in1999 from the Agriculture University of Wageningen.8. Lestari S, Mäki-Avela P, Beltramini J, Lu GQM and Murzin DY,Transforming triglycerides and fatty acids into biofuels. ChemSusChemDOI 10.1002/cssc.200900107 (2009).9. Schenk PM, Thomas-Hall SR,Stephens E, Marx UC, Mussgnug JH,Posten C, et al., Second generation biofuels: High-efficiency microalgaefor biodiesel production. Bioenerg Res 1(1):20–43 (2008).

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