Algae production: an overview ofexisting optionsYusuf ChistiSchool of EngineeringMassey University, Palmerston NorthNew Zealandb)Outline2. Algal fuels a conceptual production process7. Summary and conclusions6. Improving prospects of algal energy3. Algal biomass production options1. Microalgae an only option for biofuels3 m4. What affects productivity in photobioreactors?5. Attributes of a commercial algaUnited States biodiesel needs = 0.53 billion m3(to replace all transport fuel 2007 data)CropOil yield (L/ha) Land area needed (M ha) Percent of existing US cropping area Corn1723,0801,692 Soybean4461,188652 Canola1,190446244 Jatropha1,892280154 Coconut2,689198108 Oil palm5,9509048 Microalgae35,20215.28 Microalgae70,4057.64 Microalgae35,20215.28 Microalgae70,4057.64 20% w/w oil in biomass40% w/w oil in biomassNot feasibleMicroalgae an only option for biofuelsProved productivity1.535 kg m3day1(~158 tons ha1year1)The case of biodieselMicroalgal fuels process conceptA necessary stepBiogas quality: 16.230.6 MJ m3Yield: 0.150.65 m3kg1dry biomassBiomass extractionAlgal oilLiquid fuels- Diesel- Gasoline- Jet fuelAlgal biomass productionBiomass recoveryWater + nutrientsLightCO2H2O/nutrientsAnimal feedOther productsEffluent- Fertilizer- IrrigationAnaerobic digestionPower generationBiogasCO2Power for algae production Microalgal biomass productionOption 1: Raceway pondsTypical biomass productivity0.025 kg m2day1(~82 tons ha1year1)Maximum biomass concentration1 kg m3(0.5 kg m3typical)Cyanotech, USAPaddlewheelYaeyama, JapanAquacarotene, AustraliaOption 2: Tubular photobioreactorsMicroalgal biomass productionProved biomass productivity1.535 kg m3day1(~158 tons ha1year1) Biomass concentration4 kg m3Javan, Tajikistan (Tredici, 1999)Photobioreactors Ltd, Cartagena, SpainOption 3: Vertical column photobioreactors and variantsMicroalgal biomass productionBiomass productivity- Greater than raceways- Less than tubular photobioreactorswww.bioenergy-noe.orgwww.nerc.ac.ukNovagreen GmbH, GermanyOption 4a: Thin channel airlift and forced flow photobioreactorsMicroalgal biomass productionVertigro Energy- Relatively inexpensive- High surface-to-volume ratioOption 4b: Thin channel airlift and forced flow photobioreactorsMicroalgal biomass productionDr. Peter RipplingerSubitec GmbH, GermanyFuturistic photobioreactors (architects and artists concepts)www.inhabitat.comMicroalgal biomass productionProduction in the seaTurks & CaicosMaldives- Vertically floating columns, bags, thin channels- Individually anchored to seabed- Glass columns, protective fenders, active coatings- Tubing networks for nutrient feeding/harvesting- Each with individual solar powered control unit- Central compressors, etc.A tubular photobioreactorDegassingcolumnExhaustAirHarvestFreshmediumSolar arrayPumpCoolingwaterCyanotech, USAFactors that affect algal culture in photobioreactorsPhotoinhibitionIrradiance, I0 2 4 601maxPhotoinhibitedgrowthFig. 30Fluid mechanics- Shear sensitivity of cells- Mass transfer- Temperature controlIrradianceGrowth kineticsnavnav maxI KIn+= Mass transfer- CO2supply- O2removalThermal engineering- Temperature control Culture mediumFlashing light effectCapital cost of culture systemsUS$ (2008)$125,000/haRaceways$1.1 M/ha (8-10 x raceway)Tubular photobioreactorsLess than tubular photobioreactors?Less than raceways?Thin channel airlift photobioreactorLess than tubular photobioreactorsVertical columnsVertical bags$181,000/ha(95 ha facility)Attributes of a commercial microalgaDesired characteristics- High oil productivity during growth- Open culture tolerant of high/variable salinity good resistance to competitors- Morphology large, freely suspended cells no films, filaments, surface growth- Temperature tolerance both high and low- Robustness low sensitivity to shear force- High value of light saturation constantImproving the energy prospects of algaeGenetic and metabolic engineering issues1. Increase photosynthetic efficiency and biomass yield2. Biochemistry of oil synthesis - increase oil content in biomass 3. Improve temperature tolerance of algae 4. Eliminate the light saturation phenomenon5. Reduce/eliminate photoinhibition6. Engineer nitrogen fixation in algaeGenetic and metabolic engineering7. Incorporate age-dependent cell lysis to simplify oil recoveryImproving the energy prospectsMussgnug et al., Plant Biotechnol. J., vol. 5, pp. 802814 (2007)Cell concentration = 6106cells/mLChlamydomonas reinhardtiiParent strain Transformed strainRelative chlorophyll concentrations1.0 1.8Relative photosynthetic quantum yield8. Improve light penetration reduce light harvesting antenna sizeto enhance photon capture efficiency under high lightSummary and conclusions4. Factors that influence biomass productivity3. Biomass production options raceways and photobioreactors- thoughts on sea-based production2. A conceptual process for producing algal oils5. Desired traits in a commercial alga1. Microalgae as an only source of liquid transport fuels6. Strategies for improving the prospects for algal energy