INDUSTRIAL PRODUCTION OF MICROALGAE BY AN ECO-SUSTAINABLE INDUSTRIAL PRODUCTION OF MICROALGAE BY AN

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  • Sede Amministrativa:

    UNIVERSITÀ DEGLI STUDI DI PADOVA

    DIPARTIMENTO DI INGEGNERIA INDUSTRIALE

    CORSO DI DOTTORATO DI RICERCA IN: Ingegneria Industriale

    CURRICOLO: Ingegneria Chimica, dei Materiali e Meccanica

    CICLO: XXIX

    INDUSTRIAL PRODUCTION OF MICROALGAE

    BY AN ECO-SUSTAINABLE PROCESS:

    LIGHT UTILIZATION EFFICIENCY AND

    NUTRIENT RECYCLING

    Direttore della Scuola: Ch.mo Prof. Paolo Colombo

    Coordinatore di indirizzo: Ch.mo Prof. Giovanni Meneghetti

    Supervisore: Ch.mo Prof. Alberto Bertucco

    Dottoranda: Elena Barbera

  • Contents

    ABSTRACT .......................................................................................................................................... 7

    FOREWORD ........................................................................................................................................ 3

    RIASSUNTO ......................................................................................................................................... 7

    INTRODUCTION .............................................................................................................................. 13

    CHAPTER 1- BIOFUELS FROM MICROALGAE:STATE OF THE ART ........................................ 17

    1.1. The global energy situation ................................................................................................ 17

    1.1.1. Fossil fuels .................................................................................................................... 17

    1.1.2. Biofuels ........................................................................................................................ 18

    1.2. Overview of microalgae as feedstock for biofuels production ........................................ 19

    1.3. Cultivation systems for microalgae ................................................................................... 21

    1.4. Downstream processes and biomass conversion routes .................................................. 24

    1.4.1. Chemical conversion .................................................................................................... 25

    1.4.2. Biochemical conversion ............................................................................................... 26

    1.4.3. Thermochemical conversion......................................................................................... 27

    1.4.4. Hydrothermal conversion ............................................................................................. 28

    1.5. Constraints to scale-up and commercialization of algal fuels ........................................ 30

    1.5.1. Nutrients recycling in microalgal cultivation ............................................................... 33

    1.6. The current industrial scenario ......................................................................................... 34

    CHAPTER 2 - MAXIMIZING THE PRODUCTION OF Scenedesmus obliquus IN

    PHOTOBIOREACTORS UNDER DIFFERENT IRRADIATION REGIMES: EXPERIMENTS AND

    MODELING ......................................................................................................................................... 37

    2.1. Introduction ........................................................................................................................ 38

    2.2. Experimental setup ............................................................................................................. 40

    2.3. Modeling .............................................................................................................................. 41

    2.3.1. PBR material balances .................................................................................................. 41

    2.3.2. Growth model ............................................................................................................... 43

    2.3.3. Model parameters ......................................................................................................... 45

    2.4. Results and discussion ........................................................................................................ 48

    2.4.1. Constant light intensity ................................................................................................. 48

    2.4.2. Day-night irradiation .................................................................................................... 54

    2.5. Final remarks ...................................................................................................................... 59

    CHAPTER 3 - IMPROVING LIGHT UTILIZATION AND PHOTOCONVERSION EFFICIENCY:

    INTEGRATED PHOTOVOLTAIC PHOTOBIOREACTORS FOR MICROALGAL CULTIVATION 61

  • 3.1. Introduction ........................................................................................................................ 62

    3.2. Materials and methods ...................................................................................................... 65

    3.2.1. Algae strains and culture media ................................................................................... 65

    3.2.2. Experimental set-up ..................................................................................................... 65

    3.2.3. Analytical procedures .................................................................................................. 69

    3.2.4. Photoconversion efficiency evaluation ........................................................................ 70

    3.3. Results and discussion ....................................................................................................... 71

    3.3.1. Cultivation of N. salina in PBR with a spectral-converter filter .................................. 71

    3.3.2. Cultivation of N. salina and S. obliquus in a Silicon PV-PBR .................................... 73

    3.3.3. Cultivation of S. obliquus in a DSC PV-PBR .............................................................. 84

    3.4. Final remarks ..................................................................................................................... 93

    CHAPTER 4 - ENERGY AND ECONOMIC ANALYSIS OF MICROLAGAE CULTIVATION IN

    ALGREENHOUSE (A PHOTOVOLTAIC-ASSISTED GREENHOUSE) ............................................. 95

    4.1. Introduction ........................................................................................................................ 96

    4.2. Methods ............................................................................................................................... 98

    4.2.1. Greenhouse and cultivation system configuration ....................................................... 98

    4.2.2. Irradiance and temperature simulations ....................................................................... 99

    4.2.3. Productivity simulations and energy balances ........................................................... 100

    4.2.4. Economical evaluation of the process ........................................................................ 104

    4.3. Results and discussion ..................................................................................................... 106

    4.3.1. Irradiances inside the greenhouse with and without PV ............................................ 106

    4.3.2. Temperature inside the greenhouse with and without PV.......................................... 108

    4.3.3. Productivity ................................................................................................................ 108

    4.3.4. Energy balance and yield ........................................................................................... 110

    4.3.5. Economic analysis...................................................................................................... 111

    4.4. Final remarks ................................................................................................................... 113

    CHAPTER 5 - CULTIVATION OF Scenedesmus obliquus AND Nannochloropsis gaditana IN THE

    LIQUID HYDROLYSATE OBTAINED FROM FLASH HYDROLYSIS OF THE SAME

    MICROALGAE .................................................................................................................................. 115

    5.1. Introduction ...................................................................................................................... 116

    5.2. Materials and methods .................................................................................................... 118

    5.2.1. Algae strains and culture media ................................................................................. 118

    5.2.2. Experimental set-up ................................................................................................... 119

    5.2.3. Analytical procedures ................................................................................................ 121

    5.3. Results and discussion ..................................................................................................... 122

  • 5.3.1. Batch experiments with Scenedesmus obliquus ......................................................... 122

    5.3.2. Batch experiments with Nannochloropsis gaditana ..............................................