Biodiesel Production from Microalgae - .I Final Report on Biodiesel Production from Microalgae

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  • I

    Final Report

    on

    Biodiesel Production from Microalgae

    - A Feasibility Study

    Presented to StatoilHydro ASA

    Oslo, Norway

    May 16, 2008

    Principal investigators: Tutors: Merit Lassing Christian Hulteberg, Lund University Peter Mrtensson Hans T. Karlsson, Lund University Erik Olsson Brre T. Brresen, StatoilHydro ASA Marcus Svensson Hans Eklund, StatoilHydro ASA

    KET050 Biodiesel Production from Microalgae

    Dept of Chemical Engineering, Lund University, Faculty of Engineering

  • II

    Disclaimer

    This report was prepared as a project in the course Feasibility Studies on Industrial Plants,

    (KET050), Department of Chemical Engineering, Faculty of Engineering, LTH, Lund

    University Sweden in cooperation with the Norwegian company StatoilHydro. Neither Lund

    University nor the authors of this report or StatoilHydro may be held responsible for the effects

    following from using the information in this report. Nor the authors, Lund university or

    StatoilHydro makes any warranty, expressed or implied, or assumes any legal liability or

    responsibility for the accuracy or completeness of this information.

    No reproduction is authorized without the written permission from the authors, or StatoilHydro

    or Lund University.

    http://www.chemeng.lth.se/ket050/http://www.ka.lth.se/kursplaner/Index%20eng.cfm?Studiear=07_08%20eng&SearchExpression=KET050http://www.chemeng.lth.se/about.jsp?lang=englishhttp://www.lu.se/englishhttp://www.lu.se/englishhttp://www.lu.se/english

  • III

    Abstract

    This is a student assignment for the Norwegian oil and gas company StatoilHydro, The aim of

    this study is to investigate the potential of large scale production of biodiesel from microalgae.

    Since the technology is new and no large facilities exist to date, this report focuses on suitable

    technologies for future biodiesel production.

    There exist many different algae strains with high oil content e.g. Phaeodactylum tricornutum,

    Nannochloropsis salina and Botryococcus braunii. The alga Botryococcus braunii was first

    selected for large scale biodiesel production, but after encountering many problems when

    looking into the process, the string of Nannochloropsis salina was chosen instead. The high

    hydrocarbon content of B. braunii was one of the key factors when this alga initially was chosen,

    together with the algaes ability to produce hydrocarbons during growth without the use of

    methods such as nitrogen starvation. Difficulties encountered when using this alga strain were

    separation problems since B. braunii has its hydrocarbons on the outside connecting the colonies,

    hence it is quite slimy. At the same time the colonies could be an advantage since the larger size

    means an easier separation. The fact that B. braunii is a fresh water algae is a big disadvantage in

    large scale production of biodiesel, if not having fresh water readily available, since this require

    a large desalination facility. Nannochloropsis salina on the other hand is a halotolerant string

    that prefers saline water similar to common seawater and has characteristics of producing high

    oil content within its cells. Nannochloropsis salina is therefore the alga strain used in this

    feasibility study for large scale biodiesel production.

    It is concluded that the most promising reactor type is the closed photobioreactor, since the other

    main alternative, the open pond, suffers from contamination risks, high evaporative losses of

    water and diffusion losses of CO2. Among the different types of closed photobioreactors; tubular,

    flat and polyethylene bags, the tubular seems to be the best choice since it has a higher

    photoefficiency than the flat reactor. The polyethylene bag reactor still needs developing and is

    not yet a viable alternative.

    After the algae have been harvested it is suggested that an increased dry weight is accomplished

    by a flocculation and sedimentation stage. The chosen method for the disruption of the cells is

    the utilization of a hydrodynamic cavitation process, followed by a stirring settling tank, where

    the oil floats and the cell debris sediment. Since hydrodynamic cavitation is a relatively unknown

    method, an alternative process using a wet bead mill for the cell breakage is presented as an

    alternative. However calculations are only performed on the former process alternative.

    In order to minimize losses in further refining and fulfill the EN 14214 standard for biodiesel

    production, the algal oil will in most cases need some kind of pretreatment. The most important

    purification steps will be degumming, which removes phosphorous content, as well as reaction

    of free fatty acids into methyl esters in order to avoid soap formation in the transesterification

    process.

    Suitable plant locations for StatoilHydro to put up a large scale biodiesel production facility are

    Qatar, South Africa and Australia. All cost estimates are made for a plant location in South

    Africa where the most suitable conditions can be found.

  • IV

    The following factors showed to be most accountable in the cost estimates of this production

    facility:

    The productivity of algae

    Lifespan of the photobioreactor

    Interest rate on capital for investment

    Harvesting concentration

    Different scenarios were estimated and the production cost ranges from 0.38 /L to 1.95 /L

    between the best and worst case scenario with 0.87 /L as the base case. An approximation that

    has been made is that nutrient/flocculant cost and algae meal revenue will balance each other. If

    the algae meal turns out to be worthless this will increase the algae oil price by 0.26 /L and

    hence could be fatal to the biodiesel production from microalgae.

    The price of comparable bio-based crude oil is today 122 $ barrel (palm oil) (1), which is

    approximately 0.49 per liter. This shows that even though profitability is still not achieved, it is

    concluded that profitability is not far away.

  • V

    Contents 1 Introduction .............................................................................................................................................. 1

    1.1 Why Algae for Production of Biodiesel? ............................................................................................ 1

    1.2 Technology State-of-the-Art ............................................................................................................... 2

    1.3 Brief Description of Production System ............................................................................................. 2

    2 Technology Suitable for Large-Scale Production ................................................................................. 4

    2.1 Problems in Photobioreactors ............................................................................................................. 4

    2.1.1 Oxygen Oversaturation ............................................................................................................... 5

    2.1.2 pH-value ...................................................................................................................................... 5

    2.1.3 Temperature ................................................................................................................................ 5

    2.2 Open Pond System .............................................................................................................................. 5

    2.2.1 Advantages .................................................................................................................................. 6

    2.2.2 Disadvantages ............................................................................................................................. 6

    2.3 Closed Photobioreactors ..................................................................................................................... 6

    2.3.1 Advantages .................................................................................................................................. 6

    2.3.2 Disadvantages ............................................................................................................................. 6

    2.3.3 Comparison of Different Systems of Closed Photobioreactors ................................................... 6

    2.4 Conclusions - Type of Reactor ........................................................................................................... 7

    2.5 Choosing the Right Algae ................................................................................................................... 7

    2.5.1 General Aspects to Consider ....................................................................................................... 7

    2.5.2 Algae Strains with High Oil Content ........................................................................................... 8

    2.5.3 Phaeodactylum tricornutum ........................................................................................................ 8

    2.5.4 Chlorella protothecoides ............................................................................................................. 9

    2.5.5 Botryococcus braunii .................................................................................................................. 9

    2.5.6. Nannochloropsis salin