current status and potential for algal biofuels

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  • Report T39-T2 6 August 2010

    Current Status and Potential for

    Algal Biofuels Production

    A REPORT TO IEA BIOENEGY TASK 39

    AUTHORS:

    Al Darzins (NREL)

    Philip Pienkos (NREL)

    Les Edye (BioIndustry Partners)

    Report T39-T2. 6 August 2010

  • Background

    One of the activities of IEA Bioenergy Task 39 is to commission state-of-the-art

    reports on some of the most important relevant clean energy, liquid biofuels

    technology topics. You can access many Task 39 past reports at www.Task39.org

    One area that has received considerable recent attention is the potential of algae

    to produce low carbon energy dense liquid biofuels suitable for uses such as

    aviation, or as petrol/gasoline and diesel replacements.

    IEA Bioenergy Task 39 is fortunate to have, within its extensive network,

    colleagues who have had long experience with algae technologies, both in terms

    of commercial growth of algae (as has occurred in Australia over many years of

    operating high-productivity open ponds) and in assessing the technical status and

    potential of algal biofuels (as carried out by the United States National

    Renewable Energy Laboratory (NREL) during the Aquatic Species Program).

    We want to thank the authors, Al Darzins and Philip Pienkos (NREL, US) and Les

    Edye (BioIndustry Partners, Australia) for their hard work in writing this report!

    Contributions of text and figures were provided by Wade Amos, John Benemann,

    Eric Jarvis, John Jechura, Anelia Milbrant, Matt Ringer, Kristi Theis, and Bob

    Wallace.

    We also want to thank Don OConnor of (S&T)2 Consultants Inc. for the final

    editing and layout of this report as well all the Task 39 member Country

    Representatives and IEA Bioenergy Executive Committee members for providing

    excellent constructive feedback on initial drafts of the report.

    With algal biofuels research and development evolving rapidly, we are confident

    that areas such as technical approach, process scale-up/commercial

    demonstration, life cycle/sustainability analysis, etc., of algal systems for liquid

    biofuels production will warrant further extended examination in the future. Such

    work will likely become one focus of future IEA Bioenergy Task 39 activities.

    Jack Saddler/Jim McMillan

    Co-Task Leaders

    IEA Bioenergy Task 39; Liquid Biofuels

    www.Task39.org

    http://www.task39.org/http://www.task39.org/

  • i

    Current Status and Potential for Algal

    Biofuels Production Executive Summary

    This IEA Bioenergy report, Current Status and Potential for Algal Biofuels

    Production, seeks to examine the technical and economic feasibility of generating

    algal biomass for the production of liquid biofuels.

    As worldwide petroleum reserves diminish due to consumption exceeding

    discoveries, many countries are becoming increasingly dependent upon imported

    sources of oil. The United States, for example, currently imports a full two-thirds

    of its petroleum from only a few countries around the world. The demand for

    energy is growing worldwide especially in many of the rapidly developing

    countries such as in China and India. Furthermore, the continued combustion of

    fossil fuels has created serious environmental concerns over global warming due

    to the increased release of greenhouse gases (GHG).

    Biofuels are one of the potential options to reduce the worlds dependence on

    fossil fuels but biofuels have their limitations. One of the recent concerns with

    respect to increased biofuels production is the availability of land. It is recognized

    that the GHG benefits of biofuels can be offset if land with existing high carbon

    intensity is cleared for the production of biofuel feedstocks. Biofuels that could be

    produced without large increases in arable land or reductions in tropical

    rainforests could be very attractive in the future. Algae may offer this opportunity.

    The basic concept of using algae as a renewable feedstock for biofuels production

    has been known for many years. All of the elements for the production of lipid-

    based fuels from algae have been demonstrated.

    Algae can be grown in large outdoor cultures and harvested.

    The algal biomass will contain a certain percentage of lipids, though not

    necessarily all in the form of triacylglycerides (TAGs).

    Algal oil can be obtained from harvested biomass by known means, albeit

    with sub optimal yield, cost and thermodynamic efficiencies.

    Biodiesel (fatty acid methyl ester, FAME), hydrogenation-derived renewable

    diesel (HDRD) and synthetic jet fuel production from algal oil have been

    demonstrated at non-commercial scales.

    However, past research and development funding in this field has been

    inadequate to facilitate the development of a robust algal biofuels industry.

  • ii

    Realizing the strategic potential of algal feedstocks will require breakthroughs, not

    only in algal mass culture and downstream processing technologies, but also in

    the fundamental biology related to algal physiology and the regulation of algal

    biochemical pathways.

    Potential Benefits of Microalgal Oil Production

    Microalgae include a wide variety of photosynthetic microorganisms capable of

    fixing CO2 from the atmosphere and water to produce biomass more efficiently

    and rapidly than terrestrial plants. Numerous algal strains have been shown in the

    laboratory to produce more than 50 percent of their biomass as lipid with much of

    this as triacylglycerides (TAGs), also called triglycerides, the anticipated starting

    material for biodiesel fuels. Most of the observations of high lipid content come

    from algal cultures grown under nutrient (especially nitrogen, phosphorous, or

    silicon) limitation. Lipid content varies in both quantity and quality with varied

    growth conditions. While high lipid yields can be obtained under nutrient

    limitation, this is generally at the expense of reduced biomass yields.

    Nevertheless, the possibility that microalgae could generate considerably more oil

    than typical oilseed crops is an exciting opportunity.

    An additional benefit of growing algae as a biofuels feedstock is that they can be

    cultivated on otherwise non-productive (i.e., non-arable) land that is unsuitable

    for agriculture or in brackish, saline, and waste water that has little competing

    demand, offering the prospect of a biofuel that does not further tax already

    limited resources. Using algae to produce feedstocks for biofuels production could

    have little impact on the production of food and other products derived from

    terrestrial crops, but will utilize water resources, which will need a life cycle

    assessment to identify areas for sustainable production.

    Algae have the potential to reduce the generation of greenhouse gas (GHG) and

    to recycle CO2 emissions from flue gases from power plant and natural gas

    operations as indicated by preliminary life cycle assessments. In the future, an

    algal-based biorefinery could potentially integrate several different conversion

    technologies to produce biofuels including biodiesel, green diesel and green

    gasoline1 (generated by catalytic hydroprocessing and catalytic cracking of

    vegetable oils, respectively), aviation fuel (commercial and military), ethanol, and

    methane, as well as valuable co-products including oils, protein, and

    carbohydrates.

    1 Gasoline, jet fuel, and diesel are generally described as renewable or green if the

    feedstock material is derived from a biological source (such as biomass or plant oil) but

    has essentially the same chemical composition as that of crude oil.

  • iii

    Algal Cultivation

    There are currently no meaningful amounts of microalgal biofuels produced

    commercially in the world. Approximately 9,000 tonnes of algal biomass is

    produced commercially today, mainly for the production of high-value, low-

    volume food supplements and nutraceuticals. In the U.S., three companies are

    responsible for the majority of commercial production. Two of these (Earthrise

    Nutritionals, LLC, in California, and Cyanotech Corp., in Hawaii) use raceway

    ponds for production. The third company (Martek Co., in Maryland) produces

    biomass by fermentation, in which the algae are grown in closed vessels on

    sugars in the dark, similar to yeast production. Cognis Australia Pty Ltd produce

    -carotene from D. salina harvested from hypersaline extensive ponds in Hutt

    Lagoon and Whyalla. Hutt Lagoon has a total pond surface area of ca. 520 ha and

    Whyalla is ca. 440 ha. In terms of pond surface area, Hutt Lagoon and Whyalla

    are among the largest algal production systems in the world.

    Proposed commercial algal biofuels production facilities employ both open (ponds)

    and closed (tubes, also known as photobioreactors) cultivation systems. Each of

    these has advantages and disadvantages, but photobioreactors are much more

    expensive to build than open ponds. Photobioreactors have not been engineered

    to the extent of other bioreactors in commercial practice, and so there is certainly

    room for cost reductions. Neither open ponds nor closed photobioreactors are

    mature technologies. Until large-scale systems have actually bee

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