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
Al Darzins (NREL)
Philip Pienkos (NREL)
Les Edye (BioIndustry Partners)
Report T39-T2. 6 August 2010
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
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
IEA Bioenergy Task 39; Liquid Biofuels
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.
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
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
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.
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