BIOMASS PROGRAM

National Algal Biofuels
Technology Roadmap

MAY 2010

National Algal Biofuels
Technology Roadmap
A technology roadmap resulting from the National Algal Biofuels Workshop
December 9-10, 2008
College Park, Maryland
Workshop and Roadmap sponsored by the U.S. Department of Energy
Office of Energy Efficiency and Renewable Energy
Office of the Biomass Program
Publication Date: May 2010
John Ferrell
Office of Energy Efficiency
and Renewable Energy
Office of the Biomass Program(202)586-5340
john.ferrell@ee.doe.gov

Valerie Sarisky-Reed
Office of Energy Efficiency
and Renewable Energy
Office of the Biomass Program(202)586-5340
valerie.sarisky-reed@ee.doe.gov

Roadmap Editors:
Daniel Fishman, Rajita Majumdar,1 Joanne Morello,2 Ron Pate,3 and Joyce Yang2
1

Workshop Organizers:
Al Darzins, Grant Heffelfinger, Ron Pate, Leslie Pezzullo,2 Phil Pienkos,4 Kathy Roach,5 Valerie Sarisky-Reed,2 and the
Oak Ridge Institute for Science and Education (ORISE)
4

3

3

A complete list of workshop participants and roadmap contributors is available in the appendix.
Suggested Citation for This Roadmap:
U.S. DOE 2010. National Algal Biofuels Technology Roadmap. U.S. Department of Energy, Office of Energy Efficiency and
Renewable Energy, Biomass Program.
Visit http://biomass.energy.gov for more information
BCS, Incorporated 2Office of the Biomass Program 3Sandia National Laboratories

1

National Renewable Energy Laboratory 5MurphyTate LLC

4

This report is being disseminated by the Department of Energy. As such, the document
was prepared in compliance with Section 515 of the Treasury and General Government
Appropriations Act for Fiscal Year 2001 (Public Law No. 106-554) and information
quality guidelines issued by the Department of energy. Further, this report could be“influential scientific information” as that term is defined in the Office of Management
and Budget’s Information Quality Bulletin for Peer Review (Bulletin). This report has
been peer reviewed pursuant to section II.2 of the Bulletin.

Preface
Welcome to the U.S. Department of Energy (DOE) Biomass Program’s National Algal Biofuels Technology
Roadmap. Prepared with the input of more than 200 scientists, engineers, industry representatives, research
managers, and other stakeholders, this document represents the synthesis of the Biomass Program’s National Algal
Biofuels Technology Roadmap Workshop, comments gathered during a public comment period, and supporting
scientific literature. This Roadmap is intended to summarize the state of technology for algae-based fuels anddocument the research and development challenges associated with producing them at a commercial scale.
Renewable energy lies at the intersection of some of our nation’s most pressing issues: our energy security, oureconomic wellbeing, and the stability of our global climate. These national challenges require near-term solutions
as well as investments in nascent technologies that show promise for the future. Therefore, while DOE works to
deploy renewable energy and energy-efficient projects across the country today, it remains committed to fostering
technologies that could yield substantial benefits over time. Achieving cost-competitive, sustainable algal biofuels
will entail years of research and careful planning, but their significant potential to serve as renewable transportation
fuels warrants our thorough consideration of what efforts are necessary to make them a commercial-scale reality.
DOE has recently revived its investment in algal biofuels in response to the increased urgency of loweringgreenhouse gas emissions and producing affordable, reliable energy, as well as the recognition that we will not
likely achieve these goals via one technology pathway. Through appropriated dollars and the American Recovery
and Reinvestment Act of 2009, DOE is investing in a variety of research, development, and demonstration (RD&D)
projects that seek to tackle key technical hurdles associated with commercializing algal biofuels. Meanwhile, otherfederal agencies, private companies, and the academic community are also increasing their efforts to optimize andcommercialize this renewable energy source.
This Roadmap lays the groundwork for identifying challenges that will likely need to be surmounted for algae andcyanobacteria to be used in the production of economically viable, environmentally sound biofuels. It is intended toserve as a resource for researchers, engineers, and decision-makers by providing a summary of progress to date anda direction for future algae RD&D activities, and we hope it fosters and informs participation from existing and new
stakeholders as the next steps are taken to advance algal biofuels. DOE looks forward to continuing its work withdiverse partners in evaluating renewable energy options and facilitating development of those that carry the greatest
benefits today and in the years to come.

Valerie Sarisky-Reed
Acting Manager, Biomass Program
U.S. Department of Energy

PrefaceiExecutive Summary“”

Developing the next generation of biofuels is key to oureffort to end our dependence on foreign oil and address theclimate crisis – while creating millions of new jobs that can’t
be outsourced— Secretary of Energy Steven Chu at the White House
ceremony on May 5, 2009, announcing $800
million in new biofuel research activitiesIn recent years, biomass-derived fuels have received
increasing attention as one solution to our nation’s
continued and growing dependence on imported
oil, which exposes the country to the risk of critical
disruptions in fuel supply, creates economic and social
uncertainties for businesses and individuals, and impacts
our national security. The Energy Independence andSecurity Act of 2007 (EISA) established a mandatory
Renewable Fuel Standard (RFS) requiring transportationfuel sold in the U.S. to contain a minimum of 36 billion
gallons of renewable fuels, including advanced andcellulosic biofuels and biomass-based diesel, by 2022.
While cellulosic ethanol is expected to play a large rolein meeting the EISA goals, a number of next generation
biofuels show significant promise in helping to achieve
the goal. Of these candidates, biofuels derived from algae
have the potential to help the U.S. meet the new RFS
while at the same time moving the nation ever closer toenergy independence. To accelerate the deployment ofadvanced biofuels, President Obama and Secretary ofEnergy Steven Chu announced the investment of $800M
in new research on biofuels in the American Recovery
and Renewal Act. This announcement included funds
for the Department of Energy (DOE) Office of Energy
Efficiency and Renewable Energy’s (EERE) Biomass
Program to invest in the research, development, anddeployment of commercial algae-to-biofuel processes.
Additional funding is being directed to algae-to-biofuel
research both in EERE and other government agencies
and programs.
The term algae can refer to microalgae, cyanobacteria(the so called “blue-green algae”), and macroalgae (orseaweed). Under certain conditions, some microalgae
have the potential to accumulate significant amountsof lipids (more than 50% of their ash-free cell dry
weight). These characteristics give great potential for
an immediate pathway to high energy density, fungible
fuels. These fuels can also be produced using other algae
feedstocks and intermediates, including starches andii

Executive Summary

A culture of the microalgae Botryococcus. Photo courtesy of theProvasoli-Guillard National Center for Culture of Marine Phytoplankton(CCMP).

sugars from cyanobacteria and macroalgae. In addition
to fungible biofuels, a variety of different biofuels andproducts can be generated using algae precursors.
There are several aspects of algal biofuel production thathave combined to capture the interest of researchers andentrepreneurs around the world. These include:1) high per-acre productivity, 2) non-food based
feedstock resources, 3) use of otherwise non-productive,
non-arable land, 4) utilization of a wide variety of water
sources (fresh, brackish, saline, marine, produced, andwastewater), 5) production of both biofuels and valuable
co-products, and 6) potential recycling of CO2 and othernutrient waste streams.
The DOE-supported Aquatic Species Program, an effort
undertaken from 1978 to 1996, illustrated the potentialof algae as a biofuel feedstock. Much has changed since
the end of the program. Rising petroleum prices and anational mandate to reduce U.S. dependence on foreignoil, provide environmental benefits, and create economic
opportunities across the nation have renewed interest in
developing algal feedstocks for biofuels production.
While the basic concept of using algae as an alternativeand renewable source of biomass feedstock for biofuels
has been explored previously, a scalable, sustainable
and commercially viable system has yet to emerge.
The National Algal Biofuels Technology Roadmap
Workshop, held December 9-10, 2008, was convened
by DOE-EERE’s Biomass Program. The two-day event
brought together more than 200 scientists, engineers,research managers, industry representatives, lawyers,financiers, and regulators from across the country to
discuss and identify the critical challenges currently
hindering the economical production of algal biofuels at
commercial scale.
This document represents the output from the Workshop,
supporting scientific literature, and comments received
during a public comment period. The Roadmap
document is intended to provide a comprehensive stateof technology summary for fuels and co-products fromalgal feedstocks and to document the feasibility andtechno-economic challenges associated with scaling
up of processes. This document also seeks to explore
the economic and environmental impacts of deploying

algal biomass production systems at commercial
scale. By documenting the challenges across the algal
biomass supply chain and highlighting research andcoordination needs and gaps, this document will serve to
guide researchers and engineers, policymakers, federal
agencies, and the private sector in implementing national
research, development, and deployment efforts.
In summary, the Roadmap Workshop effort suggeststhat many years of both basic and applied science andengineering will likely be needed to achieve affordable,scalable, and sustainable algal-based fuels. The ability
to quickly test and implement new and innovativetechnologies in an integrated process will be a key
component to accelerating progress.

Executive Summary

iii

FROM
ALGAE
TO TO
BIOFUELSFROM
ALGAE
BIOFUELSAn Integrated
Systems
Approach
to Renewable
Energythat isAn Integrated
Systems
Approach
to Renewable
E nergy
ALGAE FEEDSTOCKSCULTIVATION
Microalgae and cyanobacteria can be cultivated via
photoautotrophic methods (where algae require light togrow and create new biomass) in open or closed ponds or via
heterotrophic methods (where algae are grown without lightand are fed a carbon source, such as sugars, to generate new
biomass). Macroalgae (or seaweed) has different cultivationneeds that typically require open off-shore or coastal facilities.
Designing an optimum cultivation system involves leveraging
the biology of the algal strain used and inegrating it with thebest suited downstream processing options. Choices made forthe cultivation system are key to the affordability, scalability,
and sustainability of algae to biofuel systems.

Fermentation Tanks
MICROALGAECYANOBACTERIA

MACROALGAE

Closed Photobioreactors

Algae as feedstocks for bioenergy refers to a diverse group oforganisms that include microalgae, macroalgae (seaweed),and cyanobacteria (formerly called “blue-green algae”).
Algae occur in a variety of natural aqueous and terrestial
habitats ranging from freshwater, brackish waters, marine,and hyper-saline environments to soil and in symbiotic
associations with other organisms.
Understanding, managing, and taking advantage of thebiology of algal strains selected for use in production
systems is the foundation for processing feedstocks into
fuels and products. Isolating new strains directly from uniqueenvironments will ensure versatile and robust strains for massculture needed in biofuels applications.

Open Ponds
Example Cultivation Systems

iv

POLICY

Executive Summary

SITING AND RESOURCES

Development
Path TowardaSystems and Techno-Economic Analysis: Guiding
the ResearchandAbundant, Affordable, and Sustainable

2-O-C

CONVERSIONHARVESTING / DEWATERING
Some processes for the conversion of algae to liquidtransportation fuels require pre-processing steps such as
harvesting and dewatering. Algal cultures are mainly grownin water and can require process steps to concentrate
harvested algal biomass prior to extraction and conversion.
These steps can be energy-intensive and can entail siting
issues.

EXTRACTIONO
CH2-O-C

R1

O
CH-O-C

R2O
CH2-O-C

R3

Conversion to fuels and products is predicated on a basic
process decision point:
1) Conversion of whole algal biomass;
2) Extraction of algal metabolites; or
3) Processing of direct algal secretions.
Conversion technology options include chemical,
biochemical, and thermochemical processes, or a
combination of these approaches.
The end products vary depending on the conversion
technology utilized. Focusing on biofuels as the end-productposes challenges due to the high volumes and relative low
values associated with bulk commodities like gasoline anddiesel fuels.

Bio-Crude

Algal Lipid: Precursor to Biofuels
Three major components can be extracted from algal
biomass: lipids (including triglycerides and fatty acids),
carbohydrates, and proteins. While lipids and carbohydrates
are fuel precursors (e.g., gasoline, biodiesel and jet fuel),
proteins can be used for co-products (e.g., animal/fishfeeds).
Most challenges in extraction are associated with theindustrial scale up of integrated extraction systems.
While many analytical techniques exist, optimizing
extraction systems that consume less energy thancontained in the algal products is a challenge due to thehigh energy needs associated with both handling anddrying algal biomass as well as separating out desirable
products. Some algal biomass production processes areinvestigating options to bypass extraction, though these arealso subject to a number of unique scale-up challenges.

End Uses:• Biodiesel• Biogas• Renewable Hydrocarbons• Co-products(e.g., animal feed, fertilizers,
industrial enzymes,
bioplastics, and surfactants)• Alcohols

REGULATIONS AND STANDARDS

Commercially Viable Algal Biofuel Industry

Executive Summaryv

vi

Executive Summary

Contents
1. Overview....................................................................................................................................1
About the Roadmap................................................................................................................................................1
1.1 America’s Energy Challenges..............................................................................................................................1
Advantages of Algal Feedstocks.......................................................................................................................3
1.2 A History of Domestic Algal Biofuels Development................................................................................3
Early Work to 1996..................................................................................................................................................3
Research from 1996 to Present..........................................................................................................................5
1.3 Algae-to-Biofuels: Opportunity and Challenges Today...........................................................................5
Technology and Analysis Challenges...............................................................................................................5
Regulations and Standards..................................................................................................................................7
Public-Private Partnerships.................................................................................................................................7
References..................................................................................................................................................................7
2. Algal Biology............................................................................................................................8
2.1 Strain Isolation, Screening and Selection ....................................................................................................8
Isolation and Characterization of Naturally Occurring Algae ...............................................................8
Role of Culture Collections as National Algae Data Resource Centers..............................................9
Selecting Algal Model Systems for Study....................................................................................................10
2.2 Algal Physiology and Biochemistry.............................................................................................................. 11
Photosynthesis and Light Utilization...............................................................................................................11
Carbon Partitioning and Metabolism...............................................................................................................11
Algal Carbohydrates............................................................................................................................................. 12
Lipid Synthesis and Regulation........................................................................................................................ 12
Biohydrogen ........................................................................................................................................................... 15
2.3 Algal Biotechnology........................................................................................................................................... 16
The Genetic Toolbox............................................................................................................................................. 16
Enabling Technologies: “Omics” Approaches and Bioinformatics..................................................... 19
Applications of Biotechnology to Algal Bioenergy.................................................................................20
Considerations of Genetic Modifications..................................................................................................... 22
References............................................................................................................................................................... 23
3. Algal Cultivation.....................................................................................................................29
3.1 Cultivation Pathways........................................................................................................................................... 29
Microalgae and Cyanobacteria........................................................................................................................ 29
Macroalgae..............................................................................................................................................................30
3.2 Scale-Up Challenges.......................................................................................................................................... 31
Stability of Large-Scale Cultures . ................................................................................................................. 31
Contentsvii

System Productivity............................................................................................................................................. 32
Nutrient Sources, Sustainability, and Management................................................................................ 32
Water Management, Conservation, and Recycling................................................................................. 33
References............................................................................................................................................................... 35
4. Downstream Processing: Harvesting and Dewatering......................................................... 37
4.1 Approaches for Microalgae..............................................................................................................................37
Harvesting.................................................................................................................................................................37
Drying........................................................................................................................................................................ 38
4.2 Approaches for Macroalgae ......................................................................................................................... 38
Harvesting................................................................................................................................................................ 38
Preprocessing......................................................................................................................................................... 39
4.3 Systems Engineering . ..................................................................................................................................... 39
References...............................................................................................................................................................40
Preliminary Look at Energy Balance ............................................................................................................40
5. Extraction of Products from Algae . .....................................................................................42
5.1 Current Practices for Lipid Extraction......................................................................................................... 42
Mechanical Disruption (i.e., Cell Rupture)................................................................................................... 42
Organic Co-solvent Mixtures............................................................................................................................ 43
Accelerated Solvent Extraction.......................................................................................................................44
Selective Extraction.............................................................................................................................................44
Subcritical Water Extraction............................................................................................................................. 45
Supercritical Fluid Extraction........................................................................................................................... 45
Heterotrophic Production................................................................................................................................. 45
5.2 Challenges.............................................................................................................................................................46
References...............................................................................................................................................................46
6. Algal Biofuel Conversion Technologies ...............................................................................48
6.1 Direct Production of Biofuels from Algae.................................................................................................48
Alcohols.................................................................................................................................................................... 49
Alkanes...................................................................................................................................................................... 49
Hydrogen.................................................................................................................................................................50
6.2 Processing of Whole Algae............................................................................................................................50
Pyrolysis....................................................................................................................................................................50
Gasification............................................................................................................................................................... 51
Liquefaction............................................................................................................................................................ 52
Supercritical Processing..................................................................................................................................... 53
Anaerobic Digestion of Whole Algae............................................................................................................ 53
6.3 Conversion of Algal Extracts......................................................................................................................... 53
Chemical Transesterification............................................................................................................................ 54
viii

Contents

Biochemical (Enzymatic) Conversion........................................................................................................... 55
Catalytic Cracking................................................................................................................................................. 55
Conversion to Renewable Diesel, Gasoline, and Jet Fuel .................................................................... 56
6.4 Processing of Algal Remnants after Extraction......................................................................................57
References............................................................................................................................................................... 58
7. Co-products . ......................................................................................................................... 61
7.1 Commercial Products from Microalgae and Cyanobacteria................................................................ 61
7.2 Commercial Products from Macroalgae....................................................................................................64
7.3 Potential Options for the Recovery of Co-products.............................................................................64
References............................................................................................................................................................... 67
8. Distribution and Utilization...................................................................................................69
8.1 Distribution............................................................................................................................................................ 69
8.2 Utilization.............................................................................................................................................................. 70
Algal Blendstocks to Replace Middle-Distillate Petroleum Products............................................... 70
Algal Blendstocks for Alcohol and Gasoline-Range Petroleum Products........................................71
References................................................................................................................................................................72
9. Resources and Siting ........................................................................................................... 73
9.1 Resource Requirements for Different Cultivation Approaches........................................................ 73
Photoautotrophic Microalgae Approach......................................................................................................73
Heterotrophic Microalgae Approach.............................................................................................................74
Photoautotrophic Macroalgae Approach.....................................................................................................74
9.2 Resources Overview...........................................................................................................................................75
Climate . ....................................................................................................................................................................75
Water..........................................................................................................................................................................77
Carbon Dioxide......................................................................................................................................................80
Land............................................................................................................................................................................ 81
9.4 Integration with Water Treatment Facilities .......................................................................................... 83
Wastewater Treatment and Recycling Applications............................................................................... 83
Algae Production Techniques for Wastewater Treatment Plants...................................................... 84
Main Research Needs for Algae Production with Wastewater ......................................................... 86
9.5 Co-location of Algal Cultivation Facilities with CO2-Emitting Industries..................................... 86
The Opportunity in Co-Locating with CO2-Emitting Sources.............................................................. 87
Barriers to Co-Location of Algae Production with Stationary Industrial CO2 Sources ............ 88
Directions for Research and Development................................................................................................. 88
References...............................................................................................................................................................90

Contentsix

10. Systems and Techno-Economic Analysis............................................................................93
10.1 Objectives of Techno-Economic Analysis .............................................................................................. 93
10.2 TEA Scope and Methods...............................................................................................................................94
10.3 Suggestions for TEA and LCA Approach (Workshop Results and Discussion)...................... 97
10.4 Systems Analysis..............................................................................................................................................99
Overview..................................................................................................................................................................99
Engineering Analyses and GIS Assessments........................................................................................... 100
Impact of Geographic Variability of Inputs on Algal Biofuel Production Costs..........................102
Life Cycle Analysis.............................................................................................................................................. 104
10.5 Algae Production Costs and Uncertainties.......................................................................................... 104
10.6 Preliminary System Dynamics Modeling ............................................................................................. 104
10.7 Potential Directions for R&D Effort ........................................................................................................ 105
11. Public-Private Partnerships ............................................................................................... 109
11.1 The Benefits of Algal Biofuels Public-Private Partnerships............................................................ 109
11.2 Components of Successful Public-Private Partnerships....................................................................110
11.3 Forums for Public-Private Partnerships....................................................................................................11011.4 Partnership Challenges in the Algal Biofuels Industry........................................................................ 111
11.5 Modeling Partnerships for Technology Development.......................................................................... 111
References...............................................................................................................................................................114
Appendices ............................................................................................................................. 115
Appendix 1 : Workshop Participants...................................................................................................................115
Appendix 2: Contributors.......................................................................................................................................122
Appendix 3: Respondents to Request for Information on the Draft Roadmap...............................124x

Contents

1. Overview
The Biomass Program (Program) of the U.S. Departmentof Energy (DOE) Office of Energy Efficiency and
Renewable Energy is committed to advancing the visionof a viable, sustainable domestic biomass industry that
produces renewable biofuels, bioproducts and biopower,
enhances U.S. energy security, reduces our dependenceon oil, provides environmental benefits, and creates
economic opportunities across the nation. The Program’s
goals are driven by various federal policies and laws,
including the Energy Independence and Security Act
of 2007. To accomplish its goals, the Program has
undertaken a diverse portfolio of research, development,
and deployment (RD&D) activities, in partnershipwith national laboratories, academia, and industry.
Algal biofuels offer great promise in contributing to
the Program’s vision, as well as helping to meet the
Renewable Fuels Standard (RFS) mandate establishedwithin EISA. The RFS mandates blending of 36 billion
gallons of renewable fuels by 2022, of which only 15
billion gallons can be produced from corn-based ethanol.
Biofuels derived from algae can meet these l onger-term
needs of the RFS and represent a significant opportunity
to impact the U.S. energy supply for transportation
fuels. Despite their potential, the state of technology
for producing algal biofuels is regarded by many inthe field to be in its infancy and there is a considerable
amount of RD&D is needed to achieve affordable,scalable, and sustainable algal-based biofuels.

About the Roadmap
The framework for National Algal Biofuels Technology
Roadmap was constructed at the Algal Biofuels
Technology Roadmap Workshop, held December 9-10,
2008, at the University of Maryland-College Park. The
Workshop was organized by the Biomass Program to
discuss and identify the critical challenges currently
hindering the development of a domestic, commercialscale algal biofuels industry. A major objective of theWorkshop was to gather the necessary information
to produce an algal biofuels technology roadmap
that both assesses the current state of technology andprovides direction to the Program’s RD&D efforts.
More than 200 stakeholders were convened at theWorkshop, representing a diverse range of expertise fromindustry, academia, the national laboratories, government
agencies, and non-governmental organizations. The
Workshop provided a stimulating environment to explore
topics affecting the development of algal biofuels industry.

The Workshop was able to capture the participants’experience and expertise during a series of technicalbreak-out sessions that spanned critical aspects of thealgal biomass supply chain and cross-cutting issues.
The outcomes from the Workshop provided key inputs
to the development of this Algal Biofuels Technology
Roadmap. The full proceedings of the Workshop canbe found at http://www.orau.gov/algae2008pro/.
Following the release of the initial draft of the Roadmap,
a 60-day public comment period was held to allow
Workshop participants to evaluate the Roadmap for
fidelity and incorporate new information, viewpoints,
and criticisms not captured during the Workshop. Allcomments are noted in the Appendix of this document.
Every attempt was made to ensure that the Roadmap
development process was transparent and inclusive.
This Roadmap presents information from a scientific,
economic, and policy perspectives that can support
and guide RD&D investment in algal biofuels. Whileaddressing the potential economic and environmental
benefits of using algal biomass for the production ofliquid transportation fuels, the Roadmap describes
the current status of algae RD&D. In doing so, it lays
the groundwork for identifying challenges that likely
need to be overcome for algal biomass to be used in
the production of economically viable biofuels.

1.1 America’s Energy Challenges
As global petroleum supplies diminish, the UnitedStates is becoming increasingly dependent upon foreignsources of crude oil. The United States currently imports
approximately two-thirds of its petroleum, 60% of
which is used for producing transportation fuels. The
rising energy demand in many rapidly developing
countries around the world is beginning to create
intense competition for the world’s dwindling petroleum
reserves. Furthermore, the combustion of petroleumbased fuels has created serious concerns about climatechange from the greenhouse gas (GHG) emissions.
In 2007, the Energy Independence and Security Act(EISA) was enacted, which set new standards forvehicle fuel economy, as well as made provisions that
promote the use of renewable fuels, energy efficiency,
and new energy technology research and development.
The legislation establishes production requirements fordomestic alternative fuels under the Renewable Fuels
Standard (RFS) that increase over time (Exhibit 1.1).
1. Overview

1Advanced biofuels face significant challenges in meetingthe ambitious targets set by EISA. As required by EISA,
advanced biofuels must demonstrate GHG emissions
across their life cycle that are at least 50% less than GHG
emissions produced by petroleum-based transportation
fuels. Significant acreage and productivity will be requiredfor biomass production to generate sufficient feedstock
to meet the RFS mandates. Cellulosic feedstocks wereidentified by the Billion Ton Study as a significant sourceof biomass (Perlack et al., 2005). However, the study
did not explore the potential of algae, while algae may
offer comparable biomass productivity as lignocellulosic
feedstocks – the key biomass resource factored in the study.
Many pathways are currently under consideration for
production of biofuels and bioproducts from componentsof biomass. The most promising among these are routes
to advanced biofuels such as high energy density fungible
fuels for aviation and ground transport. Algal biomass may
offer significant advantages that complement traditional
feedstocks towards these fuels. For example, oleaginous

UNIQUE ADVANTAGES OF ALGAL FEEDSTOCK FOR
ADVANCED BIOFUELS• High area productivity• Minimizes competition with conventional agriculture• Utilizes a wide variety of water sources• Recycles stationary emissions of carbon dioxide• Compatible with integrated production of fuels andco-products within biorefineries

microalgae have demonstrated potential oil yields thatare significantly higher than the yields of oilseed crops(Exhibit 1.2). Potential oil yields from certain algae
strains are projected to be at least 60 times higher thanfrom soybeans, approximately 15 times more productive
than jatropha, and approximately 5 times that of oil palm
per acre of land on an annual basis (Rodolfi et al., 2009).

Exhibit 1.1 Renewable Fuel Standard volume requirements (billion gallons)

Cellulosic biofuels and biomass-based diesel are included in the advanced biofuel requirement.

ab

CELLULOSICBIOFUELREQUIREMENT

BIOMASS-BASEDDIESELREQUIREMENTADVANCED BIOFUELREQUIREMENTTOTAL RENEWABLE
FUEL REQUIREMENT

2009

N/A

0.5

0.6

11.1

2010

0.1

0.65

0.95

12.95

2011

0.25

0.80

1.35

13.95

2012

0.5

1.0

2.0

15.2

2013

1.0

a

2.75

16.55

2014

1.75

a

3.75

18.15

2015

3.0

a

5.5

20.5

2016

4.25

a

7.25

22.25

2017

5.5

a

9.0

24.0

2018

7.0

a

11.0

26.0

2019

8.5

a

13.0

28.0

2020

10.5

a

15.0

30.0

2021

13.5

a

18.0

33.0

2022

16.0

a

21.0

36.0

2023

b

b

b

b

To be determined by EPA through a future rulemaking, but no less than 1.0 billion gallons.
To be determined by EPA through a future rulemaking.

2

1. Overview

Advantages of Algal Feedstocks

Early Work to 1996

Algae can be preferred feedstock for high energy density,
fungible liquid transportation fuels. There are several
aspects of algal biofuel production that have combined tocapture the interest of researchers and entrepreneurs aroundthe world:

Proposals to use algae as a means of producing energy
started in the late 1950s when Meier (1955) and Oswald
and Golueke (1960) suggested the utilization of the
carbohydrate fraction of algal cells for the production of
methane gas via anaerobic digestion. A detailed engineering
analysis by Benemann et al. (1978) indicated that algal
systems could produce methane gas at prices competitive
with projected costs for fossil fuels. The discovery thatmany species of microalgae can produce large amounts oflipid as cellular oil droplets under certain growth conditions
dates back to the 1940s. Various reports during the 1950s
and 1960s indicated that starvation for key nutrients, suchas nitrogen or silicon, could lead to this phenomenon.
The concept of utilizing the lipid stores as a source ofenergy, however, gained serious attention only during
the oil embargo of the early 1970s and the energy pricesurges through the decade; this idea ultimately becamea major push of DOE’s Aquatic Species Program.

• Algal productivity can offer high biomass yields peracre of cultivation.
• Algae cultivation strategies can minimize or avoid
competition with arable land and nutrients used forconventional agriculture.
• Algae can utilize waste water, produced water, andsaline water, thereby reducing competition for limited
freshwater supplies.
• Algae can recycle carbon from CO2-rich flue emissions
from stationary sources, including power plants andother industrial emitters.
• Algal biomass is compatible with the integrated
biorefinery vision of producing a variety of fuels andvaluable co-products.

Exhibit 1.2 Comparison of oil yields from biomass feedstocksa
CROP

a
b

OIL YIELD(GALLONS/ACRE/YR)

Soybean48

Camelina

62

Sunflower

102

Jatropha202

Oil palm

635

Algae

1,000-6,500b

Adapted from Chisti (2007)
Estimated yields, this report

1.2 A History of Domestic
Algal Biofuels Development
The advantages of algae as a feedstock for bioenergy
have been apparent since the mid-twentieth century.
Although, a scalable, commercially viable system has
not yet emerged, earlier studies have laid foundational
approaches to the technologies being explored today.

The Aquatic Species Program represents one of the mostcomprehensive research efforts to date on fuels frommicroalgae. The program lasted from 1978 until 1996
and supported research primarily at DOE’s National
Renewable Energy Laboratory (NREL, formerly the
Solar Energy Research Institute). The Aquatic Species
Program also funded research at many academic
institutions through subcontracts. Approximately $25
million (Sheehan, 1998) was invested during the 18-year
program. During the early years, the emphasis was on
using algae to produce hydrogen, but the focus changed toliquid fuels (biodiesel) in the early 1980s. Advances weremade through algal strain isolation and characterization,
studies of algal physiology and biochemistry, genetic
engineering, process development, and demonstrationscale algal mass culture. Techno-economic analyses
and resource assessments were also important aspectsof the program. In 1998, a comprehensive overview
of the project was completed (Sheehan et al., 1998).
Some of the highlights are described briefly below.
The Aquatic Species Program researchers collected
more than 3,000 strains of microalgae over a seven-year
period from various sites in the western, northwestern,
and southeastern U.S. representing a diversity of aquatic
environments and water types. Many of the strains wereisolated from shallow, inland saline habitats that typicallyundergo substantial swings in temperature and salinity.
The isolates were screened for their tolerance to variations
in salinity, pH, and temperature, and also for their ability
to produce neutral lipids. The collection was narrowed
to the 300 most promising strains, primarily green algae(Chlorophyceae) and diatoms (Bacillariophyceae).

1. Overview

3After promising microalgae were identified, further
studies examined the ability of many strains to induce
lipid accumulation under conditions of nutrient stress.
Although nutrient deficiency actually reduces theoverall rate of oil production in a culture (because of theconcomitant decrease in the cell growth rate), studying
this response led to valuable insights into the mechanismsof lipid biosynthesis. Under inducing conditions, somespecies in the collection were shown to accumulate asmuch as 60% of their dry weight in the form of lipid,
primarily triacylglycerides (TAGs) (Chisti, 2007).
Cyclotella cryptica, an oleaginous diatom, was the focus
of many of the biochemical studies. In this species, growthunder conditions of insufficient silicon (a component of
the cell wall) is a trigger for increased oil production. A
key enzyme is acetyl-CoA carboxylase (ACCase), whichcatalyzes the first step in the biosynthesis of fatty acids used
for TAG synthesis. ACCase activity was found to increase
under the nutrient stress conditions (Roessler, 1988),
suggesting that it may play a role as a “spigot” controlling
lipid synthesis, and thus the enzyme was extensively
characterized (Roessler, 1990). With the advent of the firstsuccessful transformation of microalgae (Dunahay et al.,1995), it became possible to manipulate the expression of
ACCase in an attempt to increase oil yields. These initialattempts at metabolic engineering identified a pathway tomodify the gene encoding in the ACCase enzyme, however,no effect was seen on lipid production in these preliminary
experiments (Jarvis et al., 1999; Sheehan et al., 1998).
Additional studies focused on storage carbohydrate
production, as biosynthesis of these compounds competes
for fixed carbon units that might otherwise be used forlipid formation. For example, enzymes involved in thebiosynthesis of the storage carbohydrate, chrysolaminarin
in C. cryptica were characterized (Roessler, 1987 and1988) with the hope of eventually turning down theflow of carbon through these pathways. The terminationof the Aquatic Species Program in 1996 halted further
development of these potentially promising paths tocommercially viable strains for oil production.
During the course of the Aquatic Species Program
research, it became clear that novel solutions would beneeded for biological productivity and various problematic
process steps. Cost-effective methods of harvestingand dewatering algal biomass and lipid extraction,
purification, and conversion to fuel are critical to successfulcommercialization of the technology. Harvesting is aprocess step that is highly energy- and capital-intensive.
Among various techniques, harvesting via flocculation
was deemed particularly encouraging (Sheehan et al.,1998). Extraction of oil droplets from the cells andpurification of the oil are also cost-intensive steps. The
4

1. Overview

Aquatic Species Program focused on solvent systems, butfailed to fully address the scale, cost, and environmental
issues associated with such methods. Conversion ofalgal oils to ethyl- or methyl-esters (biodiesel) was
successfully demonstrated in the Aquatic Species
Program and shown to be one of the less challenging
aspects of the technology. In addition, other biofuel
process options (e.g., conversion of lipids to gasoline)
were evaluated (Milne et al., 1990), but no further fuelcharacterization, scale-up, or engine testing was carried out.
Under Aquatic Species Program subcontracts,
demonstration-scale outdoor microalgal cultivation
was conducted in California, Hawaii, and New Mexico(Sheehan et al., 1998). Of particular note was the Outdoor
Test Facility in Roswell, New Mexico, operated byMicrobial Products, Inc. (Weissman et al., 1989). Thisfacility utilized two 1,000 m2 outdoor, shallow (10-20 cmdeep), paddlewheel-mixed raceway ponds, plus several
smaller ponds for inocula production. The raceway design
was based on the “high rate pond” system developed at
University of California-Berkeley. The systems weresuccessful in that long-term, stable production of algal
biomass was demonstrated, and the efficiency of CO2
utilization (bubbled through the algae culture) was shown
to be more than 90% with careful pH control. Low
nighttime and winter temperatures limited productivity in
the Roswell area, but overall biomass productivity averaged
around 10 g/m2/day with occasional periods approaching
50 g/m2/day. One serious problem encountered was thatthe desired starting strain was often outgrown by faster
reproducing, but lower oil producing, strains from the wild.
Several resource assessments were conducted under the
Aquatic Species Program. Studies focused on suitable land,saline water, and CO2 resources (power plants), primarily
in desert regions of the Southwest (Maxwell et al., 1985).
Sufficient resources were identified for the productionof many billions of gallons of fuel, suggesting that thetechnology could have the potential to have a significant
impact on U.S. petroleum consumption. However, thecosts of these resources can vary widely depending
upon such factors as land leveling requirements, depthof aquifers, distance from CO2 point sources, and otherissues. Detailed techno-economic analyses underlined
the necessity for very low-cost culture systems, suchas unlined open ponds (Benemann and Oswald, 1996).
In addition, biological productivity was shown to havethe single largest influence on fuel cost. Different cost
analyses led to differing conclusions on fuel cost, buteven with optimistic assumptions about CO2 credits andproductivity improvements, estimated costs for unextracted
algal oil were determined to range from $59 - $186 perbarrel (Sheehan et al., 1998). It was concluded that algal
biofuels would not be cost-competitive with petroleum,
which was trading at less than $20/barrel in 1995.
Overall, the Aquatic Species Program was successful
in demonstrating the feasibility of algal culture as asource of oil and resulted in important advances in thetechnology. However, it also became clear that significant
barriers would need to be overcome in order to achieve
an economically feasible process. In particular, the work
highlighted the need to understand and optimize thebiological mechanisms of algal lipid accumulation and tofind creative, cost-effective solutions for the culture andprocess engineering challenges. Detailed results from theAquatic Species Program research investment are available
to the public in more than 100 electronic documents on
the NREL Web site at www.nrel.gov/publications.
Also from 1968-1990, DOE sponsored the Marine Biomass
Program, a research initiative to determine the technicaland economic feasibility of macroalgae cultivation andconversion to fuels, particularly to substitute natural gas(SNG) via anaerobic digestion (Bird and Benson, 1987).
Primary efforts were focused on open ocean culture of
California kelp. Similar to the findings of the Aquatic
Species Program, researchers concluded that algal-derived
SNG would not be cost-competitive with fossil fuel gas.

Research from 1996 to Present
Since the end of DOE’s Aquatic Species Program in
1996, federal funding for algal research has comefrom DOE, the Department of Defense, the National
Science Foundation, and the Department of Agriculture.
Recent initiatives, such as a major Defense Advanced
Research Projects Agency solicitation, the Air Force
Office of Scientific Research (AFOSR) algal bio-jet
program, and several DOE Small Business Innovative
Research (SBIR) request for proposals, suggest thatfunding levels are beginning to increase. Additionally,
DOE’s Advanced Research Projects Agency-Energy(ARPA-E), Office of Science, Office of Fossil Energy,
and Biomass Program are all funding research activities
that include investigating microalgae, cyanobacteria, andmacroalgae for biofuels and beneficial re-use of CO2.
Additionally, a number of U.S. national labs are
increasingly focusing on algal biofuels research. Statefunding programs and research support from private
industry also make up a significant proportion ofresearch funding. Private investment in algal biofuels
has been increasing at a dramatic rate over the last few
years, significantly outpacing government funding.

Cyclotella cells, Courtesey of CCMP.

1.3 Algae-to-Biofuels:
Opportunity and Challenges
Today
Abundant, affordable, and sustainable feedstocks are thelifeblood of the burgeoning biofuels industry today.
Algae must be considered as part and parcel of thefeedstock mix for producing advanced biofuels. In
contrast to the development of cellulosic biofuels
which benefit from a direct agricultural and processengineering lineage, there is no parallel agricultural
enterprise equivalent for cultivating algae at a similar
scale. A sizable and strategically structured investment
to tackle the challenges of algal biofuels is thus
needed to support commercialization activities.
Based on the information provided at the Workshop, it wasdetermined that a great deal of RD&D is still necessary
to reduce the level of risk and uncertainty associated withthe algae-to-biofuels process so it can be commercialized.
Further, these activities must be accompanied with
conducive developments on the non-technical fronts –regulations and standards, and public-private partnerships.
By reviewing the technology gaps and cross-cutting needs,
the Roadmap aims to guide researchers and engineers,
policymakers, federal agencies, and the private sector
in implementing a nationally coordinated effort toward
developing a viable and sustainable algal biofuel industry.

Technology and Analysis Challenges
This Roadmap seeks to lay down the first comprehensive
state of technology summary for fuels and co-products
from algal feedstocks and to document the feasibility andtechno-economic challenges associated with commercial
scaling up of processes.
1. Overview

5OVERCOMING BARRIERS TO ALGAL BIOFUELS: TECHNOLOGY GOALSFEEDSTOCKFEEDSTOCKPROCESSSTEP

R&D CHALLENGES

Algal Biology• Sample strains from a wide variety of environments for maximum diversity• Develop small-scale, high-throughput screening technologies• Develop open-access database and collections of existing strains with detailed characterization• Investigate genetics and biochemical pathways for production of fuel precursors• Improve on strains for desired criteria by gene manipulation techniques or breeding

Algal
Cultivation• Investigate multiple approaches (i.e., open, closed, hybrid, and coastal/off-shore systems; phototrophic, heterotrophic,
and mixotrophic growth)• Achieve robust and stable cultures at a commercial scale• Optimize system for algal productivity of fuel precursors (e.g., lipids)• Sustainably and cost-effectively manage the use of land, water, and nutrients• Identify and address environmental risks and impacts

INFRASTRUCTURE
INFRASTRUCTURE

CONVERSIONCONVERSION• Investigate multiple harvesting approaches (e.g., sedimentation, flocculation, dissolved air floatation, filtration,
centrifugation, and mechanized seaweed harvesting)
Harvesting and • Minimize process energy intensity
Dewatering• Lower capital and operating costs• Assess each technology option in terms of overall system compatibility and sustainability• Investigate multiple approaches (e.g., sonication, microwave, solvent systems, supercritical fluid, subcriticalwater, selective extraction, and secretion)
Extraction and • Achieve high yield of desired intermediates; preserve co-products
Fractionation • Minimize process energy intensity• Investigate recycling mechanisms to minimize waste• Address scaling challenges, such as operational temperature, pressure, carrying capacity, side reactions, and separations

Fuel
Conversion• Investigate multiple approaches to liquid transportation fuels (e.g., direct fuel production, thermochemical/catalytic
conversion, biochemical conversion, and anaerobic digestion)• Improve catalyst specificity, activity, and durability• Reduce contaminants and reaction inhibitors• Minimize process energy intensity and emissions over the life cycle• Achieve high conversion rates under scale-up conditions

Co-products• Identify and evaluate the co-production of value-added chemicals, energy, and materials from algal remnants(e.g., biogas, animal/fish feeds, fertilizers, industrial enzymes, bioplastics, and surfactants)• Optimize co-product extraction and recovery• Conduct market analyses, including quality and safety trials to meet applicable standards• Characterize algal biomass, intermediates, biofuel, and bioproducts under different storage and transport scenarios forcontamination, weather impacts, stability, and end-product variability
Distribution
and Utilization • Optimize distribution for energy and costs in the context of facility siting• Comply with all regulatory and customer requirements for utilization (e.g., engine performance and material compatibility)

Resources
and Siting• Assess and characterize land, climate, water, energy, and nutrient resource requirements for siting of microalgae(heterotrophic & photoautotrophic) and macroalgae production systems• Integrate with wastewater treatment and/or CO2 emitter industries (in the case of heterotrophic approach)• Address salt balance, energy balance, water & nutrient reuse, and thermal management
PURSUING STRATEGIC R&D: TECHNO-ECONOMIC MODELING AND ANALYSIS

Given the multiple technology and system options and their interdependency, an integrated techno-economic modeling and analysis spanning the entire
algae to biofuels supply chain is crucial in guiding research efforts along select pathways that offer the most opportunity to practically enable a viable
and sustainable algae-based biofuels and co-products industry.

6

1. Overview

Regulations and Standards

Public-Private Partnerships

While the Roadmap’s primary objective is to highlightthe technical challenges and opportunities associatedwith algal biofuels commercialization, it is recognizedthat RD&D activities need to be carried out under aframework of standards, regulation, and policy. Algal
biofuel developers need to foresee and understand thepotentially applicable legal requirements early on in the
research and development process to help ensure algae
are legally and safely developed and the end-products(i.e., biofuels and co-products) comply with applicableconsumption standards. Being a nascent industry, there
are no existing standards for various aspects of algal
biofuels production. However, RD&D activities can informfurther development of applicable laws and standards.

A collaborative framework of public-private partnerships
offers an opportunity to jointly address the technological,
economic, and policy and regulatory challenges as
resolution of these issues will likely require participationfrom multiple entities. However, structuring publicprivate partnerships for successful ventures is a challenge
in itself given the myriad issues and interests, such as
intellectual property rights. Also, supporting education
will be critical to create intellectual talent and theworkforce needed to allow this industry to grow.

References
Benemann, J.R., Pursoff, P. & Oswald, W.J., 1978. Engineering Design and Cost Analysis of a Large-Scale Microalgae Biomass System.
Final Report to the US Energy Department, NTIS# H CP/ T, 1605(UC-61), 91.
Chisti, Y., 2007. Biodiesel from microalgae. Biotechnology Advances, 25(3), 294–306.
Dunahay, T.G., Jarvis, E.E. & Roessler, P.G., 1995. Genetic transformation of the diatoms Cyclotella cryptica and Navicula saprophila.
Journal of Phycology, 31(6), 1004–1011.
Jarvis, E. & Roessler, P., 1999. Isolated gene encoding an enzyme with UDP-glucose pyrophosphorylase and phosphoglucomutase
activities from Cyclotella cryptica - US Patent 5928932 Abstract. Available at: [Accessed November 3, 2009].
Meier, R.L., 1955. Biological cycles in the transformation of solar energy into useful fuels. Solar Energy Research, 179–183.
Milne, T.A., Evans, R.J. & Nagle, N., 1990. Catalytic conversion of microalgae and vegetable oils to premium gasoline, withshape-selective zeolites. Biomass, 21(3), 219-232.
Oswald, W.J. & Golueke, C.G., 1960. Biological transformation of solar energy. Adv. Appl. Microbiol, 11, 223–242.
Perlack, R.D. et al., 2005. Biomass as feedstock for a bioenergy and bioproducts industry: the technical feasibility of a billion-ton
annual supply, ORNL/TM-2006/66, Oak Ridge National Laboratory, Oak Ridge, TN..
Rodolfi, L. et al., 2008. Microalgae for oil: strain selection, induction of lipid synthesis and outdoor mass cultivation in a low-cost
photobioreactor. Biotechnol Bioeng, 102(1), 100–112.
Roessler, P.G., 1988. Effects of silicon deficiency on lipid composition and metabolism in the diatom Cyclotella cryptica.
J. Phycol, 24, 394–400.
Roessler, P.G. & Ohlrogge, J.B., 1993. Cloning and characterization of the gene that encodes acetyl-coenzyme A carboxylase in the alga
Cyclotella cryptica. Journal of Biological Chemistry.

1. Overview

7

2. Algal Biology
The term “algae” commonly refers to a diverse mix oforganisms from different kingdoms of life. Traditionally,
algae have been unified based on their ability to carry out
photosynthesis and live in aquatic habitats. Algae can besingle or multi-cellular and pro- or eukaryotic, and though
they typically live in aquatic environments and are capableof photosynthesis, this is not always the case. Algae include
microalgae (unicellular eukaryotic organisms), macroalgae(seaweeds), and cyanobacteria (historically known as
blue-green algae). Due to their diverse characteristics, thetype and strain of algae being cultivated will ultimately
affect every step of the algae to biofuels supply chain.

2.1 Strain Isolation,
Screening and Selection
Isolation and Characterization of
Naturally Occurring Algae
The goals of algae isolation and screening efforts are to
identify and maintain promising algal specimens forcultivation and strain development. Because it is not yet
known how algae will be cultivated on a mass scale,new strains should be isolated from a wide variety ofenvironments to provide the largest range in metabolic
versatility possible.

Natural Habitats
Algae can be isolated from a variety of natural aqueous
habitats ranging from freshwater to brackish water, marine
and hyper-saline environments, and soil (Round, 1984).
Furthermore, large-scale sampling efforts should becoordinated to ensure broadest coverage of environments
and to avoid duplication of efforts. The selection of
specific locations can be determined by sophisticated site
selection criteria through the combined use of dynamic
maps, Geographic Information Systems (GIS) data andanalysis tools. Ecosystems to be sampled could include
aquatic (i.e., oceans, lakes, rivers, streams, ponds, andgeothermal springs, which includes fresh, brackish,
hypersaline, acidic and alkaline environments) andterrestrial environments in a variety of geographicallocations to maximize genetic diversity. Collection sites
can include public lands as well as various sites within
our national and state park systems. In all cases, questionsof ownership of isolated strains should be considered.
Sampling strategies should not only account for spatial
distribution but also for the temporal succession brought
about by seasonal variations of algae in their habitats.

8

2. Algal Biology

Additionally, within an aqueous habitat, algae are
typically found in planktonic (free floating) and benthic(attached) environments. Planktonic algae may be usedin suspended mass cultures, whereas benthic algae mayfind application in biofilm-based production facilities.

Isolation Techniques
For isolation of new strains from natural habitats,traditional cultivation techniques may be used such asenrichment cultures (Andersen and Kawachi, 2005).
However, some algal strains take weeks to months to
be isolated by traditional methods (for a comprehensive
review of algal culturing techniques, see Anderson,2005). For large-scale sampling and isolation efforts,
high-throughput automated isolation techniques involving
fluorescence-activated cell sorting (FACS) have provento be extremely useful (Sieracki et al., 2004). Because ofmorphological similarities when comparing many algal
species, actual strain identification should be based onmolecular methods such as rRNA sequence comparison, orin the case of closely related strains, other gene markers.

Screening Criteria and Methods
An ideal screen would cover three major areas: growth
physiology, metabolite production, and strain robustness.
The term growth physiology encompasses a numberof parameters such as maximum specific growth rate,
maximum cell density, tolerance to environmental variables(temperature, pH, salinity, oxygen levels, CO2 levels), andnutrient requirements. Because all of these parameters
require significant experimental effort, the developmentof automated systems that provide information regarding
all parameters simultaneously would be helpful.
Screening for metabolite production may involve
determining the cellular composition of proteins, lipids,
and carbohydrates, and measuring the productivity ofthe organism regarding metabolites useful for biofuels
generation. The exact screens employed would dependon the cultivation approaches and fuel precursor desired.
For example, a helpful screen for oil production would
allow for distinction between neutral and polar lipids,
and would provide fatty acid profiles. Furthermore,
many strains also secrete metabolites into the growth
medium. Some of these could prove to be valuable coproducts, and new approaches are needed to develop
screening methods for extracellular materials.

For mass culture of a given algal strain, it is also
important to consider the strain’s robustness, which
includes parameters such as culture consistency,
resilience, community stability, and susceptibility to
predators present in a given environment. Previous
studies revealed that algae strains tested in the laboratory
do not always perform similarly in outdoor masscultures (Sheehan et al., 1998). Therefore, to determine
a strain’s robustness, small-scale simulations of massculture conditions will need to be performed. The
development of small-scale but high-throughput screening
technologies is an important step in enabling the testingof hundreds to thousands of different algal isolates.
At this time, the bottleneck in screening large numbers ofalgae stems from a lack of high-throughput methodologies
that would allow simultaneous screening of multiple
phenotypes, such as growth rate and metabolite
productivity. Solvent extraction, for example, is the mostcommon method for determination of lipid content in algae,
but it requires a significant quantity of biomass (Ahlgren etal., 1991; ) (Bligh and Dyer, 1959). Fluorescent methods
using lipid-soluble dyes have also been described, andthough these methods require much less biomass (as little
as a single cell), it has not yet been established if thesemethods are valid across a wide range of algal strains (Elsey
et al., 2007; de la Jara et al., 2003). Further improvements
in analytical methodology could be made through thedevelopment of solid-state screening methods. Not only
are rapid screening procedures necessary for the biofuels
field, but could prove extremely useful for the identificationof species (particularly in mixed field samples) necessary
for the future of algal ecology. It could also reduce
the number of redundant screens of algal species.

Role of Culture Collections as National
Algae Data Resource Centers
Culture collections are necessary to preserve the diversityof natural habitats, protect genetic material, and provide
basic research resources. At present, only a few major
algal collection centers exist in the United States andother countries. They currently maintain thousandsof different algal strains and support the research andindustrial community with their expertise in algae
biology. The function of a culture collection oftentranscends simple depository functions. They may also
support research on determining strain characteristics,
cryopreservation, and phylogeny either by themselves
or in connection with outside collaborators.
Currently, no central database exists that provides global
information on the characteristics of currently available
algal strains. Protection of intellectual property in private

industry has further exacerbated the flow of relevant strain
data. Some minimal growth information is available fromexisting culture collections, but it is very difficult to obtain
more detailed information on growth, metabolites, androbustness of particular existing strains. The establishmentof a central strain, open access repository could accelerate
R&D of algae-based biofuels production systems.
A number of algal strains are currently available from
culture collections such as UTEX (The Culture Collectionof Algae at the University of Texas at Austin, Texas), with
about 3,000 strains, and CCMP (The Provasoli-Guillard
National Center for Culture of Marine Phytoplankton at the
Bigelow Laboratory for Ocean Sciences in West Boothbay
Harbor, Maine), with more than 2,500 strains. However,
because many of the strains in these collections have beencultivated for several decades, some may have lost original
properties, such as mating capability or versatility regarding
nutrient requirements. To obtain versatile and robust strainsthat can be used for mass culture in biofuels applications,
it would be prudent to consider the isolation of new, native
strains directly from unique environments. For both direct
breeding and metabolic engineering approaches to improve
biofuels production, it will be important to isolate a wide
variety of algae for assembly into a culture collection thatwill serve as a bioresource for further biofuels research.
As the major culture collections already collect anddocument data on strains, they could potentiallyserve as nuclei for the development of national algae
resource centers. Culture collection organizations
could be responsible for the gathering anddissemination of detailed information about potentiallyvaluable strains. Information could include:
1. Strain name (species, subspecies name, taxonomy,reference)
2. Strain administration (number in collection,
preservation)
3. Environment and strain history (specific habitat,collector)
4. Strain properties: Cytological, biochemical, molecular,& screening results
5. Mutants
6. Plasmids and Phages
7. Growth conditions (media, temperature, pH) &germination conditions
8. Biological interaction (symbiosis, pathogenicity,
toxicity)
9. Practical applications (general and industrial)
10. Omics data (Genomics, Transcriptomics, Proteomics,
or Metabolomics)
2. Algal Biology

9Selecting Algal Model Systems
for Study
Given the diversity of algae, a large number of model
systems could be studied. However, in a practical sense,
the number of algal systems that can be studied in depth
has to be limited because a critical mass of researchers
is required to make progress on a given species.
In relation to biofuels, there are two types of algal model
systems to consider studying: species or strains amenable
to providing information on basic cellular processes
regarding the synthesis of fuel precursors, and species
or strains with characteristics useful for large-scale
growth. Species with sequenced genomes and transgenic
capabilities are the most amenable to investigating cellular
processes since the basic tools are in place. However, it
was shown in the Aquatic Species Program that not all
strains that grow well in the laboratory are suitable forlarge-scale culturing (Sheehan, 1998), so it is possiblethat other strains will be chosen for production. Adapting
the lessons learned from laboratory model strains tostrains known to be capable of large-scale growth may befeasible, but we cannot be certain that laboratory strains
and production strains will be sufficiently related to allow
for lessons from the former to be applied to the latter.

Useful Algal Characteristics
Culture stability over long periods will be a key to low costproduction of biofuels. Rapid growth is important bothfor overall productivity and the ability to compete withcontaminating strains. Other traits like the ability to grow tohigh cell density in continuous culture may allow a strain to
be maintained while at the same time reducing the amountof water to be processed daily. Resistance to predators andviruses could also be a useful phenotype. Also the ability
to flocculate without addition of chemical flocculating
agents could reduce the costs of harvest as long as it could
be controlled to avoid settling in the cultivation system.

Targeting Desired Fuel Product or Intermediate
One consideration in choosing model systems is thetype of fuel, intermediate, or co-product to be produced.
Possible fuel types of interest could include H2, lipids,
isoprenoids, carbohydrates, alcohols (either directly or
through biomass conversion), or methane (via anaerobic
digestion). Co-products could include pharmaceuticals(therapeutic proteins and secondary metabolites), foodsupplements, or materials for nanotechnology (in thecase of the silica cell wall of diatoms). A reasonable first
approach to identify model species that are optimal forthe production of a desired fuel is through a survey of theliterature, or a screen of environmental isolates for species
10

2. Algal Biologythat naturally make abundant amounts of the desired
product. In such a strain, cellular metabolism is alreadygeared toward production, which simplifies characterizationand possible strain development for production.

Secretion of Products or Intermediates
The ability of an algal species to secrete fuel precursors
may be attractive because it could reduce or skip the cell
harvesting step. However, there may be practical problems
to consider, such as, if the desired product is volatile,then collection of the atmosphere above the culture will
be necessary to isolate it, which will necessitate the useof closed bioreactors. Also to be considered is whether
secretion actually makes the product more readily
available. For example, although there are algae known
to secrete long-chain hydrocarbons (e.g., Botryococcus
braunii), they are still associated with the cells in a lipid
biofilm matrix, and thus are not free to form an organichydrocarbon phase in solution (Banerjee et al., 2002). Evenif sustainable secretion could be achieved, it is not clear
what the effect of a lipid emulsion in an algal culture would
be. For example, an abundance of exported lipids could
unfavorably alter fluidics properties or provide a carbon
source favoring growth of contaminants. Finally, secretionof either intermediates or products into the growth medium
could make these compounds vulnerable to contaminating
microbes for catabolism. Pilot-scale experimentationand further metabolic engineering is required to evaluate
possible advantages and disadvantages of secretion.

Capability for Heterotrophic or
Mixotrophic Growth
Heterotrophic or mixotrophic growth capabilities may
be attractive attributes of algal strains. In some species,
addition of supplemental carbon results in increased lipid
accumulation (Xu et al. 2006), even under mixotrophic
conditions where the substrate is not known to betransported into the cell (Ceron Garcia et al., 2006). If
the carbon source is utilized by the cell, growth in bothlight and dark periods is possible, and high cell densities
can be achieved. A potential disadvantage of the additionof external carbon sources is the possibility of increased
contamination by undesired microbes living off the carbon
source. However, this is not generally a problem with wellestablished fully-heterotrophic fermentation technologies
that are currently deployed worldwide at massive scale tomanufacture everything from cancer drugs to high- volume/
low- cost commodities such as lysine and ethanol.

2.2 Algal Physiology
and Biochemistry
Many algae are photosynthetic organisms capable ofharvesting solar energy and converting CO2 and water toO2 and organic macromolecules such as carbohydrates
and lipids. Under stress conditions such as high light or
nutrient starvation, some microalgae accumulate lipids
such as triacylglycerols (TAG) as their main carbon storage
compounds. Certain microalgal species also naturally
accumulate large amounts of TAG (30-60% of dry weight),
and exhibit photosynthetic efficiency and lipid production
at least an order of magnitude greater than terrestrial crop
plants (Hu et al., 2008). Cyanobacteria and macroalgae, asa general rule, accumulate mostly carbohydrates, with lipid
accumulation in macroalgae typically being less than 5% of
total dry weight (Mcdermid and Stuercke, 2003), althoughconcentrations approaching 20% lipid have been reported
in some species (Chu et al., 2003; Mcdermid and Stuercke,
2003). Lipids and carbohydrates, along with biologically
produced hydrogen and alcohols, are all potential biofuels
or biofuel precursors. It is, therefore, important tounderstand the metabolic pathways and processes thatgenerate them in order to advance biofuels production.

Photosynthesis and Light Utilization
When algae are cultivated photosynthetically, theefficiency of photosynthesis is a crucial determinate
in their productivity, affecting growth rate, biomass
production, and potentially, the percent of biomass
that is the desired fuel precursor. Though theoreticalbiomass productivity values in the range of 100-200 g/
m2/day have been presented (Chisti, 2007), there is no
current consensus on the true maximum productivity ofalgae. Theoretical productivity is an important concept,
however, because it can be used to set achievable goals forboth cultivation process design and strain improvement
projects. It may be useful to carry out photosynthetic
efficiency studies in algae similar to those that havebeen carried out for plants (Zhu et al., 2007 and 2008)
There are many good reviews available that cover basic
algal photosynthetic processes (Nelson et al., 1994;
Eberhard et al., 2008; Nelson and Yocum, 2006; Krause andWeis, 1991). Regardless of the cultivation practices used
to maximize light exposure (see Chapter 3), there remains
limitations of algal photosystems regarding light utilization.
The majority of light that falls on a photosynthetic algal
culture at greater than laboratory scale is not utilized. Inhigh cell density cultures, cells nearer to the light source
tend to absorb all the incoming light, preventing it fromreaching more distant cells (Christi, 2007). Even when
exposed to high light, algal photosystems have built-in

strategies to prevent the over-absorption of light energy,
which can lead to oxidative damage. A large majority ofabsorbed incident light is dissipated as heat and could beconsidered “wasted.” Even with this photoprotection, undercertain light regimes, photoinhibition or the reductionof photosynthesis due to light damage can still occur(Long et al., 1994; Foyer et al., 1994; and Niyogi, 1999).
In an effort to overcome this barrier, it was shown that
reducing the size of the chlorophyll antenna can increase
the efficiency of light utilization (Polle et al., 2002).
There is still much to learn about the dynamics andregulation of the photosynthetic apparatus (Eberhard et al.,2008). More emphasis should be placed on understanding
these processes if we are to better engineer the capture
and utilization of light energy for biomass production.

Carbon Partitioning and Metabolism
Knowing how and when carbon is partitioned in a cell into
lipids and/or carbohydrates could be very useful for biofuelsstrain development and designing cultivation strategies.
Understanding carbon partitioning will require extensive
knowledge of metabolic pathways. Metabolic networks
have been reconstructed in various microbes from genomic
and transcriptomic data, pathway analysis, and predictivemodeling (Vemuri and Aristidou, 2005). Research has also
been done in plant systems to understand carbon flux inbiosynthetic and degradative pathways (Lytovchenko et al.,2007; Schwender et al., 2004; Allen et al., 2009; Sweetlove
and Fernie, 2005; Libourel and Shachar-Hill, 2008).
However, carbon partitioning in algae is less understoodand research on how algal cells control the flux andpartitioning of photosynthetically fixed carbon into various
groups of major macromolecules (i.e., carbohydrates,
proteins, and lipids) is critically needed (Boyle and Morgan,
2009; Yang et al., 2002). A fundamental understanding of‘global’ regulatory networks that control the partitioningof carbon between alternative storage products will
be important for metabolic engineering of algae.
Further, a link between starch and lipid metabolism has
been established. Starch is a common carbon and energy
storage compound in plants and algae, and shares thesame precursors with the storage lipid TAG (Exhibit2.1). It is, therefore, possible that TAG and starch could
be inter-convertible, a potentially important implication
for biofuel production. In young Arabidopsis seeds
and Brassica embryos, starch transiently accumulated
and starch metabolism was most active before the lipid
accumulation phase (Kang and Rawsthorne, 1994; Ruuska
et al., 2002), indicating that starch is an important storage
compound and its synthesis precedes oil accumulation.
More recently, studies in higher plants showed that when
2. Algal Biology

11starch synthesis was impaired or inhibited, plant embryos
or seeds accumulated 40% less oil (Periappuram et al.,
2000; Vigeolas et al., 2004). While these results provide
an indication that starch synthesis is linked to lipid
synthesis, the nature of the interaction is unknown.
In microalgae, such an interaction has been also
indicated by studies on the diatom Cyclotella cryptica(Roessler, 1988). It could, therefore, be fruitful tofurther research de novo starch synthesis, degradation,and interaction with lipid metabolism in algae.

Algal Carbohydrates
Algae are incredibly diverse in the kind of simple
and complex carbohydrates that they use forcarbon storage and cell structure. If carbohydrates
are to be used as fuel precursors, for example forfermentation to produce alcohols, it is important todetermine the predominate types that are present.
Many green microalgae are plant-like, featuring rigid
cellulose-based cell walls and accumulating starch as
their main carbohydrate storage compound. Several
algae commonly use starch for energy storage, including
some red algae and dinoflagellates. Other algae, forexample many brown algae and diatoms, accumulate
carbohydrates such as laminaran, mannitol, or fucoidin as
food reserves. Cyanobacteria often store large quantities
of glycogen (Chao and Bowen, 1971; Yoo et al., 2002).
These major storage polysaccharides represent potential
biochemical feedstocks for conversion to liquid fuels.
Microorganisms capable of fermenting laminarin andmannitol from Laminaria hyperborea to ethanol havebeen identified and partially characterized (Horn et al.,2000a and 2000b). Other abundant polysaccharides,
for example alginate found in many brown algae, areconsidered less suitable for ethanol fermentation because
the redox balance favors formation of pyruvate as theend product (Bird and Benson, 1987). However, thesepolysaccharides may still prove useful as intermediates
to other types of conversion processes and final fuels.
Another important consideration in algal strains is thecomposition and structure of the polysaccharide cellwall. These structures can be an important source ofcarbohydrates, but like those from plants, must typicallybe broken down into simpler sugars before conversion
into biofuels. Cell walls can also be a technical barrier,for example, when trying to access DNA for genetic
manipulations, or efficiently extracting biofuel precursors
from cells in mass culture. As mentioned above, many
algal cell walls from different groupings are cellulosebased, though their physical structure and the presence
12

2. Algal Biology

or absence of other structural polysaccharides varies
greatly. There are also many algae that completely lackcellulose and have other polymers that provide structure
to the cell (Raven et al., 1992), while some algae lackcell walls entirely. Diatoms are also unique among algae
for the presence of silica in their cell walls. Some redalgae also have a thick extracellular matrix composedof important products such as agar or carrageenan.
Most cyanobacteria have a peptidoglycan layer and cellenvelope similar to those of gram-negative bacteria, andare encased in a polysaccharide sheath (Hoiczyk and
Hansel, 2000). An important lesson is the recognition of thediversity of algal polysaccharides and cell walls, and thetechnical challenges these structures may present in strain
manipulation, feedstock potential, and extraction processes.

Lipid Synthesis and Regulation
Primary Pathway for TAG Synthesis
Some algae, naturally or under stress conditions,accumulate significant quantities of neutral storage lipids
such as triacyglycerols (TAG), which are important
potential fuel precursors. The major pathway for theformation of TAG in plants first involves
de novo fatty acid synthesis in the stroma of plastids.
The synthesis of cellular and organelle membranes, aswell as of neutral storage lipids such as TAG, use 16 or
18 carbon fatty acids as precursors. TAG is formed byincorporation of the fatty acid into a glycerol backbone
via three sequential acyl transfers (from acyl CoA)in the endoplasmic reticulum (ER) (Exhibit 2.1).
TAG biosynthesis in algae has been proposed to occur
via the above Kennedy pathway described in plants.
Fatty acids produced in the chloroplast are sequentiallytransferred from CoA to positions 1 and 2 of glycerol3-phosphate, resulting in the formation of the central
metabolite phosphatidic acid (PA) (Ohlrogge and Browse,
1995). Dephosphorylation of PA catalyzed by a specificphosphatase releases diacylglycerol (DAG). Since
diglycerides are usually present in high amounts in rapidly
growing cultures, it may be of interest to research these
TAG intermediates. In the final step of TAG synthesis,a third fatty acid is transferred to the vacant position 3
of DAG by diacylglycerol acyltransferase, an enzymethat is unique to TAG biosynthesis (Lung and Weselake,
2006; Athenstaedt and Daum, 2006). The acyltransferases
involved in TAG synthesis may exhibit preferences
for specific acyl CoA molecules, and thus may play animportant role in determining the final acyl compositionof TAG (Hu et al., 2008). Alternative pathways to convert
membrane lipids and/or carbohydrates to TAG haverecently been demonstrated in bacteria, plants and yeast
in an acyl CoA-independent way (Arabolaza et al., 2008;

Glc6P

CO 2
StarchStarchAGPPase
AmylasesCentral
3-PGA

Glc6P

Metabolic

3-PGA

Mitochondria

Pyruvate
PDH

CO 2

Acetyl -CoA

Chloroplast

ACCasePyruvate

Oxaloacetate

Acetyl-CoA

TCA cycle

KAS I
KAS II

Glycolipids

SAD

Galactolipase?

C16 - C18 CoA

Phosphatidic acid
GDAT?

ER

Diacylglycerol (DAG)
Acetyl-

DAGT

Phospholipids
PDAT?

Figure 2.1 Major pathways for fatty acidand TAG synthesis in plants and algae
3-PGA: 3-phosphoglycerate; Accase: acetyl
CoA carboxylase; ACP: acyl carrier protein;
AGPPase: ADP glucose pyrophosphorylase;
ER: Endoplasmic reticulum; GDAT: putative
glycolipids: DAG acyltransferase; Glc6P:
glucose-6-phosphate; KAS: 3-ketoacyl-ACP;
PDAT: Phospholipids: DAG acyltransferase;
PDH: pyruvate dehydrogenase (putative
pathways were proposed in dashed lines).

Triacylglycerol

Lipid Body

Dahlqvist et al., 2000; Stahl et al., 2004). Such pathways
have not yet been studied in algae. Moreover, PA andDAG can also be used directly as substrates for synthesisof polar lipids, such as phosphatidylcholine (PC) andgalactolipids. These pathways are worth investigatingwhen developing strains for improved lipid production.
The regulation of the synthesis of fatty acids and
TAG in algae is relatively poorly understood. This
lack of understanding may contribute to why the lipid
yields obtained from algal mass culture efforts fallshort of the high values (50 to 60%) observed in thelaboratory (Hu et al., 2008; Sheehan et al., 1998).
Understanding lipid regulation can help to maximize
scenarios for lipid production and strain improvement.
Because fatty acids are common precursors for thesynthesis of both membrane lipids and TAG, how thealgal cell coordinates the distribution of the precursors to
distinct destinations or how the inter-conversion between
the two types of lipids occurs needs to be elucidated. If theability to control the fate of fatty acids varies among algal
taxonomic groups or even between isolates or strains, thebasal lipid and TAG content may represent an intrinsic

property of individual species or strains. If this proves tobe true, it could be a challenge to extrapolate information
learned about lipid biosynthesis and regulation in laboratory
strains to production strains. Similarly, it will be difficult
to use information regarding lipid biosynthesis in plants
to develop hypotheses for strain improvement in algae.
As an example, the annotation of genes involved in lipid
metabolism in the green alga Chlamydomonas reinhardtii
has revealed that algal lipid metabolism may be different
from that in plants, as indicated by the presence and/or
absence of certain pathways and by the size of the genefamilies that relate to various activities (Riekhof et al.,2005). Thus, de novo fatty acid and lipid synthesis should
be studied in order to identify key genes, enzymes and newpathways, if any, involved in lipid metabolism in algae.

Alternative Pathways to Storage Lipids
Algae may possess multiple pathways for TAG synthesis,
and the relative contribution of these individual pathways
to overall TAG formation may depend on environmental
or culture conditions. Analyzing different algae could help
to elucidate the possible pathways of TAG synthesis: thede-novo Kennedy Pathway, the potential pathway for lipid
formation from starch reserves mentioned earlier, and other
2. Algal Biology

13potential pathways to convert membrane phospholipids andglycolipids into TAG. The thylakoids of chloroplasts are
the main intracellular membranes of eukaryotic algae, andtheir lipid composition dominates extracts obtained from
cells under favorable growth conditions. Algal chloroplasts
contain monogalactosyldiacylglycerol as their main lipid(~50%), with smaller amounts of digalactosyldiacylglycerol( ~20%), sulfoquinovosyldiacylglycerol (~15%) andphosphatidlyglycerol ( ~15%) (Harwood, 1998). Understress conditions as degradation of chloroplasts occurs,
the fate of these abundant lipids remains unclear. It has
been proposed that these alternative pathways that convert
starch, excess membrane lipids, and other components into
TAG play an important role for cell survival under stress.

Organelle Interactions
Chloroplast membranes control the exchange of metabolites
between the plastid and the cytoplasm. As mentioned
earlier, the chloroplast stroma is the primary location
for fatty acid biosynthesis in plants. Fatty acids can thenbe either assembled into glycerolipids at chloroplast
membranes or they can be exported to the ER andassembled into lipids for cellular membranes. Some
glycerolipids assembled at the ER are then returned tothe plastid where they are assimilated. Lipid trafficking
is, therefore, an important aspect of membrane formationand lipid fate (Benning, 2008). Current work in plants
is focused on deciphering lipid transport across plastid
envelopes. Such work is also important in algae tobetter understand the interaction among organelles as
it relates to lipid formation and lipid trafficking.

Oxidative Stress and Storage Lipids
Under environmental stress conditions (such as nutrient
starvation), some algal cells stop division and accumulate
TAG as the main carbon storage compound. Synthesis of
TAG and deposition of TAG into cytosolic lipid bodies
may be, with exceptions, the default pathway in somealgae under stress conditions (Hu et al., 2008). In addition
to the obvious physiological role of TAG as a carbon andenergy storage compound, the TAG synthesis pathway
may also play a more active and diverse role in the stressresponse. The de novo TAG synthesis pathway can serveas an electron sink under photo-oxidative stress (discussed
earlier). Under high light stress, excess electrons that
accumulate in the photosynthetic electron transport chain
induce over-production of reactive oxygen species, which
may in turn cause inhibition of photosynthesis and damage
to membrane lipids, proteins, and other macromolecules.
However, the formation of fatty acids could help consume
excess electrons, and thus relax the over-reduced electrontransport chain under high light or other stress conditions.

14

2. Algal Biology

The TAG synthesis pathway is also often coordinatedwith secondary carotenoid synthesis in algae (Rabbani
et al., 1998; Zhekisheva et al., 2002). The molecules(e.g., β-carotene, lutein, or astaxanthin) produced in
the carotenoid pathway are sequestered into cytosolic
lipid bodies. Carotenoid-rich lipid bodies serve as a‘sunscreen’ to prevent or reduce excess light from striking
the chloroplast under stress. TAG synthesis may alsoutilize phosphatidylcholine, phatidylethanolamine or
toxic fatty acids excluded from the membrane system
as acyl donors, thereby serving as a mechanism to“detoxify” these compounds and deposit them in theform of TAG. Because of the potential importance ofstress conditions on lipid production in algae, the exact
relationship between oxidative stress, cell division,and storage lipid formation warrants further study.

Lipid Body Formation and Relationshipto Other Organelles
Despite the economic importance of algae as a source ofa wide range of lipophilic products, including vitamins,
hydrocarbons and very long-chain ω-3 and ω -6 fatty
acids, there have been relatively few studies on lipid
bodies in algae compared with plants and fungi. The studyof lipid-body biogenesis in plants has focused largely on
the role of oleosins (Murphy, 1993; Huang, 1992). Thisis understandable in view of their exclusive localization
on lipid-body surfaces, their apparently widespread
distribution and their great abundance in many lipidstoring seeds. Nevertheless, there are now doubts about
the role of oleosins in the biogenesis of plant lipid bodies.
It has been suggested that oleosins may be primarily
associated with the stabilization of storage lipid bodies
during the severe hydrodynamic stresses of dehydration
and rehydration that occurs in many seeds (Murphy, 2001).
Lipid bodies may dock with different regions of the ER
and plasma membrane, or with other organelles such as
mitochondria and glyoxysomes/peroxisomes, in orderto load or discharge their lipid cargo (Zehmer et al.,2009). In oil-producing microorganisms, as rapid lipid
body accumulation occurs, a close relationship is often
found between neutral lipids like TAG and the membrane
phospho- and glyco- lipids (Alvarez and Steinbuchel,2002). This relationship may be both metabolic, with acyl
and glycerol moieties exchanged between the different
lipid classes, and spatial, with growing evidence of
direct physical continuities between lipid bodies andbilayer membranes. In order to better understand lipid
metabolism in algae, the structure and function of lipid
bodies, and their interactions with other organelles
related to storage lipid formation requires further study.

Besides biochemical analysis to study algal lipids
and carbohydrates, studies involving Expressed
Sequence Tag (EST) analysis, cDNA microarray
analysis, and proteomic studies, for example, would
also help provide information about photosynthetic
carbon partitioning and lipid/carbohydrate synthesis
in algae. Based on such information, metabolicengineering through genetic manipulation represents
yet another strategy for the production of algal oils.

2007). There are two major types of hydrogenases, thosecontaining iron (which are generally H2-evolving), or
both nickel and iron (which are generally H2-uptake
enzymes). One of the most important characteristics
of hydrogenases is that they are O2 sensitive.
Four biological challenges limiting biohydrogen production
in algae have been identified: (a) the O2 sensitivity ofhydrogenases, (b) competition for photosynthetic reductant
at the level of ferredoxin, (c) regulatory issues associatedwith the over production of ATP, and (d) inefficiencies in
the utilization of solar light energy (Seibert et al., 2008).
These challenges could be addressed by (a) engineeringhydrogenases with improved tolerance to O2 (Cohenet al., 2005), (b) identifying metabolic pathways thatcompete with hydrogenases for photosynthetic reductant,and engineering their down-regulation during H2production (Mathews and Wang, 2009), (c) engineering
the photosynthetic membrane for decreased efficiency ofphotosynthetic-electron-transport-coupled ATP production(ATP is not required for H2 production), and (d) engineering
the photosynthetic antenna pigment content for increased
efficiency of solar light utilization (Polle et al., 2003).

Biohydrogen
Some microalgae and cyanobacteria can produce H2, apotential fuel product, in the following reactions: 2H2O
+ light energy → O2 + 4H+ + 4e- → O2 + 2H2. Three
pathways have been described in green algae: two lightdriven H2-photoproduction pathways, and a third, lightindependent, fermentative H2 pathway coupled to starchdegradation (see Exhibit 2.2) (Melis et al., 2000; Gfeller
and Gibbs, 1984). As a substrate, the light-driven pathways
can either employ water (through photosystems II andI) or NADH from the glycolytic breakdown of stored
carbohydrate (through photosystem I). In all pathways,
ferredoxin (FD) is the primary electron donor to thehydrogenase enzyme. Hydrogenases are the enzymes
responsible for releasing molecular H2 (Ghirardi et al.,Glycolysis
ADP

ATP

starchpyruvate
NADH

NAD++H+

Pheo

Photosystem II

Energy (Volts)

P680*

-0.4
0.0
0.4
0.8
1.2

Chl
P680

QA

QB

PQ
Cyt b

2H2O
O2+2H+

Photosynthesis

Cyt f

P700*

Photosystem I

NAD++H+

-1.2
-0.8

PFOR

FD(ox)

NPQR

PC

Chl
P700

A0

A1

Acetyl-CoA + CO2

Fx

FA/FB

FD
CO2
fixationFD (red)

H2ase

H2

2H+

Figure 2.2 Three different pathways for H2 production
Two are driven by light and the third occurs in the dark. Either
water or starch can be the electron donor. Carbon is fixed undernormal photosynthesis with water as the donor, but the electron
acceptor is switched at the level of ferredoxin (FD) from CO2 toprotons under conditions that lead to H2 production. (Drawing
courtesy of Prof. M. Posewitz, Colorado School of Mines )2. Algal Biology

15

Recently there has been a focus on using cyanobacteria to
produce H2 (Tamagnini et al., 2002; Prince and Kheshgi,
2005). While many of the challenges described above
exist in these organisms, they are typically more easily
engineered than eukaryotic algae and have more O2tolerant hydrogenases (Ghirardi et al., 2009). A possibility
to improve the efficiency of biological H2 production
includes developing biohybrid (those with biologicaland synthetic components) and synthetic photosynthetic
systems that mimic the fuel-producing processes ofphotosynthetic organisms. In all cases, more knowledgeof photosynthesis, hydrogen evolution pathways, andhydrogenase structure and function is required.
To circumvent the inhibition of hydrogenase by O2,
another option for H2 production is to take advantageof the fermentation pathways that exist in some algae
for H2 production at night, using the carbon reserves
produced during the day. In cyanobacteria, fermentation isconstitutive, accounting for their ability to adapt quickly
to changing environmental conditions (Stal and Krumbein,1987). All cyanobacteria examined thus far employ the
Embden-Meyerhof-Parnas (EMP) pathway for degradationof glucose to pyruvate. From here, several cyanobacteria
were found to use pyruvate-ferredoxin oxidoreductase,which reduces ferredoxin for subsequent H2 production
via nitrogenase or hydrogenase (Stal and Moezelaar,1997). This temporal separation of H2 production fromphotosynthesis has been demonstrated in the unicellularcyanobacteria Cyanothece sp. ATCC 51142 (Toepel etal., 2008) and Oscillatoria (Stal and Krumbein, 1987),
using nitrogenase as the catalyst. Using hydrogenase as
the catalyst, the unicellular non-N2-fixing cyanobacterium
Gloeocapsa alpicola can evolve H2 from the fermentationof stored glycogen (Serebryakova et al., 1998). Similarly
under non-N2 fixing condition, the hydrogenase from
Cyanothece PCC 7822 produces H2 in the dark andalso excretes typical fermentation byproducts including
acetate, formate, and CO2 (van der Oost et al., 1989).
It is well established that dark fermentation suffers fromlow H2 molar yield (less than 4 moles of H2 per mol
hexose) (Turner et al. 2008). This is due to the productionof organic waste by-products described above alongwith ethanol. In order to fully realize the potential of H2
production via indirect biophotolysis, several challenges
must be addressed: (a) improve photosynthetic efficiency
to increase the yield of carbohydrate accumulation;(b) remove or down-regulate competing fermentative
pathways thus directing more of the cellular flux toward H2
production; and (c) learn to express multiple hydrogenases
so that electrons from both ferredoxin (Fd) and NAD(P)H can serve as electron donors to support H2 production.

16

2. Algal Biology

2.3 Algal Biotechnology
The biotechnology industry grew from more than 100
years of basic biology and genetics R&D. Collectively,
biological process engineering breakthroughs directly
enabled new multi-billion dollar commercial enterprises
for agriculture, human health, and the production ofchemicals. Thus, the importance of being able to harness
biotechnology approaches to generate algae with desirable
properties for the production of biofuels and bioproducts
cannot be overlooked. However, methods to manipulate
algae genetically remain far behind those developed
for commonly used bacteria, fungi and higher plants.
Efforts should be undertaken to understand the fundamental
genetic and cellular processes involved in the synthesis
and regulation of potential fuel precursors from diverse
species of algae. While a better understanding of the basic
biology of algal growth and metabolite accumulation
using modern analytical approaches will provide a wealthof hypotheses for strain improvements, the limited algal
genetic toolbox that can be used to modify processrelevant strains remains a significant technical hurdle.
Thus, this subsection seeks to 1) address the genetic
tools available to modify algal strains, 2) describes
enabling technologies and analyses that can be applied
for biofuels and bioproducts, and 3) highlights a few
examples of how algal biotechnology has been applied
to date. Methods to cultivate and process algae incommercial settings are no less important to biotechnology,
and these are the subjects of Chapters 3 and 4.

The Genetic Toolbox
Because biological productivity is a key driver for
economic viability, the ability to improve on native strains
is a potentially important element in the research effort
toward algal biofuels. Genetic approaches are commonlyused to introduce genes, to delete or disrupt genes, and to
modify genes or gene expression in a particular organism.
Some of these methods can also be used to study the
localization of gene products (mRNAs and proteins)
within cells. For algae that undergo sexual reproduction,
the toolbox allows traits to be recombined into a single
individual by mating parental strains. For all of theseapproaches, the stability of the desirable trait through many
generations and the possibility of unintended horizontal
gene transfer to other organisms are important researchquestions to consider in the context of mass production.

Mutagenesis
The generation and characterization of mutants is a
powerful approach to understand gene function andpotentially generate strains with desirable characteristics.

As long as an appropriate screening process isdeveloped, spontaneous mutants arising from errors
in DNA replication can be identified. However, thisapproach is limited by the low frequency of naturally
occurring mutations, which necessitates a large amountof screening. Mutants are more readily generated bystandard chemical or UV-based mutagenesis approaches.
Drawbacks of this approach include the introductionof multiple mutations in a genome and the difficultyin mapping the locus responsible for the phenotype.
Targeted or tagged mutagenesis offers the advantage ofsimplified identification of the mutated gene. Targeted
approaches rely on homologous recombination (if thenative gene is to be entirely replaced), or introduction ofa modified copy of the gene that inserts elsewhere into
the genome. Certain strategies can also enable changes
in gene expression. Tagging can be accomplishedby introducing a selectable marker randomly into
the genome (Adams et al., 2005), or through theuse of transposons (Miller and Kirk, 1999).
Any mutagenesis approach requires an appropriate
screening technique to enrich for and isolate mutants. Thiscan include either a requirement for mutants to grow undercertain conditions (e.g., in the presence of an antibiotic), or
to exhibit a characteristic phenotypic change that is easily
assayed. For the latter, changes in fluorescence properties,e.g., reduced chlorophyll fluorescence (Polle et al., 2002),
or increased neutral lipid accumulation via Nile Red
staining (Cooksey et al., 1987) can be screening criteria.
Given a well-developed screening approach, iterative
selection could be used to generate useful algal strains
without the need to generate genetically engineered(GE) algae—something that could be desirable forlarge-scale algal production.

Selectable Markers
A powerful way to manipulate genomes is the ability tointroduce DNA into the cell, and to select for cells in which
the DNA is present. Typically, this is accomplished byintroducing an antibiotic resistance gene as a selectable
marker (Hasnain et al., 1985; Dunahay et al., 1995),
along with the DNA of interest on an extra-chromosomal
element called a plasmid. Marker systems that takeadvantage of the ability to genetically complement
auxotrophic and metabolism mutants have also beenachieved (Kindle et al., 1989; Debuchy et al., 1989). An
important consideration is that the use of antibiotics inlarge-scale production has two major drawbacks. The
first concern is the cost of the antibiotic. The second
concern is the environmental implications of widespread

antibiotic use, which could exacerbate current problems
with increased antibiotic-resistant microbes. Antibiotic
resistance is a powerful tool for research; however, othermethods may need to be considered for production scale.
For research purposes, the decision as to which antibiotic
selection marker to use includes whether the antibiotic
compound is sensitive to light and whether its potency ismodulated by the salinity of the growth medium. Several
antibiotic markers have been developed for microalgae,
including resistance to neomycin, kanamycin (Hasnain
et al., 1985; Dunahay et al., 1995), zeocin (Apt et al.,
1996; Hallmann and Rappel, 1999), and nourseothricin(Poulsen et al., 2006). The mechanism of antibiotic
resistance can also be an important factor. For example,
zeocin resistance requires stoichiometric binding of theantibiotic by the resistance protein, whereas nourseothricin
is inactivated enzymatically. A direct comparison of thetwo has shown that the nourseothricin system generates
larger numbers of transformants (Poulsen et al., 2006),
presumably because requirements for expression levelsof the gene are lower and less taxing to the cells.
Sophisticated metabolic engineering could require theintroduction of multiple selectable or complementary
markers. Most of the current selectable markers are derived
from bacterial genes, but markers based on resistancegenerated by conserved ribosomal protein mutations havealso been successful (Del Pozo et al., 1993; Nelson etal., 1994). Caveats are that the mutated gene may need
to be expressed at a higher level than the native gene
(Nelson et al., 1994), or that the native gene may need tobe replaced in order to generate the phenotypic effect. For
complementation approaches, appropriate mutations mustbe generated in the species of interest, ideally in wellcharacterized genes that can be easily complemented.
Once an appropriate antibiotic resistance orcomplementing gene is identified, constructs must be
made to place the gene under control of an expression
element that functions in the species of interest. Thistypically involves using control elements from ahighly expressed gene in that species. However, there
are examples of control elements that work acrossevolutionarily diverse species (Dunahay et al., 1995).

Transformation Methods
Gene transfer systems have been established in many
algal strains, including cyanobacteria (Synechococcus,
Synechocystis, Anabaena, Nostoc, Arthrospira),
green algae (Chlamydomonas, Dunaliella, Chlorella,
Volvox), diatoms (Cyclotella, Navicula, Phaeodactylum,
Thalassiosira), dinoflagellates (Amphidinium,
2. Algal Biology

17Symbiodinium), red algae (Cyanidioschyzon,
Porphyridium, Gracilaria, Porphyra), brown algae(Laminaria, Undaria) and euglenoids (Euglena).
Hallmann (2007) provides a comprehensive review ofalgal transgenics and implications for biotechnology.
A common method for introducing DNA into algal cells
is the biolistic (“gene gun”) approach (Armaleo et al.
1990), which is useful for both nuclear and chloroplasttransformation (Boynton et al., 1988; Dunahay, 1993).
Other successful methods include electroporation(Shimogawara et al., 1998), vortexing with glass beads(Kindle et al., 1991) or silicon carbide whiskers (Dunahay,1993). For most of these approaches, a fundamental
challenge to introducing DNA into a cell is the nature of
the cell wall. If methods exist to remove or perforate thecell wall, then chemically based methods of transformation
could be applied. Many transformation methods also exist
for cyanobacteria, including conjugation, electroporation,and biolistic approaches (Matsunaga and Takeyama, 1995).

Sexual Crossing

Gene Expression Control Elements
Gene expression control elements (also known astranscriptional regulators) can modulate the levels
of mRNA, which can then subsequently affect algae
traits. Frequently, transgenes are overexpressed byusing strong control elements, but considering theneed for balance in cellular metabolism, intermediate,slightly elevated, or reduced levels of expression may
be desirable. Control element strength can be evaluatedby monitoring mRNA levels by quantitative PCR or
high throughput transcriptomics (i.e., microarrays).
In addition, inducible and repressible promoters thatcan be actuated by simple manipulations are desirable,
allowing for precise control over the timing of gene
expression. The nitrate reductase promoter has provenuseful in this regard in microalgae, because it is inducedwith nitrate in the growth medium, and repressed withammonium (Poulsen and Kroger, 2005). Identification ofother inducible or repressible control elements would be
useful for both research and commercial applications.

Breeding of desired characteristics from a number ofphenotypic variants can allow for strain development
without creating GE algae. Algal strains often containmultiple copies of their genome, and so recessive genotypes
may not manifest unless that genotype is allowed to“breed true” though a series of sexual crosses. Manymacroalgae species are capable of sexual reproduction,and traditional mutagenesis and breeding has been used
to improve commercial varieties of seaweed since the1950s (Bird and Benson, 1987). With the exception ofChlamydomonas, classical genetic approaches using
sexual crossing are not well developed in microalgae,
but this methodology could prove to be extremely
important. Some diatoms can be propagated vegetatively
only for a limited number of generations and must be
crossed periodically to maintain culture viability.

RNA Interference (RNAi)

Homologous Recombination

RNAi approaches have been investigated primarily
in the model green alga, Chlamydomonas reinhardtii,
although there is a recent report of the method being
used in a red alga (Ohnuma et al., 2009). In a practicalsense, selecting for functional RNAi can be problematic(Fuhrmann et al., 2001). Even on vectors containing botha selectable marker and an RNAi construct, only a small
percentage of selected transformants will have functional
RNAi. One solution to this problem was developed in
C. reinhardtii. The selection process was based on ahigh-throughput phenotypic screen for functional RNAiby co-targeting an amino acid synthesis pathway alongwith the desired gene of interest (Rohr et al., 2004).

Homologous recombination-based gene integration
approaches are common in many strains of cyanobacteria,
but less so in microalgae. DNA introduced into the nucleus
of microalgal cells generally integrates randomly into
the genome (Dunahay et al., 1995). Gene replacement
via homologous recombination is more desirable thanrandom integration because it can overcome phenotypic
dominance issues when more than one copy of thegene is present, and can be used to knockout genes.
Successful recombination approaches have included the
addition of long flanking regions to the gene of interest(Deng and Capecchi, 1992), use of single stranded DNA(Zorin et al., 2005), or co-introduction of recombinase
genes with the transforming DNA (Reiss et al., 1996).
18

2. Algal Biology

RNAi can be a useful tool to down-regulate gene
expression, especially in the study of polyploid organisms
or when dealing with redundant genes where traditional
genetic manipulations are difficult. RNAi operates
through double-stranded RNAs that are cut down tosmall sizes and used to target suppression of specificgenes by base pairing. RNAi can inhibit transcription(Storz et al., 2005) and control translation by either
cleaving specific mRNAs or sequestering them awayfrom the ribosome (Valencia-Sanchez et al., 2006).
Two general types of RNAi vectors can be constructed– one containing an inverted repeat sequence from thegene to be silenced, and another in which bidirectionaltranscription generates the double stranded RNA.

Directed Evolution of Enzymes/Proteins
Regarding core cellular metabolic processes, asubstantial amount of regulation occurs at the protein
level, including allosteric activation and metabolic
feedback. Indeed, this level of regulation integrates
the proteome with the metabolome. Although time
consuming, approaches to modify proteins by genetic
engineering so that they function more efficiently or
have other favorable characteristics could be valuablefor the development of algal biofuels technology.

Protein Tagging Technologies
Tagging proteins with fluorescent markers is useful indetermining their intracellular location and can provide
at least semi-quantitative evaluation of their abundance
in a simple measurement. This information could be
useful in monitoring intracellular metabolic processes
associated with biofuel precursor production. Greenfluorescent protein and its derivatives are the mostwidely used and versatile protein tags, but others havedemonstrated utility and some possible advantages(Regoes and Hehl, 2005; Gaietta et al., 2002).

Enabling Technologies: “Omics”
Approaches and Bioinformatics
High throughput approaches, such as genomics,
transcriptomics, and proteomics, have enabled in-depth
analyses to be performed in a whole cell context. Together,
these methods have revolutionized the study of organisms
both in culture and in natural habitats. These biologicaladvancements have been complemented by developments incomputer sciences, creating the new field of bioinformatics
where powerful new databases and search algorithms are
helping biologists share and build upon experimental resultsin ways and timescales that were never before possible.
Algal species are being analyzed using these analytical
approaches to better understand the underlying
cellular processes and regulation involved indefining the attributes of the strain. Undoubtedly, thecharacterization of these cellular processes will prove
useful for applications, forming the foundation for
applied research and technology development.

Sequencing and Annotating Algal Genomes
Sequenced genomes are an essential basis of information
for the interpretation of transcriptomic and proteomic
data. With the development of more powerful sequencing
methods, in which costs have been substantially1reduced and more coverage is obtained in a shorter
period of time, obtaining a genome sequence should
be strongly considered for any strains being developedfor biofuels research or production. It must be noted
though, that the genomic data are only as useful as
the annotation (the assignment of gene functions orfamilies), so it will be important to provide sufficient
resources to allow for detailed analysis of the data.
Genome size in algae can vary substantially, even inclosely related species (Connolly et al., 2008). One
reason for this variation is likely to be the accumulationof repeated sequences in the larger genomes (Hawkins
et al., 2006). Even though new sequencing technologies
readily enable accumulation of data for large genomes,
assembly of such data (especially with short read lengths)
can be more challenging in repeat-laden genomes.
Eukaryotic algae constitute members from at least eight
major phyla, all featuring a complex series of primaryand secondary endosymbioses (Falkowski et al., 2004).
It is likely that the different symbioses have affected the
distribution of DNA between the plastid and nucleus(Wilhelm et al., 2006), which could impact the regulationand processes of fuel precursor production. A genomic
survey of representatives from all major algal classes isdesirable, with a special focus on classes or individual
species within classes that make abundant fuel precursors.
Except for cyanobacteria, for which over 20 completed
genome sequences are available, the nuclear genomesof only a handful of microalgal species have been fullyor partially sequenced to date.1 These species include
unicellular green algae (C. reinhardtii, Volvox carteri), a
red alga (Cyanidioschizon merolae), several picoeukaryotes(Osteococcus lucimarinus, Osteococcus tauris, Micromonas
pussilla, Bathycoccus sp.), a pelagophyte (Aureococcus
annophageferrens), a coccolithophore (Emiliania huxleyi),
and several diatoms (Phaeodactylum tricornutum,
Thalassiosira pseudonana, Fragilariopsis cylindrus).
Genome sequencing projects are also underway for themacroalga Porphyra purpurea at the Joint Genome Institute(U.S. Department of Energy) and for Ectocarpus siliculosus
at Genoscope - Centre National de Séquençage (France).
Bioinformatics analysis of sequenced genomes, especiallyat the basic level of gene annotation, will be essential
to make sequence data usable. If not properly done,
bioinformatics can represent the largest stumbling blockto achieving that goal. Quality standards and appropriate
training should be established at the onset of activities
to ensure consistent and useful annotation. This could

For a listing, visit http://genome.jgi-psf.org/euk_cur1.html
2. Algal Biology

19include the standardization of using a particular sequencing
approach that provides sufficient coverage of ESTs toensure accurate gene modeling. Comparative genomics
approaches between related organisms and organismsthat carry out similar functions can also help assign genefunction and identify metabolic pathways of interest.
Currently, at least10 other algal genomes, as well as
another dozen or so EST projects, are underway. It isnotable that while these projects represent a very usefulsurvey, the rationale for sequencing these organisms was
not related to lipid production or other biofuels efforts.
Therefore, there are still a large number of useful algal
species to sequence that are related to biofuels production,such as Dunaliella sp., Nannochloropsis sp., Scenedesmus
sp., Chlorococcum sp., and Pseudochlorococcum sp.

Transcriptomics
While genome sequencing will be an important componentof any algal biofuels technology development effort,
quantitative transcriptome profiling using new, highthroughput sequencing technologies will also become
increasingly important because it will not only help
with genome annotation (for example, identifying
coding regions of DNA), but it is also emerging as arobust approach for genome-wide expression analysis
in response to particular environmental conditions.
New, high-throughput sequencing technologies enable
comprehensive coverage of transcripts and quantification of
their relative abundance. Most transcriptomics approaches
evaluate mRNA levels, however, small RNAs also playmajor regulatory roles in algae (Bartel, 2004; Cerutti
and Casas-Mollano, 2006). Small RNAs have been
identified in microalgae (Zhao et al., 2007) and should beconsidered in investigations of gene expression regulation,
especially with regard to translational regulation.

Proteomics
The cellular complement of proteins reflects its metabolic
potential, and ultimately determines how a cell functions
in response to the environment. Mass-spectrometry
approaches allow for robust evaluation of soluble andmembrane-associated proteins in the form of protein
peptides. These approaches not only enable protein
identification, but also allow for protein quantification anddetection of post-translational modifications (Domon and
Aebersold, 2006; Tanner et al., 2007; Castellana et al.,2008). In the absence of genomic information, proteomic
approaches can also help assess the metabolic potential oforganisms that may be difficult to isolate, or can determinefunctional diversity of a community of organisms.
20

2. Algal Biology

Metabolomics and Lipidomics
The metabolome is the collection of small molecularweight compounds in a cell that are involved in growth,maintenance, and function. Because the chemical
nature of metabolites varies more than for mRNAand proteins, different metabolomic analysis tools
are applied, including liquid chromatography mass
spectrometry, gas chromatography mass spectrometry,and nuclear magnetic resonance (Dunn et al., 2005).
There is a distinction between metabolomics, which
involves the identification and analysis of metabolites,
and metabonomics, which is the quantitative
measurement of the dynamic multi-parametric metabolic
response of living systems to pathophysiologicalstimuli or genetic modification (Nicholson et al.,1999). Both metabolomics and metabonomics may
be important in terms of algal biofuels research.
Lipids are a subset of the molecular repertoire of thealgae cell. Lipid analysis is done using mass spectrometry
approaches (Han and Gross, 2005; Dettmer et al., 2007).
Quantitative comparison of lipid type and abundance are
critical components of lipid-based biofuels approaches aslipid characteristics can determine the suitability of the
final fuel produced. Monitoring lipid characteristics under avariety of different cultivation regimes can also help inform
process engineering and improve yields (Yu et al., 2009).

Applications of Biotechnology
to Algal Bioenergy
Cyanobacteria
Genetic manipulation of cyanobacteria is generally
more advanced than that of eukaryotic algae because
many of the tools developed for bacterial genetics areapplicable in cyanobacteria. For example, spontaneoustransformation, double-homologous recombination,and protein tagging are routine in some cyanobacterial
systems, and at least half a dozen selectable markers
are available for Synechocystis (Vermaas, 1998).
Cyanobacteria generally do not accumulate storage
lipids, but they are prolific carbohydrate and secondary
metabolite producers. Some strains can double
quickly (less than 10 hours), and some strains can fix
atmospheric nitrogen and produce hydrogen. Moreover,many can be genetically manipulated, making themattractive organisms for biofuels production.
Synechocystis has been used extensively for the study ofcarbon metabolism toward production of hydrocarbon
fuels and intermediates. The genome of this strain
was sequenced over a decade ago, the first among
photosynthetic organisms (Kaneko et al., 1996). Many

photosynthesis and carbon metabolism mutants have been
generated, and high-throughput analytical techniques
have been applied to the study of its transcriptome,
proteome, and metabolome (Singh et al., 2008; Fulda etal., 2006; Koksharova et al., 2006; Eisenhut et al., 2008).
Transgenic approaches have enabled the production andsecretion of cellulose, sucrose (Nobles and Brown, 2008),
ethanol (Deng and Coleman, 1999), and isobutanol (Atsumi
et al., 2009) in Synechococcus. Relatedly, Synechococcus
and Anabaena strains have been studied for their hydrogenproduction potential (Tamagnini et al., 2002). The latter is afilamentous strain that can form heterocysts, which are cellswith specialized structure and metabolism that function
anaerobically (important for the production of hydrogen).
Despite all of the progress, a comprehensive understandingof carbon metabolism and regulation is not yet available
in all cyanobacteria. In order to redirect carbon to a fuelproduction pathway, it will be necessary to further
characterize the dominant carbon storage compounds(sinks) in cyanobacteria, including glycogen,glucosylglycerol, sucrose, and polyhydroxybutyrate(PHB), and the conditions that trigger carbohydrate
accumulation. For example, it is known that glycogenaccumulates under normal growth conditions in
Synechocystis, whereas glucosylglycerol and sucrose
can accumulate under salt stress (Yoo et al., 2007;
Xiaoling Miao et al., 2003). It has also been shown that
PHB accumulates under nitrogen depleting conditions(Miyake et al., 2000). It has not been shown how thesepathways can be manipulated for the benefit of biofuels
production. These studies can not only serve to advancethe understanding of how the production of different
carbon storage molecules are controlled in response tophysiological conditions, but may also serve to guide thedevelopment of other types of algae for biofuels production.

Microalgae
Unicellular eukaryotic microalgae are the product ofover 3 billion years of evolution, and are highly diverse(Falkowski et al., 2004). Multiple endosymbiotic eventsoccurred during the evolution of microalgae. These
events likely had significant effects on the metabolic
pathways and regulation of fuel precursor synthesis.
For example, fatty acid synthesis, which occurs in thechloroplast, is at least partly regulated by nuclear-encoded
gene products, and there are fundamental differences in
the interaction between the nucleus and chloroplast inalgae with different extents of endosymbiosis (Wilhelm
et al., 2006). Continued exploration of the evolutionary
2

diversity of algae is important to identify species thatare adept at making fuel precursors and with highproductivity under various environmental conditions.
Chlamydomonas reinhardtii is the most studied eukaryotic
algae. In addition to having a sequenced nuclear genome(Merchant et al., 2007) and well developed transgenic
capabilities, it can be sexually crossed. It is not an abundant
lipid producer, but nevertheless, C. reinhardtii can serve
as a model system for understanding the fundamentals of
lipid synthesis and regulation. Lipid production, like theproduction of other carbohydrate-based storage compounds,is also often dependent on environmental conditions,some of which await elucidation and development.
A possible drawback of C. reinhardtii is the fact that
nuclear expression of foreign genes is still problematicdue to codon bias (Heitzer et al., 2007), RNA silencing(Cerutti et al., 1997), and positional effects (Ferrante etal., 2008). However, strategies to address these issues arebeing developed, and stable and successful expressionof foreign genes in C. reinhardtii has been recently beenreported (Neupert et al., 2009; Ferrante et al., 2008).
Chloroplast transformants are also stable, and chloroplast
protein expression systems are well developed.
Chlorella is another well-studied genus of green algae,
and some species are abundant lipid producers. In
C. protothecoides, the addition of an external carbon source
induces heterotrophic growth, which increases both growthrate and lipid production, resulting in greater than 50%
dry weight lipid (Xu et al., 2006). The genome sequenceof Chlorella NC64A was recently completed.2 Several
examples of Chlorella transformation have been reported,
although the stability of the expression of the foreign
genes is still questionable (Leon and Fernandez, 2007 ).
Dunaliella salina has several useful characteristics forlarge-scale biofuels production. It produces abundant
lipids (Weldy and Huesemann, 2007), and because
it has outstanding salt tolerance (from 0.1 M to nearsaturation), it can be grown under extreme conditions
that could reduce the growth of possible contaminatingorganisms. The genome sequence of D. salina iscurrently being determined (estimated size 130 Mb), andtransgenic strains have been reported (Li et al., 2007).
Diatoms were a major focus in the Aquatic Species Program
given their ability to accumulate high amounts of lipids(Sheehan et al., 1998). Diatoms are responsible for 20%of the total global carbon fixation (Armbrust et al., 2004),
suggesting favorable growth rates for biomass production.
A distinguishing feature of diatoms is their silica cell walls,

http://genome.jgi-psf.org/ChlNC64A_1/ChlNC64A_1.home.html
2. Algal Biology

21and their requirement for silicon as a nutrient for growth.
Silicon limitation is one trigger for lipid accumulationin diatoms. This is advantageous for studying the lipid
induction response, because silicon metabolism is notbelieved to be tightly coupled with the metabolism of othernutrients. Two diatom genome sequences are complete(Armbrust et al., 2004; Bowler et al., 2008), and four moreare underway.3 None of the sequencing projects has thus far
been focused explicitly on biofuels. Transgenic techniques
are well established for several diatom species (Dunahay etal., 1995; Apt et al., 1996; Fischer et al., 1999; Zaslavskaia
et al., 2000), and regulatory gene expression control
elements have been identified (Poulsen and Kroger, 2005).
With the development of robust gene silencing approaches
and possibly with homologous recombination, the genemanipulation toolkit for diatoms will be fairly complete.

Macroalgae
Macroalgae, or seaweeds, represent a broad group of
eukaryotic photosynthetic marine organisms. They are
evolutionarily diverse and abundant in the world’s oceans
and coastal waters. They have low lipid content as a
general rule but are high in carbohydrates that can beconverted to various fuels. Unlike microalgae, they are
multicellular and possess plant-like structural features.
They are typically comprised of a blade or lamina, thestipe, and holdfast for anchoring the entire structure to
hard substrates in marine environments. The life cycles
of macroalgae are complex and diverse, with different
species displaying variations of annual and perennial
life histories, combinations of sexual and asexual
reproductive strategies, and alternation of generations.
Macroalgae are historically classified as Phaeophyta(brown algae), Chlorophyta (green algae), and Rhodophyta(red algae) on the basis of their predominant pigments.
Currently, taxonomic affinities are under re-examination
with the use of molecular tools and phylogenetic
markers. As such, the status of macroalgal systematics
is in a state of flux (Ali et al., 2001; Baldauf, 2003).
In general, each of the major macroalgal groups has
affinity with corresponding microalgal forms. For
example, the brown macroalgae such as the kelps areclassified as Heterokonta within the Chromalveolata,
which includes diatoms. Green macroalga such as Ulva
(also known as sea lettuce) are classified together with
common green microalgae such as Chlamydomonas
and Chlorella as Chlorophyta. Red macroalgae suchas Porphyra spp. also have microalgal counterparts,
such as the unicellular alga Porphyridium cruentum.

3

http://www.jgi.doe.gov

22

2. Algal Biology

Advances in seaweed cell and molecular biology are
currently being applied toward a better understandingof seaweed genetics and cell function. For example,
restriction fragment length polymorphisms (RFLPs) andrandom amplified polymorphic DNA (RAPD) analysis
are used in seaweed population genetics (Alberto et al.,
1999; Bouza et al., 2006; Dutcher and Kapraun, 1994; Hoet al., 1995; Niwa et al., 2005), and strain selection andcharacterization (Jin et al., 1997; Meneses and Santelices,
1999; Niwa et al., 2005). Use of gene-specific probes(Jacobsen et al., 2003; Moulin et al., 1999; Roeder et al.,2005), and expression profiling (Collen et al., 2006) arebeing applied to understand cell function in representativesof red, brown, and green seaweeds. Recombination ofexisting genes through selection and procedures suchas protoplast fusion will be the basis for new strain
creation where outplanting of individuals for growthin natural environments is a goal. Genome sequencing
projects will facilitate efforts such as global genomic
and proteomic profiling, constructing detailed pathways
for secondary metabolite production, and metabolicengineering of seaweed genes to create valuable products.

Considerations of Genetic
Modifications
Despite the great promise of GE algae, there is neverthelessa great deal of uncertainty regarding the need for or
the appropriateness of deploying these strains. For the
purpose of this report, GE algae are defined as strains
carrying coding sequences obtained from a foreign
species. Since the beginning of the deployment of GE
organisms, there have usually been built in safeguards toprevent the release of GE organisms to avoid potential
disruption of ecosystems. However, even with thesesafeguards, there have been several unintended releasesof GE organisms over the past 15+ years (GAO report,
2008). Understanding the basic biology that will informsuch aspects as lateral gene transfer, potential for toxin
production, potential for large-scale blooms and subsequentanoxic zone formation, and choice of cultivation methods
in terms of organism containment, are very important.
Despite the uncertainty regarding the development ofGE algae as production strains, development of genetic
tools is still imperative from a research standpoint.

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3. Algal Cultivation
than for open ponds raceways. However, it is important toacknowledge the advantages and disadvantages of bothphotoautotrophic cultivation approaches.

3.1 Cultivation Pathways
Microalgae and Cyanobacteria
Given the multiple pathways to cultivating microalgae
and cyanobacteria, it is premature to predict whether
algal cultivation in closed (e.g., photobioreactors), open
(e.g., open ponds) or hybrid systems will prevail in theindustry. It is, therefore, important that cultivation R&D
projects are closely associated with techno-economic(TE) analysis that can evaluate the cultivation systemin the context of upstream and downstream processing
to identify the best-suited cultivation system.
Broadly speaking, algae can be cultivated via
photoautotrophic or heterotrophic methods, both varying intheir challenges and advantages (Exhibit 3.1 compares thevarious features of both approaches).

Photoautotrophic Cultivation
For photoautotrophic cultivation strategies where algae
require light to grow and create new biomass, capital costs
for closed photobioreactor construction are currently higher

Traditionally, photobioreactors have suffered fromproblems of scalability, especially in terms of mixing andgas exchange (both CO2 and O2). Though photobioreactors
lose much less water than open ponds due to evaporation,
they do not receive the benefit of evaporative coolingand so temperature must be carefully maintained.
Open ponds, however, are subject to daily and seasonalchanges in temperature and humidity. Photobioreactors
are unlikely to be sterilizable and may require periodic
cleaning due to biofilm formation, but long-term culture
maintenance is likely to be superior to that in open ponds
where contamination and “foreign” algae are more
readily introduced. Photobioreactors can also provide ahigher surface to volume ratio and so can support higher
volumetric cell densities, reducing the amount of water thatmust be processed and thus the cost of harvest (Christi,2007). Both types of cultivation systems must contend withmaximizing light exposure. Many of these issues are being
addressed through improved material usage and enhanced

Exhibit 3.1 Comparative features of microalgal cultivation approaches

ClosedPhotobioreactors
Photoautotrophic
Cultivation

Open Ponds

Heterotrophic
Cultivation

ADVANTAGESCHALLENGES• Less loss of water than open ponds• Superior long-term culture
maintenance• Higher surface to volume ratio can
support higher volumetric celldensities• Scalability problems• Require temperature maintenance as they
do not have evaporative cooling• May require periodic cleaning due tobiofilm formation• Need maximum light exposure• Evaporative cooling maintains
temperature• Lower capital costs• Subject to daily and seasonal changes intemperature and humidity• Inherently difficult to maintainmonocultures• Need maximum light exposure• Easier to maintain optimal conditions
for production and contamination• Cost and availability of suitable
prevention
feedstocks such as lignocellulosic sugars• Opportunity to utilize inexpensive•
Competesfor feedstocks with otherlignocellulosic sugars for growthbiofuel technologies• Achieves high biomass
concentrations
3. Algal Cultivation29

engineering designs. Though TE analyses for both open
pond and photobioreactor systems have been published orpresented (see Chapter 10), much of the information used
for these analyses is based on assumptions or proprietarydata. As a result, it remains to be seen which system
will be preferred at scale over long periods of operation.
Additionally, in hybrid systems, photobioreactors could
play a critical role as breeder/feeder systems linked toopen raceways, providing high cell density algal inocula
for production ponds (Ben-Amotz, 1995) or a series oflinked turbidostats or chemostats (Benson et al., 2007).

Heterotrophic Cultivation
In heterotrophic cultivation, algae are grown without lightand are fed a carbon source, such as sugars, to generate
new biomass. This approach takes advantage of matureindustrial fermentation technology, already widely used to
produce a variety of products at large scale. Heterotrophic
cultivation presents a different set of advantages andchallenges compared with photoautotrophic methods.
Optimal conditions for production and contamination
prevention are often easier to maintain, and there is thepotential to utilize inexpensive lignocellulosic sugars foralgal growth. Heterotrophic cultivation also achieves highbiomass concentrations that reduces the extent and cost of
the infrastructure required to grow the algae (Xu, 2006).
The primary challenges with this approach are the cost andavailability of suitable feedstocks such as lignocellulosic
sugars. Because these systems rely on primary productivity
from other sources, they could compete for feedstocks
with other biofuel technologies. A related approachis mixotrophic cultivation, which harnesses both thephotoautotrophic and heterotrophic ability of algae.

Macroalgae
Macroalgae require unique cultivation strategies. Modern
macroalgal cultivation technology that is based on the useof artificially produced seed as a source of propagules has
been in practice since the 1950s. Typically, seeds grownin greenhouses are attached to substrates (usually rope
structures), then reared to plantlet size and transplanted
to coastal farms for grow-out to harvestable size.
Modern tools developed in the larger plant breeding
community are now available to seaweed biologists
and culturalists to advance the vegetative propagationof seaweeds through cell and tissue culture techniques.
Although the field is still at an early stage of development,
the micropropagation of plants is a concept that has
been adopted by seaweed biologists (Garcia-Reina et al.,1991). Demonstrations of successful callus formation andplantlet regeneration have been reported in commercially
important seaweeds such as Undaria (Kawashima and30

3. Algal Cultivation

Tokuda, 1993) and the phycocolloid-producing seaweeds
Gracilaria, Hypnea, Sargassum, Turbinaria, andGelidiella (Collantes et al., 2004; Kumar et al., 2004;
Kumar et al., 2007). Growth of plantlets regenerated fromprotoplasts is possible in both the laboratory (Dipakkore
et al.et al., 2005, Reddy et al.et al., 2006) and field(Dai et al., 2004; Dai et al., 1993). Recent studies haveshown that Porphyra, in particular, appears especiallypromising for growing plants from protoplasts (Dai etal., 2004; Dai et al., 1993; Dipakkore et al., 2005).
Macroalgae can be cultivated in off-shore, near-shore, orin open pond facilities. The operation of large offshore
seaweed farms was initially tested by the Marine
Biomass Program through several deployments of kelp
on growth structures in deep waters off the coast ofSouthern California; using artificially upwelled water
as a nutrient source. While it was determined that such
structures would support growth of kelp, difficulties wereencountered with the stability of either the structures
themselves or the stability of the attachment of kelp tothe structures. However, modern prototypes for offshore
growth of the kelp, Laminaria hyperborean, have beensuccessfully tested in the North Sea (Buck and Buchholz,
2004; Buck, 2005), thus providing optimism for future
efforts. Near-shore coastal environments are alreadybeing exploited by countries like China, Japan, and Chile,which have viable seaweed aquaculture industries. In
the United States and Europe, environmental regulations
and popular resistance against use of coastal regions foraquaculture represent challenges that will need to be
overcome due to the conflicting uses of coastal zones.
Land-based pond systems have also been considered
for macroalgal cultivation (Friedlander, 2008; Hanisak,1987), both as free-standing algal farms and in an
integrated aquaculture scenario in co-culture with finfish
and mollusks. In the latter, wastes from the other species
represent a nutrient supply for the macroalgae. Porphyra
spp., Saccharina latissima and Nereocystis luetkeana havebeen successfully co-cultured with salmonid fish species(Bruton et al., 2009). Advantages of the land-based systems
over those in water have been listed as 1) ease of plant
management; 2) use of plants with or without holdfast
structures; 3) ease of nutrient application without dilution;4) avoidance of open sea problems such as bad weather,disease, and predation; and 5) possibility of farm operations
located in close proximity to conversion operations(Chynoweth, 2002). For contribution to a biofuels
marketplace, considerable scale-up from current activities,
improvement in strain selection, and major technologicalimprovements in efficiency of water movements andpond construction costs are needed (Friedlander, 2008).

Other options for algal cultivation are being investigatedincluding the harvesting of naturally occurring marine algal
blooms, and the use of algal mat or biofilm cultivation
schemes. It should be noted that, especially in open
systems, monocultures are inherently difficult to maintainand require significant investment in methods for detection
and management of competitors, predators, and pathogens.
One possible approach to contend with this is to cultivatea mixed or natural assemblage of organisms in an attempt
to maximize total harvested biomass. This model would
require a downstream biorefinery capable of processing
simple and complex carbohydrates, proteins, and lipids
into a variety of useful products. Nutrients, including
CO2, must also be managed in a way that balances
productivity and pathogen sensitivity with the plasticity ofalgal physiological adaptation. The cost-benefit analysis
of supplemental CO2 in large-scale algal cultivation
has yet to consider the intricacies of biological carbon
concentration mechanisms (Wang and Spalding, 2006 ).

3.2 Scale-Up Challenges
The inherent difficulties of scaling up from laboratory
to commercial operations present both technicaland economic barriers to success. Because of thepervasiveness of issues related to scale, an investment
in “open source” test bed facilities for public sector
RD&D may foster more cultivation research.
Nutrient sources and water treatment/recycling aretechnically trivial and inexpensive at small scales andyet represent major technical and economic problems at
commercial scales. Tapping into existing agricultural or
municipal waste streams will lower nutrient costs but could
introduce unacceptable pathogens, chemical compounds, or
heavy metals into the biomass stream (Hoffman et al., 2008;
Wilson et al., 2009). Additionally, little is known about
artificial pond ecology or pathology, and investigation into
these areas will be important for the development of largescale cultivation risk mitigation and remediation strategies.
Four broad cultivation challenges have emergedthat are important to address for economically
viable, commercial-scale algal cultivation:• Culture stability;• Standardized metrics for system-levelproductivity analysis;• Nutrient source scaling, sustainability andmanagement; and• Water conservation, management, and recycling.

Stability of Large-Scale Cultures
Systems for large-scale production of biofuels from algae
must be developed on scales that are orders of magnitudelarger than all current worldwide algal culturing facilities
combined. In certain cultivation systems, it will bechallenging to maintain algal monocultures on this scale;it may become necessary to understand and manage thecommunities that will be present. Some members of thecommunity will be of positive value, such as those thatcan scavenge and recycle nutrients or synthesize essential
vitamins. Others will compete for shared resources, andstill others will cause culture disruption. One of the moreworrisome components of large-scale algae cultivationis the fact that algal predators and pathogens are both
pervasive and little understood (Becker, 1994; Honda etal., 1999; Cheng et al., 2004; Brussaard, 2004). Fungal
and viral pathogens are common, although current
understanding of their diversity and host range is very
limited. Wilson et al., (2009) point out that though there
may be between 40,000 and several million phytoplankton
species, there have only been 150 formal descriptions ofphycoviruses. Chytrid fungi have also been known to cause
the collapse of industrial algal cultivation ponds (Hoffman
et al., 2008), but very little is known about host specificity
and even less is known about host resistance mechanisms.
Important questions concerning this threat
to large-scale algal cultures include:• Are agricultural or municipal waste streams—apotentially significant source of nutrients for algal
cultivation—actually a liability because of significant
reservoirs of algal pathogens and predators?
• To what extent will local “weedy” algae invade
and take over bioreactors and open ponds?
• What prevention or treatment measures
might limit such takeovers?
Methods for rapid, automated or semi-automated biologicaland chemical monitoring in production settings willbe essential for assessing the health and compositional
dynamics of algal cultures. The methods must be sensitive,
selective, and inexpensive, as well as potentially provide
for real-time monitoring. “Environmental” DNA sequence
analysis can contribute to the development of PCR-based(Zhu et al., 2005; Boutte et al., 2006; Viprey et al., 2008)or flow-cytometry-based taxonomic assays, e.g., TSAFISH (Marie et al., 2005). Continuous monitoring will
be necessary in open systems since seasonal variation incompetitors, predators, and pathogens is expected (Hoffman
et al., 2008; Rittmann et al., 2008; Wilson et al., 2009).

3. Algal Cultivation

31

Furthermore, developing an understanding of pond
speciation, predator-prey relationships, and ecology
dynamics will be important. Early detection schemes forinvasive species, predators, and pathogens will be a key
to the success of remedial actions and for determining
when decontamination and subsequent restart procedures
represent the only alternative. This information will
also inform efforts at developing robust, competitive
production strains. The frequency of contamination
events that require decontamination/restarts will be an
important parameter in the cost of production because of
productivity lost during down time, and because of thepotential need to either discard or treat the contaminatedculture prior to water recycle. The development ofchemical treatments or physiological adaptations andgenetic modifications of production strains may become
necessary. Dynamic pond monitoring will be importantfor both wild-type and genetically modified algae,
whose competitiveness in the field cannot be accurately
predicted. Thus, a significant investment toward basic
research in multi-trophic, molecular-level algal ecology
will be an important component of the investment
portfolio required for developing the potential of algae.

System Productivity
Research at the interface between basic algal biology andcultivation science and engineering will yield significant
improvements in productivity while at the same time
lower the cost of production. Utilization of existing andnew knowledge related to the physiological regulation oflipid or carbohydrate accumulation coupled with scalable
cultivation schemes should lead to enhancements in
productivity. For example, nitrogen nutrition has long
been known to affect lipid accumulation in phytoplankton(Ketchum and Redfield, 1938; Shifrin and Chisholm
1981; Benemann and Oswald, 1996; Sheehan et al.,1998). More recent data suggest that high salt and highlight stress in some marine phytoplankton may also
result in increases in lipid content (Azachi et al., 2002).
From a productivity standpoint, supplemental CO2 haslong been known to increase algal growth rate, andthis area is receiving new attention from the search forrenewable, sustainable fuels. New approaches are split
between using algae to scrub CO2 from emission gasses(Rosenberg et al., 2008; Douskova et al., 2009) and a focus
on better understanding the mechanisms of biological
CO2 concentration from ambient air (Lapointe et al.,2008; Spalding 2008). There is justification to carry out
R&D in both areas, as siting requirements for efficientalgal cultivation may rarely coincide with high-volume
point sources of CO2 (see Chapter 9). The cost of CO2

32

3. Algal Cultivationtransportation and the volatile market for carbon credits will
be a major challenge for TE feasibility studies; diverging
business models are already apparent on these issues.
Better methods to detect the amount of desired fuelprecursor produced will be required to assess the
productivity of potential strains. Fluorescent and Nuclear
Magnetic Resonance-based methods for rapid lipid content
screening in algae have been developed and applied tomany different types of phytoplankton with mixed results(Cooksey et al., 1987; Reed et al., 1999; Eltgroth et al.,2005; Gao et al., 2008). These tools, as well as others suchas Near Infra Red spectroscopy, need to be more rigorously
studied, automated, and adapted for rapid, inexpensive
high-throughput monitoring. The synthesis of new nontoxic, permeable, fluorescent indicators other than Nile Red
are also important. For example, derivatives of the Bodipy
molecule with higher lipophilicity or lower quantum yields
in aqueous solvent may prove to be more reliable indicatorsof algal lipid contents (Gocze and Freeman, 1994).
There is an immediate need to standardize productivity
models and establish protocols for measurement of yields,
rates, densities, metabolites, and normalization. Alongwith standards, coordinated research amongst analyticalchemists, physiologists, biochemists, and genetic,chemical, civil and mechanical engineers is needed for
rapid progress. National and international efforts toward
generating quality assurance policy standards early onin the development of an algal biofuel industry could
facilitate the deployment of algal based-biofuels by
ensuring consistent, fit-for-purpose fuels, and products.

Nutrient Sources,
Sustainability, and Management
Nutrient supplies for algal cultivation have a sizeable
impact on cost, sustainability, and production siting.
The primary focus is the major nutrients – nitrogen,phosphorous, iron, and silicon (in the case of diatoms).
Nitrogen, phosphorous, and iron additions represent asignificant operating cost, accounting for 6-8 cents per
gallon of algal fuel in 1987 U.S. dollars (Benemann and
Oswald, 1996). This calculation takes into account a 50%
rate of nutrient recycle. Phosphorous appears to be anespecially important issue as there have been calculations
that the world’s supply of phosphate is in danger of runningout (Abelson, 1999). Requirements for additional nutrients,
such as sulfur, trace metals, vitamins, etc. must also be
considered, but vary depending upon the specific strain andwater source chosen. The use and availability of carbonbased nutrients for heterotrophic growth will also affectthe economics and sustainability of such systems. Strain
selection should take nutrient requirements into account.

Nitrogen is typically supplied in one of three forms:
ammonia, nitrate, or urea. The ideal form of nitrogenis a function of relative costs and the specific strain’s
biology. Because synthetic nitrogen fixation processes
utilize fossil fuels (particularly natural gas), costs are tied
to fossil fuel prices, and the very large required energy
inputs should be accounted for in life cycle analyses.
It is possible to consider the use of nitrogen-fixing
cyanobacteria as a way to provide nitrogen biologically,
perhaps in co-culture with eukaryotic algae. However,such a scheme will certainly have some impact on overall
productivity levels as photosynthetic energy could
be diverted from carbon fixation to nitrogen fixation,
which may or may not be compensated for by the “free”
nitrogen. Note also that flue gas fed to algal cultures may
provide some of the nitrogen and sulfur needed from
NOx and SOx (Doucha, 2005; Douskova et al., 2009).
Careful control of nutrient levels is also critical. Limitationof a key nutrient will have serious impacts on biomass
productivity, but it may also be desirable to use nutrient
limitation (e.g., nitrogen, phosphorous, or silicon) as ameans to induce oil accumulation in the cells (Sheehan
et al., 1998). On the other hand, too much of a particularnutrient may prove toxic. Also, unused nutrients inthe culture medium pose a problem for waste water
discharge. Although economics dictate that the bulk ofwater derived from the harvesting step must be returnedto the cultivation system (where remaining nutrientscan feed subsequent algal growth), a certain amountof “blowdown” water must be removed to prevent saltbuildup. If this blowdown water contains substantial
nitrogen and phosphorous, disposal will become a problem
due to concerns of eutrophication of surface waters.
Finding inexpensive sources of nutrients will be important.
Reagent grade sources of nutrients could make the priceof a gallon of algal fuel cost-prohibitive. Agriculturalor commodity-grade nutrients are more applicable, but
their costs are still significant. Therefore, utilizing thenutrient content of municipal, agricultural, or industrial
waste streams is a very attractive alternative. Currently,
algae are used in some wastewater treatment facilities
because of their ability to provide oxygen for the bacterial
breakdown of organic materials and to sequester nitrogenand phosphorous into biomass for water clean-up.
Utilizing agricultural run-off also poses economic benefits
by preventing eutrophication. A potential problem withthis approach however is the impact on facility siting.
Wastewater treatment facilities, for example, tend to be nearmetropolitan areas with high land prices and limited landavailability, and it is not practical to transport wastewaterover long distances. Further research into the availability
and compatibility of wastewater resources is warranted.

Another approach to reduce nutrient costs is to pursue
a diligent recycle. The final fuel product from algal oil
contains no nitrogen, phosphorous, or iron; these nutrientsend up primarily in the spent algal biomass. From asustainability perspective, nutrient recycle may prove
to be more valuable than using the spent biomass for
products such as animal feed. If the biomass residues are,for example, treated by anaerobic digestion to produce
biogas, then most of the nutrients will remain in thedigestor sludge and can be returned to the growth system(Benemann and Oswald, 1996). The processes throughwhich these nutrients are re-mobilized and made available
for algal growth are not well understood. This may beparticularly problematic for recycling of silicon, which is
a component of the diatom cell walls. In the future, it may
also become necessary to expand the limits of analysis
to include recycling of nutrients from animal waste.
Nutrient sourcing and the control of nutrient
levels are vitally important factors for cultivation
economics, productivity, and sustainability issues.
Important research areas therefore include:• TE and life cycle analysis to understand the cost,energy, and sustainability implications of various
nutrient sources and recycling scenarios• Studies to explore the mechanisms of nutrient
recycling, e.g., from anaerobic digestion sludges• Geographic Information System (GIS) analyses ofwastewater resources to understand availability,
compatibility with cultivation sites, and potential
impact of such sources on algal biofuels production

Water Management,
Conservation, and Recycling
One of the main advantages of using algae forbiofuels production is their ability to thrive in water
unsuitable for land crops, such as saline water fromaquifers and seawater. At the same time, however,water management poses some of the largest issues
for algal biofuels. If not addressed adequately, watercan easily become a “show-stopper,” either because ofreal economic or sustainability problems or because ofloss of public support due to perceived problems.
With large cultivation systems, water demands will beenormous. For example, a hypothetical 1 hectare (ha), 20
cm deep open pond will require 530,000 gallons to fill.
In desert areas, evaporative losses can exceed 0.5 cm perday (Weissman and Tillet, 1989), which is a loss of 13,000
gallons per day from the 1 ha pond. Though the water used
to initially fill the pond can be saline, brackish, produced
3. Algal Cultivation

33

water from oil wells, municipal wastewater, or other lowquality water stream, the water being lost to evaporation
is fresh water, and continually making up the volume with
low-quality water will concentrate salts, toxins, and othermaterials in the culture. This can be prevented by adding
fresh water—a costly and often unsustainable option—orby disposing of a portion of the pond volume each day
as “blowdown.” The amount of blowdown required forsalinity control is dependent upon the acceptable salt levelin the culture and the salinity of the replacement water.
Conservation of water can be addressed to some extent
through facility design and siting. An advantage of
closed photobioreactors over open ponds is a reduced
rate of evaporation. The added cost of such systems must
be balanced against the cost savings and sustainability
analysis for water usage for a given location. Note howeverthat evaporation plays a critical role in temperature
maintenance under hot conditions through evaporative
cooling. Closed systems that spray water on the surfaces
or employ cooling towers to keep cultures cool will lose
some if not possibly all of the water savings of such
systems under these conditions (Flickinger,1999). A criticalpart of the analysis that goes into siting an algal facility
will be to analyze the “pan evaporation” rates at specificsites in conjunction with water cost and availability.
Water recycling is essential, but the amount that canbe recycled depends on the algal strain, water, process,and location. Some actively growing algal cultures candouble their biomass on a daily basis, meaning that half
the culture volume must be processed daily. This is anenormous amount of water (260,000 gallons per day in the
1 ha example above). To contain costs, it is desirable torecycle most of that water back to the culture. However,accumulated salts, chemical flocculants used in harvesting,or biological inhibitors produced by the strains themselves
could impair growth if recycled to the culture. Furthermore,moving around such large volumes of water is very
energy-intensive and can impose a significant cost.
Treatment may be essential for water entering and exiting
the process. Incoming water (surface water, groundwater,
wastewater, or seawater) may be suitable as is, or may
require decontamination, disinfection, or other remediation
before use. The blowdown water exiting the process will
also most likely require treatment. Disposal of the spentwater, which could contain salts, residual nitrogen andphosphorous fertilizer, accumulated toxics, heavy metals(e.g., from flue gas), flocculants, and residual live algal
cells, could pose a serious problem, and treatment (e.g.,desalination, activated charcoal filtration, etc.) of therecycled stream could be cost-prohibitive. Surface disposal
and reinjection into wells may be an option as regulated
34

3. Algal Cultivationby the Environmental Protection Agency and alreadypracticed by the oil industry, but live cells could adversely
affect biodiversity of neighboring ecosystems or resultin the dissemination of genetically modified organisms.
Sterilization of blowdown water, however, would be avery costly and energy-intensive proposition.
Because of the importance of issues surrounding the useof water, research in the following areas is warranted:• GIS analysis of water resources, including saline
aquifers, and their proximity to utilizable cultivationsites that may have lower pan evaporation rates• Understanding the long-term effects of drawing
down saline aquifers, including the geology of theseaquifers and associations with freshwater systems• Analysis and definition of the regulatory landscapesurrounding discharge of water containing various
levels of salt, flocculants, toxins (including heavy
metals), and live cells• Developing cultivation systems with minimal
water consumption. This could include reducing
evaporative cooling loads through such strategies
as selecting thermotolerant strains of algae• Studying water recycle and methods to maximize
recycle (and minimize blowdown), while effectively
managing the accumulation of salt and other inhibitors• Investigating ways to reduce the cost of water
treatment, makeup water/recycle, and water
movement (pumping costs)

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36

3. Algal Cultivation

4. Downstream Processing: Harvesting and Dewatering
Conversion of algae in ponds, bioreactors, and off-shore
systems to liquid transportation fuels requires processing
steps such as harvesting (Dodd and Anderson, 1977;
Butterfi and Jones, 1969; McGarry and Tongkasa, 1971),
dewatering, and extraction of fuel precursors (e.g., lipids
and carbohydrates). These energy-intensive processes are
only now being recognized as critically important. Cultureswith as low as 0.02 - 0.07% algae (~ 1 gm algae/5000
gm water) must be concentrated to slurries containing
at least 1% algae given the known processing strategies(Borowitzka, 1988). The final slurry concentration will
depend on the extraction methods employed and will
impact the required energy input. As the desired percentage
of dry biomass increases, energy costs climb steeply. Finalslurry concentration also impacts plant location becauseof transportation, water quality, and recycling issues. A
feasible algae-to-fuel strategy must, therefore, consider theenergy costs and siting issues associated with harvestingand dewatering. Addressing these issues requires carefulanalysis of engineering designs, combined with RD&D todevelop specific processing technologies to support those
designs and a fundamental understanding of how algal
biology can impact harvesting and dewatering strategies.
Processing technologies depend on the algal feedstocks
being considered. Processes that pertain to unicellular algae
are quite different from the approaches applicableto macroalgae.

4.1 Approaches for Microalgae
Harvesting
Flocculation and Sedimentation
Microalgae and cyanobacteria remain in suspension inwell-managed high growth rate cultures due to theirsmall size (~1 to 30 µm). This facilitates the transport ofcells to the photoactive zone through pond or bioreactor
circulation. Their small sizes, however, make harvesting
more difficult. Flocculation leading to sedimentation occurs
naturally in many older cultures. In managed cultures, someform of forced flocculation usually involving chemical
additives, is required to promote sedimentation at harvest.
A number of different forms of forced flocculation havebeen employed. Chemical additives that bind algae orotherwise affect the physiochemical interaction between
algae are known to promote flocculation (Lee et al.,
1998; Knuckey et al., 2006; Pan et al., 2001). Alum, lime,
cellulose, salts, polyacrylamide polymers, surfactants,
chitosan, and other man-made fibers are some chemical
additives that have been studied. Manipulating suspension

pH with and without additives is also effective, andautoflocculation in the form of photosynthetically driven
CO2 depletion for pH control has been studied (Sukenik
and Shelaf, 1984). Bioflocculation where algae are cocultured with another organism that promotes sedimentation
has also been considered (Lavoie and Delanoue, 1987).
Finally, electroflocculation and electrocoagulation offer
the advantages of no added chemicals (Chen, 2004;
Mollah et al., 2004; Poleman and Pauw, 1997).
Optimizing flocculation methods, type, mixtures,concentrations, and chemistry to maximize algae recovery
will very likely depend on strain selection, the mechanismof algae-flocculant interactions, and on empiricaldeterminations in particular processes. It is possible toimagine selecting/designing strains to aggregate on cue
or designed with a particular flocculant interaction inmind. Culture manipulation techniques, therefore, may
be useful for promoting flocculation. Future research inflocculation chemistry must take into account the following:• Chemical flocculant recovery techniques are required
to minimize cost and control water effluent purity.
• The effect of residual flocculant or pH manipulationin recycled water on culture health and stability
and lipid production must be understood andcontrolled. Likewise, the presence of flocculant infurther downstream extraction and fuel conversion
processes must be understood and controlled.
• The environmental impact of flocculant or pH
manipulation in released water effluent, and fuelconversion and use must be considered.
• Bioflocculation, electroflocculation, andelectrocoagulation must be scaled-up with cost andenergy analysis.
• Optimized sedimentation tank designs with integration
into further downstream dewatering techniques, water
recycling and flocculate recovery are required.

Flocculation and Dissolved Air Flotation
Flocculation and Dissolved Air Flotation (DAF) wasestablished for sewage treatment and later studied inalgae harvesting (Sim et al., 1988; Botes and Vanvuuren,
1991; Edzwald, 1993; Phochinda and White, 2003;
Kwak et al., 2005; Bare et al., 1975; Koopman and
Lincoln, 1983). Flocculation is used to increase thesize of the algae aggregates, and then air is bubbled
4. Downstream Processing: Harvesting and Dewatering37

through the suspension causing the algal clusters
to float to the surface. The algae-rich top layer isscraped off to a slurry tank for further processing.
All of the issues arising from the use of flocculants
for sedimentation (e.g., floc optimization, water andalgae purity, and flocculant reclamation) are also
encountered in flocculation and DAF. In addition toflocculant efficiency, recovery is largely dependent on
bubble size and distribution through the suspension.
DAF facilities require optimized integration with any
engineered design for further downstream processing.

Filtration
Solid/liquid filtration technologies are well studied,and filtration without prior flocculation can be used
to harvest and dewater algae (Ferguson et al., 1995;
Downing et al., 2002; Saidam and Butler, 1996).
Microalgae and cyanobacteria present unique filtration
challenges because most strains considered for energy
feedstocks have cell diameters less than 10 µm.
Filtration is conceptually simple but potentiallyvery expensive, and can be optimized throughfurther understanding of several issues:• The filter pore size is critically important as it isdefined by the size of the algae species and algae
aggregation rate. Small algae pass through larger
pores decreasing filter efficiency. Decreasing poresize, however, leads to blinding, the blocking of filter
pores, and reduction of filtering rates. Culture purity
becomes important as a distribution of microorganism
size will affect filtration efficiency and blinding rates.
• Filter material also influences filtration and recovery
efficiency. Materials can be used that optimize filtrationand have the ability to remove the algae later. For
instance, filter materials with controlled hydrophobicity
and/or algae affinity can be developed. Durability andblinding are also issues.
• Filtration design is an important variable with both
static and dynamic filtering operations. Moving filters
have been used in drum and cylinder press designs(Oswald, 1991). Power costs will certainly influence
design.
• An important step is recovering the algal biomass fromthe filter. Washing the filter is one practice, but doing
so leads to re-dilution of the product. Filtration designs
should consider minimal or no washing requirements.

38

4. Downstream Processing: Harvesting and Dewatering

Centrifugation
Centrifugation is widely used in industrial suspension
separations and has been investigated in algal harvesting(Molina et al., 2003). The efficiency is dependent on
the selected species (as related to size). Centrifugation
technologies must consider large initial capital equipment
investments, operating costs, and high throughput
processing of large quantities of water and algae. The
current level of centrifugation technology makes thisapproach cost-prohibitive for most of the envisioned
large-scale algae biorefineries. Significant cost andenergy savings must be realized before any widespread
implementation of this approach can be carried out.

Other Harvesting Techniques
A number of other techniques at various stages of
R&D have been proposed to harvest and dewater
microalgae. These include, but are not limited to, theuse of organisms growing on immobilized substrates
where the amount of initial water is controlled andthe growth substrate can be easily removed; acoustic
focusing to concentrate algae at nodes; manipulation ofelectric fields; and bioharvesting, where fuel precursors
are harvested from higher organisms (e.g., shrimp andtilapia) grown with algae (Johnson and Wen, 2009).

DryingDrying is required to achieve high biomass concentrations.
Because drying generally requires heat, methane drum
dryers and other oven-type dryers have been used.
However, the costs climb steeply with incremental
temperature and/or time increases. Air-drying is possible
in low-humidity climates, but will require extra space andconsiderable time. Solutions involving either solar or windenergy are also possible.

4.2 Approaches for Macroalgae
Harvesting
Currently, of the roughly 1.6 million dry metric tonsof total seaweed harvested worldwide, about 90% isderived from cultivated sources (Roesijadi et al., 2008).
Manual harvesting is common for both cultivated andnatural systems, and mechanized harvesting methods,
which can involve mowing with rotating blades, suction,
or dredging with cutters, have also been developed.
Invariably, such mechanized harvesters require boats
or ships for operation. Modern seaweed harvesting
vessels can be equipped with pumps to direct harvested
seaweeds directly into nets or other containment structures(Ugarte and Sharp, 2001). Application of mechanicalharvesters in European seaweed operations have been
described in a recent feasibility analysis for seaweeds asa biofuels feedstock in Ireland (Bruton et al., 2009).
The concept of large off-shore macroalgae farms andassociated biorefineries has from the outset included
mechanized harvesting techniques. The exact nature ofsuch mechanization will obviously depend on the formof cultivation and type of algae being cultured. For
example, attached forms that tend to stand upright, such
as Macrocystis, may be amenable to mowing. Floating
seaweeds such as Sargassum spp. could be cultivated infloating pens, and low growing attached forms such as
Gracilaria will require different approaches compatible with
their growth characteristics. In forms such as Laminaria
grown on off-shore rings (Buck and Buchholz, 2004),
harvesting may require retrieval and transport to shore.
Similarly, cultivation in land-based pond systems will
require technology appropriate for that mode of culture.
As a result of growing concern about the potential
environmental consequences of harvesting natural
populations of seaweed near-shore, strict regulations
have been put in place in some countries (Pringle andTseng, 1989). To manage seaweed harvests, laws havestipulated the percentages of harvestable stock allowed tobe harvested and the intervals between harvests to allow
growth and recovery of biomass (Ugarte and Sharp, 2001).
The establishment of large offshore seaweeds may alleviatepressure from near-shore environments and create market
opportunities for products apart from fuels, although
issues related to sustainability and potential environmental
consequences will need to be carefully evaluated.

Preprocessing
The general preprocessing requirements for macroalgal
biomass prior to extraction or direct conversion havebeen categorized as follows (Bruton et al., 2009):• Removal of foreign objects and debris, e.g., by washing• Milling• Dewatering
Seaweeds immediately following harvest can havestones, sand, litter, adhering epifauna and other forms ofdebris that should be removed before further processing.
Screening for debris is considered mandatory, withthe degree of screening dependent on the mode ofculture and end-use. Algae that are grown in suspension
culture, as opposed to attached to the bottom culture,
will likely have less debris, and the amount of debris
will likely have less impact in procedures that canutilize whole seaweeds (Bruton et al., 2009).

Milling is used to reduce seaweeds to particle sizes that are\more efficiently processed. Smaller particles, with higher
surface area to volume ratios, will have higher reaction
efficiency during anaerobic digestion for biogas,
fermentation for alcohols, and hydrothermal liquefaction
for bio-oils.
Macroalgae have less of a demand for dewatering aspart of the pretreatment process. Anaerobic digestion,
fermentation, and hydrothermal liquefaction have either
a high tolerance or requirement for water. Dewatering
may be more important as a method to increase shelf-lifeand reduce weight and associated transportation costs if
algae are to be transported from sites of harvest to distantprocessing plants (Bruton et al., 2009). Dewatering toabout 20 - 30% water content is noted to have a stabilizing
influence, which is beneficial for transportation and otherprocesses requiring further drying (Bruton et al., 2009). In
anaerobic digestion and fermentation, shredded or milled
macroalgal biomass can go directly into either reactions
or extractions. Hydrothermal conversions are suited forwet biomass and become efficient at 15 - 20% solids or
80 - 85% water content (Peterson et al., 2008). Althoughsome dewatering of seaweeds whose water content
approaches 90% may be necessary, the exact ratio of water
to solids for marine biomass remains to be determined.

4.3 Systems Engineering
While specific process technologies have been studied,breakthroughs are still needed in each, given theimportance as well as current cost and achievablescale of harvesting and dewatering. Further, newstrategies should be developed to combine and integratethese processes in order to take an algae culture andconvert it into slurry of a specific concentration.
This has yet to be demonstrated on a commerciallyrelevant scale and remains a significant challenge.
A critical gap is the energy requirements of these processes
are not only largely unknown but unbounded. This has
important implications for plant design to answer simple
questions like “What percentage of the total plant energy
requirements or what percentage of that made available byalgae must be directed toward harvesting and dewatering?”.
Ultimately, a unit operations analysis of energy input
for a range of dry weight content based on extractionneeds is required with consideration of capital equipment
investments, operations, maintenance, and depreciation.
The cost of harvesting and dewatering will depend on the
final algae concentration needed for the chosen extraction
method. This will likely be a significant fraction of thetotal energy cost of any algae-to-fuel process and asignificant fraction of the total amount of energy available
4. Downstream Processing: Harvesting and Dewatering

39

from algae. A quick and preliminary energy balanceexample shown below provides some food for thought
regarding harvesting and dewatering technologies.

Preliminary Look at Energy Balance
The energy content of most algae cells is of the orderof 5 watt-hours/gram if the energy content of lipids,
carbohydrates, and proteins and the typical percentage
of each in algae are considered (Illman et al., 2000). It
is possible to estimate the energy requirements in watthours/gram of algae for harvesting, de-watering, anddrying as a function of the volume percentage of algae
in harvested biomass. The energy requirements forflocculation and sedimentation and the belt filter press are
expected to be minimal. However, based on the latent heatof vaporization of water at 0.54 watt-hours/gram, energybalance can become an issue in systems that propose
to take algal biomass and concentrate / dry it to enable
downstream processing and extraction because of thehigh volumes of water that must be evaporated away.
In spite of gaps in data precluding more detailed
analyses, algal biofuel production schemes at scale will
likely need to implement innovative technologies andintegrated systems in order to overcome this challenge.
Possible approaches may include developing strains ofalgae with much higher energy content than available
today, along with innovative solutions to lower theenergy intensity of harvesting and drying algae.

References
Bare, W.F.R., N.B. Jones, E.J. Middlebrooks. (1975). Algae removal using dissolved air flotation.
Water Pollution Control Federation Research Journal. 47(1), 153.
Borowitzka, Borowitzka, (1988). Large-scale algae culture systems. Micro-Algal Biotechnology. Cambridge University Press. 357-394.
Botes, V., L.R.J. Vanvuuren. (1991). Dissolved air flotation for the removal of algae and inorganic turbidity on a large-scale. Water
Supply: IWSA/IAWPRC Joint Specialized Conference on Coagulation Flocculation, Filtration, Sedimentation and Flotation. 9(1), 133.
Bruton, T., H. Lyons, Y. Lerat, M. Stanley, and M. B. Rasmussen. (2009). A review of the potential of marine
algae as a source of biofuel in Ireland. Sustainable Energy Ireland, Dublin, Ireland
Buck, B. H., and C. M. Buchholz. (2005). Response of offshore cultivated laminaria saccharina
to hydrodynamic forcing in the north sea. Aquaculture. 250, 674-691.
Butterfi, B.A., J. Jones. (1969). Harvesting of algae grown in agricultural wastewaters.
Transactions-American Geophysical Union. 50(11), 612.
Chen, G. (2004). Electrochemical technologies in wastewater treatment. Separation and Purification Technology. (38), 11.
Dodd, J.C., J.L. Anderson. (1977). Integrated high-rate pond algae harvesting system. Progress in Water Technology. 9(3), 713.
Downing, J.B., E. Bracco, F.B. Green, A.Y. Ku, T.J. Lundquist, I.X. Zubieta, W.J. Oswald. (2002). Low cost reclamation using theadvanced integrated wastewater pond systems technology and reverse osmosis. Water Science and Technology. 45(1), 117.
Edzwald, J.K. (1993). Algae, bubbles, coagulants, and dissolved air flotation. Water Science and Technology. 27(10), 67.
Ferguson, C., G.S. Logsdon, D. Curley, C. Ferguson. (1995). Comparison of dissolved air flotation and direct filtration.
Water Science and Technology. 31(3-4). 113.
Illman, Scragg, Shales. (2000). Increase in chlorella strains calorific values when grown in low nitrogen media.
Enzyme and Microbial Technology. (27), 631-635.
Johnson, M., & Wen, Z. (2010). Development of an attached microalgal growth system forbiofuel production. Applied Microbiology and Biotechnology, 85(3), 525-534.
Knuckey, R.M., M.R. Brown, R. Robert, D.M.F Frampton. (2006). Production of microalgal concentrations byflocculation and their assessment as aquaculture feeds. Aquacultural Engineering. 35(3), 300.
Koopman, B, E.P. Lincoln. (1983). Autoflotation harvesting of algae from high-rate pond effluents. Agricultural Wastes. 5(4), 231.
Kwak, D.H., S.J. Kim, H.J. Jung, C.H. Won, S.B. Kwon, et al. (2005). Removal of clay and blue-green algae particles through zeta
potential and particle size distribution in the dissolved air flotation process. Water Science and Technology: Water Supply. 6(1), 95.
Lavoie, A, J. Delanoue. (1987). Harvesting of scenedesmus-obliquus in wastewaters-auto-flocculation or bioflocculation.
Biotechnology and Bioengineering. 30 (7), 852-859.

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4. Downstream Processing: Harvesting and DewateringLee, S.J., S.B. Kim, G.S. Kwon, B.D. Yoon, H.M. Oh. (1998). Effects of harvesting method and growth stage on the flocculation of thegreen alga botryococcus braunii. Letters in Applied Microbiology. (27), 14.
McGarry, M.G., C. Tongkasa. (1971). Water reclamation and algae harvesting. Water Pollution Control Federation Research Journal. 43(5), 824.
Molina Grima E., E-H Belarbi, F.G. Acién Fernández, A. Robles Medina, Y. Chisti. (2003). Recovery of microalgal biomass
and metabolites: process options and economics. Journal of Biotechnology Advances. (20), 491–515.
Mollah, M.P., et al. (2004). Fundamentals, present and future perspectives ofelectrocoagulation. Journal of Hazardous Materials. B114, 199.
Oswald, W.J. (1991). Introduction to advanced integrated wastewater ponding systems. Water, Science and Technology. 24(5), 1-7.
Pan, J.R., C.P. Huang, Y.C. Chuang, C.C. Wu. (2001). Dewatering characteristics of algae-containing alumsludge. Colloids and Surfaces A-Physicochemical and Engineering Aspects. 150(1-3), 185.
Peterson, A. A., F. Vogel, R. P. Lachance, M. Froling, M. J. Antal, and J. W. Tester. (2008). Thermochemical biofuel production inhydrothermal media: A review of sub- and supercritical water technologies. Energy & Environmental Science. 1, 32-65.
Phoochinda, W., D.A. White. (2003). Removal of algae using froth flotation. Environmental Technology. 24(1), 87.
Poelman, E., N. Pauw. (1997). Potential of electrolytic flocculation for recovery of microalgae. Resources, Conservation, and Recycling. (19), 1.
Pringle, J. D., C. K. Tseng. (1989). Overview of a workshop on production and utilization of commercial
seaweeds - Qingdao, China, 1987. The Journal of Applied Phycology. (1), 83-89.
Roesijadi, G., A. E. Copping, M. H. Huesemann, J. Forster, and J. R. Benemann. (2008). Techno-economic feasibility analysis of offshore
seaweed farming for bioenergy and biobased products. Battelle Pacific Northwest Division Report Number PNWD-3931.
Saidam, M.Y., D. Butler. (1996). Algae removal by horizontal flow rock filters. Advances in Slow Sand andAlternative Biological Filtration. 327.
Sim, T.S., A. Goh, E.W. Becker. (1988). Comparison of centrifugation, dissolved air flotation and drum
filtration techniques for harvesting sewage-grown algae. Biomass. 16(1), 51.
Sukenik, A., G. Shelaf. (1984). Algal autoflocculation-verification and proposed mechanism. Biotechnology and Bioengineering. (26), 142.
Ugarte, R., G. Sharp. (2001). A new approach to seaweed management in Eastern Canada:
The case of ascophyllum nodosum. Cah. Biol. Mar 42, 63-70.

4. Downstream Processing: Harvesting and Dewatering41

5. Extraction of Products from Algae
While relatively limited volumes of bioproducts are
currently produced from algal feedstocks, algal biomass
suffers from a lack of well-defined and demonstrated
industrial-scale methods for extracting and separating ofoils and lipids required for enabling biofuel production.
Existing extraction techniques are mainly suitable foranalytical- and laboratory-scale procedures, or for therecovery/removal of high-value products. To produce
algal biofuels as competitive bulk commodity, extraction
techniques employed must be efficient and effective.

are attempting to bypass this step—the dynamics ofextraction in aqueous phase systems serves as a starting
place for industrial-scale extraction operations.

Extraction depends on identifying the particular biologicalcomponent for extraction, which is dependant on thealgal species and growth status. Additionally, different
harvest process operations (discussed in the Chapter 4)
operations could affect extraction processes, as well as thefuel conversion process. While many terrestrial feedstocks
can be removed from their environment at total solids>40%, microalgae and cyanobacteria may be cultivatedas single cells suspended in water at concentrations below
1% solids. While macroalgae are more like traditional
feedstocks, different logistical challenges arise fromtheir offshore production and harvesting. Many effective
extraction techniques require concentrated substrates, thus
a high degree of concentration may be necessary before
some types of extraction can begin. For this reason,some algae-to-biofuels processes attempt to bypass theextraction step by either converting whole algal biomass orby inducing the secretion of the desired product directly.

Mechanical Disruption (i.e., Cell Rupture)

A shortfall of relevant information on efficient extractionof lipids and oils at larger-scale is limiting the algal-based
biofuel development. Laboratory-scale comparisons of
extraction of lipids from microalgae (Lee et al., 2010) andmacroalgae (Aresta, Dibenedetto, and Barberio, 2005)
have been carried out, but these techniques often rely
on freeze dried, pulverized biomass. While considerable
knowledge exists for the separation of plant biomass
lipid extracts and preparation for conversion to biodiesel(Zhang et al., 2003), little is known about the scaleup separation challenges for extracted algal lipids.

5.1 Current Practices for
Lipid Extraction
The basis for lipid extraction from algal biomass islargely in the realm of laboratory-scale processes thatserve analytical rather than biofuel production goals.
Assuming a system that requires extraction of oils andlipids from harvested biomass—as noted, some systems
42

5. Extraction of Products from Algae

Lipid extraction includes the following approaches:
solvent-based extraction relying on microwaves and orsonication for cell disruption; using solvents to “milk” algal
cells without disrupting cellular functions; and extraction
bypass schemes that attempt to engineer algal systems
that secrete products directly into the growth medium.

Algal biofuel schemes that rely on the accumulation of
intra-cellular lipids are the focus of this discussion. To
be successful, any extracting solvent must be able to (1)penetrate through the matrix enclosing the lipid material,(2) physically contact the lipid material, and (3) solvate thelipid. As such the development of any extraction process
must also account for the fact that the tissue structure
and cell walls may present formidable barriers to solvent
access. This generally requires that the native structureof the biomass must be disrupted prior to extraction.
Effective mechanical disruption can help offset the need
to use elevated temperature and pressure processes thatforce the solvent into contact with desired biopolymers.
Different methods can be used to disrupt the cell membraneprior to the application of the extraction solvents.
Mechanical disruption can include cell homogenizers,
bead mills (or bead-beating), ultrasounds, and autoclaving(Mata et al., 2010). Non-mechanical methods include
process such as freezing, application of organic solvents,
osmotic shock, and acid, base, and enzyme reactions (Mataet al., 2010). The use of microwaves to disrupt cells andincrease efficiencies of vegetable lipid and oil extraction
is a promising development (Cravotto et al., 2008; Virotet al., 2008), though applications outside of analyticallabs are unclear. For waste treatment, pretreatment of
sewage sludge with “focused pulse” sonication has beenshown to improve methane gas production and biosolids
reduction in sludge digestion (Rittman et al., 2008).
Recent work on extraction of lipids from three different
types of oleaginous microalgae compared bead beating,sonication, autoclaving, osmotic shock, and microwaves
and suggested that microwave disruption prior to solvent
extraction is the most efficient method (Lee et al., 2010).

Organic Co-solvent Mixtures
The concept of like dissolves like is the basis behind theearliest and well-known co-solvent extraction procedure(Bligh and Dyer, 1959). After the extraction reaction iscomplete, water (which is not miscible with chloroform) is
added to the co-solvent mixture until a two-phase systemdevelops in which water and chloroform separate into
two immiscible layers. The lipids mainly separate to thechloroform layer and can then be recovered for analysis.
Chloroform will extract more than just the saphonifiable
lipids (i.e., the unsaponifiable lipids such as pigments,
lipoproteins, and other lipid and non-lipid contaminants)(Fajardo et al., 2007). Consequently, other combinationsof co-solvents have been proposed for the extraction oflipids: hexane/isopropanol for tissue (Hara & Radin,1978); dimethyl sulfoxide/petroleum ether for yeast(Park et al., 2007); hexane/ethanol for microalgae(Cartens et al., 1996); and hexane/isopropanol for
microalgae (Nagle & Lemke, 1990). The hexane system
has been promoted because hexane and alcohol willreadily separate into two separate phases when water isadded, thereby improving downstream separations.
Similarly, less volatile and toxic alcohols (e.g., ethanol andisopropanol) have been suggested in place of methanol.
One example is the hexane/ethanol extraction co-solvent
system (Grima et al., 1994). In other cases, single alcohol(e.g., 1-butanol and ethanol) solvents have been tried(Nagle & Lemke, 1990). In these applications, the alcohol
is first added as the extracting solvent. Separation is thenachieved by adding both hexane and water in proportions
that create a two phase system (hexane and an aqueoushydroalcoholic) that partition the extracted lipids into
the nonpolar hexane (Fajardo et al., 2007). In general,applications using pure alcohol (ethanol and 1-butanol)
performed similarly, if not slightly better than alcohol/
hexane mixtures, but never more than 90% of the Bligh andDyer co-solvent method. More, pure alcohol solutions ofgreater carbon length (such as butanol) have not comparedwell against the hexane/ethanol co-solvent system.
These results suggest that the two most important criteria
when selecting a co-solvent system to extract lipids are:(1) the ability of a more polar co-solvent to disrupt the cell
membrane and thus make it sufficiently porous and(2) the ability of a second less polar co-solvent to better
match the polarity of the lipids being extracted.
To avoid the use of elevated temperature and pressure topush the solvent into contact with the analyte (at the costof a very high input of energy), disruption of the cell
membrane may be necessary.

Application of Organic Two-Solvent Systems for
Lipid Extraction from Microalgae:
Iverson et al. (2001) found that the Bligh and Dyer methodgrossly underestimated the lipid content in samples ofmarine tissue that contained more than 2% lipids but
worked well for samples that contained less than 2%
lipids. The sequence of solvent addition can also affectextraction (Lewis et al., 2000). Starting from freeze driedbiomass, it has been demonstrated that the extraction oflipids was significantly more efficient when solvents wereadded in order of increasing polarity (i.e. chloroform,
methanol, and then water) (Lewis, 2000). They explained
their results in terms of initial contact of the biomass with
nonpolar solvents weakening the association between thelipids and cell structure, prior to their dissolution in themonophasic system of water, chloroform, and methanol.
These important results have a key impact on liquid phaseextraction systems applied to “wet” biomass because theysuggest that the water will form a solvent shell around thelipids, making it more difficult for less polar solvents suchas chloroform to contact, solubilize, and extract the lipids.
It is also noteworthy that the extraction efficiency was not
improved (when water was added first), despite the added
agitation in the form of sonication or additional methanol.
Direct Transesterification of Lipids into
Fatty Acid Methyl Esters (FAMES)
To increase analytical efficiency, Lepage and Roy (1984)
proposed the direct transesterification of human milk andadipose tissue without prior extraction or purification forimproved recovery of fatty acids. In general, this approachsuggested that a one-step reaction that added the alcohol(e.g., methanol) and acid catalyst (e.g., acetyl chloride)
directly to the biomass sample and followed with heating
at 100˚C for an hour under sealed cap would increase
fatty acid concentrations measured (as compared toBligh and Dyer co-solvent system), give relatively highrecoveries of volatile medium chain triglycerides, andeliminate the need to use antioxidants to protect unsaturated
lipids. This method was applied to dried microalgal
biomass in a modified approach to include hexane in
the reaction phase in order to avoid a final purification
step (Rodriguez-Ruiz et al., 1998). It was found that theentire reaction could be shortened to 10 minutes if the
mixture was incubated at 100˚C under a sealed cap.
Continuing efforts along this path, it was found that when
applying direct transesterification using an acid catalyst(i.e., acetyl chloride), the efficiency of the reaction
increased when a second “less polar” solvent such as
diethyl ether or toluene was mixed with the methanol tomodify the polarity of the reaction medium (Carvalho andMalcata, 2005). In general, these findings suggest that
5. Extraction of Products from Algae

43

the effectiveness of the second co-solvent (i.e., reaction
medium) depends upon its ability to solubilize the target
lipids coupled with its miscibility with methanol.
All the preceding co-solvent systems, however,remain largely bench-scale methods that are difficult
to scale up to industrial processes due to the actual
solvent toxicity and the low carrying capacity of thesolvents (i.e., it is only efficient on biomass samples
containing less than 2% w/w lipids). Accordingly,
single solvent systems at elevated temperature andpressure have gained favor for two principle reasons:• the elevated temperature and pressure increase therate of mass transfer and degree of solvent accessto all pores within the biomass matrix and;• the elevated pressures can reduce the dielectric
constant of an otherwise immiscible solvent (andby analogy, the polarity) to values that match thepolarity of the lipids (Herrero et al., 2006).
Consequently, the issue of solvent access to the material
being extracted is as important as the miscibility of theanalyte in the solvent. This observation is a key driving
force behind the consideration of solvent extraction
systems at elevated temperature and pressure.

Accelerated Solvent Extraction
Accelerated solvent extraction (ASE) was first proposedin the mid 1990s (Richter et al., 1996), using thetechnique on 1 - 30 g samples of dried biomass. ASE
uses organic solvents at high pressure and temperatures
above their boiling point. In general, a solid sample
is enclosed in a sample cartridge that is filled with an
extraction fluid and used to statically extract the sample
under elevated temperature (50 - 200˚C) and pressure(500 - 3000 psi) conditions for short time periods(5 - 10 min). Compressed gas is used to purge thesample extract from the cell into a collection vessel.
ASE is applicable to solid and semi-solid samples thatcan be retained in the cell during the extraction phase(using a solvent front pumped through the sample at theappropriate temperature and pressure). It has been proposed
for the extraction of liquid extracts (Richter et al., 1996;
Denery et al., 2004) and lipids from microalgae (Schäfer,1998). In addition to improving yields and reducing
extraction time, ASE can also be applied to remove coextractable material from various processes, to selectively
extract polar compounds from lipid-rich samples, andto fractionate lipids from biological samples (ref).

44

5. Extraction of Products from Algae

ASE is more efficient if extracting solvent, sample-solvent
ratio, extraction temperature, and time have been optimized(Denery et al., 2004). Denery and coworkers optimized
the extraction of carotenoids from Dunaliella salina
and showed that higher or equal extraction efficiencies(compared to traditional solvent technology) could beachieved with the use of less solvent and shorter extraction
times. The performance of ASE extraction was comparedto that of traditional Folch method for microalgae grownon dairy manure effluent (Mulbry et al., 2009). The
ASE , depending on the solvent, extracted 85 - 95%of the fatty acid content in the harvested microalgae
compared to 44 - 55% of the fatty acids extracted by
the Folch method in the first solvent extraction cycle.
What remains unclear is the effectiveness of suchan approach at large scale in terms of how to handle
large amounts of biomass, separate out desirable
lipids, and optimize the energy cost. The latter is also
noteworthy in the context that ASE by definition uses
non-aqueous solvents and therefore, must use driedbiomass, a step that also requires energy input.

Selective Extraction
Hejazi et al. (2002) proposed the two-phase system of
aqueous and organic phases for the selective extraction of
carotenoids from the microalgae Dunaliella salina. Theirobservations were that solvents with lower hydrophobicity
reach critical concentrations more easily and in theprocess, break down the cell membrane. By using solventsof higher hydrophobicity, the effect of the solvent on
the membrane decreased and the extraction efficiency
for both chlorophyll and β-carotene decreased as well.
By applying a measurement of solvent hydrophobicity
based on the partition coefficient of the solvent in a twophase system of octanol and water, screening viability
and activity tests of Dunaliella salina in the presence ofdifferent organic phases indicated that cells remained
viable and active in the presence of organic solvents witha log P (octanol ) > 6 and that β-carotene can be extracted
more easily than chlorophyll by biocompatible solvents.
This work has served as the basis for the development ofa technology that proposes to use solvents such as decaneand dodecane in the presence of live microalgal cells,
concentrated for the extraction of triglycerides without
loss of cell viability and extraction of membrane-boundfree fatty acids. Conceptually, the cells can be returnedto their original bioreactor for continued growth andproduction of triglycerides for biofuels production. For
example, some have proposed a modified technique to“milk” oils or neutral lipids from algae using biocompatible
solvents and applied sonication. If this process can beapplied to microalgae slurries with suspended solid
concentrations as low as 1 wt%, this method may provide
a unique avenue for the selective extraction of lipids
suitable for biofuels (e.g., triglycerides) that excludes
the extraction of lipids that cannot be transesterified,
as well as pigments (such as chlorophyll), which canbe difficult to separate from the desired lipids.

Subcritical Water Extraction
Subcritical water extraction (also known as hydrothermalliquefaction) is based on the use of water, at temperatures
just below the critical temperature, and pressure highenough to keep the liquid state (Soto and Luque de Castro,
2001) . The technique, originally termed “pressurized hot
water extraction,” was initially applied to whole biomass
hemicellulose as a pretreatment prior to its use as afermentation substrate (Mok et. al., 1992). More recently,
however, it has been applied for the selective extractionof essential oils from plant matter (Eikani et al., 2007),
functional ingredients from microalgae (Herrero et al.,2006), and saponins from oil-seeds (Güçlü-Üstündağ etal., 2007). The basic premise to subcritical water extractionis that water, under these conditions, becomes less polarand organic compounds are more soluble than at room
temperature. There is also the added benefit of solvent
access into the biomass matrix that occurs at the higher
temperatures as discussed above. In addition, as the water iscooled back down to room temperature, products miscibleat the high temperature and pressure become immiscible
at lower temperatures and can be easily separated. Someof the more important advantages described for subcriticalwater extraction include shorter extract times, higher
quality of extracts, lower costs of the extracting agent,and environmental compatibility (Herrero et al., 2006).
With respect to microalgae, however, whether grownphototrophically or heterotrophically, one of the more
attractive aspects is the use of water as the solvent,thereby eliminating the need for the dewatering step. A
major constraint, however, as with accelerated solvent
extraction, is the difficulty with designing a system atlarge scale and the high-energy load required to heat thesystem up to subcritical temperatures. Large-scale design
will also require a significant cooling system to cool
the product down to room temperature to avoid productdegradation, creating additional energy use challenges.

Supercritical Fluid Extraction
Supercritical fluid extraction utilizes the enhanced solvating
power of fluids above their critical point (Luque deCastro et al., 1999). It can be processed using solid andliquid feeds (Reverchon et al., 2006). Supercritical fluid

extraction techniques have been used in the commercial
extraction of substances from solid substrates, e.g.
caffeine from coffee beans, for more than two decades(Brunner, 2005). The majority of applications have used
CO2 because of its preferred critical properties (i.e.,moderate critical temperature of 31.1˚C and pressure of
73.9 bar), low toxicity, and chemical inertness (Luque deCastro et al., 1999), but other fluids used have included
ethane, water, methanol, ethane, nitrous oxide, sulfur
hexafluoride, as well as n-butane and pentane (Herrero etal., 2006). The temperature and pressure above the criticalpoint can be adjusted as can the time of the extraction.
Supercritical extraction is often employed in batch mode,
but the process can also be operated continuously (Brunner,2005). One of the more attractive points to supercriticalfluid extraction is that after the extraction reaction has
been completed and the extracted material dissolved into
the supercritical fluid, the solvent and product can beeasily separated downstream once the temperature andpressure are lowered to atmospheric conditions. In thiscase, the fluid returns to its original gaseous state while
the extracted product remains as a liquid or solid.
Supercritical fluid extraction has been applied for the
extraction of essential oils from plants (Reverchon etal., 2006), as well as functional ingredients and lipids
from microalgae (Mendes et al., 1994; Metzger andLargeau, 2005). Lipids have been selectively extracted
from macroalgae at temperatures of 40 - 50˚C andpressures of 241 - 379 bar (Chueng, 1999). However,
economical production of biofuels from oleaginous
microalgae via supercritical processing is challenged
by the same issues of energy-intensive processing andscaling up the process that is developed mainly for
analytical usage. Use of methanol as the solvating fluid
has the effect of converting lipids, via transesterification,
to biodiesel (see Chapter 6 for more detail).

Heterotrophic Production
Other methods for extraction and fractionation include
the production of oils using heterotrophic algae. In this
scenario, non-photosynthetic algae are grown usingsugars as energy source and using standard industrial
fermentation equipment (Barclay et al., 1994). Some
private companies have engineered algae that secrete oil
into the fermentation media that can be recovered andlater refined into a biofuel; this approach significantly
reduces the capital and operating cost for an extraction
process. The potential benefits of this approach are theuse of standard fermentation systems, higher productivity
compared to photosynthetic systems, ease of scale-up,
avoidance of expensive extraction scheme(s), the ability to
5. Extraction of Products from Algae

45

maintain the integrity of the fermentation catalyst and useof sugar-based feedstocks. However, significant downsides
to this approach include many of the same feedstock
logistics challenges faced by the nascent lignocellulosic
industry. Chief amongst is the logistical challenge of
securing a sustainable biomass feedstock to supply to feedlarge-scale heterotrophic “algal-refinery” operations.

5.2 Challenges
Presence of Water Associated with the Biomass
The extraction process is affected by the choice of
upstream and downstream unit operations and viceversa. The presence of water can cause problems at
both ends at larger scales. When present in the bulk
solution, water can either promote the formation ofemulsions in the presence of ruptured cells or participate
in side reactions. At the cellular level, intracellularwater can prove to be a barrier between the solvent
and the solute. In this context, the issue of solvent
access to the material being extracted is as importantas the miscibility of the analyte in the solvent. This is aprincipal motivation behind the application of extraction
techniques at elevated temperatures and pressures.

contact between the solvent and the solute. Increased
pressure facilitates enhancing the transport of the solvent
to the analytes that have been trapped in pores. The
pressure also helps to force the solvent into matricesthat would normally not be contacted by solvents underatmospheric conditions. Mechanical disruption can
reduce the pressure and temperature requirements.
Separation of Desired Extracts from Solvent Stream
Extraction processes can yield undesirable components,
such as chlorophyll and non- transesterifiable lipids.
Very little information is available on this criticalstep that is necessary before converting the algal
biocrude into finished fuels and products.
Energy Consumption and Water Recycle
For sustainable biofuels production, the following
benchmark can be considered: the extraction process
per day should consume no more than 10% of the totalenergy load, as Btu, produced per day. As discussed in
Section 4.3, a preliminary look at the energy balancedoes not suggest that this is an insurmountable barrier,but it does serve to highlight the need for innovationto achieve sustainable commercial-scale systems.

Increasing the temperature helps to disrupt the solutematrix interactions and to reduce the viscosity andsurface tension of the water, thereby improving theReferences
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utilizing algae and algae-like microorganisms. Journal of Applied Phycology, 6(2), 123-129.
Brunner, G., 2005. Supercritical fluids: technology and application to food processing. Journal of Food Engineering, 67(1-2), 21-33.
Cartens, M. et al., 1996. Eicosapentaenoic acid from the marine microalga Phaeodactylum
tricornutum. Journal of the American Oil Chemists' Society, 73(8), 1025–1031.
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analysis of marine lipids: Insight studies. J. Agric. Food Chem, 53(13), 5049–5059.
Cravotto, G. et al., 2008. Improved extraction of vegetable oils under high-intensity ultrasoundand/or microwaves. Ultrasonics Sonochemistry, 15(5), 898-902.
Denery, J.R. et al., 2004. Pressurized fluid extraction of carotenoids from Haematococcus pluvialis and Dunaliellasalina and kavalactones from Piper methysticum. Analytica Chimica Acta, 501(2), 175–181.
Eikani, M.H., Golmohammad, F. & Rowshanzamir, S., 2007. Subcritical water extraction of essential oils
from coriander seeds (Coriandrum sativum L.). Journal of Food Engineering, 80(2), 735–740.
Fajardo, A.R. et al., 2007. Lipid extraction from the microalga Phaeodactylum tricornutum. Lipid-Fett, 109(2), 120–126.
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biomass. Journal of the American Oil Chemists' Society, 71(9), 955–959.
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Hara, A. & Radin, N.S., 1978. Lipid extraction of tissues with a low-toxicity solvent. Analytical Biochemistry, 90(1), 420–426.
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Herrero, M., Cifuentes, A. & Ibanez, E., 2006. Sub-and supercritical fluid extraction of functional ingredients from different
natural sources: Plants, food-by-products, algae and microalgae A review. Food chemistry, 98(1), 136–148.
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Luque de Castro, M.D., Jimenez-Carmona, M.M. & Fernandez-Perez, V., 1999. Towards more rational techniques
for the isolation of valuable essential oils from plants. Trends in Analytical Chemistry, 18(11), 708–716.
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Mendes, R. et al., 1994. Supercritical carbon dioxide extraction of hydrocarbons from themicroalgaBotryococcus braunii. Journal of Applied Phycology, 6(3), 289-293.
Metzger, P. & Largeau, C., 2005. Botryococcus braunii: a rich source for hydrocarbons and related
ether lipids. Applied Microbiology and Biotechnology, 66(5), 486-496.
Mulbry, W. et al., 2009. Optimization of an Oil Extraction Process for Algae from the Treatment ofManure Effluent. Journal of the American Oil Chemists' Society, 86(9), 909–915.
Nagle, N. & Lemke, P., 1990. Production of methyl ester fuel from microalgae. Applied Biochemistry and Biotechnology, 24(1), 355–361.
Park, P.K., Kim, E.Y. & Chu, K.H., 2007. Chemical disruption of yeast cells for the isolation of
carotenoid pigments. Separation and Purification Technology, 53(2), 148–152.
Reverchon, E., Iol & Marco, A.D., 2006. Supercritical fluid extraction and fractionation ofnatural matter. The Journal of Supercritical Fluids, 38(2), 146-166.
Richter, B.E. et al., 1996. Accelerated solvent extraction: a technique for sample preparation. Anal. Chem, 68(6), 1033–1039.
Rittmann, B.E., Krajmalnik-Brown, R. & Halden, R.U., 2008. Pre-genomic, genomic and postgenomic study of microbial communities involved in bioenergy.
Rodriıguez-Ruiz, J. et al., 1998. Rapid simultaneous lipid extraction and transesterification
for fatty acid analyses. Biotechnology techniques, 12(9), 689–691.
Schäfer, K., 1998. Accelerated solvent extraction of lipids for determining the fatty acidcomposition of biological material. Analytica Chimica Acta, 358(1), 69–77.
Soto Ayala, R. & Luque de Castro, M.D., 2001. Continuous subcritical water extraction as a useful
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47

6. Algal Biofuel Conversion Technologies
Potentially viable fuels that can be produced from algae
range from gaseous compounds like hydrogen and methane,to alcohols and conventional liquid hydrocarbons, topyrolysis oil and coke. Attractive targets for this effort,
however, are the liquid transportation fuels of gasoline,
diesel, and jet fuel. These fuel classes were selected as thebest-value targets because 1) they are the primary productsthat are currently created from imported crude oil for thebulk of the transportation sector, 2) they have the potential
to be more compatible than other biomass-based fuels withthe existing fuel-distribution infrastructure in the U.S., and
3) adequate specifications for these fuels already exist.
The primary objective of this chapter is to summarize anumber of potentially viable strategies for converting algal
biomass into replacements for petroleum gasoline, diesel,and jet fuel. When a fuel meets all customer requirements,
it is referred to as “fit for purpose.” While a successful
fuel-conversion strategy will address the full range ofdesired fit-for-purpose properties (e.g., distillation range,
ignition characteristics, energy density, etc.), these desired
fuel characteristics are driven primarily by customer
requirements and are discussed later in Chapter 8. This
chapter focuses on fuel conversion strategies from a varietyof perspectives to establish the current state-of-the-art,
as well as identify critical challenges and roadblocks.
Several emerged the Algal Roadmap Workshop in
relation to conversion of algal feedstocks to fuels. These
are noted here to help establish a reasonable framework
for the most promising concepts for algal biofuels.
• First, the feedstock, conversion process, andfinal fuel specifications are highly interdependentand must be considered together if an optimal
process is to be identified. As a result, accurate
and detailed feedstock characterization (including
both composition and variability) is essential,
since this is an upstream boundary condition for
the entire downstream fuel-conversion process.
• Second, life cycle analysis of energy and carbon will
be a key tool in selecting the preferred fuel conversion
technologies from those discussed in this chapter.
• Third, the greatest challenge in algal fuel conversion is
not likely to be how to convert lipids or carbohydrates
to fuels most efficiently, but rather how best to use
the algal remnants after the lipids or other desirable
fuel precursors have been extracted. All of thepetroleum feedstock that enters a conventional
petroleum refinery must leave as marketable
48

6. Algal Biofuel Conversion Technologies

products, and this conservation law must also holdtrue for the algae biorefineries of the future if they
are to achieve significant market penetration.
A large number of potential pathways exist for theconversion from algal biomass to fuels. These pathways can
be classified into the following three general categories:
1) Those that focus on the direct algal productionof recoverable fuel molecules (e.g., ethanol,hydrogen, methane, and alkanes) fromalgae without the need for extraction;2) Those that process whole algal biomass
to yield fuel molecules; and
3) Those that process algal extracts (e.g., lipids,
carbohydrates) to yield fuel molecules.
These technologies are primarily based on similar
methods developed for the conversion of terrestrial
plant-based oils and products into biofuels, although thecompositional complexities of the output streams fromalgae must be dealt with before these can be applied
effectively. Pros and cons of these pathways within eachof these categories are discussed below, and a summaryof each fuel-conversion technology is given. Inputs,
complexity, cost, and yields are provided (where known),
and key barriers and RD&D opportunities are listed.

6.1 Direct Production of
Biofuels from Algae
The direct production of biofuel through heterotrophic
fermentation and growth from algal biomass has certain
advantages in terms of process cost because it caneliminate several process steps (e.g., oil extraction)and their associated costs in the overall fuel production
process. Heterotrophic growth also allows for maintaining
highly controlled conditions, which first could be oriented
toward biomass production and then oil production. Sucha system can generate extremely high biomass (hundredsof grams per liter) and a high percentage of that biomass
as lipid (well over 50%). The system is readily scaled up
and there is an enormous potential to use various fixed
carbon feedstocks (which would bring down the cost of
production). These approaches are quite different fromthe usual algal biofuel processes that use algae to produce
biological oils which is subsequently extracted and used asa feedstock for liquid fuel production, typically biodiesel.
There are several biofuels that can be produced directlyfrom algae, including alcohols, alkanes, and hydrogen.

Alcohols
Algae, such as Chlorella vulgaris and Chlamydomonas
perigranulata, are capable of producing ethanol and otheralcohols through heterotrophic fermentation of starch(Hon-Nami, 2006; Hirayama et al., 1998). This can beaccomplished through the production and storage ofstarch via photosynthesis within the algae, or by feeding
sugar to the algae directly, and subsequent anaerobic
fermentation of these carbon sources to produce ethanol
under dark conditions. If these alcohols can be extracted
directly from the algal culture media, the process
may be drastically less capital- and energy-intensive
than competitive algal biofuel processes. The process
would essentially eliminate the need to separate thebiomass from water and extract and process the oils.
This process typically consists of closed photobioreactors
utilizing sea-water with metabolically enhanced
cyanobacteria that produce ethanol or other alcohols while
being resistant to high temperature, high salinity, andhigh ethanol levels—previous barriers to commercialscale volumes (Hirano et al., 1997). There have beenreports of preliminary engineered systems, consisting of
tubular photobioreactors (Hirano et al., 1997). One key
aspect of the system is that a source of cheap carbon, suchas a power plant, is typically used to supply CO2 to thebioreactors to accelerate the algae growth. An exampleof this process technology links sugar production toalgal photosynthesis. There are claims that this process
may consume more than 90% of the system’s CO2
through photosynthesis, wherein a portion of the carbon
in these sugars is converted into ethanol. The ethanol
is secreted into the culture media and is collected in
the headspace of the reactor, purified, and stored.
This technology is estimated to yield 4,000 - 6,000 gallons
per acre per year, with potential increases up to 10,000
gallons per acre per year within the next 3 to 4 years
with significant R&D. It is theoretically estimated that
one ton of CO2 is converted into approximately 60 - 70
gallons of ethanol with this technology. With such yields,
the price of captured CO2 becomes significant, and may
require a price less than or equal to $10 per ton to remain
cost-competitive. Further breakthroughs that enable more
efficient production systems and the development of newprocess technologies may be critical in terms of long-termcommercial viability. Scaling of these systems to largescale commercial biorefineries will also require significant
advances in process engineering and systems engineering.
Metabolic pathway engineering within these algae, enabled
by metabolic flux analysis and modern genomics tools, may
further help in producing a commercially viable organism.

In addition to ethanol, it is possible to use algae to produce
other alcohols, such as methanol and butanol, using asimilar process technology, although the recovery ofheavier alcohols may prove problematic and will needfurther R&D. The larger alcohols have energy densities
closer to that of gasoline but are not typically produced
at the yields that are necessary for commercial viability.

Alkanes
In addition to alcohols, alkanes may be produced directly
by heterotrophic metabolic pathways using algae. Rather
than growing algae in ponds or enclosed in plastic
tubes that utilize sunlight and photosynthesis, algae canbe grown inside closed reactors without sunlight. The
algae are fed sugars, the cheap availability of which
is a key consideration for cost-effective production of
biofuels; these sugars are themselves available fromrenewable feedstocks such as lignocellulosic biomass,in a pressure and heat-controlled environment. This
process can use different strains of algae to produce
different types of alkanes; some algae produce a mix ofhydrocarbons similar to light crude petroleum. Thesealkanes can theoretically be secreted and recovered
directly without the need for dewatering and extraction,
but more often are associated with the algae and thus must
be recovered through dewatering and extraction. Withfurther processing, a wide variety of fuels can be made.
The process of growing the algae heterotrophically may
present some advantages over typical photoautotrophicbased technologies. First, keeping the algae “in the dark”
causes them to produce more alkanes than they do in thepresence of sunlight. While their photosynthetic processes
are suppressed, other metabolic processes that convert
sugar into alkanes can become active. Second, some haveshown the growth rate of the algae to be much higher
than traditional methods (Xu et al., 2006). This is possible
because instead of getting energy for growth from sunlight,
the algae get concentrated energy from the sugars fed into
the process. These higher cell concentrations reduce theamount of infrastructure needed to grow the algae, andenable more efficient dewatering if is actually required.
Using algae to convert cellulosic materials, such as
switchgrass or wood chips, to oil may have an advantage
over many other microorganisms under development
for advanced biofuel production. When lignocellulosic
biomass is pretreated to allow for enzymatic hydrolysis
for production of sugars, many toxic byproducts are
released including acetate, furans, and lignin monomers.
In most other processes, these toxic compounds can
add process costs by requiring additional conditioning

6. Algal Biofuel Conversion Technologies

49

steps or the concentration of biomass hydrolysate
in the conversion step. Algae may prove to be moreresistant to these compounds and sugar conversion.

HydrogenThe production of hydrogen derived from algae hasreceived significant attention over several decades.
Biological production of hydrogen (i.e., biohydrogen)technologies provide a wide range of approaches togenerate hydrogen, including direct biophotolysis,
indirect biophotolysis, photo-fermentation,and dark-fermentation (see Chapter 2).
There are several challenges that remain before
biological hydrogen production can be considered a viable
technology. These include the restriction of photosynthetichydrogen production by accumulation of a proton
gradient, competitive inhibition of photosynthetichydrogen production by CO2, requirement forbicarbonate binding at photosystem II (PSII) for efficientphotosynthetic activity, and competitive drainage ofelectrons by oxygen in algal hydrogen production.
The future of biological hydrogen production depends
not only on research advances, i.e., improvement inefficiency through genetically engineered algae and/or thedevelopment of advanced photobioreactors, but also
on economic considerations, social acceptance, and thedevelopment of a robust hydrogen infrastructure
throughout the country.

6.2 Processing of Whole Algae
In addition to the direct production of biofuels fromalgae, the whole algae can be processed into fuels
instead of first extracting oils and post-processing. Thesemethods benefit from reduced costs associated withthe extraction process, and the added benefit of being
amenable to processing a diverse range of algae, though
at least some level of dewatering is still required.
Macroalgae has specifically received some attention as a
gasification feedstock and initial work shows that whilesome key differences exist as compared to terrestrial
crops, certain species are suitable for gasification (Ross etal., 2008). Polysaccharides, such as mannitol, laminarin,
and fucoidin, represent the main macroalgae biochemical
feedstocks for conversion to liquid fuels (McHugh, 2003).
Lipid content of a variety of macroalgal species is typicallyless than 5% of total dry weight (McDermid & Stuercke,
2003), too low for conversion to biodiesel, althoughconcentrations approaching 20% are reported in somespecies (Chu et al., 2003; McDermid & Stuercke, 2003).
50

6. Algal Biofuel Conversion Technologies

There are four major categories of conversion
technologies that are capable of processing wholealgae: pyrolysis, gasification, anaerobic digestion,and supercritical processing (Exhibit 6.1).

Pyrolysis
Pyrolysis is the chemical decomposition of a condensed
substance by heating. It does not involve reactions withoxygen or any other reagents but can frequently takeplace in their presence. The thermochemical treatment of
the algae, or other biomass, can result in a wide range of
products, depending on the reaction parameters. Liquid
product yield tends to favor short residence times, fast
heating rates, and moderate temperatures (Huber et al.,2006). Pyrolysis has one major advantage over otherconversion methods, in that it is extremely fast, withreaction times of the order of seconds to minutes.
Pyrolysis is being investigated for producing fuel frombiomass sources other than algae. Although synthetic diesel
fuel cannot yet be produced directly by pyrolysis of algae, adegradable alternative liquid called bio-oil can be produced.
The bio-oil has an advantage that it can enter directly
into the refinery stream and, with some hydrotreating andhydrocracking, produce a suitable feedstock for generating
standard diesel fuel. Also, higher efficiency can be achievedby the so-called “flash pyrolysis” technology, where finely
ground feedstock is quickly heated to 350 - 500˚C forless than 2 seconds. For flash pyrolysis, typical biomass
feedstocks must be ground into fine particles. This is
one area where algae have a major advantage over otherbiomass sources because it exists fundamentally in small
units and has no fiber tissue to deal with. Several pilot
plants for fast pyrolysis of biomass have been built in thepast years in Germany, Brazil, and the United States, but
bio-oil from pyrolysis is not a commercial product at thecurrent time (Bridgwater, 2004). Even with the increased
interest in converting biomass into liquid transportation
fuels, it appears fast pyrolysis to create bio-oil, especiallyfrom algae, is a relatively new process (Bridgwater, 2007).
There are several reports on the pyrolysis of algae in thescientific literature (Demirbas, 2006; Miao and Wu, 2004).
A significant roadblock in using pyrolysis for algae
conversion is moisture content, and significant dehydrationmust be performed upstream for the process to work
efficiently. It is unclear exactly how much more difficult
it would be to convert algae into a bio-oil comparedto other biomass sources due to uncertainties in theability to dehydrate the feedstock; no comprehensive
and detailed side-by-side comparison was found in
the scientific literature. It appears that pyrolysis will
not be cost-competitive over the short-term unless aninexpensive dewatering or extraction process is also
developed. Additionally, since pyrolysis is already arelatively mature process technology, it is expectedthat only incremental improvements will occur and a
breakthrough in conversion efficiency appears unlikely.
While algal bio-oil may be similar to bio-oil fromother biomass sources, it may have a different rangeof compounds and compositions depending on thetype of algae and upstream processing conditions(Zhang et al., 1994). Another research paper
demonstrated that the bio-oil produced by pyrolysisof algae can be tailored by carefully controlling thealgal growth conditions (Miao and Wu, 2004).
Unfortunately, there are also significant gaps in theinformation available about the specifications forconverting algal bio-oil and the resulting products. The
optimal residence time and temperature to produce different
algal bio-oils from different feedstocks need to be carefully
studied. Work also needs to be performed to understand thedetailed molecular composition of the resulting bio-oils.
Additionally, research is needed on the catalytic conversionof the resulting algal bio-oils. Another area of interest is thedevelopment of stabilizers for the viscosity of the bio-oil
and acid neutralizing agents, so the bio-oil may be moreeasily transported throughout the upgrading process.

Gasification
Gasification of the algal biomass may provide an extremely
flexible way to produce different liquid fuels, primarily
through Fischer-Tropsch Synthesis (FTS) or mixed
alcohol synthesis of the resulting syngas. The synthesisof mixed alcohols using gasification of lignocellulose isrelatively mature (Phillips, 2007; Yung et al., 2009), and it
is reasonable to expect that once water content is adjusted
for, the gasification of algae to these biofuels would becomparatively straightforward. FTS is also a relatively
mature technology where the syngas components (CO, CO2,
H2O, H2, and impurities) are cleaned and upgraded to usable
liquid fuels through a water-gas shift and CO hydrogenation(Okabe et al., 2009; Srinivas et al., 2007; Balat, 2006).
Conversion of bio-syngas has several advantages over othermethods. First and foremost, it is possible to create a wide
variety of fuels with acceptable and known properties.
Additionally, bio-syngas is a versatile feedstock and it
can be used to produce a number of products, making
the process more flexible. Another advantage is thepossibility to integrate an algal feedstock into an existing
thermochemical infrastructure. It may be possible to feedalgae into a coal gasification plant to reduce the capital
investment required, address the issue of availability

Exhibit 6.1 Schematic of the potential conversion
routes for whole algae into biofuels
Algae

Anaerobic
Digestion

Supercritical
FluidsPyrolysis

Gasification

SynGasBiogasLiquid or
Vapor Fuel

FischerTropschCatalytic
UpgradingCatalytic
UpgradingTransportation
Fuels - Liquid or
Gas

LiquidHydrogen Fuels

Higher Alcohol
Synthesis

Hydrogen

MeOH
EtOH, etc.

6. Algal Biofuel Conversion Technologies

51

for dedicated biomass plants, and improve the process
efficiency through economy of scale. Additionally, since
FTS is an exothermic process, it should be possible to usesome of the heat for drying the algae during a harvesting/dewatering process with a regenerative heat exchanger.

for indirect gasification of algae. It would be desirable todetermine the feasibility of using the oxygen generated
by algae for use in the gasifier to reduce or eliminate theneed for a tar reformer. Also, it would be useful to leverageongoing syngas-to-ethanol research using cellulosic.

The key roadblocks to using FTS for algae are thought
to be similar to those for coal (Yang et al., 2005), withthe exception of any upstream process steps that may be
a source of contaminants which will need to be removedprior to reaching the FT catalyst. FTS tends to require
production at a very large scale to make the process
efficient overall. However, the most significant problem
with FTS is the cost of clean-up and tar reforming. Tars
have high molecular weight and can develop during
the gasification process. The tars cause coking of thesynthesis catalyst and any other catalysts used in thesyngas cleanup process and must be removed. The fourbasic mechanisms to deal with tar-related problems are:Liquefaction• Fluidized-bed gasification and catalytic reforming• Fluidized-bed gasification and solvent tar removal• Fluidized-bed gasification andsubsequent thermal tar cracker• Entrained-flow gasification at high temperature
A demonstration plant for gasification of wood chips
with catalytic cracking of the tar is currently being
built in Finland in a joint venture of the TechnicalResearch Centre of Finland (VTT), Neste Oil, andStora Enso. A solvent tar removal demonstration was
installed in a plant in Moissannes, France in 2006.
Tar formation can be minimized or avoided via entrainedflow gasification at high temperatures (Hallgren et al.,1993). While this technology requires sub-millimeter
sized particles, algae may have a unique advantage
in this process. Typically, it is difficult to reach sucha small size with other biomass sources and doing sousually requires pretreatment, but certain species ofalgae may not require pretreatment due to their inherent
small size. Another approach for tar-free syngas wasdemonstrated in a pilot plant in Freiberg, Germany,
built by Choren Industries GmbH. The pilot plant used
two successive reactors. The first reactor was a lowtemperature gasifier that broke down the biomass into
volatiles and solid char. The tar-rich gas was then passed
through an entrained-flow gasifier where it was reactedwith oxygen at high temperature. (Raffelt et al., 2006).
Even though FTS is a mature technology, there are stillseveral areas that should be investigated and require R&D.
First, it is necessary to determine the optimum conditions

52

6. Algal Biofuel Conversion Technologies

Direct hydrothermal liquefaction in subcritical water(defined as water held in a liquid state above 100oC byapplying pressure) is a technology that can be employed toconvert wet algal biomass to a range of liquid fuels (Patil etal., 2008). This technology is a representation of the naturalgeological processes known to be involved in the formationof petroleum-based fossil fuels realized over greatly
shortened time scales. These technologies harness the highactivity of water in subcritical environments that is capableof decomposing the algal biomass into smaller moleculesof higher energy density or more valuable chemicals. The
main product of this liquefaction process is a “bio-crude”
that typically accounts for 45% wt. of the feedstock on a
dry ash free basis and has energy content that is comparable
to diesel and can be upgraded further. There are reports(Goudriaan et al., 2000) that claim the thermal efficiency,
defined as the ratio of heating values of bio-crude products
and feedstock plus external heat input, as high as 75%.
Prior work in direct liquefaction of biomass was very
active, and there are a few reports that used algal biomass
as a feedstock. Liquefaction of Dunaliella tertiolectawith a moisture content of 78.4 wt% produced an oilyield of about 37% (organic basis) at 300˚C and 10 MPa(Minowa et al., 1995). The oil obtained at a reaction
temperature of 340˚C and holding time of 60 min had
a viscosity of 150 - 330 mPas and a calorific value of
36 kJ g−1, comparable to those of fuel oil. In the same
report it was concluded that liquefaction technique wasa net energy producer from the overall process energybalance. A maximum oil yield of 64% using Botryococcus
braunii as a feedstock has also been reported. The
algal biomass was processed by liquefaction at 300˚C,
catalyzed by sodium carbonate (Sawayama et al., 1995).
There have also been comparative studies that report theliquefaction technique was more effective for extractionof microalgal biodiesel than using the supercritical carbon
dioxide (Aresta et al., 2005). Liquefaction of algae isconsidered a promising technological approach but due
to limited information in hydrothermal liquefactionof algae to date, more research in this area is needed
before it can become a commercially viable option.

Supercritical Processing
Supercritical processing is a recent addition to the portfolioof techniques capable of simultaneously extracting
and converting oils into biofuels (Demirbas, 2006).
Supercritical fluid extraction of algal oil is far more efficientthan traditional solvent separation methods, and thistechnique has been demonstrated to be extremely powerfulin the extraction of other components within algae (Mendes,2007). This supercritical transesterification approach canalso be applied for algal oil extracts. Supercritical fluids
are selective, thus providing high purity and productconcentrations. Additionally, there are no organic solvent
residues in the extract or spent biomass (Demirbas, 2009).
Extraction is efficient at modest operating temperatures,for example, at less than 50˚C, ensuring maximum
product stability and quality. Additionally, supercriticalfluids can be used on whole algae without dewatering,
thereby increasing the efficiency of the process.
The supercritical extraction process can be coupled witha transesterification reaction scheme to enable a “onepot” approach to biofuel production (Anitescu et al.,2008). Although it has been only demonstrated for thesimultaneous extraction and transesterification of vegetableoils, it is envisioned as being applicable for the processingof algae. In this process variant, supercritical methanol
or ethanol is employed as both the oil extraction medium
and the catalyst for transesterification (Warabi et al.,2004). In the case of catalyst-free supercritical ethanoltransesterification, it has been demonstrated that thisprocess is capable of tolerating water, with a conversion
yield similar to that of the anhydrous process in theconversion of vegetable oils. While the occurrence ofwater in the reaction medium appears as a factor in process
efficiency, the decomposition of fatty acids is the main
factor that limited the attainable ester content (Vieitez etal., 2008; Vieitez et al. 2009). Similar results have been
observed for supercritical methanol processing of vegetableoils (Hawash et al., 2009). Because decomposition wasa consequence of temperature and pressure conditions
used in this study, further work should be focused on theeffect of milder process conditions, in particular, lower
reaction temperatures. In the case of combined extraction
and transesterification of algae, further study will also
be needed to avoid saponification. It also remains tobe seen whether the processing of whole algae in thisfashion is superior, in terms of yield, cost, and efficiency,
to the transesterification of the algal oil extracts.
The economics of supercritical transesterification process,at least in the case of vegetable oil processing, have beenshown to be very favorable for large-scale deployment.
One economic analysis has been conducted based on asupercritical process to produce biodiesel from vegetableoils in one step using alcohols (Anitescu et al., 2008).
It was found that the processing cost of the proposed
supercritical technology could be near half of that of theactual conventional transesterification methods (i.e., $0.26/
gal vs. $0.51/gal). It is, therefore, theoretically possiblethat if the other upstream algal processing costs could
be mitigated through the addition of a transesterification
conversion process, the overall algal biorefinery
could become cost-competitive with fossil fuels.
The clear immediate priority, however, is to demonstratethat these supercritical process technologies can beapplied in the processing of algae, either whole or its
oil extract, with similar yields and efficiencies at alevel that can be scaled to commercial production. In
particular, it must be demonstrated that this process cantolerate the complex compositions that are found withraw, unprocessed algae and that there is no negative
impact due to the presence of other small metabolites.

Anaerobic Digestion of Whole Algae
The production of biogas from the anaerobic digestionof macroalgae, such as Laminaria hyperbore andLaminaria saccharina, is an interesting mode of gaseous
biofuel production, and one that receives scant attention
in the United States (Hanssen et al., 1987). The use ofthis conversion technology eliminates several of the
key obstacles that are responsible for the current highcosts associated with algal biofuels, including drying,extraction, and fuel conversion, and as such may be acost-effective methodology. Several studies have been
carried out that demonstrate the potential of this approach.
A recent study indicated that biogas production levelsof 180.4 ml/g-d of biogas can be realized using a twostage anaerobic digestion process with different strainsof algae, with a methane concentration of 65% (VergaraFernández et al., 2008). If this approach can be modified
for the use of microalgae, it may be very effective
for situations like integrated wastewater treatment,
where algae are grown under uncontrolled conditions
using strains not optimized for lipid production.

6.3 Conversion of Algal Extracts
The conversion of extracts derived from algal sources is
the typical mode of biofuel production from algae. There isan obvious and critical link between the type of extraction
process used and the product composition, and as such, afundamental and exhaustive understanding of the different
types of inputs to the conversion technologies must be
in place. The most common type of algal extracts underconsideration are lipid-based, e.g., triacylglycerides, which

6. Algal Biofuel Conversion Technologies

53can be converted into biodiesel. This section discusses
chemical, biochemical, and catalytic processes that canbe employed to convert algal extracts. (Exhibit 6.2).

Chemical Transesterification
The transesterification reaction is employed to convert
triacylglycerols extracted from algae to FAMEs (fatty
acid methyl esters), which is simply a process ofdisplacement of an alcohol group from an ester byanother alcohol (Demirbas, 2009). Transesterification
can be performed via catalytic or non-catalytic reaction
systems using different heating systems that are required
to initiate the reaction. This technology is relatively
mature and has been demonstrated to be the “goldstandard” in the conversion of vegetable oils into biodiesel(Hossain et al., 2008). In addition to the classic basecatalyzed methanol approach, it has been shown thattransesterification of algal oil can be achieved with ethanoland sodium ethanolate serving as the catalyst (Zhou &Boocock, 2006). The products of these reactions are
typically separated by adding ether and salt water to thesolution and mixing well. Biodiesel is then separated
from the ether by a vaporizer under a high vacuum.
Another route is found in acid-catalyzed transesterification
reactions (Wahlen et al., 2008). The replacement ofsoluble bases by liquid acid catalysts such as H2SO4, HCl
or H3PO4 is also considered an attractive alternative as
the acidic catalysts are less sensitive to the presence ofwater and free acids, and therefore, mitigate saponificationand emulsification, enhancing the product recovery(Ataya et al., 2007). Though acid catalysts have theseadvantages, they are not currently preferred due to theirlower activity than the conventional transesterification
alkaline catalysts. Higher temperatures and longer reaction
times are, therefore, generally required as a result. In
order to compensate for this, heteropolyacids (HPA),
such as H3PW12O40/Nb2O5, have been shown to lower therequired temperatures and decrease the reaction times(Alsalme et al., 2008; Cao et al., 2008). Recently, it was
shown that HPA-catalyzed transesterification of vegetable
oil achieves higher reaction rates than conventional
mineral acids due to their higher acid strength (L. Xu
et al., 2008). The apparent higher activity of certain
HPAs with respect to polyoxometallates of higher
strength resulted in lower pretreatment temperatures.
One recommended research focus would be to further
develop these homogeneous catalysts to tolerate thecontaminants expected to be present in algal extracts.
In addition to alternative catalysts, there are otherprocessing variants that appear promising. An alternative
heating system that can be used to enhance the kinetics oftransesterification involves the use of microwaves (Refaat& El Sheltawy, 2008). When the transesterification reaction
is carried out in the presence of microwaves, the reactionis accelerated and requires shorter reaction times. As aresult, a drastic reduction in the quantity of co-products
and a short separation time are obtained (Lertsathapornsuk

Exhibit 6.2 Schematic of the various conversion
strategies of algal extracts into biofuels
Algal Oil Extracts

ChemicalTransesterfication

Liquid or
Vapor Fuel

Biodiesel(ME)

Catalytic
UpgradingCatalytic
Upgrading

Diesel54

Enzymatic
Conversion

6. Algal Biofuel Conversion Technologies

DieselCatalytic
Cracking

Gasoline,
Kerosene,
Diesel, Olefin
Aromatics

et al., 2008). These preliminary results indicate thatmicrowave processing may be cost-competitive with themore mature conversion processes currently available.
In addition, catalysts may be used to enhance theimpact of microwave irradiation (Yuan et al., 2008).
In the ultrasonic reactor method, ultrasonic waves cause
the reaction mixture to produce and collapse bubbles
constantly. This cavitation provides simultaneously
the mixing and heating required to carry out thetransesterification process (Armenta et al., 2007). Thus
using an ultrasonic reactor for biodiesel production
drastically reduces the reaction time, reaction temperatures,and energy input (Kalva et al., 2008). Hence the processof transesterification can run inline rather than using thetime-consuming batch process used in traditional basecatalyzed transesterification (Stavarache et al., 2007). It isestimated that industrial-scale ultrasonic devices can allow
for the processing of several thousand barrels per day, butwill require further innovation to reach production levels
sufficient for massive and scalable biofuel production.

Biochemical (Enzymatic) Conversion
Chemical processes give high conversion of triacylglycerols
to their corresponding esters but have drawbacks such as
being energy-intensive, difficulty in removing the glycerol,
and require removal of alkaline catalyst from the productand treatment of alkaline wastewater. Use of biocatalysts(lipases) in transesterification of triacylglycerols forbiodiesel production addresses these problems andoffers an environmentally more attractive option to theconventional processes (Svensson and Adlercreutz,2008). Although enzymatic approaches have become
increasingly attractive, they have not been demonstrated
at large scale mainly due to the relatively high price oflipase and its short operational life caused by the negative
effects of excessive methanol and co-product glycerol.
These factors must be addressed before a commercially
viable biochemical conversion process can be realized.
One critical area that needs to be addressed is the solvent
and temperature tolerance of the enzymes in order toenable efficient biocatalytic processing. The presence ofsolvents is sometimes necessary to enhance the solubilityof the triacylglycerols during the extraction process,and the enzymes used in the downstream conversion
process must be able to function in the presence of thesesolvents to varying degrees to enable cost-effective
biofuel production (Fang et al., 2006). There have beensome recent reports of using a solvent engineering
method to enhance the lipase-catalyzed methanolysis of
triacylglycerols for biodiesel production (Su and Wei,
2008; Liao et al., 2003). In particular, it has been notedthat a co-solvent mixture may be critical in defining
the optimal reaction medium for the lipases. This work
indicates that the use of this co-solvent mixture in the
enzymatic biodiesel production has several advantages:(a) both the negative effects caused by excessive methanoland co-product glycerol can be eliminated completely;(b) high reaction rates and conversion can be obtained;(c) no catalyst regeneration steps are needed for lipasereuse; and (d) the operational stability of the catalyst is
high. Again, as with other approaches, one of the mostsignificant roadblocks to demonstrating the validity ofthis approach lies in the conversion of algal oil extracts
at a commercial scale and at competitive prices.
To that end, much R&D is needed in the discovery,
engineering, and optimization of enzymes that arecapable of producing these reactions in a variety ofenvironments and on different types of oil feedstocks(Lopez-Hernandez et al., 2005). Bioprospecting forthe enzymes in extreme environments may produce
novel enzymes with desired characteristics that are
more suitable for industrial applications (Guncheva
et al., 2008). Enzyme immobilization may also playa key role in developing an economic method of
biocatalytic transesterification (Yamane et al., 1998).
Other important issues that need further exploration
are developing enzymes that can lyse the algal
cell walls; optimizing specific enzyme activity tofunction using heterogeneous feedstocks; defining
necessary enzyme reactions (cell wall deconstruction
and autolysin); converting carbohydrates intosugars; catalyzing nucleic acid hydrolysis; andconverting lipids into a suitable diesel surrogate.

Catalytic Cracking
The transesterification catalysts presented above arevery strong and relatively mature in the field of biofuel
production. Although very effective and relatively
economical, these catalysts still require purification
and removal from the product stream, which increases
the overall costs. One potential solution to this is thedevelopment of immobilized heterogeneous and/or homogeneous catalysts that are very efficient andinexpensive (McNeff et al., 2008). Acid and basic catalysts
could be classified as Brönsted or Lewis catalysts.
However, in many cases, both types of sites could bepresent and it is not easy to evaluate the relative importanceof the two types of sites in the overall reaction in termsof efficiency and cost. Lewis acid catalysts, such as
AlCl3 or ZnCl2, have been proven as a viable means ofconverting triacylglycerols into fatty acid methyl esters.

6. Algal Biofuel Conversion Technologies

55

The presence of a co-solvent, such as tehtrahydrofuran,can play a vital role in achieving high conversion
efficiencies of up to 98% (Soriano et al., 2009).
In another example, catalysts derived from the titanium
compound possessing the general formula ATixMO, inwhich A represents a hydrogen atom or an alkaline metal
atom, M a niobium atom or a tantalum atom, and x is an
integer not greater than 7, were employed in vegetable oiltransesterification. The catalysts obtained are stable andgive high glycerol yield with high activities. A typical
FAME yield of 91% and glycerol yield of 91% wereobtained in a fixed-bed reactor at 200˚C and 35 bar, using
HTiNbO3 as the catalyst. Vanadate metal compounds
are stable, active catalysts during transesterification,with TiVO4 being the most active (Cozzolino et al.,2006). This catalyst is also more active than HTiNbO3,
producing the same yields with lower residence times.
Double-metal cyanide Fe-Zn proved to be promisingcatalysts resulting in active transesterification of oil.
These catalysts are Lewis acids, hydrophobic (at reaction
temperatures of about 170˚C), and insoluble. Moreover,they can be used even with oils containing significant
amounts of free fatty acids and water, probably due to thehydrophobicity of their surface. The catalysts are activein the esterification reaction, reducing the concentrationof free fatty acids in non-refined oil or in used oil. Other
catalyst examples include MgO, CaO, and Al2O3.
One of the most difficult challenges is finding an ideal
heterogeneous catalyst that has comparable activity
in comparison to the homogenous catalyst at lower
temperatures than the ones currently used (~220 - 240°C).
At these temperatures, the process pressure is high(40 - 60 bar), which translates to very costly plant designand construction requirements. Many of the catalysts
presented above seem to be good candidates for industrial
process development but must resist poisoning and theleaching of active components. There remain significant
fundamental studies and unanswered questions that must
be completed before these catalysts are fully understood.
One particular concern is the stability and longevity of
the catalysts in a representative reaction environment.

56

6. Algal Biofuel Conversion Technologies

Conversion to Renewable Diesel,
Gasoline, and Jet Fuel
All of the processes that take place in a modern petroleum
refinery can be divided into two categories, separationand modification of the components in crude oil to yieldan assortment of end products. The fuel products are a
mixture of components that vary based on input stream
and process steps, and they are better defined by theirperformance specifications than by the sum of specificmolecules. As noted in chapter 8, gasoline, jet fuel, anddiesel must meet a multitude of performance specifications
that include volatility, initial and final boiling point,
autoignition characteristics (as measured by octane number
or cetane number), flash point, and cloud point. Although
the predominant feedstock for the industry is crude oil, theoil industry has begun to cast a wider net and has spenta great deal of resources developing additional inputs
such as oil shale and tar sands. It is worth noting that the
petroleum industry began by developing a replacement
for whale oil, and now it is apparent that it is beginning toreturn to biological feedstocks to keep the pipelines full.
Gasoline, jet fuel, and diesel are generally described as“renewable” or “green” if it is derived from a biologicalfeedstock, such as biomass or plant oil, but have essentiallythe same performance specifications as the petroleumbased analog. A major characteristic of petroleum-derived
fuels is high energy content which is a function of anear-zero oxygen content. Typical biological molecules
have very high oxygen contents as compared to crude oil.
Conversion of biological feedstocks to renewable fuels,
therefore, is largely a process of eliminating oxygen andmaximizing the final energy content. From a refinery’s
perspective, the ideal conversion process would make useof those operations already in place: thermal or catalytic
cracking, catalytic hydrocracking and hydrotreating,and catalytic structural isomerization. In this way, thefeedstock is considered fungible with petroleum andcan be used for the production of typical fuels without
disruptive changes in processes or infrastructure.
Various refiners and catalyst developers have alreadybegun to explore the conversion of vegetable oils andwaste animal fats into renewable fuels. Fatty acids arewell suited to conversion to diesel and jet fuel with few
processing steps. This process has already provided therenewable jet fuel blends (derived from oils obtained
from jatropha and algae) used in recent commercial jet
test flights. On the other hand, straight chain alkanes
are poor starting materials for gasoline because they
provide low octane numbers, demanding additional
isomerization steps or high octane blendstocks.

Algal lipids can be processed by hydrothermal treatment(basically, a chemical reductive process). Referred to ashydrotreating, this process will convert the carboxylic
acid moiety to a mixture of water, carbon dioxide, orcarbon monoxide, and reduce double bonds to yieldhydrocarbons. Glycerin can be converted to propane
which can be used for liquefied petroleum gas.
The primary barrier to utilizing algae oils to makerenewable fuels is catalyst development. Catalysts incurrent use have been optimized for existing petroleum
feedstocks and have the appropriate specificity and activity
to carry out the expected reactions in a cost-effective
manner. It will be desirable to tune catalysts such that theattack on the oxygen-bearing carbon atoms will minimize
the amount of CO and CO2 lost, as well as the amount of
H2 used. Refinery catalysts have also been developed tofunction within a certain range of chemical components
found within the petroleum stream (e.g., metals, and sulfur
and nitrogen heteroatoms) without becoming poisoned.
Crude algal oil may contain high levels of phosphorousfrom phospholipids, nitrogen from extracted proteins, andmetals (especially magnesium) from chlorophyll. It will
be necessary to optimize both the level of purification ofalgal lipid as well as the tolerance of the catalyst for thecontaminants to arrive at the most cost-effective process.

6.4 Processing of Algal
Remnants after Extraction
One other critical aspect in developing a conversion
technology that derives benefit from every potential
input is the conversion of algal remnants afterconversion of algal feedstock into fuel. This
includes the anaerobic digestion of algal remnants
to produce biogas, as well as the fermentation of
any recoverable polysaccharides into biofuels.
Anaerobic digestion can be effectively used as a meansof producing biogas from algae and algal remnants after
extraction (Ashare and Wilson, 1979). In particular, theorganic fractions of the algae remaining after oil extraction
are amenable to anaerobic digestion. In addition, once
the algae has been harvested, little if any pretreatment
is required. The biogas product typically contains 60%
methane and 40% CO2 by volume. The liquid effluent
contains soluble nitrogen from the original algal proteins;the nitrogen can be recovered in the form of ammonia
for recycle to the culture. There will also likely be a highamount of polysaccharides and other oligosaccharides
present in the algal remnants that are well suited for
traditional fermentation into ethanol and other biofuels.

6. Algal Biofuel Conversion Technologies

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60

6. Algal Biofuel Conversion Technologies

7. Co-products
The “guiding truth” is that if biofuel production isconsidered to be the primary goal, the generation of otherco-products must be correspondingly low since theirgeneration will inevitably compete for carbon, reductant,and energy from photosynthesis. Indeed, the concept ofa biorefinery for utilization of every component of thebiomass raw material must be considered as a means toenhance the economics of the process. This chapter willaddress these options and discuss how some of them
are better opportunities as they will not readily saturate
corresponding markets in the long term.
This chapter will also address within the context of thebiorefinery the possibility of coupling biomass cultivation
with CO2 mitigation (for carbon credits) and wastewater
treatment (for nutrient removal) to provide additional
benefits to the technology, without invoking competing coproducts.
Using appropriate technologies, all primary componentsof algal biomass – carbohydrates, fats (oils), proteins anda variety of inorganic and complex organic molecules –can be converted into different products, either throughchemical, enzymatic or microbial conversion (see Chapter
6). The nature of the end products and of the technologies
to be employed will be determined, primarily by the
economics of the system, and they may vary from region toregion according to the cost of the raw material (Willke andVorlop, 2004). Moreover, novel technologies with increased
efficiencies and reduced environmental impacts may haveto be developed to handle the large amount of waste thatis predicted to be generated by the process. The topic ofconversion of algal biomass to other biofuels has alreadybeen discussed (see Chapter 6); this chapter will focus on
the non-fuel co-products.
Under the biorefinery concept (Exhibit 7.1), the productionof industrial, high-value and high-volume chemicals fromamino acids, glycerol, and nitrogen-containing componentsof algal biomass becomes feasible (Mooibroek et al., 2007)
and must be considered in determining the economics ofthe process.
The use of terms such as “high volume” or “high value”
can be extremely subjective, as a “high value” productto a fine chemical producer might be well over several
dollars/lb, but considerably under a dollar for a commodity
producer. For the purposes of the Roadmap, a reasonably
valued chemical is defined as one that will cost roughly$0.30 - $1.00/lb, and can be produced at a volume ofroughly 100 - 500 x106 lbs/yr.

7.1 Commercial Products fromMicroalgae and Cyanobacteria
A large number of different commercial products have been
derived from microalgae and cyanobacteria. As summarizedin Exhibit 7.2, these include products for human and animal
nutrition, poly-unsaturated fatty acids, anti-oxidants,
coloring substances, fertilizers and soil conditioners, anda variety of specialty products such as bioflocculants,
biodegradable polymers, cosmetics, pharmaceuticals,
polysaccharides, and stable isotopes for research purposes.

Exhibit 7.1 An overview ofthe biorefinery concept

Biorefinery
Aquaculture

Raw biomass,
wastewater, CO2
Special substances:pigments, dyes, flavors,
aromatic essences,
enzymes, hormones, etc.
Heat, electricity
Modified from Kamm and Kamm, 2007

Primary Refinery

Conversion

Industry

Carbohydrates

Complex
Substances

Fats

Inorganics

Proteins

Products andresidues fromconversion
processes

Energy7. Co-products61

By definition, these existing markets (and associatedproduction plants and distribution channels) are for highvalue products or co-products from algae, not commodity
products. Yet the existing fossil fuels market is and thefuture algal-based biofuels market (designed in part tosupplant the fossil fuels market) must be commodities
based to meet required volumes at price points acceptable
to the consumer. With the possible exception of the existing
market for microalgal biomass for animal nutrition andsoil fertilizer, the biofuels markets will involve volumes(of biomass, product, etc.) and scales (sizes and numbersof commercial plants) that are significantly less than those
associated with the existing high-value algae-derived
products.
Therein lies a major conundrum associated with thenascent algal-derived biofuels market: in the long term,
massive lipid production dominates; yet in the short term,
co-products of higher value in the marketplace must be
pursued in order to offset the costs of production of algalderived biofuels. Although it is clear that co-products may
improve the economic viability of some algae processes
in the short-term, the goal of the industry is to produce
transportation fuels below their market price, thereby
increasing fuel supplies without drastically increasing price.
This situation, is anticipated to continue until 1) a sufficientnumber of the challenges outlined earlier in the Roadmap
for biofuel production have been overcome and associatedlife cycle costs are reduced to realize sustainable biofuel
production at volumes and pricepoints that meet consumer
demands or 2) new co-products that are low cost and havevery large potential markets are developed.
Food and Feed
• Human Health Food Supplement: The consumption of
microalgal biomass as a human health food supplement
is currently restricted to only a few species, e.g.,
Spirulina (Arthospira), Chlorella, Dunalliella, andto a lesser extent, Nostoc and Aphanizomenon(Radmer, 1996; Pulz and Gross, 2004; Spolaore etal., 2006).
The production includes ca. 3,000 t/yr Spirulina; ca.
2,000 t/yr Chlorella; ca. 1,200 t/yr Dunaliella; ca.
600 t/yr Nostoc; and ca. 500 t/yr Aphanizomenon.
The market, currently at about 2.5 billion
US$, is expected to grow in the future.
• Aquaculture: Microalgae are also used as feed in theaquaculture of mollusks, crustaceans (shrimp), andfish (Benemann, 1990; Malcolm et al., 1999). Most
frequently used species are Chaetoceros, Chlorella,
Dunaliella, Isochrysis, Nannochloropsis, Nitzschia,
Pavlova, Phaeodactylum, Scenedesmus, Skeletonema,62

7. Co-products

Spirulina, Tetraselmis, and Thalassiosira. Both theprotein content and the level of unsaturated fatty
acids determine the nutritional value of microalgal
aquaculture feeds. The market size, currently at ~700
million US$, is expected to expand significantly.
• Animal Feed Additive: Microalgal biomass has also
been used with good results (i.e., better immune
response, fertility, appearance, weight gain, etc.) asa feed additive for cows, horses, pigs, poultry, andeven dogs and cats. In poultry rations, microalgal
biomass up to a level of 5 - 10% (wt.) can be safely
used as a partial replacement for conventional proteins(Spoalore et al., 2006). The main species used inanimal feed are Spirulina, Chlorella and Scenesdesmus.
The market for microalgal animal feeds, estimatedto be about 300 million US$, is quickly growing.
However, it is important to note that since the fluegas from coal-fired power plants that will be used
to supply carbon dioxide to the cultures will containsignificant amounts of lead, arsenic, cadmium andother toxic elements, the resulting non-oil algal
biomass is very likely to be unsuitable for use as an
animal feed, particularly given the fact that algae
are known to be effective at metal absorption.
Polyunsaturated Fatty Acids (PUFAs)
Microalgae can also be cultured for their high content
in PUFAs, which may be added to human food andanimal feed for their health promoting properties(Benemann, 1990; Radmer, 1994 and 1996). The mostcommonly considered PUFAs are arachidonic acid (AA),docohexaenoic acid (DHA), γ-linolenic acid (GLA), andeicosapentaenoic acid (EPA). AA has been shown to besynthesized by Porphyridium, DHA by Crypthecodinium
and Schizochytrium, GLA by Arthrospira, and EPA by
Nannochloropsis, Phaeodactylum and Nitzschia (Spolaore
et al., 2006). However, only DHA has been produced thus
far on a commercial scale by microalgae. All other PUFAs
are more cost-effectively produced from non-algal sources(e.g., GLA from evening primrose oil). Although small,the DHA oil market is quickly growing, having presently aretail value of 1.5 billion US$.
Anti-Oxidants
A number of anti-oxidants, sold for the health food market,
have also been produced by microalgae (Borowtizka, 1986;
Benemann, 1990; Radmer, 1996). The most prominentis β–carotene from Dunaliella salina, which is sold either
as an extract or as a whole cell powder ranging in pricefrom 300 to 3,000 US$ per kg (Spolaore et al., 2006). The
market size for β–carotene is estimated to be greater than
280 million US$.

Coloring Agents
Microalgae-produced coloring agents are used as naturaldyes for food, cosmetics, and research, or as pigments
in animal feed (Borowitzka, 1986; Benemann, 1990).
Astaxanthin, a carotenoid produced by Hematococcus
pluvialis, has been successfully used as a salmon feed togive the fish meat a pink color preferred by the consumers(Olaizola, 2003; Spolarore et al., 2006). Astaxanthin, andthe related carotenoids lutein and zeaxantin, have also
been used in the feed of carp and even chicken (Puls andGross, 2004; Spolaore et al., 2006). Phycobiliproteins,
i.e., phycoerythrin and phycocyanin, produced by
the cyanobacterium Arthrospira and the rhodophyte
Porphyridium, are used as food dyes, pigments incosmetics, and as fluorescent reagents in clinical or researchlaboratories (Spolaore et al., 2006).

Exhibit 7.2 Summary of microalgae commercial products market
MARKET SIZE(TONS/YR)SALES VOLUME(MILLION $US/YR)

REFERENCE

Health Food

7,000

2,500

Pulz&Gross (2004)

Aquaculture

1,000

700

Pulz&Gross (2004)
Spolaore et al., (2006)

Animal Feed Additive

No available information

300

Pulz&Gross (2004)

ARA

No available information

20

Pulz&Gross (2004)

DHA

<300

1,500

Pulz&Gross (2004)
Spolaore et al., (2006)

PUFA Extracts

No available information

10

Pulz&Gross (2004)

COMMERCIAL PRODUCTBIOMASS

POLY-UNSATURATEDFATTY ACIDS (PUFAs)

GLA

Potential product, no current commercial market

Spolaore et al., (2006)

EPA

Potential product, no current commercial market

Spolaore et al., (2006)

ANTI-OXIDANTS
Beta-Carotene

1,200

>280

Pulz&Gross (2004)
Spolaore et al., (2006)

Tocopherol CO2 Extract

No available information

100-150

Pulz&Gross (2004)

Astaxanthin< 300 (biomass)< 150

Pulz&Gross (2004)
Spolaore et al., (2006)

Phycocyanin

No available information>10

Pulz&Gross (2004)

Phycoerythrin

No available information>2

Pulz&Gross (2004)

No available information

5,000

Pulz&Gross (2004)
Metting&Pyne (1986)

COLORING SUBSTANCESFERTILIZERS/SOIL CONDITIONERS
Fertilizers, growth promoters,
soil conditioners

7. Co-products

63

Fertilizers
Currently, macroalgae (i.e., seaweeds) are used as a plantfertilizer and to improve the water-binding capacity andmineral composition of depleted soils (Metting et al., 1990).
Microalgal biomass could in principle serve the same
purpose. Furthermore, plant growth regulators could bederived from microalgae (Metting and Pyne, 1986).
Other Specialty Products
There are a number of specialty products and chemicals
that can be obtained from microalgae. These include
bioflocculants (Borowitzka, 1986), biopolymers andbiodegradable plastics (Philip et al., 2007; Wu et al., 2001),
cosmetics (Spolaore et al., 2006), pharmaceuticals andbioactive compounds (Burja et al., 2001; Metting and Pyne,
1986; Olaizola, 2003; Singh et al., 2005; Pulz and Gross,2004), polysaccharides (Benemann, 1990; Borowitzka,
1986; Pulz and Gross, 2004), and stable isotopes forresearch (Benemann, 1990, Radmer, 1994; Pulz and Gross,2004). The market for these specialty products is likely to
be very small due to their specialized applications.

7.2 Commercial Products
from Macroalgae
Macroalgae possess high levels of structuralpolysaccharides that are extracted for their commercial
value (Exhibit 7.3). They include alginate from brownalgae and agar and carrageenen from red algae. Alginate,

which occurs in high concentrations in brown seaweeds,
is considered recalcitrant to ethanol fermentation since
the redox balance favors formation of pyruvate as the end
product (Forro, 1987).

7.3 Potential Options for the
Recovery of Co-products
Co-products from algal refineries should address oneof these three criteria to be commercially viable andacceptable:
1. Identical to an existing chemical, fuel, or other product.
In this instance, the only issue is price. The production
cost of the new product must be equivalent to thematerial it replaces and to be competitive typically, it
must be produced at a cost 30% lower than the existingmaterial (shutdown economics). This sets a high bar
but has been achieved for some chemicals and proteins/
nutritional products.
2. Identical in functional performance to an existingchemical, fuel or other product. Here price is a major
factor, but the source of the material can often provide
some advantage. This occurs with natural oils which
manufacturers in many cases would prefer if the costs
were comparable, or with replacements such as algal
proteins for distillers dried grains from corn dry grind
ethanol processing. Price becomes less of an issue if
the product can be labeled “organic” and thus saleable
at a premium.

Exhibit 7.3 Global value of seaweed products per annum (McHugh, 2003)
PRODUCT

Human Food (Nori, aonori, kombu, wakame, etc.)

VALUE$5 billion

Algal hydrocolloids
Agar (Food ingredient, pharmaceutical, biological/microbiological)$132 million

Alginate (Textile printing, food additive, pharmaceutical, medical)$213 million

Carrageenen (Food additive, pet food, toothpaste)$240 million

Other uses of seaweeds
Fertilizers and conditioners$5 million

Animal Feed

$5 million

Macroalgal Biofuels

Negligible

TOTAL
64

7. Co-products$5.5-6 BILLION

3. New material with unique and useful functional
performance characteristics. In this case, the issues
are less related to costs and more to the functional
performance and potentially enhanced performance ofthe new product.
There are at least five different options for recovering
economic value from the lipid-extracted microalgal biomass(Exhibit 7.4). These are:
• Option 1 – Maximum energy recovery fromthe lipid extracted biomass, with potential
use of residuals as soil amendments• Option 2 – Recovery of protein from the lipidextracted biomass for use in food and feed
• Option 3 – Recovery and utilization of non-fuel lipids• Option 4 – Recovery and utilization of carbohydrates
from lipid-extracted biomass, and the glycerol
from the transesterification of lipids to biodiesel• Option 5 – Recovery/extraction of fuellipids only, with use of the residual biomass
as soil fertilizer and conditioner
Each option and its associated technologies and future
research needs are discussed below.
Option 1. Maximum Energy Recovery from the
Lipid-Extracted Biomass, with Potential Use of
Residuals as Soil Amendments
Given the large amounts of lipid-extracted biomass residues
that will likely be generated in future microalgal biofuels

production systems, it may be difficult to identify large
enough markets for potential co-products. Therefore, one
option would be to convert as much of the lipid-extracted
biomass into energy, which could then be either sold on
the open market or used on-site in the various biorefinery
operations.
The most promising energy recovery technology, bothfrom a practical and economic perspective, is the anaerobic
digestion of lipid-extracted biomass. Anaerobic digestion ofwhole (i.e., non-extracted) micro and macroalgal biomasshas been successfully demonstrated, with reported methane
yields of about 0.3 l per gram volatile solids (Huesemann
and Benemann, 2009). The economic value of the produced
methane is equivalent to about $100 per ton of digested
biomass, which is significant in terms of reducing theoverall cost of liquid biofuels production. The residuals
remaining after anaerobic digestion could either be recycled
as nutrients for algal cultivation or could be sold as soil
fertilizers and conditioners, as is currently already done forcertain waste water treatment sludges (see http://www.unh.
edu/p2/biodiesel/pdf/algae_salton_sea.pdf).
In addition to anaerobic digestion, thermochemical
conversion technologies, such as pyrolysis, gasification,and combustion, could also be potentially considered forthe recovery of energy from the lipid-extracted biomass(see Chapter 6). These technologies are able to convert
a much larger fraction of biomass into fuels. However,these technologies are still in the testing and development
stage, and because of their large energy inputs (temperatureand pressure), could have poor or even negative energybalances (Huesemann and Benemann, 2009). Nevertheless,

Exhibit 7.4 Overview of the fivepotential options for the recovery
and use of co-products

Recycle Nitrogen Gases

Algal Biomass

Option 1

Extract Lipids
for Fuel

EnergyBurn Residue

Ash/ Soil Amendments
Option 5

Soil Fertilizer/ Conditioners

Dry Residue Processing

Proteins as
Co-Products
Non-Fuel
Lipids

Option 2

Food/ Feed Supplement

Processing
Option 3
Chemical/ Biological Conversion
Option 4

Carbohydrates

Surfactants/ Bioplastics

Ethanol/ Butanol/ Glycerol

Chemical/ Biological Conversion

7. Co-products

65the thermochemical conversion of lipid-extracted biomass
has the potential advantage that the resulting nitrogencontaining gases (e.g., ammonia and nitrous oxides) could
be recycled into the microalgal culture ponds, thereby
reducing the expense for nitrogen fertilizers. Furthermore,
the mineral-rich ash generated by these thermochemical
processes could possibly be used for nutrient recycle or as asoil amendment.
Option 2. Recovery of Protein from the Lipid-Extracted
Biomass for Use in Food and Feed
Following the extraction of lipids from the microalgal
biomass for liquid biofuel production, the protein fraction
from the residual biomass could be extracted and used asa food and feed supplement. As was pointed out above,the market for animal feed (cattle, pigs, poultry, fish, andpets) is already very large and growing (estimated to rise
to approximately 60 million tons per year for distillers dry
grains plus soluble (DDGS)) (Berger and Good, 2007).
The current price for DDGS ranges from $110 - 150 per ton(http://www.ams.usda.gov/mnreports/sj_gr225.txt). Since
protein is generally the key and often limiting ingredientin animal feed, supplementation with microalgal proteins
could be advantageous. Furthermore, human nutrition may
also benefit from supplementation with microalgal proteins.
The byproduct material, which contains proteins, mightmake a useful animal feed. However, feeding studies
indicate that algae cannot be used as a high percentage
of feed, due to issues such as taste of the meat or eggs,
and interactions with animal digestion. Furthermore, theoverall size of the animal feed market is small, relative
to the amount of byproduct that would be produced, andthe individual local markets for animal feed are often not
located adjacent to areas where algae may be produced. As
a result, byproduct markets are likely to be overwhelmed,
and byproduct prices will be greatly depressed versus
current levels.
In addition, it may be possible to recover important
enzymes such as cellulases or other industrial enzymes
from the lipid-extracted biomass. However, this option
would require the use of specially selected or engineered
microalgal strains capable of producing these enzymes. The
market for industrial enzymes, specifically cellulases for
pretreating lignocellulosic feedstocks prior to fermentation
to fuel ethanol, is potentially very large. Assuming that (a)microalgal cellulases could be provided at a cost of lessthan $0.20 per gallon ethanol; (b) approximately 100 gramsof cellulase are needed per gallon of ethanol; and (c) atleast 10.5 billion gallons of lignocellulosic ethanol will be
produced by 2020, the projected market for cellulases ispotentially very large, i.e., 1 billion kg.
66

7. Co-products

Option 3. Recovery and Utilization of Non-fuel Lipids
It is well known that microalgae can synthesize a variety
of fatty acids with carbon numbers ranging from C10 to C24,
depending on the algal species and culturing conditions(Hu et al., 2008). Since the generation of gasoline, jet fuel,and diesel substitutes will require specific ranges of carbon
chain length, it will be necessary to either separate theproduct into the appropriate range or rearrange the carbon
chains through catalytic cracking and catalytic reforming.
It may be worthwhile, however, to separate specificlipids present in the algal oil that have utility as chemical
feedstocks for the manufacture of surfactants, bioplastics,
and specialty products such as urethanes, epoxies,
lubricants, etc.
Option 4. Recovery and Utilization of Carbohydrates
from Lipid-Extracted Biomass, and the Glycerol from theTransesterification of Lipids to Biodiesel
After the extraction of lipids, the residual microalgal
biomass may contain sufficient levels of carbohydrates that
could be converted through anaerobic dark fermentations
to hydrogen, solvents (acetone, ethanol, and butanol), andorganic acids (formic, acetic, propionic, butyric, succinic,
and lactic) (Huesemann and Benemann, 2009; Kamm andKamm, 2007; Kawaguchi et al., 2001). Hydrogen andethanol could be used as biofuel, while butanol and organic
acids could serve as renewable feedstocks for the chemicals
industry. For example, butanol is a valuable C4 compoundfor chemical synthesis of a variety of products, including
polymers that are currently produced from fossil oilderived ethylene and propylene, thus butanol could serve
as a renewable substitute (Zerlov et al., 2006). Similarly,
succinate is an intermediate in the production of a variety
of industrial surfactants, detergents, green solvents andbiodegradable plastics (Kamm and Kamm, 2007). Lactic
acid, which can be converted into polypropylene oxide,is the starting material for the production of polyester,polycarbonates and polyurethanes; it is also used in theindustrial production of green solvents, and its applications
include the pharmaceutical and agrochemical industries(Datta et al., 1995).
Glycerol, a byproduct of the transesterification of
microalgal lipids to biodiesel, could also be anaerobicallyfermented to the above mentioned and other end products(Yazdani and Gonzalez, 2007). Furthermore, glycerol
could be converted by certain bacteria to 1,3-propanediol,which is used in the formulation of a variety of industrial
products such as polymers, adhesives, aliphatic polyesters,solvents, antifreeze, and paint (Yazdani and Gonzalez,
2007; Choi, 2008). Finally, glycerol could be used togenerate electricity directly in biofuel cells (Yildiz andKadirgan, 1994). Once again, the issue of scale enters in.
Production of 1 billion gallons of biodiesel will result in
the formation of more than 400,000 tons of glycerol (http://
www.biodieselmagazine.com/article.jsp?article_id=377).
As the current production levels for biodiesel (700 million
gallons in 2008) already has the market for glycerol
saturated, additional capacity from algal lipids may find it
exceedingly difficult to find uses.
It may also be possible to extract microalgal
polysaccharides for use as emulsifiers in food and industrial
applications (Mooibroek et al., 2007). Finally, microalgal
carbohydrates could be recycled into pulp and paper
streams, substituting for lignocellulosic materials derived
from forestry resources.
As was the case with Option 3, this option will also require
R&D efforts as discussed under Chapter 2, Algal Biology;
specifically, these are the development of high throughput
technologies for the quantitative characterization of

microalgal metabolites, including sugars and complex
carbohydrates; and the development of genetic engineering
tools to improve yields of desired products, including
carbohydrates, if desired.
Option 5. Recovery (Extraction) of Fuel Lipids Only, with
Use of the Residual Biomass as Soil Fertilizer
and Conditioner
In case none of the above mentioned four options are
economical, i.e., the recovery and use of energy, proteins,non-fuel lipids, and carbohydrates is not cost-effective, it
is possible to revert to the most simple option (Option 5),
which involves the extraction of only fuel lipids and thesubsequent use of the biomass residues rich in nitrogen andorganic matter as soil fertilizer and conditioners. As was
mentioned above, the market for organic fertilizer is large
and potentially growing.

References
Benemann, J.R. (1990). Microalgae products and production: An overview. Developments in industrial microbiology. Journal of Industrial
Microbiology. Suppl. No. 5. (31), 247-256.
Berger, L.L., D. L. Good. (2007). Distillers dried grains plus solubles utilization by livestock and poultry in corn-based ethanol in Illinois
and the U.S. A Report from the Department of Agricultural and Consumer Economics, University of Illinois, Champaign-Urbana.
Borowitzka, M.A. (1986). Microalgae as sources of fine chemicals. Microbiological Sciences. 3(12), 372-375.
Burja, A.M., B. Banaigs, E. Abou-Mansour, J.G. Burgess, and P.C. Wright. (2001). Marine cyanobacteria – A prolific source of natural 		products. Tetrahedon. (57), 9347-9377.
Choi, W.J. (2008). Glycerol-based biorefinery for fuels and chemicals. Recent Patents on Biotechnology. (2), 173-180.
Datta, R., S.P. Tsai, P. Bonsignore, S.H. Moon, J.R. Frank. (2006). Technological and economic potential of poly(lactic acid) and lactic acidderivatives. FEMS Microbiological Review. (16), 221-231.
Forro, J. (1987). Microbial degradation of marine biomass. Developments in Aquaculture and Fisheries Science (Netherlands).
Hu, Q., M. Sommerfeld, E. Jarvis, M. Ghirardi, M. Posewitz, M. Seibert, A. Darzins. (2008). Microalgal triacylglycerols as feedstocks forbiofuel production: Perspectives and advances. The Plant Journal. (54), 621-63.
Huesemann, M.H., J.R. Benemann. (2009). Biofuels from microalgae: Review of products, processes, and potential, with special
focus on Dunaliella sp. The alga dunaliella: biodiversity, physiology, genomics, and biotechnology. Science Publishers,
New Hampshire.
Kamm, B. M. Kamm. (2007). Biorefineries – multi product processes. Advances in Biochemical Engineering/Biotechnology.
(105),175-204.
Kawaguchi H, K. Hashimoto, K. Hirata, K. Miyamoto. (2001). H2 production from algal biomass by a mixed culture of rhodobium marinumA-501 and lactobacillus amylovorus. Journal of Biosciences Bioengineering. (91), 277-282.
McHugh, D. J. (2003). A guide to the seaweed industry. Food and Agriculture Organization.
Metting, B., J.W. Pyne. (1986). Biologically active compounds from microalgae. Enzyme Microbial Technology. (8), 386-394.
Metting, B., W.J. Zimmerman, I. Crouch, J. van Staden. (1990). Agronomic uses of seaweed and microalgae. Introduction to Applied 		Phycology. SPB Academic Publishing, The Hague, Netherlands. 589-627.

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Mooibroek, H., N. Oosterhuis, M. Giuseppin, M. Toonen, H. Franssen, E. Scott, J. Sanders, A. Steinbüchel. (2007). Assessment 		
of technological options and economical feasibility for cyanophycin biopolymer and high-value amino acid production. Applied 		
Microbiology Biotechnology. (77), 257-267.
Olaizola, M. (2003). Commercial development of microalgal biotechnology: From the test tube to the marketplace.
Biomolecular Engineering. (20), 459-466.
Philip, S., T. Keshavarz, I. Roy. (2007). Polyhydroxyalkanoates: Biodegradable polymers with a range of applications. Journal of Chemical
Technology and Biotechnology. (82), 233-247.
Pulz, O., W. Gross. (2004).Valuable products from biotechnology of microalgae. Applied Microbiology and Biotechnology. (65), 635-648.
Radmer, R.J., B.C. Parker. (1994). Commercial applications of algae: Opportunities and Constraints. Journal of Applied Phycology.
(6), 93-98.
Radmer, R.J. (1996). Algal diversity and commercial algal products. BioScience. 46(4), 263-270.
Singh, S., B.N. Kate, U.C. Banerjee. (2005). Bioactive compounds from cyanobacteria and microalgae: An overview. Critical Reviews in
Biotechnology. (25), 73-95.
Spolaore, P., C. Joannis-Cassan, E. Duran, A. Isambert. (2006). Commercial applications of microalgae. Journal of Bioscience and 		Bioengineering. 101(2), 87-96.
Willke, T.H., K.D. Vorlop. (2004). Industrial bioconversion of renewable resources as an alternative to conventional chemistry.
Applied Microbiology and Biotechnology. (66), 131-142.
Wu, G.F., Q.Y. Wu, Z.Y. Shen. (2001). Accumulation of poly-b-hydroxybutyrate in cyanobacterium synechocystis sp. PCC6803.
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Yazdani, S.S., R. Gonzalez. (2007). Anaerobic fermentation of glycerol: A path to economic liability for the biofuels industry.
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(71), 587-597.

68

7. Co-products

8. Distribution and Utilization
Distribution and utilization are challenges associated with
virtually all biofuels. Although the biofuel product(s)from algal biomass would ideally be energy-dense
and completely compatible with the existing liquidtransportation fuel infrastructure, few studies exist that
address outstanding issues of storing, transporting,pipelining, blending, combusting, and dispensing algal
biomass, fuels intermediates, biofuels, and bioproducts.
Being intermediate steps in the supply chain, distribution
and utilization need to be discussed in the context of earlier
decision points, such as cultivation and harvesting. In turn,these logistics through end-use issues influence siting,scalability, and the ultimate economics and operations ofan integrated algal biofuels refinery. As a variety of fuelproducts – ethanol, biodiesel, higher alcohols, pyrolysis oil,syngas, and hydroreformed biofuels – are being consideredfrom algal biomass resources, the specific distribution andutilization challenges associated with each of these possible
opportunities is discussed.

8.1 Distribution
Lowering costs associated with the delivery of raw
biomass, fuel intermediates, and final fuels from thefeedstock production center to the ultimate consumer
are common goals for all biofuels. In all cases, biofuels
infrastructure costs can be lowered in four ways:•

Minimizing transport distance between process units;•

Maximizing the substrate energy-density and stability;•

Maximizing compatibility with existing infrastructure(e.g. storage tanks, high capacity; delivery vehicles,
pipelines, dispensing equipment, and end-use vehicles);and•Optimizing the scale of operations to the parametersstated above.

Distribution is complicated by the fact that several
different fuels from algae are being considered, as
discussed in detail in Chapter 6 (Algal Biofuel Conversion
Technologies). Ethanol, biodiesel, biogas, renewablegasoline, diesel, and jet fuels are all possible products
from algal biomass. Each of these different fuels has
different implications for distributions. Some of these fuelsappear to be more compatible with the existing petroleum
infrastructure. Specifically, jet-fuel blends from a varietyof oil-rich feedstocks, including algae, have been shown
to be compatible for use in select demonstration flights(Buckman and Backs, 2009; Efstathiou and Credeur, 2009).

It is also anticipated that gasoline and diesel range fuelsfrom algae will not require significant distribution systemmodifications during or after processing in the refinery.
While the demonstration flights mitigate someinfrastructure concerns, other distribution aspects
concerning algal biomass, fuel intermediates, and final fuelsremain poorly studied:• First, the stability of the algal biomass under different
production, storage, and transport scenarios ispoorly characterized, with some evidence suggestingthat natural bacterial communities increase therate of algae decomposition (Rieper-Kirchner,
1990). In the context of a variety of culturing andharvesting conditions differing in salinity, pH and
dewatering levels, it is difficult to predict how
these factors will influence biomass storage andtransport, and the quality of the final fuel product.
• Second, an issue that impacts oleaginous microalgae
feedstocks is that the transport and storage mechanismsof algal lipid intermediates have not yet been
established. It is conceivable that these “bio-crudes”
will be compatible with current pipeline and tanker
systems. However, it is known that the presenceof unsaturated fatty acids causes auto-oxidation ofoils (Miyashita and Takagi, 1986), which carries
implications for the producers of algae and selection
for ideal lipid compositions. It is also known thattemperature and storage material have important
implications for biodiesel stability (Bondioli et al.,1995). Thus, materials and temperature considerations
similar to plant lipids may be possibly taken into
account for the storage of algae lipids (Hu et al., 2008).
• Third, depending on whether it will be dewatered/densified biomass and/or fuel intermediates that are to
be transported to the refinery, conforming to existing
standards (e.g., container dimensions, hazardous
materials and associated human health impacts, andcorrosivity) for trucks, rails, and barges is criticalto minimizing infrastructure impacts. The optimaltransport method(s) should be analyzed and optimized
for energy-inputs and costs, within the context ofwhere the algae production and biorefinery facilities
are to be sited. These have been challenging issues
for lignocellulosic feedstocks (Hess et al., 2009) andcan be expected to influence the economics of algal
biofuels as well.

8. Distribution and Utilization

69

Ethanol is another likely fuel from algae. With over
10 billion gallons per year produced and consumed
domestically, distribution-related issues for ethanol has
been studied for some time, and algal ethanol can benefit
from these analyses. While not as energy dense as purely
petroleum-derived fuels, ethanol is an important fueloxygenate that can be used in regular passenger vehicles
and special flex-fuel vehicles at up to 10% and 85% gasohol
blends, respectively. However, considerable infrastructure
investments need to be made for higher ethanol blends
to become even more attractive and widespread. One
issue is that ethanol is not considered a fungible fuel; it
can pick up excessive water associated with petroleum
products in the pipeline and during storage, which causesa phase separation when blended with gasoline (Wakeley
et al., 2008). One possible way to address this is to build
dedicated ethanol pipelines; however, at an estimatedcost of $1 million/mile of pipeline, this approach is not
generally considered to be economically viable (Reyold,2000). Another possibility is to distribute ethanol blends byrail, barge, and/or trucks. Trucking is currently the primarymode to transport ethanol blends at an estimated rate of$0.15/ton/kilometer (Morrow et al., 2006). This amount isa static number for low levels of ethanol in the blends (5%to 15%); as the ethanol content in the blend increases, thetransport costs will also increase due to the lower energy
density of the fuel.

8.2 Utilization
The last remaining hurdle to creating a marketable newfuel after it has been successfully delivered to the refuelinglocation is that the fuel must meet regulatory and customer
requirements. As mentioned in Chapter 6, such a fuel issaid to be “fit for purpose.” Many physical and chemical
properties are important in determining whether a fuel is fit
for purpose; some of these are energy density, oxidative andbiological stability, lubricity, cold-weather performance,elastomer compatibility, corrosivity, emissions (regulated
and unregulated), viscosity, distillation curve, ignition
quality, flash point, low-temperature heat release, metal
content, odor/taste thresholds, water tolerance, specificheat, latent heat, toxicity, environmental fate, and sulfur
and phosphorus content. Petroleum refiners have shown
remarkable flexibility in producing fit-for-purpose fuelsfrom feedstocks ranging from light crude to heavy crude,
oil shales, tar sands, gasified coal, and chicken fat, and arethus key stakeholders in reducing the uncertainty about thesuitability of algal lipids and carbohydrates as a feedstock
for fuel production.

70

8. Distribution and Utilization

Typically, compliance with specifications promulgated byorganizations such as ASTM International ensures that afuel is fit for purpose (ASTM International, 2009a, 2009b,
2009c, 2009d, and 2009e). Failure of a fuel to comply witheven one of the many allowable property ranges within
the prevailing specifications can lead to severe problems
in the field. Some notable examples included: elastomercompatibility issues that led to fuel-system leaks when
blending of ethanol with gasoline was initiated; coldweather performance problems that crippled fleets when
blending biodiesel with diesel was initiated in Minnesota
in the winter; and prohibiting or limiting the use of theoxygenated gasoline additive MTBE in 25 states because
it has contaminated drinking-water supplies (McCarthy
and Tiemann, 2000). In addition to meeting fuel standard
specifications, algal biofuels, as with all transportation
fuels, must meet Environmental Protection Agency
regulations on combustion engine emissions.
As is true of any new fuel, it is unlikely that new
specifications will be developed for algal fuels in the nearterm (i.e., at least not until significant market penetration
has occurred); hence, producers of algal fuels should
strive to meet prevailing petroleum-fuel specifications.
Nevertheless, research and technology advancements
may one day yield optimized conversion processes which
can deliver algae-derived compounds with improved
performance, handling, and environmental characteristics
relative to their petroleum-derived hydrocarbon
counterparts. If significant benefits can be demonstrated,
new specifications can be developed (e.g., ASTM D6751
and D7467).
The discussion below is divided into separate sections thatdeal with algal blendstocks to replace gasoline-boilingrange and middle-distillate-range petroleum products,
respectively. These classifications were selected because
the compounds comprising them are largely distinct andnon-overlapping. Within each of these classifications,hydrocarbon compounds and oxygenated compounds aretreated separately, since their production processes and inuse characteristics are generally different.

Algal Blendstocks to Replace
Middle-Distillate Petroleum Products
Petroleum “middle distillates” are typically used to create
diesel and jet fuels. The primary algae-derived blendstocks
that are suitable for use in this product range are biodiesel(oxygenated molecules) and renewable diesel (hydrocarbon
molecules). The known and anticipated end-use problem
areas for each are briefly surveyed below.

Oxygenates: Biodiesel
Biodiesel is defined as “mono-alkyl esters of long
chain fatty acids derived from vegetable oils or animalfats” (ASTM International, 2009b). Biodiesel has been
demonstrated to be a viable fuel for compression-ignitionengines, both when used as a blend with petroleum-derived
diesel and when used in its neat form (i.e., 100% esters)(Graboski and McCormick, 1998). The primary end-use
issues for plant-derived biodiesel are: lower oxidative
stability than petroleum diesel, higher emissions of nitrogenoxides (NOx), and cold-weather performance problems(Knothe, 2007). The oxidative-stability and cold-weather
performance issues of biodiesel preclude it from use as ajet fuel. The anticipated issues with algae-derived biodiesel
are similar, with added potential difficulties including:1) contamination of the esters with chlorophyll, metals,
toxins, or catalyst poisons (e.g., sulfur and phosphorus)
from the algal biomass and/or growth medium; 2) undesired
performance effects due to different chemical compositions;and 3) end-product variability.
Hydrocarbons: Renewable Diesel and
Synthetic Paraffinic Kerosene
The hydrocarbon analog to biodiesel is renewable diesel,
which is a non-oxygenated, paraffinic fuel producedby hydrotreating bio-derived fats or oils in a refinery(Aatola et al., 2009). Algal lipids can be used to produce
renewable diesel or synthetic paraffinic kerosene (SPK),a blendstock for jet fuel. These blendstocks do not haveoxidative-stability problems as severe as those of biodiesel,and renewable diesel actually tends to decrease engineout NOx emissions. Nevertheless, unless they are heavily

isomerized (i.e., transformed from straight- to branchedchain paraffins), renewable diesel and SPK will havecold-weather performance problems comparable to thoseexperienced with biodiesel. Also, as was the case with algal
biodiesel, contaminants and end-product variability areconcerns.

Algal Blendstocks for Alcohol and
Gasoline-Range Petroleum Products
While much of the attention paid to algae is focused on
producing lipids and the subsequent conversion of the lipids
to diesel-range blending components (discussed above),algae are already capable of producing alcohol (ethanol)
directly, and there are several other potential gasoline-range
products that could be produced by algae-based technology/
biorefineries. Petroleum products in the alcohols andgasoline range provide the major volume of fuels used bytransportation vehicles and small combustion engines in
the United States. Ethanol or butanol are the most common
biofuels currently being considered for use in gasoline,
and these alcohols can be produced from fermentation of
starches and other carbohydrates contained in algae.
Additionally, the hydro-treating of bio-derived fats oroils in a refinery will typically yield a modest amount ofgasoline-boiling-range hydrocarbon molecules. Refiners
refer to this material as “hydro-cracked naphtha.” This
naphtha tends to have a very low blending octane andwould normally be “reformed” in a catalytic reformer
within the refinery to increase its blending octane value
prior to use in a gasoline blend.

8. Distribution and Utilization

71References
Aatola, H., Larmi, M., Sarjovaara, T., and Mikkonen, S. (2009). Hydrotreated vegetable oil (HVO) as a renewable diesel fuel: Trade-off
between NOx particulate emission and fuel consumption of a heavy duty engine. SAE International Journal of Engines. 1(1), 12511262.
ASTM International. (2009a). Standard specification for diesel fuel oils. West Conshohocken, PA: ASTM International. Available online
at http://www.astm.org/Standards/D975.htm
ASTM International. (2009b). Standard specification for biodiesel fuel blend stock (B100) for middle distillate fuels. West Conshohocken,
PA: ASTM International. Available online at http://astm.org/Standards/D6751.htm
ASTM International. (2009c). Standard specification for aviation turbine fuels. West Conshohocken, PA: ASTM International. Available
online at http://astm.org/Standards/D1655.htm
ASTM International. (2009d). Standard Specification for Automotive Spark-Ignition Engine Fuel. West Conshohocken, PA: ASTM
International. Available online at http://www.astm.org./Standards/D4814.htm
ASTM International. (2009e). Standard specification for diesel fuel oil, biodiesel blend (B6 to B20). West Conshohocken, PA: ASTM
International. Available online at http://astm.org/Standards/D7467.htm
Bondioli, P., Gasparoli, A., Lanzani, A., Fedeli, E., Veronese, S., and Sala, M. (1995). Storage stability of biodiesel. Journal of theAmerican Oil Chemists’ Society.72(6), 699-702.
Buckman, R. (2009). Boeing backs biofuels. Retrieved October 26, 2009, from Forbes.com at
http://www.forbes.com/2009/06/17/biofuels-biodiesel-boeing-intelligent-technology-biofuels.html
Efstathiou, J. and Credeur, M.J. (2009). Algae-powered jet proves biofuel in continental test (update 2). Retrieved October, 23, 2009 from
Bloomberg.com at http://www.bloomberg.com/apps/news?pid=20601081&sid=ayiWn9Z4EwIM
Frega, N., Mozzon, M. and Lercker, G. (1999). Effects of free fatty acids on oxidative stability of vegetable oil. Journal of the American
Oil Chemists’ Society. 76(3), 325-329.
Graboski, M.S. and McCormick, R.L. (1998). Combustion of fat and vegetable oil derived Fuels in diesel engines. Progress in Energy andCombustion Science. 24(2), 125-164.
Hess, J., Kenney, K., Wright, C., Perlack, R., and Turhollow, A. (2009). Corn stover availability for biomass conversion: Situation analysis.
Cellulose. 16(4), 599-619.
Hu, Q., Sommerfeld, M., Jarvis, E., Ghirardi, M., Posewitz, M., Seibert, M., and Darzins, A. Microalgal triacylglycerols as feedstocks forbiofuel production: Perspectives and advances. The Plant Journal. 54(4), 621-639.
Knothe, G. (2007). Some aspects of biodiesel oxidative stability. Fuel Processing Technology. 88(7), 669-677.
McCarthy, J.E. and Tiemann, M. (2000). MTBE in gasoline: Clean air and drinking water issues. Washington, D.C.: Congressional
Research Service, The Library of Congress. Available online at http://www.epa.gov/otaq/consumer/fuels/mtbe/crsrtc.pdf
Miyashita, K. and Takagi, T. (1986). Study on the oxidative rate and prooxidant activity of free fatty acids. Journal of the American Oil
Chemists’ Society. 63(10), 1380-1384.
Morrow, W.R., Griffin, W.M., and Matthews, H.S. (2006). Modeling switchgrass derived cellulosic ethanol distribution in the UnitedStates. Environmental Science & Technology. 40(9), 2877-2886.
Reyold, R. (2000). The current fuel ethanol industry transportation, marketing, distribution and technical considerations. Bremen, IN:
Downstream Alternatives, Inc. Available online at http://www.ethanolrfa.org/objects/documents/111/4788.pdf
Rieper-Kirchner, M. (1990). Macroalgal decomposition: Laboratory studies with particular regard to microorganisms and meiofauna.
Helgoland Marine Research. 44(3), 397-410.
Wakeley, H.L., Griffin, W.M., Hendrickson, C., and Matthews, H.S. (2008). Alternative transportation fuels: Distribution infrastructure forhydrogen and ethanol in Iowa. Journal of Infrastructure Systems. 14(3), 262-271.

72

8. Distribution and Utilization

9. Resources and Siting
The development and scale-up of algal biofuels
production, as with any biomass-based technology andindustry, needs to be analyzed from a site location, as
well as from a resource availability and use perspective.
Critical requirements—such as suitable land and climate,sustainable water resources, supplemental CO2 supply,and other nutrients—must be appropriately aligned interms of their geo-location, characteristics, availability,
and affordability. To achieve success regarding bothtechnical and economic performance without adverse
environmental impacts, the siting and resource factors
must also be appropriately matched to the required growth
conditions of the particular algae species being cultivatedand the engineered growth systems being developed anddeployed. The sustainability and environmental impactsof national algae production capacity build-up andoperation over time will be important complementary
aspects of the siting and resources issues that will alsoneed careful consideration and analysis using tools
and methodologies discussed later in chapter 10.
This chapter provides an overview of the issues associatedwith site location and key resources for various microalgae
and macroalgae production approaches (Exhibit 9.1).
Further, an in-depth discussion is included on the potential
to couple land-based microalgae biomass production
with wastewater treatment and industrial sources ofconcentrated CO2, both of which influence siting decisions
for algal biofuel production. Integration with wastewater
treatment can play an additional important role in thesourcing of nutrients from both the input wastewaterand from possible nutrient recycling from residual
algal biomass. The status of algae-based wastewater
treatment and necessary technical improvements forco-producing algal biofuels are described. Similarly,
the challenges associated with coupling industrial
CO2 sources with algae production are outlined.

9.1 Resource Requirements forDifferent Cultivation Approaches
Photoautotrophic Microalgae Approach
Assessments of resource requirements and availability
for large-scale, land-based photoautotrophic microalgal
cultivation were conducted during the Aquatic Species
Program (Sheehan et al., 1998), focusing primarily on
the Southwest and southern tier of the United States(e.g., Maxwell et al., 1985; Lansford et al., 1990;
Feinberg et al., 1990). Sufficient land, water, andCO2 resources were identified at the time to suggestthat the production of billions of gallons of algal
biofuel could be supported if sufficiently high algae
productivities could be achieved affordably at scale.
Many of the findings of these earlier assessments still
apply today and the potential remains for biofuels
and other co-products derived from photoautotrophic
microalgae to significantly contribute to meeting U.S.
transportation fuel needs and displacing petroleum use.
Exhibit 9.2 provides a simple high-level overview ofthe major resource and environmental parameters thatpertain to the algae biofuels production inputs of climate,water, CO2, energy, nutrients, and land. These parameters
are of greatest importance to siting, facilities design,
production efficiency, and costs. For each parameter, avariety of conditions may be more or less cost-effective
for the siting and operation of algal biomass production.
Additional resources include materials, capital, labor,
and other inputs associated with facilities infrastructure
and conducting operations and maintenance.
In addition to coastal and inland photoautotrophic
microalgae production, off-shore marine environment
concepts are also being proposed. This scenario

Exhibit 9.1 Key resource issues for different algae systems
ALGAE PRODUCTION APPROACH

KEY RESOURCE REQUIREMENTS

Photoautotrophic microalgae production

Climate, water, CO2, other nutrients, requiredenergy inputs, and land

Heterotrophic microalgae production

Sourcing of suitable organic carbon feedstock, water, energy,
and other inputs required for siting and operating industrial
bioreactor-based algae production and post-processing to fuels
and other co-products

Photoautotrophic macroalgae production

Availability of suitable coastal and off-shore marine site locations
9. Resources and Siting73

Climate
CO2 Nutrients
Nutrient
RecycleLiquid andGasous Fuels
Algal
Production

Water

Processing
andConversion

HarvestingLand

Resources andEnviromental
Parameters

Climate

Water

Land

Insolation
Temperature
Evaporation
Severe Storms

Location
Supply/ Demand
Salinity
Allocation

TopograghyUse/ Cover
Ownership
Soils
Geologycan be represented by extension of Exhibit 9.2 toconceptually include the equivalence of land andculture facilities with off-shore areas and structures. A
similar conceptual extension holds for the applicationof Exhibit 9.2 to off-shore macroalgae production.

Heterotrophic Microalgae Approach
Heterotrophic microalgae biomass and metabolite
production is based on the use of organic carbon feedstockin the form of sugars or other relatively simple organic
compounds instead of photosynthesis. The algae arecultivated in the dark in closed industrial bioreactorsthat could potentially be established in many locations
throughout the country. Achieving affordable scale-up andsuccessful commercial expansion using the heterotrophic
approach relies on the cost-effective availability of organiccarbon feedstock—a resource that ultimately links back toa photosynthetic origin (Exhibit 9.3). Heterotrophic andphotoautotrophic approaches to microalgae production
have different siting and resource input implications
and thus present synergistic integration opportunities.
Heterotrophic production can be characterized as more of
an industrial operation with a significant upstream logistics
trail associated with the sourcing of the needed biomassderived input feedstocks, whereas photoautotrophic
production, in terms of cultivation and harvesting, is moreakin to agriculture and serves as the point of origin for thebiomass feedstock supply for the downstream value chain.
Resource issues for the heterotrophic approach are morelargely associated with the upstream supply of organiccarbon feedstock derived from commodity crops, selected
74

Secondary
Products

9. Resources and Siting

Exhibit 9.2 Key siting and resource
elements for algae biofuel production(Adapted from Maxwell et al., 1985)

organic carbon-rich waste streams, and lignocellulosic
biomass, thereby sharing many of the same feedstock
supply issues with first- and second-generation biofuels.
Use of sugars from cane, beets, other sugar crops, andfrom the hydrolysis of starch grain crops can, aftersufficient scale-up of production and demand, lead to the
problem of linking biofuel production with competing
food and feed markets. The preferred source of sugars
and other appropriate organic carbon feedstocks for
greatest sustainable scale-up potential and avoidance ofadverse food/feed market impacts would be based on
the use of carbon-rich waste streams and the successful
deconstruction of lignocellulosic materials. The latterhas the greatest feedstock scale-up potential and is being
pursued and reported elsewhere through bioenergy
programs under DOE and Department of Agriculture(USDA; e.g., Perlack et al., 2005; DOE, 2006a). This
includes siting and resource issues that are closely
coupled with the production, availability, supply logistics,
and pretreatment of lignocellulosic biomass feedstockthat is expected to be capable of national scale-up to
over one billion tons annually (Perlack et al., 2005).

Photoautotrophic Macroalgae Approach
Options for siting macroalgae (also known as seaweed
or kelp) biomass production include offshore farms,
near-shore coastal farms, and land-based ponds. The
merits of each should be carefully evaluated, taking into
consideration factors such as the scale of farms required
to meet production needs, cost and availability of space

Synergistic ProjectIntergration Opportunities
Ligno-Cellulosic
Plant Material

Ligno-Cellulosic
Deconstruction& Seperation

Autotrophic
algae production- open ponds- closed PBRs
- hybrid mix

CO2
Water,
N, P, K,
other

Low-Density Algal
Biomass Harvesting

CO2 Sourceess- power plants- other industrial
Nutrient-Rich
Water Treatment- muni WWT- ag CAFO- lake, rivers
or Other
Non-Fresh Waters

LigninDewatering
CHP
High-Density Algal
Biomass FHarvesting

Sugars and Other
Organic Carbon
Feedstock

Extraction &Seperation

Biomass
Residue
Heterotropic algae
production inclosed bioreactors

and nutrients, environmental impacts, and competition
with other uses. The co-siting of macroalgal farms withother structures such as windfarms (Buck et al., 2004)
has also been proposed as a way of leveraging othertechnologies to facilitate the cultivation of macroalgae.
Based on the scale of macroalgae cultivation practices
currently being used to meet non-fuel product demand(annual global production of about 1.4 million dry
metric tonnes for food products), the level of production
would need to be greatly expanded for biofuels.
A major challenge lies in finding and developing newenvironments and cultivation approaches that will support
production of macroalgae at the larger scales and lower
costs needed to supply the biofuels market. Additional
research, technology development, and favorable regulatory
framework for coastal and offshore environment use could
help enable cultivation at scales to meet production goals.

9.2 Resources Overview
ClimateSunlight and Temperature Needs
Various climate elements affect photoautotrophic algae

Oil Feedstock

Fuels
Co-Products

Exhibit 9.3 High-levelillustration of heterotrophic
and photoautotrophic
approaches to microalgal
biomass and biofuels
production

production, particularly in the case of land-based
microalgae production. As illustrated in Exhibit 9.4, key
factors include solar radiation, temperature, precipitation,
evaporation, and severe weather. Closed photobioreactors
are less sensitive to climate variability than open ponds
due to the more controlled environment that closed
systems can provide. Temperature and availability ofsunlight, both seasonally and annually, will most directly
affect productivity, whereas precipitation, evaporation,and severe weather will affect water supply and water
quality in open systems. Heterotrophic algae production
in closed industrial bioreactor systems utilize maturebioreactor technology that can provide relatively clean
and protected environmental control needed to optimize
growth conditions for higher biomass density cultures.
Heterotrophic algal cultures can be one to two orders ofmagnitude higher in biomass density than possible with
open photoautotrophic systems that typically achieve no
more than about 1 gram per liter culture density. From aresource use perspective, the heterotrophic approach can
reduce both water and energy-use intensity in the algae
production operation. Closed heterotrophic bioreactor
systems are decoupled from the variable ambient
outdoor climate, weather conditions, and day/night lightand temperature cycles. This is done at the expense of

9. Resources and Siting75

high-cost systems, controls, and enclosures requiring
energy input for environmental control. For the case ofoffshore marine macroalgae production, the ocean or sea
environment provides a buffer that moderates temperature
variation, with the major climate element affecting algal
growth being the availability of sunlight. Storm and ocean
dynamics affecting waves, currents, and marine nutrienttransport cause additional impacts on productivity.
Equally important for photoautotrophic microalgae growthwith both open and closed cultivation systems is theavailability of abundant sunlight. A significant portionof the United States is suitable for algae production
from the standpoint of having adequate solar radiation(with parts of Hawaii, California, Arizona, New Mexico,
Texas, and Florida being most promising). The more
northern latitude states, including Minnesota, Wisconsin,
Michigan, and the New England states, would havevery low productivity in the winter months. Growth ofalgae is technically feasible in many parts of the UnitedStates, but the availability of adequate sunlight and thesuitability of climate and temperature are key siting andresource factors that will determine economic feasibility.
Preferred Geographic Regions for Algae Production
Exhibit 9.4 presents some simple GIS-based scoping
conducted by Sandia National Laboratories. The goal
was to provide a preliminary high-level assessment
identifying preferred regions of the United States forphotoautotrophic microalgae production based on
the application of selected filter criteria on annual
average climate conditions, the availability of nonfresh water, and the availability of concentrated sourcesof CO2. The climate criteria used to narrow down thegeographical regions were: annual average cumulative
sun hours ≥ 2800, annual average daily temperature≥ 55°F, and annual average freeze-free days ≥ 200.
It was recognized from the outset that the correlationof these annual average climate criteria with whatmight actually be achieved with annual average algae
productivity in large-scale deployed systems could
only be taken as a gross indicator. Within that context,
however, the results are suggestive and consistent withthe more recent assessment by Pacific Northwest National
Laboratory (PNNL) using higher GIS resolution andmore information-rich climate and meteorological data.
Projections of annual average algae biomass production
from the PNNL study show clear patterns relating climate
to total biomass growth, with the higher growth regions
having gross qualitative similarity to Exhibit 9.4 and thesouthern tier states showing greatest productivity potential
based on the modeling assumptions used. In Exhibit 9.4(a), the lack of attractiveness of the Gulf Coast region
from southeast Texas to northwest Florida is attributed
to the lower annual average solar insolation available,
whereas PNNL study suggests projected productivities inthis region could be relatively high. This is likely due tomore moderate annual average temperatures despite lower
solar insolation. These results should be considered simply
indicative at this point rather than predictive, but suggest
preference for lower latitude, i.e., lower elevation sites.
Additional factors could conceivably overcome whatmight otherwise appear to be uneconomical site andresource conditions for algae production. This could
include situations where co-location of inland microalgae
production at higher latitudes might be possible with

Exhibit 9.4 Rough scoping assessment of preferred site locations for outdoor algae productiona) Regions with annual average climate conditions meeting
selected criteria: ≥ 2800 hour annual sunshine, annual
average temperature ≥ 55˚ F, and ≥ 200 freeze-free days

76

9. Resources and Sitingb) Fossil-fired power plant sources of CO2 within 20 miles ofmunicipal wastewater facilities in the preferred climate
regionindustrial operations capable of providing excess heat andpower for cost-effective environmental control of the algae
cultivation. This would, however, require a more refined
analysis for systems that would likely be closed and highly
integrated with co-located industries providing synergistic
opportunities for utilizing waste heat and energy. Suchanalyses should include assessment of the monthly orseasonal solar radiation and ambient temperature ranges;
it should also establish minimum economically feasible
operational requirement values for heating in the winterand, for closed reactors, cooling in the summer.
Seasonal Considerations
Various species of microalgae have potential for biofuel
feedstock production and are capable of growing undera wide range of temperatures. High annual production
for a given species grown photoautotrophically outdoors,
however, will require that suitable climatic conditions
exist for a major part of the year (Maxwell et al., 1985).
Therefore, a critical climate issue for both open and closed
photobioreactor systems is the length of economically
viable growing season(s) for the particular strains of algae
available for productive cultivation. For outdoor ponds,
the conventional crop analogy for this is the length of time
between the last killing frost in the spring and the firstkilling frost in the fall. For closed photobioreactors, theconventional crop analog is the greenhouse and the limitingenergy and cost needed to maintain internal temperature
throughout the seasons. Availability and rotation ofdifferent algal species capable of good productivity incold season and hot season conditions, respectively, would
provide greater flexibility and could extend otherwise
limited periods of commercially viable algae production.
The primary geographical location factors for determining
length of growing season are latitude and elevation,
which have major influence on the hours and intensityof available sunlight per day and the daily and seasonaltemperature variations. Areas with relatively long growing
seasons (for example, 240 days or more of adequate solar
insolation and average daily temperatures above the lower
threshold needed for economically viable growth) are
the lower elevation regions of the lower latitude statesof Hawaii, Florida, and parts of Louisiana, Georgia,
Texas, New Mexico, Arizona, and California. Other local
climate and weather conditions will also have influence.
Thorough analysis (preferably on a state-by-state basis)
with detailed data is needed to assess areas most suitable
for algae production based on this climate factor. Discovery
and development of algae species capable of increased
productivity under wider ranges of light and temperature
conditions can also potentially lead to increased annual
average productivities in more geographically diverse

locations. It is encouraging that researchers today
are not only concerned with finding algae with highbiomass productivity and oil content yield, but also withalgae that grow well under severe climate conditions,particularly extremes in temperature, both high and low.
Water Requirements
Precipitation affects water availability (both surface
and groundwater) at a given location within a given
watershed region. Areas with higher annual average
precipitation (more than 40 inches), represented by specificregions of Hawaii, the Northwest, and the Southeast,
are desirable for algae production from the standpointof long-term availability and sustainability of watersupply. Evaporation, discussed later in this section, isclosely coupled with climate and will increase waterrequirements for an open algae growth system. Evaporativeloss can be a critical factor to consider when choosing
locations for open pond production. Evaporation is aless important concern for selecting locations of closed
photobioreactors, although evaporative cooling is often
considered as a means to reduce culture temperature.
The southwestern states (California, Arizona, and New
Mexico) and Hawaii have the highest evaporation rates
in the United States, with more than 60 inches annually.
A thorough evaluation of evaporative water loss isneeded to assess water requirements, implications forsustainable production scale-up, and overall economics.
Evaporative water loss is discussed in a later subsection.
Severe Weather Events and Elements
Severe weather events, such as heavy rain and flooding,hail storms, dust storms, tornadoes, and hurricanes poseserious concerns in the inland regions of the central states,
Southwest, Southeast, and coastal areas. These weather
events can contaminate an open system environment orcause physical damage to both open and closed systems,
and need to be taken into account when looking at
prospects for algae production in both inland and coastal
regions of the United States. Offshore marine algae
production will be subject to severe weather impacts
in the form of wind, waves, and currents that can cause
disruption or damage to physical structures and operations.
The marine environment can also be highly corrosive
to materials and usually demands both the use of higher
quality and more costly materials and greater maintenance.

Water
General Water Balance and Management Needs
One of the major benefits of growing algae is that, unlike
most terrestrial agriculture, algal culture can potentially
utilize non-fresh water sources having few competing

9. Resources and Siting77

uses, such as saline and brackish ground water, or “coproduced water” from oil, natural gas, and coal-bed
methane wells (Reynolds, 2003; USGS, 2002). However,for open pond systems in more arid environments withhigh rates of evaporation, salinity and water chemistry
will change with evaporative water loss, thereby changing
the culture conditions. This will require periodic blowdown of ponds after salinity build-up, periodic additionof non-saline make-up water to dilute the salinity buildup, the application of desalination treatment to control
salinity build-up, or highly adaptive algae that can thrive
under widely varying conditions. Open algal ponds may
have to periodically be drained and re-filled, or staged as acascading sequence of increasingly saline ponds each withdifferent dominant algae species and growth conditions.

The relatively flat national water withdrawal trend overthe past 25 years, following the more than doubling ofwater demand over the 30 years prior to that, reflects
the fact that fresh water sources in the Untied States areapproaching full allocation. Growing demand for limited
fresh water supplies in support of development andpopulation increase has thus far been offset by increased
conservation and by the increased re-use of wastewater.
Many of the nations’ fresh ground water aquifers are underincreasing stress, and the future expansion of fresh watersupplies for non-agricultural use must increasingly comefrom the desalination of saline or brackish water sources
and from the treatment and reuse of wastewater, all ofwhich have increasing energy demand implications (DOE,
2006b; Hightower et al., 2008; Kenny et al., 2009).

Implementing water desalination would impose additional
capital, energy, and operational costs. Disposal of highsalt content effluent or solid byproducts, from ponddrainage and replacement, or from desalination operations,can also become an environmental problem for inland
locations. Some salt byproducts may have commercial
value, depending on the chemistry. Water balance andmanagement, along with associated salt build-up andmanagement issues, from both a resource perspective
and an algal cultivation perspective, are important areas
for future research, modeling, and field assessment.

The stress on fresh water supplies in the United States is
not restricted to the more arid western half of the country,
but is also becoming a local and regional concern atvarious locations throughout the eastern half of the country,
where a growing number of counties are experiencing
net fresh water withdrawals that exceed the sustainablesupply from precipitation (DOE, 2006b; Hightower et al.,2008; ). Climate change is also recognized as a factor that
could have major effect on all sectors of water resources
supply and management in the future (USGS, 2009).

Analysis of U.S. Water Supply and Management

Water use and consumption for algae-based biofuels will
depend on the cultivation approach (photoautotrophic/
heterotrophic), with water use in upstream organiccarbon feedstock production needing to be part of theheterotrophic assessment. Water use will also depend on
the type of growth systems used for photoautotrophic
microalgae (open vs. closed vs. hybrid combination),whether evaporative cooling is used for closed systems,
and the site-specific details of climate, solar insolation,
and weather conditions (cloud cover, wind, humidity,etc.). Also a complicating factor for evaporative water
loss in open systems will be the degree of salinity of thewater used for cultivation and the local latitude, elevation,
ambient temperature variations, solar insolation, humidity,
and wind conditions (Al-Shammiri, 2002; Hutchison etal., 1978; Kokya et al., 2008; Mao, 1999; Oroud, 1995).
A significant source of water demand with inland algae
production operations could be for the replacement of watercontinuously lost to evaporation from open cultivation
systems. Whether or not this is a problem for sustainable
algal industry scale-up will depend on the geographic
location, climate conditions, and locally available water
resources. This will be of greatest impact and concern inwater-sparse locations, which also tend to be in the morearid and higher solar resource regions like the Southwest.
A rough upper bound estimate of evaporative water loss

Total combined fresh and saline water withdrawals in the
United States as of the year 2005 were estimated at 410,000
million gallons per day (Mgal/d), or 460,000 acre-feetper year (Kenny et al., 2009). Saline water (seawater andbrackish coastal water) withdrawals were about 15% of
the total. Almost all saline water, about 95%, is used by
the thermoelectric-power industry in the coastal states
to cool electricity-generating equipment. In 2005, nearly
one-half of the total U.S. withdrawals (201,000 Mgal/d)were for thermoelectric-power generation, representing
41% of all freshwater, 61% of all surface water, and 95%
of all saline-water withdrawals in 2005. Withdrawals
for irrigation of crops and other lands totaled 128,000
Mgal/d and were the second-largest category of wateruse. Irrigation withdrawals represented 31% of all water
withdrawals, and 37% of all freshwater withdrawals(Kenny et al., 2009). At the national scale, total combined
fresh and saline water withdrawals more than doubled
from about 180 billion gallons per day in 1950 to over 400
billion gallons per day in 1980. Total withdrawals since
the mid-1980s have remained relatively flat at slightly
over 400 billion gallons per day, with the majority (85%)
being fresh (Hutson et al., 2004; Kenny et al., 2009).

78

9. Resources and Siting

Scoping Out Water Requirements for Algae Production

with open systems was done as part of a hypotheticalscale-up scenario study in preparation for the National
Algae Roadmap Workshop, held in December 2008.
The notional scale-up scenarios and assumptions madeare discussed later in this chapter (see Exhibit 9.7).

co-produced water. Additional analysis, experimental
investigation, and field trials at larger scales of operation areneeded to understand how best to leverage these resources.

The evaporative loss estimates from the notional scenarios
provide an indication of the potential magnitude of theissue, and were based on simply applying fresh water
open horizontal pan evaporation data (Farnsworth etal., 1982a and 1982b; Shuttleworth, 1993; Woolhiser
et al., 1984) to large area scale-up of algae cultivation
with open systems. Extrapolations based on fresh waterpan evaporation data will be worst-case and will likely
be an over-estimate of what can be expected under
actual operating conditions in the field. Open bodies ofbrackish and saline water will usually experience lessevaporative loss than fresh water, as noted earlier.

When considering the water resources needed for the
future development and expansion of algal biofuel
production, the use of non-fresh water sources will need
to be emphasized in the face of the growing competitionand demands on limited sustainable fresh water supplies(DOE, 2006b; NAS, 2007; Hightower et al., 2008).
From a resource use standpoint, integrating algae
production with wastewater treatment, discussed
later in this chapter, has the potential benefits ofproductively using non-fresh wastewater resources
for renewable fuels, putting less additional demand on
limited fresh water supplies, reducing eutrophicationof natural water bodies, and recycling nutrients.

The evaporation estimates suggest that water loss on theorder of several tens of gallons of water per kilogramof dry weight biomass produced, or several hundreds ofgallons of water per gallon of algal biofuel produced,
could be a consequence of open system operationin the more arid and sunny regions of the country.
The most optimistic production scenario was for thesouthwestern United States, which assumed annual
average algal biomass and oil productivities of nearly
31 g/m2 per day with 50% dry weight oil content. If less
optimistic productivities are assumed, the estimatedevaporative water loss intensities will be greater.
Evaporative water loss associated with algae cultivation
can be significantly reduced if closed systems are used.
Evaluation of water use for the overall value chain fromalgal cultivation through harvesting and post-processing
into fuels and other products will also be important.
Along the way, additional water will be used andconsumed, and may well also be saved, reclaimed, andrecycled, depending on systems and process specifics.
Water must be considered a key element of life cycle
analysis for algal biofuels, as with other forms of
bioenergy (NAS, 2007; Gerbens-Leenes et al., 2009).
In summary, water utilization for algal biomass anddownstream production of biofuels, both in terms ofoverall input supply needs and consumption, warrants
closer attention and assessment to better understand andrefine water resource requirements. Water requirements
information will not be well characterized until larger scale
systems are implemented, monitored, and evaluated under arange of site locations and conditions. There is considerable
untapped potential for utilizing brackish, saline, andDeveloping and Mapping Water Resources for
Algae Production

The unique ability of many species of algae to grow in
non-fresh water over a range of salinities means that, in
addition to coastal and possible off-shore areas, other inlandparts of the country can be targeted for algae production
where brackish or saline groundwater supplies may beboth ample and unused or underutilized. Unfortunately,
quantitative information remains limited on U.S. brackish
and saline groundwater resources in terms of their extent,water quality and chemistry, and sustainable withdrawal
capacity. An improved knowledge base is needed to better
define the spatial distribution, depth, quantity, physical andchemical characteristics, and sustainable withdrawal rates
for these non-fresh ground water resources, and to predict
the effects of their extraction on the environment (Alley,
2003; Dennehy, 2004). Saline groundwater resources,
particularly deeper aquifers that are largely unregulated
by state engineers and water authorities, are also of
increasing interest and potential competition for access asa source of water for treatment and use to meet commercial
and residential development needs in high growth ratewater-sparse regions like the Southwest (Clark, 2009).
Depth to groundwater is pertinent to the economics ofresource development. Along with geological data, depth
information determines the cost of drilling and operating(including energy input requirements for pumping) a
well in a given location (Maxwell et al., 1985). Suitableaquifers located closer to the surface and nearer to thecultivation site would provide a more cost-effective sourceof water for algae production than deeper sources locatedlonger distances from the cultivation site. The location,
depth, and chemical characterization of saline aquifers
in the United States are areas of investigation in needof greater investment. The maps of saline groundwater

9. Resources and Siting79

resources are based on incomplete data that was largely
developed by the USGS prior to the mid-1960s (Feth,
1965; Dennehy, 2004). More detailed and up-to-date
information is needed to improve our understandingof this resource in support of algae production siting
analyses (Dennehy, 2004; NATCARB, 2008b). Produced
water from petroleum, natural gas, and coal bed methane
wells is another closely related and underutilized water
resource that can range in quality from nearly freshto hyper-saline (Reynolds 2003; USGS, 2002).
The geographical location, spatial extent, depth, potential
yield, recharge rate, sustainability of supply, and quality(chemical components and characteristics) are important
information for assessing non-fresh groundwater aquifer
resource availability and suitability for economic uses
(Shannon, 2006), including algae production. A limited
amount of this information is available for major
aquifers. However, if these aquifers are spread overlarge geographic areas, detailed analysis is difficultand often lacking. Data on small, local aquifers may beavailable through state agencies and private engineering
companies, but a significant effort will still be needed tolocate, identify, collect, and analyze this information.

Carbon Dioxide
The Carbon Capture Opportunity in Algae Production
Efficient algae production requires enriched sources of CO2
since the rate of supply from the atmosphere is limited bydiffusion rates through the surface resistance of the waterin the cultivation system. Flue gas, such as from fossilfuel-fired power plants, would be a good source of CO2.
Algae production could provide excellent opportunities forthe utilization of fossil carbon emissions and complement
subsurface sequestration. However, algae production does
not actually sequester fossil carbon, but rather provides
carbon capture and reuse in the form of fuels and otherproducts derived from the algae biomass. Any greenhousegas abatement credits would come from the substitutionof renewable fuels and other co-products that displace or
reduce fossil fuel consumption. In addition, at some large
scale of algae production, parasitic losses from flue gas
treatment, transport, and distribution could require moreenergy input than the output energy displacement value
represented by the algae biofuels and other co-products.
Likely Stationary CO2 Emission Sources
Major stationary CO2 emission sources that could
potentially be used for algae production are shown in
Exhibit 9.5. The sources shown (NATCARB, 2008)
represent over half of the more than 6 billion metric tonsof CO2 emitted annually in the United States (EPA, 2009;80

9. Resources and Siting

EIA, 2008 and 2009). Power generation alone (mainly
using coal) represents over 40% of the total, or more than
2 billion metric tons per year (EIA, 2008 and 2009).
Barriers to Viable CO2 Capture and Utilization
The degree to which stationary CO2 emissions canbe captured and used affordably for algae production
will be limited by the operational logistics andefficiencies, and the availability of land and water
for algae cultivation scale-up within reasonablegeographic proximity of stationary sources.
As an example, a recent analysis suggests that for algae
production to fully utilize the CO2 in the flue gas emitted
from a 50-MWe semi-base load natural-gas-fired power
plant would require about 2,200 acres of algae cultivation
area (Brune et al., 2009). The CO2 generated by the power
plant can only be effectively used by the algae during
the photosynthetically active sunlight hours. As a result,the greenhouse gas emissions offset will be limited to an
estimated 20% to 30% of the total power plant emissions
due to CO2 off-gassing during non-sunlight hours and theunavoidable parasitic losses of algae production (Bruneet al., 2009). Larger coal-fired base-load generators thattypically output a steady 1,000 to 2500 MWe of power
would each require many tens of thousands of acres ofalgae production and large volumes of water to provide asimilar effective offset of 20% to 30% of the CO2 emitted.
The distance for pumping flue gas to algae cultivation
systems will become a limiting factor that requires
capture and concentration of CO2 from the flue gas forlonger distance transport and distribution. Applications
separating CO2 in large industrial plants, including natural
gas treatment plants and ammonia production facilities,
are already in operation today and under consideration forpossible broader use for carbon capture and storage (CCS)
in response to climate change (Rubin, 2005; Campbell
et al., 2008). Photoautotrophic algae will only utilize
CO2 during daylight hours when photosynthesis is active.
The rate of effective CO2 uptake will also vary withthe algae species, biomass growth rate, and details of
growth system and incident light conditions. Therefore,
the requirements for CO2 supply to enhance algae
production, and the matching of CO2 source availability
with algal cultivation facilities, is not a simple issue. In
addition, it will be necessary to provide a CO2 source thatis suitably free of materials potentially toxic to algae.
An inventory of stationary industrial CO2 sources in
the more promising regions of the country, including
characterization of the CO2 emissions stream (e.g.,
rates and quantities of CO2 produced, content, anddescription of substances toxic to algal growth) and the
local availability and distance to suitable land for algae

production, is needed for making refined assessments foralgae production siting and CO2 sourcing. One outcomeof a hypothetical algae production scale-up scenario is
the limited quantity of CO2 that would likely be available
from stationary industrial point sources (e.g., Exhibit
9.5) within practical transport distances of suitable algae
production sites in a given geographical region. Thiscan be expected to constrain the extent to which algal
biofuels production can be affordably scaled up within
any given region unless other factors drive the investment
in expanding the nation’s CO2 pipeline infrastructure.

Land
Factors for Evaluating Land for Algal Production
Land availability will be important for algae production
because either open or closed systems will require
relatively large areas for implementation, as is expectedwith any photosynthesis-based biomass feedstock. Evenat levels of photoautotrophic microalgae biomass and oil
productivity that would stretch the limits of an aggressive
R&D program (e.g., target annual average biomass
production of 30 to 60 g/m2 per day with 30% to 50%
neutral lipid content on a dry weight basis), such systems
would require in the range of roughly 800 to 2600 acres ofalgae culture surface area to produce 10 million gallons ofoil feedstock, as will be discussed further in chapter 10.

Land availability is influenced by various physical, social,economic, legal, and political factors, as illustrated in
Exhibit 9.6. Hundreds of millions of acres of relatively lowproductivity, lower-value land exists in the United States(USDA, 2006 and 2009), including pasture, grassland,
and relatively barren desert land. For a realistic appraisalof land for algae production (i.e., land that would be bothsuitable and potentially available for siting algae production
facilities), several characteristics need to be considered.
Physical characteristics, such as topography and soil, could
limit the land available for open pond algae farming. Soils,
and particularly their porosity and permeability
characteristics, affect the construction costs and designof open systems by virtue of the need for pond lining or
sealing. Topography would be a limiting factor for thesesystems because the installation of large shallow ponds
requires relatively flat terrain. Areas with more than 5%
slope could well be eliminated from consideration due tothe high cost that would be required for site
preparation and leveling.
Land ownership information provides valuable insights
on which policies and stakeholders could affect project
development. Publicly and privately owned lands are
subject to variable use, lease, and purchase requirements.
For example, much of the land in the West is government
owned, which means that environmental assessments and/

Exhibit 9.5 Major stationary CO2 sources in the United States (NATCARB, 2008a)
CATEGORY

CO2 EMISSIONS(Million Metric Ton/Year)

NUMBER OF SOURCESAg Processing

6.3

140

Cement Plants

86.3

112

Electricity Generation

2,702.5

3,002

Ethanol Plants

41.3

163

Fertilizer

7.0

13

Industrial

141.9

665

Other

3.6

53

Petroleum and Natural
Gas Processing

90.2

475

Refineries/Chemical

196.9

173

Total

3,276.1

4,796

9. Resources and Siting81

or environmental impact statements could be required
as part of the approval process. Indian reservations also
comprise a significant portion of this land. Land ownershipcan represent and impose political and regulatory
constraints on land availability (Maxwell et al., 1985).
Further, as with any form of biomass, algae productivity
will be constrained by the available energy density
in sunlight and the relatively low efficiencies ofphotosynthetic processes coupled with other systems losses.
The result will be theoretical and practical upper limits on
the amount of biomass growth that can be achieved per unitof illuminated surface (Weyer et al., 2009). Contributing to
productivity limits per unit of illuminated surface area is thefact that algal cells nearest the illuminated surface absorb
the light and shade their neighbors farther from the lightsource. Optimizing light utilization in algae production
systems includes the challenge of managing dissipative
energy losses that occur when incident photons that cannot
otherwise be effectively captured and used by the algaein photosynthesis are instead converted to thermal (heat)
energy in the culture media and surrounding cultivation
system structures. Depending on the algae strain andculture system approach used, the dissipative heat loading
can be a benefit in moderating culture temperatures andimproving productivity under colder ambient conditions,or can lead to overheating and loss of productivity
during hotter ambient conditions. Loss mechanisms that

Typography

All
Land
Parcels82

9. Resources and Siting

Land Availability Constraints
Land use and land value affect land affordability. By
reviewing the more recent economic analyses for algae
biomass and projected oil production, the cost of land isoften not considered or is relatively small compared to othercapital cost. Land that is highly desirable for development
and other set-asides for publically beneficial reasons may

Land
Ownership

Physically
Suitable
Land

Water andClimateResources

restrict the fraction of incident photon flux that can beeffectively used to drive photosynthesis ultimately places
practical upper limits on the biomass productivity.
Despite the practical upper limits that will naturally exist
for algae productivity, the potential remains for highalgae biomass production relative to more conventional
crops, (chapter 10). It must be stressed that “potential”
algal biomass and bio-oil production projections atcommercial scale currently remain hypothetical rather
than real, given that large-scale algae biomass production
intended for bioenergy feedstock does not yet exist.
Relatively large-scale commercial algae production
with open ponds for high-value products can serve as abaseline reference, but currently reflect lower biomass
productivities in the range of 10 - 20 g/m2 per day. Thisis significantly lower than the more optimistic target
projections for biofuel feedstock of 30 - 60 g/m2 per day.
However, such systems have not been optimized forhigher-volume, lower-value production with algal strainsdeveloped and improved over time to be more suitable andproductive for biofuel feedstock rather than those used
for today’s high-value algae biomass product markets.

Current
Land Value

Politically
Available
Land

Legislation
and Regualtions

Systems
Engineering

Affordable
Land

Current
Land Use

Available
Land

Enviromental
Restrictions

Exhibit 9.6 Factors and process steps for evaluating and constraining
the available and appropriately suitable land for algae production(Adapted from Maxwell et al., 1985 )not be seen as suitable for algae production. The same
applies to land highly suited for higher-value agriculturaluse. Beyond economics, this also avoids the perception
and potential conflict of food and feed production versus
fuel. Sensitive environmental or cultural land constraints
will also reduce the overall land availability (Maxwell
et al., 1985). Examples of this type of constraint include
parks, monuments, wildlife areas, archaeological sites,
and other historical sites. On the other hand, some land
cover characteristics could present excellent opportunities
for algae farming. Land cover categories such as barren
and scrubland cover a large portion of the West and may
provide an area free from other food-based agriculture
where algae growth systems could be sited (Maxwell et al.,1985). The availability and sustainability of water supplies
in the West will also be a key consideration, as noted earlier.

9.4 Integration with Water
Treatment Facilities
Inevitably, wastewater treatment and recycling
must be incorporated with algae biofuel production.
The main connections of algae production andwastewater treatment are the following:

POTENTIAL BENEFITS OF ALGAE PRODUCTION
WITH WASTEWATER TREATMENT
Although algae-based wastewater treatment requires
many times more land area than mechanical treatment
technologies, in suitable climates, algae-based
treatment has the following advantages:• Early opportunity to develop large-scalealgae production infrastructure• Development of skilled algae production workforce• Potential for nutrient recycling at algae
biomass production facilities• Wastewater treatment revenue that
offsets algae production costs• Lower capital and O&M costs thanconventional wastewater treatment• Lower energy intensity than conventional
wastewater treatment (a greenhouse gas benefit)• Potential to be integrated with power plantor other CO2-emitting industry operations• Potential to treat agricultural drainage
and eutrophic water bodies• Treatment technology is needed to recycle
nutrients and water from algae biofuel processing
residuals for use in algae production.
• Imported wastewater provides nutrients and water tomake-up inevitable losses. The imported wastewater
would be treated as part of the algae production.
• Algae-based wastewater treatment provides a needed
service.
• Algae-based wastewater treatment can be
deployed in the near-term and provides workforce
training and experience in large-scale algae
cultivation that would translate to future dedicatedalgae feedstock production facilities.
For large-scale algae biofuel production, nutrients fromwastewater (municipal and agricultural) would be captured
by algae and then recycled from the oil extraction residuals
for additional rounds of algae production. Nutrient
recycling would be needed since wastewater flows in
the United States are insufficient to support large-scalealgae production on the basis of a single use of nutrients.
Inevitable nutrients losses during algae production
and processing could be made up with wastewater
nutrients, which can also help supplement and off-set
the cost of commercial fertilizers for algae production.
Supply and cost of nutrients (nitrogen, phosphorus, andpotassium) be a key issue for achieving affordable andsustainable scale-up of algae biofuels production.

Wastewater Treatment andRecycling Applications
Municipal wastewater treatment facilities and agricultural
dairy and feedlot operations located throughout theUnited States, particularly in the eastern half of thecountry, represent potential co-location sites for algae
operations where nutrient-rich wastewater could be
used for algae production, and the algae production canhelp provide nutrient removal service in the wastewater
treatment. Two main types of algae production facility areenvisioned: dedicated facilities, with the main purpose of
biomass production, and wastewater treatment facilities,
which produce algal biomass as a consequence of thewastewater treatment. Dedicated biomass production
facilities will also require wastewater treatment andnutrient recycling. A subset of wastewater treatment
facilities consist of evaporation facilities, which areused to dispose of wastewater or brines. The roles ofthese facility types in the development of an algae
biofuels industry are discussed in this subsection.
Algae can be useful in the treatment of waters polluted withorganic matter, excess nutrients (e.g., nitrogen, phosphorus,and potassium), metals, synthetic organic compounds,
9. Resources and Siting83and potentially endocrine disrupting compounds (Oswald,
1988; Woertz et al., 2009; Aksu, 1998; Borde et al.,2002). High rates of algae production lead to high rates
of nutrient removal and wastewater treatment. Thus, theobjectives of biofuel feedstock production and wastewater
treatment are aligned, at least in terms of maximizing
biomass production. Maintenance of lipid-rich strains,or manipulation of culture conditions to promote lipid
production, have yet to be demonstrated consistently
for ponds, including wastewater treatment ponds.
Algae-based treatment facilities are typically less expensive
to build and to operate than conventional mechanicaltreatment facilities. For example, high-productivity algae
ponds have a total cost that is about 70% less than activatedsludge, which is the leading water treatment technology
used in the United States (Downing et al., 2002). This
cost savings, coupled with the tremendous need for
expanded and improved wastewater treatment in the UnitedStates (EPA, 2008) and throughout the world, provides apractical opportunity to install algae production facilities
in conjunction with wastewater treatment. The majorclasses of wastewaters to be treated are municipal, organic
industrial (e.g., food processing), organic agricultural(e.g., confined animal facilities), and eutrophic waters
with low organic content but high nutrient content (e.g.,
agricultural drainage, lakes, and rivers). Despite a seeming
abundance of wastewater and waste nutrients, recycling of
nutrients and carbon at algae production facilities will beneeded if algae are to make a substantial contribution tonational biofuel production. Even with internal recycling,
importation of wastes and/or wastewater will still beneeded in dedicated algae biomass production facilities
to make up for nutrient losses (Brune et al., 2009).

Algae Production Techniques for
Wastewater Treatment Plants
Integration of algae production with wastewater treatment
is illustrated schematically in Exhibit 9.7. Existingalgae-based treatment facilities use relatively deep
ponds (1-6 m). The great depths contribute to low algae
productivity, but high productivity is not crucial to thetreatment goals of these facilities (removal of organic
matter and pathogens only). Ponds for more advanced
treatment, including nutrient removal, need high algae
productivities (as does biofuels feedstock production).
These highly productive systems use shallow reactors,
either high rate ponds (~30 cm) or algal turf scrubbers(~1 cm). Closed photobioreactors are not emphasizedin this wastewater treatment discussion since they arelikely to be economical only when also producing
high-value products (>$100/kg biomass), which isunlikely when wastewater contaminants are present.
84

9. Resources and Siting

As with other algae production systems, harvesting is a
crucial step in wastewater treatment systems. The standard
method is chemical addition to achieve coagulation andflocculation, followed by algae separation in dissolved
air flotation units or sedimentation clarifiers. The costof chemical addition ($0.10 - $0.17 per m3 treated)(Maglion, 2008) is high for biofuel production. Nonchemical flocculation processes (bioflocculation andautoflocculation) are far less costly, but research isneeded to improve the reliability of these processes (asdiscussed in chapter 4). As noted above, the major types
of wastewaters available for combined algae production
and water treatment are those contaminated with organic
matter and nutrients (e.g., municipal and industrial sources)
and wastewaters mainly contaminated with inorganic
nutrients (e.g., agricultural drainage, rivers, and lakes).
Treatment of Organic Wastewaters for Algae Production
Organic-rich wastewaters usually also contain nutrients,
requiring two types of treatment. Algae are similar toplants in that they both produce oxygen and assimilate
nutrients. These reactions are also the best-known
mechanisms of wastewater treatment by algae. The
dissolved oxygen algae release is used by treatment bacteria
to oxidize waste organic matter (Exhibit 9.7). The abilityof algae to assimilate dissolved nutrients down to trace
concentrations is useful in wastewater treatment, if thenutrient-rich algae are then also removed from the water.
Less well-known are the ability of algal systems to provide
natural disinfection and remove trace contaminants.
Disinfection is promoted via the production of oxygen
radicals in the presence of sunlight, dissolved oxygen,and naturally occurring organic catalysts (Sinton et al.,2002, Kohn et al., 2007). Heavy metals may be removed
by adsorption to algal cells, which will be a benefit aslong as the resulting metals concentrations in the algae
biomass are not excessive or inhibitive for later use in
the processing of fuel and other co-products. Finally, theinteraction of algae and bacteria in wastewater cultures
leads to degradation of a wide variety of syntheticorganic compounds such as phenol and acetonitrile(Borde et al., 2003, Muñoz et al., 2005). The
removal of trace contaminants (e.g., endocrine disrupting
compounds such as human hormones and antibiotics
from animal facilities) is an area in need of study.
Mechanical treatment technologies typically holdthe wastewater for less than 12 hours, whereas pond
technologies hold the wastewater for at least several days
and in an environment similar to many natural receiving
waters. The bioaccumulation of trace contaminants inalgae that would occur in the receiving waters, eventuallyharming higher organisms, might be prevented to a

Exhibit 9.7 Integration of algae production with wastewater treatment for nutrient removal and biomass production:

Sun

CO2
Reclaimed

Waste
Water

Water

Algae

CO2
N
P

CO2
N
P

O2

Organics

Biomass

Bacteriaa) Basic principles of operation;

High Rate
Pond

ClarifierRaw Sewage
SludgeDigestor

ClarifierTreatedEffluent

CO2

Generator
kWh

Food
Production
OptionAlgae Biomass
InputsLiquid Biofuel

To Fertilizer

Products
Reclaimed Water
Fuels Fertilizerb) Simplified conceptual system block diagram

9. Resources and Siting85

great extend by pond treatment followed by algae
harvesting. The processing of the algal biomass for fueland other co-products would presumably destroy andneutralize the contaminants, but further investigation isneeded to confirm this. However, any heavy metals
contaminating the algal biomass likely would remain in
the waste from biofuel processing, potentially increasing
the cost of waste disposal or recycling. For all biofuel
feedstocks, routes of such contamination should bestudied and preventative measures developed.
Treatment of Inorganic Wastewaters for Algae Production
In addition to the ability of algae systems to treat
organic-rich wastewaters, their ability to treat highnutrient, low-organic content wastewaters will expand
the opportunities for algae production systems.
Agricultural drainage and eutrophic water bodies(e.g., Salton Sea, Calif.) are examples of such waters(Benemann et al., 2002). Treatment of nutrient-richwaters is likely to occur in more rural settings thantreatment of municipal wastewaters, potentially leading
to greater land availability and savings in land costs.
For algae-based treatment of low-organic content
wastewaters, CO2 addition or slow atmosphericabsorption is essential since inorganic carbon generationfrom decomposition of organic matter would not besignificant. Treatment of agricultural drainage withalgal turf scrubbers without CO2-addition and highrate ponds with CO2 addition has been demonstrated in
California’s Central Valley and elsewhere (Craggs etal., 1996; Mulbry et al., 2008; Lundquist et al., 2004).
High rate ponds might be used as components ofevaporation systems needed to dispose of blow-down
or other wastewater. The high rate ponds could create
an algal product while performing the service of water
evaporation. Evaporation ponds are currently used todispose of agricultural drainage, oil field produced
water, mine drainage, etc. As with any evaporation pond
system, hazards to wildlife from toxic compounds (e.g.,selenium, chromium) must be carefully evaluated.

Main Research Needs for Algae
Production with Wastewater
Successful use of high rate ponds specifically for
nutrient removal/recycling requires resolutionof several issues, as follows:• Large-scale (3-5 acre) demonstration of CO2enhanced high rate ponds for nutrient removal• Determine CO2 biofixation efficiency
86

9. Resources and Siting• Determine growth model parameters• Develop algae grazer control strategies• Develop reliable low-cost algae harvesting
techniques, such as bioflocculation,
autoflocculation, micro-screening, etc.
• Demonstrate recycling of biofuel processing
wastes for algae production• Determine the cost savings and greenhouse gas(GHG) emissions avoidance benefits compared toconventional wastewater treatment technologies.

9.5 Co-location of Algal
Cultivation Facilities with
CO2-Emitting Industries
This section includes findings from discussions held at the
National Algal Roadmap Workshop break-out sessions,and additional input sought from managers at major
electric utilities through later meetings and conference
calls. These follow-on efforts were coordinated with theElectric Power Research Institute (EPRI), and included
several large municipal electric utilities. The topics
of discussion included the value proposition, desired
outcomes, integration opportunities and challenges, market
drivers, technical and market challenges, constraints
on large-scale development, co-products, and potential
opportunities for the federal government. Findings fromthese interviews and conference calls were integrated
with the Workshop inputs in developing this section.
It is important to point out that amongst the numerous
barriers to co-location of algal cultivation facilities withindustrial CO2 sources identified at the Workshop andsubsequent discussions with electric utilities, an overriding
theme was that electric utilities primarily view algae
cultivation as a means of CO2 capture as opposed to amethod for producing biofuels and co-products. Thus,
electric utilities may need to partner with algae cultivation/technology companies and fuel refiners/distributers withvery different business models and goals for algae
production in order for this type of co-location to be
widely commercialized. Furthermore, research efforts
and policy evaluations would likely need to focus on
both carbon capture and the production of biofuels andco-products to overcome barriers (technical, regulatory
and economic) for algae facilities that are co-locatedwith electric utilities and other industrial CO2 sources.

The Opportunity in Co-Locatingwith CO2-Emitting Sources

Since photoautotropic algae growth requires CO2, andproductivity can be enhanced by supplementing thelimited CO2 available from the atmosphere, concentrated
sources flue gas from fossil-fuel burning power plants
and other CO2-emitting industrial sources can bebeneficially used in algae production. Resulting costs forCO2 will be site-specific and dependent on methods of
capture, conditioning, and distance of transport to algae
cultivation sites. Costs are expected to be lower than forpure commercially supplied CO2, but economic viability
must be determined case by case. Offset of fossil fuelconsumption by algae biofuel and other co-products must
be done with approaches that provide a net GHG emissions
reduction. Co-location of algal cultivation with industrial
CO2 sources is a promising area for further research.
While the information in this section focuses on fossilfired power plants, it is also relevant to other CO2-intensive
industries (e.g., cement manufacturing, fossil fuelextraction/refining, fermentation-based industries, somegeothermal power production, etc.). The emissions frommany of these facilities have higher CO2 concentrations
compared to power plant flue gas, which typically ranges
from about 5% to about 15%, depending on the type ofplant and fuel used. This higher concentration would affectthe sizing and operations of algae production facilities—
an aspect that could be incorporated into engineeringmodels described in more detail in the Systems andTechno-Economic Assessment section of this report.
An important policy question to consider is the valueof CO2 absorption by algae in any carbon-credit orcap and trade framework, in that the carbon will be
re-released to the atmosphere when algal-derived
fuels are combusted. While algae biofuels can be
expected to result in a net reduction of overall GHG
emissions, the process of capturing flue-gas CO2 to maketransportation fuels may not rigorously be consideredcarbon sequestration. The regulatory implicationsof this will need to be addressed before utilities
and fuel companies are likely to widely adopt algal
cultivation co-located with industrial CO2 sources.
A variety of stationary industrial sources of CO2
are distributed throughout the United States. The
quantitative breakdown, introduced earlier in Exhibit
9.5, shows that fossil-fired power plants represent
the majority of CO2 emissions from stationary
sources. A number of large coal-burning power plants
distributed across the southern tier states provide
ample sources for algal growth on a large scale.

ADVANTAGES OF CO-LOCATION OF
ALGAE PRODUCTION WITH STATIONARY
INDUSTRIAL CO2 SOURCES• Abundant quantities of concentrated CO2 available
from stationary industrial sources can supplement
low concentration CO2 from the atmosphere.
• Excess heat or power may be available to provide
heating or cooling for improved thermal
management of algae cultivation systems – thiswill allow developing algal cultivation facilities
under a broader range of geographic and climate
conditions on or near a year-round basis.
• Excess wastewater or cooling water may beavailable, found often in proximity of power
plants – overcoming a primary resource challenge
for algae cultivation at scale, while providing
beneficial re-use of cooling water and wastewater.
• Potential carbon credit for utilities. This will
require establishing a U.S. policy on carbon
absorption and re-use as transportationfuel in lieu of permanent sequestration.

Coal-fired power plants may be a convenient source ofCO2 for algae production, but from an emissions control
perspective, construction of algae systems at natural
gas-fired power plants may be a better investment. The
reason is that coal-fired power plants have higher CO2
emissions per unit energy produced than natural gas-fired
power plants. Thus, using algae to capture the maximum
amount of CO2 emissions from coal-fired plants would
require proportionally larger algae production systems
per unit energy produced and higher costs per unit energy
produced. However, coal-fired plant flue gas typicallyhas about a factor of two greater CO2 concentration(10 - 15%) than natural gas plants (5 - 6%), which canbring some advantage in terms of efficiency of capture,transport, and delivery of CO2 from the power plant tothe algae cultivation site. Also, gas-fired power plantsthat operate as peaking plants rather than base-load
generators will have intermittent operation that would
introduce intermittency in the supply of CO2 for algae
growth. The impact on algae production would dependon the phasing of the intermittency with respect to the
daylight hours when photosynthesis is active. Gas-fired
baseload generators would not be intermittent, but, aswith baseload coal-fired plants, would also emit CO2
during periods of darkness when it cannot be utilized by
the algae through photosynthesis. During those times,
the CO2 would be emitted to the atmosphere if not
captured and sequestered by other means (Rubin, 2005).
9. Resources and Siting87Barriers to Co-Location of Algae
Production with Stationary Industrial
CO2 Sources• Need for nutrient sources: While stationary industrial
sources of concentrated CO2 can potentially provide
ample carbon for photosynthesis-driven algal growth,in most cases there will not be a complementary
nutrient (N, P, K) supply. Therefore nutrients must be
brought in from other sources, or in some cases algal
cultivation could be co-located with both stationary
CO2 sources and nutrient sources such as wastewater
treatment facilities and agricultural waste streams.
• Unclear regulatory framework for carbon-capture
credits: Until there are regulations in place thatquantify carbon credits from algal growth facilities,
the uncertainty may pose a barrier for wide commercial
adoption of the technology.
• Land availability: Suitable and affordable vacant land
may not be available adjacent to or near major
power plants• Emissions from ponds are at ground level: Regulatory
requirements from power plants and other stationary
sources are governed by the Clean Air Act, andare based upon point-source emissions from highelevations. The use of flue gas to cultivate algae will
involve non-point source emissions at ground level.
• Capital costs and operational costs: There exists aneed to evaluate capital costs and parasitic operational
losses (and costs) for infrastructure and power required
to capture and deliver industrial CO2 to ponds andgrow/harvest algae. These costs and losses must be
minimized and compared to other approaches for thecapture and sequestration or reuse of carbon. Current
estimates are that approximately 20% - 30% of apower plant’s greenhouse gas emissions can be offset
by algae biofuel and protein production (Brune et al.,2009). Although often referred to as a “free” resource,
the capture and delivery of concentrated CO2 fromstationary industrial sources as a supplement to enhanceand optimize algae production will not be “free”.
• Too much CO2 near plants for realistic absorption:
Large power plants release too much CO2 tobe absorbed by algal ponds at a realistic scale
likely to be possible near the power plantfacility. The same generally holds true for otherstationary industrial sources of CO2 (cement
plants, ethanol plants, etc.). Also, CO2 is only
absorbed during periods when sunlight is available
and photosynthesis is active in the algae.

88

9. Resources and Siting• Maintaining cultivation facilities during utility outages
and through seasonal changes in algal growth rates:
Detailed models will be needed to develop and evaluate
approaches for managing the variable nature of both
CO2 emissions and algal growth rates/CO2 uptake.

• Resistance from electric utilities: Electric utilities are
not in the fuels business and regulated public utility
commissions will be constrained in entering the fuelproduction arena. Their fundamental objective will be
to capture CO2 as opposed to producing biofuels andco-products. Thus, mechanisms to encourage partnering
between utilities and algae/fuel companies will be
required, and new business models will be needed tocommercialize this approach.

Directions for Research and Development
Several areas for research, as well as policy-development
efforts, will be required for commercialization ofalgal cultivation facilities co-located with industrial
CO2 sources and/or wastewater treatment facilities.
The following directions have been identified:• Develop computer models of algae production
facilities that will aid the following:▪▪ Rapid and consistent engineering design▪▪ Techno-economic analyses▪▪ Life Cycle Analysis and GHG abatement analysis▪▪ National inventory of potential production sites▪▪ Evaluation of economies of scale vs. advantagesof decentralized production consideringparasitic losses of CO2 transport, etc.
▪▪ Evaluation of temperature control (power
plant cooling and algae pond heating)▪▪ Development of efficient test-bed facilities• Establish national algae biomass production test-beds
to conduct research at the pilot scale (3 - 10 acres).
The test-beds would ideally be located at power plants,
wastewater treatment facilities, ethanol plants or otherCO2 emitting industry facilities, and agriculturaldrainage/water body restoration sites that also represent
a range geographical locations, solar resource, andclimate conditions. This effort could involve a
consortium of R&D organizations, universities, algal
cultivation companies, algal technology companies,
refiners, distributors, and other participants coordinatedat the national level. Specific test-bed R&D
topics relevant to power and wastewater utilities
include:▪▪ Technology evaluation at larger scales▪▪ Determination of algae production facility model
parameters▪▪ Flue gas or other industrial source CO2 supply
logistics, costs, and absorption/biofixation efficiency
and algal biomass productivity given seasonal anddiel variations in photosynthesis and various
water chemistries▪▪ Control of algal biomass quality (ratios of lipids:
proteins: carbohydrates and C:N:P)▪▪ Methods of nutrient and water recycling within
production facilities; salinity and blowdown
management.
▪▪ Algal biomass handling, storage, and processing
prior to fuel extraction; flocculation harvesting;pathogen safety▪▪ Beneficial management of residuals for soil carbon
development, crop fertilization, etc.
▪▪ Development of algal strains and their cultivation
techniques▪▪ Investigate the safety of ground-level flue gas
emissions from ponds including plume modelingand regulatory analysis▪▪ Effects of various flue gases on algae production
and co-product quality▪▪ Scrubbing of flue gas for NOx, SOx, etc.
▪▪ Power plant cooling with treated wastewater in
conjunction with algae production• Evaluate policies that would encourage partnering
between public utilities/other industrial CO2 sources
and algal cultivation/technology companies
and refiners/distributors.
• Develop and train the future algae production/algae
biomass processing workforce at the national test-bed
and other sites. Develop university training programs.

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from waste stabilization pond effluent in fresh and saline waters. Applied Environmental Microbiology. 68(3),1122-1131.
Solley, W.B., Pierce, R.R., and Perlman, H.A., (1998). Estimated use of water in the United States in 1995. (U.S. Geological Survey
Circular 1200). Available online at: http://water.usgs.gov/watuse/pdf1995/html/
U.S. Department of Agriculture (USDA). (2006). Major uses of land in the United States, 2002. (Economic Information Bulletin Number
14). USDA Economic Research Service.
U.S. Department of Agriculture (USDA). (2009). Land use, value, and management: Major uses of land. USDA Economic ResearchService On-Line Briefing Room Available online at: http://www.ers.usda.gov/Briefing/LandUse/majorlandusechapter.htm
U.S. Geological Survey. (2002). Produced Water Quality Map of US http://energy.cr.usgs.gov/prov/prodwat/dictionary.htm
U.S. Geological Survey. (2009). Climate change and water resources management: A federal perspective. (USGS Circular 1331). US
Geological Survey.
Weyer, K. M., Bush, D. R., Darzins, A., & Willson, B. D. (2009.). Theoretical Maximum Algal Oil Production. BioEnergy Research, 1–10.
Woertz, I.C., Lundquist, T.J., Feffer, A.S., and Nelson, Y.M. (2009). Lipid productivity of algae grown during treatment of dairy andmunicipal wastewaters. Journal of Environmental Engineering. 135(11), 1115-1122.
Woolhiser, D.A. and Wallace, D.E. (1984). Mapping average daily pan evaporation. Journal of Irrigation and Drainage Engineering.
110(2), 246-250.
Wu, M., Mintz, M., Wang, M. and Arora, S. (2009). Consumptive water use in the production of ethanol and petroleum gasoline. (ANL/
ESD/09-1). Argonne National Laboratory.

92

9. Resources and Siting10. Systems and Techno-Economic Analysis
Successful development of an algae-based biofuels andco-products industry requires the optimum combination oftechnical innovations in systems and processes, coupledwith economic feasibility in the practical implementationand integrated scale-up for commercial production
and marketing. Enabling successful advancement andcommercialization of the still relatively immaturefield of algal biofuels also requires the confidence andengagement of key public and private stakeholders sothey can make necessary investments over time to reduce
technical risks and overcome challenges to developing
an algal biofuels industry. Toward this end, objective
and quantitative modeling and analyses of systems andprocesses are needed that span different enterprise levels
across the overall algae-to-biofuels supply chain. Suchanalyses can provide improved understanding and insightto help guide successful industry development within thereal-world context of technical, environmental, political,
infrastructural, and market conditions and constraints.

challenges along each of these pathways, as discussed
throughout the Roadmap. Systems modeling and analyses
applied across this space and done at different levels of
precision and granularity, ranging from individual unit
operations to an integrated enterprise, to an overall regionalor national resource and supply chain assessment, canprovide informed guidance for targeting investments inselect technologies, processes, systems, and deployment
approaches. It can also help track performance andprogress (technical, economic, and environmental) criticalto meeting performance objectives and reaching goals for
successful commercialization, as illustrated in Exhibit 10.2.
In short, techno-economic modeling and analysis canserve a range of purposes and goals that include:• Assess technical performance and cost/benefit
tradeoffs among different technologies, systems,
and processes, e.g., comparative yield andenergy balance for different pathways• Assess economic impact of R&D strategies andinvestments, e.g., comparative cost per
gallon of biofuel for different pathways

10.1 Objectives ofTechno-Economic Analysis
Given the numerous potential approaches and pathways
available for algae biofuels and co-products (as illustratedin Exhibit 10.1), significant investment is expected to berequired to overcome the various technical and economic

Exhibit 10.1 High level illustration of various approaches and pathways to developing algae-derived biofuelsand co-products

ALGAE
Unicellular
Microalgae

Cyanobacteria

Open Terrestrial
Systems
Phototrophic

HybridSystems

Mixotrophic

Hydrocarbons& Alcohols*

LipidsMulticellular
Macroalgae

Closed Terrestrial
Systems

Phototrophic

Heterotrophic

Carbohydrates

Proteins

Species
Selection &BiologyOpen Offshore
Systems

Cultivation
System:Phototrophic- Harvesting- Dewatering- Fractionation- Separation

Consolidated
Biomass

Intermediate
Constituents

Anaerobic
Digestion

Conversion
Processes

Co-Products

End Use Fuels& Products* Biologically produced in-situ by the organism

Biochemical
Conversion
Renewable
Hydrocarbons

Thermochemical
Conversion

Biodiesel

Alcohols

DirectSynthesis

Biogas

10. Systems and Techno-Economic Analysis

93• Assess environmental impact of R&D strategies
and investments, e.g., comparative net greenhousegas (GHG) emissions per gallon of biofuel fordifferent pathways

10.2 TEA Scope and Methods
Exhibit 10.3 illustrates at a high level the essential
elements of techno-economic modeling and analysis.
These intersecting elements present a broad systems
perspective that integrates the interdependent scienceand engineering aspects specific to developing algae
biofuels, keeping environmental, economic, andpolicy aspects in view to provide critical insightand information needed for decision-support.

• Assess consequences and constraints of alternative
pathways for algal feedstock, biofuels, and coproducts industry build-up, e.g., land, water, CO2,
other nutrients, energy, and infrastructure.
• Inform R&D and business development investment
decisions• Inform policy decisions and explore “what if”
scenarios

Techno-economic assessment for algae biofuels ishighly interdisciplinary and will range from GIS-based
resource and siting assessment, to engineering modelingof systems and processes at the unit operations level, tointerdependency analyses of the entire supply chain. Exhibit
10.4 illustrates a broad systems perspective of issues andapproaches for the overall algae biofuels supply chain fromsiting and resources to product end-use. The categories
shown follow the process steps in the algal biofuel supply
chain sequence. Such summarization of key areas to beaddressed to enable algal biofuel production provides
guidance for the scope of content that should be integrated
into systems techno-economic modeling and analysis.

• Provide insight and actionable information needed
to successfully guide technical advancement,
integrated system scale-up, and commercialization
DOE’s Biomass Program employs a wide range ofanalytical tools, data, and methodologies to support
decision-making, guide research, and demonstrateprogress toward goals. In conjunction with the Algae
Roadmap, Biomass Program’s strategic and portfolio
analysis efforts are expanding to include algae withtechno-economic modeling and analysis (TEA), life cycle
assessment (LCA), and geographic information system(GIS) based resource assessments.

Exhibit 10.2 Systems and Techno-Economic Modeling and Analysis as a decision-support tool
It can track and assess performance, and evaluate investment cost/benefit/risk tradeoffs to inform both technical and programmatic decisions

S&T, Systems & Processes Areas

Cost, Performance, and Risk Metrics

Biofuel Conversion
Extraction & Fractionation
Harvesting & Dewatering
Algae Science & Biomass Production

Stage-I Advances

Systems Infrastructure & Integration
Uncertainty Range

Cost & Risk
Reductions

Stage-II Advances

Perfomance
Improvements

Commercialization Threshold
Cost & Risk
Reductions
Perfomance
Improvements

T0 (current status)

T1

Roadmap Timeframe Multi-Stage R&D,
Demonstration, Commercializtion, Deployment
94

10. Systems and Techno-Economic Analysis

T2 (e.g., 5-15 years)

Energy & Fuel Economics;

Algal Biomass & Biofuel
Production Systems,

Energy-Water-Environment
Interdepencies;

Process Engineering& Other Sciences

Carbon Emissions &CapturePolicy Analysis
Exhibit 10.3 Techno-Economic Modeling andAnalysis addresses interdependent issues

The scope of TEA will ideally include the capability toapply and integrate detailed process engineering andphysics-based modeling at the unit operations levelwith multi-scale and multi-path systems modeling andcomparative tradeoff assessment. This can include
geospatial (GIS-based) data collection, analysis andvisualization, systems and processes optimization,and dynamic interdependency analyses of the overall
supply chain at a local, regional, national, or global
scale. A major environmental impact element will
be life cycle analysis (LCA) to assess GHG impacts
and other resource use footprint (e.g., water).
The overall goal is to capitalize on the power and insightavailable through application of well developed computermodeling and analysis tools combined with disparate
database information that exists or can be developed.
For example, a process-based algae growth model that
accurately reflects and integrates the dynamic behavior of
the key biological processes with the engineered growthsystem and its time-dependent physical and chemical
conditions (including local time-varying climate andweather) can not only provide more detailed input tothe techno-economical performance analysis of algae
cultivation, but can also reveal opportunities for improved
system and process design and operation. Since thecharacteristics of the biological system at the microscopic
algae cell level affect the performance of the engineered
cultivation system and processes at a higher integrated

level, which in turn must function within climate andweather conditions that vary with geographical location,
the approach needs to be both multi-level and multi-scale.
An algae biofuels and co-products supply chain will be acomplex interdependent system with numerous alternative
pathways and functional elements and feedbacks at various
spatial and temporal scales and resolutions, as suggested
in Exhibit 10.5. System and process simulation andoptimization under a system engineering framework can
prove very beneficial for system design and operation. For
example, optimizing conditions that produce the highest
neutral lipid content of the algal biomass under a range
of design conditions, when bio-oil feedstock productionis the primary pathway and objective, may not lead to thehighest overall biomass or lipid productivity. Similarly,
achieving the most affordable and sustainable productionof algal feedstock, in terms of resource use intensity
and cost per unit of end-use biofuel produced under aspecific set of scenario conditions, may not result from thepursuit of the algal oil production pathway altogether.
Sensitivity analyses and global system optimizationand comparative tradeoff assessments across a range ofapproaches and conditions are among the critical modelingand analysis needs. Meeting such needs requires a flexible
modeling and analysis framework and suite of tools thatcan specifically address the broad scope and multiple
pathways spanned by an algae biofuels supply chain
system. Geospatial GIS-based data integration and analysis
10. Systems and Techno-Economic Analysis

95

Exhibit 10.4 Scoping the content for Systems Techno-Economic Modeling and Analysis: Key topic areas and issues for the overall algal
biofuels supply chain
SYSTEMS INTEGRATION & INTERDEPENDENCIES

Sitting & Inputs

Geolocation/
elevation
Land characteristics
Climate/Weather
Solar Insolation
Water Souces/
Issuses- brackish- wastewater- produced- desalination
concentration-marine- fresh- losses, re-use- salt build-up
CO2 Sources- power plants- cement plants- fermentation/
otherChemical/Materials
Energy/PowerInfrastructure

Algal Biology
S&T

Cultivation
Systems

Harvesting &Dewatering

Extraction &Fractionation

Species Selection& Matching toGrowth Conditions

Open Ponds- lined- unlined- raceway- wastewater
treatment
Closed PBRs
- horizontal tube
- vertical tube
- vertical planar- otherHybrid System
Combinations- covered ponds- pond/PBR mix

Filtering
Flocculation/
Settling
Airlift Flocculation
Centriuge
Drying
Biological Assist- brine shrimp- fishOther

Extract Processes- Solvent- Acoustic- Electromagnetic- OtherSeperation/
Fractionation- Membrane- Distillation- Centrifuge- OtherIntermediate
Products- TAG Oil
- Other Lipids▪ Polar▪ Neutral- Carbohydrates- Proteins- Other
Compounds- Water
Direct secretionof EtOH orhydrocarbon fuelprecursors into
growth medium,avoiding Harvest &Dewatering steps

Characterization
Performance
Strain Improvement
Biomass Growth& Oil Conditions
Photoautotrophic
organism operation
Heterotrophic
organism operation
Algae Pathogens,
Predators, andMitigations

Heterotrophic- Industrial
Bioreactors- Wastewater
Facilities
Operations,Monitoring &Maintenanceis also key to siting and resource assessment and the design,
analysis and optimization of facilities location and supply
chain logistics (from algae cultivation through end-use
fuels and products biorefining, transport, and distribution).
Algal biofuels remain an emerging field at a relatively
immature stage of development. As a result, data for
detailed unit operations and process analyses for different
technical approaches for algae cultivation, harvesting, andpost-processing into fuels and other co-products is currently
sparse and uncertain. Selected modeling and analysis
approaches can be used to effectively accommodate such

96

10. Systems and Techno-Economic Analysis

Conversion
Processes Biofuels
Co-Products,& Services
Conversion Processes- Biochemical- Thermochemical- Digestion- Hydrotreat/
RefineFuels- Biodiesel- Green diesel- Aviation- Gasoline-like- EtOH- Biogas/methane- Other
Co-Products- Feed- Fertilizer- Chemicals
Services- Carbon capture- Water treatment

Policy &Regulation

Taxes
Incentives
Permitting
Enviromental
Impact
Health & Safety
Algae Control& Regulation
Other

uncertainty in data while still capturing the underlying
dymanics of the overall system. Although quantitative
uncertainty will remain, the results can provide qualitative
system behavior and trends still useful in helping
guide technical, economic, and policy decisions. Morethorough analysis and modeling refinement, informedby field data expected to become available as largerscale pilot and demonstration projects are establishedand operated, will more clearly reveal the most criticalchallenges and guide investments and technical advances
needed to enable successful commercialization of
economical, scalable, and sustainable algal biofuels.

Policy & Regulation; Incentives & Barriers

Siting- Land (cost, location,tilt, geology, soil)- Solar Insolation- Temperatures- Climate/Weather

DesignFeedbacks

Algae- Species- Characteristics- Requirements- Performance- GMOsResources- CO2 / Flue Gas- Water- Nutrients (NPK)- Labor- Capital- Materials- Equipment- Primary Energy

Nutrient
Feedbacks

Broader
Environment& Economy

Carbohydrates

Cultivation

Biology
Feedbacks- Autotrophic- Heterotrophic- Open systems- Closed systems- Hybrid systems

Harvesting

Conditioningor Treatment

Dewatering&/or Drying

Water Capture& Re-Use

Conversion
Biofuels

Extraction& Seperation

Oil / Lipids

Proteins &Other

Conversion
Coproducts

Co-GenEnergyFeedbacks

Electric Power and Process Heat Generation

Capital Construction, Operations, Monitoring, Maintenance, Replacement
Market Externalities: Cost of Energy, Cost of Petroleum & Conventional Fuels,
Demand & Price for Co-Products vs. their alternatives, etc.
Exhibit 10.5 The dynamic coupling and interdependencies across the algal biofuels and co-products supply chain

10.3 Suggestions for TEA andLCA Approach (Workshop
Results and Discussion)
Preparation for the Algae Roadmap Workshop and thediscussion among participants during and after the event
identified the need to clearly define the scope and determine
the role that systems TEA and LCA can and should playin support of algal biofuels development. Also identified
was the need to adapt, develop, and utilize a range ofapproaches, scales, and levels of detail best suited toperform the necessary modeling and analyses based on
available and emerging information and data. Exhibit
10.6 illustrates various complementary modeling andanalysis approaches and techniques that come into play atdifferent levels within the broad systems scope presented.
Due to their more limited and immediate businessobjectives, individualized modeling and analysis efforts
by industry and technology development organizations
tend to focus on a technology or process, unit operation,
production plant, or enterprise level rather than broader
integrated systems modeling and analysis across the

supply chain. Details of systems’ and processes’ technicaland economic performance achieved by industry andother technology developers are also usually considered
proprietary, and therefore, unavailable for broader use andobjective assessment and validation. It was noted that there
is a need and role for both integrated systems modeling aswell as detailed engineering design and process modeling,
and that the two should be coupled. Workshop participants
generally agreed that modeling and analysis should be a
critical part of a national algae biofuels research programand industry development effort, similar to the modelingand analysis efforts underway by DOE in support of theother bioenergy and biofuels programs. It is also expectedthat the needs for coupled models of differing fidelity andscales will be defined in the early stages of the systems
modeling R&D effort and will evolve as time goes on.
Included in the Workshop discussions was the question of
how best to approach the multiple and disparate paths
and configurations of rapidly evolving systems andprocesses, as exemplified by Exhibit 10.7, that should
be considered in algae biofuels modeling and analysis
efforts. One approach with photoautotrophic microalgae
is modeling major cultivation system categories
10. Systems and Techno-Economic Analysis

97

Higher-Level Dynamic Meta-Systems Modeling (Integrated Analysis Framework)• Broad value-chain scope... from resources & sitting through production to end use• Algae biofuel and co-products industry scale-up potential, resource use, constraints & impacts- Integration with existing infrastructure- Required build-up of new infrastructure.. with time delays... with learning curves &improvement projections- Technical, economic, enviromental, and policy issues• Feedbacks and Multiple Sector Interdependencies... can link to other models & analyses

Process Flow Enginering Modeling• Mass & energy balance calculations(ASPEN+)• Process GHG footprint (LCA) assessment

Geographic Information System(GIS) Analysis and Visualization• Land resources (characteristics,
availability, etc.)• Water resources (fresh wastewater,other)• Climate/ Weather/ Temperature
Conditions• CO2 resources ( point source emitters,
pipelines)• Fuel processing, transport, storage
infrastructure• Other infrastructure and enviromental
features

Static CAPEX & OPEX Calculations• System and process equipment cost estimates- Vendor/ Supplier cost estimates• Engineering and construction cost estimates- Engineering & construction estimates fromindustry- ICARUS cost estimate software (or equivalent)• Operations & Maintenance cost estimates• Cost (& offsets) of co-product feedstock
production• Cost of biofuel production• Cost (& offsets) of co-products production• Carbon footprint cost accounting

Other LCA Modeling• GREET (Argonne National Lab)
• LEM (UC/ Davis)... Etc.

Exhibit 10.6 Multiple levels and complementary approaches available for Algal Biofuels Systems and Processes Techno-Economic Modeling,
GIS Analysis, and Life Cycle Analysis

of open pond, closed photobioreactors, or a hybrid
combination, and activating only those portions of thehybrid configuration model desired. Beyond this, how
to best conceptualize a model that spans the overall“beginning-to-end value chain” for algal biofuels
production with adequate resolution and detail is very
challenging and still emerging. The size of the “matrix”
of possibilities could quickly become unmanageable.
Developing numerous detailed models that are eachuniquely customized to a specific combination of systems
and processes and performance parameters is anotherapproach, and essentially represents what exists today withvarious groups doing ad-hoc modeling and assessment
specifically focused on their chosen approach andtechnologies (e.g., platform). The disadvantage of such a
distributed and narrowly focused approach is that it is often
done in isolation with limited or no consideration of other98

10. Systems and Techno-Economic Analysis

competing options and the broader scope of interdependentissues and tradeoffs that need to be addressed together tobetter inform technical, economic, and policy decisions
at the state, regional, and national level. Narrowly
focused and detailed technical and economic modelingand analysis is valuable and necessary for those doing
engineering design, development, and optimization of
specific technologies, processes and integrated systems
for commercialization. Flexibility and usefulness
could be increased to the extent that such modelingand analysis can be done using common standards,
definitions, and interface approaches, across an emerging“community of practice” for the algae biofuels industry.
Standardized interface requirements and definitions could
be established for system and process functional blocks thatwould enable the development of an open-source modelingand assessment platform with “plug & play” flexibility.

5.1 Physical(Thermo/Mechanical)
5.2 Electromagnetic
5.3 Chemical

M. Biodiesel

G. Fatty Acids

5.4 BY PASS

H. Triglycerides

C. Lipids
5.0 Extraction& Separation

D. Carbohydrates

N. Green diesel

6.1.2 Thermochemical

O. Aviation
P. Gasoline-like

6.2 Co-products
Conservation

F. Other
Metabolites

1.1.2 Cyanobacteria

6.1 Fuel
Conservation

6.1.3 Biochemical

E. Proteins
1.1.1 Microalgae

6.1.1 Chemical

Q. Biogas / Methane

I. FeedR. Ethanol

J. Fertilizer

1.0
Inputs

1.1.3 Macroalgae

R. Hydrogen

K. Chemicals
2.1 Closed system

1.1 Algae species
1.2 Land1.3 CO2

2.0
Cultivation

3.0 Harvesting

L. Materials

2.2 Open system
2.3 Hybrid systems

3.1 Flocculation& settling

2.4 Off-shore systems

3.2 Filtering
8. Dried Algal
biomass

3.3 Centrifuging

1.3 Water

2.5 Biological assist

Infrastructure& Markets

A. Wet algal or
biological assist
derivative biomass

3.4 BY PASS

1.5 Light or
Alt. Energy Source

3.5 Biological Assist
Harvesting (shrimp,
fish excrement, etc.)

4.1 Solar
4.0 Drying
4.2 Fuel - Field- Transport- Storage- Distribution- End Use

Exhibit 10.7 High-level multi-pathway algae biofuel process flow diagram for the algal biofuels and co-products supply chain

Much more detailed or custom models of individual
subsystem or process blocks could then be developed byvarious others in industry, universities, and national labs,
utilizing different techniques such as high performancephysics-based modeling (e.g., computational fluid dynamics
modeling of open raceway ponds or closed photobioreactor
cultivation systems) or process engineering models using
widely accepted and applied commercial process modelingtools like AspenPlusTM or customized spreadsheets.
Flexibility in being able to link custom subsystemor process models into an overall meta-systemmodeling and analysis framework would provide acapability that could be of significant value and benefit
to different stakeholder communities such as:• DOE & national labs doing R&D, assessment, andtracking of program investments• Other federal and state agencies (Department of
Defense, USDA, EPA, etc.)• Universities doing a wide range of technical/
economic/policy R&D and assessment• Industry developing and commercializing technologies,
systems, processes• Private investment / funding sources

Work currently underway on the Knowledge Discovery
Framework (KDF) by DOE’s Biomass Program ismoving in this direction (Getman, 2009), and represents
an example of a GIS-based information gatheringand analysis platform that can be productively used
and leveraged for algae biofuels development.

10.4 Systems Analysis
Overview
System analysis is foundational to designing a strategy
for algal biofuel deployment. A system is an aggregationof subsystems interacting such that the system is able todeliver an over-arching functionality. Exhibit 10.5 provides
a high-level illustration of the interdependent characterof the overall algae biofuels value chain that involves a
broad range of systems, processes, and other technicaland non-technical issues. To facilitate system-level
thinking during the Workshop, a process flow diagram wasdeveloped and presented at every breakout track discussion
to illustrate the intricate interdependencies of algal
biofuel production. Exhibit 10.7 is a revised adaptationof the flow diagram that shows a representative number
10. Systems and Techno-Economic Analysis

99

of multiple path process options available for every stepin the algal biofuel production chain, from algae growth
to fuel and co-product processing and end-use. Sub-levelprocesses that made up different thematic topic discussion
sessions in the Workshop are all inter-related. Collecting
and understanding key information from each node in theprocess becomes the primary task of the systems analysis.
Both Exhibit 10.5 and Exhibit 10.8 represent a large
number of permutations of potential pathways to algal
biofuel production, most of which are still immature andemerging. Many of the process steps will differ dependingon the product or co-product chosen, and others beyond
those selected for inclusion in the figures also exist or
will likely emerge. Though it may seem daunting toattempt to develop a comparative analysis based on somany process permutations, there is precedence for thissort of undertaking in DOE’s Hydrogen Analysis (H2A)
Project within the overall Hydrogen Program (DOE,2009). Established in 2003 in response to the Hydrogen
Fuel Initiative, H2A was designed to consider various
pathways toward a hydrogen economy, evaluate costs,
energy and environmental tradeoffs and set research
priorities and inform policy by sound analysis. The
options for hydrogen production include goal gasification,
nuclear energy, wind electrolysis, and organic moleculereforming. This program could serve as a guide for moving
forward with analysis of algal biofuel production.
Other chapters of this Roadmap point out the lackof availability of detailed information about thecharacteristics of algae themselves and the characteristics(energy requirements and costs) of the systems andprocesses that are shown in the process flow diagramof Exhibit 10.8. A substantial number of barriers are
enumerated and designated as goals to be achieved.
Systems analysis can help manage the complexity of
producing algal biofuels and co-products by quantifying
uncertainties, identifying and appropriately modelinginterdependencies and feedbacks, and comparing tradeoffs from various scenarios with regard to cost, risk,
technical performance, and environmental impacts.

Engineering Analyses and
GIS Assessments
Engineering analyses (technical and economic) at theunit operations level require the systematic calculationand tracking of mass and energy balances that include
evaluation of the thermodynamic, hydrodynamic,
biological, and chemical kinetics of the systems andprocesses used. Example engineering analysis tools
include AspenPlusTM and FLUENTTM, among others,
which require sufficient understanding and detailed100

10. Systems and Techno-Economic Analysis

technical information and data about the systems andprocesses involved to appropriately formulate and conduct
accurate analyses. This may also require couplingwith appropriate external data and driving functions
such as time-dependent solar insolation, temperature,and other local environmental conditions. Simpler andmore approximate preliminary spreadsheet analyses
are more appropriate as a first step, especially where
detailed process engineering data may be lacking.
An example of this type of analysis is presented in
Exhibit 10.8. Exhibit 10.8 represents a mass and energybalance systems level view of an algal biomass and algal
lipid cultivation and extraction system. Inputs to eachsystem component are shown, and each numbered node
represents a mass or energy balance calculation. The
value of this kind of systems mass and energy balance
assessment is that it can help assess the overall viabilityof a given algal biomass production system and showwhat steps in the process are most energy intensive, thus
highlighting areas for research and development. The
development of mass and energy based systems models
can help evaluate different proposed processes foroverall viability and examine the sensitivity of different
assumptions in individual processes to the overall system.
Geographic Information System (GIS) Visualization
and Analysis tools (referenced also in chapter 9)
are indispensible for algae production and supply
chain systems analysis due to their ability to performmapping and resource analysis spanning local, regional,
and national scales. Critical climatic and natural
resource data can be readily accessed, such as:•

Land and water resources(characteristics, availability, etc.)• Climatic characteristics (temperature,
precipitation, solar insolation, etc.)• Water evaporation loss (function of climate, etc.)• CO2 resources (point source emitters, pipelines)• Fuel processing, transport, storage infrastructure• Other infrastructure and environmental features
Several critical resource factors will impact large-scale,sustainable production of microalgae biomass. These
include climate and the adequate availability of water,
efficiency of water use, availability of suitable land,
and availability of supplemental CO2 and other nutrient(N, P, K) supplies. The impact that availability and costof these resource can have on algae biofuel production
scale-up was touched on earlier in chapter 9. The costand benefit tradeoffs of CO2 capture through biofixation
using photoautotrophic microalgae cultivation enhanced

by the addition of CO2 from industrial sources will affectthe economics of algal biofuel production. Potential
CO2 capture and utilization in algae biomass production
is discussed in more detail through a few selected
example calculations presented later in this chapter.
The economics of algae-based biofuels and co-products
will depend in large measure on the degree to which algae
feedstock production and downstream processing can be
integrated with existing infrastructure and markets. At thefront end of the supply chain, this will include the logistics
and costs of supplying inputs needed for algae production(suitable siting, sourcing, and transport of water, nutrients,
supplemental CO2, and energy). Midstream will be thelogistics of transport, storage, and biorefining into fuels andother co-products, followed downstream by the necessarytransport, storage, and distribution into the various end-use
fuel and co-product markets at the end of the suppy chain.
To the extent that operations can be effectively co-locatedor established within reasonable distances across the
supply chain, the economics can be expected to improve.
Producing biofuels that are highly compatible, or totally
fungible, with the existing hydrocarbon fuel handling,
distribution, and end-use infrastructure would result ineasier and more widespread market acceptance. The
same would apply to co-products and their potential
markets. These and related issues should be an integral
part of techno-economic modeling, analysis and LCA
for algae, with the appropriate models, tools, and data
sets developed and leveraged to provide the necessary
assessment capabilities to guide research, businessdevelopment, resource management, and policy decisions.
At the downstream end, the relative location andlogistical costs associated with fuel processing,transport, storage, and distribution infrastructure
could benefit from GIS analysis. This information, forexample, can help determine the practical upper limiton the size and the optimum site locations of biorefinery
facilities relative to upstream algae biomass production
and downstream fuel and co-product markets.
The combination of GIS resource assessment, including
geographic location attributes and time dependent climate
and weather data, with physics-based modeling ofcultivation systems and algae growth, can provide powerfulcapabilities for estimating performance and for improving
the technical design of systems and their operations fordifferent site conditions. Exhibit 10.9 is an example of theapplication of high-performance computational modelingtools and capabilities to an open raceway pond system that
includes an algae growth model driven by environmental(e.g., solar insolation, ambient temperature, nutrient
concentrations, etc.) forcing functions and boundary
conditions (James and Varun, in press). The possibilityof combining these types of spatial and physical data to
project possible algal production scenarios as a function ofgeography and climate is an interesting avenue of inquiry.
Currently, the data available to implement this type ofanalysis are thought to be preliminary and refinement
based on model improvement and validation with datafrom the operation and monitoring of larger scale algae
production systems under a range of site and climate
conditions with multiple species of algae could be useful.
Economic analysis tools for static capital expense(CAPEX ) and operational expense (OPEX) calculations
are also integral to system analysis as they reveal financial
investment or market incentives needed for algae biofuel
deployment. Some examples are:
• POLYSYS• ICARUS cost estimate software (or equivalent)• Equipment, Operation & Maintenance cost estimates• Discounted cash flow analysis• Cost (& offsets) of co-product feedstock production• Cost of biofuel production• Carbon footprint cost accounting

Exhibit 10.8 Notional baseline algae feedstock production system
H2O
& O2

Energy &Other Inputs

EnergyEnergyH2O

PhotoBioreactor&/ or Pond
SystemPrimary
Harvestinge.g.,
ChemicalFlocculation

Secondary
Harvestinge.g.,
Dissolved Air
Flotation

Primary
Dewatering
e.g.,
microfiltration& Centrifuge

SecondaryDewatering
e.g., Biomass
DryingNeutral Lipid
Extraction
e.g., Hexane
Solvent

Water
Capture &re-useEnergyResidues:

Potrential
Co-productsProteinPolar Lipid
Carbohydrate

Sunlight& Water

Microalgae
Air & CO2
Nutrients(N, P, K, etc.)

Facilities, Structures, andSystems Infrastructure, Land,
Materials, Equipment, Utilities,
Site Preparation

Solvent
RecycleSolvente.g., Hexane
Recovery

TAGs & Other
Neutral Lipid
Biofuel Feedstock

10. Systems and Techno-Economic Analysis

101Computational Fluid Dynamics Model of Algal Raceway Pond Using Modified EPA
and US Army Corps of Engineers Codes•

The Environmental Fluid Dynamics Code (EFDC) solves 3D Navier-Stokes
equations of open channel flow to model speed, temperature,and nutrient gradients• Solar insolation and other environmental, climate, and meteorologicalforcing functions• Includes algal biomass growth model• CE-QUAL couples nutrient kinetics and 22 independent variables(N, P, Si, O2…) to model growth rates.

Exhibit 10.9. Open raceway pond example of physics-based algae cultivation system modeling and anlaysis. Such analysis can enable both
performance prediction and pond system design optimization after appropriate refinement and validation with monitored field system data
(Adapted from James and Varun, in press)

Recent analysis suggests an upper theoretical limit on
the order of ~38,000 gal/ac-yr and perhaps a practicallimit on the order of ~4,350 - 5,700 gal/ac-yr, basedon the expected losses, photosynthetic efficiency, andother assumptions made in the analysis (which include
the availability of high solar insolation consistent withlower latitudes and/or high percentage of clear weather
conditions, 50% oil content, etc.) (Weyer et al., 2009).

Impact of Geographic Variability of
Inputs on Algal Biofuel Production Costs
The various inputs necessary for algal biofuel production
have been described earlier in this chaper and in otherchapters of the Roadmap. Certain elements, like cost of
power, water, and fertilizer, vary over the U.S. but thesevariations, though important for overall TE analysis, are
not unique to the development of algal biofuel technology.
There are, on the other hand, aspects of large scale
macroalgae and microalgae cultivation (autotrophic,
heterotrophic, and mixotrophic) for which geographicalvariation of resource availability will have major impacts
on cost of production and scale for commercial viability.
These aspects were discussed in some detail in
Chapter 9, but it is appropriate here to briefly notethe following:• The average annual insolation is generally thedominant and rate-limiting factor for autotrophic algal
productivity, and this factor varies widely across thecountry among inland, coastal, and offshore sites.
This variation will determine the spatial surface
102

10. Systems and Techno-Economic Analysis

area of cultivation systems needed to achieve a set
amount of product; it will affect the amount of CO2that can be captured; and it will affect the amountof culture that will need to be processed on a daily
basis. The daily, seasonal, and annual variation insolar insolation, as well as other climate-related
factors such as temperature and weather (cloud
cover, precipitation, wind, etc.) will also affect boththe productivity and reliability of production.
• Availability, cost, and sustainability of suitable watersupplies for algae production will be a key input factor
for inland cultivation, and will be heavily dependent
on geographical location and local conditions. Areasof the country with the highest solar resource best
suited for algae growth also tend to be more arid andsubject to more limited water supplies. Under largecommercial algae industry build-up scenarios, theamount of water required nationally could begin toapproach the same order of magnitude as large scale
agriculture, particularly with open systems subject toevaporative loss. Capture and re-use of non-fresh water,in particular, can potentially help fill this need, but will
be dependent on the geographical location, availability,
and affordable accessibility of such water sources.
• The supply, availability, and cost of organic carbon
feedstock needed as input for heterotrophic microalgae
production will play a major role in the commercial
viability and extent to which national production
capacity can expand using the heterotrophic approach.
Sugar from commodity crops and other organiccarbon materials from industrial or municipal waste
streams can provide bridge feedstock in the near-term, but major sustainable scale-up of national
production capacity will demand the use of sugars
and other suitable organic carbon source materials
derived originally from lignocellulosic biomass.
As with cellulosic ethanol, the logistics and costs
associated with producing, transporting, andappropriately processing lignocellulosic biomass
materials in the form of woody and herbaceous
energy crops, waste materials from agriculture
and forest industries, and municipal waste streams
will be location-dependent. The affordability ofgenerating organic carbon feedstock from suchmaterials will also depend on technical advancesand processing improvements needed to reduce thecost of lignocellulosic material deconstruction into
simple sugars and other organic carbon compounds
suitable for feeding heterotrophic microalgae.
• The supply, availability, and cost of other nutrients(i.e., N, P, K) required as inputs for algae growth will
also play a role in commercial viability and extent ofindustrial build-up. Commercial fertilizer costs aretied closely to the cost of energy supplies (natural gas
and petroleum), and can be an appreciable factor inoperational costs for algae (Massingale et al., 2008)
to the same extent as for large scale commercial
agriculture (Huang, 2009; Malcolm et al., 2009). In
the absence of nitrogen fixation, algae can require as
much, if not more, nitrogen than conventional biomass
crops on a mass balance basis (Alexander et al., 2008).
Under large commercial algae industry build-up
scenarios, the amount of nutrients required nationallycould begin to approach the same order of magnitude
as large scale agriculture, where recent cost and supply
issues have had negative impacts on the industry(Huang, 2009). The capture and reuse of nutrientsfrom various agricultural and municipal waste streams(Woertz et al., 2009) can potentially help supply
nutrients for algae production scale-up, but this will bedependent on the geographical location, availability,
and affordable accessibility of such nutrient sources.
• CO2 availability and cost of delivery will play a majorrole in autotrophic microalgae cultivation scalability
and operating expense. As noted here and in chapter
9, it will be advantageous to co-locate cultivation
facilities with stationary industrial CO2 sources, but thiswill not be feasible in all instances and thus, it may benecessary to transport CO2 over some distance. Even in
the case of co-location, the size of an autotrophic algae
facility will require extensive pipeline infrastructure forCO2 distribution, adding to the cost. The quality of theCO2 source will also play a role for algal growth, andsome sources are likely to require more cleanup thanothers (especially if there are plans for animal feed asa co-product and/or if the CO2 source stream includes

contaminants that inhibit algae growth). Algae can beeffective at capturing and concentrating heavy metal
contaminants (Aksu, 1998; Mehta and Gaur, 2005),
such as are present in some forms of flue gas. This
could impact the suitability of residual biomass forco-products like animal feed, and is a consideration that
requires further investigation. Finally, carbon credits
must also enter into this analysis, though it is not yet
clear how best to factor this into the calculation.
• Land prices and availability can also impact the costof biofuel production at inland and coastal sites.
For offshore sites, the right of access and use, andthe associated logistics, risks, and costs of offshore
marine operations will have a major impact on
costs of production. Cost of site preparation andinfrastructure facilities for offshore, coastal, and inlandsites will all be location-dependent. It is reasonably
straightforward to calculate the impact of the costof land, and perhaps also for offshore sites, on theoverall cost of total algal biomass and intermediate
feedstock fraction (e.g., lipids, carbohydrates,
proteins, other) production, but for each approach
it will likely be an optimum minimum and rangeof size for a commercial production facility. If it isnecessary to distribute the facility over a number ofsmaller parcels of land or offshore sites, it may not
be possible to get the most benefit of economies ofscale. The key tradeoffs will be between the costof overall production (capital and operating costs)
versus the matching of affordable production scale tothe sustainable and affordable supply of the required
input resources with the required output productprocessing and distribution infrastructure and markets.
• As in traditional agriculture, the temperature during
the growing season will restrict the ability to cultivate
specific strains for extended durations. For open
systems operating at inland sites in the summer,
water evaporation rates will provide some level oftemperature control, but evaporation will also add tooperating cost (for water replacement and/or for saltmanagement with brackish or saline water. Conversely,
closed systems operating inland can overheat,requiring active cooling that can add prohibitively tothe cost of operations. Waste heat and energy fromco-located industries or the CO2 source may allow
active thermal management for growth during periodsof suboptimal (high or low) temperature, but applying
this heat or energy to extensive algal cultivation
systems will provide the same engineering problems
and costs as transporting and distributing CO2.

10. Systems and Techno-Economic Analysis

103

In summary, the calculations for the cost of algal biofuel
production will benefit from detailed inputs that take into
consideration the variations in cost and availability of theessential elements for cultivation. While these variations
may be minor relative to the technical uncertainties, it islikely that a technology that will require the productionof immense volumes of biofuel at affordable cost so it
can play a significant role in the national energy economy
would be subject to narrow operating margins.

Life Cycle Analysis
Life Cycle Analysis (LCA) is a “cradle-to-grave”
analysis approach for assessing the resource use andenvironmental impacts and tradeoffs of industrial systems
and processes. LCA is important for assessing relative
GHG emissions and other resource utilization (e.g.,water, energy) impacts among different approaches toalgal biofuels production, and in comparison with fuels
based on other renewable and non-renewable feedstocks.
LCA is considered to be a key element of the scope of TE
modeling and analysis within the context of this roadmap.
The systems modeling and analysis framework for algae
biofuels must include the integration of appropriate
LCA methodology and metrics (Curran, 1996; EPA,
1993; ISO, 1997; EPA, 2006; EPA, 2009; UNEP,
2005), and specifically leverage past and current LCA
work specific to biofuels (ANL 2009; Delucchi, 2004)
and including algae (Kadam, 1997, 2001 and 2002).
The term “life cycle” refers to the major activities in thecourse of the product’s life-span, from manufacture, use,
and maintenance, to final disposal, including the raw
material acquisition required to manufacture the product(EPA, 1993). Exhibit 10.11 illustrates the typical life
cycle stages considered in an LCA and the typical inputs/
outputs measured. LCA is a systematic technique to assess
the environmental aspects and potential impacts associatedwith a product, process, or service. The process employs aphased approach that consists of four major components:
goal definition and scoping, life cycle inventory analysis(LCI), life cycle impact assessment (LCIA), andinterpretation as illustrated in Exhibit 10.12 (ISO, 1997).
LCA methodologies, modeling, data base resources, andtools have been developed that include Argonne National
Laboratory’s GREET “well-to-wheels” model (ANL,2009), the UC/Davis Lifecycle Emission Model (Delucci,
2002 and 2004), and numerous others (EPA, 2009). In
addition to net GHG emissions, LCA for biofuels can also
assess impacts and tradeoffs associated with utilization
intensity for water, energy, nutrients, and other resources.

10.5 Algae Production
Costs and Uncertainties
Data gathering and validation of technical and economic
system performance for an industry that has yet to becommercially realized is one of the biggest challenges fortechno-economic analysis. To facilitate the Workshop’s
objectives of identifying needs, eliciting discussion,and compiling suggested directions for research anddevelopment from the participants, algal oil feedstock
production cost analyses were reviewed based on a
range of sources to gauge the status of algal biofuel
technology. These included technical reports prepared
for the U.S. Department of Energy (e.g., Benemann and
Oswald, 1996), peer-reviewed literature (e.g., Tapie andBernard, 1987), white papers / industry analyses, andpersonal communications with field experts. While mostcitable sources are quite dated, they also present a wide
variability in approach to final costs (from per gallon
of algal oil to per kg of “raw” biomass) and illustrate
a general lack of demonstrated operating parameters
and widely varying basic assumptions on a number ofparameters from algal productivity to capital depreciation
costs, operating costs, and co-product credits. These
shortcomings of the existing literature and modelingknowledge base present a challenge in designing scaled
up systems. There are indications, however, that a
combination of improved biological productivity andfully integrated production systems can bring the costdown to a point where algal biofuels can be competitive
with petroleum at approximately $100 per barrel.

10.6 Preliminary System
Dynamics Modeling
Systems dynamics modeling is a powerful and flexible
modeling approach that can foster collaborative analysis
and scenario studies. A dynamics simulation model also
provides an integrated analysis framework that can include:• Broad value-chain scope: from resources andsiting through production to end use• Algae biofuel and co-products industry scale-up
potential, resource use, constraints and impacts• Input resources, output flows, waste stream
resource capture and reuse, co-generation• Integration with existing infrastructure• Required build-up of new infrastructure with timedelays, learning curves and improvement projections• Technical, economic, environmental, and policy issues• Feedbacks and Multiple Sector Interdependencies
with links to other models and analyses

104

10. Systems and Techno-Economic Analysis

The development of a system dynamics model for
conducting scenario analysis of algal biofuels production
scale-up and operations was initiated as part of the roadmap
effort and is currently a work in progress. The preliminarymodeling uses algae production and resource availability
data and assumptions from the same information
sources discussed earlier in this chapter and in chapter
9. Interactive graphical user interfaces,can facilitate theuse of the model to conduct rapid ‘what if’ analyses andtradeoff studies using different yield scenarios, technicaland economic performance for various pathways, andresource constraints. The model will eventually include
more detailed systems and processes modules for multiple
pathways being pursued for algae biofuels and co-products,
along with the ability to do Monte Carlo simulation,
varying parameters values within pre-set ranges in orderto describe the uncertainty or robustness of model output.

10.7 Potential Directions
for R&D Effort\in techno-economic analysis and the capture of datafrom fielded systems as they emerge over time canprovided needed additional information. Workshop
participants specifically suggested that the following
areas be addressed in the modeling and analysis.
• Determine the current state of technology• Identify critical path elements that offer opportunities
for cost reduction• Identify research areas most in need of support• Identify external factors that will impact cost
• Provide plan for entry of algal biofuel into a renewable
fuel portfolio• Inform and perhaps guide formation and/or
modifications to public policy• Incorporate appropriate insights and benefit fromalliances with industry associations
The Techno-Economic Analysis can accomplish this by:

The model described above was initially prepared inoutline form for the algae roadmap workshop, and has
been developed further since the workshop. The model
currently includes only a limited amount of available data.
To adequately inform research and investment decisions
for algal biofuel deployment, continued progress• Stressing dynamics over detail initially, expanding
detail later as available and needed• Employing modular modeling, e.g. ISBL and OSBL
approaches1• Establishing interface requirements between
sub-systems

OUTPUTSINPUTS

Raw Materials Acquisition
Raw Materials

Manufacturing

Atmospheric
Emissions
Waterborne
Wastes
Solid
WastesUse / Reuse / Maintenance
EnergyRecycle / Waste Management

Coproducts
Other
Releases

System Boundary
Exhibit 10.11 Scope of Life Cycle Analysis(Adapted from EPA 1993)

10. Systems and Techno-Economic Analysis

105

Goal Definationand ScopeInterpretatation

Inventory
Analysis

ImpactAssessment

Exhibit 10.12 Phases of a Life Cycle Analysis(Adapted from ISO, 1997)• Leveraging university and industry resources• Maintaining industry standard notation, units, etc.
Throughout the roadmap workshop and report development
process, significant algae-to-biofuels production system andprocess performance uncertainties (technical and economic)
have been identified along various steps in the value chain.
These have been noted in this and earlier chapters of the
Roadmap. Addressing the uncertainties in a systematicand integrated modeling and analysis framework will help
guide needed investments and speed the deployment of an106

10. Systems and Techno-Economic Analysis

algal biofuels industry. A critical complementary need isthe development, operation, monitoring, and evaluation oflarger-scale algae biofuel production systems and processes
that can provide data to validate and improve the modeling.
When done in a closely coordinated spiral development
fashion, the complementary bi-lateral feedback of
information and insight between the modeling and analysis,
and the experimental and operational investigations
with larger-scale systems in the field, can facilitate
more rapid technological advancement leading towardcommercialization.

References

Aksu, A. (1998). Biosorption of heavy metals by microalgae in batch and continuous systems.” In: Wastewater
Treatment with Algae, Y-S Won and N.F.Y. Tam, eds., Springer-Verlag, Berlin, pp. 37-54.
Argonne National Laboratory (2009). The greenhouse gas, regulated emissions, and energy use in transportation(GREET) model. Available online at: http://www.transportation.anl.gov/modeling_simulation/GREET/
AspenTech (2010). AspenTech software product portfolio, including AspenPlus® and Aspen Process Economic
Analyzer (formerly Aspen Icarus Process Evaluator®). http://www.aspentech.com/core/
Benneman, J. and Oswald, W. (1996). Systems and economic analysis of microalgae ponds for conversion
of CO2 to biomass. Report prepared for the Pittsburg Energy Technology Center. (Grant No. DE-FG2293PC93204). http://www.osti.gov/bridge/product.biblio.jsp?query_id=1&page=0&osti_id=493389
Curran (1996). M.A. Curran (ed), Environmental Life Cycle Assessment. ISBN 0-07-015063-X, McGraw-Hill.
Delucchi, Mark (2004). “Conceptual and Methodological Issues in Lifecycle Analyses of Transportation Fuels“, UCD-ITS-RR-04-45, 2004.
DOE (2009). DOE Hydrogen Program, http://www.hydrogen.energy.gov/ and specifically the DOE Hydrogen Analysis (H2A) Project:
http://www.hydrogen.energy.gov/h2a_analysis.html
Environmental Protection Agency (EPA). (1993). Life Cycle Assessment: Inventory Guidelines andPrinciples. (EPA/600/R-92/245). Cincinnati: Ohio. Office of Research and Development.
Environmental Protection Agency (EPA). (2006). Life cycle assessment: Principles and practice.
(EPA/600/R-06/060). Cincinnati: Ohio. Office of Research and Development.
Environmental Protection Agency (EPA). (2009). US-EPA LCA Resources Web Site (latest update July2009): Available on line at: http://www.epa.gov/ord/NRMRL/lcaccess/resources.html
Getman, D. (2009). Bioenergy knowledge discovery framework. Geographic Information Scienceand Technology Group, Oak Ridge National Laboratory, March 2009.
Huang, Wen-yuan (2009). “Factors Contributing to the Recent Increase in U.S. Fertilizer Prices, 2002-08”, USDA, ERS Report AR-33,
February 2009.
International Standards Organization. (1997). Environmental management - Life cycle assessment- Principles and Framework. International Standards Organization, ISO 14040.
James, S. C. and Varun, B. (in press). Optimizing algae growth in open-channel raceways. Journal of Computational Biology.
Kadam, K.L. (1997). “Power Plant Flue Gas as a Source of CO2 for Microalgae Cultivation: Economic Impact of Different Process
Options”, Energy Convers. Mgmt, v.38, Suppl., pp. S505-S510, 1997.
Kadam, K.L. (2001). “Microalgae Production from Power Plant Flue Gas: Environmental Implications on a Life Cycle Basis”,
NREL Report No. TP-510-29417.
Kadam, K.L. (2002). “Environmental implications of power generation via coal-microalgae cofiring”, Energy v.27, pp. 905-922, 2002.
Malcolm, Scott A., Marcel Aillery, and Marca Weinberg (2009). “Ethanol and a Changing Agricultural Landscape”, USDA ERS Report
Number 86, November 2009.
Mehta, S.K. and Gaur, J.P. (2005) Use of algae for removing heavy metal ions from wastewater: Progress and prospects.
Critical Reviews in Biotechnology. 25(3), 113-152.
Molina, G.E., Belarbi, E.H., Acien Fernandez, F.G., Medina, A.R., and Chisti, Y. (2003). Recovery of microalgal
biomass and metabolites: Process options and economics. Biotechnology Advances, 20. 491-515.
Oak Ridge National Laboratory (ORNL). (2003). Bioenergy conversion factors. Available online at:
http://www.localenergy.org/pdfs/Document%20Library/Bioenergy%20conversion%20factors.pdf
Rittmann, B. E. (2008). Opportunities for renewable bioenergy using microorganisms. Biotechnology and Bioengineering. 100(2), 203-212.
Schenk, P., Thomas-Hall, S.R., Stephens, E., Marx, U.C., Mussgnug, J.H., Posten, C., Kruse, O. and Hankamer, B. (2008).
Second generation biofuels: High-efficiency microalgae for biodiesel production. Bioenergy Research. 1(1), 20–43.
Sheehan, J., Dunahay, T., Benemann, J., and Roessler, P. (1998). A look back at the U.S. DOE’s aquatic species program –Biodiesel from algae. (NREL/TP-580-24190). Available online at: http://www.nrel.gov/docs/legosti/fy98/24190.pdf

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Tapie, P and Bernard, A. (1987). Microalgae production: Technical and economic evaluations.
Biotechnology and Bioengineering. 32, 873-885.
United Nations Enivironment Programme (UNEP). (2005). Life cycle approaches: The road from analysis to practice.
United Nations Environmental Program, UNEP/SETAC Life Cycle Initiative. Available online at: http://jp1.estis.
net/sites/lcinit/default.asp?site=lcinit&page_id=138F5949-6997-4BE6-A553-585E92C22EE4#lcirap
Weyer, K. M., Bush, D. R., Darzins, A., & Willson, B. D. (2009). Theoretical Maximum Algal Oil Production. BioEnergy Research, 1 -10.
Woertz, I., A. Feffer, T. Lundquist, and Y. Nelson (2009). “Algae Grown on Dairy and Municipal Wastewater for Simultaneous Nutrient
Removal and Lipid Production for Biofuel Feedstock”, Journal of Environmental Engineering, American Societyof Civil Engineers, v135, n11, pp. 1115-1122.

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11. Public-Private Partnerships
The Workshop participants emphasized the needfor DOE and other federal agencies to partner withnational laboratories, academia, and industry. The
participants, however, also noted the unique partnershipenvironment in algal biofuels development, given
the fact that the algal biofuels industry is still in its
infancy. More specifically, given the current state ofthis industry, the business strategies of many existing
companies are focused on one or more aspects ofalgae, but not necessarily producing transportation
biofuels from cultivated algal biomass at scale.
This chapter discusses potential models for public-private
partnerships in general and specifically as related to algal
biofuels. Various models for such partnerships employedin past efforts are discussed in the context of applicability
to the algal biofuels challenge, including characteristics
for membership and intellectual property models.

11.1 The Benefits of Algal Biofuels
Public-Private Partnerships
Since the 1980s, the U.S. has increasingly invoked
public-private partnerships not only for large-scale
infrastructure projects, but also for research and technology
developments of national interest (Stiglitz and Wallsten,1999). Indeed, analyses of various federal agencies
and government programs aimed at public-private
partnerships are documented (Audretsch et al., 2002; Link
et al., 2002), including specific studies on the impactsof DOE programs on the clean energy sector (Brown,
2001; Brown et al., 2001; Gallagher et al., 2006).

The algal biofuels industry is evolving with numerous
players, many focusing on one to a few elements inthe algal biofuels value chain. Partnerships basedon sharing of knowledge and capabilities for mutual
benefit could pull together the current expertise andfacilities, thereby facilitating growth and developmentof a sustainable, algal biofuels industry. The type ofpartnership most relevant to the advancement of the algal
biofuels industry is perhaps the research partnershipenvisioned by the Council on Competitiveness (1996):
Partnerships are defined as cooperative
arrangements engaging companies, universities,
and government agencies and laboratories invarious combinations to pool resources in pursuitof a shared R&D objective.
Exhibit 11.1 shows the potential benefits ofcollaboration between private entities (e.g., industry)and public entities (e.g., national laboratories anduniversities) for development of algal biofuels.A
While benefiting both private and public entities fromshared investment toward mutual objectives, publicprivate partnerships have the potential to acceleratecommercialization of algal biofuel technology, leading
to rapid industry growth and a stable market.
Industry benefits from public-private partnerships from theexposure to fundamental science and engineering R&D,
which can support a quickening pace of innovation. This
could, in turn, increase the capital efficiency of commercial
firms, many of which may be investor-backed andpre-revenue, as well as reduces the risk of private
investment. By focsuing these partnerships on precompetitive research or critical problems shared by all

Exhibit 11.1 Benefits of algal biofuels public-private partnerships

Public Benefits
Energy Security
Long-term Clean Fuel
Solution
Climate Change Migration
Jobs Creation
Clean Energy &Science Leadership

Shared Benefits
Technolgy Commercialization
Industry Growth & Market Stability
Shared Investment
Domestic Energy Supply
Sustainable Industry
Development

Private Benefits
Innovation Quickens
Shared Risk &Capital Efficiency
Competitive Edge
Breakdown Legal &Regulatory Hurdles
Growth Stimulates
Labor PoolA

In this situation, academia can be either public or
private, realizing benefits in both categories.

11. Public-Private Partnerships

109

players (e.g., technology scale-up and demonstration,
regulatory issues, labor), industry would retain its
competitive edge, while increasing the opportunity todevelop and license technology with new partners.

11.2 Components of Successful
Public-Private Partnerships
At the highest level, successful partnerships havebeen identified to include the following attributes:• The partners collaborate on the basis ofcommon interest.
• The benefits of partnership outweigh the costof collaboration.
• The partners can achieve more through collaboration
than they can individually.
• The benefits received from the partnership should
be proportional to the value of the contribution.
• The partnership should not openly conflict with theinterest of other groups (Micheau, 2008).
Partnerships can bring together parties that have notworked together before, which could both be a benefit(new complementary capability) and a challenge (theunderstanding of how to work together). Implicit in theconcept of collaborating on a common basis is the sharingof pre-competitive research results, which could allow
for the advancement of technology and know-how tolevels beyond the capability of any individual entity.

11.3 Forums for PublicPrivate Partnerships
There are several forums for creating public-private
partnerships:• Networking events such as seminars and conferences• Team-oriented government solicitations• Consortia and trade organizations• Team-oriented prizes
Networking events such as workshops, conferences, andseminars can be important tools for creating a collaborativeenvironment. Through these events, scientists and engineers
can learn of new research, and potential partners can
explore areas of mutual interest. These events are often
the point at which new researchers can enter and where
new thought or methodology is shared with the peers.

110

11. Public-Private Partnerships

Government solicitations are also an option to promotecollaborative research to tackle complex problems
through public-private partnerships. Often these typesof solicitations are system-oriented, where no single
entity can address the complex research challenge.
This may result in the formation of teams of proposers
in a project-level partnership. Such solicitations havethe potential to accelerate technology development,
particularly in instances in which the team would nothave necessarily come together without a governmentfunded solicitation. However, these partnerships canonly be expected to last for the life of the project, as
they are often formed to serve no other purpose.
Consortia and trade organizations are membershiporganizations that may provide an opportunity forlasting partnerships. Partnerships are facilitated inthese environments through collaborations among
the membership. By maintaining an active directory,
consortia and trade organizations can also be an effective
vehicle for researchers looking for a new approach or
new partnership, as well as a platform to share research.
Through their structure, these organizations provide foropportunity to facilitate deeper collaborations. However,organizations that promote a closed circle of partners who
have worked together for many years may not generate
the new thinking and fresh approaches that could be
gained through openness toward new partnerships.
In recent years, prizes have been offered by variousorganizations to support solving critical, national, or
global problems, including the development of biofuels.B,C
Prize forums can pull together developed technology
into a working system to solve a problem, and demandthat the winning team meet or exceed certain successcriteria. Prize forums can also leverage reward moneyfrom a variety of different funding sources (state andfederal government, non-profit foundations, and private
investors) into a single competition, and provide publicity
and marketing toolsets for competitors to attract future
investors. However, because some awards are based on
having solved the problem, such forums may favor maturetechnology in the final stages of development where thefocus can be on assembly into a working system. Basic
research and early stage technology with limited funding
may compete poorly in this type of award, with the ultimate
solution only as good as existing technology will allow.

11.4 Partnership Challenges in
the Algal Biofuels Industry

Public-private partnerships—whether they
are formed or sustained through networking
events, government solicitations, consortia, prize
competitions, or trade organizations—can be aneffective way to address technological, economic,
and public-policy and regulatory challenges.
As discussed in greater detail in this document, several
key technological challenges must be addressed forthe algal biofuels to become viable. These include:• An open environment to share ideas and technology
across the entire algal biofuels value chain;• Technology development in algal biology,
algal growth and harvesting, algal oil
extraction, and fuel conversion;• Pre-commercial-scale user facilities that areaccessible to researchers and developers
to road-test their technologies;• The generation of basic methods and standards; and• Labor force and intellectual talent to draw upon.
Technology partnerships could be used for following
objectives:• Share knowledge of existing algal strains throughan open access repository and collaborate on thedevelopment of new natural or GMO algal strains• Share knowledge of algal cultivation andcollaborate on the development of dynamic
monitoring of growth operations• Collaborate on the development of technologies
for biomass harvesting and extraction ofalgal components from the biomass

As this industry expands, it will need labor to run its
operations, develop new algae-based fuels and co-products,
and innovate new cost-cutting measures. Academia willbe the workhorse that generates labor for this new industry.
Collaborative partnerships, particularly between industry
and academia, are needed to ensure that academia develops
students capable of addressing the challenges industry faces
in algal biofuels. Also, in order to fully realize the potentialof the algal biofuels industry, public-private partnerships
are needed to engage field experts (e.g., real estatedevelopers, construction personnel, lawyers, marketingand public relations specialists, distributors) across thevalue chain to address technical and non-technical needs.

11.5 Modeling Partnerships forTechnology Development
Of the different forums for public-private partnerships,
collaborative consortia for technology development are
the most difficult to implement. These consortia require
all of the key attributes for successful partnerships
noted earlier. Therefore, it is useful to conceptualize
the various models for public-private consortia in termsof the five attributes of successful partnerships within
the context of particular scenarios (e.g., particular algal
strain, dewatering pathway, conversion process, etc.) or
end goals (specific intended use, performance aspects ofthe fuel, etc.). Doing so may help define the boundary
problem(s) for focus by a public-private consortiumand bring clarity to the composition, requirements,and expected contributions of the membership.
Considering the following four external characteristics
can help evaluate consortia models:• Share knowledge of fuel requirements
and utilization to advance fuel conversion
technologies toward marketable products• Openness. How inclusive is the membershipto its industry (or segment thereof)?

In the biofuels industry, technologies developed in thelaboratory have traditionally not translated well to thefield (Willems, 2009). Algal biofuels will likely facesimilar issues since natural environmental constraints
could have a significant impact on algal productivity. A
public-private partnership for pre-commercial-scale user
facilities could allow for new technologies to be roadtested and scaled before full-scale deployment in thefield. This type of partnership would greatly acceleratetechnology development, overcoming the lab-fieldscaling barrier and the lack of private capital to conduct
such applied research. By reducing scaling risks, thistype of partnership can help incentivize commercial
investment of similar full-scale algal operations.

• Industry Growth. Does it seek to grow the industry?

B
C

http://www.xprize.org/future-x-prizes/energy-and-environment
http://www.mitcep.org/• Technology Commercialization. Is it structured todevelop and commercialize new technology?
• Shared Investment. Does it share investment equitably?
Different consortia models exist and it is possible tocompare some of these existing public-private consortia
models against these four external characteristics,
as illustrated in Exhibit 11.2. The exhibit compares
PPP models from five different industry sectors –semiconductors, biofuels, nanotechnology, aviation,and information technology. These PPP models are
mentioned only to serve as examples of the four external
characteristics. Because the ecosystem in the algal
biofuels industry is unique and differs greatly fromthe established industry sectors represented by most
11. Public-Private Partnerships

111

models presented, this industry may find that no specific model will meet all of its needs. However, for an algal biofuels
public-private consortium to meet its specific mission successfully, it could be helpful to consider these attributes
and models, discuss and debate the merits of each, and determine how to best adapt / implement these attributes.

Exhibit 11.2 Comparison of Some Public-Private-Partnership (PPP) Models

INDUSTRY FOCUS

ENTITY TYPEOPENNESS OF PPPTECHNOLOGYCOMMERCIALIZATION• Collaborate on
pre-competitive R&D
selected by membership• Open membership

Semiconductors

Biofuels

112

Non-Profit
Corporation(501c6) withphysicalfacilities

Government
AgencyResearchCenters(not aseparate legal
entity with
employees)

11. Public-Private Partnerships• Transfer of technology by
publication or memberwebsite data transfer

INDUSTRY GROWTHSHAREDINVESTMENT• Designed
to increase
competitiveness ofexisting US firms inmarketplace• Provides• Cost-shared• Technology further
commercialization
by government
developed to manufacturing
network thatand industry atsolutions with external• Forums inspiring
drives economic
start-uppartners; then adopted
cross collaboration
development• Now fundedamongst members • PPP owns created IP and• Develops
solely by industry
provides non-exclusive,• Public conferences
coordinatedroyalty-free license toindustry roadmap tomembers
focus R&D and spur
• PPP can also license IP toon economic growththird parties• Represent
industry interests• R&D conducted at Research • Address gamechanging, high-riskCenters or partner facilities• Partners withbarriers through• Industry partners toindustry andtargeted R&D
commercialize developed IP
universities• Industry growth• Public conferences • IP licensed to interested
supported throughparties with an evaluation
and workshops
educationof commercialization• Opportunities for• Limited industry
potential
collaboration
involvement to• Transfer of technology byaddress issues on
publicationindustry growth• Government
funding• State funding• Financial andother resourcesfrom nationallabs

INDUSTRY FOCUS

Nanotechnology

Aviation

ENTITY TYPEOPENNESS OF PPPTECHNOLOGYCOMMERCIALIZATION

INDUSTRY GROWTHSHAREDINVESTMENT

Non-Profit
Corporation(501c6) withphysicalfacilities• Open membership• Consortium of
industry, academic
and national lab
partners;• Technicalworkshops;
technical,
business, andsocial issues
inspire crosscollaboration
amongst members• Pre-competitive research
selected by all members• Research conducted bynational labs and member
universities• PPP provides non-exclusive,
paid-up license to industry
members• Industry growththrough education• Technology
only licensed tomembers• Government
funding for over 5
years• Founding
member financial
commitment forover 3 years• Technology
development andstandardization
designed to reduce
operational costs
and increase
general aviation
market, including
large establishedfirms and small
businesses• Significant industry
involvement
provides market
focus andcommercialization
network• Government
funding for over 8
years• Industry matchfor same numberof years• Industry growth
supported througheducation• Limited industry
involvement
through Advisorycommittee toaddress issues on
industry growth• State funding
over 4 years• University funds• Industry gifts• No federal
fundingIndustry
consortiumwith NASA& FAA (not a
separate legal
entity with
employees• Collaborative researchamongst consortium
members designed
to reduce technical,
operational, and regulatory
bottlenecks• IP licensed exclusively or
non-exclusively• Open membership,• Commercialization afforded• Consortium ofas members agree to crossindustry, academic
license background andand government
newly developed IP nonpartners
exclusively to each otherroyalty-free• Transfer of technology by
publication, and transfer
of knowledge throughmember-only database• Donor-driven
model• Industry andUniversity
university partnersof California
Information• Numerous forums
Institute
Technology Researchinspiring cross(not a separate
collaboration
legal entity
amongstwith employees
researchers fromuniversities andcompanies• Research conducted byuniversity• Software is open source
licensed• Other IP is either licensed
non-exclusively, royaltyfree basis or exclusively,
royalty basis as needed toachieve the widest possible
dissemination.

11. Public-Private Partnerships

113

References
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114

11. Public-Private Partnerships

Appendices
Appendix 1 : Workshop Participants
Walter Adey

Smithsonian Institution

John Aikens

LybradynMark Allen

A2be Carbon Capture

Gennady Ananyev

Princeton

Alex Aravanis

Sapphire Energy

Ed Archuleta

El Paso Water Utilities

Paul Argyropoulos

Environmental Protection Agency

Ricardo Arjona

Abengoa Bioenergy

Virginia Armbrust

University of Washington

Bob AvantTexas A&M

Tom Avedisian

U.S. Department of Energy

David BaylessOhio University

Jacques Beaudry-Losique

U.S. Department of Energy Biomass Program

Leslie Bebout

NASA Ames Research Center

Lucie Bednarova

General Motors

Amha Belay

Earthrise Nutritionals

John Benemann

Benemann Associates

Linda Benjamin

Food and Drug Administration

Christoph Benning

Michigan State

Isaac BerzinInterdisciplinary Center Herzliya, Lauder School of Government, Diplomacy
And Strategy

Catalino Blanche

U.S. Department of Agriculture

Doug Borger

Lockheed Martin

John Bouterse

Envo Smart

Sara Boyd

BCS, Inc.

Andrew Braff

Wilson Sonsini Goodrich & Rosati

Jim Brainard

National Renewable Energy Laboratory

Jerry Brand

University of Texas at Austin

Tom Brennan

Arch Ventures

Michael Briggs

University of New Hampshire

Jim Bristow

Joint Genome InstituteKevin Brown-

Malcolm Brown

University of Texas at Austin

Nathan Brown

Federal Aviation Administration (Office of Environment And Energy)

Kent Bryan

City of Celina

115

AppendicesWilliam Buchan

NASA Ames Research Center

Jay Burns

Bionavitas

Arthur Butcher

CPS Energy

Thomas Byrne

Byrne & Co

Martin Carrera

BP

Matt Caspari

Aurora Biofuels

Chris Cassidy

U.S. Department of Agriculture

Heriberto Cerutti

University of Nebraska - Lincoln

Alice Chen

Environmental Protection Agency

Parag Chitnis

National Science Foundation

Daniel Cicero

National Energy Technology Laboratory

Mike Cleary

National Renewable Energy Laboratory

John Coleman

Algenol

Jim Cook

Univenture

Doris Cooksey

CPS Energy

Keith CookseyMontana State University

Michael Cooney

University of Hawaii – Manoa

David Daggett

BoeingAl Darzins

National Renewable Energy Laboratory

K.C. Das

University of Georgia

John Datko

Air Force Office of Scientific Research

Chris Davies

Independence Bioproducts

Brian Davison

Oak Ridge National Laboratory

Mark Decot

U.S. Department of Energy Biomass Program

Michel Delafontaine

Hawaii Biocrude

Gregg Deluga

General Electric Global Research

Harrison Dillon

Solazyme

Dan Drell

Office of Science Biological and Environmental ResearchDonn Dresselhuys

Old Dominion University

Bruce Eldridge

University of Texas at Austin

Tj Evens

U.S. Department of Agriculture

Paul Falkowski

Rutgers University

John Ferrell

U.S. Department of Energy, Biomass Program

Daniel Fishman

BCS, Inc.

Todd French

Mississippi State

Christian Fritsen

Desert Research Institute

Matthew Frome

Solozyme

Maria Ghirardi

National Renewable Energy Laboratory

Appendices116

Warren GilletteFederal Aviation Administration (Office of Environment And Energy)

Jim Gillingham

ValeroDan Ginosar

Lawrence Livermore National Laboratory

Robert Glass

Lawrence Livermore National Laboratory

Steven Gluck

Dow Chemical

Steve Gorin

National Renewable Energy Laboratory

Alison Goss Eng

U.S. Department of Energy, Biomass Program

Suzanne Goss

Jacksonville Electric Authority

Paul Grabowski

U.S. Department of Energy, Biomass Program

Michael Graves

University of Massachusetts

Bailey Green

Lawrence Berkeley National Laboratory

Eli Greenbaum

Oak Ridge National Laboratory

Nathanael Greene

Natural Resources Defense Council

Michael Gregoire

U.S. Department of Agriculture

Tom GrossIf, LLC

Arthur Grossman

Stanford

Guritno “Guri” Roesijadi

Pacific Northwest National Laboratory

Molly Hames

U.S. Department of Energy, Golden Field Office

Anders Handlos Grauslund

Novozymes

Zia Haq

U.S. Department of Energy Biomass Program

Laurel Harmon

UOP

Deanna Hatch

Organofuels Incorporated

Pat Hatcher

Old Dominion University

David Hazlebeck

General Atomics

Bob Hebner

University of Texas at Austin

Grant Heffelfinger

Sandia National Laboratories

Erik Helm

Environmental Protection Agency

William Henley

Oklahoma State

Doug Henston

Solix Biofuels

Jurg Heuberger

County of Imperial

Kevin Hicks

U.S. Department of Agriculture

Mark HildebrandScripps Institute

Masahito Hiratake

Mitsubishi International

Kent Hoekman

Desert Research Institute

Neil Hoffman

U.S. Department of Agriculture

Ed Hogan

Natural Resources Canada

John Hogan

NASA Ames Research Center

John Holladay

Pacific Northwest National Laboratory

117

AppendicesAndy Horne

Natural Resources Development

Jeff Houff

Hydrogeologic, Inc

Qiang Hu

Arizona State University

Neil Huber

Army

Michael Huesemann

Pacific Northwest National Laboratory

Peter Hug

Recombinant Innovation, LLC

J.C. Hunter-Cevera

University of Maryland Biotechnology InstituteMark Huntley

University of Hawaii

Stephen J. Miller

Chevron Chevron

Gil Jackson

United States Agency for International Development

Jacob Jacobson

Idaho National Laboratory

Robert Jagusch

Minnesota Muncipal Utilitees Association

Eric Jarvis

National Renewable Energy Laboratory

Jeff Jeter

Honda

Libby Jewett

National Oceanic and Atmospheric Administration

James “Jim” Sears

A2be Carbon Capture

Michael Johnson

Massachusetts Institute of Technology

Glen Kertz

Valcent

Alex Kinnier

Khosla Ventures

Douglas Kirkpatrick

Defense Advanced Research Projects Agency

Melissa Klembara

U.S. Department of Energy Biomass Program

Geetha Kothandaraman

ConocoPhillips

Walt Kozumbo

Air Force Office of Scientific Research

Heidi Kuehnle

Kuehnle Agrosystems

Peter Lammers

New Mexico State University

Cynthia Lane

American Water Works Association

Todd Lane

Sandia National Laboratories

Mario Larach

Kai Bioenergy Corp.

Rachel Lattimore

Arent Fox LLP

Edward Laws

University of Hawaii at Monoa

Gordon LeblancPetrosunJoo-Youp Lee

University of Cincinnati

Paul Lefebvre

University of Minnesota

James Lester

Stratus Consulting

Jack Lewnard

Gas Technology InstituteCasey Lippmeier

MartekKent Lohman

Midwest Research InstituteTryg Lundquist

California Polytechnic State University

Appendices118

John Magnuson

Pacific Northwest National Laboratory

Len Malczynski

Sandia National Laboratories

Mike Manella

ADM

Russell Martin

Blue Source

Anthony Martino

Sandia National Laboratories

Margaret McCormick

Targeted Growth

Patrick McGinn

National Research Council

John McGowen

Biodesign Institute at Arizona State University

Diane McKnight

University of Colorado-Boulder

Steve Meller

Procter & Gamble

Omar Mendoza

United States Air Force

Walter Messier

Evolutionary Genomics

Blaine Metting

Pacific Northwest National Laboratory

Anelia Milbrandt

National Renewable Energy Laboratory

Greg Mitchell

Scripps Institution of Oceanography

John Mizroch

U.S. Department of Energy

Lissa Morgenthaler-Jones

Livefuels

Jerry Morris

Innovation/Biodomain - Shell Global Solutions Inc.

Kenneth Moss

Environmental Protection Agency

Chuck Mueller

Sandia National Laboratories

Jeff Muhs

Utah State University

Walter Mulbry

U.S. Department of Agriculture

Alyson Myers

Kegotank Biofuels

Nick Nagle

National Renewable Energy Laboratory

David Nobles

University of Texas at Austin

Charley O’kelly

Blue Marble Energy

Lou Ogaard

CEHMM

Kelly Ogilvie

Blue Marble Energy

John OhlroggeMichigan State University

Jose Olivares

Los Alamos National Laboratory

Phil Ovitt

Senator Brownback OfficeGeorge Oyler

Johns Hopkins University

Stephen P. Mayfield

Scripps Research InstituteMike Pacheco

National Renewable Energy Laboratory

Paul Panesgrau

National Renewable Energy Laboratory

Frank Parker

Organofuels Incorporated

Helen Parker

Algaelink, N.V.

Roberta Parry

Environmental Protection Agency

119

AppendicesRon Pate

Sandia National Laboratories

Leslie Pezzullo

U.S. Department of Energy, Biomass Program

Schild Philippe

European Commission

Philip Pienkos

National Renewable Energy Laboratory

Maria Piera

Abengoa Bioenergy

John Pierce

Wilson Sonsini Goodrich & Rosati

Daniel Pike

AF Research Lab

Jennifer Pinkerton

LA Department of Water & Power

Bradley Plantz

University of Nebraska-Lincoln

John PlazaJohn Plaza

Robert Polak

PhycalJuergen Polle

Brooklyn College

Matt Posewitz

Colorado School of Mines

Steve Potts

EPA Office of Water

Peter Pryfogle

Idaho National Laboratory

Steve Przesmitski

National Renewable Energy Laboratory

Theras Pugh

American Public Power Association

Ron Putt

Auburn University

Nigel Quinn

Lawrence Berkeley National Laboratory

Kenneth Reardon

Colorado State University

Hal Reed

American Water

Valerie Reed

U.S. Department of Energy, Biomass Program

Ron Reinsfelder

Shell Global Solutions

Bruce Resnick

CargillCurt Rich

Van Ness Feldman

Mark Riedy

Andrews Kurth

Kathy Roach

MurphyTate, LLC

John Robbins

Exxonmobil

Paul Roessler

Synthetic Genomics

Roger Ruan

University of Minnesota

Jim Ryan

MOR Supercritical, LLC

Gerson Santos-Leon

Abengoa Bioenergy

Richard Sayre

Donald Danforth Plant Science Center

Philippe Schild

European Commission

Gerald Seeley

Old Dominion University/Company

Mark Segal

Environmental Protection Agency

Mike Seibert

National Renewable Energy Laboratory

Joel Serface

Kleiner Perkins

Appendices120

Pamela Serino

Defense Energy Support Center

Chris Shaddix

Sandia National Laboratories

Alex Shearer

SRI International

John Sheehan

Sheehanboyce, LLC

Tanja Shonkwiler

Jamestown Ny (Outside Counsel)

Blake Simmons

Sandia National Laboratories

Knut Simonsen

DTE Energy Resources, Inc.

Evan Smith

The Verno Group

Seth Snyder

Argonne National Laboratory

Milton Sommerfeld

Arizona State University

Glenn Sonntag

U.S. Department of Energy, Biomass Program

John Spear

Colorado School of Mines

Karl Stahlkopf

Hawaiian Electric Company, Inc.

Cai Steger

Natural Resources Defense Council

Dan Stepan

Energy & Environmental Research Center

Jake Stewart

Organic Fuels

Mark Stone

Desert Research Institute

Belinda Sturm

Kansas University Transportation Research InstituteSidhu Sukh

University of Dayton

Xiaolei Sun

Arizona Public Service

Sam Tagore

U.S. Department of Energy, Biomass Program

Evonne Tang

National Academy of Sciences

Jeff Tester

Massachusetts Institute of Technology

Robert Thomas

South Australia R&D Institute

Jonathan Trent

NASA Ames Research Center

Pat Unkefer

Los Alamos

James Van Etten

University of Nebraska

Peter Van Den Dorpel

Algaelink, N.V.

Jean Vandergheynst

UC Davis

Tom Verry

National Biodiesel Board

Sanjay Wagle

Vantagepoint Venture

Kevin Wanttaja

Salt River Project

Michael Webber

The University of Texas at Austin

Alan Weber

Marc-IV Consulting

Donald Weeks

University of Nebraska - Lincoln

Alan Weimer

University of Colorado at Boulder

Zhiyou Wen

Virginia Tech

Norman Whitton

Sunrise Ridge Algae

121

AppendicesElizabeth Willet

Mars Symbioscience

Bryan Willson

Colorado State University

Byard Wood

Utah State University

Christopher Wood

Platt River Power Authority

David Woodbury

Biofuel Producers of America (BpaPaul Woods

Algenol

Ben WuLivefuels

Don Wyma

National Intelligence Officer For Science And Technology

Joyce Yang

U.S. Department of Energy Biomass Program

Chris Yeager

Savannah River National Laboratory

Ross Youngs

Univenture

Tim Zenk

Sapphire Energy

Zhenqi Zhu

Stevens Institute of Technology

Yonathan Zohar

University of Maryland Biotechnology Institute

Appendix 2: Contributors
Jim Brainard

National Renewable Energy Laboratory

Tom Brennan

Arch Ventures

Bill Buchan

NASA Ames Research Center

Mike Cleary

National Renewable Energy Laboratory

Michael Cooney

University of Hawaii – Manoa

Al Darzins

National Renewable Energy Laboratory

Daniel Fishman

BCS, Inc.

Maria Ghirardi

National Renewable Energy Laboratory

Stephen Gorin

National Renewable Energy Laboratory

Tom Gross

IF, LLC.

Molly Hames

U.S. Department of Energy Golden Field OfficeGrant Heffelfinger

Sandia National Laboratories

Mark HildebrandScripps Institution of Oceanography

John Hogan

NASA Ames Research Center

Qiang Hu

Arizona State University

Michael Huesemann

Pacific Northwest National Laboratory

Eric Jarvis

National Renewable Energy Laboratory

Geoff Klise

Sandia National Laboratories

Alina Kulikowski-Tan

Carbon Capture Corp

Pete Lammers

New Mexico State University

Jared Largen

BCS, Inc.
Appendices122

Yantao Li

Arizona State University

Tryg Lundquist

California Polytechnic State University

Rajita Majumdar

BCS, Inc.

Len Malcynski

Sandia National Laboratories

Tony Martino

National Renewable Energy Laboratory

Steve Mayfield

Scripps Institution of Oceanography

Anelia Milbrandt

National Renewable Energy Laboratory

Joanne Morello

U.S. Department of Energy, Biomass Program

Chuck Mueller

Sandia National Laboratories

Nick Nagle

National Renewable Energy Laboratory

Michael Pacheco

National Renewable Energy Laboratory

Ron Pate

Sandia National Laboratory

Leslie Pezzullo

U.S. Department of Energy, Biomass Program

Philip Pienkos

National Renewable Energy Laboratory

Juergen Polle

Brooklyn College

Matthew Posewitz

Colorado School of Mines

Ron Putt

Auburn University

Kathy Roach

MurphyTate, LLC.

Guri Roesijadi

Pacific Northwest National Laboratory

Mike Seibert

National Renewable Energy Laboratory

Joel Serface

Kleiner Perkins

Chris Shaddix

Sandia National Laboratories

Blake Simmons

Sandia National Laboratories

Amy SunSandia National Laboratories

Joyce Yang

U.S. Department of Energy, Biomass Program

123

AppendicesAppendix 3: Respondents to Request for Informationon the Draft Roadmap
Daniel Angell

TPA Inc.

Bob Avant et al

Texas AM

Halil Berberoglu

University of Texas

Shulin Chen et al

Washington University

Barry Cohen

National Algae Association

Anju Dahiya

1) The University of Vermont ; 2) General Systems Research LLC

Matthew Frome

Solazyme

Michael R. Gale

PetroAlgae, LLC

Arthur Grossman

Carnegie Institution for Science (Staff member), Stanford University(Adjunct Professor), Solazyme (Chief of Genetics)

Douglas Haughey

not listed

Joel E. Kostka

Florida State University

David Lewis

The University of Adelaide

Margaret McCormick

Targeted Growth

Lissa Morgenthaler-Jones

LiveFuels, Inc

Matt PeakPrize Capital

María Piera Alberola

Abengoa

Matthew Posewitz

Colorado School of Mines

Bruce Resnick

Cargill

Bruce E. Rittmann

Center for Environmental Biotechnology, Biodesign Institute,Arizona State University

G. Roesijadi

Pacific Northwest National Laboratory

Mary Rosenthal

Algal Biomass Organization

Richard Sayre and Ursula GoodenoughDonald Danforth Plant Science Center and Washington University

Gerard Seeley Jr.

Algal Farms Inc.

Mark Segal

Environmental Protection Agency Office of Pollution Prevention and Toxics

Alexander D. Shenderov

BioLogical Technologies, Inc.

Dr. Valentin Soloiu

Georgia Southern University

Lance Stokes

ECI Environmental Compliance

Jefferson Tester

Cornell University

Willem Vermaas

Arizona State University, School of Life Sciences

Marc von Keitz and Steve Heilmann

University of Minnesota, Biotechnology InstituteDavid L. Wenbert

The Eden Tube Project

Norman M. Whitton, Dr. Robert S Weber

Sunrise Ridge Algae, Inc.

Paul Woods

Algenol

Xiaohan Yang

Oak Ridge National Laboratory

Tim Zenk

Sapphire Energy

Appendices

124

DOE/EE-0332
www.eere.energy.gov