2016 National Algal Biofuels Technology Review

212 Pages·2016·10.1 MB·English

National Algal Biofuels
Technology Review
Bioenergy Technologies Office
June 2016

National Algal Biofuels
Technology Review
U.S. Department of Energy Office of
Energy Efficiency and Renewable Energy
Bioenergy Technologies Office
June 2016
Review Editors:
Amanda Barry,1,5 Alexis Wolfe,2 Christine English,3,5 Colleen Ruddick,4 and Devinn Lambert5
2010 National Algal Biofuels Technology Roadmap:
eere.energy.gov/bioenergy/pdfs/algal_biofuels_roadmap.pdf
A complete list of roadmap and review contributors is available in the appendix.
Suggested Citation for this Review:
DOE (U.S. Department of Energy). 2016. National Algal Biofuels Technology Review. U.S.
Department of Energy, Office of Energy Efficiency and Renewable Energy, Bioenergy
Technologies Office.
Visit bioenergy.energy.gov for more information.
1 Los Alamos National Laboratory
2 Oak Ridge Institute for Science and Education
3 National Renewable Energy Laboratory
4 BCS, Incorporated
5 Bioenergy Technologies Office
This report is being disseminated by the U.S. 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.
Cover photo courtesy of Qualitas Health, Inc.
BIOENERGY TECHNOLOGIES OFFICE
Preface
Thank you for your interest in the U.S. Department of Energy (DOE) Bioenergy Technologies Office’s (BETO’s)
National Algal Biofuels Technology Review. This 2016 update to the 2010 National Algal Biofuels Technology
Roadmap is a review of algal biofuels research at every step of the supply chain. It addresses several research areas
highlighting advances, outlining unknowns, and discussing opportunities for advancement.
Domestic renewable energy provides potential solutions to priorities for the United States, such as decreasing
dependence on foreign oil, revitalizing rural America by creating new jobs across many sectors of the economy, and
reducing carbon emissions. Through strategic investments and close coordination with partners in industry, academia,
national laboratories, and other agencies, DOE is committed to developing and demonstrating transformative and
revolutionary bioenergy technologies for a sustainable nation.
Algae have significant potential to support an advanced biofuels industry. The goal of the BETO Advanced Algal
Systems Program is to develop cost-effective algal biofuels production and logistics systems. The program focuses
on supporting the growth of the emerging domestic algae industry and its interest in commercialization for fuels and
products, specifically by reducing costs of production and ensuring the sustainability and availability of resources.
DOE revived its investment in algal biofuels in 2009 in response to the increased urgency of lowering greenhouse
gas emissions and producing affordable, reliable renewable energy, as well as the increasing recognition that we will
not achieve these goals via any single technology pathway. Since then, BETO has invested in a variety of research,
development, and demonstration (RD&D) projects that tackle the most impactful barriers associated with the scale-
up of commercial algal biofuels. BETO is proud of the progress of our partners, and has the pleasure of highlighting
many of their projects within this review, along with the work of the broader research community.
The National Algal Biofuels Technology Review, as a summary of algal biofuels research and development to-date,
serves as one reference to inform the implementation of the BETO strategy to achieve the vision of a thriving and
sustainable bioeconomy fueled by innovative technologies. This review is intended to be a resource for researchers,
engineers, and decision-makers by providing a summary of algal biofuel research progress to date and the challenges
that could be addressed by future RD&D activities. We hope this review fosters and informs participation from
all stakeholders as the next steps are taken to advancing an algal biofuels industry together. DOE looks forward to
continuing its work with diverse partners in the development of renewable energy options that provide the greatest
benefits in the years to come.
Jonathan L. Male
Director, Bioenergy Technologies Office
U.S. Department of Energy
Preface i
FROM ALGAE TO BIOFUELS
An Integrated Systems Approach to Renewable Energy that Is
ALGAE FEEDSTOCKS CULTIVATION
Microalgae and cyanobacteria can be cultivated via
photoautotrophic methods (where algae require light to
grow and create new biomass) in open or closed ponds or via
heterotrophic methods (where algae are grown without light
and are fed a carbon source, such as sugars, to generate new
biomass). Macroalgae (or seaweed) has different cultivation
needs 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 the
best suited downstream processing options. Choices made for
the cultivation system are key to the affordability, scalability,
and sustainability of algae to biofuel systems.

Fermentation Tanks
MICROALGAE CYANOBACTERIA MACROALGAE

Closed Photobioreactors
Algae as feedstocks for bioenergy refers to a diverse group of
organisms 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 the
biology of algal strains selected for use in production systems
is the foundation for processing feedstocks into fuels and
products.
Open Ponds
Example Cultivation Systems
POLICY SITING AND RESOURCES
Systems and Techno-Economic Analysis: GuiDdeinvge ltohpem Reenste Paarcthh Taonwd a r d a Commercially Viable Algal Biofuel Industry
FROM ALGAE TO BIOFUELS
An Integrated Systems Approach to Renewable Energy that Is Abundant, Affordable, and Sustainable
HARVESTING / DEWATERING CONVERSION
Some processes for the conversion of algae to liquid Conversion to fuels and products is predicated on a basic
process decision point:
transportation fuels require pre-processing steps such as
harvesting and dewatering. Algal cultures are mainly grown 1) Conversion of whole algal biomass;
in water and can require process steps to concentrate 2) Extraction of algal metabolites; or
harvested algal biomass prior to extraction and conversion.
3) Processing of direct algal secretions.
These steps can be energy-intensive and can entail siting
Conversion technology options include chemical,
issues.
biochemical, and thermochemical processes, or a
CH2-O-C
EXTRACTION combination of these approaches.
The end products vary depending on the conversion
technology utilized. Focusing on biofuels as the end-product
O
poses challenges due to the high volumes and relative low
CH -O-C R
2 1 values associated with bulk commodities like gasoline and
O diesel fuels.
CH-O-C R
2
O
CH -O-C R
2 3
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.
Most challenges in extraction are associated with the
industrial scale up of integrated extraction systems.
While many analytical techniques exist, optimizing
extraction systems that consume less energy than
contained in the algal products is a challenge due to the
high energy needs associated with both handling and
drying algal biomass as well as separating out desirable
products. Some algal biomass production processes are
investigating options to bypass extraction, though these are
also subject to a number of unique scale-up challenges.
End Uses:
• Biodiesel • Biogas
• Renewable Hydrocarbons • Co-products

• Alcohols (e.g., animal feed, fertilizers,
industrial enzymes,
bioplastics, and surfactants)
REGULATIONS AND STANDARDS
Systems and Techno-Economic Analysis: GuiDdeinvge ltohpem Reenste Paarcthh Taonwd a r d a Commercially Viable Algal Biofuel Industry
BIOENERGY TECHNOLOGIES OFFICE
Contents
1. Overview of Algal Biofuels and Work from the U.S. Deparment of Energy ...........................1
1.1 History of the Review .............................................................................................................................................1
1.2 America’s Energy Challenges ............................................................................................................................1
Algal Feedstocks .....................................................................................................................................................2
1.3 A History of Domestic Algal Biofuels Development ...............................................................................3
Early Work to 1996 .................................................................................................................................................3
Research from 1996 to 2008 ..............................................................................................................................6
Algae Program Research Consortia (2009–2014) .....................................................................................6
Integrated Biorefineries ........................................................................................................................................8
Research Since 2012 ..............................................................................................................................................8
Regional Algal Feedstock Testbed ...................................................................................................................9
1.4 Algae-to-Biofuels and Products: Opportunity and Challenges Ahead .........................................10
References ................................................................................................................................................................11
2. Algal Biomass, Genetics, and Development ........................................................................14
2.1 Strain Isolation, Screening, and Selection .................................................................................................14
Isolation and Characterization of Naturally Occurring Algae .............................................................14
Screening Criteria and Methods......................................................................................................................15
Selecting Algal Model Systems for Study ...................................................................................................15
2.2 Algal Physiology and Biochemistry ............................................................................................................16
Photosynthesis, Light Utilization, and Carbon-Concentrating Mechanisms .................................17
Carbon Partitioning and Metabolism ............................................................................................................19
Algal Carbohydrates ...........................................................................................................................................20
Lipid Synthesis and Regulation .......................................................................................................................21
Biohydrogen ..........................................................................................................................................................24
2.3 Algal Biotechnology .........................................................................................................................................25
Enabling Technologies: Omics Approaches and Bioinformatics .......................................................25
Algal Genetic Engineering ................................................................................................................................28
Applications of Biotechnology to Algal Bioenergy ................................................................................32
Considerations of Genetic Modifications ....................................................................................................34
2.4 Macroalgae ..........................................................................................................................................................35
References ..............................................................................................................................................................39
3. Resources for Algal Research ...............................................................................................57
3.1 Algae Testbed Services and Real-Time Data Collection and Sharing ............................................57
3.2 Role of Culture Collections as National Algae Data Resource Centers ........................................57
3.3 Omics Databases ...............................................................................................................................................58
3.4 Genetic Toolboxes .............................................................................................................................................59
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BIOENERGY TECHNOLOGIES OFFICE
3.5 Growth Prediction Tools .................................................................................................................................59
3.6 Standardization and Biomass Analysis Resources ..............................................................................59
3.7 Lab-Scale Performance Tools .......................................................................................................................60
References ..............................................................................................................................................................62
4. Algal Cultivation ..................................................................................................................64
4.1 Cultivation Pathways ........................................................................................................................................64
Photoautotrophic vs. Heterotrophic .............................................................................................................64
Open vs. Closed Systems ..................................................................................................................................64
4.2 Cultivation Scale-Up Challenges .................................................................................................................66
Process-Development-Scale and Integrated Biorefinery “Lessons Learned” ..............................66
Stability of Large-Scale Cultures ...................................................................................................................67
Scalable System Designs: Maintaining Productivity ..............................................................................68
Nutrient Sources, Sustainability, and Management ...............................................................................69
Water Management, Conservation, and Sustainability .........................................................................70
4.3 Macroalgae ...........................................................................................................................................................71
References ..............................................................................................................................................................73
5. Harvesting and Dewatering .................................................................................................80
5.1 Harvesting and Dewatering ............................................................................................................................80
Ultrasonic Harvesting .........................................................................................................................................80
Filtration ..................................................................................................................................................................80
Flocculation and Sedimentation .....................................................................................................................81
Flocculation and Dissolved Air Flotation ....................................................................................................82
Centrifugation .......................................................................................................................................................82
Other Harvesting Techniques ..........................................................................................................................82
5.2 Drying ....................................................................................................................................................................82
Microalgae Drying Methods .............................................................................................................................82
5.3 Systems Engineering .......................................................................................................................................83
Preliminary Look at Energy Balance ............................................................................................................83
5.4 Approaches for Macroalgae .........................................................................................................................84
Harvesting ...............................................................................................................................................................84
Preprocessing ........................................................................................................................................................84
References ..............................................................................................................................................................85
6. Extraction of Algae ...............................................................................................................89
6.1 Lipid Separations and Extractions from Algae .......................................................................................89
6.2 Physical Methods of Extraction and/or Cellular Biomass Pretreatment .....................................90
Microwave Assisted ..............................................................................................................................................91
Pulsed Electric Field .............................................................................................................................................91
Ultrasonic ................................................................................................................................................................92
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BIOENERGY TECHNOLOGIES OFFICE
6.3 Catalytic Methods of Extraction and/or Cellular Biomass Pretreatment ...................................92
Acid/Base Hydrolysis .........................................................................................................................................92
6.4 Solvent-Based Extraction of Lipids ...........................................................................................................93
Solvent Extraction ...............................................................................................................................................93
Accelerated Solvent Extraction ......................................................................................................................94
Mixed Solvent Extraction ..................................................................................................................................94
Supercritical Fluid Extraction ..........................................................................................................................95
Switchable Solvents ............................................................................................................................................95
6.5 Comparison of Extraction Methods ...........................................................................................................96
6.6 Lipid Extraction Challenges ..........................................................................................................................97
Presence of Water Associated with the Biomass....................................................................................97
Separation of Desired Extracts from Solvent Stream ............................................................................97
Process Integration .............................................................................................................................................97
References ..............................................................................................................................................................98
7. Algal Biofuel Conversion Technologies ..............................................................................103
7.1 Production of Biofuels from Algae through Heterotrophic Fermentation
or by Direct Secretion ......................................................................................................................................103
Alcohols .................................................................................................................................................................104
Alkanes ...................................................................................................................................................................104
7.2 Processing of Whole Algae ..........................................................................................................................104
Pyrolysis .................................................................................................................................................................104
Gasification ...........................................................................................................................................................105
Anaerobic Digestion of Whole Algae .........................................................................................................106
Supercritical Processing ...................................................................................................................................107
Hydrothermal Processing ................................................................................................................................107
7.3 Conversion of Extracted Algae ..................................................................................................................109
Chemical Transesterification............................................................................................................................110
Direct Transesterification of Lipids into Fatty Acid Methyl Esters .....................................................111
Carbohydrate and Protein Fermentation ...................................................................................................112
Biochemical (Enzymatic) Conversion ..........................................................................................................113
Catalytic Transesterification.............................................................................................................................114
Conversion to Renewable Diesel, Gasoline, and Jet Fuel .....................................................................115
7.4 Processing of Algal Residuals after Extraction ......................................................................................116
References ..............................................................................................................................................................117
8. Commercial Products .........................................................................................................123
8.1 Commercial Products from Microalgae and Cyanobacteria ............................................................123
Food and Feed .....................................................................................................................................................124
Polyunsaturated Fatty Acids ..........................................................................................................................124
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