GREEN POWER FROM ALGAE Reducing dependence on fossil fuels_20251013_224002_0000.pdf
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Oct 13, 2025
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About This Presentation
Concept of Greenpower From Algae focusing mainly on Bioengineering.
Slide Content
GREEN POWER FROM ALGAE :
Reducing dependence on
fossil fuels Taskeen Khalid, Anika Ruhela, Sudha Kumari, Aryan, Nainika Rosy. M.Sc. Botany 1st Year
Reducing dependence on
fossil fuels Taskeen Khalid, Anika Ruhela, Sudha Kumari, Aryan, Nainika Rosy. M.Sc. Botany 1st Year
Introduction
HOW CAN WE MANIPULATE
ALGAE to produce the
greenpower?
Approaches that can be
used to produce
greenpower from algae:List of
contents
References
HOW CAN WE MANIPULATE
ALGAE to produce the
greenpower?
Approaches that can be
used to produce
greenpower from algae:List of
contents
References
Introduction
The world today faces an alarming dependence on fossil fuels such as
coal, petroleum, and natural
gas for meeting its energy demands. The continuous extraction and
burning of fossil fuels release large amounts of carbon dioxide
(CO₂), sulfur oxides, nitrogen oxides, and particulate matter into the
atmosphere, leading to global
warming, air pollution, and climate change. The rise in global temperatures,
melting of polar ice caps,
and frequent extreme weather events are clear consequences of this
overdependence.
Moreover, fossil fuels are finite and depleting rapidly.
Many countries, including India, rely heavily on fuel imports, which strains
the economy and increases
vulnerability to global price fluctuations and geopolitical tensions. Thus,
there is an urgent need to
explore renewable, sustainable, and environment-friendly energy sources.
The world today faces an alarming dependence on fossil fuels such as
coal, petroleum, and natural
gas for meeting its energy demands. The continuous extraction and
burning of fossil fuels release large amounts of carbon dioxide
(CO₂), sulfur oxides, nitrogen oxides, and particulate matter into the
atmosphere, leading to global
warming, air pollution, and climate change. The rise in global temperatures,
melting of polar ice caps,
and frequent extreme weather events are clear consequences of this
overdependence.
Moreover, fossil fuels are finite and depleting rapidly.
Many countries, including India, rely heavily on fuel imports, which strains
the economy and increases
vulnerability to global price fluctuations and geopolitical tensions. Thus,
there is an urgent need to
explore renewable, sustainable, and environment-friendly energy sources.
One promising alternative emerging from biological
research is green algae. Algae are photosynthetic
organisms capable of converting sunlight, water, and
carbon dioxide into biomass rich in lipids,
carbohydrates, and proteins. These lipids can be
converted into biofuels such as biodiesel,
bioethanol, and biogas, providing a clean and renewable
substitute for petroleum-based fuels.
research is green algae. Algae are photosynthetic
organisms capable of converting sunlight, water, and
carbon dioxide into biomass rich in lipids,
carbohydrates, and proteins. These lipids can be
converted into biofuels such as biodiesel,
bioethanol, and biogas, providing a clean and renewable
substitute for petroleum-based fuels.
Algae
are preferred over terrestrial plants for green power production due to their superior productivity,
highlighted by an unmatched lipid yield per unit area, efficient CO₂ capture, and ability to utilize non-
arable land and wastewater. The qualities of algae are fundamentally supported by their robust
cellular systems, such as the efficient reactive oxygen species (ROS) degradation system that
enables rapid growth under intense light. During photosynthesis and metabolic processes, organisms
inevitably produce reactive oxygen
species like hydrogen peroxide and superoxide radicals. These are highly reactive molecules that
cause oxidative stress, damaging. proteins, lipids, and DNA, ultimately, inhibiting growth and
productivity. Algae possess a remarkably robust and diverse arsenal of antioxidant enzymes (e.g..
Super-oxide dismutase, catalase, peroxidase) and non-enzyme antioxidants (eg., carotenoids like
astaxanthin, vitamin C and E). On the other hand, plants have sophisticated antioxidant systems, but
they are distributed across complex tissues (leaves, roots, stems). The overall rate of ROS
degradation and signaling is slower and more localized in plants as compared to algae.
WHY ALGAE, NOT PLANTS?
are preferred over terrestrial plants for green power production due to their superior productivity,
highlighted by an unmatched lipid yield per unit area, efficient CO₂ capture, and ability to utilize non-
arable land and wastewater. The qualities of algae are fundamentally supported by their robust
cellular systems, such as the efficient reactive oxygen species (ROS) degradation system that
enables rapid growth under intense light. During photosynthesis and metabolic processes, organisms
inevitably produce reactive oxygen
species like hydrogen peroxide and superoxide radicals. These are highly reactive molecules that
cause oxidative stress, damaging. proteins, lipids, and DNA, ultimately, inhibiting growth and
productivity. Algae possess a remarkably robust and diverse arsenal of antioxidant enzymes (e.g..
Super-oxide dismutase, catalase, peroxidase) and non-enzyme antioxidants (eg., carotenoids like
astaxanthin, vitamin C and E). On the other hand, plants have sophisticated antioxidant systems, but
they are distributed across complex tissues (leaves, roots, stems). The overall rate of ROS
degradation and signaling is slower and more localized in plants as compared to algae.
WHY ALGAE, NOT PLANTS?
HOW CAN WE MANIPULATE ALGAE to
produce the greenpower? Since algae possess natural advantages such as
rapid growth rate, high photosynthetic efficiency,
and high lipid content, it makes them the ideal
candidates for biofuel production. Through modern
biotechnological tools scientists are optimizing
algae to yield more biomass, enhance lipid
synthesis,
and reduce production costs.
produce the greenpower? Since algae possess natural advantages such as
rapid growth rate, high photosynthetic efficiency,
and high lipid content, it makes them the ideal
candidates for biofuel production. Through modern
biotechnological tools scientists are optimizing
algae to yield more biomass, enhance lipid
synthesis,
and reduce production costs.
HOW? Selection & Genetic
improvement of
algal strains Optimized algal
cultivation
systems
Harvesting and
Biofuel conversion
Sustainable energy
integration in Biofuel
production
improvement of
algal strains Optimized algal
cultivation
systems
Harvesting and
Biofuel conversion
Sustainable energy
integration in Biofuel
production
HOW Bioengineering Works? Bioengineering focuses on modifying metabolic pathways within algal cells to increase the
accumulation of oils and fatty acids that can be converted into Biodiesel. For example, genes involved
in Lipid biosynthesis are overexpressed, while those responsible for Carbohydrate formation are
downregulated, directing more carbon flow towards lipid production. Genetic engineering also
enables algae to tolerate stress conditions such as high salinity or variable light intensity, allowing them to
grow efficiently in non-arable lands or wastewater systems. Another area of innovation is the
development of Optimized cultivation systems, including photobioreactors and open pond systems,
designed to maximize sunlight capture and CO₂ utilization. These systems not only enhance algal
growth but also help in carbon sequestration, reducing greenhouse gas emissions. Additionally,
bioengineered algae can be tailored to produce multiple energy products like biodiesel, bioethanol,
biogas, and hydrogen thus creating an integrated biorefinery approach for sustainable energy
generation.
Advances in Synthetic biology have also made it possible to design new algal strains that produce
specific biofuels directly, eliminating the need for complex chemical conversion processes. Combined
with efficient harvesting and extraction technologies, these developments are making algal biofuels a
viable alternative to fossil fuels.
accumulation of oils and fatty acids that can be converted into Biodiesel. For example, genes involved
in Lipid biosynthesis are overexpressed, while those responsible for Carbohydrate formation are
downregulated, directing more carbon flow towards lipid production. Genetic engineering also
enables algae to tolerate stress conditions such as high salinity or variable light intensity, allowing them to
grow efficiently in non-arable lands or wastewater systems. Another area of innovation is the
development of Optimized cultivation systems, including photobioreactors and open pond systems,
designed to maximize sunlight capture and CO₂ utilization. These systems not only enhance algal
growth but also help in carbon sequestration, reducing greenhouse gas emissions. Additionally,
bioengineered algae can be tailored to produce multiple energy products like biodiesel, bioethanol,
biogas, and hydrogen thus creating an integrated biorefinery approach for sustainable energy
generation.
Advances in Synthetic biology have also made it possible to design new algal strains that produce
specific biofuels directly, eliminating the need for complex chemical conversion processes. Combined
with efficient harvesting and extraction technologies, these developments are making algal biofuels a
viable alternative to fossil fuels.
To unlock the full potential of algae as a viable source of greenpower, a primary focus lies in the direct and
precise enhancement of the organisms themselves. This begins with the strategic improvement of high-
performing algal strains, a process aimed at amplifying key traits such as lipid yield, growth
rate, and environmental resilience. Through advanced bioengineering approaches including rigorous strain
screening and targeted genetic tools like CRISPR/Cas9, scientists are systematically
reprogramming algal metabolism to divert carbon towards lipid accumulation and fortify the cells
against industrial-scale stresses, there by creating optimized 'bio-factories' for sustainable energy
production. 1. Selection and Genetic
Improvement of Algal strains:
precise enhancement of the organisms themselves. This begins with the strategic improvement of high-
performing algal strains, a process aimed at amplifying key traits such as lipid yield, growth
rate, and environmental resilience. Through advanced bioengineering approaches including rigorous strain
screening and targeted genetic tools like CRISPR/Cas9, scientists are systematically
reprogramming algal metabolism to divert carbon towards lipid accumulation and fortify the cells
against industrial-scale stresses, there by creating optimized 'bio-factories' for sustainable energy
production. 1. Selection and Genetic
Improvement of Algal strains:
Fig 1. Genetically engineered microalgae for enhanced
biofuel production. (Korkhovoy V, et al., 2016)
biofuel production. (Korkhovoy V, et al., 2016)
A. Strain Screening
Bioengineering Approaches
B. Genetic modification using various techniques:
C.Stress Engineering
Bioengineering Approaches
B. Genetic modification using various techniques:
C.Stress Engineering
A. Strain Screening
Bioengineering Approaches
B. Genetic modification using various techniques:
C.Stress Engineering Fig. 2 The schematic of data and resource driven strategy for microalgal bioengineering. (A) Resource
generation and enrichment: The high-throughput technologies, intense computation and bioinformatic
analysis, and the extensive research interest on microalgae can generate high-quality curated data. The
genomic and transcriptomic data of model organisms provides a basic understanding of the
biosynthetic pathway. This imperative information is aided by proteomics and metabolomics that
offers functional insights for bioproduct discovery in microalgae. Also, the metabolomic data can be
implemented to novel microbial isolates with limited genomic and transcriptomic information. (B)
Strain development and resource refinement: The leads from metabolic models and the use of state-
of-the-art technologies, such as genome-editing and high-throughput variant selection can be used for
microalgae strain development. Often the metabolic flux shifts of the mutants implies an organism's
evolution to optimize flux rearrangement. The objective of the flux balance shift can be biomass
production or enhanced production of desired product. Moreover, the information obtained from fine-
tuned modeling and genomic-editing experiments create resource avenues for further discoveries.
Bioengineering Approaches
B. Genetic modification using various techniques:
C.Stress Engineering Fig. 2 The schematic of data and resource driven strategy for microalgal bioengineering. (A) Resource
generation and enrichment: The high-throughput technologies, intense computation and bioinformatic
analysis, and the extensive research interest on microalgae can generate high-quality curated data. The
genomic and transcriptomic data of model organisms provides a basic understanding of the
biosynthetic pathway. This imperative information is aided by proteomics and metabolomics that
offers functional insights for bioproduct discovery in microalgae. Also, the metabolomic data can be
implemented to novel microbial isolates with limited genomic and transcriptomic information. (B)
Strain development and resource refinement: The leads from metabolic models and the use of state-
of-the-art technologies, such as genome-editing and high-throughput variant selection can be used for
microalgae strain development. Often the metabolic flux shifts of the mutants implies an organism's
evolution to optimize flux rearrangement. The objective of the flux balance shift can be biomass
production or enhanced production of desired product. Moreover, the information obtained from fine-
tuned modeling and genomic-editing experiments create resource avenues for further discoveries.
A. Strain Screening
Bioengineering Approaches
The ideal algae strain for greenpower generation must efficiently convert solar energy and CO₂ into
high-density energy molecules (Like lipids for biodiesel or carbohydrates for bioethanol) while being
tough enough to survive in large-scale open outdoor cultivation. Not all lipids are equal. For
biodiesel,
lipids should have a high proportion of C16-C18 fatty acids (eg, palmitic, stearic, oleic acid) for good
fuel properties. Gas chromatography (GC) after transesterification of lipids to Fatty Acid Methyl
Esters (FAMEs) is done for screening. Alternatively, Lipophilic fluorescent dyes like Nile Red or
BODIPY with fluorescence microscopy or flow cytometry can be used. This allows for rapid, high-
throughput screening of thousands of cells.
Bioengineering Approaches
The ideal algae strain for greenpower generation must efficiently convert solar energy and CO₂ into
high-density energy molecules (Like lipids for biodiesel or carbohydrates for bioethanol) while being
tough enough to survive in large-scale open outdoor cultivation. Not all lipids are equal. For
biodiesel,
lipids should have a high proportion of C16-C18 fatty acids (eg, palmitic, stearic, oleic acid) for good
fuel properties. Gas chromatography (GC) after transesterification of lipids to Fatty Acid Methyl
Esters (FAMEs) is done for screening. Alternatively, Lipophilic fluorescent dyes like Nile Red or
BODIPY with fluorescence microscopy or flow cytometry can be used. This allows for rapid, high-
throughput screening of thousands of cells.
a) Diatoms (eg., Phaeodactylum tricornutum) - High lipid content, unique silica cell wall.
Notable Algal Strains for
greenpower generation are:
Image: Light Micrographs of Phaeodactylum tricornutum
Notable Algal Strains for
greenpower generation are:
Image: Light Micrographs of Phaeodactylum tricornutum
a) Diatoms (eg., Phaeodactylum tricornutum) - High lipid content, unique silica cell wall.
b) Green algae e.g.,
Chlorella vulgaris
Scenedesmus obliquus
Nannochloropsis spp.
Chlamydomonas reinhardtii
(`fruitfly` of the algal world)
Fig. 3 - Image: Chlamydomonas reinhardtii
Location: Creek in Oder valley 100 km north east of Berlin (Germany)
Date: 01 May 2011
Photographer: Wolfgang Bettighofer, www.protisten.de
Copyright: © Wolfgang Bettighofer
Notable Algal Strains for
greenpower generation are:
Wild-type strains of Chlamydomonas reinhardtii have moderate
lipid content, but they are excellent
candidates for genetic engineering to redirect carbon flux from
starch to lipids (e.g., by knocking out
starch synthesis genes).
b) Green algae e.g.,
Chlorella vulgaris
Scenedesmus obliquus
Nannochloropsis spp.
Chlamydomonas reinhardtii
(`fruitfly` of the algal world)
Fig. 3 - Image: Chlamydomonas reinhardtii
Location: Creek in Oder valley 100 km north east of Berlin (Germany)
Date: 01 May 2011
Photographer: Wolfgang Bettighofer, www.protisten.de
Copyright: © Wolfgang Bettighofer
Notable Algal Strains for
greenpower generation are:
Wild-type strains of Chlamydomonas reinhardtii have moderate
lipid content, but they are excellent
candidates for genetic engineering to redirect carbon flux from
starch to lipids (e.g., by knocking out
starch synthesis genes).
c) Cyanobacteria (Blue-Green Algae):
such as Synechocystis spp.
Notable Algal Strains for
greenpower generation are:
These can be engineered to directly secrete hydrocarbons,
bypassing the need for cell disruption.Fig. 4: Cells of Synechocystis sp. PCC 6803. a Cryo-SEM
of highpressure frozen and freeze-fractured cells.
Some cells fractured along the plane of the outer
membrane and the cytoplasmic membrane (white
asterisks).
such as Synechocystis spp.
Notable Algal Strains for
greenpower generation are:
These can be engineered to directly secrete hydrocarbons,
bypassing the need for cell disruption.Fig. 4: Cells of Synechocystis sp. PCC 6803. a Cryo-SEM
of highpressure frozen and freeze-fractured cells.
Some cells fractured along the plane of the outer
membrane and the cytoplasmic membrane (white
asterisks).
B. Genetic modification using various techniques:a ) Biolistic particle delivery:- "Gene gun method"
b) Electroporation:- Algal cells are subjected to a brief, high-
voltage electric pulse, which temporarily
creates pores in the cell membrane, allowing the foreign DNA to
enter.
c) Agrobacterium :- Mediated transformation
b) Electroporation:- Algal cells are subjected to a brief, high-
voltage electric pulse, which temporarily
creates pores in the cell membrane, allowing the foreign DNA to
enter.
c) Agrobacterium :- Mediated transformation
Fig. 5:
Overview of tools/techniques used in
microalgae genetic engineering
Overview of tools/techniques used in
microalgae genetic engineering
Using CRISPR/Cas9 tool, bioengineers can carry out knockout
of starch synthesis gene (STA6,
STA7) to divert carbon flow towards lipid accumulation in
green alga Chlamydomonas reinhardtii. The
mutant algae with knocked out STA6 gene could not make
starch at all and completely lacked ADP-
glucose pyrophosphorylase (AGPase) enzyme activity, which
controls how much starch is made.
The STA6 gene makes a protein (about 50 kDa) that resembles
the small subunit of plant AGPase ;
Another gene STA1 makes the large subunit (53kDa).
Together these two subunits (large + small) form the active
enzyme that make ADP-Glucose, the
building block of Starch
d) CRISPR/Cas9 :-
of starch synthesis gene (STA6,
STA7) to divert carbon flow towards lipid accumulation in
green alga Chlamydomonas reinhardtii. The
mutant algae with knocked out STA6 gene could not make
starch at all and completely lacked ADP-
glucose pyrophosphorylase (AGPase) enzyme activity, which
controls how much starch is made.
The STA6 gene makes a protein (about 50 kDa) that resembles
the small subunit of plant AGPase ;
Another gene STA1 makes the large subunit (53kDa).
Together these two subunits (large + small) form the active
enzyme that make ADP-Glucose, the
building block of Starch
d) CRISPR/Cas9 :-
Overexpression of Lipid
biosynthesis genes - Algae naturally
make lipids (mainly triacylglycerols
TAGs) for energy storage. But under
normal growth conditions, lipid yield
is Low. To make more lipids,
scientists enhance key enzymes and
pathways that convent carbon into
fatty acids and TAGs. d) CRISPR/Cas9 :-
biosynthesis genes - Algae naturally
make lipids (mainly triacylglycerols
TAGs) for energy storage. But under
normal growth conditions, lipid yield
is Low. To make more lipids,
scientists enhance key enzymes and
pathways that convent carbon into
fatty acids and TAGs. d) CRISPR/Cas9 :-
Common targets for overexpression include:
i) ACCase (Acetyl-CoA-Carboxylase): Converts
acetyl-CoA to malonyl-CoA (first step in Fatty
Acid Synthesis).
Fig. 6: Fatty acid Synthesis Cycle
i) ACCase (Acetyl-CoA-Carboxylase): Converts
acetyl-CoA to malonyl-CoA (first step in Fatty
Acid Synthesis).
Fig. 6: Fatty acid Synthesis Cycle
Common targets for overexpression include:
ii) DGAT
(Diacylglycerol acyltransferase) :- final enzyme
in TAG Synthesis.
Fig. 7: TAG synthesis
ii) DGAT
(Diacylglycerol acyltransferase) :- final enzyme
in TAG Synthesis.
Fig. 7: TAG synthesis
Common targets for overexpression include:
iii) PDAT (phospholipid: diacylglycerol
acyltransferase) :- Alternative route to TAG
formation.
Fig. 8: PDAT pathway
iii) PDAT (phospholipid: diacylglycerol
acyltransferase) :- Alternative route to TAG
formation.
Fig. 8: PDAT pathway
Common targets for overexpression include:
iv, GPD1/GPAT/LPAAT:- Glycerol Backbone
and acyl Chain assemblyFig. 9: Generalized scheme for triacylglycerol (TAG) biosynthesis via the
glycerol phosphate pathway. Glycerol-3-phosphate acyltransferase (GPAT)
Lyso-phosphatidic acid acyltransferase (LPAAT)
Phosphatidic acid phosphatase (PAP)
Diacylglycerol acyltransferase (DGAT).
iv, GPD1/GPAT/LPAAT:- Glycerol Backbone
and acyl Chain assemblyFig. 9: Generalized scheme for triacylglycerol (TAG) biosynthesis via the
glycerol phosphate pathway. Glycerol-3-phosphate acyltransferase (GPAT)
Lyso-phosphatidic acid acyltransferase (LPAAT)
Phosphatidic acid phosphatase (PAP)
Diacylglycerol acyltransferase (DGAT).
Common targets for overexpression include:
v, Transcription factors (e.g.,
DOF, bZIP, WRINKLED-Like) :-
Turn on groups of lipid genes.
v, Transcription factors (e.g.,
DOF, bZIP, WRINKLED-Like) :-
Turn on groups of lipid genes.
C.Stress Engineering
Algae naturally increase lipid
accumulation under Stress (like
Salinity or Nitrogen deprivation),
but
growth drops sharply, so overall
productivity reduces. The goal of
stress engineering is to
manipulate algal strains in such a
way that they:
a) Survive harsh conditions (salinity & nutrient stress).
b) Continue to grow reasonably well
c) Still accumulate high lipids, proteins or pigments.
Fig.10: Genetically modifying the algae to produce Higher
Biomass, Low oxidative damage Algae
Algae naturally increase lipid
accumulation under Stress (like
Salinity or Nitrogen deprivation),
but
growth drops sharply, so overall
productivity reduces. The goal of
stress engineering is to
manipulate algal strains in such a
way that they:
a) Survive harsh conditions (salinity & nutrient stress).
b) Continue to grow reasonably well
c) Still accumulate high lipids, proteins or pigments.
Fig.10: Genetically modifying the algae to produce Higher
Biomass, Low oxidative damage Algae
The global demand for sustainable and renewable energy sources has made microalgae one of
the most promising bioresources for biofuel production. Algae can produce large amounts of
lipids, carbohydrates, and proteins, which can be converted into biodiesel, bioethanol, biogas,
or biohydrogen.
However, large-scale algae cultivation faces challenges such as low productivity,
contamination, and high cost. Hence, developing optimized cultivation systems is essential
for enhancing algal biomass yield and improving biofuel economics.
Optimized systems combine biological engineering, environmental control, and technological
automation to maximize algal growth, lipid content, and sustainability. 2. Optimized Algal
Cultivation Systems
the most promising bioresources for biofuel production. Algae can produce large amounts of
lipids, carbohydrates, and proteins, which can be converted into biodiesel, bioethanol, biogas,
or biohydrogen.
However, large-scale algae cultivation faces challenges such as low productivity,
contamination, and high cost. Hence, developing optimized cultivation systems is essential
for enhancing algal biomass yield and improving biofuel economics.
Optimized systems combine biological engineering, environmental control, and technological
automation to maximize algal growth, lipid content, and sustainability. 2. Optimized Algal
Cultivation Systems
To maximize algal biomass productivity per unit area or volume.
To enhance lipid or carbohydrate accumulation for biofuel conversion.
To minimize water, nutrient, and energy inputs.
To allow year-round cultivation with minimal contamination.
To integrate with waste CO₂ or wastewater for circular bioeconomy models. Objectives of Optimized Algal Cultivation Systems
To enhance lipid or carbohydrate accumulation for biofuel conversion.
To minimize water, nutrient, and energy inputs.
To allow year-round cultivation with minimal contamination.
To integrate with waste CO₂ or wastewater for circular bioeconomy models. Objectives of Optimized Algal Cultivation Systems
1. Open Pond Culture Systems Cultivation Strategies for Algae
Pond is usually between 1-100cm deep. The most
common open pond culture system
consists of
A pond in the shape of a raceway and the liquid is
circulated around the pond by a paddle
wheel.
This system mimics the way algae grow in their natural
environment. The raceways are
typically
Made from poured concrete, or they are simply dug into
the earth and lined with a plastic
liner.
These raceways vary from a few feet in length to
thousands of meters. Due to scalability
and
Low cost of building these systems, they are the most
popular cultivation system
Fig. 11
Pond is usually between 1-100cm deep. The most
common open pond culture system
consists of
A pond in the shape of a raceway and the liquid is
circulated around the pond by a paddle
wheel.
This system mimics the way algae grow in their natural
environment. The raceways are
typically
Made from poured concrete, or they are simply dug into
the earth and lined with a plastic
liner.
These raceways vary from a few feet in length to
thousands of meters. Due to scalability
and
Low cost of building these systems, they are the most
popular cultivation system
Fig. 11
2. Closed Photobioreactors Closed photobioreactors (PBR) were established to overcome the major issues associated
With open-pond cultures, including low cell densities, contamination issues, evaporation,
Environment regulation and high land requirements. PBRs are very versatile and can be
located
Both indoors with artificial light and outdoors with natural light. PBRs are very attractive
due to
The previously stated benefits, however compared to an open-pond system PBR’s require
higher
Capital investments and have issues with scalability. Many unique PBRs have been
developed;
With open-pond cultures, including low cell densities, contamination issues, evaporation,
Environment regulation and high land requirements. PBRs are very versatile and can be
located
Both indoors with artificial light and outdoors with natural light. PBRs are very attractive
due to
The previously stated benefits, however compared to an open-pond system PBR’s require
higher
Capital investments and have issues with scalability. Many unique PBRs have been
developed;
3. Tubular PBR The most widely used PBR is of tubular design, which has a
number of clear transparent
Tubes, composed of either glass or plastic (11). The culture
is circulated through the tubes
where it is exposed to light for photosynthesis, and then
returns to a reservoir. The tubes are
usually 10
Cm or less in diameter, which allows for sufficient sunlight
penetration. The algal biomass
is
Prevented from settling by maintaining highly turbulent
flow within the reactor with either a
Mechanical pump or an airlift pump (11). These tubular
reactors can be run either vertically
or
Horizontally. Many of these systems require a gas exchange
chamber to reduce the
elevated
Dissolved O2 levels in the liquid. Fig. 12
number of clear transparent
Tubes, composed of either glass or plastic (11). The culture
is circulated through the tubes
where it is exposed to light for photosynthesis, and then
returns to a reservoir. The tubes are
usually 10
Cm or less in diameter, which allows for sufficient sunlight
penetration. The algal biomass
is
Prevented from settling by maintaining highly turbulent
flow within the reactor with either a
Mechanical pump or an airlift pump (11). These tubular
reactors can be run either vertically
or
Horizontally. Many of these systems require a gas exchange
chamber to reduce the
elevated
Dissolved O2 levels in the liquid. Fig. 12
3. Tubular PBR The most widely used PBR is of tubular design, which has a
number of clear transparent
Tubes, composed of either glass or plastic (11). The culture
is circulated through the tubes
where it is exposed to light for photosynthesis, and then
returns to a reservoir. The tubes are
usually 10
Cm or less in diameter, which allows for sufficient sunlight
penetration. The algal biomass
is
Prevented from settling by maintaining highly turbulent
flow within the reactor with either a
Mechanical pump or an airlift pump (11). These tubular
reactors can be run either vertically
or
Horizontally. Many of these systems require a gas exchange
chamber to reduce the
elevated
Dissolved O2 levels in the liquid. Fig. 13
number of clear transparent
Tubes, composed of either glass or plastic (11). The culture
is circulated through the tubes
where it is exposed to light for photosynthesis, and then
returns to a reservoir. The tubes are
usually 10
Cm or less in diameter, which allows for sufficient sunlight
penetration. The algal biomass
is
Prevented from settling by maintaining highly turbulent
flow within the reactor with either a
Mechanical pump or an airlift pump (11). These tubular
reactors can be run either vertically
or
Horizontally. Many of these systems require a gas exchange
chamber to reduce the
elevated
Dissolved O2 levels in the liquid. Fig. 13
4. Helical PBR Helical PBRs are composed of parallel transparent tubes
coiled around a cylinder. The
Helical shape is effective in increasing the surface area
sunlight is able to reach. This in
turn can
Increase productivity. These systems increase productivity
compared to tubular PBR’s but
due to
The unique shape and increased cost, it has not been as
popular. Fig. 14
coiled around a cylinder. The
Helical shape is effective in increasing the surface area
sunlight is able to reach. This in
turn can
Increase productivity. These systems increase productivity
compared to tubular PBR’s but
due to
The unique shape and increased cost, it has not been as
popular. Fig. 14
5.Airlift PBR An airlift PBR can be a simple vertical cylinder made
out of transparent glass or plastic. On the bottom of
the tube is an air inlet. This air inlet bubbles air
through the column,
which
Provides mixing and gas exchange. These systems
have aerial productivity compared to
algae
Grown in a similar tubular reactor. Fig. 15
out of transparent glass or plastic. On the bottom of
the tube is an air inlet. This air inlet bubbles air
through the column,
which
Provides mixing and gas exchange. These systems
have aerial productivity compared to
algae
Grown in a similar tubular reactor. Fig. 15
6. Flat Panel (Flat Plate) PBR Flat panels, also known as flat plate PBRs, are essentially
rectangular boxes composed of
Translucent glass or plastic. Air is bubbled from the bottom, which
provides sufficient
mixing and
Gas transfer. These reactors can have baffles running horizontally
inside the reactor to aid
mixing and gas exchange efficiencies. Because of the increased
surface area for light to reach
algae
Cells, flat panel PBRs can have significantly higher productivity
than an open-pond system.
For
Example, in one study, cell densities were compared between a flat
panel PBR and an open
pond
Using the algae S. platensis; the flat panel PBR produced 2.15 g L -1
d-1
), and under similar
Conditions in an open pond produced 0.15 g L-1 Fig. 16
rectangular boxes composed of
Translucent glass or plastic. Air is bubbled from the bottom, which
provides sufficient
mixing and
Gas transfer. These reactors can have baffles running horizontally
inside the reactor to aid
mixing and gas exchange efficiencies. Because of the increased
surface area for light to reach
algae
Cells, flat panel PBRs can have significantly higher productivity
than an open-pond system.
For
Example, in one study, cell densities were compared between a flat
panel PBR and an open
pond
Using the algae S. platensis; the flat panel PBR produced 2.15 g L -1
d-1
), and under similar
Conditions in an open pond produced 0.15 g L-1 Fig. 16
Heterotrophic Culture SystemsThe majority of algae gets energy from light and is strictly phototrophic. Some algae
Species are able to utilize organic substrates as an energy source. Generally. Heterotrophic
algae
Cultivation is cultivated in fermentators where a high degree of culture manipulation can
be
Performed. This cultivation method can have many benefits; for example, it can utilize
well-
Established fermentation technologies, high degree of process control, good production
Repeatability, elimination of light limitation, and lower harvesting costs. (16)
In most cases, heterotrophically grown algae can contain a much higher lipid
Concentration than phototrophically grown algae of the same species. One study showed
that
Chlorella sp. Cells accumulated 55.2% lipids when heterotrophically grown and only 14.6%
When phototrophically grown (17). Although heterotrophic algae culture usually results in
algal biomass with higher lipid content, the fermentation vessels are usually very
expensive. For
this
Reason. Heterotrophically grown algae has not been considered feasible for biodiesel
production
But has shown great promise in producing high value products such as omega-3 fatty
acids
Species are able to utilize organic substrates as an energy source. Generally. Heterotrophic
algae
Cultivation is cultivated in fermentators where a high degree of culture manipulation can
be
Performed. This cultivation method can have many benefits; for example, it can utilize
well-
Established fermentation technologies, high degree of process control, good production
Repeatability, elimination of light limitation, and lower harvesting costs. (16)
In most cases, heterotrophically grown algae can contain a much higher lipid
Concentration than phototrophically grown algae of the same species. One study showed
that
Chlorella sp. Cells accumulated 55.2% lipids when heterotrophically grown and only 14.6%
When phototrophically grown (17). Although heterotrophic algae culture usually results in
algal biomass with higher lipid content, the fermentation vessels are usually very
expensive. For
this
Reason. Heterotrophically grown algae has not been considered feasible for biodiesel
production
But has shown great promise in producing high value products such as omega-3 fatty
acids
Attached/biofilm-Based Culture SystemsAn attachment/biofilm-based algae culture system is
very different than other cultivation
Systems. In most cultivation systems, such as open
ponds or PBRs, microalgae cells are suspended in the
liquid and the cultivation system is designed to keep
these cells from
attaching
Or settling on surfaces. Biofilm-based culture systems
are the complete opposite. These
systems Encourage algae to settle or attach on a
desired surface. By allowing cells to
attach, algae
Naturally concentrates and are easily harvested. Thus,
the costly and energy intensive
harvesting
Practices can be removed. Algal biomass harvested
from an attached surface has water
content Fig. 17
very different than other cultivation
Systems. In most cultivation systems, such as open
ponds or PBRs, microalgae cells are suspended in the
liquid and the cultivation system is designed to keep
these cells from
attaching
Or settling on surfaces. Biofilm-based culture systems
are the complete opposite. These
systems Encourage algae to settle or attach on a
desired surface. By allowing cells to
attach, algae
Naturally concentrates and are easily harvested. Thus,
the costly and energy intensive
harvesting
Practices can be removed. Algal biomass harvested
from an attached surface has water
content Fig. 17
Harvesting /recovery or solid–liquid separation:-
Harvesting is the process of separating microalgal biomass from
the large volume of culture medium in which it grows. After
harvesting, the concentrated biomass is further dewatered and
dried or processed for downstream conversion (oil extraction,
biochemical conversion, or direct combustion).
Need of Harvesting:- Microalgal cultures are very dilute
(typical cell solids 0.1–1 g/L in ponds/photo bioreactors), so you
must concentrate them to obtain usable biomass. 3. Harvesting and biofuel
conversion
Harvesting is the process of separating microalgal biomass from
the large volume of culture medium in which it grows. After
harvesting, the concentrated biomass is further dewatered and
dried or processed for downstream conversion (oil extraction,
biochemical conversion, or direct combustion).
Need of Harvesting:- Microalgal cultures are very dilute
(typical cell solids 0.1–1 g/L in ponds/photo bioreactors), so you
must concentrate them to obtain usable biomass. 3. Harvesting and biofuel
conversion
Downstream conversion steps (lipid extraction, hydrothermal
liquefaction, anaerobic digestion, transesterification) require
higher solids (often >10% w/w or dry biomass). Efficient
harvest/thickening reduces energy and solvent needs
downstream. Harvesting impacts overall process cost and life-cycle energy use
— it’s one of the major techno-economic hurdles for algal
biofuels.
liquefaction, anaerobic digestion, transesterification) require
higher solids (often >10% w/w or dry biomass). Efficient
harvest/thickening reduces energy and solvent needs
downstream. Harvesting impacts overall process cost and life-cycle energy use
— it’s one of the major techno-economic hurdles for algal
biofuels.
Harvesting /recovery or solid–liquid separation:-
Harvesting is the process of separating microalgal biomass from
the large volume of culture medium in which it grows. After
harvesting, the concentrated biomass is further dewatered and
dried or processed for downstream conversion (oil extraction,
biochemical conversion, or direct combustion).
Need of Harvesting:- Microalgal cultures are very dilute
(typical cell solids 0.1–1 g/L in ponds/photo bioreactors), so you
must concentrate them to obtain usable biomass.
Downstream conversion steps (lipid extraction, hydrothermal
liquefaction, anaerobic digestion, transesterification) require
higher solids (often >10% w/w or dry biomass). Efficient
harvest/thickening reduces energy and solvent needs
downstream.
Fig. 18
Harvesting is the process of separating microalgal biomass from
the large volume of culture medium in which it grows. After
harvesting, the concentrated biomass is further dewatered and
dried or processed for downstream conversion (oil extraction,
biochemical conversion, or direct combustion).
Need of Harvesting:- Microalgal cultures are very dilute
(typical cell solids 0.1–1 g/L in ponds/photo bioreactors), so you
must concentrate them to obtain usable biomass.
Downstream conversion steps (lipid extraction, hydrothermal
liquefaction, anaerobic digestion, transesterification) require
higher solids (often >10% w/w or dry biomass). Efficient
harvest/thickening reduces energy and solvent needs
downstream.
Fig. 18
Harvesting method
• Flocculation/coagulation:- Flocculation is a widely used
approach to harvest microalgal biomass.
• In this process, scattered units in the medium are
accumulated together and these particles are settled down
using various kinds of chemicals and bio-flocculants.
• Example:- calcium oxide, polydillymethylammonium,
chitosan etc… ..
• Bioflocculation:- This method uses natural processes to
cause algae to aggregate.
• Auto-flocculation:-Microalgae spontaneously form flocs
without external agents, often due to changes in the culture
medium.
• Chemical flocculation:- This technique involves
adding chemical agents to the microalgae culture.
• Mechanism: The chemical flocculants, which are often
positively charged, neutralize the negative surface charge of
the microalgae, causing them to clump together. Harvesting methodFig. 19
• Flocculation/coagulation:- Flocculation is a widely used
approach to harvest microalgal biomass.
• In this process, scattered units in the medium are
accumulated together and these particles are settled down
using various kinds of chemicals and bio-flocculants.
• Example:- calcium oxide, polydillymethylammonium,
chitosan etc… ..
• Bioflocculation:- This method uses natural processes to
cause algae to aggregate.
• Auto-flocculation:-Microalgae spontaneously form flocs
without external agents, often due to changes in the culture
medium.
• Chemical flocculation:- This technique involves
adding chemical agents to the microalgae culture.
• Mechanism: The chemical flocculants, which are often
positively charged, neutralize the negative surface charge of
the microalgae, causing them to clump together. Harvesting methodFig. 19
Sedimentation is a method to
harvest microalgae by allowing
cells to settle out of a liquid
suspension under gravity, often
after being induced to clump
together (flocculation) to
improve efficiency.
• This process is attractive for its
low cost and simplicity, though
its efficiency is limited by the
small size and slow settling
rate of many microalgae
species, especially in dilute
solutions. Sedimentation / GravityFig. 20
harvest microalgae by allowing
cells to settle out of a liquid
suspension under gravity, often
after being induced to clump
together (flocculation) to
improve efficiency.
• This process is attractive for its
low cost and simplicity, though
its efficiency is limited by the
small size and slow settling
rate of many microalgae
species, especially in dilute
solutions. Sedimentation / GravityFig. 20
• Flotation is an effective and energy-efficient
method for harvesting microalgae by using
bubbles to lift the cells to the surface.
• Microalgae cells are trapped on microair
bubbles and float at the surface of water [69].
Generally, the flotation efficiency is
dependent on the size of the created bubble:
nanobubbles (<1 μm), microbubbles (1–
999 μm), and fine bubbles (1–2 mm). Flotation
method for harvesting microalgae by using
bubbles to lift the cells to the surface.
• Microalgae cells are trapped on microair
bubbles and float at the surface of water [69].
Generally, the flotation efficiency is
dependent on the size of the created bubble:
nanobubbles (<1 μm), microbubbles (1–
999 μm), and fine bubbles (1–2 mm). Flotation
• Centrifugation operation separates microalgae cells from the culture
media based on each component’s density and particle size using
centrifugal force .
• This technique has high cell harvesting efficiency, but the process is time
consuming and energy intensive.
• Moreover, high gravitational force used in centrifugation might cause
cellular damage making it unfavorable for certain applications since the
sensitive nutrients might be lost .
• Several types of centrifugal systems have been used in the industry; these
include disk stack centrifuges, perforated basket centrifuges,
imperforated basket centrifuges, decanters, and hydro-cyclones . Centrifugation
media based on each component’s density and particle size using
centrifugal force .
• This technique has high cell harvesting efficiency, but the process is time
consuming and energy intensive.
• Moreover, high gravitational force used in centrifugation might cause
cellular damage making it unfavorable for certain applications since the
sensitive nutrients might be lost .
• Several types of centrifugal systems have been used in the industry; these
include disk stack centrifuges, perforated basket centrifuges,
imperforated basket centrifuges, decanters, and hydro-cyclones . Centrifugation
• Filtration process utilizes a semipermeable
membrane which can retain microalgae on the
membrane while allowing the liquid media to pass
through, leaving the algae biomass behind to be
collected .
• This method can harvest high concentration of cell
from the medium, and the varying pore size of the
filter membrane enables the system to suit the need
of different microalgae and are able to handle the
more delicate species which are prone to damage due
to shearing. However, this method is very prone to
fouling and clogging and therefore requires frequent
change of fresh filter or membrane that might
contribute significantly to its processing cost. Filtration
membrane which can retain microalgae on the
membrane while allowing the liquid media to pass
through, leaving the algae biomass behind to be
collected .
• This method can harvest high concentration of cell
from the medium, and the varying pore size of the
filter membrane enables the system to suit the need
of different microalgae and are able to handle the
more delicate species which are prone to damage due
to shearing. However, this method is very prone to
fouling and clogging and therefore requires frequent
change of fresh filter or membrane that might
contribute significantly to its processing cost. Filtration
• High lipid-producing strains can be converted into biodiesel (FAME) by
transesterification of extracted oils. Other routes: hydrothermal liquefaction (HTL)
producing biocrude, pyrolysis, gasification, or anaerobic digestion to biogas.
Some algal-derived fuels are drop-in compatible with existing refineries after
upgrading (hydrotreating), making them potentially compatible with current
transport infrastructure.
• High areal productivity: certain microalgae can produce more oil per unit land
area than terrestrial oil crops.
• Non-arable land / non-potable water: can use saline/brackish/wastewater and
marginal land, avoiding food-vs-fuel conflicts.
• CO₂ mitigation opportunity: algae fixes CO₂ during growth; coupling algal systems
to CO₂ emitters can utilize flue gas.
• Multiple product streams: lipids → fuels; proteins/carbohydrates → animal feed or
biogas; residuals → fertilizers/co-products — improving overall economics and
GHG balance. Green power from Algae
transesterification of extracted oils. Other routes: hydrothermal liquefaction (HTL)
producing biocrude, pyrolysis, gasification, or anaerobic digestion to biogas.
Some algal-derived fuels are drop-in compatible with existing refineries after
upgrading (hydrotreating), making them potentially compatible with current
transport infrastructure.
• High areal productivity: certain microalgae can produce more oil per unit land
area than terrestrial oil crops.
• Non-arable land / non-potable water: can use saline/brackish/wastewater and
marginal land, avoiding food-vs-fuel conflicts.
• CO₂ mitigation opportunity: algae fixes CO₂ during growth; coupling algal systems
to CO₂ emitters can utilize flue gas.
• Multiple product streams: lipids → fuels; proteins/carbohydrates → animal feed or
biogas; residuals → fertilizers/co-products — improving overall economics and
GHG balance. Green power from Algae
The most prevalent way of making biofuel from microalgae is to
produce biodiesel from algal lipids (oil) through
transesterificaiton compared to plant-based oils, algae oil
has
relatively high carbon and hydrogen contents and low oxygen
content. These characteristics
make algae an attractive biodiesel feedstock because they lead
to a fuel with high energy content, low viscosity, and low density.
In most cases, biodiesel can be directly combusted in a
standard diesel engine without the issue of blending with regular
diesel. Transesterification of alcoholsand lipids are the chemical
reaction required to produce biodiesel, with glycerol being
produced as a byproduct .
Total lipid levels are commonly the most important factor in
considering the applicability of algae biomass for biodiesel
production. However, considering only the total lipid content is
misleading as only the neutral lipids are converted to biodiesel
during transesterificaiton. The best algal feedstock for biodiesel
production is a biomass high in neutral lipids. Biodiesel
produce biodiesel from algal lipids (oil) through
transesterificaiton compared to plant-based oils, algae oil
has
relatively high carbon and hydrogen contents and low oxygen
content. These characteristics
make algae an attractive biodiesel feedstock because they lead
to a fuel with high energy content, low viscosity, and low density.
In most cases, biodiesel can be directly combusted in a
standard diesel engine without the issue of blending with regular
diesel. Transesterification of alcoholsand lipids are the chemical
reaction required to produce biodiesel, with glycerol being
produced as a byproduct .
Total lipid levels are commonly the most important factor in
considering the applicability of algae biomass for biodiesel
production. However, considering only the total lipid content is
misleading as only the neutral lipids are converted to biodiesel
during transesterificaiton. The best algal feedstock for biodiesel
production is a biomass high in neutral lipids. Biodiesel
• Certain strains of algae are capable of producing high
levels of carbohydrates, such as starch, which is an
ideal fermentative substrate. High ethanol productivity
can be accomplished from fermentation of algae
biomass. The production of ethanol from algae is done
by breaking the cells via mechanical means followed by
dissolving carbohydrates with either water or solvent.
• Once the carbohydrates are extracted, traditional
methods, such as scarification with enzymes and
fermentation with bacteria or yeasts, are used to
produce ethanol. Finally, a distillation step
concentrates the ethanol.
• In addition to producing ethanol via fermentation of
algal starch, ethanol can be also be produced directly
by algae. This process includes genetically modifying
an algae species so it secretes ethanol into the
medium. Ethanol
levels of carbohydrates, such as starch, which is an
ideal fermentative substrate. High ethanol productivity
can be accomplished from fermentation of algae
biomass. The production of ethanol from algae is done
by breaking the cells via mechanical means followed by
dissolving carbohydrates with either water or solvent.
• Once the carbohydrates are extracted, traditional
methods, such as scarification with enzymes and
fermentation with bacteria or yeasts, are used to
produce ethanol. Finally, a distillation step
concentrates the ethanol.
• In addition to producing ethanol via fermentation of
algal starch, ethanol can be also be produced directly
by algae. This process includes genetically modifying
an algae species so it secretes ethanol into the
medium. Ethanol
• Anaerobic digestion is widely used to treat various carbon-rich wastes,
converting them into biogas composed of methane and CO₂. This biogas serves
as a valuable resource for generating heat and electricity. The CO₂ produced
can be recycled back into an algae culture system, enhancing sustainability.
Using raw algal biomass for biogas production eliminates the need for
expensive biomass-harvesting and oil-extraction processes, significantly
reducing the overall production costs associated with algal biodiesel.
Additionally, anaerobic digestion of the cell residues after lipid extraction offers
a viable method to utilize residual biomass. However, this process only
converts about 50-70% of the material and typically produces lower-value
products, limiting its economic potential. Biogas and Syngas
converting them into biogas composed of methane and CO₂. This biogas serves
as a valuable resource for generating heat and electricity. The CO₂ produced
can be recycled back into an algae culture system, enhancing sustainability.
Using raw algal biomass for biogas production eliminates the need for
expensive biomass-harvesting and oil-extraction processes, significantly
reducing the overall production costs associated with algal biodiesel.
Additionally, anaerobic digestion of the cell residues after lipid extraction offers
a viable method to utilize residual biomass. However, this process only
converts about 50-70% of the material and typically produces lower-value
products, limiting its economic potential. Biogas and Syngas
• Animal Feed:- In the U.S., most livestock feed comes from corn or soybean, but
microalgae are gaining attention as a sustainable alternative. Algae can grow on non-
fertile land and often have higher protein content than corn or soy. In 2007, about 30% of
cultivated algae were used for animal feed. With large-scale algae production for
biofuels, the remaining algal biomass could be repurposed for feed, especially in poultry
and aquaculture. As wild fish populations decline and aquaculture expands, algae offer
a valuable protein and lipid source to replace fish meal, reducing dependence on
capture fisheries.
• Human Consumption:- Microalgae were first eaten in China about 2000 years ago during
famines.Today, they’re consumed as tablets, capsules, drinks, and snack ingredients.
Spirulina and Chlorella dominate global production for whole-cell consumption.The
largest facility is Earthrise Farms in California (440,000 m²).Most products use specific
algal compounds rather than whole cells. Common supplements include omega-3 fatty
acids and β-carotene. Dunaliella salina produces β-carotene; Nannochloropsis,
Phaeodactylum, and Nitzschia produce omega-3 (EPA).
Non-biofuel from Microalgae
microalgae are gaining attention as a sustainable alternative. Algae can grow on non-
fertile land and often have higher protein content than corn or soy. In 2007, about 30% of
cultivated algae were used for animal feed. With large-scale algae production for
biofuels, the remaining algal biomass could be repurposed for feed, especially in poultry
and aquaculture. As wild fish populations decline and aquaculture expands, algae offer
a valuable protein and lipid source to replace fish meal, reducing dependence on
capture fisheries.
• Human Consumption:- Microalgae were first eaten in China about 2000 years ago during
famines.Today, they’re consumed as tablets, capsules, drinks, and snack ingredients.
Spirulina and Chlorella dominate global production for whole-cell consumption.The
largest facility is Earthrise Farms in California (440,000 m²).Most products use specific
algal compounds rather than whole cells. Common supplements include omega-3 fatty
acids and β-carotene. Dunaliella salina produces β-carotene; Nannochloropsis,
Phaeodactylum, and Nitzschia produce omega-3 (EPA).
Non-biofuel from Microalgae
Comprehensive insights into
sustainable energy optimization in
algal biofuel systems4. Sustainable Energy Integration in
Biofuel Production from Algae
sustainable energy optimization in
algal biofuel systems4. Sustainable Energy Integration in
Biofuel Production from Algae
• Algae-based biofuels, classified as third-generation biofuels, represent a highly promising pathway
toward
achieving a sustainable, low-carbon energy future.
• Algae possess significant advantages over terrestrial crops due to their rapid growth rate, high lipid
content, and ability to thrive on non-arable land using saline or wastewater resources.
• These characteristics allow for biofuel production without competing with food crops or freshwater
resources.
• Despite these benefits, large-scale algal biofuel production faces challenges related to high
operational
energy demands, especially in cultivation, harvesting, drying, and extraction stages.
• Sustainable energy integration through renewable resources and process optimization is crucial to
improving economic viability and reducing the carbon footprint. Introduction to Algal Biofuel
Systems
toward
achieving a sustainable, low-carbon energy future.
• Algae possess significant advantages over terrestrial crops due to their rapid growth rate, high lipid
content, and ability to thrive on non-arable land using saline or wastewater resources.
• These characteristics allow for biofuel production without competing with food crops or freshwater
resources.
• Despite these benefits, large-scale algal biofuel production faces challenges related to high
operational
energy demands, especially in cultivation, harvesting, drying, and extraction stages.
• Sustainable energy integration through renewable resources and process optimization is crucial to
improving economic viability and reducing the carbon footprint. Introduction to Algal Biofuel
Systems
Introduction to Algal Biofuel
Systems
Systems
• Cultivation: Energy is required for mixing, aeration, CO₂ injection, and maintaining optimal temperature in
ponds or PBRs. While open raceway ponds are cheaper, they have lower yields compared to
photobioreactors (PBRs), which require higher energy inputs.
• Harvesting and Dewatering: Algal cells exist in dilute suspension, necessitating energy-intensive separation
using centrifugation, filtration, or flocculation techniques. These steps often account for 20–30% of total
production costs.
• Drying: Reducing moisture content for oil extraction consumes significant energy. Thermal drying or spray
drying is common but energy-intensive; alternatives like solar drying or wet processing are being explored.
• Oil Extraction and Conversion: Solvent extraction, supercritical CO₂, or enzymatic methods are employed
to extract lipids, which are converted via transesterification into biodiesel or upgraded to other fuels.
Energy-Intensive Stages in Algae
Biofuel Production
ponds or PBRs. While open raceway ponds are cheaper, they have lower yields compared to
photobioreactors (PBRs), which require higher energy inputs.
• Harvesting and Dewatering: Algal cells exist in dilute suspension, necessitating energy-intensive separation
using centrifugation, filtration, or flocculation techniques. These steps often account for 20–30% of total
production costs.
• Drying: Reducing moisture content for oil extraction consumes significant energy. Thermal drying or spray
drying is common but energy-intensive; alternatives like solar drying or wet processing are being explored.
• Oil Extraction and Conversion: Solvent extraction, supercritical CO₂, or enzymatic methods are employed
to extract lipids, which are converted via transesterification into biodiesel or upgraded to other fuels.
Energy-Intensive Stages in Algae
Biofuel Production
Energy-Intensive Stages in Algae
Biofuel Production
Raceway Pond
Biofuel Production
Raceway Pond
• Solar Energy: Photovoltaic (PV) systems can provide direct power for paddlewheels, pumps, lighting, and
monitoring systems. Solar thermal collectors can also supply low-grade heat for temperature regulation in
cultivation tanks.
• Wind Energy: Coastal or open-area facilities can integrate wind turbines to power dewatering, circulation,
and CO₂ delivery systems.
• Waste Heat Recovery: Industrial waste heat from factories or power plants can maintain culture
temperatures, eliminating the need for fossil-fuel-based heating systems.
• Biogas & Cogeneration (CHP): Residual biomass after lipid extraction can undergo anaerobic digestion to
produce biogas, which can be utilized in CHP units to generate electricity and heat for the facility.
• Geothermal and Ocean Thermal Energy: Can be harnessed for stable and continuous thermal regulation,
especially in colder climates. Integration of Renewable Energy in
Algal Biofuel Systems
monitoring systems. Solar thermal collectors can also supply low-grade heat for temperature regulation in
cultivation tanks.
• Wind Energy: Coastal or open-area facilities can integrate wind turbines to power dewatering, circulation,
and CO₂ delivery systems.
• Waste Heat Recovery: Industrial waste heat from factories or power plants can maintain culture
temperatures, eliminating the need for fossil-fuel-based heating systems.
• Biogas & Cogeneration (CHP): Residual biomass after lipid extraction can undergo anaerobic digestion to
produce biogas, which can be utilized in CHP units to generate electricity and heat for the facility.
• Geothermal and Ocean Thermal Energy: Can be harnessed for stable and continuous thermal regulation,
especially in colder climates. Integration of Renewable Energy in
Algal Biofuel Systems
• Co-location: Integrating algae facilities near CO₂ emitters (like cement or power plants) allows direct
utilization of flue gases and waste heat, significantly lowering energy and operational costs.
• Gravity-Based Flow Systems: Designing cultivation and dewatering setups that leverage gravity reduces
the need for pumps.
• Low-Energy Harvesting: Techniques such as bio-flocculation and natural sedimentation eliminate
mechanical separation needs.
• Membrane Filtration: Energy-efficient filtration systems can outperform centrifugation in terms of energy
savings and recovery rates.
• Hydrothermal Liquefaction (HTL): Converts wet algal biomass directly into bio-crude, bypassing drying and
achieving higher EROI.
• Nutrient Recycling: Nitrogen and phosphorus from digested residues can be reused in algae cultivation,
closing nutrient loops. Process Optimization and Energy
Efficiency Measures
utilization of flue gases and waste heat, significantly lowering energy and operational costs.
• Gravity-Based Flow Systems: Designing cultivation and dewatering setups that leverage gravity reduces
the need for pumps.
• Low-Energy Harvesting: Techniques such as bio-flocculation and natural sedimentation eliminate
mechanical separation needs.
• Membrane Filtration: Energy-efficient filtration systems can outperform centrifugation in terms of energy
savings and recovery rates.
• Hydrothermal Liquefaction (HTL): Converts wet algal biomass directly into bio-crude, bypassing drying and
achieving higher EROI.
• Nutrient Recycling: Nitrogen and phosphorus from digested residues can be reused in algae cultivation,
closing nutrient loops. Process Optimization and Energy
Efficiency Measures
Process Optimization and Energy
Efficiency Measures
Efficiency Measures
• Hybrid Renewable Systems: Combining solar, wind, and biogas sources ensures consistent power supply
and grid independence.
• Smart Control Systems: IoT and AI-based automation optimize aeration, illumination, and nutrient delivery
in real-time, reducing waste.
• Circular Economy Design: Integrates waste CO₂ and nutrients from wastewater treatment, creating a
closed-loop biorefinery model.
• Energy Storage Solutions: Batteries and thermal storage stabilize renewable energy fluctuations, ensuring
steady operation.
• Life Cycle Assessment (LCA): Comprehensive LCA identifies drying and harvesting as energy hotspots and
evaluates total GHG emissions.
• With renewable integration, algae biofuel systems can transition toward carbon neutrality or even carbon
negativity, enhancing global energy sustainability. Advanced Energy Integration and
Life Cycle Assessment (LCA)
and grid independence.
• Smart Control Systems: IoT and AI-based automation optimize aeration, illumination, and nutrient delivery
in real-time, reducing waste.
• Circular Economy Design: Integrates waste CO₂ and nutrients from wastewater treatment, creating a
closed-loop biorefinery model.
• Energy Storage Solutions: Batteries and thermal storage stabilize renewable energy fluctuations, ensuring
steady operation.
• Life Cycle Assessment (LCA): Comprehensive LCA identifies drying and harvesting as energy hotspots and
evaluates total GHG emissions.
• With renewable integration, algae biofuel systems can transition toward carbon neutrality or even carbon
negativity, enhancing global energy sustainability. Advanced Energy Integration and
Life Cycle Assessment (LCA)
(i) Reduction of CO₂ Emissions-
High Carbon Sequestration Capacity: Microalgae can fix approximately 1.8 kg of CO₂ per
kilogram of dry biomass due to their rapid growth rate and high photosynthetic efficiency (up to
3–5% solar energy conversion efficiency compared to ~1% in terrestrial plants).
Mitigation of Greenhouse Gases: Large-scale algal cultivation systems can be integrated with
industrial CO₂ emitters such as power plants and cement factories to capture flue gases directly.
Studies show up to 80–90% reduction in CO₂ concentration from industrial exhaust when coupled
with photo-bioreactors.
Carbon-Neutral Biofuel: The CO₂ released during algal biofuel combustion is nearly equivalent to
that absorbed during algal growth, creating a closed carbon cycle and ensuring a net-zero carbon
emission profile.
Quantitative Potential: According to the U.S. Department of Energy (DOE), if algae-based biofuels
replaced conventional fossil fuels, global CO₂ emissions could be reduced by up to 3–5 billion
tons annually.
5. Socioeconomic and Environmental
Impacts of Algal Bioenergy
High Carbon Sequestration Capacity: Microalgae can fix approximately 1.8 kg of CO₂ per
kilogram of dry biomass due to their rapid growth rate and high photosynthetic efficiency (up to
3–5% solar energy conversion efficiency compared to ~1% in terrestrial plants).
Mitigation of Greenhouse Gases: Large-scale algal cultivation systems can be integrated with
industrial CO₂ emitters such as power plants and cement factories to capture flue gases directly.
Studies show up to 80–90% reduction in CO₂ concentration from industrial exhaust when coupled
with photo-bioreactors.
Carbon-Neutral Biofuel: The CO₂ released during algal biofuel combustion is nearly equivalent to
that absorbed during algal growth, creating a closed carbon cycle and ensuring a net-zero carbon
emission profile.
Quantitative Potential: According to the U.S. Department of Energy (DOE), if algae-based biofuels
replaced conventional fossil fuels, global CO₂ emissions could be reduced by up to 3–5 billion
tons annually.
5. Socioeconomic and Environmental
Impacts of Algal Bioenergy
(ii) High Land-Use Efficiency-
Superior Productivity: Microalgae can produce 15–30 times more oil per hectare compared to
oilseed crops like soybean, rapeseed, or palm. Their annual lipid productivity may reach
20,000–30,000 liters of oil per hectare, depending on species and cultivation system.
Non-Arable Land Utilization: Algae can grow on non-fertile, saline, or wastewater environments,
avoiding competition with agricultural land use for food crops.
Minimal Land Footprint: Compared to terrestrial biofuel crops, microalgae require 10–50 times less
land area for the same bioenergy yield. This is particularly significant for densely populated
countries like India, where land availability is limited.
Continuous Cultivation: Unlike seasonal crops, microalgae can be cultivated
Superior Productivity: Microalgae can produce 15–30 times more oil per hectare compared to
oilseed crops like soybean, rapeseed, or palm. Their annual lipid productivity may reach
20,000–30,000 liters of oil per hectare, depending on species and cultivation system.
Non-Arable Land Utilization: Algae can grow on non-fertile, saline, or wastewater environments,
avoiding competition with agricultural land use for food crops.
Minimal Land Footprint: Compared to terrestrial biofuel crops, microalgae require 10–50 times less
land area for the same bioenergy yield. This is particularly significant for densely populated
countries like India, where land availability is limited.
Continuous Cultivation: Unlike seasonal crops, microalgae can be cultivated
(iii) Rural Employment and Economic Development-
Job Creation in Multiple Sectors: Establishing algal biofuel facilities supports employment in
cultivation, harvesting, processing, biorefinery operations, quality control, and logistics.
Rural and Coastal Area Empowerment: Algae cultivation can be established near coastal regions,
saline lands, or wastewater treatment plants, Inclusive Growth: By integrating small-scale algae farms with c
models, rural populations can participate in green entrepreneurship and bioenergy value chains.
Skill Development and Research Opportunities: Expansion of algal biotechnology stimulates
training programs, research collaborations, and academic-industry linkages, enhancing technical
knowledge in developing nations.
Economic Diversification: The algal biofuel sector promotes diversification from fossil fuel
dependency to renewable and bio-based economics, strengthening national energy security.
Job Creation in Multiple Sectors: Establishing algal biofuel facilities supports employment in
cultivation, harvesting, processing, biorefinery operations, quality control, and logistics.
Rural and Coastal Area Empowerment: Algae cultivation can be established near coastal regions,
saline lands, or wastewater treatment plants, Inclusive Growth: By integrating small-scale algae farms with c
models, rural populations can participate in green entrepreneurship and bioenergy value chains.
Skill Development and Research Opportunities: Expansion of algal biotechnology stimulates
training programs, research collaborations, and academic-industry linkages, enhancing technical
knowledge in developing nations.
Economic Diversification: The algal biofuel sector promotes diversification from fossil fuel
dependency to renewable and bio-based economics, strengthening national energy security.
(iv) Contribution to the Circular Economy-
Wastewater Treatment Integration: Microalgae effectively utilize nutrients (N and P) from
municipal and industrial wastewaters, acting as a natural bio-remediation agent. They can remove
up to 80–90% nitrogen and 50–80% phosphorus, reducing eutrophication risks.
CO₂ Recycling: Algal photobioreactors can use flue gases from factories as a CO₂ source,
transforming waste carbon into biomass, thereby contributing to industrial decarbonization.
Resource Recovery and By-products: After lipid extraction, the residual algal biomass (rich in
protein, carbohydrates, and minerals) can be converted into:
→ Animal feed and aquafeed
→ Biofertilizers and Compost
→ Bioplastics, pigments, and pharmaceuticals
Zero Waste Biorefinery Concept: The algal biorefinery approach ensures complete utilization of
biomass, achieving a closed-loop production system with minimal waste and maximum value
generation.
Energy-Water-Nutrient Nexus: Algal bioenergy systems optimize resource use by linking
wastewater treatment, CO₂ fixation, and renewable fuel output, a prime model of sustainable
circular bioeconomy.
Wastewater Treatment Integration: Microalgae effectively utilize nutrients (N and P) from
municipal and industrial wastewaters, acting as a natural bio-remediation agent. They can remove
up to 80–90% nitrogen and 50–80% phosphorus, reducing eutrophication risks.
CO₂ Recycling: Algal photobioreactors can use flue gases from factories as a CO₂ source,
transforming waste carbon into biomass, thereby contributing to industrial decarbonization.
Resource Recovery and By-products: After lipid extraction, the residual algal biomass (rich in
protein, carbohydrates, and minerals) can be converted into:
→ Animal feed and aquafeed
→ Biofertilizers and Compost
→ Bioplastics, pigments, and pharmaceuticals
Zero Waste Biorefinery Concept: The algal biorefinery approach ensures complete utilization of
biomass, achieving a closed-loop production system with minimal waste and maximum value
generation.
Energy-Water-Nutrient Nexus: Algal bioenergy systems optimize resource use by linking
wastewater treatment, CO₂ fixation, and renewable fuel output, a prime model of sustainable
circular bioeconomy.
(vii) Economic Viability and Challenges-
Cost Considerations: Current production costs for algal biofuel range from $4–6 per litre,
mainly
due to harvesting, drying, and extraction expenses.
Integrating wastewater treatment and coproduct recovery can reduce costs by 40–60%.
Energy Return on Investment (EROI): Recent advancements in wet extraction technologies,
hydrothermal liquefaction, and genetically engineered strains are improving EROI towards
positive
margins (~2:1 ratio).
Policy and Market Drivers:
Carbon credit schemes, renewable energy subsidies, and green fuel mandates are crucial
for
promoting algal bioenergy commercialization.
Public-private partnerships (PPPs) and international collaborations are essential to scale
up production
Cost Considerations: Current production costs for algal biofuel range from $4–6 per litre,
mainly
due to harvesting, drying, and extraction expenses.
Integrating wastewater treatment and coproduct recovery can reduce costs by 40–60%.
Energy Return on Investment (EROI): Recent advancements in wet extraction technologies,
hydrothermal liquefaction, and genetically engineered strains are improving EROI towards
positive
margins (~2:1 ratio).
Policy and Market Drivers:
Carbon credit schemes, renewable energy subsidies, and green fuel mandates are crucial
for
promoting algal bioenergy commercialization.
Public-private partnerships (PPPs) and international collaborations are essential to scale
up production
(viii) Long-Term Outlook-
Research and Technological Innovations:
Genetic engineering, and metabolic pathway optimization in species like Nannochloropsis,
Botryococcus braunii, and Chlorella enhance lipid yield and stress tolerance.
Hybrid cultivation systems combining open ponds and photobioreactors improve cost efficiency
and scalability.
Integration with Other Renewable Technologies:
Algal bioenergy can complement solar and wind power, offering energy storage through biofuel
conversion.
Future energy models envision bioenergy-carbon capture and storage (BECCS) using algae for
negative emission technologies.
Sustainable Future Vision:
Widespread adoption of algal bioenergy will enable:
1. Cleaner air and reduced greenhouse emissions
2. Enhanced rural livelihoods
3. Efficient resource recycling
4. A global shift towards carbon-neutral economies.
Research and Technological Innovations:
Genetic engineering, and metabolic pathway optimization in species like Nannochloropsis,
Botryococcus braunii, and Chlorella enhance lipid yield and stress tolerance.
Hybrid cultivation systems combining open ponds and photobioreactors improve cost efficiency
and scalability.
Integration with Other Renewable Technologies:
Algal bioenergy can complement solar and wind power, offering energy storage through biofuel
conversion.
Future energy models envision bioenergy-carbon capture and storage (BECCS) using algae for
negative emission technologies.
Sustainable Future Vision:
Widespread adoption of algal bioenergy will enable:
1. Cleaner air and reduced greenhouse emissions
2. Enhanced rural livelihoods
3. Efficient resource recycling
4. A global shift towards carbon-neutral economies.
ConclusionWith the help of algae, we have a powerful and
sustainable way to reduce our dependence on
fossil fuels. Algae can produce clean biofuels
efficiently while absorbing carbon dioxide and
minimizing environmental harm. By investing in
algae-based energy, we take a major step toward a
greener, cleaner, and more sustainable future :
one where our planet can breathe easier and
thrive for generations to come.
sustainable way to reduce our dependence on
fossil fuels. Algae can produce clean biofuels
efficiently while absorbing carbon dioxide and
minimizing environmental harm. By investing in
algae-based energy, we take a major step toward a
greener, cleaner, and more sustainable future :
one where our planet can breathe easier and
thrive for generations to come.
REFERENCES: 1. Dhokane, D. et al. (2023). CRISPR-based bioengineering in microalgae for production of industrial
biomolecules. Frontiers in Bioengineering and Biotechnology.
2. Khoo, K.S. et al. (2023). Enhanced microalgal lipid production for biofuel using different strategies
including genetic modification of microalgae. Sci. Direct.
3. Figueroa-Torres, G. M., Pittman, J. K., & Theodoropoulos, C. — Optimisation of microalgal cultivation via
nutrient-enhanced strategies: the biorefinery paradigm (2021) ([BioMed Central][1])
4. Li, C. T. et al. — Optimization of nutrient utilization efficiency and algal cultivation under light/dark cycles.
(2023) ([PMC][2])
5. Gross, M. A. — Development and optimization of algal cultivation systems (PhD thesis) (2013)
6. Tan, J. S. et al., “A review on microalgae cultivation and harvesting”, PeerJ / PMC (2020). — Good general
review of cultivation and harvesting methods.
7. Deepa, P. et al., “A Review of the Harvesting Techniques of Microalgae”, Water (MDPI) (2023). — Clear survey of
harvesting methods and comparisons.
8. Hannon, M. et al., “Biofuels from algae: challenges and potential”, Biotechnology for Biofuels (2010) — often-
cited foundational review on potentials and hurdles.
9. Chisti, Y. (2007). Biodiesel from microalgae. Biotechnology Advances, 25(3), 294-306.
10. Sander, N., & Murthy, G. S. (2010). Life cycle assessment of microalgae biodiesel production. International
Journal of Life Cycle Assessment, 15(7), 646-656.
11. Zhou S., et al. Transforming Microalgae to Biofuel through Hydrothermal Liquefaction. Journal of Cleaner
Production; 2024.
12. De Souza, M.F. The potential of Microalgae for Carbon capture and Sequestration. (2024)
13. Demirbas, M.F. - Biofuels from algae for sustainable development (2011)
14. Beal,C.M. et al. Microalgae based wastewater treatment for developing... (2022, PMC)
biomolecules. Frontiers in Bioengineering and Biotechnology.
2. Khoo, K.S. et al. (2023). Enhanced microalgal lipid production for biofuel using different strategies
including genetic modification of microalgae. Sci. Direct.
3. Figueroa-Torres, G. M., Pittman, J. K., & Theodoropoulos, C. — Optimisation of microalgal cultivation via
nutrient-enhanced strategies: the biorefinery paradigm (2021) ([BioMed Central][1])
4. Li, C. T. et al. — Optimization of nutrient utilization efficiency and algal cultivation under light/dark cycles.
(2023) ([PMC][2])
5. Gross, M. A. — Development and optimization of algal cultivation systems (PhD thesis) (2013)
6. Tan, J. S. et al., “A review on microalgae cultivation and harvesting”, PeerJ / PMC (2020). — Good general
review of cultivation and harvesting methods.
7. Deepa, P. et al., “A Review of the Harvesting Techniques of Microalgae”, Water (MDPI) (2023). — Clear survey of
harvesting methods and comparisons.
8. Hannon, M. et al., “Biofuels from algae: challenges and potential”, Biotechnology for Biofuels (2010) — often-
cited foundational review on potentials and hurdles.
9. Chisti, Y. (2007). Biodiesel from microalgae. Biotechnology Advances, 25(3), 294-306.
10. Sander, N., & Murthy, G. S. (2010). Life cycle assessment of microalgae biodiesel production. International
Journal of Life Cycle Assessment, 15(7), 646-656.
11. Zhou S., et al. Transforming Microalgae to Biofuel through Hydrothermal Liquefaction. Journal of Cleaner
Production; 2024.
12. De Souza, M.F. The potential of Microalgae for Carbon capture and Sequestration. (2024)
13. Demirbas, M.F. - Biofuels from algae for sustainable development (2011)
14. Beal,C.M. et al. Microalgae based wastewater treatment for developing... (2022, PMC)
Content
Contribution : Slides 1-26 : Taskeen Khalid
Slides 27-37 : Anika Ruhela
Slides 38-50 : Sudha Kumari
Slides 51-56 : Aryan
Slides 57-62 : Nainika Rosy
All slides prepared by Taskeen Khalid
Contribution : Slides 1-26 : Taskeen Khalid
Slides 27-37 : Anika Ruhela
Slides 38-50 : Sudha Kumari
Slides 51-56 : Aryan
Slides 57-62 : Nainika Rosy
All slides prepared by Taskeen Khalid
Thank You
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