PHL Bio
Agro- and Biotechnologie
HELHa Agronomie
Biotechnologies
Projectmanagement
Final end report
The production of algae coupled to anaerobic
digestion in a closed vessel system for bio-fuel
production
Group 2:
Anke Hauben
Marine D'Aulisa
Dorien Janssens
Jessica Leonard
Bjorn Tordoor
Aline Verbist
Selien Sanchez
Projectleader:
B. Cornelis
O. Janssens
Summary
In this 21th century the environment is endangered by numerous human actions. One of the main
causes is the overuse of fossil fuels, which contributes to global warming. This is a big problem in the
whole energy story. A good solution for this could be the use of bio-fuels. Today there are already
many applications being used in practice. Corn, starch and sugar are the basic ingredients for these
bio-fuels, but an important disadvantage is that it is interfering with the food availability. Therefore
there had to be found an alternative, Algae.
The use of algae has a lot of advantages; it does not use agricultural land, it’s a very quick in
production and seawater can be used. There are different ways to use algae to produce bio-fuels.
Algae can be used to produce three different bio-fuels: methane in an anaerobic digestion system,
biodiesel with algae-oil and bio-hydrogen. Each with different production processes.
Because of the early stage of these processes there are still some disadvantages of algae. But many
companies are involved in this evolution.
2
The production of algae coupled to
anaerobic digestion in a closed
vessel system for bio-fuel production
The 21st century is marked by
one of its greatest challenges:
environmental protection and
energy production. Actually,
during a lot of years, the
relationship of 'environment'
and 'energy' were not friendly
co-existents. The environment
has suffered from the huge
production of energy in the
context of our modern society.
And the situation is going on!
That is why the scientists began
to reflect about ways to combine the protection of the
environment and the production
of energy. One of the ways is
using bio-fuels.
3
B
one, that is at the experimental stage.
io-fuels are solid, liquid
or gas fuel refined from
biomass. Unlike fossil fuels
(from petroleum, coal ...
simply said, natural resources) which are of limited
availability, bio-fuels are not
finite resources. Also biofuels respect the climate
much more than fossil fuels.
A recent UK government
publication (according to the
BBC news) declared that
bio-fuels consumption has
reduced
emissions
of
carbon dioxide « by 50-60%
compared to fossil fuels ».
That is another significant
reason to produce them.
Biomass contains all
living or dead biological
organisms. All organisms
are build of organic material, what is the main
product to produce biogas. Biomass could be
everything, like plants,
animals, waste products,
microorganisms or in this
article more specific algal
biomass.
The production of first
generation bio-fuels is characterized by mature commercial markets and well
understood
technologies.
They refer to fuels that have
been derived from sources
like starch, sugar, animals
fats and vegetable oil. But
these bio-fuels have many
disadvantages: They contribute to higher food prices
due to competition with food
crops and are expensive to
produce. Also they are accelerating the deforestation
and they do not meet their
claimed environmental benefits because the biomass
feedstock may not always
be produced sustainably.
The second generation of
bio-fuel aims to resolve the
problems
associated
to
the first generation.
The bio-fuels from the
second generation are derived from lignocellulosic
crops. Plants are made from
lignin and cellulose, second
generation technology allows these two components
of a plant to be split. After
that, the cellulose can be
fermented into alcohol much
in the same way as a first
generation bio-fuel.
The resources that can be
used are: low-cost crop and
forest residues, wood forest
wastes and
the organic
fraction of municipal solid
wastes.
(biofuel 2010;Nigam and
Singh 2009;Sims et al.
2008)
The last generation of biofuels is the third one. It is
this generation that relates
to this article because it is in
this one that algae bio fuel is
listed. This generation has
algae and biowaste as
resources.
(Nigam & Singh
2009;university college Cork
2010)
Unlike to the bio-fuel produced with soya, corn, palm, ...
(products of agriculture),
algae is not an aliment for
humans, so its production
does not deprive people of
food.
There is a diverse and long
list of bio-fuels, but in recent
years the term bio-fuel has
come to mean bio-ethanol or
biodiesel.
For their production, the
resources we can use are
for example: corn, soys,
beans, palm oil ... (crops)
but also wood chips, straw,
sewage... and algae.
(bbc 2007)
Three generations
We can divide the bio-fuels
between the ones from the
first generation, the ones
from the second and the
ones from the third. The first
and the second generations
are well known because
these bio-fuels are put into
practice. Meanwhile, there is
another generation, the third
Figure 1: Cartoon biofuels first generation
4
Moreover it does not compete with agriculture food
crops for land. In the same
way, algae do not depend
on a particular landscape or
soil type in order to grow, we
can even use abandoned
land or land that is not suitable for agriculture. We do
not need huge land to
cultivate algae either. For
instance: in the USA, only
3% of the cultivating land of
the country would be necessary to produce all the
bio-fuel for transport.
Also sea water can be used
for its culture and only a
small amount of it is required. Another important
advantage is the time
needed to cultivate and harvest algae. It is very quick. It
is one of the fastest growing
plant in the world. And the
yields in this production is
much higher than other
production types like soya or
corn. Algae contains much
more energy per unit of
weight than other crops.
About its impact on the
environment, bio-fuel from
algae is non-toxic, highly
biodegradable and contains
no sulfur. More-over, algae
plants could capture the CO2
and use it for their growth.
That is a very important
point for the environment.
Finally, the production of
microalgae generates byproducts that can be used
for a lot of things like for
example food for animals.
(Ningthoujam S.
2010;Renewable Energy
Sources 2010;Solix Biofuels
2010;university college Cork
2010;Wageningen UR
2010b)
Algae species
There are two kinds of algae
on the earth: the macroalgae and the microalgae.
We are only interested in the
microalgae in this article.
Microalgae are used for the
production of bio-fuel. Micro-
algae are, as the word says
it, microscopics (~ 1 to 50
µm).
A big majority of microalgae
produces unique molecules
like enzymes, antioxidants,
fatty acids, ... They are autotrofe unicellular organisms
so they are able to perform
photosynthesis.
They account for approximately half of the production
of the atmospheric oxygen
and they grow using the
greenhouse gas carbon
dioxide. Finally, microalgae
are the basis of the aquatic
food chain. All this shows
the
important
role
of
microalgae.
There are a lot of microalgae species. Their exact
number is unknown because
there are so many of them.
It is said that only 10 percent
of the species are identified.
For
the
moment,
the
registered species varies
between 25 and 40 thousands.
All the different species are
grouped in classes. Among
all these species, only some
of them, for the moment, are
used for the microalgal
biotechnology that consists
of (for the moment) bulks
chemicals, fine chemicals,
food and feed, end energy.
The three main ones are
spirulina, chlorella, Dunaliella. The chlorella and the
dunaliella are members of
the chlorophyceae class and
the spirulina is a member of
the cyano-phyceae class.
Microalgae have an enormous potential. There are
three ways to produce biofuels using microalgae.
Methane produced by
anaerobic digestion
Anaerobic digestion is the
production of biogas by
microorganisms in absence
of oxygen. If we look to the
digestion system of a cow
we see that anaerobic digestion is always been there
in nature. It’s only the last
decennia that humans started to use the methane bacteria to degrade organic material for the production of
bio-fuels. These methane
bacteria only works when
the substrate is mixed with
water (at least 50 %). (In
contrast to aerobic bacteria,
yeasts and fungi they cannot
exist in a solid phase.) Also
the methane bacteria are
very temperature sensitive.
They will only produce
methane if the temperature
is between 0°C and 70°C.
Normally they use organic
wastes or some other biodegradable organic material
but this article will only
Figure 2: Microscopic photo of microalgae
5
discuss the algal biomass
for this process.
(Oilgae 2010a)
The production of methane
by algae happens in an
anaerobic system. The methane will be produced from
any of the three constituents
of algae (carbohydrates,
proteins and fats). Normally
these large chains have to
be broken in smaller parts
by some chemical processes. But if we use algal
biomass, in fresh and preserved form, so it contains
enough
nutrients,
the
bacteria don’t need these
other processes, and they
can be broken down alone
by the bacteria.
An algal bioreactor is the
best option to produce the
algal biomass, because
microalgae can be grown in
large amounts (150 - 300
tons per ha per year). This
quantity of biomass can
theoretically yield 200,000 400,000 m of methane per
ha per year.(Oilgae 2010c)
Biogas plants consist of two
components: a digester (or
fermentation tank) and a gas
holder.
The digester is waterproof
container with the fermentable mixture. The gas
holder is normally an airproof steel container that, by
floating like a ball on the
fermentation mix, cuts off air
to the digester and collects
the gas generated. The
fermentation of algal biomass can be divided in 4
process stages: Hydrolysis,
Acidogenese, Acetogenesis,
Methanogenesis.
Biomass is mostly made up
of large organic polymers.
The bacteria in the anaerobic digester can’t use
these materials to produce
methane. The polymers
chains have to be cut in
smaller constituent parts by
hydrolysis. These smaller
parts are monomers like
sugars, amino acids and
fatty acids. In the second
stage acidogenesis, these
smaller
parts
will
be
converted into volatile fatty
acids (VFA’s). Acetogenesis
is the stage where acetogens bacteria produce
acetic acid, carbon dioxide
and hydrogen out of the
VFA’s. The last stage methanogenesis or biomethanation is the production of
methane by microbes called
methanogens. These bacteria convert acetate into
carbon dioxides and methane, while hydrogen is consumed.
(Biofuel technologies
2009;Wikipedia
2010a;Wikipedia
2010b;Wikipedia
2010d;Wikipedia 2010e)
Bio-diesel from
microalgae oil
Not only biogas can be
produced by algae, but also
liquids like biodiesel. E.g.
green algae, diatoms and
blue-green algae are being
studied for their suitability for
mass-oil production. To give
an example, the green algae
species Botryococcus braunii convert almost 70% of its
biomass in oil. This is good
Algae manipulation
To take care that all these
algae produce more than
enough oil, algae can
being manipulated. When
algae cells are environmentally stressed, the dry
weight lipid contents can
double or triple. So e.g.
nitrogen or silicon (Diatoms are characterized
by the presence of silicon
in the cell wall) can be
rapped.
Another option is to increase the expression of
enzymes that are involved
in the pathways of fatty
acid synthesis. E.g. acetylCoA carboxylase can be
increased so more acetylcoenzyme A synthesis into
malonyl-CoA.
for 136 900 liters of oil/ha/
year what means they are
about 20 times more productive per unit area than oil
palm, the most productive
bio-fuel so far with 5950
liters oil/ha/year.
The most natural method of
growing algae for biodiesel
production is through openpond growing. Open ponds
have a variety of shapes
and sizes but the most
commonly used design is
the raceway pond. In these
ponds, the algae, water and
nutrients circulate around a
racetrack. With
paddlewheels, algae are kept
suspended in the water, and
are circulated back to the
surface.
Figure 3 from biomass to methane
6
The ponds are always kept
shallow so the algae can
absorb all the sunlight they
need. CO2 and nutrients are
being constantly fed to the
ponds,
while
algaecontaining water is removed
at the other end.
One of the major advantages of open ponds is that
they are easy to construct
and operate, but it has got
also many drawbacks like
poor light utilization by the
cells, evaporative losses,
diffusion of CO2 to the
atmosphere, requirement of
large areas of land and a
low biomass production.
Also bad weather can stunt
algae growth, as can contamination from bacteria or
other organisms. The water
in which the algae grow also
has to be kept at 20-30°C,
which can be difficult to
maintain.
Other companies are constructing closed-tank bioreactors to help increase oil
rates even further. Instead
of growing algae outside,
indoor plants are built with
large, round drums that
grow algae under ideal
conditions. The algae are
manipulated into growing at
maximum levels and can be
Figure 5: Open pond
Figure 4: High density vertical growth system by Valcent
harvested
every
day.
(Newman S. 2010) Solar
collectors, solar concentrators, or fibre optics allow
the sunlight to reach algal
cells in the thin, horizontal
tubes or by directing light,
through a fibre optic matrix.
(Campbell N.M. 2008)
Closed bioreactor plants can
also be strategically placed
near energy plants to
capture
excess
carbon
dioxide that would otherwise
pollute the air.
(Newman S. 2010)
The high density vertical
growth system, also known
as the Vertigro system or
closed loop production is
another way to produce biodiesel. This is made by the
company: Valcent. In this
system, instead of pipes,
algae, water (only 5% of the
water that is normally required have to be used) and
nutrients are placed in
transparent bags made of
polyethylene, so they can be
exposed to sunlight on two
sides. These packages are
a lot cheaper than the glass
tubing and the fiber optic
light distributors from the
bioreactors.
And
when
locating this system next to
carbon producing power
plants, the algae can use
those emissions to grow.
Other advantages are that
the bags are protected from
the rain because they are
grown
in
greenhouses.
These greenhouses are
settled in the desert (namely
in El Paso, Texas) so the
extra sun increases the
productivity rate of the
algae, which in turn increases the oil production.
(Newman S. 2010;Sweeney
2007;Walton 2010)
Another method to produce
algae oil is the heterotrophic
fermentation. Solazyme in
South
San
Francisco
cultivate their algae in
stainless steel tanks (each
fermentation vat contains a
single species) en feed them
7
a consistent supply of sugar
until they are large, round
and ready to explode with
oil.
This method has got the
advantage that the algae
don’t need CO2, water and
light.(Green car congress
2009;Kagan 2010;Wu 2010)
Other benefits of this process are that it allows the
algae biodiesel to be produced anywhere in the
world. Therefore fermentation offers the most control
of all the methods. Temperature, pressure, and other
environmental
conditions
can be minutely controlled.
(Michael K. 2008) The big
disadvantages are that it
cost more, only a few algae
species can be used
because not all of them can
grow in darkness (an
example is Chlamy domonas) and researchers are
still trying to figure out where
to get enough sugar without
creating problems.
(Newman S. 2010;
Wageningen UR 2010a)
When the algae has produced enough oil, the oil can
be extracted. There are
three ways to do this. The
first and the most used one
is the hexane solvent
method. This is a two-part
Figuur 6: Algae plantation in the desert
process. First, the press
squeezes out the oil. Then,
the leftover algae is mixed
with hexane, filtered and
cleaned through distillation
so there is no chemical left
in the oil.(Newman S. 2010)
Another method is the
supercritical fluids method.
Here CO2 is liquefied under
pressure and heated to the
point that it has the
properties of both a liquid
and a gas. This liquefied
fluid then acts as a solvent
to extract the oil. The
additional equipment and
work make this method a
less
popular
option.
(Newman S. 2010;Oilgae
2010b)
The process of Transesterification
Transesterification is a chemical reaction for conversion of
vegetable oil to biodiesel. The oil reacts with an alcohol in the
presence of a catalyst like sodium hydroxide.(Hess Scott M.
2010) The end products are hence biodiesel, sodium
(m)ethanolate and glycerol. To separate this end-mixture, ether
and salt water are added. After some time, the entire mixture has
been separated into two layers, with in the bottom layer a mixture
of ether and biodiesel. This layer can again be separated.(Oilgae
2010d)
A third method is the
ultrasonic-assisted extraction. In this process ultrasonic waves are being sent
around the algae sending
shock signals on to the
organisms. As a reaction to
the wave they release oil
substances into a solvent
that can be easily extracted.
(Algae-oil 2010)
Once the oil is finally extracted, they can be transformed
into biodiesel, in a process
called trans-esterification, to
use in transports. The byproducts like sugars and
proteins could be recycled
for animal feeds or even as
replacements
for
other
petroleum
products like
ethanol. (Alok J 2008)
Bio-hydrogen
Hydrogen is one of the most
promising fuels for the future. The main advantage of
hydrogen fuel is that there is
no emission of greenhouse
gases. The combustion of
hydrogen gas produces only
water vapor, unlike fossil
fuels, there will be no
release of carbon dioxide.
Another advantage is that
hydrogen is almost inexhaustible. New hydrogen
can be made from water.
The viability and future of H2
depends entirely upon the
development of efficient,
8
large-scale and sustainable
H2
production
systems.
Currently, hydrogen is produced using non renewable
technologies such as steam
reformation of natural gas,
coal
gasification
and
petroleum
refining.
(Wikipedia 2010c)
The key enzyme in biological H2 metabolism is
hydrogenase. This unique
enzyme catalyses the formation and decomposition
of the simplest molecule
occurring in biology: H2.
A good example is C.
reinhardtii. Chlamydomonas
reinhardtii is a single celled
green alga about 10 micrometers in diameter that
swims with two flagella. It
provides the basis for solar
driven bio-hydrogen production.
The first difficulty is decoupling hydrogenase from
photosynthesis. Hydrogenases are usually extremely
sensitive to inactivation by
oxygen. If this could be
achieved, there is no need
for an anaerobic environment
for
large-scale
hydrogen
production.
In 2000, it was discovered
that when lacks sulfur, they
automatically switch from
normal photosynthesis to
hydrogen
production.
(Miyake et al. 2004;Solar
biofuels
2008)
Hydrogenase
In anaerobic conditions,
mitochondrial oxidative phosphorrylation
is
largely
inhibited. Under these conditions, some organisms
reroute the energy stored in
carbohydrates to a chloroplast hydrogenase. H2ase
essentially acts as a H+/erelease valve by recombining H+ and e- to
produce H2 gas that is
excreted from the cell.
H2 Production
H2O → 2H+ + 2e- + 1⁄2 O2
2H+ + 2e → H2
H2 Combustion
H2 + 1⁄2 O2 → H2O. + E
Secondly, scientists are
trying to interrupt the photosynthesis process, through
genetic manipulation, so
oxygen cannot reach the
level to inhibit the hydrogenase.
Nevertheless, the main idea
for bio-hydrogen production
is not the construction of
huge algae plantations. A lot
of scientist are trying to
create a “backyard plantation”. This model would
allow people to produce
their own hydrogen.
A group of Philadelphiabased
(USA)
creatives
known as the 20/2 Collaborative have designed a
unique concept that is based
on small-scale production of
hydrogen. This plan mixes
algae ponds with floating
balloons to integrate fuel
production and distribution
into the local landscape and
allows the renewable fuel to
be created and distributed
from the same place.
(ecocool 2007)
Disadvantages and
possible solutions
As expected there are also
disadvantages about biofuels produced by algae.
The first and obvious reason
is that it is very expensive,
because it’s a very new
technology. There has to be
a lot of money for research
and trying out different
methods. Another reason
that makes the harvest of
algal biomasses relatively
costly is the low biomass
concentration in the microalgal culture due to the limit
of light penetration in
combination with the small
size of algal cells. Also
because it is very new it’s
required to develop standardized protocols for cultivation
and
bio-fuel
production.
Yusuf Christi, an NewZeeland researcher, pointed
out that to compete with
other energy sources the
cost of growing microalgae
for bio-fuel production must
be drastically reduced. A
solution could be a high
volume co-product strategy,
this contains the extracting
Figure 7: H2 respiration
9
of bioreactive products from
harvested algal biomass.
Examples are carotenoïden,
vitamins,
polyunsaturated
fatty acids, … These can be
used
in
pharmaceutical
compounds, health food and
natural pigments. A solution
for the limit of light
penetration has been found
by Anastasios Melis, a plantand microbial-biology professor at the University of
California. She produced a
mutant algae that makes a
better use of sunlight than
the normal algae. This is
important for the maximization of the production.
The
algae
have
less
chlorophyll
than
others
wherefore they absorb less
sunlight so more sunlight
can reach other algae. This
process is still in progress
and so the new formed
algae are not yet being
used.
Another drawback is that the
bio-fuel produced by algae
is very unstable, not only
does it contain unstable
chemical products also it
has many polyunsaturated
fatty acids which is not that
profitable. The produced
bio-fuel
has
a
lower
performance also than the
bio-fuels produced by for
example rapeseed or soybean. Also there will have to
be economically viable harvesting technologies found
for large scale algae production. Because now the
focus lays with the improvement of the algae itself
and creating innovative harvesting technologies and not
so much with the economic
side. This can be solved
with genetic engineering,
and several techniques are
currently being tested.
(Kyndt 2010;Li Y. et al.
2008;Ningthoujam S.
2010;Prachi P. 2007;Rob
2010)
Figure 8: H2 respiration
Companies
Synthetic
Genomics,
ExxonMobil Research and
Engineering Company are
three of the many companies that try to find
solutions for the global
challenges including energy
and environment. They have
an development agreement
of a multi-year research to
develop next generation biofuels using photosynthetic
algae.
Even though the algae naturally don’t carry out the process as efficient as should
be for an commercial-scale
production
of
bio-fuels.
These companies believe
that biology can be harnessed to produce sufficient
quantities of bio-fuels, with
the use of scientific expertise and proprietary tools
and technologies in ge-
nomics en genome engineeering as a platform. So
their goal is to find, optimize
and/or engineer superior
strains of algae and also try
to define and develop the
best systems for large-scale
cultivation
of
algae.
(Jacobs and Ventor 2009)
Toyota and sapphire energy
are also involved in this
research. Sustainable mobility and environmental
leadership are core principles of Toyota’s business
strategy for future growth.
One of their new technologies has brought them a
step forward in improving
the environmental impact of
automobiles. It involves an
to plug-in Prius hybrid that
has been converted to “The
Algaeus”. This car drove on
a mixture of battery power
Figure 9: Process sapphire energy
10
and algae fuel blended with
conventional gasoline. Unfortunately they couldn’t fully
get rid of the smell of a
neglected swimming pool
when they were driving the
car. This drive was due to
the research and development of the company
Sapphire
Energy.
This
company has their algae
producing 30 percent by
weight of oil so they confirm
that it is possible to use
algae-oil for an efficient
system.
The algae are cultivated in
open ponds with salt water
in deserts (performs best
there). They use nonpotable, non-fresh water en
non-arable land therefore it
does not contribute to
deforestation.
A lot of scientists and
important people in this
sector believe that bio-fuel
from microalgae has the
potential to replace the
petroleum transport fuels
without affecting the food
supply.
This believe hasn’t fully
been
transformed
into
practice but it’s not that far
away. A lot of companies
are doing research and
developing methods so that
they can succeed in bringing
a new bio-fuel on the
market.
(Biello D. 2009;Lahaussois
2010;Sapphire
Energy
2010)
Figure 10: The algaeus
Figure List
Figure 1: Cartoon biofuels first generation ....................................................................................................... 2
Figure 2: Microscopic photo of microalgae ....................................................................................................... 2
Figure 3 from biomass to methane .................................................................................................................... 2
Figure 5: High density vertical growth system by Valcent .............................................................................. 2
Figure 4: Open pond ............................................................................................................................................ 2
Figuur 6: Algae plantation in the desert ............................................................................................................ 2
Figure 7: H2 respiration ........................................................................................................................................ 2
Figure 8: H2 respiration ........................................................................................................................................ 2
Figure 9: Process sapphire energy .................................................................................................................... 2
Figure 10: The algaeus ........................................................................................................................................ 2
11
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