microalgae to biodiesel
TRANSCRIPT
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Prof. Roberto Rana
University of Foggia
Faculty of Economics
University of Foggia - Faculty ofEconomicsErasmus Intensive Programme EPROBIO
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Why to use algae to produce biofuels?
Over this last decades the frequent oil crises
and environmental impact of fossil fuels, hasdived many industrialized countries tocarrying out research to discover analternative sources of fuels able to ensure a
new energy sources supply that reduceemissions of CO2, nitrogen monoxides andsulphur into the atmosphere.
So, has been introduced biofuels mainlyderived from sugar cane, corn, as bio-
ethanol or biodiesel, obtained fromrapeseed, soybean, etc. However someresearchers believe that bio-energy will notbe able to satisfy future world fuels
requirements, since intense energy crop
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Why to use algae to produce biofuels? Algae are the fastest growing
microorganisms (some unicellular algaedouble their weight in 12-24 hours, whilecells are able to separate in less than 4hours),
Algae are most abundant biomassproducers in earths biosphere. Some algaehave a high yield (biomass production) (50-70 t/hectares per year).
Most algae are unicellular and thereforecontain a very high amount of starches orlipids (up to 50% dw).
Compared to plants, algae require less
space to grow, have more tolerant
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RHODOPHYTA
Chondrus crispus
Gelidium spp
PHAEOPHYTA
Fucus spp
Laminaria spp
Ascophyllum nodosum
CLOROPHYTAUlva lactuca
MACROALGAE
Classification of Algae
Worldwide are described 30 000 species of microalgae (< 10% of estimated).The classes (29) are distinguished by the structure of flagellate cells (e.g.,
scales, angle of flagellar insertion, microtubular roots, and striated roots), thenuclear division process (mitosis), the cytoplasmic division process
(cytokinesis), and the cell covering.
Spirulina spp flos-aquae
Diatomee
(Bacillariophyta)
MICROALGAE
Cianoficae Clorophycophyta
Green algae
Chrysophycophyta
(golden algae)
Dinophyta
(dinpflagellates)
Neochlorisoleoabundans,
Scenedesmus
dimorphus,
Botryococcus brunii
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Macroalgae or seaweeds
The worlds mostsuccessful seaweedcultivation industriesare in Asia. Howeverthis continent is reallow in technology
Japan is one ofthe big producer
and consumer ofseaweeds in the
world.
Cultivating seaweed in
Portugal, England andIreland is traditional.People use fertilizer for
their seaweed.
China is thebiggest producer
and consumer ofseaweed
The shallow coral
lagoons off the
coast of EastAfrica andZanzibar are
host to multipleseaweed farms.
Seaweeds cultivation are old. Seaweed has
been part of the Chinese diet for over 2000years and probably much longer. The macro-algae have a high biomass yield from 7-30t/hectares.
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Macroalgae growing systems
There are many
technologies tocultivate seaweed.For instancetraditionalseaweed farminguses lines, ropes,nets or rafts,floating suspendedin the sea.
Young seaweed orpart of seaweed
are attacked to thesubstrate and thanare left to grow for6 to 8 weeks,depending on the
species andlocation.
Generally seaweeds species grow
very fast and can be croppedwithin a few months.
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A new cultivationsystems of seaweed
Because most ofmacro algae live onthe sea bed isdifficult to cultivate
in offshoreinstallations andhave highproduction. These
technology, indeed,are subjected to theaction of waves andtides. To resolve
these problemsA concave mirror placed in the sea
surface converges the radiation at depths
where macroalgae grow
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Paths of the various energy products fromseaweedSyngas is the name given to a
gas mixture that contains
varying amounts of carbon
monoxide and hydrogen. Thegas is obtained by a process
that occurs at high
temperature and in absence of
oxygen
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MICROALGAE
The microalgae areunicellular
organisms, in generalphotosynthetic, with
a few microns size(
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MICROALGAEMicroalgae generally have a protein,
carbohydrates and fats content vary widelydepending on the species. For instance
the average amount of lipid ranges from 1-
40% dry weight. Fats composition and
quantity depend on the environmental
factors of the algae broth (temperature,
salinity, light intensity, etc.). So, when algal
cells grow in situations of nutrientdeficiency (such as nitrogen, silicon, etc.)
or in a broth rich in sodium chloride, can
increase fats content more than 70%.
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Microalgae
Biodiesel
Hydrogen
Bio-ethanol Biogas
Foodsuppleme
nts
Food
industry
Feed
industry
FinalChemicals
Commercial use of microalgae
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BIODIESEL FROM MICROALGAE
Microalgae, have the highest biomassproduction (50-70 t/ha) and oil content
(about 20-30 m3/ha) among all plants,
significantly higher than those of corn,soybeans, palm oil, etc..
According to some authors, the annual
yields are much higher, up to values
280t/ha.
Comparison between yield of most common
oleaginous crops and microalgae
Land surface
occupied by soy
productionnecessary to supply
USA diesel
consumptionLand surface
occupied by corn
production
necessary to supply
USA dieselconsumption
Land surface
occupied by algae
schemes necessary
to supply USAdiesel consumption
~ 250 billion liters of diesel is the nation presently consumes
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BIODIESEL FROM MICROALGAE
Although the idea of growing algae to obtain biofuels started to
the end of the 1940s, the first applied studies were
undertaken only twenty years later, when some American
researchers proposed to use these organisms to obtain biogas
by fermentation, to be burned in electric power plants.
During the first energy crisis (1973) the American Congress
set up the NREL (National Renewable Energy Laboratory),linked to the DOE (Department Of Energy). This laboratory
carried out a programme, call Aquatic Species Program
(ASP), to grow unicellular microalgae in a ponds connected to
electric power plants.
but thisprogramme wasstoped in 1996
because
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BIODIESEL FROM MICROALGAE
Initially DOE researchers was aimed at the possibility to
obtain biogas from the fermentation of microalgae and to
store CO2. The success of this experiment and the
discovery of large quantities of oil contained in
microalgae led researchers to use these organisms to
produce biodiesel.
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1Open ponds
2Photobioreactors
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Open cultivation systems
Open pond or racewaypondA raceway pond is a shallow
artificial pond used in the
cultivation of algae. The pond,
with a surface from 100-1000-
10000 m2
and a dept from 15-30cm, is divided by several baffles
forming one channel in the
shape of an oval, like an
automotive raceway circuit. From
above, many ponds look like a
maze (labyrinth). Each basin
contains a paddlewheel to make
the water flow continuously
around the circuit and prevents
the deposition of microalgae on
the bottom of the pond.
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Open cultivation systems
Open pond or racewaypond
To cultivate microalgae requires an appropriate culture
medium (broth), consisting of an aqueous solution rich in
inorganic salts such as sodium chloride, potassium
carbonate, calcium chloride, potassium nitrate, calciumphosphate, etc.. and appropriate environmental conditions
(light, temperature, concentration of CO2, etc.).
Some installations are made by several pondswhere you can use a thermal power plantemissions (CO2, and oxides of nitrogen) and/or
sewage(wastewater with high concentration ofnitro en and hos horus to feed al ae.
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Open cultivation systems
To prevent predation by other species, the salt
concentration of the broth is keep high
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In order to cultivate microalgae species thatprefer lower salt concentrations, achieving
a higher cell density and prevent the
contamination of culture medium, were
tested the photobioreactors.These facilities are closed systems in which
the algae are not direct contact with the
external environment and receive solar
radiation directly through the walls of
photobioreactor or from optical fibers or
solar collectors (concave mirrors).
Closed cultivation systems
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Closed cultivation systemsPlants may be placedPlants may be placed outdoorsoutdoors ororindoorsindoors (greenhouses).(greenhouses).
Plastic bagsPlastic bags
(outdoor or indoor)(outdoor or indoor)
PhotobioreactorsPhotobioreactors
are made in glass,are made in glass,
plastic or otherplastic or other
materialsmaterials
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Closed cultivation systems
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How the photobioreactor work:
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How tubular photobioreactor work:
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How flat panel photobioreactor work:
The flat panel photobioreactors are made in glass or Plexiglas and have
rectangular shape, vertically arranged, with a thickness about 1-5 cm. In thisvessels microalgae are harvested (recovered) at the top and kept in suspension
through an air flow introduced at the bottom generally by a special tube. This
system seems to offer high biomass yields, with the increased surface area
exposed to solar radiation that can improve the photosynthetic efficiency and
to increase biomass production (80g/L vs. 30-50/L).
O P d Ph t bi t
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Open Pond versus PhotobioreactorPARAMETER
SOPENPOND
NOTE PHOTO
BIOREACT
OR
NOTE
Land space fill High - Low -
Water loss Very high - Low -CO2 loss High Depends on the
depthness of the pondLow -
CO2 consume Medium - Medium -Concentration
of O2
Low O2 is released freely
from the surface oftanks
High O2 must be removed
due to inhibition ofphotosynt. problems
photo-oxidationTemperature Very variable Depends on the depth
of the pondsHigh Often requires a cooling
system accessories
Mixing algae Low It is carried out using a
paddlewheel
High Its occurs by pumping
in gas such as CO2Cleaning
equipmentNot required - Required It is required to clean
the walls of photob.because algae growthreduces the incoming
solar radiationContamination Very high Depends on the
chem./phys. charac. ofthe broth
Very low -
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Raceway Pond versus Photobioreactor
The comparison between raceway ponds and bioreactors
shows that the management of the former is difficult becausethe operational parameters such as temperature, salinity,
dissolved gases, etc., depend on environmental conditions. In
addition, productivity may be lower due to the phenomena of
contamination of parasites and competition with other aquaticplant species.
So, photobioreactors seem to be the most promising
technology, although currently the increased cost of production
of biomass and the complexity of managing prevent its
widespread use.
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A new technology process
HR BioPetroluem proposed a hybrid system thatprovides for the combined use of both technologies.
This new process use only photobioreactors to make apure culture of microorganisms, with high productivityand rate of nutrient intake. When the algae biomass
achieve high concentration than it is inoculated in openponds. To prevent contamination phenomena, algaebiomass are left in the tank for a day allowingsterilization during the follow night.
With the development of this hybrid productionsystem, HR BioPetroleum has achieved significant
Currently simple and inexpensive new facilities have been
proposed combining the two technologies allowing bothlower operating costs and increase biomass yields.
This system combines low costand the high productivity ofalgae ponds with the protectionof culture-closedphotobioreactors; allowscontamination-free
monocultures of the mostproductive algae to becultivated; minimizes capitalinvestment as a cost factor.
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Oil extraction
Flocculation
This phase can occur
spontaneously in a tank, but
can be speeded up by
raising the value of pH,
adding salts, lowering the
concentration of certain
nutrients or gases or byadding appropriate
flocculants.
Decantation/
Filtration
Centrifugation
Centrifugation is used to removemost of the water still present in
algal biomass. This is the most
expensive stage because of the
energy consumption (1000$/t)
and purchase cost.
Water
Open pond orOpen pond or
bioreactorsbioreactorsThe water removed, still rich in nutrients,
is sent again in the pond or bioreactors.
Filtration is carried out commonly onmembranes of modified cellulose. The
greatest advantage of this method as a
concentrating device is that it is able to
collect microalgae or cells of very low
density. However, concentration by
filtration is limited to small volumes andleads to the eventual clogging of the
filter by the packed cells when vacuum
is applied. This technology is used
when is not required an excessive
removal of water.
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Flocculation Decantation/
Filtration
Centrifugation
Water
Open pond orOpen pond or
bioreactorsbioreactorsThe water removed, yet rich in nutrients,
is sent in the pond or bioreactors.
Algaepaste
Extract
ion
OIL Cake
Animal feedAnimal feed
BiogasBiogasFinal ChemicalsFinal Chemicals
HeatHeatBIODIE
SEL
Trans-esterificationTrans-esterification
Oil extraction that mayoccur by simple coldpressing, with recovery70-75% of oil, or asuitable solvent(benzene, petroleumether, cyclohexane,etc.). immiscible inwater, with yields up to100%.
1g/L1g/L
50-100 g/L50-100 g/L
The cake nottreated usingcyclohexane, still
rich in preciouspolyunsaturated fatacids -3 and -6 , can be utilized asfeed because it is
rich also incarboh drates and
Oil extraction
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Though oil from microalgaemay be used as it is in dieselengine, in order to improve its
performance, it undergoes aprocess of trans-esterificationhaving it react with alcohol
(methanol).
OIL FROMMICROALGAE
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Biodiesel from microalgaeversusversus biodiesel standard
In general, biodiesel from microalgae has similarphysical-chemical characteristics and, in somecases, better than standard one, for example, afewer number of a Cold Filter Plugging Point and a
higher value of heating value.
Biodiesel from soyBiodiesel frommicroalgae
Cold filter plugging point (C)
Density(kg /L)
Viscosity
Acidity
Heating value
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Some economics aspectsUnit of
measurementsOpen Pond Pannell
Photobioreactor
Tuborar
Photobioreactor
Biomass production
T/y per hectare 20 60 40
Photosyntheticefficiency
% 1,5 5 3
Penetration of solarradiation in the
system
cm 20 3 3,4
Capital Costs /hect. 70 000 > 700 000 > 700 000
Energy consumption kWh/ha ~ 1.800 5.000-185.000 5.000-185.000
Production costs of
biomass
/kg (dw) 5.70 4.03 4.02
Major cost factor % Movement of paddle (15)
Input of air (24) Pumping (46)
The development of commercial-scale biodiesel from microalgae seems not yet economically feasible for both the low biomass
production and high cost. As you can see in table, photobioreactors have capital and operating costs much higher than open
pond because of more complex technology involved in this technology. However, higher yields in biomass would seem to offer
better development prospects to photobioreactors than open ponds.
At the present the cost of 1L of
biodiesel product withphotobioreactor is
< 3$/L (palm oil 0,6 $/L)< 3$/L (palm oil 0,6 $/L)
How can we reducethe price of biodiesel
from microalgae?
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Some economics aspects
Because 300 t/ha per year (dw) is considered the production of
microalgae biomass which would produce a real economic
benefit to the factory owner we are far from producing an
economic return in the production of biodiesel from algae
Actual yield in a best plant:15/m2 per day 50 t/hect. per year (dw)
oil ~ 20 t/ per year
Best yields a short-run:
30/m2 per day 100 t/hect. per year (dw)oil ~ 40 t/ per year
Best yields a long run:
50g/m2 per day 170 t/hect. per year (dw)
oil ~ 70 t/ per year
to produceGenetically Modified
Microalgae
to improve algae biomass productionto improve algae biomass production
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Open pond - algae cultivation
10%
90%
55%
45%
45%
90%
10%
75-78% lost
lost
lost
15% lost (mt= 1000t)
lost
/m2
S i t (GMO
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Some economics aspects (GMOmicroalgae)
light radiation is
not absorbed andrelease as heat
This phenomenon known as the light saturation effect is
particularly unfavorable to microalgae production systems.
In fact microrganisms live in the deep grow slightly because
of the sunlight intercepted by the algae placed on the
Because of the size of the chlorophyll pigment, 90% of
solar radiation absorb by the algal cell is lost as heat
In nature there is an mutant strain of alga (Chlamydomonas
reinhardtii) that has a short dimension of photosynthetic
pigments. This modification reduce the amount of light
absorbed by the algae leaving the radiation get in the deep.
Researchers now want to transfer this mutant
character to other species of microalgae
Wild types Mutant types
Wild types Mutant types
S i
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Some economics aspects
Because 300 t/ha per year (dw) is considered the production of
microalgae biomass which would produce a real economic
benefit to the factory owner we are far from producing an
economic return in the production of biodiesel from algae
Actual yield in a best plant:15/m2 per day 50 t/hect. per year (dw)
oil ~ 20 t/ per year
Best yields a short-run:
30/m2 per day 100 t/hect. per year (dw)oil ~ 40 t/ per year
Best yields a long run:
50g/m2 per day 170 t/hect. per year (dw)
oil ~ 70 t/ per year
to improve algae biomass productionto improve algae biomass production
How can we reducethe price of biodiesel
from microalgae?
to use by-productscame from oil
production(i.e. astaxantina)
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It should be noted, however, that the simplecomparison between the input and output energyshow that open ponds involve a higher "energyreturn than the photobioreactors.
*Include the energy consumption in the plant and the energy consumption to
produce the devices.
** Includes the energy obtainable from the production of algal biomass
I wonder how photobioreactorscan be considered the cheapest
technology if they consume 100times more energy than openponds?Energy is considered an important cost: it represent40% of the total costs
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The production of biodiesel from
microalgae is a valid alternative to the
traditional energy crops, because the use
of these microorganisms do not subtracts
valuable resources for food.
Future developments
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However, the low biomass yields and high
production costs prevent a large-scale
commercial development. In deed, as we
see above, 1 liter of oil from microalgae
costs about six times the palm oil.
Future developments
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So, some researchers believe that commercialdevelopment of biodiesel production from
microalgae requires many years before being
feasible. They think, in deed, that has not yetshown that intensive algal culture provide
more energy than that it consumes.
Future developments
This figure shows the energy invested over the
lifecycle versus the energy in the algae biomass
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Challenges for the future are:
1) genetic improvement of microalgae species (to
create an organism with a higher yield in biomass
and oil);2) to resolve technical issues (fouling,
contamination of the broth, control of operating
parameters, etc.);
3) economic valorization of by-products (final
chemical, biogas, animal feed, etc.)
Future developments
The achieve of these
targets will reduce capitaland management costs
and will allow the large-scale production ofbiodiesel from
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