WO2011070432A1 - Procédé pour la production d'huile biologique à partir d'algues phototrophes et hétérotrophes - Google Patents

Procédé pour la production d'huile biologique à partir d'algues phototrophes et hétérotrophes Download PDF

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Publication number
WO2011070432A1
WO2011070432A1 PCT/IB2010/003179 IB2010003179W WO2011070432A1 WO 2011070432 A1 WO2011070432 A1 WO 2011070432A1 IB 2010003179 W IB2010003179 W IB 2010003179W WO 2011070432 A1 WO2011070432 A1 WO 2011070432A1
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Prior art keywords
phototrophic
algal biomass
heterotrophic
aqueous suspension
oil
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PCT/IB2010/003179
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English (en)
Inventor
Ezio Nicola D'addario
Francesca De Ferra
Federico Capuano
Roberta Miglio
Aldo Bosetti
Lino Carnelli
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Eni S.P.A.
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Priority to MA35033A priority Critical patent/MA33900B1/fr
Publication of WO2011070432A1 publication Critical patent/WO2011070432A1/fr
Priority to TNP2012000275A priority patent/TN2012000275A1/en

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    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12P—FERMENTATION OR ENZYME-USING PROCESSES TO SYNTHESISE A DESIRED CHEMICAL COMPOUND OR COMPOSITION OR TO SEPARATE OPTICAL ISOMERS FROM A RACEMIC MIXTURE
    • C12P7/00—Preparation of oxygen-containing organic compounds
    • C12P7/64—Fats; Fatty oils; Ester-type waxes; Higher fatty acids, i.e. having at least seven carbon atoms in an unbroken chain bound to a carboxyl group; Oxidised oils or fats
    • C12P7/6436—Fatty acid esters
    • C12P7/649—Biodiesel, i.e. fatty acid alkyl esters
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E50/00—Technologies for the production of fuel of non-fossil origin
    • Y02E50/10—Biofuels, e.g. bio-diesel

Definitions

  • the present invention relates to a process for the production of bio-oil from phototrophic and heterotrophic algae .
  • the present invention relates to a process for the production of bio-oil from phototrophic and heterotrophic algae which comprises integrating the cultivation of algae, in particular of microalgae, autotrophic and heterotrophic, subjecting the aqueous suspension of algal biomass obtained from the cultivation of phototrophic algae to concentration before joining said aqueous suspension of algal biomass to the aqueous suspension of algal biomass obtained from the cultivation of heterotrophic algae and subjecting the aqueous suspension deriving from said combination to concentration and subsequent thermal treatment .
  • bio-oil thus obtained can be advantageously used in the production of biofuels which can be used as such, or in a mixture with other fuels, for motor vehicles.
  • said bio-oil can be used as such (biocombustible) , or in a mixture with fossil combustibles (combustible oil, lignite, etc.) for the generation of electric energy or heat.
  • Algae in particular phototrophic microalgae, are generally cultivated for the production of valuable compounds such as, for example, poly-unsaturated fatty acids (for example, eicosapentaenoic acid (EPA) , docosahexaenoic acid (DHA) , and the like) , vitamins
  • microalgae for the above sectors is characterized by the relatively limited productive capacities (in the order of hundreds-thousands of tons per year) and the high added value of the compounds obtained (hundreds-thousands of euro per kilogram) .
  • complex and expensive production systems particularly with respect to concentration and drying of the biomass and to the extraction of compounds of interest, which must satisfy strict regulations of a sanitary and nutritional nature, typical of the above- mentioned fields, can be tolerated.
  • Cultivations of algae generally use fresh or salt water to which nutrients and mineral salts and, when necessary, vitamins and/or other products (for example, antibiotics) , have been added, and are carried out in bioreactors and/or in fermenters and/or in open ponds.
  • nutrients and mineral salts and, when necessary, vitamins and/or other products for example, antibiotics
  • the bioreactors and/or open ponds each of said bioreactors and each of said open ponds generally having surfaces ranging from 1 m 2 to 5,000 m 2 and depths ranging from 0.05 m to 2 m, maintained under solar irradiation, can generally be fed not only with water but also with carbon dioxide (C0 2 ) , in liquid or gaseous form, stocked in specific tanks, or obtained from exhausted gases deriving from industrial processings such as, for example, from natural gas electric plants, or from decarbonation plants of natural gas or other fuel gases (for example hydrogen) , optionally diluted with air.
  • C0 2 carbon dioxide
  • said carbon dioxide (C0 2 ) in gaseous phase is generally bubbled through the liquid algal biomass by means of distribution systems and perforated ducts immersed in said bioreactors and/or in said open ponds.
  • the growth is generally carried out in one or more bioreactors and/or in one or more fermenters, each of said bioreactors and each of said fermenters generally having a volume ranging from 0.010 m 3 to 1,000 m 3 , in the presence not only of water but also of a dissolved organic carbon source such as, for example, sugars (e.g., glucose), carboxylic acids (e.g., acetic acid), carbohydrates, proteins, in the absence or presence of light, and in the presence of air or of air enriched in oxygen, optionally humidified.
  • sugars e.g., glucose
  • carboxylic acids e.g., acetic acid
  • carbohydrates e.g., proteins
  • air or of air enriched in oxygen optionally humidified.
  • Miao X. et al . describe the production of biodiesel from algae in the following article: "Biodiesel production from heterotrophic microalgal oil” , published in “Bioresource Technology” (2006), 97, pages 841-846.
  • algae of the species Chorella protothecoides grown under heterotrophic conditions, are collected by centrifugation, washed with distilled water, and subsequently dried in a freeze drier.
  • the freeze-dried algae are subsequently pulverized in a mortar and subjected to extraction with hexane in order to extract the oil.
  • the extracted oil is subsequently subjected to acid transesterification in the presence of methanol and sulfuric acid as transesterification catalyst, in order to obtain biodiesel.
  • bio-oil from algae is potentially . advantageous with respect to the production of bio-oil from agricultural crops as it allows a higher production of oil per hectare of surface per year. Furthermore, the bio-oil produced from algae does not compete with said agricultural crops which are generally crops for nutritional use (for example, corn, soya, sugar cane, rape) . The cultivation of said algae however, can have various drawbacks.
  • the low concentration of the algal biomass per litre of aqueous suspension requires the use of large volumes of water and of relatively large surfaces and consequently high costs and energy consumptions for the separation and concentration of the algal biomass, i.e. relatively low yields of bio-oil with respect to the volumes of water treated.
  • Heterotrophic microalgae do not require light for their growth and consequently their concentration in the aqueous medium does not suffer from the limit of light penetration in the growth medium.
  • Heterotrophic microalgae require an energy and carbon source alternative to light and to carbon dioxide (C0 2 ) .
  • Said alternative energy and carbon source generally comprises organic compounds such as, for example, sugars (e.g., glucose), carboxylic acids (e.g., acetic acid) , carbohydrates, proteins, which are not always easily available at competitive costs.
  • an organic carbon source such as, for example, glucose, acetate, or ethanol
  • the Applicant has found that the processes described above can only be carried out in the presence of algae capable of growing under both photoautotrophic and heterotrophic conditions during their life cycle.
  • the Applicant has found that, when the aqueous phase deriving from the cultivation of heterotrophic algae, under heterotrophic conditions, generally rich in dissolved and dispersed organic compounds and having a high C.O.D. ("chemical oxygen demand"), comes into contact (for example, by recycling said water) with phototrophic algae cultivated under photoautotrophic conditions, problems may arise in the growth of said phototrophic algae (e.g., a slowdown in their growth) .
  • C.O.D. chemical oxygen demand
  • the Applicant has now found that the production of bio-oil from phototrophic and heterotrophic algae can be advantageously carried out by means of a process which comprises integrating the cultivation of algae, in particular microalgae, phototrophic and heterotrophic, subjecting the aqueous suspension of algal biomass obtained from the cultivation of phototrophic algae to concentration before joining said aqueous suspension of algal biomass to the aqueous suspension of algal biomass obtained from the cultivation of heterotrophic algae and subjecting the aqueous suspension deriving from said combination to concentration and to subsequent thermal treatment.
  • Said process allows a good yield of bio-oil to be obtained, overcoming the disadvantages described above.
  • said process allows to avoid the contact between the aqueous phase deriving from the cultivation of heterotrophic algae, under heterotrophic conditions, and the phototrophic algae cultivated under photoautotrophic conditions, and consequently allows to use algae capable of growing under photoautotrophic conditions only, during their life cycle and algae capable of growing under heterotrophic conditions only, during their life .cycle, without having growth problems of said phototrophic algae.
  • the aqueous phase deriving from the concentration of the algal biomass obtained from the concentration of algal biomass comprising both phototrophic algae and heterotrophic algae, said aqueous phase being in a limited quantity, in order to maintain the levels of salts and of organic substances which may optionally accumulate during said process, within the management limits of the production plant used in said process .
  • a further important advantage lies in the fact that the aqueous phase which is obtained after thermal treatment of the aqueous suspension of algal biomass comprising both phototrophic and heterotrophic algae, said aqueous phase comprising organic compounds such as, for example, sugars (e.g., glucose), carboxylic acids (e.g., acetic acid), glucoside fractions, proteins, deriving from the thermal treatment (thermal hydrolysis) of the proteins and of the polysaccharides contained in the phototrophic and heterotrophic algae used, can be fed to the above process, in particular to the cultivation of heterotrophic algae.
  • the feeding of said aqueous phase to the cultivation of heterotrophic algae allows a reduction in the quantity of organic compounds, which, as indicated above, are usually used as alternative energy and carbon source in the growth of heterotrophic algae, under heterotrophic conditions.
  • Said aqueous phase can be used as water necessary for the cultivation of said heterotrophic algae thus avoiding the use of other waters (e.g., fresh or salt waters coming from natural or artificial sources) .
  • said thermal treatment allows a sterilization of said aqueous suspension of algal biomass comprising phototrophic and heterotrophic algae to be carried out, in this way minimizing the growth of other species (for example, bacteria) competitive with the growth of the algae, in particular with the growth of heterotrophic algae, under heterotrophic conditions.
  • other species for example, bacteria
  • An object of the present invention therefore relates to a process for the production of bio-oil from phototrophic and heterotrophic algae comprising:
  • an oily phase comprising bio-oil and an aqueous phase comprising organic compounds such as, for example, sugars (e.g., glucose), carboxylic acids (e.g., acetic acid), glucoside fractions, proteins .
  • sugars e.g., glucose
  • carboxylic acids e.g., acetic acid
  • glucoside fractions proteins .
  • the term “photoautotrophic conditions” means that the cultivation of the algae is carried out in the presence of carbon dioxide (C0 2 ) , solar or artificial light, and water, to which it is also possible to add: nutrients which can be selected from compounds comprising nitrogen such as, for example, urea, ammonia, ammonium salts, nitrates, or mixtures thereof; or compounds comprising phosphorous such as, for example, phosphates, or mixtures thereof; and/or microelements (or oligoelements) such as, for example, copper, iron, manganese, molybdenum, boron, selenium, cobalt, or mixtures thereof; and/or other compounds such as, for example, vitamins, antibiotics, or mixtures thereof; or mixtures thereof.
  • nutrients which can be selected from compounds comprising nitrogen such as, for example, urea, ammonia, ammonium salts, nitrates, or mixtures thereof; or compounds comprising phosphorous such as, for example, phosphates,
  • the term “heterotrophic conditions” means that the cultivation of the algae is carried out substantially in the absence of carbon dioxide (C0 2 ) [i.e. at a concentration of carbon dioxide (C0 2 ) lower than or equal to 3% by volume] and of solar or artificial light, and in the presence of air or of air enriched in oxygen, optionally humidified, and of organic compounds such as, for example, sugars (e.g., glucose), carboxylic acids (e.g., acetic acid), carbohydrates, proteins, as energy/nutrition source and water, to which it is also possible to add: nutrients which can be selected from compounds comprising nitrogen such as, for example, urea, ammonia, ammonium salts, nitrates, or mixtures thereof; or compounds comprising phosphorous such as, for example, phosphates, or mixtures thereof; and/or microelements (or oligoelements) .such as, for example, copper, iron, manganese, moly
  • said phototrophic alga can be cultivated in one or more open ponds and/or in one or more bxoreactors, each of said open ponds and each of said bxoreactors generally having surfaces ranging from 1 m 2 to 5,000 m 2 and depths ranging from 0.05 m to 2 m, maintained under solar irradiation.
  • said heterotrophic alga can be cultivated in bxoreactors and/or fermenters, preferably in closed bxoreactors and/or fermenters, each of said bxoreactors and each of said fermenters generally having a volume ranging from 0.010 m 3 to 1,000 m 3 .
  • the water necessary for the cultivation of said phototrophic alga and/or of said heterotrophic alga can be fresh water or salt water coming from natural sources such as, for example, seawater or river water, or from artificial sources such as, for example, coproduced waters or wastewaters coming from industrial and/or civil discharge water.
  • the algal cultivation metabolizes the substances containing nitrogen and/or phosphorous contained therein contributing to their purification.
  • the water necessary for the cultivation of said heterotrophic algae can be the aqueous phase obtained after the thermal treatment of said second concentrated aqueous suspension of algal biomass .
  • the water necessary for the cultivation of said phototrophic alga can be fresh water or salt water coming from natural sources such as, for example, seawater or river water, or from artificial sources such as, for example, coproduced waters or wastewaters coming from industrial and/or civil discharge waters; whereas the water necessary for the cultivation of said heterotrophic alga can be the aqueous phase deriving from the thermal treatment of said second concentrated aqueous suspension of algal biomass.
  • the fresh water can be river water or artificial water, for example, water coproduced in the synthesis of hydrocarbons such as the Fischer-Tropsch synthesis, or the synthesis known as "MTO process" ("methanol to olefin process”) .
  • MTO process methanol to olefin process
  • the salt water can be seawater or brackish-type water, natural or artificial, having a saline concentration ranging, for example, from 5 g/1 to 350 g/litre.
  • An example of brackish waters which can be used in the process object of the present invention, are waters coming from oil production fields.
  • the carbon dioxide contained in industrial combustion gases can be used as carbon dioxide (C0 2 ) necessary for algal growth, under photoautotrophic conditions .
  • algal cultivation i.e. growth
  • nutrients organic compounds, and/or microelements (or oligoelements) , and/or other compounds, when these are not already present in the water.
  • organic compounds such as, for example, solutions of various types of carbohydrates (e.g., glucose), carboxylic acids (e.g., acetic acid), glycine, are fed to favour growth under heterotrophic conditions; nutrients such as, for example, organic and/or inorganic salts soluble in water, such as, for example, ammonia salts, phosphates and/or nitrates, of alkaline or alkaline earth metals, for example phosphates and/or nitrates of sodium, potassium, calcium, magnesium, or ammonium phosphates, are fed to favour growth under both heterotrophic and photoautotrophic conditions.
  • carbohydrates e.g., glucose
  • carboxylic acids e.g., acetic acid
  • glycine e.glycine
  • nutrients such as, for example, organic and/or inorganic salts soluble in water, such as, for example, ammonia salts, phosphates and/or nitrates, of alkaline or alkaline
  • a stream of carbon dioxide (C0 2 ) is fed as carbon source to the water, in addition to the above nutrients and/or microelements (or oligoelements) , through specific distributors which can be deposited on the bottom of the open ponds, or of the bioreactors, or can be suitably inserted in the open ponds or in the bioreactors .
  • heterotrophic algae to the water, in addition to the above organic compounds, nutrients and/or microelements (or oligoelements) , it is fed a stream of air, or of air enriched in oxygen, optionally humidified, at a temperature ranging from 5°C to 45°C, preferably ranging from 20°C to 40°C, as oxygen source, through specific distributors which can be suitably inserted in the bioreactors or in the fermenters and, optionally, an aqueous stream comprising at least one inorganic base such as, for example, potassium hydroxide, sodium hydroxide, in order to maintain the pH of the cultivation water at optimum values for their growth (e.g., values ranging from 6 to 8).
  • said phototrophic alga can be selected from phototrophic microalgae (unicellular algae) .
  • Phototrophic microalgae which can be advantageously used for the purposes of the present invention can be selected from the following genera: Tetraselmis, Nannochloropsis, Nannochloris, Scenedesmus, Ankistrodesmus, Phaeodactylu , Chlorella, A phipleura, Amphora, Chaetoceros, Cyclotella, Cymbella, Fragilaria, Navicula, Nitzschia, Achnantes, Dunaliella,
  • Oscillatoria Porphiridium, Spirulina, or mixtures thereof .
  • said heterotrophic alga can be selected from heterotrophic microalgae (unicellular algae) .
  • Heterotrophic microalgae which can be advantageously used for the purposes of the present invention can be selected from the following genera: Chlorella, Nannochloropsis, Nitzschia,
  • Thraustochytrium Thraustochytrium, Spirulina, or mixtures thereof.
  • Said first aqueous suspension of algal biomass is discharged from said one or more open ponds or from said one or more bioreactors and subjected to concentration .
  • the concentration of said first aqueous suspension of algal biomass can be carried out through: gravitational separation by means of settlers and/or thickeners, typically used in waters treatment plants;
  • the concentration of said first aqueous suspension of algal biomass can preferably be carried out by gravitational separation by means of settlers and/or thickeners typically used in waters treatment plants.
  • said first aqueous suspension of algal biomass can be subjected to flocculation.
  • said first aqueous suspension of algal biomass can be subjected to flocculation.
  • Said flocculation can be carried out by means of various processes, such as, for example:
  • bio- flocculation for example, by cultivating algae in culture mediums having low nitrogen concentrations
  • said flocculation can be carried out by the addition of at least one flocculating agent.
  • Said flocculating agent can preferably be selected from: metal salts such as, for example, iron chloride, aluminium sulphate, iron sulphate, or mixtures thereof; cationic polyelectrolytes such as, for example, polyethyleneimines , polyacrylamides, or mixtures thereof; chitosane; or mixtures thereof.
  • said first concentrated aqueous suspension of algal biomass can have a concentration of dry algal biomass (i.e. of dry phototrophic alga) ranging from 0.1% by weight to 10% by weight, preferably ranging from 0.5% by weight to 5% by weight, with respect to the total weight of said first concentrated aqueous suspension of algal biomass .
  • a concentration of dry algal biomass i.e. of dry phototrophic alga
  • the aqueous phase which is obtained from the concentration of said first aqueous suspension of algal biomass can be used in the above process as water in the production of said first aqueous suspension of algal biomass (i.e. as cultivation water of said at least one phototrophic alga) .
  • said process comprises feeding the aqueous phase which is obtained from the concentration of said first aqueous suspension of algal biomass to the cultivation, under photoautotrophic conditions, of said at least one phototrophic alga.
  • Said second aqueous suspension of algal biomass is discharged from said one or more bioreactors or from said one or more fermenters and subsequently joined to said first concentrated aqueous suspension of algal biomass obtaining a third aqueous suspension of algal biomass .
  • Said third aqueous suspension of algal biomass is subjected to concentration, so as to obtain a second concentrated aqueous suspension of algal biomass.
  • Said concentration can be carried out according to what is described above for the concentration of said first aqueous suspension of algal biomass. It is preferably carried out by centrifugation.
  • said third aqueous suspension of algal biomass can be subjected to flocculation.
  • Said flocculation can be carried out according to what is described above for the concentration of said first aqueous suspension of algal biomass.
  • said second concentrated aqueous suspension of algal biomass can have a concentration of dry algal biomass (i.e. of dry phototrophic alga + dry heterotrophic alga) ranging from 4% by weight to 30% by weight, more preferably ranging from 5% by weight to 25% by weight, with respect to the total weight of said second concentrated aqueous suspension of algal biomass .
  • dry algal biomass i.e. of dry phototrophic alga + dry heterotrophic alga
  • the aqueous phase which is obtained from the concentration of said third aqueous suspension of algal biomass, as it is in a limited quantity, can be eliminated as blowdown, in order to maintain the levels of salts and of organic substances which can optionally accumulate during said process within the management limits of the production plant used in said process .
  • said process comprises eliminating the aqueous phase which is obtained from the concentration of said third aqueous suspension of algal biomass as blowdown.
  • Said aqueous phase (blowdown) can optionally be fed to a waters treatment plant .
  • Said thermal treatment comprises heating said second concentrated aqueous suspension of algal biomass in a container, under pressure.
  • Said thermal treatment can be carried out by operating in different ways such as, for example “batch”, “semi-batch”, or in continuous.
  • said thermal treatment can be carried out at a temperature ranging from 80°C to 350°C, preferably from 150°C to 330°C.
  • the pressure is preferably maintained at values which are such as to keep at least part of the water in said second concentrated aqueous suspension of algal biomass in the liquid state.
  • said thermal treatment can be carried out at a pressure ranging from 0.1 MPa to 25 MPa, preferably from 0.5 MPa to 18 MPa.
  • said thermal treatment can be carried out for a time equal to or higher than 15 minutes, preferably ranging from 30 minutes to 3 hours.
  • the thermal energy necessary for said thermal treatment can totally or partially derive from the thermal recovery which takes place within the production cycle, or from the combustion of energy vectors such as, for example, methane gas, biogas, LPG, mineral oil, coal, etc., or from the combustion of bio- oil (bio-oil which can be that obtained from the process object of the present invention)
  • the thermal energy can derive from solar energy.
  • the thermal energy necessary for said thermal treatment can be transmitted directly such as, for example, by high-temperature vapour injection, or indirectly such as, for example, by means of thermal exchange surfaces.
  • the transmission of said thermal energy can take place in a single step or in more than one step.
  • the breakage takes place of the cell membranes of said phototrophic alga and of said heterotrophic alga present in said second concentrated aqueous suspension of algal biomass obtaining a mixture including an oily phase comprising bio-oil and an aqueous phase comprising organic compounds such as, for example, sugars (e.g., glucose), carboxylic acids (e.g., acetic acid), glucoside fractions, proteins, deriving from the thermal treatment (thermal hydrolysis) of the proteins and of the polysaccharides contained in the algae used. It should be pointed out that part of said proteins and of said polysaccharides, during said thermal treatment, can be converted to bio-oil.
  • sugars e.g., glucose
  • carboxylic acids e.g., acetic acid
  • glucoside fractions glucoside fractions
  • proteins deriving from the thermal treatment (thermal hydrolysis) of the proteins and of the polysaccharides contained in the algae used. It should be pointed out that part of said
  • a gaseous phase is also formed, equal to about 5% by weight - 25% by weight with respect to the total weight (dry weight) of the algal biomass present in said second concentrated aqueous suspension of algal biomass, said gaseous phase comprising about 80% by weight to 95% by weight of carbon dioxide (C0 2 ) with respect to the total weight of said gaseous phase, and from 2% by weight to 20% by weight of hydrocarbons having from 1 to 3 carbon atoms with respect to the total weight of said gaseous phase.
  • C0 2 carbon dioxide
  • heterogas e.g., H 2 S, NH 3
  • other compounds e.g., CO
  • the mixture obtained (oily phase + aqueous phase + gaseous phase) can be cooled to a temperature ranging from 40°C to 90 °C, recovering the heat useful for the above thermal treatment and fed to a separation section in order to separate the above phases: the oily phase, the aqueous phase and the gaseous phase .
  • Said separation is generally carried out by means of techniques known in the art . It can be advantageously carried out, for example, by means of static separators or of centrifuges, or by extraction with at least one organic solvent insoluble in water which can be selected, for example, from hydrocarbon cuts available in refinery, or from derivatives of the processing of bio-oil, in order to obtain the above three phases: an oily phase, an aqueous phase and a gaseous phase .
  • said separation can be carried out by fractionated distillation.
  • Said aqueous phase can be optionally further cooled to a temperature ranging from room temperature (25°C) to 50°C and, as mentioned above, fed to the cultivation of said heterotrophic alga. If impurities are still present (for example, traces of bio-oil, traces of inhibitors, etc.), said aqueous phase can be subjected to a detoxification treatment which can be carried out, for example, by filtration, adsorption, centrifugation, or extraction with an organic solvent .
  • said process comprises feeding the aqueous phase obtained from the thermal treatment of said second concentrated aqueous suspension of algal biomass to the cultivation, under heterotrophic conditions, of said at least one heterotrophic alga.
  • said thermal treatment allows a sterilized aqueous phase to be obtained, consequently without contaminants (e.g., bacteria) which could negatively influence the growth of the heterotrophic algae .
  • Said gaseous phase is generally upgraded in its hydrocarbon component as combustible gas.
  • said gaseous phase can be optionally further cooled to a temperature ranging from room temperature (25°C) to 50°C and recycled to the cultivation of said phototrophic alga as carbon dioxide source (C0 2 ) .
  • the process, object of the present invention allows the bio-oil to be recovered with a yield ranging from 15% to 70%, preferably from 20% to 60%, said yield being calculated with respect to the total weight (dry weight) of the algal biomass present in said second concentrated aqueous suspension of algal biomass.
  • the bio-oil obtained by the above process can be used as such, or it can be fed to the subsequent processing phases in order to transform it, for example, into biofuel by treatments known in the art, such as, for example, hydrogenation or cracking.
  • At least one phototrophic alga preferably a phototrophic microalga, which grows, for example, in seawater, is cultivated, under photoautotrophic conditions, in open ponds and/or in bioreactors (A) , obtaining a first aqueous suspension of algal biomass (5) .
  • an aqueous stream (3) comprising nutrients and/or oligoelements such as, for example, nitrates, phosphates, copper, iron.
  • the aqueous stream (3) is not necessary (not represented in Figure 1) .
  • Said first aqueous suspension of algal biomass (5) is collected by emptying, in continuous or at regular intervals, the open ponds and/or the bioreactors (A) and fed to a concentration area (B) (e.g., to a settler) in order to obtain a first concentrated aqueous suspension of algal biomass (8) [e.g., concentration of dry algal biomass (i.e. of dry phototrophic alga) equal to 3% by weight with respect to the total weight of said first concentrated aqueous suspension of algal biomass] .
  • concentration area e.g., concentration of dry algal biomass (i.e. of dry phototrophic alga) equal to 3% by weight with respect to the total weight of said first concentrated aqueous suspension of algal biomass
  • the aqueous phase which is released from the concentration of said first aqueous suspension of algal biomass (5) is fed to the process, i.e. it is fed (7) to the open ponds or to the bioreactors (A) , in order to be used as water in the production of said phototrophic microalga.
  • At least one heterotrophic alga is cultivated, under heterotrophic conditions, in the presence of the aqueous phase (15) as cultivation water, in bioreactors and/or in fermenters (E) , obtaining a second aqueous suspension of algal biomass (9) .
  • an aqueous stream comprising nutrients and/or oligoelements such as, for example, nitrates, phosphates, copper, iron;
  • an aqueous stream (19) comprising an organic base (e.g., potassium hydroxide) in order to maintain the pH of the cultivation water at optimum values for the growth of said heterotrophic tnicroalga (e.g., values ranging from 6 to 8) .
  • an organic base e.g., potassium hydroxide
  • Said second aqueous suspension of algal biomass (9) is collected by emptying, in continuous or at regular intervals, the bioreactors and/or the fermenters (E) and is subsequently joined with said first concentrated aqueous suspension of algal biomass (8) obtaining a third aqueous suspension of algal biomass (10) which is fed to a concentration area (C) (e.g., to a centrifuge) in order to obtain a second concentrated aqueous suspension of algal biomass (12) [e.g., concentration of dry algal biomass (i.e. dry phototrophic alga + dry heterotrophic alga) equal to 20% by weight with respect to the total weight of said second concentrated aqueous suspension of algal biomass) .
  • concentration area e.e. dry phototrophic alga + dry heterotrophic alga
  • blowdown (11) The aqueous phase which is released from the concentration of said second aqueous suspension of algal biomass (9) is eliminated as blowdown (11) : in this way, as mentioned above, as the production cycle is subject to the possible accumulation of salts and organic substances, said blowdown (11) allows the levels of these products to be maintained within the management limits of the production plant used in said process. Said blowdown can be optionally fed to a water treatment plant (not represented in Figure 1) .
  • Said second concentrated aqueous suspension of algal biomass (12) is preheated in a heat exchange section (not represented in Figure 1) , optionally brought to the correct temperature by means of a heat source (not represented in Figure 1) and then fed to the thermal treatment area, i.e. to a pressurized recipient (D) .
  • Said second concentrated aqueous suspension of algal biomass (12) is brought to the temperature and pressure conditions in said recipient (D) , and is left for residence times which allow a mixture to be obtained, including an oily phase comprising bio-oil and an aqueous phase comprising organic compounds such as, for example, sugars (e.g., glucose), carboxylic acids (e.g., acetic acid), glucoside fractions, proteins, deriving from the thermal treatment (thermal hydrolysis) of the proteins and polysaccharides contained both in the phototrophic alga and in the heterotrophic alga used.
  • sugars e.g., glucose
  • carboxylic acids e.g., acetic acid
  • glucoside fractions e.g., glucoside fractions
  • proteins deriving from the thermal treatment (thermal hydrolysis) of the proteins and polysaccharides contained both in the phototrophic alga and in the heterotrophic alga used.
  • Said mixture is discharged from said recipient (D) , cooled in a heat exchange section (not represented in Figure 1) and fed to a separation section (not represented in Figure 1) in order to recover:
  • an oily phase (14) comprising bio-oil which can be used as such or fed to subsequent processing phases for transforming it into biofuel by means of hydrogenation or cracking treatments, for example (not represented in Figure 1) ;
  • an aqueous phase (15) , rich in organic compounds such as, for example, sugars (e.g., glucose), carboxylic acid (e.g., acetic acid), glucoside fractions, proteins, which is fed to the cultivation bioreactors and/or fermenters (E) , under heterotrophic conditions, of said heterotrophic alga;
  • sugars e.g., glucose
  • carboxylic acid e.g., acetic acid
  • glucoside fractions e.g., proteins
  • a gaseous phase (13) essentially comprising carbon dioxide (C0 2 ) and gaseous hydrocarbons having from 1 to 3 carbon atoms, which can be upgraded in its hydrocarbon component as fuel gas, or fed to the cultivation open ponds or bioreactors of said phototrophic alga (A) as carbon dioxide (C0 2 ) source (not represented in Figure 1) .
  • a cultivation open pond with seawater was used, having a total surface of 2.33 m 2 , a depth of 16.1 cm, for a total volume of liquid equal to 375 litres.
  • the surface of the pond was exposed for 10 hours a day to solar light and a water evaporation equal to about 23.3 kg/day was registered.
  • the productivity proved to be equal to 40 g of dry alga/m 2 /day .
  • a bioreactor having a volume of 0.0015 m 3 (1.5 litres) was used, containing a total liquid volume equal to 9 x 10 "4 m 3 (0.9 litres) .
  • a heterotrophic microalga belonging to the heterotrophic strain Nannochloropsis was used.
  • the productivity proved to be equal to 15.1 g of dry alga/day.
  • a diluted aqueous solution of a polyacrylamide was added, as flocculating agent, to said first aqueous suspension of algal biomass (5) (not represented in Figure 1) , in a quantity equal to 1% by weight with respect to the concentration of dry algal biomass (i.e. dry autotrophic algae) present in said first aqueous suspension of algal biomass.
  • Said first aqueous suspension of algal biomass (5) was subsequently fed to the concentration area (B) , i.e. to a settler, obtaining:
  • a first concentrated aqueous suspension of algal biomass having a concentration of dry algal biomass (i.e. dry phototrophic alga) equal to 3% by weight with respect to the total weight of said first concentrated aqueous suspension of algal biomass: 3.1 kg/day;
  • an aqueous phase deriving from the thermal treatment carried out in (D) rich in organic compounds such as, for example sugars (e.g., glucose), carboxylic acids (e.g., acetic acid), glucoside fractions, proteins, for a total of 31 g/1: 0.5 kg/day;
  • an aqueous stream comprising nutrients containing nitrogen and phosphorous in order to maintain a concentration of nitrogen equal to 3,200 ppm and a concentration of phosphorous equal to 160 ppm;
  • a second aqueous suspension of algal biomass 9 were discharged from the bioreactor (E) , having a concentration of dry algal biomass (i.e. dry heterotrophic algae) equal to 1.5% by weight with respect to the total weight of said second aqueous suspension of algal biomass, which was joined to said first concentrated aqueous suspension of algal biomass (8) , obtaining a third aqueous suspension of algal biomass (10) .
  • dry algal biomass i.e. dry heterotrophic algae
  • Said third aqueous suspension of algal biomass (10) was fed to the concentration area (C) , i.e. to a centrifuge, obtaining:
  • a second concentrated aqueous suspension of algal biomass having a concentration of dry algal biomass (i.e. dry phototrophic alga + dry heterotrophic alga) equal to 20% by weight with respect to the total weight of said second aqueous suspension of algal biomass: 0,5 kg/day;
  • Said second concentrated aqueous suspension of algal biomass (12) was preheated to 300°C by means of a heat exchanger (not represented in Figure 1) and subsequently fed to the thermal treatment, i.e. to a pressurized recipient (D) in which it was kept at this temperature, at a pressure of 10.3 MPa, for 2 hours.
  • an oily phase comprising bio-oil which can be used as such or fed to the subsequent processing phases to transform it into biofuel by means of hydrogenation or cracking treatments, for example (not represented in Figure 1) : 41 g/day;
  • an aqueous phase rich in organic compounds such as, for example, sugars (e.g., glucose), carboxylic acids (e.g., acetic acid), glucoside fractions, proteins, which is fed to the cultivation bioreactors (E) , under heterotrophic conditions, of said heterotrophic alga: 0.5 kg/day;
  • sugars e.g., glucose
  • carboxylic acids e.g., acetic acid
  • glucoside fractions e.g., proteins

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Zoology (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Wood Science & Technology (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Bioinformatics & Cheminformatics (AREA)
  • General Chemical & Material Sciences (AREA)
  • Biotechnology (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Health & Medical Sciences (AREA)
  • Biochemistry (AREA)
  • Microbiology (AREA)
  • General Engineering & Computer Science (AREA)
  • General Health & Medical Sciences (AREA)
  • Genetics & Genomics (AREA)
  • Preparation Of Compounds By Using Micro-Organisms (AREA)
  • Apparatus Associated With Microorganisms And Enzymes (AREA)
  • Micro-Organisms Or Cultivation Processes Thereof (AREA)
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Abstract

L'invention porte sur un procédé pour la production d'huile biologique à partir d'algues phototrophes et hétérotrophes consistant à : cultiver au moins une algue phototrophe, dans des conditions photoautotrophes, afin d'obtenir une première suspension aqueuse de biomasse algale; cultiver au moins une algue hétérotrophe, dans des conditions hétérotrophes, afin d'obtenir une deuxième suspension aqueuse de biomasse algale; soumettre ladite première suspension aqueuse de biomasse algale à une concentration afin d'obtenir une première suspension aqueuse concentrée de biomasse algale; combiner ladite première suspension aqueuse concentrée de biomasse algale avec ladite deuxième suspension aqueuse de biomasse algale ce qui permet d'obtenir une troisième suspension aqueuse de biomasse algale; soumettre ladite troisième suspension aqueuse de biomasse algale à une concentration afin d'obtenir une seconde suspension aqueuse concentrée de biomasse algale; soumettre ladite seconde suspension aqueuse concentrée de biomasse algale à un traitement thermique afin d'obtenir une phase huileuse comprenant de l'huile biologique et une phase aqueuse comprenant des composés organiques.
PCT/IB2010/003179 2009-12-09 2010-12-07 Procédé pour la production d'huile biologique à partir d'algues phototrophes et hétérotrophes WO2011070432A1 (fr)

Priority Applications (2)

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MA35033A MA33900B1 (fr) 2009-12-09 2010-12-07 Procédé pour la production d'huile biologique à partir d'algues phototrophes et heterotrophes
TNP2012000275A TN2012000275A1 (en) 2009-12-09 2012-05-30 Process for the production of bio-oil from phototrophic and heterotrophic algae

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ITMI2009A002164A IT1396940B1 (it) 2009-12-09 2009-12-09 Procedimento per la produzione di bio-olio da alghe fototrofe ed eterotrofe
ITMI2009A002164 2009-12-09

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CN115011641A (zh) * 2022-05-25 2022-09-06 重庆理工大学 一种通过壳聚糖强化微藻产油与固碳的方法

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CN115011641A (zh) * 2022-05-25 2022-09-06 重庆理工大学 一种通过壳聚糖强化微藻产油与固碳的方法

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MA33900B1 (fr) 2013-01-02
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TN2012000275A1 (en) 2013-12-12

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