System for the cultivation of microalgae

Abstract

The invention refers to the biotechnological sector of growth processes of photosynthetic organisms such as microalgae, and relates to a system (100) for the cultivation of microalgae (A) comprising: mains water supply means (10); a treatment section (20) for the incoming water; a preparation section (30) of a concentrated solution (SC) of treated water and nutrients (N); a general loading and compensation tank (40); a growth section (50) for said microalgae (A) comprising a plurality of reactors (R); means for feeding (60) a growth gas in said reactors (R); a separation section (70) of said microalgae (A) from the growth liquid and total recovery of the liquid itself; a hydraulic circuit connecting said sections of said system (100); - a command and control unit (80). Said general tank (40) is adapted to contain a growth solution, comprising said concentrated solution (SC), treated water for its dilution and recovery water comprising said growth liquid, to distribute it to said reactors (R) so as to create, within each reactor (R), a growth environment for said microalgae (A).

Description

[0001] SYSTEM FOR THE CULTIVATION OF MICROALGAE

[0002] Technical field of application

[0003] The invention refers to the biotechnological sector of growth processes of photosynthetic organisms such as microalgae, and in particular relates to a system for the cultivation of microalgae.

[0004] Prior art

[0005] Today, much of the world's industrial production of microalgae is achieved using open-air cultivation systems in tropical and subtropical areas, where yields can be optimised by making the best use of sunlight as an energy source throughout the year.

[0006] The systems for the industrial production of microalgae on a large scale comprise “open” systems where the microorganisms are grown in contact with external light and air, i.e., in shallow open ponds where the algal culture is static or moved by agitators or by blowing air.

[0007] In many non-tropical regions, open-air algal culture systems often have the disadvantage of being located in unfavourable climatic conditions which do not allow for continuous production cycles throughout the year, thus requiring algae production and harvesting to be maximized for periods limited to the warmer months.

[0008] Another problem related to open pond cultivation is the excessive evaporation of the liquid, especially in hot climates, with consequent progressive variation in salinity and the possible loss of essential components. The volumes evaporated daily require constant replenishment of fresh water to avoid increasing the salinity of the medium in the pond.

[0009] Open ponds are more exposed to contamination by bacteria, protozoa and other microalgae which can proliferate, competing for growth with the strain of interest. Such susceptibility to contamination makes this type of technique less preferable in a context where the quality control of the product, used for purposes such as food, and thus in conditions where health problems are already serious, must be maximum.

[0010] Further critical issues with open-type algal growth systems include: the low photosynthetic efficiency of the cells which, due to a sometimes inefficient medium movement system, i.e., with a very poor mixing rate, leads to low biomass productivity (microalgae), a lower cultivation density, which requires high volumes of water to be managed, moved and stored in the production phase, as well as in the subsequent phases for processing the biomass; a low carbonation efficiency, also due to a limited height of the free surface, which favours the diffusion of CO2 in the atmosphere; the need for large cultivation surfaces.

[0011] Presentation of the invention

[0012] The object of the invention is to eliminate such drawbacks by creating a system for the cultivation of microalgae which is not subject to external boundary conditions, which ensures stable and constant growth of the microalgae, which is easily manageable and controllable in the parameters involved, which can be configured in the optimal parameters based on the species being cultivated, which does not require excessive maintenance, which does not have large quantities of waste material, which does not waste water.

[0013] Such objects are achieved with a system for the cultivation of microalgae characterized in that it comprises:

[0014] - mains water supply means;

[0015] - a treatment section for the incoming water supplied;

[0016] - a preparation section of a concentrated solution of treated water and nutrients;

[0017] - a general loading and compensation tank for said system;

[0018] - a growth section for said microalgae comprising a plurality of reactors;

[0019] - means for feeding a growth gas inside said reactors;

[0020] - a separation section of said microalgae from the growth liquid and total recovery of the liquid itself;

[0021] - a hydraulic circuit connecting said sections of said system;

[0022] - a command and control unit adapted to supervise all the functions of the system, where said general tank is adapted to contain a growth solution, comprising said concentrated solution, treated water for its dilution and recovery water, to distribute it to said reactors so as to create, within each reactor, a growth environment for said microalgae.

[0023] Further characteristics of the invention are contained in the dependent claims.

[0024] The system for the cultivation of microalgae according to the invention has numerous advantages.

[0025] The closed system for the cultivation of microalgae which is the subject matter of the present invention allows a closer control of the chemical-physical and biological parameters of the cultivation, as well as a better production yield; it also guarantees an efficient isolation from the external environment, avoiding any contamination.

[0026] The closed cultivation system allows for better quality production with respect to the open systems, as there is no significant contact with the external atmosphere, thus eliminating (or greatly limiting) the presence of impurities in the final product from external pollutants, including those brought by precipitation.

[0027] The system is a closed circuit, it does not envisage the discharge of process water and material to be disposed of: all the products and byproducts are functional to the various phases of the system and reintroduced into the production cycle.

[0028] Brief description of the drawings

[0029] These and further advantages of the invention will be more evident below, in which a preferred embodiment method is described, by way of non-limiting example, and with the help of the figures where:

[0030] Figure 1 depicts, by means of a block diagram, a system for the cultivation of microalgae made according to the invention;

[0031] Figures 2a and 2b depict, in layout mode, two sections of the diagrammatic system of Figure 1 ;

[0032] Figure 3 depicts, in layout mode, a system for the cultivation of microalgae made according to a possible variant of the invention. Detailed description of a preferred embodiment of the invention

[0033] Referring to Figures 1 -3, a system 100 is illustrated for the implementation of growth processes of photosynthetic organisms such as microalgae A.

[0034] As illustrated in the block diagram of Figure 1 , said system 100 essentially comprises:

[0035] - mains water supply means 10;

[0036] - a treatment section 20 for the incoming water supplied;

[0037] - a preparation section 30 of a concentrated solution SC of treated water and nutrients N;

[0038] - a general loading and compensation tank 40 for said system 100;

[0039] - a growth section 50 for said microalgae A comprising a plurality of reactors R;

[0040] - means for feeding 60 a growth gas inside said reactors R;

[0041] - a separation section 70 of the microalgae A produced in the reactors R from the growth liquid and total recovery thereof;

[0042] - a hydraulic circuit connecting said sections of said system 100.

[0043] Said general tank 40, said growth section 50 and said separation section 70 constitute what is called a growth module 101 .

[0044] Said system 100 then comprises a command and control unit 80 adapted to automatically supervise all the functions of the system 100, using known type sensors located in the various sections of the system.

[0045] Figure 2a illustrates a first section of the system 100 dedicated to the preparation of said concentrated solution SC of treated water and nutrients N, i.e., the basis for recreating a growth environment for said microalgae A.

[0046] Said treatment section 20 for the incoming water supplied comprises, arranged in series, a filtering mesh filter 21 , preferably 0.5 micron, a softener 22, and a first storage tank 23 of 10 m3.

[0047] Between said treatment section 20 for the incoming water supplied and said preparation section 30 of a concentrated solution SC of treated water and nutrients N, a first disinfectant filter 24 with UV rays is arranged.

[0048] Downstream of said first storage tank 23 there is a first pump R1 adapted to direct the treated water along two different lines belonging to said hydraulic circuit: a first supply line L1 of treated water to said preparation section 30 of a concentrated solution SC and a second supply line L2 of treated water directly to said general tank 40.

[0049] Said preparation section 30 of a concentrated solution SC of treated water and nutrients N comprises supply means 33 of nutrients N in powder form, a dosing battery 36 of said nutrients N and a mixing tank 31 of said nutrients N in said water.

[0050] Said supply means 33 of nutrients N in powder form comprise a stainless steel nozzle suction system 34 powered by a compressor 35.

[0051] Said dosing battery 36 of said nutrients N comprises a plurality of hoppers 37, each for a specific nutrient N, hermetically sealed and provided with a volumetric dispenser 38.

[0052] Each nozzle is adapted to suck a specific nutrient N in powder form from a specific storage container to transfer it into a corresponding dedicated hopper 37.

[0053] Said dosing battery 36 of said nutrients N comprises a gravimetric loading hopper 39 placed underneath said hoppers 37 of the individual powders, adapted to collect all the pre-dosed nutrients N and channel them into said mixing tank 31 .

[0054] Said mixing tank 31 is advantageously a 1 m3 tank and comprises an agitator 32 placed therein.

[0055] The treated water from the storage tank 23 is also conveyed into said mixing tank 31 via said first supply line L1 of the hydraulic circuit.

[0056] Inside the mixing tank 31 there is 1 m3 of the concentrated solution SC of nutrients N and treated water.

[0057] Once the concentrated solution SC has been composed, it is sent, along a third supply line L3 of said hydraulic system and by means of a pump P2, to the 15 m3 general tank 40 which is also filled with treated water via the aforementioned second supply line L2 of the hydraulic system: a growth solution SR is thus composed inside the general tank 40, comprising said concentrated solution SC, treated water for its dilution, and growth liquid separated from the microalgae A (as we will see in the following description).

[0058] Figure 2b illustrates a second section of the system 100 dedicated to the actual cultivation of microalgae A.

[0059] Figure 2b actually illustrates a single growth module 101 .

[0060] As mentioned above, said growth section 50 comprises a plurality of vertical column reactors R, better defined as photoreactors, in which, thanks to the presence of artificial light, the photosynthetic reaction underlying the growth processes of microalgae A actually occurs.

[0061] Said growth section 50 for said microalgae A comprises a first R1 , a second R2, a third R3 and a fourth R4 group of reactors R: in each group R1 , R2, R3, R4 the reactors R are connected in series with each other, while said groups R1 , R2, R3, R4 are arranged in parallel with each other so as to define a growth module 101 .

[0062] Each group R1 , R2, R3, R4 comprises 17 reactors, and said growth module 101 therefore comprises a total of 68 reactors.

[0063] Each reactor R comprises:

[0064] - a container, adapted to contain said growth solution SR for said microalgae A therein;

[0065] - an inlet for said growth solution SR and an outlet for said solution enriched with the developed and grown microalgae A;

[0066] - a lamp for illuminating the microalgae A growing inside said container;

[0067] - an inlet for a pressurized growth gas in said container connected to said supply means 60.

[0068] Ambient air, which therefore constitutes said growth gas, is blown into each reactor R, injected from below through a flexible tube. Air is injected into the reactor R under light pressure through a side channel blower.

[0069] It is evident that the growth gas can have another composition, for example with a higher content of CO2. Said general tank 40 and said reactors R are connected by means of a fourth supply line L4 of said hydraulic circuit adapted to intercept the inlet of each reactor R: the growth solution SR is thus transferred from the general tank 40 to the individual reactors R.

[0070] A pump P3 and a plurality of automatic valves are arranged along the fourth supply line L4.

[0071] Said hydraulic circuit then comprises a fifth supply line L5 adapted to collect the solution enriched with microalgae A developed and grown inside the reactors R.

[0072] Manual valves are provided along the fifth supply line L5, which are used during system maintenance.

[0073] Said fifth supply line L5 is also directly connected to the pump P3 of the fourth supply line L4: said pump P3 can thus work in delivery for said fourth supply line L4 and in suction for said fifth supply line L5 based on the opening or closing of said valves.

[0074] Said fifth supply line L5 of the hydraulic circuit conveys the solution enriched with the microalgae A developed and grown inside the reactors R towards a specific treatment section, i.e., towards a separation section 70 of the microalgae A produced from the exhausted growth solution SR which, in addition to water, still comprises residual nutrients N.

[0075] The separation section 70 of the microalgae A comprises a vibrating sieve 71 , i.e., a vibrating screen.

[0076] Said system 100 then comprises a drying station (not illustrated) for the microalgae A extracted from said separation section 70, and a UV disinfectant filter 72 for the exhausted growth solution SR deprived of the microalgae A.

[0077] Said hydraulic circuit 100 comprises a sixth supply line L6 of said liquid, or of said exhausted growth solution SR, in said general tank 40, after passing through said disinfectant filter 72 with UV rays thanks to a pump P4, so that it can be reused for the dilution of the concentrated solution SC in a closed-circuit system 100 perspective.

[0078] The system 100 is controlled by a command and control unit 80 comprising a PLC system provided with a touchscreen.

[0079] Said PLC is provided with all the inputs and outputs necessary for management, through specific signals coming from probes and sensors:

[0080] • of the pneumatic load in suction of the nutrients N in powder form;

[0081] • of the volumetric dispensers 38 of nutrients N;

[0082] • of the gravimetric loading hopper 39 and of the pneumatic transfer of the concentrated solution SC to the general tank 40;

[0083] • of the water supply lines L1 , L2 of the hydraulic circuit to the mixing tank 31 and to the general tank 40;

[0084] • of the supply line L4 of the reactors R from the general tank 40;

[0085] • of the supply line L5 from the reactors R towards the vibrating sieve 71 ;

[0086] • of the compressed air circuit for insufflation into the reactors R;

[0087] • of the power supply and control circuit of the lighting lamps of the individual reactors R;

[0088] • of the water temperature control circuit in the reactors R through the activation of air extractors and darkening screens.

[0089] Figure 3 illustrates a system 100 for the cultivation of microalgae A made according to a possible variant of the invention, particularly of the type comprising three growth modules 101 , 102, 103 arranged in parallel and fed by the same preparation section 30 of the concentrated solution SC of treated water and nutrients N.

[0090] Each growth module 101 , 102, 103 comprises its own general loading and compensation tank 40 for the system 100, its own growth section 50 for the microalgae A comprising reactors R; its own separation section 70 for the microalgae A, together with all the attached components of the hydraulic circuit.

Claims

CLAIMS1. System (100) for the cultivation of microalgae (A) characterized in that it comprises:- mains water supply means (10);- a treatment section (20) for the incoming water supplied;- a preparation section (30) of a concentrated solution (SC) of treated water and nutrients (N);- a general loading and compensation tank (40) for said system;- a growth section (50) for said microalgae (A) comprising a plurality of reactors (R);- means for feeding (60) a growth gas inside said reactors (R);- a separation section (70) of said microalgae (A) from the growth liquid and total recovery of the liquid itself;- a hydraulic circuit connecting said sections of said system (100);- a command and control unit (80) adapted to supervise all the functions of the system (100), wherein said general tank (40) is adapted to contain a growth solution, comprising said concentrated solution (SC), treated water for its dilution and recovery water including said growth liquid, to distribute it to said reactors (R) so as to create, within each reactor (R), a growth environment for said microalgae (A).

2. System (100) for the cultivation of microalgae (A) according to claim 1 , characterized in that said plurality of reactors (R) comprises a first group of reactors (R1 ) connected in series witheach other.

3. System (100) for the cultivation of microalgae (A) according to claim 2, characterized in that said plurality of reactors (R) includes at least a second group of reactors (R2, R3, R4) connected in series with each other, and said at least one second group of reactors (R2, R3, R4) is arranged in parallel with respect to said first group (R1 ).

4. System (100) for the cultivation of microalgae (A) according to claim 1 , characterized in that said treatment section (20) for the incoming water supplied includes a filtering mesh filter (21 ), a softener (22), a first storage tank (23).

5. System (100) for the cultivation of microalgae (A) according to claim 1 , characterized in that it comprises, between said treatment section (20) for the incoming water supplied and said preparation section (30) of a concentrated solution (SC) of treated water and nutrients (N), a first disinfectant filter (24) with UV rays.

6. System (100) for the cultivation of microalgae (A) according to claim 1 , characterized in that said preparation section (30) of a concentrated solution (SC) of treated water and nutrients (N) comprises a mixing tank ( 31 ) of said nutrients (N) in said treated water comprising an agitator (32).

7. System (100) for the cultivation of microalgae (A) according to claim 6, characterized in that said preparation section (30) of a concentrated solution (SC) of treated water and nutrients (N) includes supply means (33) of said nutrients (N) in powder formcomprising a nozzle suction system (34) powered by a compressor (35).

8. System (100) for the cultivation of microalgae (A) according to claim 6, characterized in that said preparation section (30) of a concentrated solution (SC) of treated water and nutrients (N) comprises a dosing battery (36) of said nutrients comprising a plurality of hoppers (37), each for a specific nutrient substance, hermetically sealed and provided with a volumetric dispenser (38).

9. System (100) for the cultivation of microalgae (A) according to claim 8, characterized in that said dosing battery (36) of said nutrients comprises a gravimetric loading hopper (39) placed underneath said hoppers (37), adapted to collect all the pre-dosed nutrients (N) and channel them into said mixing tank (31 ).

10. System (100) for the cultivation of microalgae (A) according to claim 1 , characterized in that said means (60) for feeding a growth gas inside said reactors (R) comprise a blower.

11. System (100) for the cultivation of microalgae (A) according to claim 1 , characterized in that said microalgae (A) separation section (70) comprises a vibrating sieve (71 ).

12. System (100) for the cultivation of microalgae (A) according to claim 11 , characterized in that it includes a drying station for the microalgae (A) extracted from said separation section (70).

13. System (100) for the cultivation of microalgae (A) according to claim 1 , characterized in that it includes a second UV disinfectant filter (72) interposed between said separation section (70) of themicroalgae (A) and said general tank (40).

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