Rotational fluid dynamics system for microalgae harvesting

Abstract

The present disclosure provides a system for harvesting microalgae, comprising a cylindrical vessel configured to contain a suspension of microalgae, the cylindrical vessel having a longitudinal axis oriented predominantly perpendicular to gravity. A rotation mechanism is configured to rotate the cylindrical vessel around its longitudinal axis at a speed sufficient to induce either suspension or aggregation or both of the microalgae through fluid dynamics and sedimentation. Algae can be cultivated directly in the vessel. A harvesting mechanism is configured to remove aggregated microalgae from the cylindrical vessel. Different configurations for the harvesting mechanism are proposed and viable for different applications. The system enables efficient microalgae cultivation and harvesting without chemical flocculants by utilizing controlled fluid dynamics to promote natural aggregation, thereby reducing energy consumption and simplifying downstream processing.

Description

ROTATIONAL FLUID DYNAMICS SYSTEM FOR MICROALGAE HARVESTINGBACKGROUNDRelated

[0001] This application claims the benefit of priority of U.S. Provisional Application No.63 / 778,135, filed on March 26, 2025, including the references cited therein, the entire content of which is relied upon and incorporated herein by reference in its entirety.Field

[0002] The present disclosure relates to microalgae harvesting systems, and more particularly to a fluid dynamics-based method for cultivating, aggregating and harvesting various materials, and especially suspended organic matter such as microorganisms or microalgae using controlled rotational motion of a cylindrical vessel.of the Related Art

[0003] Microalgae have gained significant attention in recent years as a promising source of biofuels, nutraceuticals, and other high-value products. These microscopic photosynthetic organisms can be cultivated using minimal resources, including non-arable land and wastewater streams, making them an attractive option for sustainable production of various compounds. However, the widespread commercial adoption of microalgae-based technologies faces several challenges, with harvesting being one of the primary bottlenecks.

[0004] Harvesting microalgae from dilute cultures presents considerable difficulties due to the small size of the cells, typically ranging from 1 to 30 micrometers, and their low concentration in the growth medium. Traditional harvesting methods include centrifugation, filtration, sedimentation, and flocculation, each with its own set of advantages and limitations.1130761.00573 / 157562042v.1Centrifugation is effective at separating microalgae from the culture medium but requires substantial energy input, leading to high operational costs. Filtration can achieve good recovery rates but often suffers from membrane fouling and clogging, necessitating frequent maintenance and replacement of filter materials. Sedimentation is a low-energy option but is generally impractical for harvesting colloidal microalgal cells due to their slow settling velocities.Flocculation techniques aim to aggregate cells to enhance sedimentation, but chemical flocculants can be expensive and may contaminate the final product.

[0005] The energy consumption associated with harvesting can account for a substantial portion of the total production costs in microalgae cultivation systems. This energy requirement not only impacts the economic viability of microalgae-based products but also affects the overall sustainability of the process. Consequently, there is a growing interest in developing more efficient and cost-effective harvesting technologies that can overcome these limitations.

[0006] Furthermore, the choice of harvesting method can have implications beyond mere separation efficiency. Some techniques may cause cell damage or introduce contaminants, which can be particularly problematic when the goal is to produce high-value compounds for food or pharmaceutical applications. The ability to harvest microalgae gently and without the use of chemical additives is thus a desirable characteristic for any new harvesting technology.

[0007] As research in this field progresses, there is an increasing focus on leveraging the natural properties of microalgae, such as their tendency to form aggregates under certain conditions, to improve harvesting efficiency. Understanding and controlling the fluid dynamics and physicochemical interactions that govern microalgal aggregation, as the present disclosure does, could potentially lead to innovative harvesting solutions that are both energy-efficient and compatible with various downstream processing requirements.2130761.00573 / 157562042v.1

[0008] Advancements in microalgae harvesting technology have the potential to not only reduce production costs but also to enable new applications and markets for microalgal products.Improved harvesting methods could contribute to making microalgae-based biofuels more competitive with conventional fossil fuels and facilitate the development of biorefineries that produce a range of valuable co-products from a single cultivation process.

[0009] In light of these considerations, there is a continued need for research and development of novel approaches to microalgae harvesting that can address the current limitations and unlock the full potential of microalgae as a sustainable resource for various industries.SUMMARY

[0010] This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

[0011] According to an aspect of the present disclosure, a system for harvesting microalgae is provided. The system includes a cylindrical vessel configured to contain a suspension of microalgae. The cylindrical vessel has an axis (e.g., a longitudinal axis for an elongated cylinder) oriented predominantly perpendicular to gravity, and in some embodiments the vessel is tilted at an angle sufficient to facilitate the recovery of biomass deposits. For example, the vessel longitudinal axis can be at an acute angle with respect to a horizontal surface, and in certain embodiments a slight angle to horizontal such as less than 10 degrees, 5-10 degrees, and in certain embodiments 5 degrees. Certain embodiments of the present invention may include a3130761.00573 / 157562042v.1tilting system cable to change the orientation angle of the longitudinal axis to facilitate the collection of agglomerated algae.

[0012] The system also includes a rotation mechanism configured to rotate the cylindrical vessel around its longitudinal axis at a speed sufficient to induce clumping (here termed aggregation) of the microalgae through fluid dynamics.

[0013] The system may further include a conical end portion attached to one end of the cylindrical vessel, where the conical end portion is configured to facilitate collection of aggregated microalgae.

[0014] The cylindrical vessel may include a fixed cap not rotating with the full cylinder (e.g., a dynamic sealing with O-rings) which will be used to fill with fresh culture, accumulate harvested particle and eject exhaust mixture. The fixed cap can be also used to introduce air and light into the tank to act as a bioreactor. The geometries for the endcap can be conical, toroidal or funnel shaped, as showed in the drawings, depending on the application. The harvesting mechanism may include one or more valves located at the conical end portion.

[0015] Microalgae hold enormous potential for producing biofuels as they are aquatic photosynthetic organisms that require low energy inputs and can be grown in non-arable lands using high-salinity and wastewater streams. Microalgal biofuels outperform in productivity and sustainability those obtained by terrestrial plants. Still, further cost reductions are needed. Of note, microalgae are also a well-known source of proteins and lipids of high value for the food and pharmaceutical industries. Thus, abiorefinery approach, which co-extracts multiple valuable compounds from the same culture, is key for cost-effective biofuel production. According to a recent NREL report (2024), integrating algal protein production for human consumption can reduce the minimum algal fuel selling price (MFSP) from $8.69 to $3.72 per gasoline gallon4130761.00573 / 157562042v.1equivalent, enhancing economic feasibility. However, the necessity of dewatering a highly diluted biomass, while respecting the food-grade restrictions necessary for the biorefinery approach creates big technical challenges. This makes the design of the harvesting facility a crucial feature, particularly considering that harvesting accounts for 20-30% of the total production costs at industrial scale (Li et al., 2021) with some estimates reaching 90% for open pond systems.

[0016] Conventional harvesting methods, which include centrifugation, filtration, sedimentation, and flocculation, face efficiency, cost, and sustainability challenges (Zhu et al., 2024).Centrifugation and filtration achieve high recovery rates (up to 90%), but they demand significant energy inputs (3-6 kWh / m3 for centrifugation and 1-3 kWh / m3 for filtration) and high operational costs. Moreover, filtration membranes clog easily, requiring frequent maintenance. Also, both methods cause cell damage, compromising product quality and rendering it unsuitable for the co-production of food or pharmaceutical-grade products.Sedimentation is energy-efficient but impractical for colloidal cells, with recovery rates of only 20% due to microalgae's low sinking velocity. Flocculation accelerates sedimentation through algal aggregation and is currently achieved with biological, chemical, and electrochemical methods.

[0017] Biological methods risk contamination and competition between organisms, while chemical methods involve expensive or toxic additives that complicate disposal. Electrochemical methods, though effective, cause metal ion contamination, active chlorine generation, and are energy-intensive. None of these flocculation approaches are currently suitable to achieve satisfactory harvesting systems compared to mechanical methods, which, despite higher costs5130761.00573 / 157562042v.1and the cell damage, remain the most viable option. However, physical methods for algal aggregation like the proposed technology have been unexplored.

[0018] These and other objects of the disclosure, as well as many of the intended advantages thereof, will become more readily apparent when reference is made to the following description, taken in conjunction with the accompanying drawings. This summary is not intended to identify all essential features of the claimed subject matter, nor is it intended for use in determining the scope of the claimed subject matter. It is to be understood that both the foregoing general description and the following detailed description are exemplary and are intended to provide an overview or framework to understand the nature and character of the disclosure.BRIEF DESCRIPTION OF THE FIGURES

[0019] The accompanying drawings are incorporated in and constitute a part of this specification. It is to be understood that the drawings illustrate only some examples of the disclosure and other examples or combinations of various examples that are not specifically illustrated in the figures may still fall within the scope of this disclosure. Examples will now be described with additional detail through the use of the drawings, in which:

[0020] FIGS. 1 A, IB show an overview of the rolling tank system.

[0021] FIG. 2 shows a tilting mechanism.

[0022] FIGS. 3A, 3B show a single funnel cap.

[0023] FIGS. 4A, 4B show a double funnel cap.

[0024] FIGS. 5A, 5B show a toroidal cap.

[0025] FIGS. 6A, 6B, 6C show a funnel cap.

[0026] FIGS. 7A, 7B, 7C show a V-shape cap.6130761.00573 / 157562042v.1

[0027] FIG. 8 shows algal culture before aggregation process (left) and after 3h low speed rolling (right).

[0028] FIGS. 9A-9E illustrate operation of the harvesting system.DETAILED DESCRIPTION

[0029] In describing the illustrative, non-limiting embodiments illustrated in the drawings, specific terminology will be resorted to for the sake of clarity. However, the disclosure is not intended to be limited to the specific terms so selected, and it is to be understood that each specific term includes all technical equivalents that operate in similar manner to accomplish a similar purpose. Several embodiments are described for illustrative purposes, it being understood that the description and claims are not limited to the illustrated embodiments and other embodiments not specifically shown in the drawings may also be within the scope of this disclosure. The following description sets forth exemplary aspects of the present disclosure. It should be recognized, however, that such description is not intended as a limitation on the scope of the present disclosure. Rather, the description also encompasses combinations and modifications to those exemplary aspects described herein.

[0030] Turning to the drawings, FIG. 1 shows an illustrative example embodiment of a microalgae harvesting system 10, and in particular a rotational fluid dynamics system for microalgae harvesting. The harvesting system 10 includes a tank assembly 100, a support assembly 200, and rotation or mixing assembly 300. The tank assembly 100 is a container that houses the algae solution, the support assembly 200 supports the tank assembly 100, and the mixing assembly 300 moves the tank assembly 100 to mix the contents.7130761.00573 / 157562042v.1

[0031] The present system 10 relates to a rotational fluid dynamics system for microalgae harvesting or cultivation and harvesting. This innovative approach utilizes controlled fluiddynamic conditions to induce aggregation of microalgal cells, facilitating their efficient harvesting. The slow rotational motion of the tank generates a well-organized, predominantly laminar flow field characterized by localized regions of elevated shear. This controlled hydrodynamic environment promotes repeated intercellular interactions and collisions among microalgae, facilitating aggregation without the need for chemical additives. Aggregates include single microalgal cells or chains, sticking together to form an exponentially growing structure. The sinking rate increases as the size of the aggregates gets larger, with a size of 2 mm being sufficient for effective sinking and / or exportation towards the collection zone. Of note, aggregate size can range from 50 pm to 2 cm in diameter depending on species, rotational speed and processing time. Due to the low rotational speed of the system, the process operates with reduced energy input while maintaining effective harvesting performance. As a result, the system provides significant advantages over conventional harvesting methods, including improved energy efficiency, reduced operational costs, and enhanced sustainability, particularly for applications requiring chemical-free processing.

[0032] Within localized high-shear regions of the flow, microalgae cells are brought into frequent close contact due to increased collision rates. These hydrodynamic interactions enhance the probability of cell-cell encounters without causing significant cellular damage when shear levels are properly controlled. Microalgae cells naturally possess extracellular polymeric substances (EPS) on their surface, which exhibit adhesive properties. Upon collision, these EPS layers facilitate intercellular binding through physicochemical interactions, including polymer8130761.00573 / 157562042v.1entanglement, hydrogen bonding, and electrostatic attraction. As a result, cells adhere to one another, forming stable aggregates.

[0033] This shear-induced aggregation mechanism enables effective biomass clustering without the addition of external flocculants, thereby preserving product purity and making the process particularly suitable for applications in food, nutraceutical, and pharmaceutical production. Even with smooth walls, rotation of the tank rotates the particles contained therein, with particles at the sides of the tank moving at a higher speed than at the center of the tank, creating a shear flow. In some embodiments, a constant speed in a single unique direction is sufficient. In other embodiments, and depending on the application, the rotation direction can be reversed or alternated (e.g., clockwise, counterclockwise, clockwise), and / or the rotation speed can be varied (e.g., fast clockwise, slow clockwise, slow counterclockwise).

[0034] In some cases, the rotational fluid dynamics system may be applied to harvest or sediment other types of microorganisms beyond microalgae. For example, the system may be used with bacteria or yeasts, potentially expanding its applicability across various biotechnology sectors.

[0035] The disclosed system may also find applications in medium clarification processes. In some cases, the rotational fluid dynamics approach may be employed in food and pharmaceutical industries where efficient separation of particulates from liquid media is desired.

[0036] Additionally, the rotational fluid dynamics system may be adapted for use in algal bioremediation systems. In such applications, the system may enhance the removal of contaminants by improving the aggregation and sedimentation of algae that have absorbed pollutants from the environment.9130761.00573 / 157562042v.1

[0037] The versatility of the rotational fluid dynamics system may allow for its implementation across diverse fields, potentially addressing cultivation and harvesting and separation challenges in multiple industries beyond microalgae cultivation.

[0038] The rotational fluid dynamics system for microalgae harvesting may include a cylindrical vessel. In some cases, the cylindrical vessel may be oriented with its longitudinal axis perpendicular to gravity. The cylindrical vessel may be constructed from various materials suitable for containing algal suspensions, such as stainless steel, glass, or food-grade plastics.

[0039] Tank Assembly 100

[0040] The tank assembly 100 includes a main rolling tank body 110, and tank body end caps 150. The tank body 110 has continuous linear cylindrical tank body wall 112 with an outer surface 101; an inner surface 103; a first tank body end portion 113 with a first tank body open end 114 and a first tank body distal edge 111; a second tank body end portion 115 opposite the first end portion 113, with a second tank body open end 116, and a second tank body distal edge 117. The tank body 110 forms a cylindrical tube with a hollow tank body interior space 120. The tank body 110 can be made of rigid material, such as steel, though other materials can be utilized. In the embodiment shown, the tank body 110 is elongated and defines a tank body longitudinal axis, though in other embodiments the tank body need not be elongated.

[0041] A first tank body end cap 152 is positioned at the first tank body open end 114, and a second tank body end cap 154 is positioned at the second tank body open end 116. The end caps 152, 154 can have the same structure, to be interchangeable, or can vary. And the end caps 150 can have an end cap rotating mating feature to rotatably couple with the tank body outer surface 101, an example of which will be discussed more fully below. A rubber gasket, seal or O-ring is10130761.00573 / 157562042v.1provided at the base of the end cap neck and contacts the distal ends of the tank body to form a liquid-tight seal when the end caps 152, 154 are fully engaged with the tank body end portions. In addition, one or more end cap liquid release valves 156 can optionally be provided in the end cap neck portion to release content from the tank body 110.

[0042] In operation, the second end cap 154 is coupled to the tank body 110, the algae solution is introduced into the tank body interior space 120 through the first tank body open end 114, and the first tank body end cap 152 is coupled to the first tank body open end 114. Other suitable configurations can be provided, for example both end caps 152, 154 can be coupled to the tank body 110, then the solution introduced into the tank body interior space 120 through an input valve 160 (FIG. IB), and a pressure release valve can be coupled to the tank body 110 to release air. As further shown in FIG. IB, a release valve 162 can be located in the second end portion of the tank body 110 (not in the second end cap 154). In this manner, the tank body 110 houses the algae solution.

[0043] In some cases, as shown in FIG. IB, the cylindrical vessel tank body 110 may have a conical end, for example shown as the second end cap 154a. This conical end may be outfitted with swivel openings and valves 160, 164 to facilitate biomass harvest. The valve 162 may allow for controlled extraction of aggregated algal biomass, and is fixed to the tank body 110, and so the biomass can only be extracted when the tank body 110 is rotated to position the outlet valve 162 at the bottom of the tank body 110 and rotation is stopped, as shown in FIG. IB. The swivel connectors 160, 164 can allow for extraction during the rolling motion. In the embodiment shown in FIG. IB, the inlet valve is located at the center of the first end cap 152 and extends therethrough to communicate liquid from the exterior of the tank body 110 to the interior space 120. The inlet valve 160 can swivel as the tank body 110 rotates, so that any tube (or any other11130761.00573 / 157562042v.1fixture) that may be connected to the inlet valve 160 does not rotate and get twisted or decoupled. The outlet valve 162 is positioned in the tank wall 112 and extends therethrough to communicate liquid from the interior space 120 to the exterior of the tank body 110. The inlet and outlet valves 160, 162 allow for continuum feed of fresh algae cultivation, enabling continuous operation. The conical shape concentrates the aggregated microalgae into the tip of the cone 154a, but doesn’t affect the flow of solution. This conical endcap 154a could be used without the need of dynamic O-ring sealing and is fixedly coupled with the main body 110 to rotate together with the main tank body 110.

[0044] The dimensions of the tank assembly 100 may vary depending on the scale of operation. For example, a cylindrical vessel 110 with a volume of 1000 L may be suitable for medium-scale operations. In some cases, smaller vessels 110 with volumes of 10-100 L may be used for laboratory or pilot-scale studies. Larger vessels 110 with volumes of 5000 Lor more may be employed for industrial-scale applications.

[0045] The length-to-diameter ratio of the cylindrical vessel 110 may be optimized to promote efficient algal aggregation or varied for the convenience of installation. In some cases, a length-to-diameter ratio between 2:1 and 5:1 may be used. For example, a 1000 L vessel may have a length of approximately 3 meters and a diameter of 0.8 meters.

[0046] Another important component of this invention is the interchangeable end caps 150, a set of different geometries tank terminations which allow to perform harvesting for different species and in different conditions. The endcaps 150 sealing happens trough a dynamic O-ring sealing. This allows to hold the endcap still while the tank is rotating. The end caps 150, including the conical end cap 154a of FIG. IB, can have a linear neck portion with a seated O-ring that slidably couples with external outer surface of the end portion of the tank body 110. As shown in12130761.00573 / 157562042v.1FIG. IB, the junction between the tank body distal end and the conical cap 154a are angled so that liquid flows to the outlet valve 162.

[0047] In some cases, the cylindrical vessel may be equipped with internal baffles or other flowmodifying structures such as humps or bumps. These structures may help to create specific fluid dynamic conditions that enhance algal aggregation. The cylindrical vessel may also include ports or openings for sampling, monitoring, or introducing additional components. In some cases, these ports may be sealed with removable caps or fitted with sensors for real-time monitoring of process parameters. It is further noted that while the end caps 150 are shown as separate discrete elements, one or both of the end caps 150 can be integrally formed with the tank body wall 112.

[0048] Support Assembly 200

[0049] As shown in FIGS. 1A, IB, 2, a support assembly 200 is provided that supports the tank assembly 100. In the embodiments shown, the support assembly 200 can be a frame assembly with one or more elongated top support or frame members 210, one or more elongated top transverse cross-support or -frame members 220, and one or more support or frame leg members 230.

[0050] In the embodiment where the tank body is elongated, the longitudinal support members 210 are linear and extend parallel to the tank body longitudinal axis. And, the cross-support members 220 extend transverse to the tank body longitudinal axis and in some embodiments can contact the tank body 110 outer surface 101. The cross-support members 220 are shown as linear, but in some embodiments can be curved to match the outer tank body surface 101. The frame assembly 200 design is not limited to the one presented in FIG. 1, and can be adapted to the different applications. Thus, the support assembly 200 can be changed depending on the13130761.00573 / 157562042v.1application of the system 10, including for example, a frame assembly 200 that can be changed to accommodate different sizes of tanks.

[0051] Mixing Assembly 300

[0052] Referring to FIGS. 1 A-3C, the mixing assembly 300 includes, for example, a motor 302; a timing belt 304 and gear 306 that can be changed according to the motor; and ball bearings 308. The gear 306 is a discrete component that is fastened to the tank body 110, about the tank body outer surface 101, or can be integrally formed with the tank body 110. The motor 302 is fixedly coupled to the support assembly 200. For example, the support assembly 200 can include a center post support member 242 that is coupled to and extends downwardly from a crosssupport 220 and / or longitudinal support 210. One or more center diagonal support strut members 240 can also optionally be coupled to the legs 230 and the longitudinal members 210 and / or cross-members 220 to stabilize and support the frame assembly 200. The motor can be coupled to the center post 242 at a position below the top of the longitudinal members 210 and the crosssupport members 220. The timing belt 304 extends around a motor gear on the motor 302 and the tank body gear 306, so that rotation of the motor gear at the motor 302 turns the belt 304, which then turns the body gear 306, which then rotates the tank body 100.

[0053] The ball bearings 306 are situated on one or more (all in some embodiments) of the crosssupport members 220 and extend transverse at the bottom portion of the tank body 110. As shown, multiple ball bearings or wheels can be provided at each cross-support member 220, and the cross-support members 220 can be toward the end portions of the tank body 110, with the tank gear 306 toward the middle of the tank body 110. The ball bearings 308 contact the outer tank surface 101 of the tank wall 112, and allow for rotational motion of the tank body 110 with14130761.00573 / 157562042v.1minimum friction, by activation of the motor 302. Of course, other suitable mixing apparatus 300 can be provided within the spirit and scope of the present disclosure.

[0054] The rotational fluid dynamics system for microalgae harvesting may include the mixing apparatus 300, which can be a rotation mechanism to rotate the tank assembly 100, to induce controlled fluid-dynamic conditions within the cylindrical vessel 110. This rotation mechanism may be designed to slowly rotate the cylindrical vessel and the algal suspension inside it around its longitudinal axis.

[0055] In some cases, the rotation mechanism may comprise an electric motor coupled to a gear reduction system for direct drive or to a timing belt to reduce stress on the motor. The gear reduction system may allow for precise control of the rotational speed, which may be critical for optimizing the aggregation process. The motor and gear system may be connected to the cylindrical vessel via a drive shaft, a gear reduction system or a belt-and-pulley arrangement. In other applications, the vessel may be rotated by driving the support wheels / bearings.

[0056] The rotation mechanism may be capable of operating at various steady or unsteady speeds to accommodate different algal species and cultivation conditions. In some cases, a rotational speed of 1-10 rpm may be used. This relatively slow rotation may induce differential sedimentation and low-shear laminar flow within the algal suspension, promoting cell-to-cell contact and aggregation.

[0057] The rotation of the cylindrical vessel is allowed by the presence of bearing mechanisms on the frame. The bearing mechanisms could consist of ball bearing, roller bearings or wheels. Some embodiments of this invention will consider the use of pins to prevent the axial translation of the cylindrical vessel.15130761.00573 / 157562042v.1

[0058] The energy consumption of the rotation mechanism may be significantly lower compared to conventional harvesting methods. In some cases, the energy consumption may be approximately 2500 J or 1.3 kJ / kg of biomass. This low energy requirement may contribute to the overall efficiency and cost- effectiveness of the harvesting process.

[0059] In some cases, the rotation mechanism may include speed control mechanisms such as variable frequency drives (VFD) or other electronic speed control mechanisms to allow for finetuning of the rotational speed. The speed controller may enable gradual acceleration and deceleration of the cylindrical vessel, which may help prevent disruption of formed algal aggregates during start-up and shutdown procedures.

[0060] The rotation mechanism may also incorporate sensors and control systems to monitor and adjust the rotational speed in real-time. These systems may help maintain optimal aggregation conditions throughout the harvesting process. In some cases, the control system may be programmed to adjust the rotational speed based on factors such as algal concentration, average particle size, species-specific characteristics, or desired aggregation time.

[0061] In some cases, the rotation mechanism may be designed to allow for reversing the direction of rotation. This feature may be useful for breaking up any unwanted settling or compaction of algal biomass that may occur during extended operation periods.

[0062] The rotation mechanism may be constructed using materials resistant to corrosion and compatible with the algal cultivation environment. In some cases, stainless steel components may be used for parts in contact with the algal suspension, while other components may be made from durable plastics or coated metals.16130761.00573 / 157562042v.1

[0063] To minimize vibration and ensure smooth operation, the rotation mechanism may include balancing features and vibration dampeners. These elements may help maintain the integrity of the algal aggregates and prevent unwanted turbulence within the cylindrical vessel.

[0064] In some cases, the rotation mechanism may be designed for easy maintenance and cleaning. This may include features such as quick-release couplings for the drive shaft or easily accessible lubrication points for bearings and gears.

[0065] The rotation mechanism may also be scalable to accommodate different sizes of cylindrical vessels. In some cases, modular designs may be employed to allow for easy adaptation to various harvesting capacities, from laboratory-scale systems to large industrial installations.

[0066] The rotational fluid dynamics system for microalgae harvesting may include a harvesting mechanism to facilitate the collection of aggregated algal biomass. This harvesting mechanism may be designed to efficiently extract the concentrated algal suspension from the cylindrical vessel while minimizing disruption to the formed aggregates.

[0067] The mixing apparatus 300 or rotation mechanism is configured to rotate the cylindrical vessel around its longitudinal axis at a speed sufficient to induce clumping (here termed aggregation) of the microalgae through fluid dynamics. The slow rotation of the vessel induces rotation in the fluid, which enhances microalgae contact with one another through slight differences in their sedimentation velocities and motion in the vessel, where they then aggregate together due to their inherent stickiness. Once aggregated, the large clumps of algae sediment quickly to the vessel bottom where the biomass can then be harvested separately from the bulk medium. The system further includes a harvesting mechanism configured to remove aggregated microalgae from the cylindrical vessel. In some cases, the vessel rotation can be varied in both17130761.00573 / 157562042v.1rotation speed and direction (reverse rotation) to induce transient laminar and / or turbulent boundary layers to form along the outer walls. This can be done to induce fragmentation of the algae aggregates near the wall in order to control their size.

[0068] According to other aspects of the present disclosure, the system may include one or more of the following features. The rotation mechanism may be configured to rotate the cylindrical vessel at an average speed between 1 and 10 rotations per minute and may include non-constant rotational rates. The cylindrical vessel may have a volume between 100 liters and 10,000 liters.

[0069] Incline Mechanism 400

[0070] As shown in FIGS. IB, 2, a tilt or incline mechanism 400 is coupled with the support apparatus 200 to incline or tilt the tank assembly 100, for example in the longitudinal direction. For example, one end of the support assembly 200 can be raised with respect to the opposite end of the support assembly 200. Here, the front leg members 230 are shorter than the rear leg members 230, so that the tank assembly tilts or inclines, here shown as a downward incline from the first rear end portion 113 to the second front end portion 115. And the conical end cap 154a is placed at the front end portion 113 of the tank assembly 100, with the output valve 162 shown at the lowest position on the tank assembly 100. The solution flows from the inlet valve 160 downward inside the tank body 110 toward the conical funnel 154a. Medium to be recycled goes through the outlet valve 162, and harvested biomass exits through a biomass outlet 164 positioned at the nose or tip of the funnel cap 154a, as will be discussed more fully below with respect to FIG. 9. The biomass valve 164 can swivel, so that the inlet valve 160 and outlet valve 164 stay fixed in position with respect to any tube connected to those respective valves 160, 164.18130761.00573 / 157562042v.1The tilt angle can be dynamically adjusted by raising and lowering the rear legs and / or the front legs.

[0071] FIG. 2 shows another configuration of the tilt assembly 400 for use with the harvesting system 10. Here, a platform 402 is pivotally coupled to the support assembly 200, and the tank body 110 is fixedly coupled to the platform 402. The platform 402 can have planar platform longitudinal members 404 and platform cross-support members 406 that contact the tank body 110 and can have the ball bearings 308. The motor 302 is also fixedly coupled to the platform 406, so that the motor rotates with the tank body 110 and the motor 302 and belt remain operatively coupled to the tank body 110 during tilt rotation. For example, the center post 242a is coupled to the platform 402 (e.g., a platform longitudinal member 402 or a platform crosssupport 406 at a middle of the platform 402), and is independent from (i.e., not directly coupled to) the support frame assembly 200 (including the top support members 210, top cross-support members 220, and legs 230).

[0072] A lift arm 408 is coupled to the frame assembly 200 (for example, one or more of the longitudinal member 210) and the platform 406. As shown, the lift arm 408 is toward or at the rear end portion of the platform 402 and the rear end portion of the tank body 110 when situated on the platform 402. The lift arm 408 can extend and retract to raise and lower the platform 400 (with the tank assembly 100 and the mixing assembly 300) with respect to the frame assembly 200. Thus, the tank can be tilted at any angle from 0 to 90 degrees to allow for different functions such as filling, emptying and / or harvesting aggregated algae. For example, the incline can be dynamically adjusted during each of those operations, whereby the tank body 110 can be at a first incline during a first (e.g., fill) operation, a second incline during a second (e.g., emptying) operation, and a third incline during a third (e.g., harvesting) operation. Each incline19130761.00573 / 157562042v.1can be different than the prior one, or can be the same as the prior one, and each operation can have more than one incline.

[0073] The inclination of the tank establishes a preferential direction for gravitational settling of aggregated microalgal clusters. As aggregation progresses, the effective density and size of the clusters increase, promoting their separation from the surrounding fluid. Under tilted conditions, these heavier aggregates precipitate toward the lower region of the tank and, due to gravity, undergo a controlled downward migration along the inclined surface. This motion results in the progressive concentration of biomass within a confined collection zone. The combined effect of shear-induced aggregation and gravity-driven transport enables spatial segregation of the biomass from the bulk suspension. This concentration mechanism significantly facilitates downstream extraction and harvesting operations by reducing the volume to be processed and improving collection efficiency, without the need for additional mechanical or chemical separation steps.

[0074] The system might be tilted to an angle up to 90° to facilitate the extraction process of harvested algae. The desirable incline can vary depending on the application to be made, including which cap is used, and the material contents. For example all the caps can be used with an incline of 0-25°, whereas the conical cap can be used up to 90°. In addition, the valves 160, 162, 164 are shown in FIG. 1 at certain positions for lower inclines; though it will be recognized that the location and position of one or more of the valves can be changed for greater inclines. For example, a biomass outlet valve 164 and / or the recycled outlet valve 162 can be positioned at the middle or toward the rear end portion 113. The system may be configured to operate without the addition of chemical flocculants to the microalgae suspension, which are detrimental to the quality of the bioproducts. The cylindrical vessel may be made of a transparent or20130761.00573 / 157562042v.1translucent material to allow light penetration and be used for cultivation purposes and / or harvesting in continuous. The system may further optionally include a light source positioned to illuminate the interior of the cylindrical vessel and air supplementation system, depending on the application such as cultivation. The rotation mechanism may be configured to induce differential sedimentation and low-shear laminar or turbulent flow within the microalgae suspension.

[0075] Single Funnel Cap 150b (FIG. 3)

[0076] FIGS. 3 A, 3B show one of the geometries for a single funnel end cap 150b, which can be used, for example, for the second end cap 154 of FIGS. 1A, IB, 2. The cap 150b has a wide head 174, and a smaller neck 176. The head 174 is linear and the neck is inset from the outer perimeter edge of the head 174 to form a flange 175 thereabout. The neck 176 forms a linear wall that extends orthogonally outward from the head inner surface. The neck has a neck inner surface 177 with a neck inner diameter. An O-ring channel or recess 173 is axially formed in the neck inner surface 177, and an O-ring 172 is positioned in the O-ring channel 172.

[0077] As shown, the valve 156 is formed at the bottom (in the embodiment of FIG. 3B) of the cap 150b just inside the head 174 and at the inner end of the neck 176. This geometry is a round circle with a single funnel region 170 used to concentrate the aggregated algae. The O-ring 172 allows dynamic sealing, enabling the cap to be independent from the tank and be steady without any rotation. This allows a region 170 without any fluid flow (or a diminished flow with respect to the main tank 110) where the aggregates algae can concentrate before being harvested from the exit of the funnel.

[0078] That is, the cap 150b rotates with respect to the tank body 110, so that the cap 150b remains at a fixed position relative to the support structure 200 and ground, with the valve 15621130761.00573 / 157562042v.1staying fixed at the bottom of the cap 150b. In some embodiments, a fastening mechanism, such as a fastener, adapter or structural support, can fixedly couple the cap 150b to the frame assembly 200, such as the top support 210, legs 230, or to the incline mechanism 400, such as the platform 404. In addition, the cap head 174 can have a flange 175 with a through hole that receives the fastening mechanism. In other embodiments, the cap 150b can be weighted so that the cap 150b rotates with respect to the tank body 110. The tank is not under pressure, so the cap 150b can be loosely coupled to the main tank 110.

[0079] In the example embodiment shown, the tank body end portion 115 outer diameter is smaller than the neck 176 inner diameter, and so the tank body end portion 115 is received into the neck 176, and sealed by the O-ring 172. The O-ring 172 is partially received in a shallow recess 173, which keeps the O-ring 172 fixed to the neck 176 and cap 150b. The O-ring 172 projects out of the recess and extends beyond the neck inner surface 177. Thus, the O-ring 172 has a smaller diameter than the neck inner surface 177, so that the O-ring 172 contacts the tank outer surface 101. The cap inner surface 177 can form a loose fit with the tank outer surface 101, so that the cap inner surface 177 does not restrict movement of the cap 150b with respect to the tank 110. The O-ring 172 can be flexible but sufficiently rigid to form a friction fit with the tank outer surface 101 so that the cap 150a does not inadvertently decouple from the tank body 110. A lubricant can be provided about the O-ring 172 and / or tank outer surface 101 to further facilitate the O-ring sliding with respect to the tank outer surface 101.

[0080] The front distal edge 117 of the main tank body 110 extends slightly past the O-ring 172 and to the funnel 170, but does not extend to the cap head 174 inner surface and does not extend to, cover or enter the funnel 170. In some embodiments, a stop member can be positioned to prevent the tank 110 from extending too far into the cap neck 176. For example, the stop member22130761.00573 / 157562042v.1can be coupled to the cap head inner surface, or to the top of the neck inner surface 177, and contact the tank distal edge 117 as the tank front end portion 115 is received into the cap neck 176. Accordingly, solution from the interior space of the tank 110 is received at the funnel 170, and exits through the valve 156.

[0081] Double Funnel Cap 150c (FIG. 4)

[0082] FIGS. 4A, 4B show another example of a double funnel cap 150c for the rotating tank. This cap is similar to the one shown in FIGS. 3A, 3B but has two funnel regions 170a, 17b, and facilitate filling and harvesting process for automated systems. The material will go out from the two cylindrical barbed connectors on top and bottom of the cap. From the top we feed new culture, from the bottom we extract the aggregated algae first, then we extract the leftover exhaust water.

[0083] In addition, flanges or stoppers 171 are provided that project inwardly in the cap to support the tank body outer surface 101 and provide clearance between the cylinder outer surface 101 and the cap 150c, allowing aggregates to pass through. The stoppers 171 align the tank distal edge 117 with the funnel 170 so that the tank distal edge 117 does not block or cover the funnel 170.

[0084] Toroidal Cap 150d (FIG. 5)

[0085] FIGS. 5 A, 5B show another example geometry for the system 10 having a circular cap 150d with a toroidal concentration region 180. The cap is 150d axial symmetrical, thus allowing minimum flow disturbance when rotating together with the main body of the rolling tank. It can be equipped with outlet / inlet fitting for ease of insertion / removal of fluid and biomass. The cap23130761.00573 / 157562042v.1150d is similar to cap 150b (FIG. 3), but here the neck 176 has a curved section that gently drives the aggregated algae into the concentrating or collecting region 180. Any suitable outlet can be provided, such as the single funnel of FIG. 3 or the double funnel of FIG. 4.

[0086] Funnel Cap 150e (FIG. 6)

[0087] FIGS. 6A, 6B, 6C show a funnel style cap 150e allowing to concentrate all the aggregated algae to the tip of the funnel. Similar to the geometry in FIG. 5, it shows an axial symmetry allowing for rotation without significant perturbation of the flow. This geometry can be combined with the tilt mechanism represented in FIG. 2 for best optimization. In certain embodiments, the rotating cylindrical tank is equipped with a funnel end cap 150e configured to define a localized collection region 198.

[0088] The cap 150e has a cap body 190 that includes a funnel-shaped head portion 192 and a cap neck 194. The funnel head portion 192 has a narrow funnel distal end and a wide funnel proximal end. The funnel head portion 192 has linear walls that are tapered inwardly from the wide proximal end to the narrow distal end. A nozzle or valve 196 is located at the funnel distal end. The neck is linear and similar to the neck of FIG. 3. The collection region 198 is located at the funnel proximal end, where the funnel proximal end meets the cap neck.

[0089] When the cylinder is operated under a slight inclination, gravitational forces act in conjunction with the tank geometry to direct aggregated microalgal clusters toward this lowest point 182. Shear-induced aggregation increases the effective size and density of the biomass, enabling gravitational settling. The imposed inclination causes the aggregated clusters to migrate axially along the cylinder toward the lower end, while the toroidal-shaped geometry further guides and funnels the biomass into the apex of the end cap 150e. This combined effect results in24130761.00573 / 157562042v.1passive trapping and concentration of the aggregates within the toroidal-shaped region, where local flow velocities are reduced and re-entrainment is minimized. The geometry thereby promotes accumulation of biomass in a confined volume, enhancing concentration efficiency. The toroidal-shaped end cap thus acts as a passive collection and retention feature, enabling continuous or batch extraction of the concentrated biomass from a well-defined location. This configuration improves harvesting efficiency, reduces the need for external separation mechanisms, and maintains a chemical-free processing environment suitable for high-value applications.

[0090] V-shape Cap 150f (FIG. 7)

[0091] FIGS. 7A, 7B, 7C show a funnel style cap 150f similar to the one in FIG. 5, but with a V-shape profile instead of toroidal shape. The function of this geometry is analogous to the one represented in FIG. 5 and is optimized for different algae species and rotating regimes. Here, a linear angled wall 179 is positioned between the cap neck 176 and the cap head 174, so that the cap 150f is tapered outward from the neck 176 to the head 174 to define a reverse funnel shape with a collection region 181. The head 174 is substantially larger than the neck 176. FIG. 7 works with exactly the same principle as in FIG. 5, but with a different geometry but with the same scope and performance.

[0092] Operation (FIG. 9)

[0093] FIGS. 9A-9E shows an example operation of the harvesting system 10, having various operational phases: (1) tank inclination (FIG. 9A); (2) tank filling (FIG. 9B); (3) aggregation (FIG. 9C); (4) water extraction (FIG. 9D); and material extraction (FIG. 9E). This example25130761.00573 / 157562042v.1shows the double funnel cap 150c (FIG. 4) to extract algae, though other caps and materials can be utilized, and operational phases can be added or removed. Accordingly, there are four valves, including a rear end upper valve 151a, rear end lower valve 153 a, front end upper valve 151b, and front end lower valve 153b. The upper valves 151a, 151b are positioned at the furthest position further from the ground and can be directed away from the ground (or in another direction). And the lower valves 153a, 153b are positioned at the lowest position, closer to the ground than the upper valves 151a, 151b, and can be directed toward the ground (or in another direction).

[0094] Turning to FIG. 9A, the first phase is tank inclination. Here, the tank body 110 is inclined through use of the incline mechanism 400 to be set at the desired operational angle. The tank body 110 is positioned on the platform cross-support members 406 of the platform 402, and the lift arm 408 is operated to raise the distal rear end of the platform 402 and rear end portion 113 of the tank body 110. The tank body 110 is longer than the platform 402, so that the rear distal edge 111 and front distal edge 117 extend beyond the platform 402 and overhang the platform 402. In this manner, the platform 402 does not interfere or obstruct the caps 105c that are wider than and fitted to the main body 110 distal edges 111, 117 or the tubes / components fitted to those end caps 105c. The end caps 105c are fixedly coupled to the platform 402 or support structure 200, so the caps 105c do not rotate as the main tank body 110 rotates. Inclining the tank 110 prior to it being filled facilitate air escaping the tank through the rear upper valve 151a.

[0095] Turning to FIG. 9B, the second phase is filling or loading the interior cavity of the tank body 110. Here, the bottom valves 153a, 153b are closed, and the upper valves 151a, 151b are open. The algal suspension (i.e., algae cells suspended in a liquid such as water) is fed into the tank trough the upper back valve 151a. The upper back valve 151a can be in flow26130761.00573 / 157562042v.1communication with a material source, such as a large container that is placed at a higher position the upper back valve 151a to provide a gravity feed to the upper back valve 151a.

[0096] The front upper valve 151b is kept open to allow air to escape, facilitating liquid loading. The lower valves 153a, 153b are closed to prevent water and algae from escaping. The tank 110 is loaded to completely fill the interior space of the tank 110 (as shown in FIG. 9C), though FIG.9B shows the tank partially filled as it is in the process of being completely filled. In other embodiments, the tank 110 need not be completely filled, but can be partially filed, such as to about two-thirds capacity, though can be more or less depending on the application. Once the solution is loaded, the upper valves 151a, 151b are closed. Though the tank is shown being loaded in the inclined position, it will be appreciated that the tank can be loaded prior to being inclined or during incline.

[0097] In FIG. 9C, the aggregation phase is shown. Here, the tank is agitated, such as by rolling or rotating the tank body 110 in the inclined position, through use of the rotation mechanism 300. As illustrated, as the aggregates form, they become heavier and tend to sink in the liquid and precipitate towards the lower funnel, at the cap biomass collection zone 170 of the lower end cap 153b. Once in that space, Algal aggregates are trapped and consequently concentrated. Since the end cap 153b remains fixed, the algae can settle at the collection zone 170 even while the main tank 110 is rotating.

[0098] The next phase is product recovery, which includes a liquid (e.g., clarified medium) extraction phase (FIG. 9D) and medium (e.g., algal) extraction (FIG. 9E). At FIG. 9D, the tank 110 is lowered, for instance to a completely horizontal position. The lift arm 408 is lowered, which lowers the rear end of the platform and tank body 110. After that, the rear upper and lower valves 151a, 153a are opened. The clarified (cell free) medium is recovered from the lower front27130761.00573 / 157562042v.1valve 153b, while air fills the tank through the upper valve 151b (and / or rear upper valve 151a) without liquid disturbance. It is further noted that the tank rotation can optionally be stopped or slowed during this produce recovery phase (FIG. 9D and / or 9E).

[0099] Turning to FIG. 9E, once the liquid is removed from the tank, the front lower valve 153b is opened to recover concentrated biomass. If the operator needs to collect partial concentrated biomass before the medium is completely clarified, it is possible to do so with an alternative method. For example, in phase 4 (FIG. 9D), the lower and upper front valves 151b, 153b (on the side where the biomass is) can be quickly opened (and closed) to recover concentrated biomass, leaving the liquid in the tank. It is further noted that the biomass can be retrieved while the tank is at the inclined position (FIG. 9C), or is lowered to a slightly raised position (e.g., 0.5-2° or 5°) to prevent any backflow of aggregated medium

[0100] Summarizing the operational phases, an algal suspension of variable concentration (0.2 to 5 g / L) is fed into the rotating tank harvester. After inducing aggregation and liquid separation the tank will generate a double output: 1. Clarified medium, which is in cell-free (<0.1 g / L, efficiency can vary) growing solution or treated water and 2. Concentrated biomass (2 to 200 g / L). However, it will be appreciated that the operational phases can be changed, eliminated or switched. For example, the tank can be inclined after it is loaded with algal suspension. In addition, the tank need not be rotated. Still further, the system 10 can have a continuous operation where all the valves 151a, 151b, 153a, 153b are at least partly opened. Thus, the tank can be continuously filled through the upper rear valve 151a, while liquid is continuously drained through lower rear valve 153a. The rear bottom valve 153a can be slightly opened during rotation and / or filling, and the algae can be periodically or continuously removed through the front lower valve 153b, with air / pressure release through the front upper valve 151b.28130761.00573 / 157562042v.1A uniform level can be maintained to avoid over-filling the tank. In addition, the front end cap can have a single valve 153b (such as the end caps shown in FIGS. 3, 6), and an air vent or valve can be provided at another location on or in communication with the tank.

[0101] According to another aspect of the present disclosure, a method for harvesting microalgae is provided. The method includes introducing a suspension of microalgae into a cylindrical vessel having a longitudinal axis oriented predominantly perpendicular to gravity. The method also includes rotating the cylindrical vessel around its longitudinal axis at a speed sufficient to induce aggregation of the microalgae through fluid dynamics. The method further includes methods to remove the aggregated biomass from the cylindrical vessel.

[0102] According to other aspects of the present disclosure, the method may include one or more of the following features. The method may further include collecting aggregated microalgae in a conical end portion attached to one end of the cylindrical vessel. The removing step may involve opening one or more valves located at the conical end portion to extract aggregated microalgae, or further tilting the tank, such as up to a standing position (longitudinal axis orthogonal to horizontal) which might depend on the size and content of the tank. The method may be performed without adding chemical flocculants to the microalgae suspension. The method may further include illuminating the interior of the cylindrical vessel during the rotating step. The rotating step may induce differential sedimentation and low-shear laminar flow within the microalgae suspension.

[0103] The method may further include recycling the remaining liquid medium after removing the aggregated microalgae. The method might be employed for an innovative continuous “cultivation and harvesting” method. The rotatory movement allows aggregation of a portion of the suspended cells. The aggregates precipitate by gravity and are collected in29130761.00573 / 157562042v.1proximity of the harvesting output. Non aggregating cells can be kept in suspension and continue dividing as long as light and air are provided. Once the suspended biomass concentration rise again, aggregation rate will increase again resulting in a continuous production of biomass and harvesting. The volume subtracted for harvesting can be replaced always in continuous with fresh, nutrient reach medium from the inlet valve.

[0104] The innovative methodology to harvest algae using aggregation driven by controlled fluid-dynamics conditions. The technology works by slowly rotating a cylindrical vessel and the algal suspension inside it around its longitudinal axis, which is oriented perpendicular to gravity as shown in FIG. 1. This motion induces differential sedimentation, low-shear laminar flow, and in some cases, gentle turbulent flow to induce algal aggregation through enhanced cell-to-cell contact and the inherent adhesiveness of their extracellular polymeric substances (EPS). A conical end outfitted with valves is used to facilitate biomass harvest. This technology outperforms the current state-of-the-art by quickly and gently generating aggregating biomass with high sinking rates using minimal energetic inputs and without need for flocculant agents. This has the potential to overcome the technological limitations related to present harvesting methods and is also suitable for bio-refinery of multiple high-value compounds, which will lead to the cost-effective production of biofuels.

[0105] Other Features

[0106] In some cases, the harvesting mechanism may comprise a conical end portion attached to or integrally formed with the cylindrical vessel. This conical end portion may be oriented at the bottom of the vessel when it is positioned for harvesting. The conical shape may30130761.00573 / 157562042v.1help funnel the aggregated algal biomass towards a central collection point, enhancing the efficiency of the harvesting process.

[0107] The conical end portion may be constructed from materials compatible with the algal suspension and resistant to corrosion. In some cases, stainless steel or food-grade plastics may be used to ensure durability and maintain the quality of the harvested biomass.

[0108] The harvesting mechanism may include a valve system integrated into the conical end portion. This valve system may allow for controlled extraction of the concentrated algal suspension. In some cases, a single valve may be sufficient for small-scale operations. For larger systems, multiple valves may be incorporated to provide greater control over the harvesting process.

[0109] Various valve configurations may be employed in the harvesting mechanism. In some cases, a simple ball valve may be used, allowing for quick opening and closing during the harvesting process. Alternatively, a butterfly valve may be employed, offering precise flow control and the ability to modulate the extraction rate.

[0110] For more advanced systems, a diaphragm valve may be incorporated into the harvesting mechanism. Diaphragm valves may provide excellent sealing capabilities and minimize the risk of contamination, which may be particularly important for applications in the food or pharmaceutical industries.

[0111] In some cases, the valve system may include a series of valves arranged in a manifold configuration. This arrangement may allow for selective harvesting from different regions of the conical end portion, potentially optimizing the collection of aggregated biomass.

[0112] The effectiveness of the harvesting mechanism in collecting aggregated microalgae may depend on various factors, including the valve configuration, the slope of the31130761.00573 / 157562042v.1conical end portion, and the properties of the algal aggregates. In some cases, the system may be capable of achieving a recovery rate of 75%. This recovery rate may represent a significant improvement over conventional harvesting methods, particularly when combined with the energy efficiency of the rotational fluid dynamics system.

[0113] The harvesting mechanism may be designed to handle algal suspensions with varying concentrations of biomass. In some cases, the average concentration of biomass in the harvested suspension may be 2.5 g / L. This concentration may represent a substantial increase compared to the initial algal culture, facilitating downstream processing and reducing the overall energy requirements for further dewatering steps.

[0114] To enhance the effectiveness of the harvesting mechanism, the conical end portion may be equipped with internal baffles or flow directors. These structures may help guide the aggregated biomass towards the valve system, potentially improving the recovery rate and consistency of the harvested product.

[0115] In some cases, the harvesting mechanism may include a flushing system to prevent clogging and ensure consistent performance. This flushing system may use a small volume of recycled growth medium or clean water to clear any residual biomass from the conical end portion and valve system after each harvesting cycle.

[0116] The harvesting mechanism may also incorporate sensors to monitor the extraction process. These sensors may measure parameters such as flow rate, biomass concentration, or valve position, providing real-time data to optimize the harvesting operation. In some cases, this data may be integrated with a control system to automate the harvesting process, potentially improving efficiency and consistency.32130761.00573 / 157562042v.1

[0117] For larger-scale operations, the harvesting mechanism may be designed with redundancy in mind. Multiple valve systems or backup components may be incorporated to ensure continuous operation even in the event of individual component failures.

[0118] The harvesting mechanism may be constructed to allow for easy cleaning and maintenance. In some cases, the conical end portion and valve system may be designed for quick disassembly, facilitating regular inspection and cleaning to maintain optimal performance and prevent contamination between harvesting cycles.

[0119] The rotational fluid dynamics system for microalgae harvesting may include optional components to enhance its efficiency and versatility. These optional components may be integrated into the system to optimize performance, monitor process parameters, or expand the system's capabilities.

[0120] In some cases, the rotational fluid dynamics system may incorporate a light source. The light source may be used to promote photosynthesis and maintain algal growth during the harvesting process. Various types of light sources may be employed, such as LED arrays, fluorescent tubes, or fiber optic systems. The light source may be positioned externally to illuminate the cylindrical vessel or integrated within the vessel itself.

[0121] The light source may be designed to provide specific wavelengths of light that are optimal for algal growth. In some cases, the light source may be programmable to adjust its intensity and spectral output based on the needs of different algal species or growth stages. This adaptability may allow the system to maintain algal viability and potentially continue biomass production during the harvesting process. The rotating system can be used as cultivation vessel as well. In this case it will be equipped with a cultivation light source that can be either internal33130761.00573 / 157562042v.1or external to the vessel. In cultivation mode valves can also be used to supply air or concentrated CO2.

[0122] To accommodate the light source, portions of the cylindrical vessel may be constructed from transparent or translucent materials. In some cases, the entire vessel 110 may be made from transparent materials such as glass or acrylic. Alternatively, transparent viewing ports or sections may be incorporated into an otherwise opaque vessel 110. These transparent elements may allow for visual monitoring of the aggregation process and enable the use of external light sources.

[0123] The use of transparent materials may also facilitate the integration of optical sensors or imaging systems. In some cases, these sensors may be used to monitor algal concentration, aggregate size, or other parameters in real-time. This information may be used to optimize the harvesting process or trigger automated adjustments to system parameters.

[0124] In some cases, the rotational fluid dynamics system may include a temperature control mechanism (e.g., a controller such as a processing device, temperature sensor, heating unit and / or cooling unit). This mechanism may help maintain optimal conditions for algal aggregation and prevent thermal stress during the harvesting process. The temperature control system may incorporate heating or cooling elements, such as water jackets or internal coils, to regulate the temperature of the algal suspension.

[0125] The system may also include optional mixing or agitation components such as interior baffles, paddles, static mixers, or gas sparging systems. In some cases, these components may be used to create gentle turbulence or enhance fluid circulation within the cylindrical vessel. These components may be designed to operate in harmony with the rotational motion of the vessel, potentially improving the efficiency of cell-to-cell contact and aggregate formation.34130761.00573 / 157562042v.1

[0126] Optional sensors and monitoring equipment may be integrated into the rotational fluid dynamics system. These may include optical particle sizing or turbidity sensors, pH sensors, dissolved oxygen meters, conductivity probes, or nutrient analyzers. In some cases, these sensors may provide valuable data on the condition of the algal suspension during the harvesting process, allowing for real-time adjustments to optimize performance.

[0127] In some cases, the system may include optional sterilization or sanitation components. These may include UV light systems, chemical dosing equipment, or steam injection ports. Such components may help maintain the cleanliness of the system and prevent contamination between harvesting cycles, which may be particularly important for applications in food or pharmaceutical industries.

[0128] The rotational fluid dynamics system may also be equipped with optional automation and control systems. These systems may include programmable logic controllers (PLCs), human-machine interfaces (HMis), or data logging equipment. In some cases, these components may allow for automated operation of the harvesting process, remote monitoring, or integration with broader algal cultivation systems.

[0129] Optional safety features may also be incorporated into the rotational fluid dynamics system. These may include emergency stop buttons, pressure relief valves, or containment systems to prevent spills or leaks. In some cases, these safety features may be designed to comply with specific industry standards or regulatory requirements.

[0130] The integration of these optional components may enhance the functionality and adaptability of the rotational fluid dynamics system for microalgae harvesting. By incorporating various combinations of these elements, the system may be tailored to meet the specific needs of different algal species, cultivation methods, or end-use applications.35130761.00573 / 157562042v.1

[0131] The rotational fluid dynamics system for microalgae harvesting may operate through the coordinated interaction of its various components to achieve efficient aggregation and collection of algal biomass. The system's operation may involve a series of steps that leverage controlled fluid dynamics to promote cell-to-cell contact and aggregate formation.

[0132] In some cases, the harvesting process may begin with the introduction of an algal suspension into the cylindrical vessel. The algal suspension may contain dispersed microalgal cells with sizes typically less than 50 pm. Once the vessel is filled to an appropriate level, the rotation mechanism may be activated to initiate the slow rotation of the cylindrical vessel around its longitudinal axis.

[0133] The rotational motion of the vessel may induce specific fluid dynamic conditions within the algal suspension. These conditions may include differential sedimentation, low-shear laminar flow, and in some cases, gentle turbulent flow. The combination of these fluid dynamic effects may enhance cell-to-cell contact and promote the formation of algal aggregates.

[0134] As the vessel rotates, the algal cells may experience slight differences in motion due to variations in cell size, density, or other physical properties. These differences may increase the likelihood of collisions between cells, potentially leading to the formation of small clusters. The inherent adhesiveness of the algal cells' extracellular polymeric substances (EPS) may facilitate the binding of these clusters, allowing them to grow into larger aggregates.

[0135] The slow rotational speed of the vessel may be crucial for maintaining gentle conditions that promote aggregation without causing cell damage. In some cases, a rotational speed of approximately 3 rpm may be used, though this may be adjusted based on the specific characteristics of the algal species being harvested.36130761.00573 / 157562042v.1

[0136] As the aggregation process continues, the system may dramatically increase the sedimentation rates of the algal biomass. In some cases, the sedimentation rates may be increased by up to three orders of magnitude compared to the initial dispersed state of the algal cells. This significant increase in sedimentation rate may be attributed to the formation of larger aggregates, which have a higher settling velocity than individual cells.

[0137] The duration of the aggregation process may vary depending on factors such as algal species, initial cell concentration, and desired aggregate size. In some cases, the system may be capable of aggregating dispersed microalgal cells into floes larger than 1 cm within a period of 3-4 hours. This rapid aggregation may represent a significant improvement over conventional harvesting methods, potentially reducing overall processing time and energy requirements.

[0138] During operation, the system may allow for real-time monitoring and adjustment of process parameters. In some cases, sensors integrated into the cylindrical vessel may provide data on factors such as aggregate size, biomass concentration, or fluid dynamics. This information may be used to optimize the rotational speed or duration of the aggregation process for different algal species or cultivation conditions.

[0139] Once the desired level of aggregation has been achieved, the harvesting mechanism may be activated to collect the concentrated algal biomass. The conical end portion of the vessel may facilitate the movement of the aggregated biomass towards the valve system. In some cases, the rotation of the vessel may be slowed or stopped to allow the aggregates to settle towards the bottom of the vessel before harvesting.

[0140] The valve system in the harvesting mechanism may be opened to allow the concentrated algal suspension to flow out of the vessel. The flow rate may be controlled to37130761.00573 / 157562042v.1ensure efficient collection of the aggregated biomass while minimizing disruption to the formed floes. In some cases, multiple harvesting cycles may be performed to maximize the recovery of biomass from a single batch.

[0141] The system's operation may be adaptable to various microalgae species with different physical and biological characteristics. For example, when harvesting species with lower natural adhesiveness, the rotational speed or duration may be adjusted to promote more frequent cell-to-cell contacts. Conversely, for species that aggregate more readily, the process may be optimized for shorter durations or lower rotational speeds to achieve the desired level of aggregation.

[0142] In some cases, the system may be operated in a semi-continuous mode, where a portion of the aggregated biomass is harvested while new algal suspension is introduced to maintain a constant volume in the vessel. This mode of operation may allow for more efficient use of the system, potentially increasing overall throughput.

[0143] The rotational fluid dynamics system may also be integrated with upstream cultivation processes and downstream processing steps. For example, the system may be designed to receive algal suspensions directly from photobioreactors or open pond systems. Similarly, the harvested biomass may be fed directly into further concentration or extraction processes, creating a more streamlined and efficient production pipeline.

[0144] By leveraging the controlled fluid dynamics and the natural properties of microalgal cells, the rotational fluid dynamics system may provide an efficient and gentle method for harvesting microalgae. The system's ability to rapidly form large aggregates and significantly increase sedimentation rates may offer substantial advantages in terms of energy efficiency, processing time, and biomass recovery compared to conventional harvesting methods.38130761.00573 / 157562042v.1

[0145] A number of implementations have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the disclosure. Accordingly, other implementations are within the scope of the following claims.

[0146] For example, the system can utilize any suitable end cap size and shape. And the end cap can rotate with respect to the main tank body 110 in any suitable manner other than through the friction fit of the O-ring. For example, the end cap can be fixedly coupled with the tank body 110, such as by providing the neck with a first mating feature (e.g., an internal threading) and the tank outer surface with second mating feature (e.g., an external threading). In this embodiment, the end cap rotates as the tank body rotates, but the valve 162 stays at a fixed lower position. Or, the valve 162 can also be fixed to the cap and main tank body, but have a outlet port that enables draining at all rotational positions. In addition, rotating valves can be placed at different positions along the tank 110. The system 10 can operate at room temperature.

[0147] In addition, one or more of the caps and valves can be fixed to the tank 110 (such as by threadably coupling or by integral forming or by providing the cylinder with a closed end), and the operations performed when the tank is in the proper position. For example, the loading and product extraction can be performed by stopping rotation of the tank when the valves 151a, 151b, 153a, 153b are in the upper and lower positions. Any necessary tubes or adapters can then be connected, and then removed when the tank needs to be rotated.

[0148] FIG. 8 shows algal culture before aggregation process (left) and after 3h low speed rolling (right). Results show that simple slow tank rotation about a horizontal axis can aggregate dispersed microalgal cells (<50 pm) into flocs >1 cm within 3-4 hours, dramatically increasing their sedimentation rates by three orders of magnitude. As an example of the39130761.00573 / 157562042v.1commercial feasibility of this method, a 1000 L tank operating for 3 hours at a rotational speed of 3 rpm, with an estimated recovery rate of 75% and an average concentration of biomass of 2.5 g / L would lead to 1.875 kg of harvested biomass. Our calculations estimate that the energy consumption would be approximately 2500 J, or 1.3 kJ / kg of biomass, approximately three orders of magnitude lower than centrifugation-based methods (1.1 MJ / kg). This remarkable efficiency is attributed to the low and constant rotational speed, which efficiently induces selfflocculation through slight differences in cell motion.

[0149] The microalgae harvesting system 10 relies on low-energy physical biomass flocculation but avoids the use of additives, contamination, and cell damage, representing a solution compatible with a synergistic co-production of nutraceuticals. This comprehensive utilization aligns with circular economy principles, making the technology a cornerstone for advancing algae-based solutions in the global energy and bioproduct markets while significantly reducing the environmental footprint. Moreover, the absence of additives allows the recycling of the growth medium, reduces resource consumption and does not affect product quality. The facility is 100% reusable and scalable and it does not require consumables or regular equipment replacements (e.g. filters), ensuring an environmentally friendly approach for long-term use. The straightforward scalability for mid- to large-scale operations, whether through the expansion of a single structure or the integration of modular units, makes it adaptable to evolving production needs. The proposed approach can also be adapted to virtually any microalgal species and is agnostic to cultivation setups, from open ponds to closed bioreactors.

[0150] While our system offers many advantages, it also has some limitations. It achieves an estimated 75% recovery rate, which is lower than the 90% from centrifugation-but at a much lower cost. However, in our bench-scale prototype, aggregation rates increase exponentially with40130761.00573 / 157562042v.1suspended cell concentrations, meaning a minimum cell density is needed for timely aggregate formation. Typically, cell concentration ranges from 106-108 and 105-106 cells / ml in bioreactors and open ponds respectively. Our tests indicate a minimal operational concentration of 103 cells / ml, a threshold that is readily achievable in both cultivation scenarios. Variations in temperature, photoperiod, and species-specific EPS productivity affect cell density and stickiness, which also affects the recovery efficiency. To cope with potential shortcomings, we can tailor the fluid flow in the aggregation tank to induce gentle laminar or turbulent shearing to further increase the aggregation efficiency. Moreover, tests show that the use of algal consortiums significantly boosts aggregation. Together, these approaches can optimize performance under varying conditions.

[0151] The following references are hereby incorporated by reference. Li, T., Hu, J., & Zhu, L. (2021). Water, 13(18), Article 18. https: / / doi.org / 10.3390 / wl3182585; National Renewable Energy Laboratory (NREL), Argonne National Laboratory (ANL), & Pacific Northwest National Laboratory (PNNL). (2024). www.nrel.gov / docs / fy24osti / 87099.pdf; Zhu, J., Wakisaka, M., Omura, T., Yang, Z., Yin, Y., & Fang, W. (2024). Journal of Cleaner Production, 436, 140626. https: / / doi.Org / 10.1016 / j.jclepro.2024.140626.

[0152] The technology advances the production of high quality biofuels and other products specifically from microalgae, which can be cultured using wastewater and saline streams on minimal land resources. The technology is agnostic to cultivation method and easily translatable and transportable to different locations. Thus, success of this effort will directly enable the expansion of biofuel production in ways that promote biofuel production around the country, avoid the use of large arable lands and freshwater resources, and lessen the overall impact and burden of the biofuel industry on communities around the country.41130761.00573 / 157562042v.1

[0153] It is further noted that the drawings may illustrate and the description and claims may use several geometric or relational terms and directional or positioning terms, such as between, planar, linear, curved, elongated, circular, parallel, perpendicular, orthogonal, transverse, lateral, circular, top, bottom, left, right, up, down, inner, outer, side, distal, and proximal. Those terms are merely for convenience to facilitate the description based on the embodiments shown in the figures, and are not intended to limit the disclosure. Thus, it should be recognized that the disclosure can be described in other ways without those geometric, relational, directional or positioning terms. In addition, the geometric or relational terms may not be exact. For instance, walls or surfaces may not be exactly flat, perpendicular or parallel to one another but still be considered to be substantially perpendicular or parallel because of, for example, roughness of surfaces, tolerances allowed in manufacturing, etc. And, other suitable geometries and relationships can be provided without departing from the spirit and scope of the disclosure.

[0154] Each of the exemplary embodiments described above may be realized separately or in combination with other exemplary embodiments. In addition, features, components or elements from one embodiment can be utilized with or in other embodiments. For example,

[0155] The foregoing description and drawings should be considered as illustrative only of the principles of the disclosure, which may be configured in a variety of shapes and sizes and is not intended to be limited by the embodiment herein described. Numerous applications of the disclosure will readily occur to those skilled in the art. Therefore, it is not desired to limit the disclosure to the specific examples disclosed or the exact construction and operation shown and described. Rather, all suitable modifications and equivalents may be resorted to, falling within the scope of the disclosure.42130761.00573 / 157562042v.1

Claims

CLAIMS:

1. A system for harvesting microalgae, comprising:a cylindrical vessel configured to contain a suspension of microalgae and having a longitudinal axis;an incline mechanism configured to incline the cylindrical vessel along its longitudinal axis;a rotation mechanism configured to rotate the inclined cylindrical vessel around its longitudinal axis at a speed sufficient to induce aggregation of the microalgae through fluid dynamics; anda harvesting mechanism configured to collect aggregated microalgae in the cylindrical vessel.

2. The system of claim 1, wherein the cylindrical vessel is elongated and the axis comprises a longitudinal axis.

3. The system of claim 1 or 2, wherein the axis is horizontal.

4. The system of any one of claims 1-3, further comprising a support frame and said rotation mechanism includes one or more rotation elements positioned perpendicular to the axis, wherein the cylindrical vessel rests on the one or more rotation elements to permit rotation of the cylindrical vessel.

5. The system of any one of claims 1-4, wherein the axis is perpendicular to gravity.

6. The system of any one of claims 1-5, wherein the axis is at an acute angle less than 25 degrees with respect to horizontal.

7. The system of any one of claims 1-6, wherein the rotation mechanism is configured to rotate the cylindrical vessel at a speed between 1 and 10 rotations per minute.43130761.00573 / 157562042v.

18. The system of any one of claims 1-7, wherein the cylindrical vessel has a volume between 10 liters and 10,000 liters.

9. The system of any one of claims 1-8, further comprising a conical end portion attached to one end of the cylindrical vessel, wherein the conical end portion is configured to facilitate collection of aggregated microalgae.

10. The system of claim 9, wherein the harvesting mechanism comprises one or more valves located at the end portion.

11. The system of any one of claims 1-10, wherein the system is configured to operate without the addition of chemical flocculants to the microalgae suspension.

12. The system of any one of claims 1-11, wherein the cylindrical vessel is made of a transparent or translucent material to allow light penetration, and further comprising a light source positioned to illuminate the interior of the cylindrical vessel.

13. The system of any one of claims 1-12, wherein said vessel has an open end, and further comprising an end cap rotatably mounted to the open end of the vessel, whereby the end cap remains stationary as said vessel is rotated by said rotation mechanism.

14. The system of claim 13, said end cap having a collection region that collects aggregated microalgae during rotation and or inclining of said vessel.

15. A method for harvesting microalgae, comprising:introducing a suspension of microalgae into a cylindrical vessel having a longitudinal axis oriented perpendicular to gravity;rotating the cylindrical vessel around its longitudinal axis at a speed sufficient to induce aggregation of the microalgae through fluid dynamics; andremoving aggregated microalgae from the cylindrical vessel.44130761.00573 / 157562042v.

116. The method of claim 15, wherein rotating the cylindrical vessel comprises rotating at a speed between 1 and 10 rotations per minute.

17. The method of claim 15 or 16, further comprising collecting aggregated microalgae in a conical end portion attached to one end of the cylindrical vessel.

18. The method of any one of claims 15-17, wherein removing aggregated microalgae comprises opening one or more valves located at the end portion to extract aggregated microalgae.

19. The method of any one of claims 15-18, wherein the method is performed without adding chemical flocculants to the microalgae suspension.

20. The method of any one of claims 15-19, further comprising illuminating the interior of the cylindrical vessel during the rotating or non rotating step.

21. The method of any one of claims 15-20, wherein rotating the cylindrical vessel induces differential sedimentation and low-shear laminar flow within the microalgae suspension.

22. A rotational fluid dynamics system for microalgae harvesting, comprising:a cylindrical vessel oriented with its longitudinal axis perpendicular to gravity;a motor coupled to the cylindrical vessel and configured to rotate the vessel at a speed between 1 and 10 rotations per minute; anda variable geometry end portion attached to one end of the cylindrical vessel, the end portion including at least one valve for extracting aggregated microalgae.

23. The rotational fluid dynamics system of claim 22, wherein the cylindrical vessel has a volume between 10 liters and 10,000 liters.

24. The rotational fluid dynamics system of claim 22 or 23, wherein the cylindrical vessel is made of a transparent or translucent material to allow light penetration.45130761.00573 / 157562042v.

125. The rotational fluid dynamics system of any one of claims 22-24, further comprising a light source positioned to illuminate the interior of the cylindrical vessel.

26. The rotational fluid dynamics system of any one of claims 22-25, wherein the motor is coupled to a gear reduction system to provide precise control of the rotational speed.

27. The rotational fluid dynamics system of any one of claims 22-26, further comprising a control system configured to adjust the rotational speed based on at least one of algal concentration, species-specific characteristics, or desired aggregation time.

28. A harvesting system comprising:a cylinder having a central axis, an open end and an interior space;an inlet valve for communicating a liquid solution suspension into the interior space, the liquid solution suspension containing a liquid and a material;a rotation apparatus configurated to rotate said cylinder about the central axis;an incline apparatus configured to incline the cylindrical vessel along its axis.an end cap rotatably coupled with said cylinder at the open end, said end cap forming or having a collection region for collecting material from the liquid solution suspension during rotation and incline of the cylinder.

29. The system of claim 28, wherein said collection region has a diminished fluid flow with respect to the cylinder.46130761.00573 / 157562042v.1

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