Patent Application
20140315290
The present invention relates to a bioreactor for production of biomass and more particularly to a low-cost, high surface-to-volume trough-like elevated pond that integrates features of photobioreactors such as transparency/translucency from all directions, closed environment, efficiency in the mixing of gases and temperature control. The configuration, fast erection, collapsibility and temperature control of the device may also apply to troughs for animal feed, to fish and shrimp culture and to fast erection of mini-greenhouses for agricultural purposes.
The current energy crisis has prompted interest in alternative energy, bringing a great deal of attention to the production of algae biofuels. Beyond biofuels, commercial algae farming is also important to medicine, food, chemicals, aquaculture and production of feedstocks. One major obstacle to the production of biofuels is the commercial scale-up for mass culture, temperature control of algae and the high cost associated with such a culture.
The vast number of different bioreactor concepts is testimony that the best algal farming bioreactors are still to be found. Most bioreactor designs are not suitable for commercial use due to cost and scale-up problems. In contrast with bioreactors, pond technologies are commercially viable today, but have well-established problems of their own. Integrated technologies might provide the control offered through closed bioreactors and the scalability afforded by open ponds.
To appreciate the value of attempts made and of associated prior art, a short review of recent studies and related publications is presented:
According to Mario R. Tredici: “Outdoors, under full sunlight, the photosynthetic efficiency drops to one tenth-one fifth of the values observed at low irradiances. The major causes for this inefficiency are the light saturation effect (LSE) and photoinhibition, phenomena that strongly limit the growth of microalgae in outdoor culture, although these because of the high cell density, are light-limited. The main problem is that photosynthetic apparatus of phototrophs saturates at low irradiances and that, at irradiances above saturation, the absorbed photons are used inefficiently and may cause cell injury. Several strategies to overcome the LSE and photoinhibition have been proposed, based on engineering (light dilution, ultra high cell density culture, high turbulence), physiologic (photoacclimation, nutrient deprivation) or genetic.” (Tredici M. R. (2004) Mass production of microalgae: photobioreactors. In Richmond A (ed.), Handbook of Microalgae Culture. Blackwell Publishing, Oxford (UK), pp 178-214.
Dimanshteyn taught in U.S. Pat. No. 7,824,904 that photobioreactors generally consist of a container containing a liquid growth medium that is exposed to a light source. However, the configuration of the photobioreactor often prevents the light from penetrating more than a few centimeters from the surface of the liquid. This problem reduces the efficiency of the photobioreactor, and was recognized in “Solar Lightning for Growth of Algae in a Photobioreactor” published by the Oak Ridge National Lab and Ohio University. Light delivery and distribution is the principle obstacle to using commercial-scale photobioreactors for algae production. In horizontal cultivator systems, light penetrates the suspension only to 5 cm leaving most of the algae in darkness.
As described in Healthy Algae, Fraunhofer Magazine, January 2002, algae are a very undemanding life form—they only need water, CO2, nutrients and sunlight. However, providing sufficient sunlight can be a problem in large scale facilities. As the algae at the surface absorb the light, it does not penetrate to a depth of more than a few millimeters. The organism inside the unit gets no light and cannot grow, explains Walter Troesch, who has been cultivating algae for years. One of the problems with growing algae in any kind of pond is that only in the top 1-4 or so of the pond receives sufficient solar radiation for the algae to grow. In effect, this means that the ability of a pond to grow algae is limited by its surface area, not by its volume.
In summary, the ability of a pond to grow algae is limited by its surface area, not by its volume. Therefore limitations in prior documents are examined in consideration of the above findings.
Traditional procedures employed for culturing autotrophic organisms have involved the use of shallow open ponds or open channels exposed to sunlight. Not surprisingly this comparatively crude method has proved impracticable for production of pure high grade products because of such problems as invasion by hostile species (sometimes producing dangerous toxins), other pollution (such as dust), difficulty in the control of such variables as nutrient ratios, temperature and pH, intrinsically low yield because of escape of carbon dioxide to the atmosphere and inefficient use of light to illuminate only the top portion of the biomass.
Somewhat more sophisticated attempts have involved the use of horizontally disposed large diameter transparent plastics tubes for biomass production. The problems of such a system include the low density of biomass in the liquid within the tubes, coating of the pipes by algae due to low velocity flow passing through, thus reducing transparency, overheating in summer weather, high land usage and high energy input to displace large amount of over diluted water.
Now, looking closely at receptacles disclosed in prior documents and more particularly for potential use as low-cost raceway-type pond or photo bioreactor, a number of inventions are examined.
U.S. Pat. No. 7,069,875 to Warecki (“Warecki”) discloses a large and low cost portable raceway or vessel for holding flowable materials. The vessel has a body formed of an elongate rollable sheet of buoyant material that, when assembled into an upwardly concave vessel has bulkheads at its ends to give it its half-rounded shape. The large vessel is self-supporting in both water and land. The Warecki vessel suffers from a number of limitations. Joining of parts such as bulkheads to the body of the vessel requires welding, chemical bonding, and- or mechanical fastening. Also, to maintain the shape of the pond, bulkhead bow frames must be positioned inside the vessel, dividing the space into closed compartments that are fastened mechanically or chemically to the body, although some unsecured movable compartments are used. Also, no provision of thermal control is provided.
WO2011016735 to Dalrymple discloses an erectable trough for animal feed. The plastic sheet disclosed by Darlymple is bent into a U-shaped trough with opposite side walls being supported upright by tension wires through perforations in the side walls. As disclosed, the trough is not waterproof and not suitable for a closed trough-like pond.
U.S. Pat. No. 5,846,816 to Forth (“Forth”) discloses a biomass production apparatus including a transparent chamber which has an inverted, triangular cross-section. Although the “Forth” bioreactor promotes the growth of biological matter, it contradicts the principles extensively tested by Tredici, Fraunhofer and National Labs that assert the need to maximize exposed surface area to sunlight relative to the volume displaced. Furthermore, the disclosed chamber is expensive to manufacture. Finally, the constant circulation of the liquid required by “Forth” interferes with the growth of some types of biological matter. For instance, fully differentiated aquatic plants from the lemnaceae or “duckweed” family are fresh-water plants that grow best on the surface of the water. Such surface growing plants typically prefer relatively still water to support and promote optimal growth.
Often, the importance of the surface area directly exposed to sunlight and which can benefit from the photosynthesis process has been overlooked in prior art. Consequently, many inventions have paid more attention to the volume of water and of the over diluted algal suspension being displaced than the actual available amount of photon per square meter available to that algal solution. This resulting low-efficiencies have lead to the necessity of oversizing algae farming facilities and consequently to high costs in investment, operations and energy.
One object of the present invention is to provide a photobioreactor comprising at least one translucent flexible sheet shapable by a support assembly forming thereby an elongated channel adapted for biomass production therewithin.
Another object of the present invention is to provide a photobioreactor comprising at least one translucent flexible memory sheet shapable to form an elongated channel adapted to be mountable on a support assembly for biomass production therewithin.
Another object of the present invention is to provide a kit for making a photobioreactor, the kit comprising:
Another object of the present invention is to provide a kit for making a floatable photobioreactor, the kit comprising;
These and other objects and advantages of the invention will become apparent upon reading the detailed description and upon referring to the drawings in which:
The present invention provides a photobioreactor made of a translucent flexible sheet or of a translucent flexible memory sheet that is shapable and rollable. The photobioreactor is thus easy to install and to transport at low cost. Further, the photobioreactor combines the control of microalgae culture typical to photobioreactor and the scability provided by pounds. The photobioreactor further maximizes exposure to sunlight with a high surface-to-volume ratio, minimizing water leakage and is rapid to assemble.
Referring to
In another embodiment, the photobioreactor 10 comprises at least one translucent flexible memory sheet which is shapable during manufacturing. In this embodiment, the translucent flexible memory sheet can be shaped by any known means to form an elongated channel such as by hands or by a support or may hold its shape by nature of shape memory provided during manufacturing. Thus in this embodiment, the shaped channel is adapted to be mounted on the support assembly 14.
As the translucent flexible sheet 12 and the translucent flexible memory sheet are flexible, they can be bent and/or rolled and can be provided in a compact roll reducing thereby transport, storage and installation costs of the photobioreactor.
In one embodiment, the photobioreactor comprises a translucent cover 18 attachable to opposite longitudinal edges 20 and 22 of the elongated channel 16. The translucent cover 18 can thus close a top portion of the elongated channel 16. The translucent cover 18 is attachable to the opposite longitudinal edges 20 and 22 by any known means such as but not limited to hooks or pressed between opposite longitudinal edges 20 and 22 and respectively upper portions of support assembly 14. The translucent cover 18 can be removed by being rolled or wrapped around a rotating horizontal axle from a trolley that is moved along and above the elongated channel 16. The removal of the translucent cover 18 may be automated. The translucent cover may comprise a porthole 17 for removal of gases or for introduction of elements into the bioreactor 10.
As shown at
In one embodiment, the support assembly 14 may comprise a plurality of brackets 28 as shown at
In another embodiment, the photobioreactor 10 can be positioned over a liquid surface. The photobioreactor 10 can float directly on the liquid surface or can comprise a floating assembly 36 which is mountable on and along the length of the elongated channel 16 as shown at
In one embodiment, the elongated channel 16 further comprises side-openings 19 which can be positioned at equal distance from each other on opposite sides of the translucent flexible sheet 12 as shown in
As shown at
In another embodiment, the support assembly 14 can further comprise a plurality of frames 44, each frame 44 are adapted to elevate the elongated channel 16 above ground as shown at
The support assembly 14 can further comprise a plurality of shape-sustaining supports 54 as shown at
In another embodiment, the width of the cavity 62 and the shape of the recess 64 may vary from one shape-sustaining support to another. Thus the width and the depth of the elongated channel 16 and the shape of the water pocket 34 may vary along the length of the elongated channel 16. In a first example, the shape of the elongated channel 16 may vary from a generally oval-shape channel into a funnel-shape channel, thus gradually funneling algal flow into a harvester system (not shown) for dewatering and extraction of algal oil. In another embodiment, a T-shape elongated channel 16 may gradually take on a different shape such as M-shape and finish into a cylindrical-shape or an inclined-shape elongated channel. Each of these shapes has their own merits. For example, an inclined-shape channel enables to have deeper water on one side of the channel which results into an increase of residence time during mixing of gases with water. Often microalgae inoculation is done in a closed photobioreactor prior to transferring the resulting culture into an opened or closed photobioreactor for mass culture. The shape of the photobioreactor 10 can be adapted to enhance both the control existing in photobioreactor and the scalability of opened or closed ponds, without facing challenges of connectivity between the two systems.
In another embodiment, the height of the base 56 is adjustable by any known means. For example, each base 56 may comprise a leg 66 mountable thereon further elevating the elongated channel 16 above the ground. The leg 66 can be slidebly mountable on the base 56 using rails as shown at
In another embodiment, the base 56 comprises a height-adjustable delta-shape as shown at
The first shape-sustaining support and the second shape-sustaining support transfer weight of the elevated photobioreactor 10 across its width to the ground. The distribution of weight allows the base 56 to use low-cost construction materials such as wood, plastic-lumber, fiberglass, fiber-cement, clay, magnesium oxide, gypsum, metal plate or a combination thereof.
The height of the photobioreactor 10 can substantially be maintained constant along its length by adjusting the height of the frame 44 or by adjusting the height of the shape-sustaining support 54. Furthermore, the height of the photobioreactor 10 can also vary along its length by adjusting the height of the frame 44 or by adjusting the height of the shape-sustaining support 54. This becomes advantageous to create a cascade where algal solution can flow from higher level of the elongated channel 16 into gradually a lower level of the elongated channel 16, thus reducing the need for pumps.
The photobioreactor 10 can also comprise a reflective material 72 located adjacent the elongated channel 16 as shown at
The photobioreactor 10 may further comprise a translucent sleeve 74 insertable into the elongated channel 16 for biomass production therewithin as shown at
In another embodiment, as shown at
In one embodiment, the photobioreactor 10 may comprise a dewatering system. To dewater the biomass, the sleeve 74 may be provided with an upper translucent film 78 and a bottom osmosis membrane 80. The sleeve 74 can be partially filled with a liquid such as fresh water and a biomass suspension. The sleeve 74 can be adapted to float within the photobioreactor 10 over a fluid of higher solute concentration than its own fluid content such as sea water. It is known that any liquid of lower solute concentration flows through an osmosis membrane to a liquid of higher solute concentration to seek equilibrium. This flow effect causes dehydration of biomass.
In another embodiment, dewatering of the biomass may be achieved by providing the sleeve 74 made entirely of an osmosis membrane partially filled with salt water. Water content in diluted biomass present in the photobioreactor 10 permeates through the osmosis membrane of sleeve 74 and flows towards the higher solute concentration present within the sleeve 74 causing dehydration of biomass.
To enhance biomass growth, the translucent flexible sheet, the translucent flexible memory sheet or the translucent sleeve may comprise antibacterial additives, anti-rotifier additives, ultra-violet absorbent, infra-red absorbent, ultra-violet and infra-red blocker film, additives or film absorbing photo inhibitive wavelengths, spectral shifting dyes, absorbents for all sunlight wavelengths except wavelengths between 400 nm and 700 nm absorbents for all sunlight wavelengths except wavelengths between 660 to 700 nm or a combination thereof.
In another embodiment, the photobioreactor 10 may further comprise a temperature controlling system. A second translucent flexible sheet 82 or a second translucent flexible memory sheet shapable by the support assembly 14 may be wrapped around the elongated channel 16 as shown at
In one embodiment, the translucent flexible sheet 12, the translucent flexible memory sheet, the second translucent flexible sheet 82, the second translucent flexible memory sheet or the translucent cover 18 is made of a material such as fiber reinforced plastic, low density polyethylene, high-density polyethylene, hard acrylic, polyvinyl chloride, polycarbonate, composite plastic, ethylene vinyl acetate, fiberglass and a combination thereof. Fiberglass offers advantages such as durability and ease of repair and maintenance. A fiberglass sheet typically may last as long as 25 years or more making return on investment substantially affordable.
The translucent flexible sheet 12, the translucent flexible memory sheet, the second translucent flexible sheet 82, the second translucent flexible memory sheet or the translucent cover 18 may be about 0.5 mm to 1.2 mm thick, about 3 m to 50 m long and about 0.5 m to 2.5 m wide.
In another embodiment, the translucent flexible sheet 12, the translucent flexible memory sheet, the second translucent flexible sheet 82, the second translucent flexible memory sheet or the translucent cover 18 may further include attached thereto or embedded therein a biomass growth monitor assembly, a biomass growth detector assembly and/or a biomass growth promoter assembly. These assemblies may comprise the following components: flexible wire, sensor, light emitting diode, optical sensor, Bluetooth short-range connection, photovoltaic cell, microplate reader, batterie, piezo-electric vibrator, thermotropic crystal, liquid crystal, suspended particle display, electrochromic film, reflective hydride, heating element, heating tape, wire to generate electromagnetic field, electrode and a combination thereof. To enhance biomass productivity, the electronically-connected devices mentioned above, may be electronically pulsated so as to manipulate intensity and frequency of light sources, to flash light, to generate magnetic waves or to generate electrical pulses that enhance the oil extraction process.
Further, as shown at
Agitation of the biomass within the photobioreactor 10 can be achieved by any known means such as a wave generation system, pump or water wheel. When the production of a sterile cultivation of the biomass is required, the agitation equipment is configured to maintain a degree of air-tightness that prevents air contamination from outside. The suspended algal solution within the translucent sleeve 74 is agitated by one or multiple wave generators which can comprise bellows that inflate at controlled time by lifting at a time interval the sleeve 74 creating thus a wave moving along the length of the photobioreactor 10. Once the wave has reached its destination, the sleeve 74 is lowered and lifted again to generate the following wave and the cycle is repeated. In one embodiment, a wave generation system is connectable to one end of the photobioreactor 10. In one embodiment, a wave generator connectable to one end of the photobioreactor 10 lifts angularly a volume of water and empties it to flow in the elongated channel 16.
Referring to
As shown in
Arrows in
Referring to
In another embodiment, the present invention provides a kit for making a photobioreactor. The kit comprises the support assembly 14 and at least one translucent flexible sheet 12 shapable by the support assembly 14 forming thereby the elongated channel 16 adapted for biomass production therewithin. The kit may further comprise the above-mentioned elements.
In another embodiment, the present invention provides a kit for making a floatable photobioreactor. The kit comprises a floating assembly 36 and at least one translucent flexible memory sheet shapable to form an elongated channel. The elongated channel is mountable on the floating assembly 36 forming thereby a floatable elongated channel adapted for biomass production therewithin. The kit may further comprise the above-mentioned elements.
As the translucent flexible sheet or the translucent flexible memory sheet is made of flexible sheet such as fiberglass, the bending stress applied to shape them into an elongated channel is well tolerated by the flexible sheet. Consequently, the elongated channel may be spanned or elevated at a longer distance than a typical sheet. This translates into longer span than may be projected between load-bearing or support assembly than a typical sheet. This advantage reduces costs and makes commercial scale-up of biomass production more affordable.
Further, the photobioreactor of the present invention has the advantage of combining the scalability and cost-effectiveness offered by open ponds with the biomass growth control provided by photobioreactors such as providing a high surface-to-volume light exposure ratio and light exposure from different directions.
The scope of the claims should not be limited by the preferred embodiments set forth in the examples, but should be given the broadest interpretation consistent with the description as a whole.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2,761,251 | Dec 2011 | CA | national |
| 2,764,291 | Jan 2012 | CA | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/CA2012/050750 | 10/22/2012 | WO | 00 | 6/4/2014 |
