Abstract:
A portable system and method for producing biofuel from algae are disclosed. In the portable system, a chemostat and a plug flow reactor formed from plastic bladders are interconnected. Further, an algae separator is in fluid communication with the plug flow reactor for removing algae cells. Also, the system includes a device for processing biofuel from the algae cells. Importantly, the system includes a temperature controller to maintain desired temperatures in the chemostat and plug flow reactor for algae growth and intracellular algae production. In order to further support algae cell growth, the system includes a device for capturing carbon dioxide and delivering the carbon dioxide to the chemostat.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention pertains generally to processes for producing biofuel from oil in algae. More particularly, the present invention pertains to a portable system that grows algae cells having a high oil content and synthesizes the oil into biofuel. The present invention is particularly, but not exclusively, useful as a portable system and method that utilizes available carbon in waste and pollution to grow algae for processing into biofuel. 
       BACKGROUND OF THE INVENTION 
       [0002]    As worldwide petroleum deposits decrease, there is rising concern over shortages and the costs that are associated with the production of hydrocarbon products. As a result, alternatives to products that are currently processed from petroleum are being investigated. In this effort, biofuels such as biodiesel have been identified as a possible alternative to petroleum-based transportation fuels. In general, biodiesel is a fuel comprised of mono-alkyl esters of long chain fatty acids derived from plant oils or animal fats. In industrial practice, biodiesel is created when plant oils or animal fats are reacted with an alcohol, such as methanol. 
         [0003]    For plant-derived biofuel, solar energy is first transformed into chemical energy through photosynthesis. The chemical energy is then refined into a usable fuel. Currently, the process involved in creating biofuel from plant oils is expensive relative to the process of extracting and refining petroleum. It is possible, however, that the cost of processing a plant-derived biofuel could be reduced by maximizing the rate of growth of the plant source. Because algae is known to be one of the most efficient plants for converting solar energy into cell growth, it is of particular interest as a biofuel source. However, current algae processing methods have failed to result in a cost effective algae-derived biofuel. 
         [0004]    In overview, the biochemical process of photosynthesis provides algae with the ability to convert solar energy into chemical energy. During cell growth, this chemical energy is used to drive synthetic reactions, such as the formation of sugars or the fixation of nitrogen into amino acids for protein synthesis. Excess chemical energy is stored in the form of fats and oils as triglycerides. Thus, the creation of oil in algae only requires sunlight, carbon dioxide and the nutrients necessary for formation of triglycerides. Nevertheless, with the volume requirements for a fuel source, the costs associated with the inputs are high. 
         [0005]    In certain applications, costs associated with conventional fuels are also quite high. Specifically, forward military bases and remote exploratory camps experience high fuel costs due to the expenses involved in delivering fuel. Also, ships typically must travel to ports simply to refuel. Therefore, fuel costs can be reduced if fuel is produced at the desired site, rather than transported to the desired site. 
         [0006]    In light of the above, it is an object of the present invention to provide a system and method for producing biofuel from algae which reduces input costs. For this purpose, a number of systems have been developed, such as those disclosed in co-pending U.S. patent application Ser. No. ______ for an invention entitled “High Efficiency Separations to Recover Oil from Microalgae,” which is filed concurrently herewith, co-pending U.S. patent application Ser. No. 11/549,532 for an invention entitled “Photosynthetic Oil Production in a Two-Stage Reactor” filed Oct. 13, 2006, co-pending U.S. patent application Ser. No. 11/549,541 for an invention entitled “Photosynthetic Carbon Dioxide Sequestration and Pollution Abatement” filed Oct. 13, 2006, co-pending U.S. patent application Ser. No. 11/549,552 for an invention entitled “High Photoefficiency Microalgae Bioreactors” filed Oct. 13, 2006, and co-pending U.S. patent application Ser. No. 11/549,561 for an invention entitled “Photosynthetic Oil Production with High Carbon Dioxide Utilization” filed Oct. 13, 2006. All aforementioned co-pending U.S. patent applications are assigned to the same assignee as the present invention, and are hereby incorporated by reference. Another object of the present invention is to provide a portable recycling system for feeding oil harvesting byproducts back to the conduit where high oil content algae is grown. Still another object of the present invention is to provide a portable system for supplying nutrients to algae cells in the form of processed algae cell matter. Another object of the present invention is to provide a portable system for recycling the glycerin byproduct from the creation of biofuel as a source of carbon to foster further oil production in algae cells. Another object of the present invention is to provide a portable system for processing oil from algae that defines a flow path for continuous movement of the algae and its processed derivatives. Yet another object of the present invention is to provide a portable system and method for producing biofuel from algae with high oil content that is simple to implement, easy to use, and comparatively cost effective. 
       SUMMARY OF THE INVENTION 
       [0007]    In accordance with the present invention, a portable system is provided for efficiently producing biofuel from algae. For this purpose, the system utilizes a collapsible plastic bladder that forms a chemostat and a plug flow reactor. Structurally, the chemostat defines a conduit for growing algae cells. The chemostat&#39;s conduit includes input ports for feeding material into the conduit as well as an output port. Further, the plug flow reactor defines a conduit for fostering oil production within the algae cells. For the present invention, the plug flow reactor has an input port that is positioned to receive material from the output port of the chemostat. Also the system is provided with a temperature control that monitors and maintains the temperature within the conduits. 
         [0008]    In addition to the plastic bladder and temperature control, the system includes an algae separator. Specifically, the algae separator is positioned in fluid communication with the plug flow reactor to remove an algae cell concentrate from the plug flow reactor&#39;s conduit. Structurally, the algae separator includes an outlet for the remaining effluence which is in fluid communication with the input port of the chemostat. Further, the system includes a device for lysing algae cells to unbind oil from the algae cells. For purposes of the present invention, the lysing device is positioned to receive algae cells from the algae separator. 
         [0009]    Downstream of the lysing device, the system includes an oil separator that receives the lysed cells and withdraws the oil from remaining cell matter. For purposes of the present invention, the oil separator has an outlet for the remaining cell matter which is in fluid communication with the input port of the chemostat. Further, the system may include a hydrolyzing device interconnected between the oil separator and the chemostat. In addition to the cell matter outlet, the oil separator includes an outlet for the oil. For the present invention, the system includes a biofuel reactor that is in fluid communication with the outlet for oil. In a known process, the biofuel reactor reacts an alcohol with the oil to synthesize biofuel and, as a byproduct, glycerin. Structurally, the biofuel reactor includes an exit for the glycerin that is in fluid communication with the input port of the plug flow reactor. 
         [0010]    For purposes of the present invention, the system includes a scrubber having a chamber for receiving a pollutant-contaminated fluid stream and a scrubber solution. Typically, the fluid stream comprises flue gas from a combustion source, such as a power plant or incinerator. Further, the scrubber solution is typically a caustic or sodium bicarbonate. Downstream of the algae separator, the system includes a channel for recycling an effluence from the plug flow reactor to the scrubber for reuse as the scrubber solution. 
         [0011]    In operation, the flue gas from the power plant is flowed through the chamber of the scrubber. At the same time, the scrubber solution is sprayed into the scrubber chamber to capture the pollutants in the flue gas. The scrubber solution with the entrapped pollutants is then delivered to the chemostat through its input port. Also, a nutrient mix may be fed into the chemostat through the input port to form, along with the scrubber solution, a medium for growing algae cells. As the medium circulates through the conduit of the chemostat, the algae cells grow using solar energy and converting the pollutants and other nutrients to cell matter. Preferably, a continuous flow of the medium washes the algae cells and constantly removes them from the chemostat as overflow. In the plug flow reactor, the algae cells are treated to produce intracellular oil. Thereafter, the algae separator removes the algae cells from the remaining effluence in the plug flow reactor. 
         [0012]    Then, the effluence is recycled through a channel back to the scrubber for reuse as the scrubber solution. At the same time, the algae cells are delivered to the cell lysis apparatus. At the cell lysis device, the cells are lysed, preferably with steam, to unbind the oil from the remaining cell matter. This unbound cell material is received by the oil separator from the cell lysis device. Next, the oil separator withdraws the oil from the remaining cell matter and effectively forms two streams of material. The stream of remaining cell matter is transferred to the hydrolysis device where the cell matter is broken into small units which are more easily absorbed by algae cells during cell growth. Thereafter, the hydrolyzed cell matter is delivered to the chemostat to serve as a source of nutrition for the algae cells growing therein. At the same time, the stream of oil is transmitted from the oil separator to the biofuel reactor. In the biofuel reactor, the oil is reacted with an alcohol to form biofuel and a glycerin byproduct. The glycerin byproduct is fed back into the plug flow reactor to serve as a source of carbon for the algae cells therein during the production of intracellular oil. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    The novel features of this invention, as well as the invention itself, both as to its structure and its operation, will be best understood from the accompanying drawing, taken in conjunction with the accompanying description, in which the FIGURE is a schematic view of the portable system for producing biofuel from algae in accordance with the present invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0014]    Referring to the FIGURE, a portable system for producing biofuel from algae in accordance with the present invention is shown and generally designated  10 . As shown, the system  10  includes a plastic bladder  12  that forms at least one chemostat  14  for growing algae cells (exemplary cells depicted at  16 ) and a plug flow reactor  18  for treating the algae cells  16  to trigger cell production of triglycerides. For purposes of the present invention, the plastic bladder  12  is easily collapsed and stored to facilitate transportation to, and assembly of the system  10 , at remote locations. 
         [0015]    As shown in the FIGURE, the chemostat  14  includes a conduit  20 . As further shown, the conduit  20  is provided with an input port  22  for receiving a medium  24 . For purposes of the present invention, the input port  22  is also in communication with a reservoir (not illustrated) holding a nutrient mix (indicated by arrow  26 ). Preferably, the nutrient mix  26  includes phosphorous, nitrogen, sulfur and numerous trace elements necessary to support algae growth. Further, the chemostat  14  is provided with an Archimedes screw  28  for causing the medium  24  and the nutrient mix  26  to continuously circulate around the conduit  20  at a predetermined fluid flow velocity. Also, each conduit  20  is provided with an output port  30  in communication with the plug flow reactor  18 . 
         [0016]    As shown, the plug flow reactor  18  includes an input port  32   a  for receiving overflow medium (indicated by arrow  24 ′) with algae cells  16  from the output port  30  of the chemostat  14 . As further shown, the plug flow reactor  18  includes a conduit  34  for passing the medium  24 ″ with algae cells  16  downstream. The flow rate of the medium  24 ″ is due solely to gravity and the force of the incoming overflow medium  24 ′ from the chemostat  14 . Preferably, the plug flow reactor  18  has a substantially fixed residence time of about one to four days. For purposes of the present invention, the system  10  is provided with a reservoir (not shown) that holds a modified nutrient mix (indicated by arrow  36 ). Further, the conduit  34  is provided with an input port  32   b  for receiving the modified nutrient mix  36 . In order to manipulate the cellular behavior of algae cells  16  within the plug flow reactor  18 , the modified nutrient mix  36  may contain a limited amount of a selected constituent, such as nitrogen or phosphorous. For instance, the nutrient mix  36  may contain no nitrogen. Alternatively, the algae cells  16  may exhaust nutrients such as nitrogen or phosphorous in the nutrient mix  26  at a predetermined point in the plug flow reactor  18 . By allowing such nutrients to be exhausted, desired behavior in the algae cells  16  can be caused without adding a specific modified nutrient mix  36 . Further, simply water can be added through the modified nutrient mix  36  to compensate for evaporation. In addition to input ports  32   a  and  32   b,  the conduit  34  is further provided with an input port  32   c  to receive other matter. 
         [0017]    For purposes of the present invention, the system  10  further includes a temperature control  38  that is connected to the chemostat  14  and the plug flow reactor  18  via leads  39 . Specifically, the temperature control  38  monitors the temperature of the medium  24  and heats or cools the medium  24  as needed to provide a suitable environment for algae growth. 
         [0018]    As shown in the FIGURE, the system  10  also includes an algae separator  40  for removing the algae cells  16  from the plug flow reactor  18 . Specifically, the algae cells  16  form an algae cell concentrate  41  that is separated by the algae separator  40  from the medium  24 ″ and the remaining nutrients therein through flocculation and/or filtration. As further shown, the algae separator  40  includes an effluence outlet  42  and an algae cell outlet  44 . 
         [0019]    For further purposes of the present invention, the system  10  includes a scrubber  46  for scrubbing a pollutant-contaminated fluid stream. Specifically, the scrubber  46  includes a chamber  48  and an input port  50   a  for receiving flue gas from a combustion source such as a power plant or incinerator  52  and a scrubber solution  54 . Typically, the flue gas includes pollutants such as carbon dioxide, sulfur oxides, and/or nitrogen oxides. Also, the scrubber solution  54  typically comprises sodium phosphate or sodium bicarbonate. As further shown, the scrubber  46  includes a solution outlet  56  and a gas outlet  58 . As illustrated, the solution outlet  56  is in fluid communication with the input port  22  of the chemostat  14 . For purposes of the present invention, the scrubber  46  includes a solution input port  50   b  in the scrubber chamber  48 . Further, the system  10  includes a channel  60  providing fluid communication between the effluence outlet  42  and the scrubber  46  through the solution input port  50   b.  Also, the system  10  includes an oxidation stage  62  for oxidizing pollutants in the flue gas to facilitate their removal from the flue gas. As shown, the oxidation stage  62  is interconnected between the carbon source  52  and the scrubber  46 . 
         [0020]    In the FIGURE, the system  10  includes a cell lysis apparatus  64  that receives algae cells  16  from the algae outlet  44  of the algae separator  40 . As shown, the cell lysis apparatus  64  is in fluid communication with an oil separator  66 . For purposes of the present invention, the oil separator  66  is provided with two outlets  68 ,  70 . As shown, the outlet  68  is connected to a hydrolysis apparatus  72 . Further, the hydrolysis apparatus  72  is connected to the input port  22  in the conduit  20  of the chemostat  14 . 
         [0021]    Referring back to the oil separator  66 , it can be seen that the outlet  70  is connected to a biofuel reactor  74 . It is further shown that the biofuel reactor  74  includes two exits  76 ,  78 . For purposes of the present invention, the exit  76  is connected to the input port  32   c  in the conduit  34  of the plug flow reactor  18 . Additionally or alternatively, the exit  76  may be connected to the input port  22  in the chemostat  14 . Further, the exit  78  may be connected to a tank or reservoir (not shown) for purposes of the present invention. 
         [0022]    In operation of the present invention, pollutant-contaminated flue gas (indicated by arrow  80 ) is directed from the carbon source  52  to the oxidation stage  62 . At the oxidation stage  62 , nitrogen monoxide in the flue gas  80  is oxidized by nitric acid or by other catalytic or non-catalytic technologies to improve the efficiency of its subsequent removal. Specifically, nitrogen monoxide is oxidized to nitrogen dioxide. Thereafter, the oxidized flue gas (indicated by arrow  82 ) is delivered from the oxidation stage  62  to the scrubber  46 . Specifically, the oxidized flue gas  82  enters the chamber  48  of the scrubber  46  through the input port  50   a.  Upon the entrance of the oxidized flue gas  82  into the chamber  48 , the scrubber solution  54  is sprayed within the chamber  48  to absorb, adsorb or otherwise trap the pollutants in the oxidized flue gas  82  as is known in the field of scrubbing. With its pollutants removed, the clean flue gas (indicated by arrow  84 ) exits the scrubber  46  through the gas outlet  58 . At the same time, the scrubber solution  54  and the pollutants exit the scrubber  46  through the solution outlet  56 . 
         [0023]    After exiting the scrubber  46 , the scrubber solution  54  and pollutants (indicated by arrow  86 ) enter the chemostat  14  through the input port  22 . Further, the nutrient mix  26  is fed to the chemostat  14  through the input port  22 . In the conduit  20  of the chemostat  14 , the nutrient mix  26 , scrubber solution  54  and pollutants form the medium  24  for growing the algae cells  16 . This medium  24  is circulated around the conduit  20  by the screw  28 . Further, the conditions in the conduit  20  are maintained for maximum algal growth. For instance, in order to maintain the desired conditions, the medium  24  and the algae cells  16  are moved around the conduit  20  at a preferred fluid flow velocity of approximately fifty centimeters per second. Further, the amount of algae cells  16  in the conduit  20  is kept substantially constant. Specifically, the nutrient mix  26  and the scrubber solution  54  with pollutants  86  are continuously fed at selected rates into the conduit  20  through the input port  22 , and an overflow medium  24 ′ containing algae cells  16  is continuously removed through the output port  30  of the conduit  20 . 
         [0024]    After entering the input port  32   a  of the plug flow reactor  18 , the medium  24 ″ containing algae cells  16  moves downstream through the conduit  34  in a plug flow regime. Further, as the medium  24 ″ moves downstream, the modified nutrient mix  36  may be added to the conduit  34  through the input port  32   b.  This modified nutrient mix  36  may contain a limited amount of a selected constituent, such as nitrogen or phosphorous. The absence or small amount of the selected constituent causes the algae cells  16  to focus on energy storage rather than growth. As a result, the algae cells  16  form triglycerides. 
         [0025]    At the end of the conduit  34 , the algae separator  40  removes the algae cell concentrate  41  from the remaining effluence (indicated by arrow  88 ). Thereafter, the effluence  88  is discharged from the algae separator  40  through the effluence outlet  42 . In order to recycle the effluence  88 , it is delivered through channel  60  to the input port  50   b  of the scrubber  46  for reuse as the scrubber solution  54 . Further, the removed algae cells (indicated by arrow  90 ) are delivered to the cell lysis apparatus  64 . Specifically, the removed algae cells  90  pass out of the algae cell outlet  44  to the cell lysis apparatus  64 . For purposes of the present invention, the cell lysis apparatus  64  lyses the removed algae cells  90  to unbind the oil therein from the remaining cell matter. After the lysing process occurs, the unbound oil and remaining cell matter, collectively identified by arrow  92 , are transmitted to the oil separator  66 . Thereafter, the oil separator  66  withdraws the oil from the remaining cell matter  92  as is known in the art. After this separation is performed, the oil separator  66  discharges the remaining cell matter (identified by arrow  94 ) out of the outlet  68  of the oil separator  66  to the input port  22  of the chemostat  14 . 
         [0026]    In the chemostat  14 , the remaining cell matter  94  is utilized as a source of nutrients and energy for the growth of algae cells  16 . Because small units of the remaining cell matter  94  are more easily absorbed or otherwise processed by the growing algae cells  16 , the remaining cell matter  94  may first be broken down before being fed into the input port  22  of the chemostat  14 . To this end, the hydrolysis apparatus  72  is interconnected between the oil separator  66  and the chemostat  14 . Accordingly, the hydrolysis apparatus  72  receives the remaining cell matter  94  from the oil separator  66 , hydrolyzes the received cell matter  94 , and then passes hydrolyzed cell matter (identified by arrow  96 ) to the chemostat  14 . 
         [0027]    Referring back to the oil separator  66 , it is recalled that the remaining cell matter  94  was discharged through the outlet  68 . At the same time, the oil withdrawn by the oil separator  66  is discharged through the outlet  70 . Specifically, the oil (identified by arrow  98 ) is delivered to the biofuel reactor  74 . In the biofuel reactor  74 , the oil  98  can be reacted with alcohol, such as methanol, to create mono-alkyl esters, i.e., biodiesel fuel. This biodiesel fuel (identified by arrow  100 ) is released from the exit  78  of the biofuel reactor  74  to a tank, reservoir, or pipeline (not shown) for use as fuel. Alternatively, a biofuel  100  may be synthesized in the reactor  74  and converted to jet fuel. In addition to the biofuel  100 , the reaction between the oil  98  and the alcohol produces glycerin as a byproduct. For purposes of the present invention, the glycerin (identified by arrow  102 ) is pumped out of the exit  76  of the biofuel reactor  74  to the input port  32   c  of the plug flow reactor  18 . 
         [0028]    In the plug flow reactor  18 , the glycerin  102  is utilized as a source of carbon by the algae cells  16 . Importantly, the glycerin  102  does not provide any nutrients that may be limited to induce oil production by the algae cells  16  or to trigger flocculation. The glycerin  102  may be added to the plug flow reactor  18  at night to aid in night-time oil production. Further, because glycerin  102  would otherwise provide bacteria and/or other non-photosynthetic organisms with an energy source, limiting the addition of glycerin  102  to the plug flow reactor  18  only at night allows the algae cells  16  to utilize the glycerin  102  without facilitating the growth of foreign organisms. As shown in the FIGURE, the exit  76  of the biofuel reactor  74  may also be in fluid communication with the input port  22  of the chemostat  14  (connection shown in phantom). This arrangement allows the glycerin  102  to be provided to the chemostat  14  as a carbon source. 
         [0029]    While the particular Transportable Algae Biodiesel System as herein shown and disclosed in detail is fully capable of obtaining the objects and providing the advantages herein before stated, it is to be understood that it is merely illustrative of the presently preferred embodiments of the invention and that no limitations are intended to the details of construction or design herein shown other than as described in the appended claims.