Introduction
Currently, each stage in algae’s biofuel production requires more energy than it produces. In order for algae to become a true contender in the biofuel race, the entire algae-to-oil pathway must be energy positive and environmentally sustainable. This project addresses each step in the oilgae production: cultivation, harvesting, extraction and transesterification. By identifying the obstacles, engineering equipment, and refining the processes, formulating an economically and environmentally viability green diesel alternative is in the near future.
This project is a culmination of four years of experimentation wherein the first year a bioreactor was specifically designed to enhance the algae cell count. Various fertilizers were tested to determine which supplement created the largest algae bloom. The second year’s project focused on designing two separate bioreactors: an incubator and a vessel. The purpose of the incubator was to force the Spirogyra to fragment thereby inducing asexual reproduction for intercalary mitosis to form new filaments. The vessels’ purpose was to test new variables to enhance algae’s growth. It was hypothesized that if Spirogyra is grown in a photo-bioreactor and enriched with carbon dioxide in a hydrostatic vessel and an ambient vessel, the Spirogyra enriched with carbon dioxide in the hydrostatic vessel will have a higher growth rate than Spirogyra enriched with carbon dioxide in the ambient vessel. The third year of testing involved the engineering of a prism photo-bioreactor that enhanced the light spectrum to increase algae proliferation. A closed loop system through the photo-bioreactor allowed for air agitation and constant diet of CO₂. A chemically-free method of dewatering was created and an ultrasonic vacuum was utilized for lipid extraction.
This year’s project seeks to broaden the scope by evaluating the entire algae to biofuel conversion process and developing new methodologies and equipment that can make algae oil a viable solution to our existing fuel problems. Each step of algae oil production was thoroughly researched and examined for development. The decision to cultivate algae in a photoautotrophic bioreactor enhanced with Neon and Helium gases was a direct result of last year’s experiment wherein a prism was used to separate light wavelengths to determined which light energy provide the greatest increase in algae growth. After studying bright line spectra of noble gases, it was determined that Neon and Helium could be used to filter light waves. Double walled bioreactors were designed allowing each noble gas to surround the algae biomass, filtering only a specific light wavelength that can be absorbed by the algae solution. This experiment involved the red-orange light spectrum and the blue-green light spectrum. A bioreactor containing natural air was also included as a constant. In addition, the bioreactors had controlled air and mechanical agitation to ensure optimal light penetration through the entire solution. The horizontal positioning of the bioreactors provided a high surface-to-volume CO₂ ratio and maximized lux penetration to the solution. A closed-loop nutrient control chamber attached to the bioreactor allowed uniform dispersion of CO₂ and Fe⁺², the solution’s constant diet.
The use of bioreactors to cultivate algae is supported by years of research. The bioreactor engineered for this project is one of first impression. The idea to create a bioreactor that filters specific light wavelengths was a result of studying the effects of light on photosynthesis (Taiz). The higher energy level of the red light spectrum causes the driver of the algae’s cellular activity, ATP (Adenosine Triphosphate), to convert H₂O and CO₂ into glucose faster resulting in higher reproduction rates. Although it was thought that the blue-green light spectrum would provide the optimal growing environment due to its short wavelength and high energy, the red-orange light energy provided the highest growth rate as the blue-green waves were reflected off the algae’s surface while the red - orange light was absorbed by the solution.
₃ Industry standards for harvesting the biomass include centrifugation, air flotation, and filtration. All are associated with high capital cost, toxic chemicals and high energy consumption. In an effort to maintain a green methodology, ionic flocculation was utilized in this experiment. Although prior studies conducted by this researcher utilizing ionic flocculation were promising there was still an issue of residual biomass that was left uncaptured. After researching pH fluctuations and lipid accumulation, it was determined that increasing the pH to a base level above 8.2 would promote biomass settlement. A study conducted by Montana State University found that adding a carbonate to an algae growth system increased pH level significantly and induced lipid accumulation (Gardner). The addition of carbonate triggers a buildup of TAGS, the molecule that comprises fatty acid methyl esters (FAME), the main component of biodiesel. Utilizing this knowledge, flocculation methods were modified by adding Na₂CO₃ to the biomass two weeks prior to flocculation. During this two week period the algae was starved of CO₂ and pH levels were manipulated to 8.5. Fe+² was also added to the growth medium serving a dual purpose; (1) the presences of Fe+² increases the solution’s ability to absorb CO₂ during cultivation, and (2) Fe+² facilitates flocculation. Through Coulombic interactions, Fe+² ionicly bonded with O₂ to form Fe₂O₃, a polymer that bridged the surface of the Spirogyra cells producing a floc yield that was significantly higher than last year. Furthermore, there was no need to cleanse the flocculated biomass before extraction as the Fe+² ions were oxidized forming Fe₂ which were hydrated into the algae solution. Additionally, there was no chemical waste water to dispose of, as any remaining algae solute was recycled for further cultivation.
The methods currently used in the market for lipid extraction and conversion require multiple steps including drying the biomass, chemical infusion, solvent recovery, and/or severe reaction conditions. The benchmark for lipid extraction is the Bligh and Dyer method which requires a mixture of methanol and chloroform to frack the cell membrane and separate the lipids from the biomass. Although the method touts a 90% recovery rate, the amount and type of solvents necessary make this a toxic, high energy process. Recognizing the need to rid the green biofuel of chemical solvents, researchers are testing methods that include pulsed electric field, ion resins, emzyme catalyst, microwaving, mechanical pressing, homogenization, bead beating, hydrodynamic cavitation, and osmotic shock for cell disruption. After extraction, the lipids are transesterified into a biodiesel. Recently, alternative methods have been explored wherein extraction and conversion are combined in what has been coined “in situ” conversion. In this process, alcohol or carbon dioxide plays the role of both the solvent and the reactant in a one step, super critical method that employs reaction temperatures of 255˚C and pressure in excess of 40 bars (Soh)., a energy sinker for the green biofuel.
In an effort to maintain energetic feasibility and environmental sustainability, this researcher engineered the cellulose-blaster, a high pressured ultrasonic tank that extracted the lipids in one step using a combination of osmotic shock, homogenization and sonication for cell disruption. The algae cells were lysed in an osmotic bath then forced through a pressurized orifice while being bombarded with ultrasonic waves. This three-in-one method sheared the cell wall and released the lipids, avoiding high-energy costs. To maintain economic viability, the lipid oil was recycled through the cellulose blaster where it was transesterified into a fuel using Ba(OH)₂ and CH₄O under ultrasonic, homogenization conditions. Unlike traditional transesterification processes with large energy and chemical requirements, the cellulose-blaster was able to cut the reaction time and static time in half keeping energy consumption at a minimum. Further research plans include creating an in situ supercritical process wherein the cellulose-blaster is built to withstand high pressure, high temperature, and high frequency ultrasound for a one-step extraction and transesterification process without the use of a base catalyst.
This project is a culmination of four years of experimentation wherein the first year a bioreactor was specifically designed to enhance the algae cell count. Various fertilizers were tested to determine which supplement created the largest algae bloom. The second year’s project focused on designing two separate bioreactors: an incubator and a vessel. The purpose of the incubator was to force the Spirogyra to fragment thereby inducing asexual reproduction for intercalary mitosis to form new filaments. The vessels’ purpose was to test new variables to enhance algae’s growth. It was hypothesized that if Spirogyra is grown in a photo-bioreactor and enriched with carbon dioxide in a hydrostatic vessel and an ambient vessel, the Spirogyra enriched with carbon dioxide in the hydrostatic vessel will have a higher growth rate than Spirogyra enriched with carbon dioxide in the ambient vessel. The third year of testing involved the engineering of a prism photo-bioreactor that enhanced the light spectrum to increase algae proliferation. A closed loop system through the photo-bioreactor allowed for air agitation and constant diet of CO₂. A chemically-free method of dewatering was created and an ultrasonic vacuum was utilized for lipid extraction.
This year’s project seeks to broaden the scope by evaluating the entire algae to biofuel conversion process and developing new methodologies and equipment that can make algae oil a viable solution to our existing fuel problems. Each step of algae oil production was thoroughly researched and examined for development. The decision to cultivate algae in a photoautotrophic bioreactor enhanced with Neon and Helium gases was a direct result of last year’s experiment wherein a prism was used to separate light wavelengths to determined which light energy provide the greatest increase in algae growth. After studying bright line spectra of noble gases, it was determined that Neon and Helium could be used to filter light waves. Double walled bioreactors were designed allowing each noble gas to surround the algae biomass, filtering only a specific light wavelength that can be absorbed by the algae solution. This experiment involved the red-orange light spectrum and the blue-green light spectrum. A bioreactor containing natural air was also included as a constant. In addition, the bioreactors had controlled air and mechanical agitation to ensure optimal light penetration through the entire solution. The horizontal positioning of the bioreactors provided a high surface-to-volume CO₂ ratio and maximized lux penetration to the solution. A closed-loop nutrient control chamber attached to the bioreactor allowed uniform dispersion of CO₂ and Fe⁺², the solution’s constant diet.
The use of bioreactors to cultivate algae is supported by years of research. The bioreactor engineered for this project is one of first impression. The idea to create a bioreactor that filters specific light wavelengths was a result of studying the effects of light on photosynthesis (Taiz). The higher energy level of the red light spectrum causes the driver of the algae’s cellular activity, ATP (Adenosine Triphosphate), to convert H₂O and CO₂ into glucose faster resulting in higher reproduction rates. Although it was thought that the blue-green light spectrum would provide the optimal growing environment due to its short wavelength and high energy, the red-orange light energy provided the highest growth rate as the blue-green waves were reflected off the algae’s surface while the red - orange light was absorbed by the solution.
₃ Industry standards for harvesting the biomass include centrifugation, air flotation, and filtration. All are associated with high capital cost, toxic chemicals and high energy consumption. In an effort to maintain a green methodology, ionic flocculation was utilized in this experiment. Although prior studies conducted by this researcher utilizing ionic flocculation were promising there was still an issue of residual biomass that was left uncaptured. After researching pH fluctuations and lipid accumulation, it was determined that increasing the pH to a base level above 8.2 would promote biomass settlement. A study conducted by Montana State University found that adding a carbonate to an algae growth system increased pH level significantly and induced lipid accumulation (Gardner). The addition of carbonate triggers a buildup of TAGS, the molecule that comprises fatty acid methyl esters (FAME), the main component of biodiesel. Utilizing this knowledge, flocculation methods were modified by adding Na₂CO₃ to the biomass two weeks prior to flocculation. During this two week period the algae was starved of CO₂ and pH levels were manipulated to 8.5. Fe+² was also added to the growth medium serving a dual purpose; (1) the presences of Fe+² increases the solution’s ability to absorb CO₂ during cultivation, and (2) Fe+² facilitates flocculation. Through Coulombic interactions, Fe+² ionicly bonded with O₂ to form Fe₂O₃, a polymer that bridged the surface of the Spirogyra cells producing a floc yield that was significantly higher than last year. Furthermore, there was no need to cleanse the flocculated biomass before extraction as the Fe+² ions were oxidized forming Fe₂ which were hydrated into the algae solution. Additionally, there was no chemical waste water to dispose of, as any remaining algae solute was recycled for further cultivation.
The methods currently used in the market for lipid extraction and conversion require multiple steps including drying the biomass, chemical infusion, solvent recovery, and/or severe reaction conditions. The benchmark for lipid extraction is the Bligh and Dyer method which requires a mixture of methanol and chloroform to frack the cell membrane and separate the lipids from the biomass. Although the method touts a 90% recovery rate, the amount and type of solvents necessary make this a toxic, high energy process. Recognizing the need to rid the green biofuel of chemical solvents, researchers are testing methods that include pulsed electric field, ion resins, emzyme catalyst, microwaving, mechanical pressing, homogenization, bead beating, hydrodynamic cavitation, and osmotic shock for cell disruption. After extraction, the lipids are transesterified into a biodiesel. Recently, alternative methods have been explored wherein extraction and conversion are combined in what has been coined “in situ” conversion. In this process, alcohol or carbon dioxide plays the role of both the solvent and the reactant in a one step, super critical method that employs reaction temperatures of 255˚C and pressure in excess of 40 bars (Soh)., a energy sinker for the green biofuel.
In an effort to maintain energetic feasibility and environmental sustainability, this researcher engineered the cellulose-blaster, a high pressured ultrasonic tank that extracted the lipids in one step using a combination of osmotic shock, homogenization and sonication for cell disruption. The algae cells were lysed in an osmotic bath then forced through a pressurized orifice while being bombarded with ultrasonic waves. This three-in-one method sheared the cell wall and released the lipids, avoiding high-energy costs. To maintain economic viability, the lipid oil was recycled through the cellulose blaster where it was transesterified into a fuel using Ba(OH)₂ and CH₄O under ultrasonic, homogenization conditions. Unlike traditional transesterification processes with large energy and chemical requirements, the cellulose-blaster was able to cut the reaction time and static time in half keeping energy consumption at a minimum. Further research plans include creating an in situ supercritical process wherein the cellulose-blaster is built to withstand high pressure, high temperature, and high frequency ultrasound for a one-step extraction and transesterification process without the use of a base catalyst.