Discussion
The objective of this experiment was to develop an energy efficient process to cultivate, harvest, extract, and transesterify algae into an economically and environmentally sustainable biofuel. With fossil fuel prices rising, resources quickly depleting, energy security at the forefront, and alarming environment concerns, a safe, sustainable source of energy has become a necessity. Terrestrial crops have offered little relief and have consequences that are even more devastating than those involved in the production of carbon based fuels. With few alternatives on the horizon, interest in algae oil has escalated. These microorganisms have a higher growth rate and shorter maturity rate than any other plant crop. They can be produced in less space and provide up to one hundred times more oil per acre than any other bio-fuel. Algae do not require soil, fresh water, or land to grow. It doesn’t compete with food supplies and can actually benefit the environment with its ability to reduce GHG emissions, the culprit of global warming. But mass producing algae biodiesel has yet to be achieved as the energy return on the energy invested still runs in the red.
For algae oil to become economically feasible, the entire algae-to-oil pathway must be energy positive and environmentally sustainable. This project focused on achieving that goal by engineering equipment and designing processes to insure energetic viability. Many of the ideas and processes that were developed and tested this year are a result of three years of experimentation with each year evidencing marked improvement in the reduction of energy consumption and chemical utilization. Several results from this experiment mimic current data available in the scientific community and were repetitive from prior experiments conducted by this researcher. These include the fact that algae proliferates faster when CO₂ is present in the growing environment. A closed growing environment eliminates contamination and allows for variables such as temperature, light, and pH to be controlled. Algae biomass can be harvested through ionic flocculation, and ultrasonic waves can rupture algae’s cell walls for extraction. With these proven facts, this experiment focused on reducing energy consumption and increasing production yields in the upstream, midstream, and downstream processes involved in algae oil production.
The double walled, photoautotrophic bioreactor vessels were designed to utilize the sun’s free energy source for cultivation. By enhancing the light spectrum with neon and helium gases, a study of first impression, the filtered red-orange and blue-green light spectrums intensified the growth of biomass without the use of fuel or chemical additives. The vessels’ mechanical agitation paddles allowed for continuous rotation of the biomass, improving transmission of light waves through the solution. The 360˚ rotation of the airstone increased the solutions, absorption of CO₂ airborne and CO₂ aqueous. The vessels’ tee valves allowed for sample extraction without contaminant to the solution. The closed loop nutrient control chamber allowed for controlled infusion of CO₂ airborne and CO₂ aqueous to the biomass. By controlling CO₂ consumption, the correlation between algae’s growth and CO₂ consumption was determined. Furthermore, by controlling CO₂ levels, pH levels were manipulated to optimize lipid growth and harvesting. This engineered cultivation system resulted in an increase yield of clean biomass in a shorter time period.
The harvesting process utilizing ionic flocculation was tested by this researcher last year and resulted in a substantial floc, but there was still a residual of algae biomass that was not captured. With the goal of maintaining an energetically positive process, ionic flocculation was once again utilized, but with variations in procedures. 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. 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 wherein Na₂CO₃ was added to the biomass two weeks prior to flocculation. During this two week period, pH levels were manipulated to 8.5 by starving the algae of CO₂. 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 Fe₃O₂, 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 Fe₃ 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.
A three-fold critical cell disruption process was designed and built to perform the downstream process of fracturing the cell walls and extracting the lipids in a one-step, low energy, wet process. The current method utilized in the industry requires drying the algae biomass, treating the biomass with chemical solvents for lipid separation, cleansing the lipid for refining, and cleaning the remaining algae mass for further use as feedstock. These downstream steps are energy and economic sinkers for algae oil. By engineering the “cellulose blaster” the algae slurry is transformed into lipid oil utilizing osmotic shock, homogenization and sonication. The algae cells were lysed by 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 the high-energy costs associated with drying the biomass, chemical infusion, and solvent recovery. 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. The inspiration to build the cellulose-blaster resulted from research on the various methods of cell disruption. Many researchers have attempted to frack the cell wall using mechanical pressing, bead beating, microwave, homogenization, ultrasound, pulsed electric field, ion exchange or enzyme catalysts, but not a combination of these methods. The cellulose-blaster was designed to bombard the algae cells with several disruption methods at one time. The future goal is to conduct 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.
By refining the processes involved in algae oil production, its ability to compete with existing commodities is improving. Although the double-walled photoautotrophic bioreactor is an innovative design, there are still many variables to be tested. The input of CO₂ into the vessels needs to be controlled. Flue gas should be used rather than compressed CO₂. The medium utilized for cultivation should be tested. If the actual composition of the solution is determined, it could be manipulated for increased growth. Different strains of algae should be tested to determine the highest lipid content and optimal growing conditions. Does the species grow more efficiently in vertical, horizontal, or helical positions? The vessels should always incorporate mechanical and air agitation, but the speed of rotation should be investigated to determine how much agitation the algae could withstand before shearing occurs. Does increased rotation improve overall growth and CO₂ consumption? Further research should be conducted to determine whether the benefits of ionic flocculation outweigh the costly, but effective separation process offered by centrifugation, filtration, or flotation. Further testing should be conducted on the residual solution left from the floc to determine the percentage of uncaptured biomass. Could a different cation produce larger flocs? The creation of the cellulose-blaster to fracture the cell wall and extract the lipids is a prototype for future experiments. Can the cellulose blaster be manufactured into a single stainless steel unit for supercritical in situ method? Can extraction and transesterification be completed in one step? Overall, repetitive studies should be done to ensure consistent data. Obstacles must continue to be identified and processes refined in order to produce an economically viable green diesel alternative.
For algae oil to become economically feasible, the entire algae-to-oil pathway must be energy positive and environmentally sustainable. This project focused on achieving that goal by engineering equipment and designing processes to insure energetic viability. Many of the ideas and processes that were developed and tested this year are a result of three years of experimentation with each year evidencing marked improvement in the reduction of energy consumption and chemical utilization. Several results from this experiment mimic current data available in the scientific community and were repetitive from prior experiments conducted by this researcher. These include the fact that algae proliferates faster when CO₂ is present in the growing environment. A closed growing environment eliminates contamination and allows for variables such as temperature, light, and pH to be controlled. Algae biomass can be harvested through ionic flocculation, and ultrasonic waves can rupture algae’s cell walls for extraction. With these proven facts, this experiment focused on reducing energy consumption and increasing production yields in the upstream, midstream, and downstream processes involved in algae oil production.
The double walled, photoautotrophic bioreactor vessels were designed to utilize the sun’s free energy source for cultivation. By enhancing the light spectrum with neon and helium gases, a study of first impression, the filtered red-orange and blue-green light spectrums intensified the growth of biomass without the use of fuel or chemical additives. The vessels’ mechanical agitation paddles allowed for continuous rotation of the biomass, improving transmission of light waves through the solution. The 360˚ rotation of the airstone increased the solutions, absorption of CO₂ airborne and CO₂ aqueous. The vessels’ tee valves allowed for sample extraction without contaminant to the solution. The closed loop nutrient control chamber allowed for controlled infusion of CO₂ airborne and CO₂ aqueous to the biomass. By controlling CO₂ consumption, the correlation between algae’s growth and CO₂ consumption was determined. Furthermore, by controlling CO₂ levels, pH levels were manipulated to optimize lipid growth and harvesting. This engineered cultivation system resulted in an increase yield of clean biomass in a shorter time period.
The harvesting process utilizing ionic flocculation was tested by this researcher last year and resulted in a substantial floc, but there was still a residual of algae biomass that was not captured. With the goal of maintaining an energetically positive process, ionic flocculation was once again utilized, but with variations in procedures. 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. 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 wherein Na₂CO₃ was added to the biomass two weeks prior to flocculation. During this two week period, pH levels were manipulated to 8.5 by starving the algae of CO₂. 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 Fe₃O₂, 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 Fe₃ 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.
A three-fold critical cell disruption process was designed and built to perform the downstream process of fracturing the cell walls and extracting the lipids in a one-step, low energy, wet process. The current method utilized in the industry requires drying the algae biomass, treating the biomass with chemical solvents for lipid separation, cleansing the lipid for refining, and cleaning the remaining algae mass for further use as feedstock. These downstream steps are energy and economic sinkers for algae oil. By engineering the “cellulose blaster” the algae slurry is transformed into lipid oil utilizing osmotic shock, homogenization and sonication. The algae cells were lysed by 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 the high-energy costs associated with drying the biomass, chemical infusion, and solvent recovery. 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. The inspiration to build the cellulose-blaster resulted from research on the various methods of cell disruption. Many researchers have attempted to frack the cell wall using mechanical pressing, bead beating, microwave, homogenization, ultrasound, pulsed electric field, ion exchange or enzyme catalysts, but not a combination of these methods. The cellulose-blaster was designed to bombard the algae cells with several disruption methods at one time. The future goal is to conduct 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.
By refining the processes involved in algae oil production, its ability to compete with existing commodities is improving. Although the double-walled photoautotrophic bioreactor is an innovative design, there are still many variables to be tested. The input of CO₂ into the vessels needs to be controlled. Flue gas should be used rather than compressed CO₂. The medium utilized for cultivation should be tested. If the actual composition of the solution is determined, it could be manipulated for increased growth. Different strains of algae should be tested to determine the highest lipid content and optimal growing conditions. Does the species grow more efficiently in vertical, horizontal, or helical positions? The vessels should always incorporate mechanical and air agitation, but the speed of rotation should be investigated to determine how much agitation the algae could withstand before shearing occurs. Does increased rotation improve overall growth and CO₂ consumption? Further research should be conducted to determine whether the benefits of ionic flocculation outweigh the costly, but effective separation process offered by centrifugation, filtration, or flotation. Further testing should be conducted on the residual solution left from the floc to determine the percentage of uncaptured biomass. Could a different cation produce larger flocs? The creation of the cellulose-blaster to fracture the cell wall and extract the lipids is a prototype for future experiments. Can the cellulose blaster be manufactured into a single stainless steel unit for supercritical in situ method? Can extraction and transesterification be completed in one step? Overall, repetitive studies should be done to ensure consistent data. Obstacles must continue to be identified and processes refined in order to produce an economically viable green diesel alternative.