With the substantial amount of research conducted regarding climate change, it is widely believed that the burning of fossil fuels, deforestation, and other human activities are adding a significant amount of greenhouse gases to the atmosphere. These greenhouse gases include carbon dioxide, methane, chlorofluorocarbons, and nitrous oxide. It is furthermore believed that this is enhancing the greenhouse effect, leading to a gradual warming of the Earth’s surface. It is essential that these gases emitted from human activity be constrained in order to avoid exacerbating the warming of the Earth. The effects of climate change are multifarious. It is a direct threat to human health. It could lead to rising sea levels, agricultural, forestry, and ecosystem disruption, and an increase in the spread of tropical diseases. Climate change is predicted to bring about intense heat waves as well as violent that storms will occur with more frequency and with more destructiveness. The potential of such devastating impacts on a global scale make climate change one of the most consequential environmental challenges we must deal with.
As the price for petroleum continues to rise and the demand for it increases exponentially, biofuels are steadily gaining more ground as one possible alternative to our current unsustainable means of transportation. Hydrogen, ethanol, and biodiesel are at the center of research seeking to find an alternative, cleaner source of fuel to power our economy.
These fuels are appealing because of their renewability and in most cases, their cleaner emissions. The United States spends $100 to $150 billion each year importing petroleum from predominantly unstable political economies (Briggs 1). Developing domestic alternatives to petroleum will lessen the economic strain of importation and increase the level of national security. Biodiesel, derived from vegetable oils and animal fats is, at the moment, considered by many to be the best alternative to oil. It can be used to power all diesel engines and no conversions are needed for this to work, making it an ideal subject for further research. Biodiesel emits far lower levels of particulate matter, carbon-di-oxide, carcinogens, air toxins, and sulfur oxides as compared to petroleum diesel (Sheehan 7).
Among the most cost and space effective options for a renewable biofuel source are microalgae. As a result of their simple molecular structure, microalgae are the most photosynthetically efficient organisms on the planet and it is because of this that they are also the fastest growing (Sheehan 9). Every few days, microalgae complete an entire growth cycle. Certain algal strains can consist of hydrocarbons that make up 75% of their dry mass and therefore provide significantly higher yields of oil than terrestrial oilseeds (Banerjee 246). Microalgae are able to produce 5,000-15,000 gallons of oil per acre per year whereas corn is only able to produce 18 gallons (Riesing 1).
Another advantage algae have over other terrestrial biomass sources is that they do not have to compete for land with agriculture in the way corn and soybeans do. Michael Briggs, a physicist at the University of New Hampshire, estimates that roughly 15,000 square acres filled with open-air raceway systems designed for the purpose of algal cultivation would produce enough oil to fuel all ground transport vehicles in the United States of America (Briggs 4). Microalgae, which grow in aqueous suspension, are also more efficient at utilizing available resources (Sheehan 9). Because of the immense variety of algae and the diversity therein, it can be grown in a wide geographical spectrum including the deserts of New Mexico, the brackish swamps of Louisiana, and the mountains of Southern Appalachia.
Algal growth is dependent on three crucial ingredients: sunlight, carbon-di-oxide, and water. With these three ingredients present, algae will bloom in lakes, streams, and ponds. However, since these bodies of water are exposed to various elements of the earth, they are extremely susceptible to several forms of contamination such as invasive algal species and harmful bacteria (Cultivation of Algae Strains for Biodiesel, http://www.oilgae.com/algae/oil/biod/cult/cult.html ). Additionally, the strains of algae with the highest oil contents reproduce at a rate much slower than that of the less desirable ones. The species with the faster reproductive rates will eventually starve the oil producing strains of its necessary nutrients, thereby eliminating them the body of water. As a result of these problems, very few algal species have been successfully cultivated outdoors (Cultivation of Algae Strains for Biodiesel).
Despite these glaring problematic possibilities, open-air systems remain the primary means for microalgal biomass production on a mass commercial scale. This is largely due to the cost-effectiveness of such systems, not their effectiveness. In these commercial productions, the cultivators typically grow microalgae in a shallow raceway pond. In this design, a paddlewheel continually circulates the microalgae, water, and nutrients around a raceway track, suspending the species at the surface of the water so that it may receive optimal irradiance levels (Sheehan 4). These shallow raceway ponds are designed so that a source of carbon-di-oxide can be poured in and efficiently utilized by the microalgae (4). Algae are captured and removed at the end of the raceway by various forms of harvesting systems.
There are numerous sources for waste carbon-di-oxide; essentially, anything that combusts fuel for energy could be utilized. Algalculture farms could be potentially used as a means of carbon sequestration. Early researchers of the field envisioned farms that could be designed to capture the carbon-di-oxide emitted from industrial gaseous waste streams and utilize it to enhance growth (Hase 157). The gas stacks of coal and other fossil fuel powered plants produce emissions comprised of 13% carbon-di-oxide and such high concentrations would greatly enhance microalgal growth (Sheehan 4). Pairing an algalculture farm with power plants would be an excellent way to divert emissions that would otherwise be harmful and convert them into a usable liquid fuel.
However, the majority of algalculture farms are not yet at this point and many experience difficulties in providing the microalgae with sufficient levels of carbon-di-oxide. As a result of the short absorbing path of carbon-di-oxide, these farms use organic substances such as acetic acid and carbonate as the primary source (Hase 157). These substitutes limit the overall productive efficiency, lowering total yields and slowing the algae’s growth period. This problem is further exacerbated by the farmers’ inability to control water temperature and irradiance levels. Open-air farms, therefore, have a limited growing season.
Several solutions have been devised to increase the efficiency of these open-air raceway culture systems. Some designs that are currently at the center of research are tubular reactors, flat plate reactors, fermenter-type reactors, and air-lift reactors. The most suitable and practical design of an algalculture system is largely dependent on location, the particular strain, and the purpose of growing that strain. As aquaculture researchers Carvalho, Meireles, and Malcata say, “Despite several research efforts developed to date, there is no such thing as “the best reactor system”- defined, in an absolute fashion, as the one able to achieve maximum productivity with minimum operation costs, irrespective of the biological and chemical system at stake” (Carvahlo et. al 2006).
The alternative that I chose for my system is a scaled-down variation of a raceway system enclosed by a greenhouse. This was by far the most cost-effective option and compared to other feasible ones, I believed it would prove to be the most efficient. The greenhouse will drastically reduce the risk of contaminating sources that could potentially invade the microalgae. The culture medium will be protected against large fluctuations of temperatures that could, if occurring at frequent enough intervals, kill the medium. The greenhouse will also provide a more constant water temperature which will enhance the growth process. Instead of the water snaking through a raceway track, as occurs in most raceway systems, the water is instead circulated around a series of three baffles. This is done to ensure the even distribution of nutrients and carbon-di-oxide amongst the microalgae. There is no harvesting system built in and instead the algae must be collected by means of a sterilized fish net.
The tank was constructed to the dimensions of 8′x2′x2′. In retrospect, the height of this tank is perhaps a bit too high and a shorter height of 1′ would have been more than sufficient. I believe that this height will block out slightly more sunlight than is desired but that will be determined. Since the distance that sunlight is able to penetrate water is very limited, the surface area of the tank is far more important than its volume capacity. The total surface area of the tank is 16 square feet. If optimal growing conditions are sustained, each square foot will produce 4 pounds of algae per year for a total of 64 pounds (Riesling 2).
The tank is mainly constructed of oriented strand board which was selected over plywood because of the much lower levels of formaldehyde emissions, which I saw as a potential source of contamination. I first cut the OSB lengthwise, leaving me two 8′x2′ pieces. I then cut the other board into two 2′x2′ pieces. I placed the 2′x2′ board on the inside corner of one of the 8′x2′ pieces and connected them with small tacking nails. The same thing was done to the other side. The other 8′x2′ board was then tacked to the open edges of both 2′x2′s.
Connecting 2x4s on the base, the top, and on all eight corners supported this structure. I placed a 2x4x8 lengthwise on the bottom. This was screwed to a 2x4 with the length cut down to 2′3″. The short 2x4 was then screwed to another 2x4x8 on the other lengthwise side. The base was completed by screwing a board with the same dimensions as its opposite side to both lengthwise 2x4s. This same procedure was then repeated for the top of the structure with one minor difference. A 1″ gap was placed on the short side to allow the entry of electrical cords into the tank. I cut the remaining 2x4s into eight pieces, each with a length of 1′5″. These were vertically placed in between the 2x4s on the top and bottom of each corner and screwed securely together. As an additional safety measure to ensure that the tank would not blow out due to the pressure of the water, I later braced the tank with six stud plate ties, three on the top and three on the bottom.
The next step I took was lining the tank with 6 millimeter plastic. It is essential to avoid making the lining too taut. If the plastic lining is pulled too tight, it is likely that the weight of the water will pull the plastic and detach it from the structure. The lining was secured by nailing 1x4s on top of the plastic on the top rim of the tank. Each 1x4s width was trimmed down to 2⅝″ so that it would fit plush with the top rim. A one inch gap in the 1x4 was placed directly above the gap in the 2x4. The excess plastic was carefully removed with a razorblade.
After the structure of the tank was sturdy, secure, and lined with plastic, I created a baffle system that would aide in the circulation of the microalgae. This was done by securing three small sheets of corrugated metal roofing, each measuring 2′x 20″, to two 1x4x6s attached to the top and bottom of the north inner wall. This baffle system was fully constructed before placing it inside of the tank. Five inches from the edge of each 1x4, slices were made in the wood. 1′6″ from those slices, two more were made. These four cuts, two on the top 1x4 and two on the bottom one, would hold the first baffle. After a small gap of 5″, slices were made 1′6″ apart from each other on both 1x4s. This last step was then repeated. Each metal sheet was placed into their respective cuts so they would protrude into the tank and direct the flow of water. This was placed on the north side of the tank in order to leave the algae exposed to the more direct southern sunlight. Each sheet was scrubbed with hypochlorite to reduce the risk of potential contamination.
The last step in the building process was the construction of the greenhouse. This was done using three main materials: 1x4s, 6 millimeter thick plastic, and wood trim. The greenhouse is designed so that it fits tightly around the top rim of the tank. For this to happen, I had to first surround the outer perimeter of the tank with 1x4s, split in half lengthwise, two inches below the top rim. The base of the greenhouse was built by first determining what length the 1x4 needed to be cut to in order to tightly fit on top of the tank. After determining it to be 8′⅜″ on the north and south sides and 2⅝″ on the east and west sides, I cut the 1x4s accordingly. The boards were placed horizontally upright and fastened together with metal plates. I then cut the 1x4s to form ten pieces that would be used to brace the roof, each with the length of 2′. One piece was fastened to each of the base’s outside corner and the remaining two were placed directly in the center of the north and south sides. These two center pieces were connected at the bottom by another 1x4 that was secured to the top of the horizontally upright base. I then nailed the two remaining halves of the 1x4s I had split earlier to the top of each vertically upright 1x4. It was essential that they were halved in order to connect the northern east and west corners to the southern east and west corners via another 1x4. I then nailed the last of the 1x4s to the bottom of the base to fill in the gaps between the vertical supports so that the plastic for the greenhouse would be taut and air tight. The plastic was draped over the structure, pulled tight, and stapled to the 1x4s.
The growth of microalgae in a closed system cannot successfully occur without purified, contaminant free water (Venkataraman 11). The ideal source for pollutant free water is offshore open ocean water because of the low levels of nutrients and trace metals that it contains (Andersen 24). However, since water of this type is in my situation too difficult to obtain, my source of water is derived from a deep well. Well water, while still containing varying degrees of impurities, is a cleaner source than tap water which contains relatively high levels of chlorine that would prove deadly for most species of algae.
There are several methods that can be used to sterilize water. The most practical method in my particular scenario, considering the large volume of water in need of sterilization, is sodium hypochlorite. This is the predominant sterilization technique used in aquaculture hatcheries (Andersen 72). Depending on the source of water, between 1 and 5 milliliters of sodium hypochlorite is added per liter of water (73). Prior to sterilizing the water, I covered both the top rim of the tank and the bottom of the greenhouse with aluminum foil to prevent any recontamination from occurring once I placed the greenhouse back on. My algalculture tank contains 226.5 liters of water; therefore I added 226,500 milliliters of commercial bleach to the body of water. Since direct sunlight during the sterilization process will drastically reduce the procedures overall effectiveness, I added the bleach slightly before nightfall. I then slowly stirred the water to evenly distribute the bleach, enclosed the tank with the greenhouse, and let the mixture stand for several hours.
The last step in the sterilization process is adding sodium thiosulfate to the water. This is done in order to neutralize the solution. If it is not neutralized, the presence of bleach in the water will destroy all liquid pH indicators, making it impossible to test for pH levels (Andersen 73). Per every 4 milliliters of bleach added, 1 milliliter of sodium thiosulphate must also be added (73). I therefore added a total of 56,625 milliliters of sodium phosphate to the body of water. The water is now pure and the pH level of it can regularly be checked.
The specific species of algae that will be at the center of my experimental research is Botryococcus braunii. Botryococcus braunii, a green algae, is a member of the class chlorophyceae. B. braunii is distinguished for its ability to produce substantial amounts of hydrocarbons and other chemicals (Metzger 486). Of all known species, it has the ability to produce the most significant amounts of hydrocarbons (Benerjee 246). Considering the end result of my algal cultivation is the production of biodiesel, B. braunii is the optimal species for the experiment.
B. braunii, which blooms in both fresh and brackish water, can be found in the waters of all seven continents (Benerjee 246). There are a total of three distinctly separate races of B. braunii that have been acknowledged. Each species is differentiated from one another by the type and amount of hydrocarbons that they produce as well as their physiological characteristics. The races A and B have been found blooming in lakes located in the alpines, the tropics, temperate, and continental regions, while race L has only been found growing in tropical bodies of water (Metzger 488). The dry weight of race A can be composed of hydrocarbons ranging anywhere from 0.4% to 61.0%, by far the largest possible variation of oil content of all B. braunii races (488). Race B is more consistent in its hydrocarbon production and generally is composed of 30% to 40% hydrocarbons (488). Race L is not a desirable species to cultivate as a fuel source seeing as the highest hydrocarbon content recorded is only 8% (488).
It is reported that B. braunii are able to utilize 3% of the solar energy they receive and transform it into hydrocarbons (489). When these hydrocarbons are burned, they do not add any carbon-di-oxide to the atmosphere. If a 100-MW thermal power plant burned liquid fuel derived from this species of algae instead of coal, carbon-di-oxide emissions would be reduced by 1.5x10^5 tons per year (Benerjee 24).
B. braunii have a relatively slow growth rate in comparison to most other species which is not a result of their inefficiency but rather it is a “result of the substantial commitment by the cells to producing energetically expensive hydrocarbons” (Benerjee 266). B. braunii grow best under a pH of 7.5. As of now, the pH of the water in the algalculture tank is 7.6. This will be adjusted prior to inoculating the microalgae into the medium.
I have incorporated a water pump into the tank that will aerate carbon-di-oxide in order to shorten the doubling time of the culture. Very low levels of nitrate salt will be added to the culture to increase the rate of reproduction. If the level of nitrate in the water is too high, hydrocarbon production will slow drastically. Another essential nutrient for B. braunii is phosphorous which will be added at levels much higher than that of nitrate because it has been reported that excess levels of phosphate substantially increase the amount of hydrocarbons (Benerjee 267).
I have not yet been able to begin experiments with B. braunii as I had hoped. The optimal temperature for this species is 78 degrees Fahrenheit, a temperature range that has not yet been sustained for any length of time this spring. The late winter has delayed the scientific process. The species is currently being cultured in a laboratory and is ready to be inoculated into the small-scale closed raceway reactor as soon as the weather cooperates.
Small-scale algalculture systems have enormous potential in producing clean and renewable sources of fuel. Not only are these systems easily constructed, they can also be built at surprisingly low costs. Different system designs could be used in different geographical areas, with different species of algae being cultivated. If only a small fraction of people in this country cultivated algae in their backyards or in their basements, the levels of carbon-di-oxide emissions would be far lower and we would be one step closer from freeing ourselves from our dependence on unstable political economies.
Thursday, April 19, 2007
Thursday, April 5, 2007
rough rough incomplete first draft
With the substantial amount of research conducted regarding climate change, it is widely believed that the burning of fossil fuels, deforestation, and other human activities are adding a significant amount of greenhouse gases to the atmosphere. These greenhouse gases include carbon dioxide, methane, chlorofluorocarbons, and nitrous oxide. It is furthermore believed that this is enhancing the greenhouse effect, leading to a gradual warming of the Earth’s surface. It is essential that these gases emitted from human activity be constrained in order to avoid exacerbating the warming of the Earth.
The effects of climate change are multifarious. It is a direct threat to human health. It could lead to rising sea levels, agricultural, forestry, and ecosystem disruption, and an increase in the spread of tropical diseases. It will bring intense heat waves and violent storms will occur with more frequency and with more destructiveness. These effects are not expected to be uniform. The potential of such devastating impacts on a global scale make climate change one of the most consequential environmental challenges we must deal with.
As the price for petroleum continues to rise and the demand for it increases exponentially, biofuels are steadily gaining more ground as a possible alternative to our current unsustainable means of transportation. Hydrogen, ethanol, and biodiesel are at the center of research seeking to find an alternative source of fuel to power our economy. These fuels are appealing because of their renewability and in most cases, their cleaner emissions. Biodiesel, made from vegetable oils and animal fats, is at the moment, considered by many to be the best alternative to oil.
Among the most cost and space effective options for a renewable biofuel source are microalgae. As a result of their simple molecular structure, microalgae are the most photosynthetically efficient organisms on the planet and it is because of this that they are also the fastest growing organisms. Every few days, microalgae complete an entire growth cycle. Certain algal strains can consist of hydrocarbons that make up 75% of their dry mass and therefore provide significantly higher yields of oil than terrestrial oilseeds (Banerjee 246). These hydrocarbons can be converted into petrol, diesel, and turbine fuel. Another advantage algae have over other terrestrial biomass sources is that they do not have to compete for land with agriculture. Because of the immense variety of algae and the diversity therein, it can be grown in a wide geographical spectrum.
There are three crucial ingredients for algal growth: sunlight, carbon-di-oxide, and water. If these three criteria are met, algae can be cultivated from lakes, streams, and ponds. However, since these bodies of water are exposed to the elements, they are extremely susceptible to various forms of contamination such as other species of algae and harmful bacteria. Additionally, the strains of algae with the highest oil contents reproduce at a rate much slower than that of the less desirable ones. The faster reproductive rates of those species will eventually starve the oil producing strains of its necessary nutrients. As a result of these problems, very few algal species have been successfully cultivated outdoors (http://www.oilgae.com/algae/oil/biod/cult/cult.html)
Despite this, open-air systems remain the primary means for microalgal biomass production on a mass commercial scale. This is largely due to the cost-effectiveness of such systems. In these commercial productions, the cultivators typically use a shallow raceway pond. In this design, a paddlewheel continually circulates the microalgae around a raceway track, suspending the species at the surface of the water so that it may receive optimal irradiance levels. These shallow raceway ponds are designed so that a source of carbon-di-oxide can be poured in and efficiently captured by the microalgae.
There are numerous sources for waste carbon-di-oxide; essentially, anything that combusts fuel for energy could be used. Algalculture farms could be potentially used as a means of carbon sequestration. Early researchers of the field envisioned farms that could be designed to capture the carbon-di-oxide emitted from industrial gaseous waste streams and utilize it to enhance growth (Hase 157). The gas stacks of coal and other fossil fuel powered plants produce emissions comprised of 13% carbon-di-oxide. Pairing an algalculture farm with power plants would be an excellent way to divert emissions that would otherwise be harmful and convert them into a usable liquid fuel.
However, the majority of algalculture farms are not yet at this point and many experience difficulties in providing the microalgae with sufficient levels of carbon-di-oxide. Because of the short absorbing path of carbon-di-oxide, these farms use organic substances such as acetic acid and carbonate as the primary source (Hase 157). These substitutes limit the overall productive efficiency, lowering total yields and slowing the algae’s growth period. This problem is further exacerbated by the farmers’ inability to control water temperature and irradiance levels. Open-air farms, therefore, have a limited growing season.
Several solutions have been devised to increase the efficiency of these open-air raceway culture systems. The alternative that I chose for my system is a scaled down raceway system that is enclosed by a greenhouse. This will drastically reduce the risk of contaminating sources invading the microalgae. It will allow me to have greater control over the culture medium than one would have in an open pond.
Before beginning construction, I designed several potential tanks. After deliberating as to which design would be most efficient as well as cost-effective, I decided on a tank with the dimensions of 8 ft. x 2 ft. x 2 ft. In retrospect, the height of this tank is perhaps a bit too high and shorter height of 1-11/2 ft. would have been sufficient. I believe that the larger height blocks out slightly more sunlight than is desired but that will be determined.
The tank is mainly constructed of oriented strand board which was selected over plywood because of the much lower levels of formaldehyde emissions, which I saw as a potential source of contamination. The OSB is supported by 2x4’s on the base, the top, and on all eight corners. As an additional safety measure to ensure that the tank would not blow out due to the pressure of the water, I braced the tank with six iron bridge connectors, three on the top and three on the bottom.
Prior to this, however, I first lined the tank with painter’s plastic. This was secured by nailing 1x4’s on top of the plastic on the top rim of the tank. The excess plastic was then removed with a razor.
The next step was to create a baffle system inside of the tank that would aide in the circulation of the microalgae. This was done by securing three small sheets of metal sheathing to 2 1x4’s attached to the north inner wall. Each sheet was scrubbed with hypochlorite to reduce the risk of potential contamination. See diagram 1.0 for details.
Solar heat gain……………..
Details of the greenhouse…………..
Pump system…….
Filling water and purifying……
Algae selection and uses…..
Experimental data……
Conclusion………….
The effects of climate change are multifarious. It is a direct threat to human health. It could lead to rising sea levels, agricultural, forestry, and ecosystem disruption, and an increase in the spread of tropical diseases. It will bring intense heat waves and violent storms will occur with more frequency and with more destructiveness. These effects are not expected to be uniform. The potential of such devastating impacts on a global scale make climate change one of the most consequential environmental challenges we must deal with.
As the price for petroleum continues to rise and the demand for it increases exponentially, biofuels are steadily gaining more ground as a possible alternative to our current unsustainable means of transportation. Hydrogen, ethanol, and biodiesel are at the center of research seeking to find an alternative source of fuel to power our economy. These fuels are appealing because of their renewability and in most cases, their cleaner emissions. Biodiesel, made from vegetable oils and animal fats, is at the moment, considered by many to be the best alternative to oil.
Among the most cost and space effective options for a renewable biofuel source are microalgae. As a result of their simple molecular structure, microalgae are the most photosynthetically efficient organisms on the planet and it is because of this that they are also the fastest growing organisms. Every few days, microalgae complete an entire growth cycle. Certain algal strains can consist of hydrocarbons that make up 75% of their dry mass and therefore provide significantly higher yields of oil than terrestrial oilseeds (Banerjee 246). These hydrocarbons can be converted into petrol, diesel, and turbine fuel. Another advantage algae have over other terrestrial biomass sources is that they do not have to compete for land with agriculture. Because of the immense variety of algae and the diversity therein, it can be grown in a wide geographical spectrum.
There are three crucial ingredients for algal growth: sunlight, carbon-di-oxide, and water. If these three criteria are met, algae can be cultivated from lakes, streams, and ponds. However, since these bodies of water are exposed to the elements, they are extremely susceptible to various forms of contamination such as other species of algae and harmful bacteria. Additionally, the strains of algae with the highest oil contents reproduce at a rate much slower than that of the less desirable ones. The faster reproductive rates of those species will eventually starve the oil producing strains of its necessary nutrients. As a result of these problems, very few algal species have been successfully cultivated outdoors (http://www.oilgae.com/algae/oil/biod/cult/cult.html)
Despite this, open-air systems remain the primary means for microalgal biomass production on a mass commercial scale. This is largely due to the cost-effectiveness of such systems. In these commercial productions, the cultivators typically use a shallow raceway pond. In this design, a paddlewheel continually circulates the microalgae around a raceway track, suspending the species at the surface of the water so that it may receive optimal irradiance levels. These shallow raceway ponds are designed so that a source of carbon-di-oxide can be poured in and efficiently captured by the microalgae.
There are numerous sources for waste carbon-di-oxide; essentially, anything that combusts fuel for energy could be used. Algalculture farms could be potentially used as a means of carbon sequestration. Early researchers of the field envisioned farms that could be designed to capture the carbon-di-oxide emitted from industrial gaseous waste streams and utilize it to enhance growth (Hase 157). The gas stacks of coal and other fossil fuel powered plants produce emissions comprised of 13% carbon-di-oxide. Pairing an algalculture farm with power plants would be an excellent way to divert emissions that would otherwise be harmful and convert them into a usable liquid fuel.
However, the majority of algalculture farms are not yet at this point and many experience difficulties in providing the microalgae with sufficient levels of carbon-di-oxide. Because of the short absorbing path of carbon-di-oxide, these farms use organic substances such as acetic acid and carbonate as the primary source (Hase 157). These substitutes limit the overall productive efficiency, lowering total yields and slowing the algae’s growth period. This problem is further exacerbated by the farmers’ inability to control water temperature and irradiance levels. Open-air farms, therefore, have a limited growing season.
Several solutions have been devised to increase the efficiency of these open-air raceway culture systems. The alternative that I chose for my system is a scaled down raceway system that is enclosed by a greenhouse. This will drastically reduce the risk of contaminating sources invading the microalgae. It will allow me to have greater control over the culture medium than one would have in an open pond.
Before beginning construction, I designed several potential tanks. After deliberating as to which design would be most efficient as well as cost-effective, I decided on a tank with the dimensions of 8 ft. x 2 ft. x 2 ft. In retrospect, the height of this tank is perhaps a bit too high and shorter height of 1-11/2 ft. would have been sufficient. I believe that the larger height blocks out slightly more sunlight than is desired but that will be determined.
The tank is mainly constructed of oriented strand board which was selected over plywood because of the much lower levels of formaldehyde emissions, which I saw as a potential source of contamination. The OSB is supported by 2x4’s on the base, the top, and on all eight corners. As an additional safety measure to ensure that the tank would not blow out due to the pressure of the water, I braced the tank with six iron bridge connectors, three on the top and three on the bottom.
Prior to this, however, I first lined the tank with painter’s plastic. This was secured by nailing 1x4’s on top of the plastic on the top rim of the tank. The excess plastic was then removed with a razor.
The next step was to create a baffle system inside of the tank that would aide in the circulation of the microalgae. This was done by securing three small sheets of metal sheathing to 2 1x4’s attached to the north inner wall. Each sheet was scrubbed with hypochlorite to reduce the risk of potential contamination. See diagram 1.0 for details.
Solar heat gain……………..
Details of the greenhouse…………..
Pump system…….
Filling water and purifying……
Algae selection and uses…..
Experimental data……
Conclusion………….
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