Algae as an Alternative Source to Transportation Fuel
Algae Biomass is being researched as a sustainable, viable and alternative renewable resource. This paper will discuss what algae biomass is, how it works, the economic impacts, its pros and cons and the future possibilities of using it widely; in this case, biodiesel to replace petroleum-based transport fuel.
Algae was the life giver of earth billions of years ago due to its photosynthesis qualities. Algae collects CO2 from the atmosphere and replaces it with oxygen. In 1978, under President Jimmy Carter, algae were explored as a fuel alternative by the Aquatic Species Program run by the National Renewable Energy Laboratory (Newman, 2018).
Microalgae are small aquatic organisms that convert sunlight into energy in the form of natural oils (Energy 101, 2012). The extracted oil provides the raw material to make fuel for any type of transportation that currently runs on gasoline or diesel. Microalgae are single celled organisms found in both saltwater and freshwater ecosystems, which makes it easily accessible and continually renewable (Demirbus, 2010).
To progress to the actual use of microalgae as an oil-based fuel replacement, three processes need to be further researched and perfected. These include finding the best type of algae, finding the best way to grow it both economically and spatially and fine tuning the extraction and refining process of the oil (Newman, 2018)
It is the oil within the microalgae, that is used to make biodiesel. Researches are attempting to find the best strain that would be most efficient within certain boundaries such as; the amount of oil that can be extracted, and, the resilience to rapid growth in different environments. Algae that may have a large amount of oil may not be versatile enough to grow in large scales (Sherry, n.d).
There are five steps in the process of turning microalgae into biodiesel. Cultivating or Growing the microalgae followed by harvesting, drying, extracting and purifying (Farag, 2001).
Microalgae can be cultivated in open or closed systems. The “raceway” is currently the most productive open pond system. It is shaped like a racetrack and fertilizer is added to the pond and mechanically mixed with a paddle wheel exciting the algae into rapid growth. A closed cultivating system; such as photobioreactors (PBR’s) are generally climate controlled, water is circulated by pumps and artificial light can be used to maintain the algae’s growth process (Singh, Nigam, & Murphy, 2011).
Either system used to cultivate the algae have positive and negative inclinations. Open pond systems are less expensive to create than PBR’s, are cheaper to maintain and can be placed in areas that do not interfere with any other land use conflicts such as crop production or agriculture; but, it has limitations, such as being site specific. To maximize the production there needs to be a lot of sunlight, so hot, dry areas are ideal. The ponds are also open to contamination from pollution or other organisms that can affect the yield of the crop (Demirbus, 2010).
PBR’s have proved to be highly productive with low results of contamination due to the controlled growth environment but the expense to start and maintain photobioreactors are still too high to make it an economically feasible to replace the current transportation fuel on a large scale (Singh, Nigam, & Murphy, 2011).
Harvesting the microalgae, or separating the biomass from its birthing area, is also being researched and developed. Harvesting depends on how the algae was cultivated and there are a wide range of techniques available, none of which are economical (Demirbus, 2010). In open pond cultivation; flocculation is commonly used. A chemical or chemicals are added to attract the algae to clump together where it can be collected in several ways. Filters can collect the clumps of algae or air bubbles can be injected to bring the clumps to the surface. A slower way to cultivate is through sedimentation where the clumps settle to the bottom (Newman, 2018).
PBR’s commonly use a filtration and centrifugation process to separate the microalgae from its growth environment. (Singh, Nigam, ; Murphy, 2011)
325945568580Open pond extraction process.
4000020000Open pond extraction process.
Harvesting costs may contribute 20 – 30 percent of the total cost of algae biomass because of the energy intensiveness in harvesting (Demirbas, 2010).
Drying or dewatering the algae is also necessary. External heat-drying, sun drying, spray-drying, shelf-drying and drum-drying are being used and tested now but are proving to be costly. There are many companies researching other techniques to improve the process of removing the water from the microalgae, and affordable techniques will have to be developed at this stage as well (Energy 101, 2012).
As discussed earlier in this research paper, the microalgae oil is what is manipulated to biodiesel by being chemically changed. As in each step of the process thus far, there are many options being tested. An oil press can be used in combination with a hexane solvent. The press extracts about 75 percent of the oil prior to the hexane being added. The oil is then filtered and cleaned removing any chemicals left over (Newman, 2018). The supercritical fluids method extracts 100 percent of the oil when carbon dioxide is mixed with the algae and is heated and pressurized leaving the oil behind (Energy 101, 2012.)
Transesterification is the process that changes the plant oil to biodiesel. An alcohol and an ester combination are mixed together. The physical characteristics of fatty acid esters are very close to those of fossil diesel fuels and when mixed with the microalgae a chemical alteration takes place changing the algae oil into biodiesel (Singh, Nigam, ; Murphy, 2011).
Even thought the current technology and knowledge of using microalgae biofuel as a future replacement for petroleum-based transportation is still being tested, I believe there could be a future in its use, especially if barriers can surpass the benefits.
Algae based biofuels are considered carbon neutral in its combustion which is a factor with current transportation fuel and CO2 emitting into the atmosphere; which, is an attribute to climate change (Singh, Nigam, ; Murphy, 2011).
There are many barriers to overcome to make the transition from oil-based petroleum to bio-based petroleum. Open system cultivation does not seem to be practical in the long-term due to the possibilities of contamination and the number of algae that will need to be cultivated to support the current demand for transportation fuel; and closed systems are not currently an economically viable solution. Researchers are still on the quest to perfect the combination of microalgae species with rapid growth rate with adaptability, harvesting and production that would economically compete with the worlds current fuel resources (Siegel, 2017).
In my opinion, the most difficult barrier to overcome is convincing the minds of the worlds population to release its reliance on oil-based petroleum. If these barriers can be overcome through research and development; and, can be proven to be a reliable and less expensive alternative, there will be microalgae-based biofuel stations in our future.
Demirbas, A. (2010). Use of algae as biofuel sources. Energy Conversion and Management,51(12), 2738-2749. doi:10.1016/j.enconman.2010.06.010
Energy 101: Algae-to-Fuel. (2012, September 5). Retrieved October 3, 2018, from https://www.energy.gov/eere/videos/energy-101-
Farag, I. (2013, October). Process diagram of producing biofuel from Algae Digital image. Retrieved September 30, 2018, from https://www.researchgate.net/figure/Process-diagram-of-producing-biodiesel-from-algae_fig1_259868136
Newman, S. (2018, June 28). How Algae Biodiesel Works. Retrieved October 2, 2018, from https://science.howstuffworks.com/environmental/green-science/algae-biodiesel1.htm
Sherry, A. M. (n.d.). How Algae can be used to produce Biofuel. Retrieved October 02, 2018, from http://www.biomara.org/schools/welcome-to-the-biomara-school-zone.html
Siegel, R. (2017, July 04). Algae-based Biofuel: Pros and Cons. Retrieved October 02, 2018, from https://www.triplepundit.com/special/energy-options/algae-based-biofuel-pros-cons/
Singh, A., Nigam, P. S., ; Murphy, J. D. (2011). Mechanism and challenges in commercialization of algal biofuels. Bioresource Technology,102(1), 26-34. doi:10.1016/j.biortech.2010.06.057
Cultivation of Algae and Photobioreactors
Slater, C. S. (2012, August). General process flow diagram of algae biodiesel production Digital image. Retrieved October 1, 2018, from https://www.researchgate.net/figure/General-process-flow-diagram-of-algae-biodiesel-production_fig1_257479214