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DESCRIPTIONAnalysis of the pros and cons of biofuels introductory concepts.
ContentsIntroduction2Benefits2Processing4Types of Biofuel Processing4Biodiesel4Bioethanol5Summary6Feasability6Aspects6Manufacturing6Transportation7Usage7Conclusion7References9Table of Figures10Appendix: Articles11
Introduction Energy, a term that is used every single day in America, a staple for the modern lifestyle has been the focus of science, national debate, and even war. The search for renewable energy has been at the frontier of science and the media in the past several decades. America and other countries are very familiar with the energy crisis. There is no doubt that natural crude oil being nonrenewable will eventually be scarce. Barrels of petrol reaching over one hundred dollars seem to be a commonality in the world at this time. As natural resources of crude oil are exhausted, it seems that a new substance must take its place to satisfy the energy needs of leading nations. Although the green initiative will likely be a combination of renewable resources, a very promising candidate in relinquishing crude oils grasp on nations is Algal Biofuels. Algal, meaning algae based, biofuels is the radical idea of producing fuels from a renewable resource, namely Algae! The same green stuff that grows on the inside of fishbowls fueling an entire nation seems ludicrous, but in reality it is more feasible than one would think. Benefits, processing, and long term feasibility of Algal biofuels will be discussed.
Benefits The benefits of using Algae as a source for energy and biofuels are numerous. Firstly, examination of the properties of Algae is important. Algae comes is part of the first level biomass. The term biomass refers to the primary producers in the energy distribution for ecosystems. These producers take advantage of sunlight by using the process we know as photosynthesis (Campbell & Reece, 2002). Algae, being a primary producer implies that it can store energy in lipids, carbohydrates, fatty acids, and storage products by using photosynthesis. In particular microalgae is one of the best primary producers for these energy rich compounds which are prerequisites in the process of making oil from Algae, it has been shown that up to 80% of the dry weight of algae biomass is organic oils (Amin, 2009). Figure 2 Green Algae numerocinqmagazine.com
Some other benefits include their photosynthetic efficiency, noncomplex organic structure, focused production types ie those that will produce more lipids than anything else-, simple reproduction and growth, farming techniques, and ease of technical production (Amin, 2009). So clearly the prospect of making Algae and using it as a stable resource seem feasible. Also it is quite simple to show that when Algae uses photosynthesis to produce organic compounds, it uses CO2 in process thereby reducing carbon based emissions (Demirbas A. , 2010). Figure 3 Photobio Glass Tube Reactor
Other benefits include the technology and the ease of farming Algae. Because microalgae can grow and thrive in a suspension this is how most common ponds and other algae cultures in nature exist cultures can take various different forms. Some structures have micro-tubes 0.1mm thick that can be bent around structures that make it easier for users to gather the algae and its products after growth and photosynthesis (Demirbas A. , 2010). This freedom in design is not only aesthetic, it can also serve as a tool to maximize certain parameters based on what kind of product the manufacturer wants. So Algae seems very user friendly when it comes to manufacturing purposes, it is good for the environment, and it is extremely efficient in comparison to other substances that can be used for biofuels. Also an obvious advantage to biofuels over other green initiative energy mechanisms is that biofuels dont require a major change to the infrastructure of how humans use energy. Most biofuels can be used in internal combustion engines for instance. If biofuels can be processed, manufactured, and transported easily then it can be a viable modern renewable energy source. Processing the biomass will be a very critical point in the feasibility of biofuels.
Processing Types of Biofuel Processing Some of the benefits of Algae were discussed, now the focus is on the processing of microalgae to produce biofuels. Energy initiatives around the world are interested in producing fuel for cheap, so exploring the parameters in manufacturing biofuels is essential to the feasibility of biofuels as an alternative resource. Algae being a first level producer doesnt just turn into oil. Producing and Refining Biofuel can be an extensive process but also rewarding. There are two general methods to convert microalgae to useable forms of energy, there are biochemical processes and thermochemical process. The biochemical sector will produce biodiesel and ethanol, whereas the thermochemical sector will produce oil and gas. The processes in each sector are as follows. Thermochemical: Gasification, Liquefaction, Pyrolysis, and Hydrogenation. Biochemical: Fermentation and Transesterification (Amin, 2009). The discussion will be limited to the biochemical processes because the focus is biofuels. The goal is to find out how much time and energy is needed to make these biofuels the energy investment for the return. Biodiesel and transesterification will be discussed first, and ethanol with fermentation second. Biodiesel Studies have shown that to produce biodiesel, lipids must be extracted. Even though the biodiesel is biodegradable and nontoxic producing low sulfates and carbon emissions-, the extraction of lipids is quite difficult because the algal cells have thicker cell walls. Mechanical pressing and grinding is insufficient, thus biochemicals must be used for lipid extraction. Chemicals such as methanol, chloroform, hexane, and isopropanol must be used to effectively extract the lipids, and different algae strains greatly effect the percent yield (Lam & Lee, 2014). Clearly, there is a lot of parameters that go into lipid extraction. According to another source certain strains can be extracted through oil presses, osmotic shock, and supercritical fluids (Amin, 2009).Once the lipids have been extracted from the biomass of the algae, it is ready for transesterification. As the name might suggest, the process involves ester groups. The addition of several different types of acids and bases that act as a catalyst in esterification. To increase the yield of this process transesterification is executed in situ, the algal biomass is in direct contact to ensure maximum surface area exposure and chemical reactivity (Lam & Lee, 2014). One study was able to take the Algal Strain Chlorella and use in situ transesterification to obtain a yield of 90% at 60 with a methanol to lipid molar ratio of 315:1 H2SO4 of 0.04mol and a reaction time of only four hours (Ehimen, Sun, & Carrington, 2010). The punch line however is that it is a high percent yield, but notice the molar ratio of methanol to lipids. So there is obviously some investment in reactants. In the same study (Ehimen, Sun, & Carrington, 2010), a yield of 95% was obtained when an algal strain of Chlorella pyrenoidosa was used in in situ transesterification with a cosolvent of hexane, the methanol to lipid molar ratio was significantly reduced to 165:1. Bottom line is that transesterification techniques can be improved and hopefully become entirely independent of petrol derived reactants, but this will be discussed in more detail in the feasibility section. The next main algal biofuel is bioethanol. Bioethanol Bioethanol is produced via the process of fermentation. Just as alcohols are produced, the same reactants are needed, that is a sugar, starch, or cellulose with the combination of yeast to fuel the fermentation process. Any strain of microalgae that has a high percentage of carbohydrates can be used in the bioethanol process, some include: Chlamyfomanas renhardtii, C. Reinhardtii, Chlorella Vulgaris, Chlorella sp. And Scenedesmus sp (Lam & Lee, 2014). Thus there are plenty of strains of algae that are suitable for bioethanol production. The process is very similar to the production of all other alcohols, a flow diagram of the process is shown below.Microalgaes starch is released via mechanical action or enzymes, Saccharomycess cereviasiae yeast is then added to produce alcohol groups, in this case ethanol. The ethanol must be extracted from the mixture once the process is complete; therefore large distillation tanks are used for this process. Some by products include acetate, hydrogen, and carbon dioxide (Amin, 2009). Figure 4 Fermantation process of microalgae (Amin, 2009)
So the process to produce ethanol is elementary; however the yields are quite different than biodiesel. The table below is taken from (Lam & Lee, 2014):The table shows how the ethanol yield to substrate ration varies dramatically among the different strains of algae used for feedstock. Each with a different pretreatment. So even though the process to produce ethanol may be more simplistic than biodiesel, the yields are clearly lower, and one must question the pretreatments of the material as well. Clearly there is a lot of parameter space in the processing of bioethanol. Figure 5 Different Fermentation Processes based on Feedstock and Percent Yields (Lam & Lee, 2014)
SummaryThe processes that produce biodiesel and bioethanol is transesterification and fermentation. Both processes are not conceptually challenging, and have a large parameter space to experiment with. It seems that biodiesels can produce a higher percent yield than ethanol but that might be at the cost of using more petrol based reactants. Nonetheless it seems that there is hope for the processes. It should be mentioned that using Algae as a biomass to refine reactants is just as dynamic as refining oil. There are many products that