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Algal Biofuels
An introduction to Algae based renewable energy
AbstractA synopsis of the state of biofuels is examined. The benefits, processing, and long term
feasibility of biodiesel and bioethanol are discussed.
Figure 1 Farming Algae www.energytrendsinsider.com
CONTENTSIntroduction...................................................................................................................................2
Benefits..........................................................................................................................................2
Processing......................................................................................................................................4
Types of Biofuel Processing.......................................................................................................4
Biodiesel.................................................................................................................................... 4
Bioethanol................................................................................................................................. 5
Summary....................................................................................................................................6
Feasability......................................................................................................................................6
Aspects...................................................................................................................................... 6
Manufacturing...........................................................................................................................6
Transportation...........................................................................................................................7
Usage......................................................................................................................................... 7
Conclusion..................................................................................................................................... 7
References..................................................................................................................................... 9
Table of Figures............................................................................................................................10
Appendix: Articles........................................................................................................................11
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 oil’s 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).
Some other benefits include their photosynthetic efficiency, noncomplex organic structure, focused production types – ie those that will produce more lipids than anything else-,
Figure 2 Green Algae numerocinqmagazine.com
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).
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 don’t 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.
Figure 3 Photobio Glass Tube Reactor
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 doesn’t 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.
Microalgae’s 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).
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):
Figure 4 Fermantation process of microalgae (Amin, 2009)
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.
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 can be derived from Algae.
FEASABILITY Aspects
So benefits of using algae, and processing algae have been discussed, and it has been shown that there are promising aspects to using algae to make biofuels. However, some studies don’t analyze the full feasibility of scientific concepts. Some main topics that would affect algal biofuel feasibility are manufacturing, transportation, and usage.
ManufacturingProcessing of biofuels has been discussed, but not their analytics. Costs estimates for
producing algae in favorable conditions for biodiesel are $2.95/kg and $3.80/kg for photo bioreactors and raceways, but if the capacity was grossly increased to an annual capacity of 10,000 tons the price can be reduced to $0.47/kg and $0.60/kg. Further analytics show that advances in reactions that produce biodiesel and even genetics can even further the yield of biodiesel (Chisti, 2007).
Figure 5 Different Fermentation Processes based on Feedstock and Percent Yields (Lam & Lee, 2014)
The brief analysis shows that biofuel production might be favorable! However a closer study examines the problem with processing fossil fuels. A metric that is common in energy analytics is the Energy Return On Investment (EROI) that is a simple ratio of energy output to input – obviously it needs to be greater than one for anything to make sense as an energy production mechanism. However, for Algal fuels, the common metric that is discussed is not the total EROI but the EROIfossil ratio which is the energy ratio of energy output to biofuel’s share of nonrenewable energy. This ratio shows that under current technology algal biofuels are depended on nonrenewable resources – the very thing that biofuels are supposed to replace! The EROIfossil ratio ranges from 0.26 to 1.20 with the current techniques, but the larger the number the better because more energy per unit fossil fuel would be obtained (Zaimes &Khanna, 2013). This number should be increased dramatically when further investigation in manufacturing is done.
TransportationThe ease of transportation is rather obvious. The fact that biofuels are liquid fuels make
it very easy to transport and use. For example, hydrogen must be converted into liquid or pumped into an engine in a gaseous state to burn, which isn’t only a trouble for transportation – because gases require more attention and careful engineering to transport – but also for safety concerns. Biofuels having a similar heat of vaporization to gasoline which is safer than having liquid hydrogen in engines and gas tanks for instance.
UsageBiodiesel and bioethanol seem very promising candidates, but it still comes down to the
consumer of the product. A large part of the feasibility of biofuels comes from the fact that implementation is so easy. Unlike other resources that require new methods to implement into current infrastructures, biofuels can indeed be used in internal combustion engines. However a consequence of this benefit is production of more greenhouse gasses – which is also on the environmentalist’s watch. These greenhouse gas emissions not only include usage, but also manufacturing. The whole life cycle from cultivation to burning it for fuel goes into greenhouse gas calculations (Scarlat & Dallemand, 2010).
Figure 7 Microalgae biofuel production chain and examined production pathways (Zaimes & Khanna, 2013)
CONCLUSION The oil and energy crisis has been in the spotlight for a while, and there has been
multiple developments to reduce dependence on nonrenewable energy. Algal biofuels were examined, their benefits, processing, and feasibility as an alternative resource. Bioethanol and biodiesel are the most common fuels produced currently, and many new developments in the field have increased the throughput and yield of such fuels. Nonetheless, even with new developments, several procedures involved in production include dependence on fossil fuels. Also the burning of biodiesel and bioethanol still release greenhouse gases and therefore raise CO2 and other harmful emissions. Even though the prospects may be doubtful, the industry of biofuels is really juvenile. Mitigating dependency on nonrenewable resources is the main objective of algal fuels and the potential for growth in the realm of biofuels is certainly evident.
REFERENCESAmin, S. (2009, March 8). Review on biofuel oil and gas production processes from microalgae.
Energy Conversion and Management.
Campbell, & Reece. (2002). Biology (Sixth ed.). Benjamin Cummings.
Chisti, Y. (2007). Biodiesel from Microalgae. Biotechnology Advances 25 , 294-306.
Demirbas, A. (2010, December). Use of Algae as Biofuel Sources. Energy Conversion and Management, 51(12), 2738-2749.
Demirbas, M. F. (2011). Biofuels from algae for sustainable development. In Applied Energy (Vol. 88, pp. 3473-3480). ELSEVIER.
Ehimen, E., Sun, Z., & Carrington, C. G. (2010). Variables affecting the in situ transesterification of microalgae lipids. Fuel, 677-684.
Lam, M. K., & Lee, K. T. (2014). Scale-Up and Commercialization of Algal Cultivation and Biofuel Production. In Biofuels from Algae (pp. 261-286). Elsevier.
Russo, D., M Dassisti, V. Lawlor, & A.G. Olabi. (2012). State of the Art of biofuels from pure plant oil. Renewable and Sustainable Energy Reviews, 4056-4070.
Scarlat, N., & Dallemand, J.-F. (2010). Recent Developments of biofuels/bioenergy sustainability certificaiton: A global overview. Energy Policy, 1630-1646.
Scott, S. A., Davey, M. P., Dennis, J. S., Horst, I., Howe, C. J., Lea-Smith, D. J., & Smith, A. G. (2010). Biodiesel from algae: challenges and prospects. Current Opinion in Biotechnology, 277-286.
Zaimes, G. G., & Khanna, V. (2013, December). Environmental Sustainability of Emerging Algal Biofuels: A Comparative Life Cycle Evaluation of Algal Biodiesel and Renewable Diesel. Environmental Progress & Sustainable Energy, 32(4), 926-936.
TABLE OF FIGURES
Figure 1 Farming Algae www.energytrendsinsider.com................................................................0Figure 2 Green Algae numerocinqmagazine.com..........................................................................2Figure 3 Photobio Glass Tube Reactor...........................................................................................3Figure 4 Fermantation process of microalgae (Amin, 2009)..........................................................5Figure 5 Different Fermentation Processes based on Feedstock and Percent Yields (Lam & Lee, 2014)..............................................................................................................................................5Figure 6 Microalgal biomass recovered from the culture broth by filtration moves along a conveyor belt at Cyanotech Corporation (www.cyanotech.com), Hawaii, USA. Photograph by Terry Luke......................................................................................................................................6Figure 7 Microalgae biofuel production chain and examined production pathways (Zaimes & Khanna, 2013)................................................................................................................................7
