Fuel The World
3rd
Third generation biofuel is made from microalgae. Microalgae, one of the oldest living organisms on earth, is a small unicellular organism that has no leaves, roots and stems. Its simple cellular structure makes it more efficient at converting solar energy than other higher plants.
Third Generation Biofuel
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Microalgae as biomass have several advantages. Because of its rapid growth rate, ability to double its number in 24 hours, and high production of lipids, some with the oil content of over 80 percent, microalgae can produce 15-300 times more fuel than other traditional crops on an area basis. Fuel extract from algae can potentially replace all U.S. oil consumption using only 15000 square miles of production compare to the current 35,000 square miles of production of corn used meeting only 10 percent of U.S. fuel needs. Microalgae can convert higher fraction of their biomass to oil than all current conventional energy crop. For example, microalgae have an average of 60% oil recovery compare to the 3% of soybeans. The per unit area yield of oil from algae is around 58,700 to 136,900 L/ha/year which is 10 to 23 times higher than the next highest yielding crop, oil palm, at 5,950 L/ha/year. The U.S. Department of Energy’s Aquatic Species Program established in 1978 to 1996 researched on biodiesel from microalgae and suggested that biodiesel from microalgae is the only viable method to produce enough fuel to replace world fuel usage.
In addition, microalgae requires low maintenance and do not compete with land for food production as it can be grown on non-arable land such as marine environments and desert(with seawater pond) and can use waste water as source of nutrients. Microalgae production can be combined with waste water treatment to produce clean water and remove significant quantity of organic compounds as well as heavy metal
contaminants. The microalgae production process also allows the recovery of phosphorus, essential but scarce element in nature, from waste. The microalgae is also great at absorbing CO2 sometimes taking in more than 90 percent of CO2 when the gas is piped through the algae pond. The fuel produced from microalgae has a greater diversity, is indistinguishable from current fossil fuel and requires less processing. Microalgae can be turn into different products including hydrogen, biodiesel, butanol, gasoline, methane, ethanol, bio oil, and syngas depending on the type of conversion used (transesterification, fermentation, gasification, pyrolysis and many others).
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How is microalgae grown?
There are two main systems for growing microalgae, open and closed system. Open-air system use lake, natural ponds, or artificial ponds for algae biomass production. This system has mostly being use to cultivate algae with especially high oil content. This system is less expensive to build and to operate, has a greater production capacity, and can use waste water for nutrients making it more commercializable than closed system. However open system face technical challenge in the uncontrollable water temperature, light intensity, competition from invasive algae and bacteria, and evaporation. The open systems using monoculture are also vulnerable to infection. One common type of open air system is the open pond raceway system. The raceway pond is open, shallow pond made up of zig zagging oval shape channels that looks like a raceway for cars to minimize space. The raceway is typically made with poured concrete or artificial hole in the ground( usually lined with material that prevent the ground from soaking water away. It operates in a continuous mode, the paddle wheel in the beginning of the circulation to provides circulation and nutrients for algae and the algal broth in the end of the circulation that harvest the algae.
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(28) High surface area to volume ratio of the closed system maximized algae's exposion to sunlight.
In contrast, closed system, also known as photobioreactors, allows controls of light distribution, temperature, nutrients, and many other factors to meet the growing condition needed of a specific type of algae but have high building and operation cost. Photobioreactors is a system that utilize sight source to cultivate phototrophic organism. Some pump nutrient rich water through transparent tubes that are exposed to sunlight. The close system generally has a greater surface area to volume ratio to maximize the sunshine the algae get. In vertical closed loop production, microalgae are placed in clear plastic bags and expose to sunlight on both side. The increase in sunlight consumption increases the oil production. However the problem in finding sterile carbon dioxide source and lack of equipment inhibit this method to be commercialized.
In addition to the open and close system there are also algae turf scrubber and biofilm system. The Algae Turf Scrubber is a system design for cleaning nutrients and pollutants in water with algal turfs. The system mimics natural algal turfs and allow naturally occurring algae spores to coloneze the surface. The algae can be harvested every 5-15 days but as the algae in the system is naturally occurred polyculture, the ATS has lower lipid content and is more suitable to be fermented into alcohol. This system generally has a higher productivity than other open systems, lower operation cost, and eliminate contamination. The biofilm system induce algae to attach to and colonize the water surface with controlled concentration of cations, proteins, and organic molecules on the surface. The biofilm system was already used in wastewater treatment plants so algae biofilm system can integrate the waste water treatment for nutrient supply and in return provide treated water. Compare to the usual suspended culture, biofilm system can increase culture density to reduce water and land usage and can improving production in harvesting, dehydrating operation.Scientists also hope to improve both the quality and quantity of fuel from microalgae through genetic engineering.
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(29) The algae production can be set up in nonarable land and combined with factories that release exausted gas for source of carbon dioxide
How is microalgae made into fuel?
The wet algae have to go through several different steps to be processed into fuel and the type of process depends on the fuel desired. The energy rich compounds are first extracted from algae as "green crude" that can later turn into specific fuel through different processes. There are different ways to extract oil from algae including chemical, mechanical and combination of both. Oil press, similar to olive press, is a one of the simplest and most popular method to extract oil from algae. It can extract up to 75 percent of the oil from algae. Another method, the ultrasonic method, uses ultrasonic waves to create bubbles in a solvent. The bubbles will then burst and break the cell walls of the algae causing oil to be released into the solvent. The hexane solvent method first press out the oil then mixes the leftover algae with hexane to extract further. This two step process together can extract up to 95 percent of oil from algae.
The green waste leftover can be turn into valuable byproducts such as natural dyes and pigments, antioxidant, and animal feed. It can also be fermented into butanol and other solvents.
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(30) Extract fat and sugar from algae through chemical method with solvents.
(31) The oil press machine
© 2015 by Van Hsieh
Sponsored by Mrs. Moriarty and Davis Senior High