|
Algae fuel or algal biofuel is an alternative to liquid fossil fuels that uses algae as its source of energy-rich oils. Several companies and government agencies are funding efforts to reduce capital and operating costs and make algae fuel production commercially viable. Like fossil fuel, algae fuel releases when burnt, but unlike fossil fuel, algae fuel and other biofuels only release recently removed from the atmosphere via photosynthesis as the algae or plant grew. The energy crisis and the world food crisis have ignited interest in algaculture (farming algae) for making biodiesel and other biofuels using land unsuitable for agriculture. Among algal fuels' attractive characteristics are that they can be grown with minimal impact on fresh water resources, can be produced using saline and wastewater, have a high flash point, and are biodegradable and relatively harmless to the environment if spilled. Algae cost more per unit mass than other second-generation biofuel crops due to high capital and operating costs, but are claimed to yield between 10 and 100 times more fuel per unit area. The United States Department of Energy estimates that if algae fuel replaced all the petroleum fuel in the United States, it would require , which is only 0.42% of the U.S. map, or about half of the land area of Maine. This is less than the area of corn harvested in the United States in 2000. According to the head of the Algal Biomass Organization, algae fuel can reach price parity with oil in 2018 if granted production tax credits. However, in 2013, Exxon Mobil Chairman and CEO Rex Tillerson said that after committing to spend up to $600 million over 10 years on development in a joint venture with J. Craig Venter’s Synthetic Genomics in 2009, Exxon pulled back after four years (and $100 million) when it realized that algae fuel is "probably further" than 25 years away from commercial viability.〔 On the other hand, Solazyme and Sapphire Energy already began commercial sales of algal biofuel in 2012 and 2013, respectively, and Algenol hopes to produce commercially in 2014. ==History== In 1942 Harder and Von Witsch were the first to propose that microalgae be grown as a source of lipids for food or fuel.〔Harder R., H. von Witsch. 1942. Bericht über versuche zur fettsynthese mittels autotropher microorganismen. Forschungsdienst Sonderheft 16:270–275.〕〔Harder R., H. von Witsch. 1942. Die massenkultur von diatomeen. Berichte der Deutschen Botanischen Gesellschaft 60:146–152.〕 Following World War II, research began in the US,〔Cook P.M. 1950. Large-scale culture of Chlorella. In: Brunel J., G.W. Prescott (eds) The culture of algae. Charles F. Kettering Foundation, Dayton, p. 53–77.〕〔Burlew J.S. (ed). 1953. Algae culture: from laboratory to pilot plant. Carnegie Institution of Washington, Washington, DC, p. 1–357.〕〔Burlew J.S. 1953. Current status of large-scale culture of algae. In: Burlew J.S. (ed). Algal culture: from laboratory to pilot plant. Carnegie Institution, Washington, DC, p. 3–23.〕 Germany,〔Gummert F., M.E. Meffert, and H. Stratmann. 1953. Nonsterile large-scale culture of Chlorella in greenhouse and open air. In: Burlew J.S. (ed). Algal culture: from laboratory to pilot plant. Carnegie Institution of Washington, Washington, DC, p. 166–176.〕 Japan,〔Mituya A., T. Nyunoya, and H. Tamiya. 1953. Pre-pilot-plant experiments on algal mass culture. In: Burlew J.S. (ed). Algal culture: from labo- ratory to pilot plant. Carnegie Institution, Washington, DC, p. 273–281.〕 England,〔Geoghegan M.J. 1953. Experiments with Chlorella at Jealott’s Hill. In: Burlew J.S. (ed). Algal culture: from laboratory to pilot plant. Carnegie Institution, Washington, DC, p. 182–189.〕 and Israel〔Evenari M., A.M. Mayer, and E. Gottesman. 1953. Experiments of culture of algae in Israel. In: Burlew J.S. (ed). Algal culture. From laboratory to pilot plant. Carnegie Institution, Washington, DC, p. 197–203.〕 on culturing techniques and engineering systems for growing microalgae on larger scales, particularly species in the genus ''Chlorella''. Meanwhile, H. G. Aach showed that ''Chlorella pyrenoidosa'' could be induced via nitrogen starvation to accumulate as much as 70% of its dry weight as lipids. Since the need for alternative transportation fuel had subsided after World War II, research at this time focused on culturing algae as a food source or, in some cases, for wastewater treatment. Interest in the application of algae for biofuels was rekindled during the oil embargo and oil price surges of the 1970s, leading the US Department of Energy to initiate the Aquatic Species Program in 1978. The Aquatic Species Program spent $25 million over 18 years with the goal of developing liquid transportation fuel from algae that would be price competitive with petroleum-derived fuels.〔Sheehan J., T. Dunahay, J. Benemann, P. Roessler. 1998. A look back at the U.S. Department of Energy’s Aquatic Species Program – biodiesel from algae. National Renewable Energy Laboratory: Golden, Colorado. NREL/TP-580-24190, p. 1–328.〕 The research program focused on the cultivation of microalgae in open outdoor ponds, systems which are low in cost but vulnerable to environmental disturbances like temperature swings and biological invasions. 3,000 algal strains were collected from around the country and screened for desirable properties such as high productivity, lipid content, and thermal tolerance, and the most promising strains were included in the SERI microalgae collection at the Solar Energy Research Institute (SERI) in Golden, Colorado and used for further research.〔 Among the program’s most significant findings were that rapid growth and high lipid production were "mutually exclusive," since the former required high nutrients and the latter required low nutrients.〔 The final report suggested that genetic engineering may be necessary to be able to overcome this and other natural limitations of algal strains, and that the ideal species might vary with place and season.〔 Although it was successfully demonstrated that large-scale production of algae for fuel in outdoor ponds was feasible, the program failed to do so at a cost that would be competitive with petroleum, especially as oil prices sank in the 1990s. Even in the best case scenario, it was estimated that unextracted algal oil would cost $59–186 per barrel,〔 while petroleum cost less than $20 per barrel in 1995.〔 Therefore, under budget pressure in 1996, the Aquatic Species Program was abandoned.〔 Other contributions to algal biofuels research have come indirectly from projects focusing on different applications of algal cultures. For example, in the 1990s Japan’s Research Institute of Innovative Technology for the Earth (RITE) implemented a research program with the goal of developing systems to fix using microalgae. Although the goal was not energy production, several studies produced by RITE demonstrated that algae could be grown using flue gas from power plants as a source, an important development for algal biofuel research. Other work focusing on harvesting hydrogen gas, methane, or ethanol from algae, as well as nutritional supplements and pharmaceutical compounds, has also helped inform research on biofuel production from algae.〔 Following the disbanding of the Aquatic Species Program in 1996, there was a relative lull in algal biofuel research. Still, various projects were funded in the US by the Department of Energy, Department of Defense, National Science Foundation, Department of Agriculture, National Laboratories, state funding, and private funding, as well as in other countries.〔 More recently, rising oil prices in the 2000s spurred a revival of interest in algal biofuels and US federal funding has increased,〔 numerous research projects are being funded in Australia, New Zealand, Europe, the Middle East, and other parts of the world,〔 and a wave of private companies has entered the field〔Darzins, A., 2008. Recent and current research & roadmapping activities: overview. National Algal Biofuels Technology Roadmap Workshop, University of Maryland.〕 (see Companies). In November 2012, Solazyme and Propel Fuels made the first retail sales of algae-derived fuel,〔 and in March 2013 Sapphire Energy began commercial sales of algal biofuel to Tesoro.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「algae fuel」の詳細全文を読む スポンサード リンク
|