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Ethanol Production from Acetate: A Path to the Economically Viable Bioethanol Ad~ao L. B. Montel* Laboratorio de Química, sala 02, Bloco II, Departamento de Engenharia Civil, Universidade Federal do Tocantins, Av. NS 15, ALCNO 14, 109 Norte, Palmas, Tocantins, Postal Code 77001-090. anhydrous ethanol through this path. This amount might attend to the rising American demand, that, according to estimates, will need 136 billion liters of biofuel through 2022.3 Recent works have demonstrated the viability of producing ethanol from acetate with the use of mixtures of microorganism cultures and an electric current, that is, through a bioelectrochemical reduction.4 Works like this may open an important production line for ethanol biofuel. The electricity needed for such processes may be obtained from different sustainable sources: solar, wind, geothermal energy, etc. There are, clearly, problems with ethanol production through the bioelectrochemical reduction of acetate obtained from chitin. In the case of bioelectrochemical reduction, for instance, there are problems associated with the low conversion rate and with the use of intermediates, which raise the costs and show some problems with its stability. Despite these problems, however, the conversion of acetate to ethanol may be a viable alternative to help meet the rising demand for ethanol, and it is important to get the industry’s attention to the research works in this field. The production of acetate from chitin may be a path to economically viable bioethanol.
’ AUTHOR INFORMATION Corresponding Author
O
ne of the big difficulties of using bioethanol as an effective alternative for agricultural alcohol is economically obtaining a viable source of bioethanol. Both current methods of producing bioethanol, reducing carbon dioxide or the enzymatic hydrolysis of cellulose or lignocellulose, are onerous. In this context, the acetate-to-ethanol reduction has shown to be a promising source of economically viable bioethanol. Many works consider that obtaining ethanol from acetate would be excessively onerous due to the cost of separating acetate present in wastewaters.1 There is, however, an abundant natural source of acetate that has been neglected in this discussion: chitin. Acetate is abundantly present in chitin, the second most abundant natural polymer in nature (by cellulose only). The obtention of acetate from chitin can take place in a simple way, through the alkaline or acidic hydrolysis of this polymer. In fact, the chitosan production industry annually wastes large amounts of acetate through this process. Acetate represents about 29% of the molecular mass of chitin. It is estimated that the annual production of chitinous waste from the processing of marine invertebrates is between 1 and 100 billion metric tons.2 If we consider the lower estimate (1 billion metric tons), the average percentage of acetate in chitin (=29%) and admitting the conversion efficiency of acetate into ethanol (which in some examples of these processes may reach =74.6%) we get as a result the possibility of producing almost 214 billion liters of r 2011 American Chemical Society
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’ REFERENCES (1) Agler, M. T.; Wrenn, B. A.; Zinder S. H.; Angenent L. T. Waste to bioproduct conversion with undefined mixed cultures: the carboxylate platform. Trends Biotechnol. 2011, 29 (2), 70 78; DOI: 10.1016/ j.tibtech.2010.11.006. (2) Rattanakit, N.; Plikomol, A.; Yano, S.; Wakayama, M.; Tachiki, T.; Utilization of shrimp shellfish waste as a substrate for solid-state cultivation of Aspergillus sp. S1 13: Evaluation of a culture based on Chitinase formation which is 3necessary for chitin-assimilation. J. Biosci. Bioeng. 2002, 93, 550 556; DOI: 10.1263/jbb.93.550. (3) Balat, M.; Balat, H. Recent trends in global production and utilization of bio-ethanol fuel. Appl. Energ. 2009, 86 (11), 2273 2282; DOI: 10.1016/j.apenergy.2009.03.015. (4) Steinbusch, K. J. J.; Hamelers, H. V. M.; Schaap, J. D.; Kampman, C.; Buisman, C.J. N. Bioelectrochemical ethanol production through mediated acetate reduction by mixed cultures Environ. Sci. Technol. 2010, 44 (1), 513 517; DOI: 10.1021/es902371e. Received: November 16, 2011 Accepted: November 21, 2011 Published: December 05, 2011 109
dx.doi.org/10.1021/es2040976 | Environ. Sci. Technol. 2012, 46, 109–109
