Ethanol Production from Acetate: A Path to the Economically Viable Bioethanol

Published: December 05, 2011

r 2011 American Chemical Society 109 dx.doi.org/10.1021/es2040976 | Environ. Sci. Technol. 2012, 46, 109–109

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Ethanol Production from Acetate: A Path to the Economically ViableBioethanolAd~ao L. B. Montel*

Laborat�orio 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.

One of the big difficulties of using bioethanol as an effectivealternative for agricultural alcohol is economically obtaining

a viable source of bioethanol. Both current methods of producingbioethanol, reducing carbon dioxide or the enzymatic hydrolysisof cellulose or lignocellulose, are onerous. In this context, theacetate-to-ethanol reduction has shown to be a promising sourceof economically viable bioethanol. Many works consider thatobtaining ethanol from acetate would be excessively onerous dueto the cost of separating acetate present in wastewaters.1 There is,however, an abundant natural source of acetate that has beenneglected in this discussion: chitin. Acetate is abundantly presentin chitin, the second most abundant natural polymer in nature(by cellulose only). The obtention of acetate from chitin can takeplace in a simple way, through the alkaline or acidic hydrolysis ofthis polymer. In fact, the chitosan production industry annuallywastes large amounts of acetate through this process. Acetaterepresents about 29% of the molecular mass of chitin. It is esti-mated that the annual production of chitinous waste from theprocessing of marine invertebrates is between 1 and 100 billionmetric tons.2 If we consider the lower estimate (1 billion metrictons), the average percentage of acetate in chitin (=29%) andadmitting the conversion efficiency of acetate into ethanol (whichin some examples of these processes may reach=74.6%) we get asa result the possibility of producing almost 214 billion liters of

anhydrous ethanol through this path. This amountmight attend tothe rising American demand, that, according to estimates, will need136 billion liters of biofuel through 2022.3 Recent works havedemonstrated the viability of producing ethanol from acetate withthe use of mixtures of microorganism cultures and an electriccurrent, that is, through a bioelectrochemical reduction.4 Workslike this may open an important production line for ethanolbiofuel. The electricity needed for such processes may be obtainedfrom different sustainable sources: solar, wind, geothermal energy,etc. There are, clearly, problems with ethanol production throughthe bioelectrochemical reduction of acetate obtained from chitin.In the case of bioelectrochemical reduction, for instance, there areproblems associated with the low conversion rate and with the useof intermediates, which raise the costs and show some problemswith its stability.

Despite these problems, however, the conversion of acetate toethanol may be a viable alternative to help meet the risingdemand for ethanol, and it is important to get the industry’sattention to the research works in this field. The production ofacetate from chitin may be a path to economically viablebioethanol.

’AUTHOR INFORMATION

Corresponding Author*E-mail: montel@uft.edu.br.

’REFERENCES

(1) Agler,M. T.;Wrenn, B. A.; Zinder S. H.; Angenent L. T.Waste tobioproduct conversion with undefined mixed cultures: the carboxylateplatform. 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-statecultivation of Aspergillus sp. S1�13: Evaluation of a culture based onChitinase 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 andutilization 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 throughmediated acetate reduction bymixed cultures Environ. Sci. Technol. 2010,44 (1), 513�517; DOI: 10.1021/es902371e.

Received: November 16, 2011Accepted: November 21, 2011