A viscous, yellow liquid with an unpleasant odor, fusel oil is the least-known waste produced by the sugar and alcohol industry. Every thousand liters of ethanol generates, on average, 2.5 liters of fusel. The compound consists of various alcohols, and only a small fraction of the approximately 80 million liters produced in Brazil each year is used to manufacture a type of alcohol called isoamyl alcohol. Part is burned to generate energy for the plants. Factories, however, do not disclose how much is transformed into isoamyl alcohol, how much is burned, and how much is discarded. With the objective of making better use of this waste product, two research groups are studying fusel oil in order to transform it into a product with greater value. In one of the groups, at the School of Science and Technology of São Paulo State University (FCT-UNESP), Presidente Prudente campus, Professor Eduardo René Pérez González is coordinating a project that proposes recycling fusel oil and carbon dioxide (CO2) — one of the greenhouse gases, also generated in the plants — in a single process.
In a study published in the journal RSC Advances of the Royal Society of Chemistry, the group from UNESP indicated that processing the two waste products could lead to the production of alkyl carbonates for use as additives in fuel, drugs and fungicides. “Our goal is to add value to these wastes by combining them to form chemical compounds with various potential or known uses,” explains González. “In more developed countries, researchers are very interested in finding a solution for CO2. Here we have found one on a laboratory scale. The main substances obtained are alkyl carbonates, which in principle can be considered intermediate agents in the organic synthesis of other chemicals.” This means that they can be used to produce chemicals such as carbamates, potential fungicides to protect sugarcane or other crops.
Doctoral student Fernanda Stuani, González’s student in the Fine Organic Chemistry Laboratory (LQOF) at FCT-Unesp, explains that two processes were tested during the experiments. “In the first, we distilled the fusel oil to extract the isoamyl alcohols, which are used to produce alkyl carbonates. Since it would be difficult to make this process economically feasible, because the factories would have to first distill the oil in order to produce the carbonate, we also attempted, in a second process, to do this directly using fusel oil.” The experiments used carbon dioxide purchased commercially, but the idea is to take advantage of that generated in the plants during ethanol production. “Later, working with chemical and environmental engineers, we will try to do a study to implement this technology on a larger scale,” adds González.
Information and disposal
The other group studying the use of fusel oil is coordinated by Eduardo Augusto Caldas Batista, a professor at the University of Campinas School of Food Engineering (FEA-Unicamp). These projects intend to obtain isoamyl alcohol using more advanced technologies—the product has applications in the paint, plastics, perfume and food sectors. According to Batista, one of the difficulties when carrying out this research is the scarcity of information available on the use of fusel oil. “Since there is not a well-established market for this waste product, finding information on its price, use and discard practices is difficult,” he says. According to the researcher, the waste product can be added to fuel ethanol. But it is not known what the sugar and alcohol industry actually does with it, nor how it is discarded. “Since it is highly toxic, this waste cannot be released into the environment without treatment.”
In Batista’s work, he proposes studying the configurations of a process to produce isoamyl alcohol using waste oil, integrated into the ethanol production process. “The configurations can be coupled with conventional ethanol production, or used in independent systems,” he says. “This line of research began in 2010 and continued in 2012 with the PhD proposal of a student named Magno José de Oliveira,” recounts Batista. During the study, three process configurations were developed to recover isoamyl alcohol, which is an ingredient of fusel oil. The study resulted in a 2013 article in the journal Industrial and Engineering Chemistry Research. Oliveira’s project proposes two process configurations: one integrated into a hydrous ethanol production plant and another that, in addition to obtaining isoamyl alcohol from the oil, also recovers butanol and ethanol from the waste. “We have applied for patents with the Brazilian Industrial Property Institute (INPI) for both processes,” says Batista.
Professor Antonio Aprigio da Silva Curvelo of the University of São Paulo (USP) São Carlos Institute of Chemistry says that recovering and using carbon dioxide has been studied for years. “With respect to the use of fusel oil, it has not yet been shown to be important from an industrial standpoint, though some applications could be found for it,” says Curvelo. According to him, the greatest merit of the work is the academic contribution to finding an alternative for the use of these raw materials and the explanation of the mechanisms involved in the reactions studied.
1. Study of reactions of clean synthesis and chemical modification of biodiesel and fusel oil for preparation of organic carbonate and carbamates using carbon dioxide in the presence of organocatalysts and heterogeneous catalysts (nº 2013/24487-6); Grant Mechanism Regular research project; Principal Investigator Eduardo René Pérez González (FCT-Unesp); Investment R$ 106,024.75 and US$ 58,568.54.
2. Phase equilibrium and purification processes in the production of biofuels and biocompounds (nº 2008/56258-8); Grant Mechanism Regular, Bioen program — Pronex Thematic Project; Principal Investigator Antônio José de Almeida Meirelles (FEA-Unicamp); Investment R$ 1,307,138.81 and US$ 629,087.74.
PEREIRA, F. S. et al. Cycling of waste fusel oils from sugar cane industries using supercritical carbon dioxide. RSC Advances. V. 5, No. 99, p. 81515-22. 2015.
FERREIRA, M. C. et al. Study of the fusel oil distillation process. Industrial and Engineering Chemistry Research. V. 52, No. 6, p. 2336-51. 2013.