Abstract. Large consumption of non-renewable fuels in the world has strongly encouraged the search for biofuels, due to inevitable shortage of fossil energy sources and catastrophic problems generated by their use. Under these circumstances the so called second generation biofuel production has been highlighted, where lignocellulosic materials such as sugarcane bagasse are used to produce bioethanol, unlike the traditional first-generation process, whose feedstock is sugarcane. Therefore, this work aimed to perform a comparative exergetic analysis between first and second-generation bioethanol production processes, in order to evaluate from the exergetic point of view, which of these processes is the most feasible. It was found an overall exergetic efficiency of 60.89 % for the exclusively first-generation plant, whereas for the integrated plant, it was obtained 41.58 %. In this way, insertion of new stages in production process, required by the second generation, has caused consequently an increase of irreversibilities and losses.

Abstract. Biofuels, such as biodiesel has obtained more and more relevance in the national scenario, because of the current concerns related to the burning of fossil fuels, besides of laws in force that determine the increase of biodiesel blend in common diesel each year. Thus, in this study a comparative exergetic analysis was carried out between the biodiesel production from soybean oil via basic homogeneous catalysis, case 1, where sodium hydroxide (NaOH) was used as a catalyst, and by means of supercritical alcohol, case 2, in which methanol was led to critical state. For that, two production plants were simulated in Aspen HYSYS ® V9 software accepting the same amount of main feedstock, in this case soybean oil. After the simulations, the exergetic efficiency of each process was calculated through to a global control volume (CV), having as result 94.01 and 93.50 % to the Case 1 and 2, respectively. These results confirm the feasibility of biodiesel production and the little exergetic difference was caused principally by the conditions of temperature and pressure that were imposed in the methanol supercritical case.

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