Explosão a vapor como pré-tratamento de biomassas lignocelulósicas para produção de bioetanol

Abstract

Governments are currently building strategies to increasingly replace fossil fuel consumption by renewable and sustainable fuels. This occurs because oil reserves, the world's main energy source, are in imminent shortage, which can cause problems for environmental preservation. Thus, the use of biofuels, especially second-generation bioethanol (2G), is an alternative to alleviate this kind of problems. 2G ethanol is obtained from lignocellulosic biomass, which are promising raw materials available in large quantities and have low market value in Brazil. In this study, olive residues of the Arbequina variety were used for the tests. Olive groves provide a large amount of biomass, which can be obtained through pruning material or through olive oil extraction processes, generating solid and liquid residues, which must be treated or reused. In such case, in order to transform lignocellulosic materials (biomass) into bioethanol, five transformation steps are generally adopted, which consist of performing biomass pretreatment, cellulose and hemicelluloses hydrolysis, fermentation, ethanol separation and wastewater treatment. Pretreatment is one of the most expensive stages for bioethanol production and is still advancing on knowledge. It is a subject that needs to be properly studied. Therefore, this study aimed to use the steam explosion method for olive waste pretreatment as one of the steps for bioethanol production in order to evaluate which conditions of temperature, pressure, humidity and time can improve the subcritical hydrolysis process. In this research, in general, the steam explosion pretreatment did not increase the formation of reducing sugars, but some tests showed promising results. Therefore, a yield of 19.66 g/L of reducing sugars was obtained, indicating that values in this range may favor biofuel production. The extraction of olive oil with supercritical CO2 showed satisfactory results and consistent with the scientific literature, reaching yields of up to 2.83%.