Avaliação do óleo obtido do resíduo do pescado para obtenção de biocombustível

Abstract

Biodiesel is a biodegradable biofuel that can be obtained from transesterification of vegetable oils or animal fats, such as fish oil. The disposal of this residue in the environment generates gases with bad odors, leaching of organic material, waterproofing of the soil and eutrophication in water bodies. The use of these wastes to produce biodiesel is a sustainable alternative. The objective of this study was to characterize the oil extracted from fish waste for the production of biofuel. The oil was extracted from the residue (head and carcass with viscera) by cooking in two treatments: 60 ° C / 120 minutes (T1) and 80 ° C / 90 minutes (T2), observing its physicochemical characteristics and the highest oil yield . The fatty acid profile of the oils obtained in T1 and T2, was determined by gas chromatography with flame ionization detector. The methods of conventional transesterification (heating and shaking) were evaluated at the 30 and 60 minute reaction times, and assisted by ultrasonic waves at times of 1, 2 and 3 minutes, under the ultrasonic frequencies of 20kHz and 40kHz. The conversion of the oil to biofuel occurred with the aid of methyl alcohol and sodium hydroxide as catalyst, observing the yield. The chemical composition of the oil obtained from the residue and the biofuel obtained in the two techniques was investigated by infrared spectroscopy. The acid index and the peroxide index of biofuels were determined. The results of the extractions showed that Treatment 2 was the one with the best oil yield and had a specific mass of 0.921 ± 0.01g/cm 3 . The acid, iodine, peroxide and saponification indices of the oil are in agreement with the literature. Determining the moisture content of the residue confirms its lean composition. The moisture of the oil is above the ideal limit to obtain a good yield in biodiesel in the transesterification. The fatty acid profile of the oil presented the palmitic, palmitoleic and oleic fatty acids as the ones with the highest percentages in area. The conventional method was the best yield in biodiesel (97.95 ± 0.69%) with 60 minutes of reaction, presenting a specific mass of 0.895 ± 0.00g / cm3 . The ultrasonic method obtained higher yields (81.02 ± 59%) with 2 minutes sonication at the 20 kHz frequency. The acid and peroxide indices determined in biofuels are below the limit determined by the National Petroleum Agency (ANP). Infrared spectroscopy identified the ester and carbonyl functional groups, which are part of the composition of the oils and confirmed the conversion of the residual oil to biodiesel. The biodiesel obtained in the two techniques presented high concentrations of sodium, potassium and magnesium from the fish residue, salting and sodium hydroxide used to catalyze the reaction. However, obtaining a biofuel from waste with an inadequate final destination, supports this project. The generation of a value-added product under these conditions encourages improvements in the economic, social and environmental aspects of a region.