Luís, km 235, 13565-905 São Carlos -SP, Brasil Recebido em 8/12/11; aceito em 9/8/12; publicado na web em 28/11/12 EVALUATION OF THE POTENTIALITY OF FRESHWATER MICROALGAE AS A SOURCE OF RAW MATERIAL FOR BIODIESEL PRODUCTION. In this work, the fatty acid quantity and composition of six freshwater microalgae and soybean grains was determined by direct transesterification and gas chromatography analysis. The results showed that all the freshwater microalgae species presented a higher quantity of fatty acid than soybean grain. Choricystis sp. (A) provides 115% more fatty acids per gram of biomass than soybean grain. With regard to the fatty acid composition, Choricystis sp. (A) showed an adequate proportion of saturated and unsaturated fatty acids, with lower quantity of polyunsaturated fatty acids and, akin to some marine microalgae, constitutes an alternative raw material for biodiesel production.Keywords: microalgae; transesterification; biodiesel. INTRODUÇÃOAtualmente, o Brasil se destaca por gerar 45% de sua matriz energética a partir de fontes renováveis de energia, com destaque para a produção de biocombustíveis. Entre os biocombustíveis mais promissores destaca-se o biodiesel, o qual no mundo é produzido basicamente utilizando óleos como os de soja, canola e palma.1 No caso do Brasil, a produção de biodiesel a partir da soja representa, aproximadamente, 80 a 90% da totalidade da matéria-prima graxa empregada para tal finalidade. 2A soja, contudo, apresenta pouco teor de óleo no grão e baixa produtividade por hectare, além de ser uma commodity agrícola. Essas características indicam que o aumento da produção de biodiesel no mundo tendo como base esta oleaginosa pode acarretar sérios danos econômicos e ambientais, especialmente se sua produção em larga escala for acompanhada do aumento da área cultivada, com expansão da fronteira agrícola e da ocupação humana via novos desmatamentos, com consequente perda de biodiversidade. 2Nesse sentido, é essencial pesquisar fontes de matérias-primas alternativas para a produção de biodiesel e, nesse contexto, destaca--se o potencial das microalgas. Um dos mais importantes apelos para produção de biodiesel a partir de microalgas é que este tipo de cultivo não deslocará as tradicionais áreas de cultivo voltadas para a alimentação humana -uma das principais críticas à produção de biodiesel a partir de plantas oleaginosas. 3Assim como as oleaginosas, muitas microalgas são ricas em triacilglicerídeos, os quais podem ser convertidos em ésteres metílicos de ácidos graxos (FAME -fatty acids methyl esters) para produção de biodiesel. Adiciona-se ainda o fato de que estudos demonstram que a composição química de ácidos graxos presentes em algumas microalgas é similar às oleaginosas atualmente utilizadas para a produção de biodiesel, tais como soja e canola. 4,5 Atualmente o processo utilizado para a produção de biodiesel a partir de microalgas é a transesterificação do óleo extraído via catálise ácida ou básica na presença de um álcool. Na literatura são descritos vários process...
In view of the constant search for new sources of renewable energy, the particulate agro-industrial waste reuse emerges as an advantageous alternative. However, despite the advantages of using the biomass as an energy source, there is still strong resistance as the large-scale replacement of petroleum products due to the lack of scientifically proven efficient conversion technologies. In this context, the pyrolysis is presented as one of the most widely used thermal decomposition processes. The knowledge of aspects of chemical kinetics, thermodynamics these will, heat and mass transfer, are so important, since influence the quality of the product. This paper presents a kinetic study of slow pyrolysis of coffee grounds waste from dynamic thermogravimetric experiments (TG), using different powder catalysts. The primary thermal decomposition was described by the one-step reaction model, which considers a single global reaction. The kinetic parameters were estimated using nonlinear regression and the differential evolution method. The coffee ground waste was dried at 105°C for 24 hours. The sample in nature was analyzed at different heating rates, being 10, 15, 20, 30 and 50 K/min. In the catalytic pyrolysis, about 5% (w/w) of catalyst were added to the sample, at a heating rate of 30 K/min. The results show that the one-step model does not accurately represent the data of weight loss (TG) and its derivative (DTG), but can do an estimative of the activation energy reaction, and can show the differences caused by the catalysts. Although no one can say anything about the products formed with the addition of the catalyst, it would be necessary to micro-pyrolysis analysis, we can say the influence of the catalyst in the samples, based on the data obtained in thermogravimetric tests.
Locally available malt waste or brewers' spent grain, a by-product of brewing industry, was found to be a low cost and promising biomass for pyrolysis. A kinetic studied of pyrolysis of malt waste was investigated by non-isothermal thermogravimetric analyses (TG-DTG), applying slow heating rates, 10, 15, 30 and 50 K/min, and well-defined conditions. Activation energies and Arrhenius exponential factors were inferred by different estimation methods: Kissinger, Ozawa, Starink, K-A-S and. The methods presented energy activation values of 214 - 238.23 kJ/mol. The Literature studies found activations energies values similar to those found for sugarcane bagasse pyrolysis and other types of biomasses with predominance of hemicelluloses, cellulose and lignin, respectively.
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