Produção de biocombustíveis a partir de resíduos e efluentes da indústria arrozeira: biodiesel e metano

Abstract

The unavoidable depletion of fossil fuels, the increase in the price of crude oil and the high emissions of greenhouse gases and pollutants make the search and improvement of techniques to produce clean and renewable energies an emergency. In this context, biofuels are included. Its sources of production present in the form of biomass from crops and agricultural waste, solid urban waste, effluents, among others. In view of the high potential for energy production from effluents and other waste from rice industries in Brazil, it is essential to study and develop biofuels from these by-products. Thus, this work aimed at the production of two biofuels, biodiesel and methane, which had as raw material the residues and effluents generated in rice processing processes. For this, were determined: 1) the best conditions for basic methyl transesterification of vegetable oil from rice bran for biodiesel production; 2) the potential for inhibition and enhancement of biodiesel glycerol to the Specific Methanogenic Activity (SMA) of the sludge from rice parboiling, and in what proportions such effects are present; 3) the potential for production of biodiesel and methane in the rice industries of the state of Rio Grande do Sul, as well as the potential for generating thermal and electrical energy from such biofuels. The study is complemented, therefore, on three fronts: experimental, energy planning and application of the generated energy. The results showed that in addition to being within the parameters required by ANP, ASTM and EN, the biodiesel produced with a 6:1 molar ratio of oil to alcohol, 1.0% catalyst and 120 minutes showed the highest yield obtained in this study, equal to 98.09%. Regarding methane production, the addition of 1% glycerol promoted the longest period of stationary phase for the sludge microorganisms, resulting in 539.45% of generation, superior to the system without glycerol, totalling a volume of 945.23±5.34 mL of methane produced in 168 hours of the experiment. Considering the energy potential raised in this study, Rio Grande do Sul (RS) has a production potential of 8.34E+02 m3.d-1 of rice bran vegetable oil biodiesel and an average potential to generate 8.44E+04 Nm3.d-1 of methane through the individual digestion of the effluent in the Rio Grande do Sul. With the addition of 1% crude glycerol in the process of anaerobic digestion of the rice parboiling effluent, RS had reached a potential to reach an average production of 4.55E+05 Nm3.d-1. Thus, analysis shows that 2.93E+06 kWh.d-1 of electric energy and 5.55E+06 kWh.d-1 of thermal energy can be generated in the state through the production and use of biodiesel and methane as energy sources.