Development of a methodology for net energy analysis in biorefineries, regarding microalgae cultivation to improve energy yields in industrial wastes

Resumen

In general, biomass processing plants are considering the use of biorefinery concept to evaluate the net energy balance, as well as, the life cycle analysis of agroindustrial plants to meet sustainability requirements. Among the several types of biomass processing plants, biofuels production plants are becoming of great importance due to the increasing demand of biofuels to attend the desirable energetic sustainable global scenario. From the other side, energy recovering from wastes is an essential theme to achieve both, energy and environmental requirements. Inside this context, this paper considered the evaluation of energy recovering from vinasse of ethanol plants in Brazil to produce biogas or biodiesel through microalgae cultivation, once this kind of industrial plant produces a large amount of wastes. For such purpose, it was developed initially, a methodology to evaluate the net energy ratio in ethanol or biodiesel agroindustrial plants. Having this methodology in mind, it was considered the complementary energetic contribution of the biogas or biodiesel obtained from microalgae cultivation in vinasse and its processing. Based on this approach it was possible to evaluate the best options in terms of resources utilization, considering the analysis of the net energy ratio of ethanol agroindustrial plants. In conclusion, this type of analysis contributes to a better use of biomass resources, as well as, to the best design of the agroindustrial plant. Certainly, the energy recovered from the cultivation systems contributes to diminish the pressure on land use and consequently the competitiveness between food and energy.