Cost calculations for biogas from vinasse biodigestion and its energy utilization

The anaerobic biodigestion is as an alternative treatment for vinasse that preserve and even increase its fertilization potential (phosphorus, potassium and nitrogen content), dramatic reducing the BOD, making safer the use of treated vinasse for field fertirrigation. The process also yield methane, a very convenient and eco-friendly fuel gas, so the paper deals with a methodology for the calculation of the cost of the biogas, considering also the benefits of the fertirrigation using the liquid effluents from the digester, as well as the solids residues, very rich in organic matter. An analysis of the economical feasibility of the use of the biogas, obtained from the vinasse anaerobic digestion, as fuel, is also carried out. Different scenarios are evaluated, like: electric power generation through Reciprocating Combustion Engines (RCE), gas turbines and microturbines (MT), the cofiring of the biogas and bagasse in the mill’s boilers, the sale of the substituted bagasse, its utilization for electric power generation and the use of the biogas, as fuel, in spray drying of thermal sensible bioproducts (yeasts) to be commercialized. The possibility of selling the certificates of avoided greenhouse gasses emissions (carbon credits) due to the use of the biogas in substitution to fossil fuels, is also considered.