National potential production of methane and electrical energy from sugarcane vinasse in Brazil: A thermo-economic analysis

The sugarcane is the most explored raw material in Brazil to produce ethanol and for each liter of ethanol around 12 L vinasse are produced, thus, the country has high production of vinasse. The vinasse has a very high polluting potential, being considered a solid residue. In general, the vinasse is applied in sugarcane plantations, in some cases with wastewater from plants, promoting the fertirrigation. Therefore, the objective of this work was to evaluate the potential of methane generation from the vinasse generated in Brazilian ethanol plants, as well as its potential for thermal and electrical energy generation and economic viability. In all, 377 ethanol plants are registered in Brazil, where 334 are of the annexed type and only 43 autonomous. The results indicate that Brazil has the potential to generate at least 3.53E + 07 m.d^-1 of methane, 1.88E + 06 m.d^-1 in autonomous plants and 3.34E + 07 m.d^-1 in annexed plants. While all the autonomous plants have a minimum production potential of 1.21E + 07 kWh.d^-1 of electrical energy and 2.28E + 07 kWh.d-1 of thermal energy, that of annexed plants reach a potential of 2.15E + 08 kWh.d^-1 of electrical energy and 4.07E + 08 kWh.d^-1 of thermal energy. The costs of producing electricity from methane were about 0.09 R$.kWh^-1 for autonomous plants and about 0.06 R$.kWh-1 for annexed plants. NPV has a positive value in all cases indicates that this study, Autonomous plants presented IRR of 51% with a payback of one year and 11,51 months, while the annexed obtained 161% of IRR and payback of 7,56 months.